USE IN SILICON MANUFACTURINGSilicon Wafer Cleaning Wafer cleaning is the largest use of ultrapure...

USE IN SILICON WAFER

MANUFACTURING This article reports t ions must be the results achieved treated before dis- and lessons learned charge Water sup- from five years of ply and wastewater

treatment are basic industrial infra-

successful water reuse efforts a t t he

MEMC Electronic structure needs pro- Materials Inc vided e i ther by manufacturing fa- public systems or cility in Spartanburg South Carolina MEMC by private utilities developed by the industrial achieved water cost savings and significantly in- water user creased total water use without increasing wa- The semiconductor or microelectronic in- ter supply demand or expanding wastewater dustry uses large volumes of ultrapure water treatment facilities Water reuse practices a t This ultrapure water is highly filtered and dem- other manufacturing facilities operated by ineralized and contains no particles dissolved MEMC also are presented The case study results salts or organic contaminants As the industry and water balance techniques illustrated are of and semiconductor technology evolved during interest to the semiconductor industry and to the 1970s and 1980s water use efficiency was other industries that use large volumes of not a high priority The focus of manufacturing ultrapure water technology and equipment design was smaller

A case study in wafer reuse at

MEMC

Water Conservation and Reuse Many industrial operations require large vol-

umes of high quality water These operations compete with other water users for water sup-

Paul S Dickens and

Alan E Madewell plies Wastewaters generated by industrial opera-

C 2000 John Wiley R Sons Inc

Pollution hevention Review

microelectronic device size faster processing speed and improved manufacturing yield The cost of producing ultrapure water and treating resulting wastewaters was not considered a significant cost of production or an opportunity for improvement

This situation has changed The semiconductor industry matured during the 1990s and faces extreme pressure on pricing margin and manufacturing cost At the same time the industry has realized its dependence upon reliable water supplies and affordable water and wastewater utilities These infrastructure needs limit the location

and expansion of semiconductor manufactur-

Water consumption can be reduced ing facil i t ies The in two ways water conservation and efficiency of semicon-

ductor water use has water reuse

new a t ten t ion rsquo The National Technology Roadmap of the Semicon- ductor Industry Association includes definitive goals and time frames to reduce water consumption in microelectronic manufacturing Semicon- ductor equipment manufacturers and silicon material suppliers share these goals

Water consumption can be reduced in two ways water conservation and water reuse Other authors3 have discussed the benefits of and tech- nologies for water conservation and reuse in public water systems and municipal wastewater utilities Water reuse practices and opportunities in industry are product- and process-~pecific~ rsquo For industry water conservation involves new or modified process technology and equipment that use less water per unit of production in a particular process step Water reuse in industry involves one or more of the following practices

Wastewater effluent reuse is capture of treated wastewater effluent for secondary uses such as agriculture horticulture flush water or industrial cooling This practice has the effect of off-

setting water supply demand for the secondary use Wastewater effluent reuse for landscape ir- rigation and industrial cooling are common practices Strict criteria for public health protection apply where direct human contact with wastewater effluents can occur In-process water reuse involves multiple uses of water in a production step or piece of manufacturing equipment A common example is countercurrent rinsing used in elec- troplating and metal cleaning operations Relatively ldquocleanrdquo water from final rinse tanks flows opposite (or countercurrent) to product flow The final rinse water is recovered and supplied to ldquodirtyrdquo rinse tanks at the start of the cleaning line In-process water reuse is possible where water quality is not critical to product quality in upstream process steps In- process water reuse reduces water supply demand for production and associated wastewater flow Implant water reuse is the capture or recovery of rinse water and other ldquocleanrdquo process wastewaters for use in plant utility systems such as cooling towers air pollution scrubbers and wastewater treatment that do not require high quality water It has the effect of offsetting water supply demand and wastewater flow associated with utility systems In- plant water reuse requires facilities for collect- ing storing and distributing reuse water Par- tial treatment of recovered water may be required before reuse Process water recyclingis the capture or recovery of process wastewaters followed by treatment and return to the production process This is possible only where water quality after treatment is acceptable for product quality Process water recycling is practiced in industries where water supplies are limited or the production process can tolerate low-quality water Treatment steps and equipment for

lsquo

22 Spring 2000 I Pollution Prevention Review I Paul S Dickens and Alan E Madewell

process water recycling can be capital inten- sive and expensive to operate A form of process water recycling practiced in the semiconductor industry involves returning silicon wafer cleaning rinse water to ultrapure water p r o d u ~ t i o n ~

Water conservation is primarily an issue of tool design and process development (The term tool refers here to semiconductor manufacturing equipment) In some cases new technology is needed for a significant improvement in process water consumption12~o Water reuse and process water recycling are primarily issues of facility design and operation

MEMC Electronic Materials Inc MEMC Electronic Materials Inc manufactures

polished and epitaxial silicon wafers Silicon wafers are the substrate or base on which microelectronic circuits (microchips) are built MEMC is a worldwide producer of silicon with manufacturing plants in the United States Europe and Asia MEMCs customers are the manufacturers of logic and memory microchips used in everything from computers and consumer electronics to automo- biles and aerospace

MEMCs production processes fall into two general categories crystal growth and wafering Crys- tal growth refers to process steps for converting polycrystalline silicon into single crystal silicon ingots (also called silicon rods) The crystal growth process is carefully controlled to produce silicon rods meeting different electrochemical properties specified by MEMC customers Wafering refers to process steps for converting silicon rods into wafers and preparing the wafer surface for microchip manufacturing by MEMC customers The final polished silicon wafers must meet exacting standards for flatness chemical purity and surface cleanli- ness Epitavialgrowth is a value-added process where a thin layer of ultra-pure silicon is deposited on

the surface of a polished silicon wafer MEMC also produces polycrystalline silicon the raw material for silicon crystal growth and wafering

Water Use at MEMC Uses of water by MEMC include

Ultrapure water production Process water production Cooling tower makeup Makeup to wet scrubbers for air pollution control Flush water for sewers Flush and supply water for wastewater treatment and other utility systems

The greatest single water use is ultrapure water production MEMC uses ultrapure water (UPW) for silicon wafer cleaning and Other wet process steps The ultrapure water is necessary to prevent particle organic and metallic contamination of the silicon wafer surface UPW is produced from groundwater or purchased water with the following general steps

MEMCs production processes fall into two general categories crystal

growth and wafering

sand filtration and carbon adsorption single- or multi-stage reverse osmosis (RO) demineralization (deionization) in either ion ex- change or electrochemical (EDI) demineralizers microfiltration sterilization

The term purchased water refers to water purchased from public water supplies

Depending upon production technology and the degree of demineralization between 12 and 145 gallons of feed water are required for each gallon of ultrapure water Feed water losses include filter backwash reverse osmosis reject ED1 and microfilter

Offsetting Water Use in Silicon Wafer Manufacturing Pollution Prevention Review I Spring 2000 I 23

bleeds and rinse water from demineralizer regen- eration MEXIC produces two resistivity grades of ultrapure water 3-10 megohm deionized (DI) n a -

ter and 18 megohm DI waterI The 18 megohm DI water involves the larger volume

The second largest use of water by MEMC is for process cooling and space conditioning Silicon crystal growth is a high-temperature process and requires cooling water for process control Several silicon wafering steps are also thermal processes and require cooling The majority of silicon wafering takes place in a clean room environment with tight temperature and humidity controls Each MEMC manufacturing facility includes cooling towers mechanical chillers and chilled water systems to remove process heat and to maintain clean room environments Excess process heat latent heat from manufacturing equipment and personnel and heat from mechanical chillers are removed in cooling towers by evaporation

MEMC examined its costs for water use and associated wastewater treatment at nine manufacturing facilities worldwide In 1998 the combined cost of purchased water ultrapure water produc-

tion and cvastewater treatment was 30 percent of the cost of goods sold (COGS) When depreciation of capital facilities for ultrapure water and wastewater treatment is included the 1998 cost of water use by MEMC was 54 percent of COGS Water use efficiency thus represented an important cost reduction opportunity for MEMC

Silicon Wafer Cleaning Wafer cleaning is the largest use of ultrapure

water in silicon wafer manufacturing Prior to thermal process steps in wafering and epitaxial growth and prior to final packaging and shipment to customers the surface of silicon wafers must be cleaned to remove particles organic contaminants ionic contaminants and trace metals

The cleaning process is performed in a wet bench cleaner The wet bench contains a series of chemical solutions designed to remove the contaminants of concern Each chemical bath is followed by one or more rinse baths using DI water Wet bench cleaning technology is based on the RCA Cleaning Pro- cessi2 developed in the 1970s A typical wet bench cleaner for silicon wafers is illustrated in Exhibit 1

Exhibit 1 Typical SCllSC2 Wet Bench for Silicon Wafer Cleaning Drains Configured for Rinse Water Recovery and Reuse

EXHAUST TO PROCESS FUME SCRJBBER

4 DIRECTKIN OF SILICON WAFER FLOW

1 ROBOTIC OR WALKING B E N CARRIER 1

1 WET LOAD

I DI WATER OVERFLOW TO PLENUM

I BITH

1 LOAD PLENUM

L

QUICK DUMP RINSE 1

O4WATTER OVERFLOW 10 PLENUM

-1 L + TO P R 0 CESS 1 DRAIN I

I - j

d

EXHAUST TO ACID FUME SCRUBBER

t I

WET BENCH DECU ~- -7 - scz BATH I QUICKDUNP 1 WETUNLOM OVERFLOW I

I ]RINSE 1 BATH

_____ Y- ___ RECOVERY WATER DRAIN I _ _ A -

24 I Spring 2000 I Pollution Prevention Review Paul S Dtckens and Alan E Madewell

The wet bench tool is usually enclosed and operated inside a clean room environment The wet bench tanks and cabinet are constructed of high purity plastic materials typically polypropylene polyvinylidene fluoride (PVFD) and Teflon

The RCA Cleaning Process involves two solution chemistries Standard Clean 1 (SC1) and Stan- dard Clean 2 (SC2) SC1 chemistry uses dilute ammonium hydroxide and hydrogen peroxide in deionized water to remove organic residues and particles from the silicon wafer surface The SC1 tank may include ultrasonic or megasonic agita- tion to remove submicron particles from the wafer SC2 chemistry involves dilute hydrofluoric acid (HF) and hydrochloric acid (HC1) The dilute HF strips the silicon wafer surface of native oxide (Si02) fopmed in the SC 1 bath The dilute HC1 re- moves trace ionics and metals from the silicon wafer surface MEMC uses several proprietary varia- tions of the RCA Cleaning Process

Rinse baths in the wafer cleaning wet bench are critical for product quality The DI water rinse following each chemical cleaning bath must remove all residual chemicals from the silicon wafer surface prevent chemical stains and prevent organic and ionic re-contamination of the wafer As a result a large volume of ultrapure rinse water is required

Another aspect of wafer cleaning is that SC 1 and SC2 chemistries are incompatible That is any chemical residual that carries over from the SC1 solution bath into the SC2 solution bath (and vice versa) will contaminate the silicon wafer surface by the forma- tion of ammonia salts This problem limits use of countercurrent rinsing and other in-process water reuse technology in silicon wafer cleaning This is also the reason for segregation of chemical process exhausts from the SC1 and SC2 sections of the wet bench cleaner as illustrated in Exhibit 1

Because of the large volume of rinse water used the concentration of chemical residuals in wafer cleaning rinse waters is low This rinse water is of- ten of acceptable quality for reuse in utility sys-

tems such as cooling towers and air pollution scrubbers In some cases the rinse waters are of better quality than the feed water supply to ultrapure water produ~t ion ~ With appropriate segregation and operating controls silicon wafer cleaning rinse waters can be returned to ultrapure water production Drains from the wet bench cleaner illustrated in Exhibit 1 are configured for rinse water recovery and reuse

Silicon wafer cleaning includes other process steps that use ultrapure water for particle removal alone Spent ultrapure water from wafer spin cleaners and from silicon wafer brush scrubbing is of high quality and suitable for recovery and reuse

MEMC Spartanburg Plant The MEMC manufacturing facility in

Spartanburg South Carolina operated from 1980 to 1999 In 1998 the semiconductor industry experienced a severe economic downturn The result was depres- sion of silicon wafer prices and a worldwide overcapacity of silicon especially 150-mm silicon wafers-the primary product produced at the MEMC Spartanburg Plant MEMC was forced by market conditions to consolidate small-diameter silicon wafer production and schedule phase-out of manufacturing at the Spartanburg facility

Despite the decision to close MEMC learned valuable lessons from water reuse initiatives at the MEMC Spartanburg plant The experience and knowledge described in the following sections transfer to other MEMC facilities and to larger diameter (gt 150 mm) silicon wafer production

Because of the large volume of rinse water used the concentration of

chemical residuals in wafer cleaning rinse waters is low

The Spartanburg Plants Water Use Problem Utility systems constructed in 1980 at the

MEMC Spartanburg plant included a 290000 gallon per day (gpd) capacity DI water plant and a


600000 gpd capacity wastewater treatment facility The Spartanburg plant operated through the 1980s with reserve capacity for both DI water and wastewater treatment flow

During 1991 and 1992 however MEPvIC increased production at the Spartanburg plant and installed new wafer cleaning and other manufacturing technology that increased plant water demand and associated wastewater flow The result was that by the end of 1992 Spartanburg plant wastewater flows exceeded the design hydraulic capacity of the existing wastewater treatment plant

This situation prompted MEMC to undertake a study of Spartanburg plant water use and al- ternatives for wastewater treatment expansion The resulting water balance is illustrated in Ex- hibit 2 Purchased water (city water) demand in 1992 averaged 712000 gpd DI water production averaged 275000 gpd and wastewater effluent

flo~c averaged 625000 gpd Reverse osmosis reject and rinse water loses represented 2 4 percent of the feed water to DI water production That is 1 24 gallons of feed water were required for every gallon of DI water produced The RO reject and rinse waters from DI water production were discharged to wastewater treatment Util- ity systems (cooling towers air pollution scrubbers and wastewater treatment) plus DI water production losses were 43 percent of purchased water demand A small volume of ccastewater effluent (36000 gpd) was recycled to operate wastewater u til i ty e q u i p me n t 0 the rw ise no water reuse or recycling was practiced at the MEMC Spartanburg plant during 1992

The 1992 study identified several hydraulic bottlenecks that limited treatment of additional wastewater flow The most significant were secondary clarifier capacity and the size of existing waste-

xhibit 21992 Water Balance Prior to Water Reuse Proect MEMC Spartanbur Plant 115 MSlE (Million quare Inch Equivalents) Actual Annual Production - 714000 gpd Total Water A e

A EVAP 14000 opd

I _-___- 360 gPd DEIONIZED WATER I

t ____ - 4 PRODUCTIDN r--^-

CITYWATER I

712M)Ogpd I A

4 EVAP 19000 gpd I i PRODUCT WATER 215 000 gpd - _ _ ~

SINGLE CRYSTAL SILIC I I b ROOgWAFER 390 ow gpd

I

k34m gpd ___ __ I MANUFACTURING )i 409 000 gpd water use

____- I 1 I

L_ EFFLUENT 625000 gpd

RIVER WASTEWATER TREATMENT ~ooooagpddevgn

I 3sw0pLM_I___ I

Evaporative loss from manufacturing adjusted to balance water use and wastewater flow data

26 Spring 2000 I Pollution Prevention Review Paul S Dickens and Alan E Madewell

water pumps and piping The capital cost estimate to expand wastewater treatment capacity from 600000 gpd to 900000 gpd (the most logical flow increment) was $12 million

The Plants Solution to the Water Use Challenge MEMC realized that a wastewater treatment

expansion at Spartanburg could be avoided if water use efficiency was improved A particular opportunity was the 43 percent of purchased water demand used in utility systems and lost in DI water production Rather than pursue a wastewater treatment expansion MEMC chose to implement a water reuse system in conjunction with a groundwater recovery and treatment system for the Spartanburg siteI3 This system would offset total site water demand by recovering and reus- ing the following

RO reject and filter rinse waters from DI water production Rinse waters from silicon wafer cleaning Treated groundwater from the groundwater recovery and treatment system

The estimated cost of the water reuse utility was $200000 This was less than 20 percent of the estimated capital cost to expand wastewater treatment facilities

Design Wafer Balance Exhibit 3 illustrates the design water balance with

water reuse for the MEMC Spartanburg plant as of January 1998 The water reuse system was installed in 1993 and began operation in August of that year The system was expanded several times until 1998 Wastewater eMuent recycling was also expanded

Exhibit 3 Desi n Water Balance with Water Reuse January 1998 MEMC Spartanburg Plant 150 MSlE Annual Producbon Basis - 880000 awl Total Water Use

CITY WATER 690000 gpd

--D --

c EVff 650w OPd

4 5 m wd - 4 EVAP20~owQpd

45000 opd REUSE WATER I

3 0 m gpd Y AIR POLLUTION 4 SCRUBBERS

100000 gpd REUSE WATER I 1 PRODUCT WATER

290000 gpd RO REJECT j WATER I A EVAP 500W ad -

I B5000 9pd

200 000 gpd MANUFACTURING 7 490000 gpd water use -

i REUSE RECOVERY WATER WATER 80 Qpd

WATER REUSE TREATED GROUNDWATER 45 OW gpd

4 lsomgpd [SYSTEM

I WASTEWATER TREATMENT BOO 000 gpd design

~- 45 000 Qpd REUSE WATER

SOW ami 7 EFFLUENT REUSE 80WO gpd

EFFLUENT 600000 apd

~ -T--- RIVER

Evaporative loss not directly related to cooling towers and air pollution scrubbers I


The design water balance provided for 880000 gpd of total water use including 190000 gpd of water reuse in plant utility systems This is a design water reuse rate of 22 percent I The design city water demand was 690000 gpd The design wastewater effluent flow was the 600000 gpd hydraulic capacity of site wastewater treatment facilities The design flow for wastewater effluent recycling to operate wastewater utility equipment was 60000 gpd

Water Reuse Components Exhibit 4 is a schematic diagram of the MEMC

Spartanburg water reuse system as of January 1998 Pump capacities tank capacities and reuse water demands are indicated There are six main components illustrated in the figure

Rinse watprs from silicon tvafer cleaning were collected in three recovery water (RCCV) sewer and pump station systems The pump stations discharged to the recovery water neutralization system Collection sumps for the recovery water pump stations were sized to equalize peak flows from quick dump rinse tanks on wafer wet bench cleaners DI water used for wafer cleaning has essentially no pH buffering capacity The recovery water had a low pH (typically 2 to 4) due to dilute acid carried over from wet bench chemical baths into rinse tanks and spent rinse water The recovery water neutralization system added dilute caustic (NaOH) to recovery water to neutralize this acidity The neutralized

Exhibit 4 Water Reuse System MEMC Spartanburg Plant January 1998

n

RECOVERY WATER NEUTRALIZATION SYSTEM

90 TO 140 GPM PUMP CApAClry 800 GAUONS

RECOVERY WATER (Rcw) SEWERS

1 AIRPOLLUTION i tEWiBERS I-)--- -( T O L V A L V E ---

RECOVERY WATER PUMP STATIONS (3)

__ 165 GPM CAPACITY TREATED GROUNDWATER

TGW 1 30TO45GPM

REVERSE

OSMOSIS REJECT SYSTEM PRESSURE gt

70 GPM

FILTER RINSE FRW 1 WATER 15000 gpd -

CITYWATER MAKEUP 0 TO 90 GPM --i

WATER REUSE PUMPS 200 TO 240 GPM CAPACITY 80 TO 100 PSI0 SYSTEM PRESSURE

BAG FILTERS 25 pm

Paul S Dickens and Alan E Madewell 28 I Spring 2000 Pollution Prevention Review

r Y

recovery water was pumped to the water reuse storage tank Treated groundwater (TGW) was piped directly to the water reuse storage tank RO reject water (ROR) and filter rinse waters (FRW) from DI water production were also piped directly to the water reuse storage tank The water reuse tank provided flow equaliza- tion and storage of the different waters recovered for reuse The water reuse tank included city water (PW) makeup in the event that reuse water (RW) demand exceeded the supply of water recovered for reuse Water reuse pumps pressurized the reuse water (RW) distribution system Major reuse water demands included cooling towers air pollution scrubbers slutige press backwash water and wastewater treatment utility water System pressure was maintained by recirculating water back into the water reuse tank through a system pressure control valve The reuse water distribution system operating pressure was 90 pounds per square inch (psi The pressurized reuse water was filtered through 25 micron (pm) bag filters to protect utility equipment connected to the water reuse system Water recirculating back into the water reuse tank was dosed with chlorine dioxide (C10) for biofouling control Automatic controls (ORP) maintained a constant C10 concentration in reuse water pumped to utility systems

Equipment Protection MEMC built several equipment protection fea-

tures into the water reuse system Since wafer cleaning rinse waters may contain dilute acid MEMC used corrosion resistant materials for recovery water sewers sumps pumps and piping For the same reason the water reuse tank was constructed of fiberglass The water reuse pumps were stainless steel and the reuse water distribution piping was plastic (PVC and CPVC) The pH controls on the recovery water neutralization system would divert

Offsetting Water Use in Silicon Wafer Manufacturing

recovery water to the plant sewer system if pH was out of range or if the pH controls failed

The piping transferring RO reject water to the water reuse tank included pressure relief valves and an over-pressure rupture disk These were necessary to prevent rupture of RO membranes and piping should a valve on the RO reject line be inadvertently closed while RO pumps were running

Controls for the water reuse tank maintained a minimum tank level of 10 percent using city water makeup as required This kept the water reuse system operating even when recovery water volume was less than reuse water demand When full the water reuse tank overflowed to the plant process sewer

Process Control Exhibit 5 outlines process control monitoring

for the MEMC Spartanburg water reuse system Daily reuse water samples and operating checks verified that automatic controls were functioning Daily flow readings tracked water reuse rate MEMC maintained trend charts of use water PH conductivity and chlorine residual The charts were a tool to detect changes in reuse water quality and to assess the effect of water reuse on cooling tower water chemistry

Since wafer cleaning rinse waters may contain dilute acid MEMC

used corrosion resistant materials for recovery water sewers sumps

pumps and piping

Results - and Growing Pains The water reuse system enabled the MEMC

Spartanburg plant to significantly increase total water use while reducing both purchased water volume and wastewater flow These accomplish- ments are illustrated in Exhibits 6 and 7

Exhibit 6 is the 1998 water balance for the MEMC Spartanburg plant During the period Janu- ary through July 1998jthe plant achieved a water reuse rate of 23 percentl4 Exhibit 7 illustrates water use and wastewater flou at the Spartanburg

Pollution hevention Review Spring 2000 I 29

1

c

Exhibit 5 Process Control Monitoring MEMC Spartanburg Water Reuse System January 1998

Parameter

Reuse Water pH

Reuse Water Conductivity

Chlorine Dioxide

Reuse Water Flow

City Water Makeup

Reuse Water System Pressure

Bag Filter Pressure Drop

Equipment Status

Recovery Water pH

Location amp Frequency (ref Exhibit 4)

Daily grab sample from port on discharge of reuse water pumps


Daily grab sample from port at reuse water makeup to main cooling tower

Total flow readings of reuse water pumped and city water makeup to water reuse tank recorded at 0730 each day

Daily reading of system pressure at discharge of water reuse pumps

Daily reading of pressure drop across reuse water bag filters

Daily checklist documenting inspection of key equipment operating condition

Weekly grab sample from recovery water neutralization tank

Operating Specification

50 to 90

Target less than 250 umhodcm

Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA

less than k 05 pH units difference from recovery water pH controller

PurposelNotes

Verify proper function of the recovery water neutralization daily results tracked with trend chart

Check for presence of excessive dissolved salts suggesting concentrated acid or other contamination of recovery water daily results tracked with trend chart

Verify that CIO system was working at correct dose daily results tracked with trend chart

Actual reuse water volume = reuse water pumped less city water makeup to reuse water tank

Verify operating condition of reuse pumps and distribution piping

Determine if bag filter change is required

Verify correct control settings and no equipment problems

Weekly grab sample to verify calibration of recovery water neutralization pH controller

plant from 1990 through 1998 Water use is read on the left scale in units of million gallons per day (mgd) and represents the sum of purchased water and reuse water Wastewater flow is read in mgd on the right scale Water reuse began in August 1993 The data represent average daily flows for each year except for 1998 data which represent seven months of operation

Exhibit 8 is a summary of annual data show- ing average daily water reuse and the correspond- ing wastewater offset and water cost savings Net annual cost savings are also presented Spartanburg water reuse in 1998 averaged 165500 gpd avoid- ing $74000 per year in purchased water cost When adjusted for the cost of pumping and caustic for

recovery water treatment the net 1998 cost savings were approximately $69900

Exhibit 9 outlines investments for the original water reuse system and subsequent modifica- tions and expansions Over the five-year period of operation covered by Exhibits 8 and 9 the Spartanburg water reuse system avoided $209600 in purchased water cost MEMC invested a total of $4 10500 in the Spartanburg water reuse system between 1993 and 1998 The payback based on 1998 reuse water rate and cost savings is 59 years a return on investment of about 12 percent More importantly water reuse enabled MEMC to avoid an expansion of wastewater treatment facilities estimated to cost $12 million in 1992 dollars

30 Spring 2000 I Pollution Prevention Review

P

Paul S Dickens and Alan E Madewell

Exhibit 6 Water Balance with Water Reuse Janua throu h June 1998 MEMC Spartanburg Plant 81 MSlE Actual Annual Production - 722000 aod Totaampater b e

A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd

i 24000 pj REUSE WATER

I I

82000 pj REUSE WATER I

- - I

PRODUCT WATER 255 OW gpd

RO REJECT

CITYWATER 556 OOO gpd -- WATER

317MOopd

- 1 5OWO opd

1 435000 gpd water use i

RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM

38000 ppd REUSE WATER

TREATED GROUNDWATER 44000 gpd

4 ~ WATER REUSE

- -

5000 gppd EFFLUENT REUSE

_- --_I


The cost of purchased water (per 1000 gallons) is presented in Exhibit 8 An unintended conse- quence of water reuse by the MEMC Spartanburg plant was an increase in purchased water price MEMC water demand in 1992 represented about 25 percent of the water distributed by the local public water authority The authority had based water rates and bond retirements for water system expansion on the assumption that MEMC would continue to purchase large volumes of water The loss of purchased water revenue when MEMC implemented water reuse in 1993 was sufficient to require recalculation of water authority rates in order to amortize bond issue cost

Wastewater Offset Wastewater flow did not decrease in a 1l ratio

with water reuse because of the effect of reuse water on cooling tower chemistry Reuse water at the

MEMC Spartanburg plant averaged about twice the concentration of dissolved salts as city water The result was an increase in both makeup and blow down rates in cooling towers operated on reuse water When running on city water MEMC Spartanburg cooling towers averaged between six and nine concentration cycles l 6 l 7 When running on reuse water cooling tower concentration cycles were reduced to between two and four to avoid mineral fouling of tower packing and heat exchanger plates

MEMC examined four years of water balance data prior to the start of water reuse to evaluate cooling tower evaporative loss and to calculate the actual wastewater offset from water reuse Annual average results are presented in Exhibit 8 Over the five-year period of operation covered by this exhibit the Spartanburg plant averaged 068 gallons of wastewater flow reduction or offset for each gallon of water reuse This is the result of the re-


- I

Exhibit 7 Water Use and Wastewater Flow MEMC Spartanburg Plant Average Daily Flows in mgd

WATER USE amp WASTEWATER FLOW MEMC Spartanburg Plant - Average Daily Flows in mgd

0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850

~ Water Reuse Started August 1993 Total Water Use = City Water + Reuse Water Goals Wastewater Flow 0600 mgd Water Reuse Rate gt 20 percent

duced number of concentration cycles in cooling towers operating on reuse water

Conductivity Upsets MEMC experienced several incidents of el-

evated dissolved salt concentrations in reuse wa-

ter recovered from wafer cleaning wet benches The worst incidents were in the third and fourth quar- ters of 1995 when a drain in a wet bench failed and allowed intermittent discharge of concentrated acid to the recovery water sewer MEMC detected the elevated dissolved salt concentration with the

Exhibit 8 Water Reuse Data Summary MEMC SDartanbura Plant

Average Purchased Average Percent Wastewater Water

Water Reuse of Total Offset gal Net Water Cost per Year gPd Water Use per gal Savings gpd 1000 gal

1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009

Net Annual Annual Cost Savings

Pumping amp from Water Caustic Cost Reuse

$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621

32 Spring 2000 Pollution Prevention Review Paul S Dickens and Alan E Madewell

Exhibit 9 Investment and Payback for Water Reuse MEMC Spartanburg Plant

I I Year Investment Scope I Payback

1993

1994 $25000 Added sodium hypochlorite feed system for biofouling control

1995

1997

$200500 Original system including water reuse tank amp pumps recovery water neutralization system recovery water pumps and piping reuse water distribution piping

$ 140000

$45000

Total $410500

Expanded recovery water system to new wet bench cleaners added bag filters to protect utility equipment on reuse water modified controls for cooling tower reuse water supply

Expanded reuse water distribution system to new utility equipment converted to chlorine dioxide feed system for biofouling control

Payback based on 1998 water reuse rate and cost savings = 587 years

trend chart for reuse water conductivity MEMC located the source of concentrated acid by corre- lating reuse water conductivity upsets with manufacturing records for silicon wafer cleaning Unfortunately repairs to the damaged wet bench drain had to wait until an extended manufacturing shutdown

The effect o n cooling tower chemistry of intermittent spikes in reuse water conductivity was profound concentration cycles dropped below two Average wastewater offset in 1995 (Exhibit 8) was only 048 gallons per gallon of water reuse The same wet bench drain problem recurred in 1997 MEMC then reworked and replaced the recovery water and process sewer drains in the offending wet bench Average wastewater offset in 1998 was 084 gallons per gallon of water reuse The improved 1998 wastewater offset reflects successful segregation of concentrated acid from wafer cleaning rinse waters collected for reuse

Biofouling Shortly after startup of water reuse in August

1993 the MEMC Spartanburg plant experienced a

series of problems with biofouling or excessive growth of microorganisms in the packing of both cooling towers and air pollution scrubbers The excessive biological growth caused operating problems with the equipment

Biofouling in the cooling towers was attributed to ammonia and sulfur bacteria that were stimulated by low concentrations of ammonia and sul- fate in reuse water that originated from wafer cleaning wet benches Biofouling in the air pollution scrubber packing was soil fungi that were also stimulated by low concentrations of ammonia and other dissolved salts in reuse water Bacteria are always present in cooling towers and will grow when favored by environmental conditions Low pH conditions in air pollution scrubbers generally inhibit bacterial growth However fungi tolerate low pH conditions and were always present in MEMCs air pollution scrubbers When operating on city water the growth rate of these fungi was low and did not interfere with airflow through the scrubber packing When operated on reuse water fungi growth would periodically explode and physically foul (plug) the scrubber packing

MEMC solved immediate biofouling problems with slug doses of biocidal chemicals to cooling towers and air pollution scrubbers supplied with reuse water The Spartanburg plant then installed a sodium hypochlorite system to chlorinate reuse water before distribution The injection point was downstream of the water reuse pumps and water reuse tank (Exhibit 4) Chlorine dose control was by flow pacing the hypochlorite feed to water reuse demand The hypochlorite system operated with limited success from 1994 until early 1997


MEMC found that a continuous free chlorine concentration of about 4 mgl was necessary to control biofouling in cooling towers supplied with reuse water Combined chlorine residual (chloramine) was not effective In hindsight MEMC realized that the hypochlorite system controlled biofouling primarily by ammonia destruc- tion during breakpoint chlorination That is reuse water with a free chlorine residual contained no ammonia and would not stimulate biological growth Whenever the hypochlorite system malfunctioned or was turned off biofouling recurred with a vengeance

MEMC sought technical assistance from the Drew Industrial Division of the Ashland Chemi- cal Company for a comprehensive solution to pe- riodic biofouling problems associated with water reuse A t Drewrsquos recommendation MEMC in-

spected the inside of the water reuse tank (see Exhibit 4) and dis- covered that the tank was full of biological growth Testing of this growth revealed that

the tank was a reservoir for ammonia and sulfur bacteria that would take hold in cooling towers whenever the hypochlorite system malfunctioned or the free chlorine dose in reuse water was low Drew representatives recommended that MEhIC replace the hypochlorite system with a chlorine dioxide (CIO) system and dose CIO directly into the water reuse tankI9 Drew provided the necessary equipment and agreed to include chlorine dioxide system operation in contract management of cooling tower water chemistry at the site

Chlorine dioxide is a powerful biocide and does n o t react with ammonia to form chloroamines This aspect of chlorine dioxide chemistry is important because rinse waters from SC 1 chemistry silicon wafer cleaning contain low concentrations of ammonia Chlorine dioxide

MFMC found that a continuous free chlorine concentration of about 4 mgl was necessary to control biofouling in cooling towers supplied with reuse water

addition to reuse water began in the second quar- ter of 1997 The CIO was generated on-site from chlorine gas and sodium chloriteLrdquo The target CIO dose at cooling towers for biofouling control was 05 mgil This required a C10 concentration of about 1 mgl in the water reuse tank Prior to startup MEMC sterilized the water reuse tank and distribution system with hydrogen peroxide and then flushed the tank and piping to remove dead biological growth

After sterilizing the water reuse system and switching from sodium hypochlorite to chlorine dioxide MEMC experienced no further problems with biofouling in utility equipment supplied with reuse water The C10 system allowed MEMC to end direct dosing of cooling towers with biocidal and algicidal chemicals All biofouling control was accomplished with CIO dosing of reuse water supplied to site utility equipment

Water Use and Production Loading The economic downturn in the semiconduc-

tor industry that led to closure of the MEMC Spartanburg plant began in the second half of 1996 and continued through 1998 Manufacturing production at Spartanburg declined from a sold out condition in 1995 to 54 percent of full production capacity in 1998 During this period MEMC realized that water use was not linear to production Purchased water demand and cvastewater flow in 1998 (Exhibit 6) were 81 percent of the design water balance at full production capacity (Exhibit 3) Total water use in 1998 was 82 percent of full production design

There are two reasons that water use did not decline in direct proportion to MEMC production

Water use in cooling towers for clean room temperature and humidity control is independent of production volume Even when clean rooms are idle temperature and humidity conditions are maintained

34 I Spring 2000 I Pollution Prevention Review Paul S Dickens and Alan E Madewell

To prevent particle and ionic contamination ultrapure water systems and wafer cleaning rinse baths are never turned off These systems operate in a low flow mode when idle but continue to consume ultrapure water

Although inefficient when production volumes decline these practices are considered es- sential for product quality Clean rooms and ultrapure water at the MEMC Spartanburg plant were turned off only during extended manufacturing shutdowns This is common practice in the semiconductor industry

Water Conservation In 1995 DI water demand at the Spartanburg

plant exceeded production capacity The plant in- stituted a DI water use reduction plan that included quarterly checks on wet bench rinse water flows The plant also installed continuous flow meters and flow restricting valves on DI water supply lines to wet bench cleaners and other equipment using ultrapure water The flow meters were wired into a data collection system that allowed continuous trend monitoring of DI water use With better information about water use manufacturing personnel were able to optimize wafer cleaning rinse water flows and reduce associated DI water demand by 15 percent with no adverse effect on product quality

During early 1998 the MEMC Spartanburg plant completed preliminary testing of an alternative wet bench tool for silicon wafer cleaning Rather than a series of chemical and rinse tanks with mechanical transfer of wafers through the tanks the alternative tool used one working tank and chemical injection systems that cycled silicon wafers through different chemical cleaning and ultrapure rinse water steps Specific technical details are proprietary Preliminary test results suggest that the alternative wafer cleaning tool can reduce ultrapure water consumption by 40 to 50 percent compared

to traditional wet bench designs used by MEMC Further evaluation of product quality from the alternative tool is required before adoption

Water Reuse M i c e at Other MEMC Facilities Exhibit 10 summarizes water reuse practice at

other MEMC manufacturing facilities MEMC facilities in St Peters Missouri and Novara Italy operate water reuse utilities similar to the MEMC Spartanburg plant These plants recover rinse water from silicon wafer cleaning and reject waters from DI water production for reuse in plant utility systems Both sites installed their water reuse utilities in the mid-1990s to avoid expansion of water supply and wastewater treatment systems In general the sites included water reuse in new capi- During early 1998 the MEMC tal projects and did not Spartanburg plant completed attempt to retrofit older preliminary testing of an manufacturing equip- alternative wet bench tool for ment or facilities silicon wafer cleaning MEMCs 200-mm wafer plant in Sherman Texas was constructed in 1996 The facility design included equipment for water reuse in plant utility systems

MEMC manufacturing plants in Japan Korea and Taiwan have restrictions on water supply volume These restrictions drove water use efficiency efforts All three factories capture rinse water from silicon wafer cleaning and return this water to ultrapure water production All three factories capture RO reject water for use in plant utility systems including cooling towers air pollution scrubbers and sewer flushing

The MEMC plant in Chonan Korea (Posco Huls Company Ltd) was constructed in 1992 The MEMC plant in Hsinchu Taiwan (Taisil Electronic Materials Corporation) was constructed in 1995 The facility design of both plants included systems for water reuse that were subsequently modified and expanded

Utility engineers at the MEMC Chonan plant developed a proprietary system to return final


Exhibit 10 Water Reuse Practice at Other MEMC Manufacturing Sites

I

36 Spring 2000 Pollution Prevention Review I

i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan

Kuala Lumpur Malaysia

Primary Products

150- and 200-mm polished amp epitaxial silicon wafers 300-mm single crystal silicon ingots

150- and 200-mm polished amp epitaxial silicon wafers

Polycrystalline silicon


Polycrystalline silicon 150- and 200-mm single crystal silicon ingots

150- 200- and 300-mm polished amp epitaxial silicon wafers

200-mm polished amp epitaxial silicon wafers

200 polished amp epitaxial silicon wafers

100- and 125-mm polished silicon wafers

Water Reuse Practice

RO reject water wafer cleaning rinse water and treated groundwater captured for use in plant utility systems (air pollution scrubbers belt press cooling towers)

Wafer cleaning rinse water and ROlEDl reject water captured for use in plant utility systems

None

Wafer cleaning rinse water and RO reject water captured for use in plant utility systems

None

Wafer cleaning rinse water returned to ultrapure water production RO reject water captured for use in plant utility systems

Wafer cleaning rinse water (process sewer) and final effluent returned to ultrapure water production RO reject water captured for use in plant utility systems


None

wastewater effluent to ultrapure water production The plant recycles 44 percent of treated wastewater flow and achieved a water reuse rate of 57 percent during 1998 This high water reuse rate allowed the Chonan plant to triple manufacturing production capacity without increasing demand on the public water supply

The MEMC Hsinchu plant copied process water recycling technology that had been demon- strated in Korea The water reuse rate for the Hsinchu facility in 1998 was 30 percent

Water reuse utilities at the MEMC plant in Utsunomiya Japan evolved as manufacturing equipment at the site was upgraded and improved The water reuse rate for the Utsunomiya facility in 1998 was 33 percent

Summary MEMC Electronic Materials Inc installed water

reuse utilities at the MEMC Spartanburg plant and at other facilities worldwide to offset water use in sili-

con wafer manufacturing The company drew the following conclusions from its experience with both in-plant water reuse and process water recycling

1 For existing MEMC plants the economic payback of water reuse in plant utility systems is moderate The cost of retrofitting existing tools and facilities for water reuse must be offset by purchased water savings Water reuse in plant utility systems is cost justified for new construc- tion New manufacturing facilities should include equipment for water reuse

2 The economic payback of returning silicon wafer cleaning waters to ultrapure water production is low and is viable only where necessary due to water supply restrictions Process water recycling into ultrapure water production increases the risk of product contamination and requires close operating controls

3 The primary drivers for water reuse at MEMC facilities are water supply restrictions and capital


avoidance of expanded wastewater treatment Water reuse enabled the MEMC Spartanburg plant to avoid a more costly wastewater treatment expansion Water reuse enabled MEMC plants in Asia to expand manufacturing production without an increase in water supply demand Water reuse utility design should anticipate im- pacts on cooling tower chemistry and potential biofouling in utility equipment The MEMC Spartanburg plant successfully resolved these problems with close monitoring of reuse water conductivity and addition of chlorine dioxide to reuse water supplying plant utility systems From the standpoint of manufacturing cost reduction water conservation is preferred over water reuse Water conservation requires new tools and technology for silicon wafer cleaning but generates direct savings in both capital and operating costs for ultrapure water Water reuse generates cost savings by offsetting water supply demand However these savings are offset by the capital and operating cost of water reuse utilities

Next Steps MEMC is currently developing manufacturing

technology for 300-mm silicon wafer production The company is also refining its technology and production cost for 200-mm silicon wafers Steps to drive process development towards water conservation include

Establish definitive company goals for water use efficiency Establish company-wide metrics for water use tracking Where cost effective transfer proven water reuse technology to existing MEMC facilities Incorporate water conservation goals into tool design for 300-mm silicon wafers Incorporate water reuse goals into facility design for 300-mm silicon wafers

Notes 1 Peter L (1997 August) Clean processing-recycling Assess- ing the risks and rewards Semiconductor International 20(9) 42 2 Semiconductor Industry Association (1997) The national technology roadmap for semiconductors technology needs environmental safety amp health - natural resources (pp 158- 159) San Jose C A SEMATECH (httpnotessematechorg NTRSRdmpmemnsfpagestochtm June 1999)

3 US EPA amp US AID (1992 September) Manual-guide- lines for water reuse EPN625R-92-004 Cincinnati OH Of- fice of Research and Development 4 Ammerman DK (1998 May) Water reclamation takes hold Water Environment and Technology 10(5) 67-72 5 Rosen E ampSheikh B (1998 May) Choosing to reuse m t e r Environment and Technology lO(5) 75-78

6 Wolfe D et al (1998 August) Combining treatment tech- nologies to eliminate wastewater discharge Pollution Engineer- ing 30(8) 38-40 7 Clark T (1998 MayJune) Wastewater reuse Industrial Wastewater 6(3) 37-43

8 Junnier et al (1999 JanuarylFebruary) It takes metal oxide and a lot of water Industrial Wastewater 7(1) 25-30

9 Peters L (1998 February) Ultrapure water rewards of recycling Semiconductor International 2 1 (2) 7 1-76 10DeJule R (1998 August) Trends in wafer cleaning Semi- conductor International 21 (9) 64-68 11 Ultrapure water (UPW quality is measured by electrical resistivity (ohms) which is the inverse of conductivity Dissolved salts (or minerals) in water increase electrical conductivity of the water and decrease the waters resistance to electrical cur- rent 3-10 megohm DI water is roughly equivalent to distilled water 18 megohm DI water contains essentially zero dissolved minerals (part per billion level or less) Semiconductor circuits are poisoned by the presence of submicron particles organic contaminants ionic contaminants (Na K Ca Mg) and trace metals (Cu AI Fe Zn Pb Cr) on the silicon wafer surface There- fore UPW used for silicon wafer cleaning must be of the high- est possible quality 12 OMara WC et al (1990) Handbook ofsemiconductor silicon technology (pp 236275-276) Park Ridge NJ Noyes Pub- lications

I3MEMC operated a recovery and treatment system for groundwater protection at the MEMC Spartanburg plant This was an interim corrective measure under the site RCRA per- mit for a historical release to groundwater under previous site ownership The water reuse system provided a conve- nient means of disposing of treated groundwater in plant utility systems Treated groundwater was less than 25 of the total volume of water captured for reuse at the MEMC Spartanburg plant 14MEMC defines water reuse rate as the ratio of reuse water (RW) volume to total water use Total water use is the sum of purchased water (PW) plus reuse water (RW) Water reuse rate is calculated percent water reuse = (RW (PW + RW)) x 100 15 MEMC announced the decision to phase out and close the MEMC Spartanburg Plant on 27 July 1998 July 1998 repre-


sents the last month of fully staffed normally scheduled production at the site

16Cooling tower concentration cycles express the ratio of makeup water rate to tower water blow down rate The number of cycles also expresses the ratio of makeup water dissolved salt concentration to tower water dissolved salt concentration For example at 4 concentration cycles tower water dissolved salt concentration is 4 times the concentration of makeup water One gallon of tower water blow down is created for every 4 gallons of tower water makeup The buildup or concentrating of dissolved salts in tower water from heat transfer and evaporation must be limited to prevent mineral fouling of tower packing and heat exchanger plates Increased dissolved salt concentration in cooling tower makeup water decreases the allow- able number of concentration cycles and increases tower water blow down rate by the same factor that concentration cycles are reduced For example a reduction in concentration cycles from 4 to 2 doubles cooling tower blow down rate

17 The Drew Industrial Division of the Ashland Chemical Com- pany was the cooling tower chemical supplier for the MEMC Spartanburg plant Drews services inrluded monitorin rool- ing tower water chemistry and recommending chemical dose rates for corrosion and biofouling control The acceptable number of cooling tower concentration cycles and adjustments required for water reuse were based on Drew recommendations Drew also assisted MEMC in evaluating control methods for

biofoulirig problems that occurred in cooling towers and air pollution scrubbers after the start of water reuse 18Hypochlorite chemistrj and equipment are discussed in White CC (1999) Hypochlorination In Handbook of chlorination and alternative disinfectants (4th Ed Chapter 2 pp 103-166) New York John Wiley amp Sons 19C hlorine dioxide chemistry and equipment are discussed in White GC (1999) Chlorine dioxide In Handbookofchlo- rination and alternative disinfectants (4th Ed Chapter 12 pp 1153-12021 New York John Wiley amp Sons 2OThe MEMC Spartanburg plant used a GENEROXTL chlorine dioxide generator and control system patented by the Drew Industrial Chemical Division of the Ashland Chemical Com- pany Information on the GENEROX unit is in the Oxidative Chemicals page of the Ashland Chemicals web site (http wwwashchemcom June 1999) Concentrated ClO solution (100 ppm) was dosed directly to the water reuse tank Chlorine dioxide dose was controlled by measuring oxidation reduction potential (ORP) in reuse water downstream of reuse water pumps The GENEROX equipment was leased and included in Drews overall contract for Tit cooling tower chemical control 21 The alternative tool tested was the VERTEQ VrSTL1 wafer cleaning process VERTEQ is a semiconductor manufacturing equipment supplier The VcS process is described in the products section of the VERTEQ web site (httplwwwverteqcom products June 1999)

Paul S Dickens is principal engineer with ARCADIS Geraghty amp Miller in Greenville South Carolina He was formerly senior engineering specialist with MEMC Electronic Materials Inc in Spartanburg South Carolina He is a registered professional engineer with more than 17 years experience as a state regulatory engineer as a consultant and for 12 years in a facilities management and environmental regulatory compliance role with MEMC Mr Dickens was the project engineer responsible for water reuse efforts at the MEMC Spartanburg Plant and was an internal consultant for water reuse efforts at other MEMC facilities His responsibilities with ARCADIS involve consulting services to industrial clients in the areas of pollution prevention environmental health and safety regulatory compliance and IS0 14001 environmental management system implementation He can be reached by email at pdickensQgmgwcom Alan E Madewell is manufacturing excellence organization specialist with MEMC Electronic Materials Inc in St Peters Missouri Mr Madewell is a registered professional engineer He has more than 13 years experience in the electronics industry 11 years of which were spent in environmental regulatory management and pollution control system operation His work experience covers a range of products including circuit boards multi-layer ceramic capacitors and silicon wafers Mr Madewells responsibilities at MEMC include initiatives for accelerated cost reduction (facilities focus) corporate coordination of performance improvements through resource utilization and efficiency analysis and support for IS0 14001 certification He can be reached by email at amadewellQmemccom

Alan E Madewell

microelectronic device size faster processing speed and improved manufacturing yield The cost of producing ultrapure water and treating resulting wastewaters was not considered a significant cost of production or an opportunity for improvement

This situation has changed The semiconductor industry matured during the 1990s and faces extreme pressure on pricing margin and manufacturing cost At the same time the industry has realized its dependence upon reliable water supplies and affordable water and wastewater utilities These infrastructure needs limit the location

and expansion of semiconductor manufactur-

Water consumption can be reduced ing facil i t ies The in two ways water conservation and efficiency of semicon-

ductor water use has water reuse

new a t ten t ion rsquo The National Technology Roadmap of the Semicon- ductor Industry Association includes definitive goals and time frames to reduce water consumption in microelectronic manufacturing Semicon- ductor equipment manufacturers and silicon material suppliers share these goals

Water consumption can be reduced in two ways water conservation and water reuse Other authors3 have discussed the benefits of and tech- nologies for water conservation and reuse in public water systems and municipal wastewater utilities Water reuse practices and opportunities in industry are product- and process-~pecific~ rsquo For industry water conservation involves new or modified process technology and equipment that use less water per unit of production in a particular process step Water reuse in industry involves one or more of the following practices

Wastewater effluent reuse is capture of treated wastewater effluent for secondary uses such as agriculture horticulture flush water or industrial cooling This practice has the effect of off-

setting water supply demand for the secondary use Wastewater effluent reuse for landscape ir- rigation and industrial cooling are common practices Strict criteria for public health protection apply where direct human contact with wastewater effluents can occur In-process water reuse involves multiple uses of water in a production step or piece of manufacturing equipment A common example is countercurrent rinsing used in elec- troplating and metal cleaning operations Relatively ldquocleanrdquo water from final rinse tanks flows opposite (or countercurrent) to product flow The final rinse water is recovered and supplied to ldquodirtyrdquo rinse tanks at the start of the cleaning line In-process water reuse is possible where water quality is not critical to product quality in upstream process steps In- process water reuse reduces water supply demand for production and associated wastewater flow Implant water reuse is the capture or recovery of rinse water and other ldquocleanrdquo process wastewaters for use in plant utility systems such as cooling towers air pollution scrubbers and wastewater treatment that do not require high quality water It has the effect of offsetting water supply demand and wastewater flow associated with utility systems In- plant water reuse requires facilities for collect- ing storing and distributing reuse water Par- tial treatment of recovered water may be required before reuse Process water recyclingis the capture or recovery of process wastewaters followed by treatment and return to the production process This is possible only where water quality after treatment is acceptable for product quality Process water recycling is practiced in industries where water supplies are limited or the production process can tolerate low-quality water Treatment steps and equipment for

lsquo

22 Spring 2000 I Pollution Prevention Review I Paul S Dickens and Alan E Madewell











growth and wafering

















1 WET LOAD


I BITH

1 LOAD PLENUM

L

QUICK DUMP RINSE 1



I - j

d


t I


I ]RINSE 1 BATH
























A EVAP 14000 opd



CITYWATER I

712M)Ogpd I A



I


____- I 1 I



I 3sw0pLM_I___ I












--D --

c EVff 650w OPd






I B5000 9pd




4 lsomgpd [SYSTEM




EFFLUENT 600000 apd

~ -T--- RIVER








n







TGW 1 30TO45GPM

REVERSE


70 GPM




BAG FILTERS 25 pm


r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell











growth and wafering

















1 WET LOAD


I BITH

1 LOAD PLENUM

L

QUICK DUMP RINSE 1



I - j

d


t I


I ]RINSE 1 BATH
























A EVAP 14000 opd



CITYWATER I

712M)Ogpd I A



I


____- I 1 I



I 3sw0pLM_I___ I












--D --

c EVff 650w OPd






I B5000 9pd




4 lsomgpd [SYSTEM




EFFLUENT 600000 apd

~ -T--- RIVER








n







TGW 1 30TO45GPM

REVERSE


70 GPM




BAG FILTERS 25 pm


r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell













1 WET LOAD


I BITH

1 LOAD PLENUM

L

QUICK DUMP RINSE 1



I - j

d


t I


I ]RINSE 1 BATH
























A EVAP 14000 opd



CITYWATER I

712M)Ogpd I A



I


____- I 1 I



I 3sw0pLM_I___ I












--D --

c EVff 650w OPd






I B5000 9pd




4 lsomgpd [SYSTEM




EFFLUENT 600000 apd

~ -T--- RIVER








n







TGW 1 30TO45GPM

REVERSE


70 GPM




BAG FILTERS 25 pm


r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell






















A EVAP 14000 opd



CITYWATER I

712M)Ogpd I A



I


____- I 1 I



I 3sw0pLM_I___ I












--D --

c EVff 650w OPd






I B5000 9pd




4 lsomgpd [SYSTEM




EFFLUENT 600000 apd

~ -T--- RIVER








n







TGW 1 30TO45GPM

REVERSE


70 GPM




BAG FILTERS 25 pm


r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell










--D --

c EVff 650w OPd






I B5000 9pd




4 lsomgpd [SYSTEM




EFFLUENT 600000 apd

~ -T--- RIVER








n







TGW 1 30TO45GPM

REVERSE


70 GPM




BAG FILTERS 25 pm


r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell






n







TGW 1 30TO45GPM

REVERSE


70 GPM




BAG FILTERS 25 pm


r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell

r Y












pumps and piping





1

c


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell


Parameter

Reuse Water pH


Chlorine Dioxide

Reuse Water Flow

City Water Makeup



Equipment Status

Recovery Water pH











50 to 90


Target 05 mgl

NA

80 to 110 psig

max 15 psig

NA


PurposelNotes














P



A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell


A EVAP 53030 gpd

I ANDBOILERS -

35 000 ppd


I I


- - I


RO REJECT


317MOopd

- 1 5OWO opd


RECOVERY WATER I

EFFLUENT 485000 gpd

I REUSE

1 WATER 9 72WOgpd

166w0gpd[SYSTEM



4 ~ WATER REUSE

- -


_- --_I








- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell

- I



0850

Q CI) E 0750

i

z 3 L 0650 3

- a 0550 U e

0450

- - 0850









1993 63750 76 084 53822 $ 100 1994 135500 168 070 95396 $ 107 1995 122750 158 048 58322 $119 1996 107750 142 061 65434 $132 1997 127500 163 063 80078 $139 1998 165500 231 084 139838 $145

Average 068

Annual Purchased

Water Savings

$ 19645 $ 37257 $25332 $31526 $40628 $74009



$1989 $ 17656 S 3304 $33953 $ 3071 $ 22261 $2922 $ 28604 $3409 $ 37218 $4081 S 69928

Total $209621




1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell



1993


1995

1997


$ 140000

$45000

Total $410500






































I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell



























I


i

Location

St Peters Missouri

Sherman Texas

Pasadena Texas

Novara Italy

Merano Italy

Utsunomiya Japan

Chonan Korea

Hsinchu Taiwan


Primary Products













None


None




None



























Alan E Madewell

















Alan E Madewell

USE IN SILICON MANUFACTURINGSilicon Wafer Cleaning Wafer cleaning is the largest use of ultrapure...

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Transcript of USE IN SILICON MANUFACTURINGSilicon Wafer Cleaning Wafer cleaning is the largest use of ultrapure...