Application of insitu Plasma Measurement Techniques on ... · non-equilibrium chemistry Present...

April 6, 2005

Andreas SteinbachSven BarthInfineonTechnologies DresdenMarco ReinickeDresden University of Technology

Application of insitu Plasma Measurement Techniques on Etch Hardware Design and Process

Development for 60nm Structures

Andreas Steinbach, Sven BarthPilot Fab 300Infineon Technologies Dresden, Germany, [email protected]

Marco ReinickeSemiconductor and Microsystems Technology LaboratoryDresden University of Technology, Germany, [email protected]

mailto:[email protected]



April 6, 2005


Acknowledgement

The authors are very thankful for their support from:– Axel Henke

Stephan WegeJörg SobeInfineon Technologies Dresden, Germany

– Michael KijowskiRuhr University Bochum, Germany

– Ralf NäkeUniversity of Applied Sciences, Dresden, Germany

The work for this paper was partly supported by the EFRE fund of the European Community and by funding of the State of Saxony of the Federal Republic of Germany, project SENSOR, project number 7700 and 7701. The authors are responsible for the content of the paper.

April 6, 2005


Outline

Challenges in Dry Etch Technology todayParadigm Shift in Process DevelopmentInsitu Plasma Measurement Techniques for Hardware Design and Process Development Application on Chamber and Process Development

– Power dissipation and RF frequencies– Chamber conditioning– Process development

Conclusions and Summary

April 6, 2005


Demands of Dry Etch Technology Development

Feature Size

4nm5nm6nmDeep Trench CD control

12010080Deep Trench Aspect Ratio

403530Deep Trench Mask Open Aspect Ratio

4x nm5x nm6x nm

DRAM Dry Etch Challenge

Main challenges for future dry etch technology development:– Increasing aspect ratio– Tight CD control– Mask selectivity– Uniformity improvement on 300mm wafers

April 6, 2005


Example of Technology Challenge:Deep Trench Aspect Ratio at DRAM

Aspect ratio increases exponentially !

20

30

40

50

60

70

80

90

100

110

00,050,10,150,20,250,3

Aspect ratio

Aspect Ratio Challenge

Technology

April 6, 2005


Conventional Methodology at Plasma Process Development

~~~

Mask

R +R

RR++

++

++

+

+

+

+ +

+ ++ +

Chamber = ToolboxPlasma = Tool:

in non-equilibrium and non-linearTransport processes:

non-linearReactions on wafer:

non-equilibrium chemistry

Present Methodology:– Offline measurements on blank and patterned wafers after process– Experience and statistical analysis (DOE)– Insitu measurement methods are rarely used

Needed:– Sufficient characterization and control of wafer surface conditions– Significantly improved “tool” = plasma characterization

April 6, 2005


Outline

Challenges in Dry Etch Technology todayParadigm Shift at Process DevelopmentInsitu Plasma Measurement Techniques for Hardware Design and Process Development Application on Chamber and Process Development



April 6, 2005


Paradigm Shift at Plasma Process Development

Paradigm shift: – Joint development of chamber hardware and process by tool

vendors and customers – Joint application of insitu and exsitu measurement methods for

chamber hardware design and process developmentGoal: Process development excellence

– Increase of process development efficiency– Reliable tool hardware and process as basic requirement of AEC/APC

The following measurement methods have been used:– Quadrupol Mass Spectroscopy (QMS)– Optical Emission Spectroscopy (OES) with high and low resolution– Self-Excited Electron Resonance Spectroscopy (SEERS)– RF voltage, current and phase measurement (V,I Probe)– RF Network Analysis

April 6, 2005


Measurement Equipment Setup for Chamber Hardware and Process Development at 300mm Etch Chamber

Anode (GDP)

RF Matchbox

RF Matchbox

Z-Scan

VI Probe

~~~

~~~

2 MHz

60 MHz

SEERS

Pump System

QuadrupolMS

OMA

Cathode (CESC)

Wafer

Plasma

Vacuum PumpN2

N2

Final Valve

Slit Valve

Anode (GDP)

RF Matchbox

RF Matchbox

V,I Probe

V,I Probe

~~~~~~

~~~~~~

2 MHz

60 MHz

Gas Inlet

SEERS

Pump System

QMS

OES

Throttle Valve

Cathode (CESC)

Wafer

Plasma

Vacuum PumpN2

N2

Slit Valve

Gas 1…..Gas n

All experiments performed in production environment

April 6, 2005


Outline

Challenges in Dry Etch Technology todayParadigm Shift in Process DevelopmentInsitu Plasma Measurement Techniques for Hardware Design and Process DevelopmentApplication on Chamber and Process Development



April 6, 2005


Quadrupol Mass Spectroscopy (QMS)

Current measurement position above throttle valve:

– Gas composition analysis– Detection of stable gas components

(no ions or neutrals)

Advantages of planned QMS installation at chamber wall:

– Detection of ions and neutrals– Measurement of plasma potential– Ion energy analysis at chamber wall

+

+

R

+

+

R+

++

+

+

GDP

CESC

Wafer

Throttle GateValve

HART TS™ Chamber

Plasma

Quadrupol MS

April 6, 2005


Optical Emission Spectroscopy (OES)

Spectral range: 300nm – 900nmSpectral Resolution: app. 0.2nmSampling rate: app. 90s per full

spectrum

Spectral range: 200nm – 950nmResolution: > 1nmSampling rate: min. 20ms per full

spectrumFocus on detailed analysis of

molecular speciesFocus on complex DoE

parameter scans

Acton Research SpectrometerFocal length: 500 mm

Hamamatsu Optical MultichannelAnalyzer (OMA)

High resolution OESLow resolution OES

April 6, 2005


Self Excited Electron Resonance Spectroscopy (SEERS)

RF current

ei

n

eff ν(ve-1)p

pkTp

⋅⋅+≈ ∑ σν νstoch

≈ n -1 dV∼ne V1( )-1

V∫

Electrons are key in electrically excited plasmaElectron collision rate νeff reflects: – Excitation – Ionization rates

Electron density ne is:– Plasma density– total number of positive - negative ions

April 6, 2005


RF Voltage and Power Measurement by V,I Probe

Ugenerator Umatchbox Uplasma

~~~50 Ω Matchbox Plasma

Lfeedthrough R

CfeedthroughV,I Probe

Measurement of RF voltage, current and phase at RF matchbox output

– RF power dissipation in feedthrough and plasma can not be separated– Above chamber resonance frequency feedthrough impedance

dominates load impedance significant voltage difference between RF matchbox output and plasma

April 6, 2005


Chamber Impedance Measurement by Network Analyzer

Measurement of chamber and feedthrough impedance without plasma by Network Analyzer

Chamber = DUT

Device Under Test

1

111 a

bS =02 =a

a1 a2

b1 b2

April 6, 2005


Outline

Challenges in Dry Etch Technology todayParadigm Shift in Process DevelopmentInsitu Plasma Measurement Techniques for Hardware Design and Process Development Application on Chamber and Process Development



April 6, 2005


Power Dissipation and RF Frequencies: 2MHz Bias Power Impact on 60MHz Source Power

60MHz Delivered vs. Setpoint Power

250

500

750

1000

1250

1500

1750

2000

2250

2500

250 500 750 1000 1250 1500 1750 2000 2250 250060MHz Setpoint Source Power [W] @ 1750W BP

60M

Hz D

eliv

ered

Sou

rce

Pow

er [W

]

500W Bias1000W Bias1500W Bias2000W Bias

Interaction of 2MHz and 60MHz RF power sources was detected by V,I probe measurements60MHz source power loss increases with:

– Higher nominal source power

– Decreasing 2MHz Bias Power

Possible root causes: RF matching limits, temperature drift effects

60MHz Delivered Source Power vs. RF Power

700

800

900

1000

1100

1200

250 500 750 1000 1250 1500 1750 2000 2250 2500Setpoint Source Power [W] @ 1750W BP

60M

Hz D

eliv

ered

Sou

rce

Pow

er [W

]

500W Bias

1000W Bias1500W Bias

2000W Bias

Delivered Power = Setpoint Power

HBr Plasma

April 6, 2005


Phase of Load Impedance Z vs. Frequency

-90

-65

-40

-15

10

35

60

85

30 35 40 45

Frequency [MHz]

Phas

e [°]

200mm chamber300mm chamber

1 10 10010

0

10Voltage ratio vs. ferquency

10

10−

U plasma 2 π⋅ f⋅( )

U matchbox

1001 f

MHz

calculatedmeasured

U plasma ω( ) U matchbox1

1 ω2

C feedthrough⋅ L feedthrough⋅−:=U plasma ω( ) U matchbox

1

1 ω2

C feedthrough⋅ L feedthrough⋅−:=

Power Dissipation and RF Frequencies: Chamber Resonance Frequency Analysis

Resonance frequency at about 37 …38 MHzResonance frequency depends mainly on RF feedthrough

Nearly no impact of chamber geometry (200 mm or 300 mm)60MHz excitation is above chamber resonance

considerable RF voltage loss at feedthrough

See Presentation 1.3 at 5th European AEC&APC Conference, Dresden, 2004

April 6, 2005


Chamber Conditioning: Monitoring and Baseline by Electron Collision Rate

Electron collision rate vs. process time

1,0E+06

1,0E+07

1,0E+08

1,0E+09

0 20 40 60 80 100 120time [s]

El. C

oll.

rate

[s-1

]Exp_1a Exp_1bExp_1c Exp_2Exp_3 Exp_4

RF Match Issues

stable

unstable

Chamber conditioning was instable due to many different productive lots running in parallel !Electron collision rate directly indicates:

– Chamber hardware issues– Stability and reproducibility of chamber conditioning

April 6, 2005


Chamber Conditioning: Chemical Impact of Fluorine Clean and HBr Plasma

79Br Partial Pressure vs. Process Time

1,0E-08

1,0E-07

1,0E-06

1,0E-05

1,0E-04

0 602 1204 1806 2408 3010Time [s]

Par

tial P

ress

ure

[mTo

rr] N2

PlasmaN2

PlasmaN2

PlasmaN2

PlasmaHBr NF3

HBr plasma NF3 plasma

QMS application to optimize chamber clean procedure:– Goal: Stable and

reproducible conditioning

– Effectively decrease fluorine (bromine) contamination inside chamber by HBr (NF3) plasma or purgeF + HBr → HF + Br

– Mass spectrometer useful to monitor behavior of Br/HF species

19F Partial Pressure vs. Process Time

1,0E-08

1,0E-07

1,0E-06

1,0E-05

1,0E-04

1,0E-03

1,0E-02

0 420 840 1260 1680 2100 2520 2940Time [s]Pa

rtial

Pre

ssur

e [m

Torr

] N2plasma

N2plasma

N2plasma

N2plasma

NF3plasma

HBr

HBr purge

HBr plasma

April 6, 2005


3000 4000 5000 6000 7000 8000 90000

10000

20000

30000

40000

inte

nsity

[a.u

.]

λ [Å]

Process Development: Why Application of High and Low Resolution OES ?

High resolution OES: Detailed identification of plasma species for process developmentOptical Multichannel Analyzer with low resolution and high speed: Parameter field measurement and DoE experiments, see next page

6800 6850 6900 6950 7000 7050 7100 7150 72000

4000

8000

12000

16000

20000

24000

28000

F (6

834.

260)

F (6

856.

030)

F (6

870.

220)

F (6

902.

470)

F (6

909.

810)

F (7

037.

460)

F (7

127.

890)

F (7

202.

360)

inte

nsity

[a.u

.]

λ [Å]

0

5000

10000

15000

20000

25000

30000

35000

680 685 690 695 700 705 710 715 720wavelength [nm]

inte

nsity

[a. u

.]

Lowresolution

NF3 Plasma

High resolution

April 6, 2005


Process Development: B- Field and RF Power Impact on Plasma Excitation

Simple model gas used: N2

Electron collision rate indicates nonlinear energy transfer from RF power to gas by electronsOptical emission indicates ionic and neutral species in excited states

Electron Collision RateN2 Emission 337.1nm N2+ Emission 423.7nm

April 6, 2005


Process Development: Source Power Impact on NF3 Etch Gas Fragmentation

Partial Pressure vs. RF Power

1,0E-07

1,0E-06

1,0E-05

1,0E-04

1,0E-03

1,0E-02

250 500 750 1000 1250 1500 1750 2000 2250 2500Setpoint Source Power [W] @ 1750W BP

Par

tial P

ress

ure

[mTo

rr]

NF(+)F2(+)NF2(+)NF3(+)O2(+)SiF3(+)

SiF3(+)

O2(+)

NF3 fragmentation increases with higher source power

Attention: Decrease of O2 and increase of SiF3indicate complete removal of SiO2hardmask only

Partial Pressure vs. RF Power

6,7E-04

6,8E-04

6,9E-04

7,0E-04

7,1E-04

7,2E-04

7,3E-04

250 500 750 1000 1250 1500Setpoint Source Power [W] @ 1750W BP

Parti

al P

ress

ure

[mTo

rr]

1,0E-07

6,0E-07

1,1E-06

1,6E-06

2,1E-06

2,6E-06

3,1E-06

3,6E-06

4,1E-06

Parti

al P

ress

ure

[mTo

rr]

F(+)NF(+)NF2(+)NF3(+)

F(+)

NF(+)

NF2(+)

NF3(+)

NF3 Plasma

April 6, 2005


Process Development: B-Field and RF Power Impact on Electron Collision Rate

200 mTorr70 mTorr

Electron collision rate depends on relation between mean free path of gas molecules and electron Larmor Radius.Larmor Radius is an nonlinear function of 60MHz Source Power, 2MHz Bias Power and B- Field !

April 6, 2005


Process Development: RF Source and Bias Power Impact on Plasma Density and Gas Excitation in NF3

Electron densityincreases with sourcepower and changesgas excitation and fragmentationOutlier indicates biaspower dominance at low source powerAll measuredparametersdemonstrate drift of process conditionsduring themeasurements.

5000

10000

15000

20000

25000

30000

35000

40000

250 500 750 1000 1250 1500 1750 2000 2250 2500 275060MHz Setpoint Source Power [W] @ 2MHz 1750W BP

Emis

sion

Inte

nsity

[cts

]

2,0E+09

4,0E+09

6,0E+09

8,0E+09

1,0E+10

1,2E+10

1,4E+10

1,6E+10

Elec

tron

Dens

ity [c

m-3

]O(844.6nm)

F(703.8nm)

Electron Density

1,0E-06

1,0E-05

1,0E-04

1,0E-03

1,0E-02

250 500 750 1000 1250 1500 1750 2000 2250 2500 275060MHz Setpoint Source Power [W] @ 2MHz 1750W BP

Part

ial P

ress

ure

[mTo

rr]

2,0E+09

4,0E+09

6,0E+09

8,0E+09

1,0E+10

1,2E+10

1,4E+10

1,6E+10

Elec

tron

Den

sity

[cm

-3]O(+)

F(+)

NF(+)

NF2(+)

Electron Density

Outlier indicates dominance of 2MHz Bias Power in range of 60MHz Source Power (SEERS model range)

April 6, 2005


Summary:The Paradigm Change in Plasma Process Development

Joint development work by tool vendors and customersJoint application of insitu and exsitu measurement methods

Enable to

Improve knowledge of tool characteristics and plasma process conditions significantlyAccelerate plasma etch tool and process developmentDevelop reliable tools and processes as a basic precondition of AEC/APC in production

April 6, 2005


… Finally a possible Back Up Solution, if the Paradigm Shift should not work …

Application of insitu Plasma Measurement Techniques on ... · non-equilibrium chemistry Present...

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