Resistance Reproducibility & Thermal

Coefficient of ALD coatings at Argonne

(LAPD project collaboration meeting 06-10-2010)

Anil Mane, Qing Peng, Jeffrey Elam(Group leader)

ALD Research Program, Process Technology Research Group

Energy Systems Division.

Outline

LAPD Project: Importance of atomic layer deposition (ALD)

Development of novel resistive coatings by ALD at Argonne

Electrical measurements and thermal coefficient study of resistive coatings

Next plan and Summary

LAPD collaboration Meeting

26/10/2010

LAPD project background

Apply the basic concept of “micro-channel plate” (MCP) detectors to the development of large-area photo-detectors (LAPDs) *8”x8” MCP + with quantum efficiencies and gains similar to those of photo-tubes.

To design and fabricate “economical” robust LAPDs that can be tailored for a wide variety of applications that now use photomultipliers.

LAPD fabrication divided into sub-projects:

1. Development of higher quantum efficiency photo-cathodes

2. Use of Atomic Layer Deposition (ALD) to control the chemistry and surface characteristics of resistive and secondary emission surfaces on MCPs

3. Electronics

4. Assembly

5. Testing

LAPD collaboration Meeting

36/10/2010

“Microchannel plate” detectors

44

Channels

6/10/2010

LAPD collaboration Meeting

“Microchannel plate” detectors

55

Channels

6/10/2010

LAPD collaboration Meeting

• Continuous-dynode electron multiplier in presence ofa strong electric field (~ 1kVA/MCP)

• Electron amplifier (x104-107)

6

Conventional MCP Fabrication

Draw lead-glass fiber bundle

Slice, polish, chemical etch

Heat in hydrogen

Top/Bottom electrode coating (NiCr)

Drawbacks

Expensive

Resistance and secondary emission properties are linked

Limited optimize MCP performance for applications where lifetime, gain, substrate size, composition and thermal runaway are important

MCP fabrication

6/10/2010

LAPD collaboration Meeting

7

Conventional MCP Fabrication

Draw lead glass fiber bundle

Slice, polish, chemical etch

Heat in hydrogen

Top/Bottom electrode coating (NiCr)

Drawbacks

Expensive

Resistance and secondary emission properties are linked

Limited optimize MCP performance for applications where lifetime, gain, substrate size, composition and thermal runaway are important

LAPD Approach

Start with porous, non-lead glass

ALD (resistive + SEE layer) coating

Thermal treatment

Top/Bottom Electrode coating (NiCr)

Advantages

Independent control over composition of Resistive and SEE coating

Low thermal coefficient of resistance

Applicable: Ceramics, SiO2, plastics, polymers MCPs

Low cost (No major issue for scale-up with ALD)

MCP fabrication

MCP Structure

1) resistive coating (ALD)2) emissive coating (ALD)3) conductive coating (thermal

evaporation or sputtering)

pore

Bare MCP ALD (R+SEE) Electrode (NiCr)

33 mm

6/10/2010

LAPD collaboration Meeting

8

Ultimate goal

6/10/2010

LAPD collaboration Meeting

Received from Incom Inc.

Create workable 8”x8”MCP with ALD

8”

8”

Materials selection for functionalisation of MCPs

• Secondary electron emission coating:

o Al2O3, MgO, Diamond, MgF2, …………

• Resistive coating: Composites of Metal and insulatoro Variety of material

o Reliability

o Scaling and Cost

• Why ALD process?

o Atomic level control over composition, thickness,

o Excellent uniformity and conformal coating on very high aspect ratio (>98%)

o Large area deposition, batch processing (low cost)

• Developed workable few novel resistive coatings by ALD process:

o Submitted patent application

o Here after named as Chemistry-1, 2, ….

o Tested with different ALD grown SEE layers

LAPD collaboration Meeting

96/10/2010

ALD coating on MCP: Chemistry #1 Resistivity

10

• Good control over resistivity • Several MCP pairs shows good “Gain data”

-Matt Wetstein will present status later

6/10/2010

LAPD collaboration Meeting

% of metal ALD cycles doping in oxide

1.E+06

1.E+08

1.E+10

1.E+12

1.E+14

5 10 15 20 25 30 35

Re

sist

ivit

y (

oh

m-c

m)

W % in Al2O3

Resistivity vs. % W in Al2O3 on MCP

•Linear I-V on MCP

Workable resistivity range for 33mm MCP

y = 1E-08x - 2E-09

-2.E-07

-1.E-07

-1.E-21

1.E-07

2.E-07

-10 -5 0 5 10

I(A

)

V(V)

30% W in Al2O3

MCP

ALD coating on MCP: Chemistry #1

11

• Uniform and smooth ALD coating on Si(100) surface

6/10/2010

LAPD collaboration Meeting

% of metal ALD cycles doping in oxide

1.E+06

1.E+08

1.E+10

1.E+12

1.E+14

5 10 15 20 25 30 35

Re

sist

ivit

y (

oh

m-c

m)

W % in Al2O3

Resistivity vs. % W in Al2O3 on MCP

Roughness

•Maximum RMS roughness < 3%

AFM on planer substrate (Courtesy: Hau Wang)

10% 20% 30%

0.506nm 0.889nm 1.41nm

ALD coating on MCP: Chemistry #1

12

• Uniform and smooth ALD coating pores of MCP

6/10/2010

LAPD collaboration Meeting

% of metal ALD cycles doping in oxide

1.E+06

1.E+08

1.E+10

1.E+12

1.E+14

5 10 15 20 25 30 35

Re

sist

ivit

y (

oh

m-c

m)

W % in Al2O3

Resistivity vs. % W in Al2O3 on MCP

Roughness

•Maximum RMS roughness < 3%

AFM on planer substrate (Courtesy: Hau Wang)

10% 20% 30%

0.506nm 0.889nm 1.41nm

Reproducibility: ALD Chemistry #1

6/10/2010

LAPD collaboration Meeting

13

620

630

640

650

660

0 5 10 15 20

Thic

kne

ss [A

]

# of MCP

Thickness

Thickness on Si(100) Resistance

1.E+06

1.E+08

1.E+10

1.E+12

1.E+14

0 5 10 15 20

Re

sist

ance

(oh

m)

# of MCP

On GlassOn MCP

Composition AComposition B

Composition A Composition B

• Excellent reproducible thickness and resistance on Glass• Resistance variation on MCP cause by electrode “end spoiling”

- Electrode coating plays very crucial role and need reliable source

LAPD collaboration Meeting

14

1.E+00

1.E+03

1.E+06

1.E+09

1.E+12

1.E+15

0 5 10 15

Re

sist

ivit

y (

oh

m-c

m)

Mo % in Al2O3

Data on Glass

6/10/2010

Resistivity of ALD coating on Glass: Chemistry #2

• Better control process than chemistry 1: uniform and smooth ALD coating• Similar resistivity range (like chemisty-1) with low % of metal doping• Process tested on large substrates capable ALD reactor

% of metal ALD cycles doping in oxide

•Linear I-V on Glass

Workable resistivity range for 33mm MCP

Process scale-up test: ALD chemistry #2

LAPD collaboration Meeting

15

12”x12” Glass

300mm Si wafer

Resistive coating process tested on custom made large substrate processing ALD reactor

6/10/2010

Large substrate testing: ALD Chemistry #2

LAPD collaboration Meeting

16

Item Thickness [A] Index of refraction (n)

Minimum 775 1.72

Maximum 794 1.77

Average 785 1.73

% STDV (1σ) 0.57 0.84

Thickness Index of refraction

Loca

tio

n a

cro

ss s

ub

stra

te

Location across substrate

6/10/2010

-150 -100 -50 0 50 100 150

-150

-100

-50

0

50

100

150

Y(m

m)

X (mm)

775.0

777.4

779.8

782.1

784.5

786.9

789.3

791.6

794.0

-150 -100 -50 0 50 100 150

-150

-100

-50

0

50

100

150

Y(m

m)

X (mm)

1.715

1.722

1.730

1.737

1.744

1.751

1.759

1.766

1.773

17

-100 -50 0 50 100

-1.0x10-5

-5.0x10-6

0.0

5.0x10-6

1.0x10-5

I(A

)

V(V)

30C

40C

50C

60C

70C

80C

90C

100C

20 30 40 50 60 70 80 90 100 110

106

107

108

109

Re

sis

tan

ce

(M

)

Temperature (oC)

Thermal characteristics: ALD of Chemistry #2 on MCP

I-V data at different temperature

6/10/2010

LAPD collaboration Meeting

10 20 30 40 50 60 70 80 90 100 110

16

17

18

19

Ln

(R)

Temperature(C)

Equation y = a + b*x

Weight No Weighting

Residual Sum of Squares

0.00897

Adj. R-Square 0.99779

Value Standard Error

C1 Intercept 19.41289 0.04112

C1 Slope -0.03352 5.96598E-4100M @RT

T for 100M =-0.033

Thermal coefficient

MCP Resistance (air) T

Commercial (~0.7 cm2) 6.5G -0.0451

With ALD Chemistry-1 500M -0.0337

With ALD Chemistry-2 100M -0.0335

• Linear I-V characteristic for all temperature • ALD coated MCPs shows lower T Reduced thermal runaway

Thermal coefficient of resistance = Rmcp=R0exp(-βT(Tmcp-T0))

18

1) Developed several novel ALD of resistive coating processes

-Excellent control over thickness, uniformity, resistance & thermal coefficient

2) Demonstrated the scalability of the resistive ALD process

3) Contact electrode plays crucial role in resistance tuning

-Need attention especially for 8”x8” MCP

4) Achieved all Year 1 and some Year 2 LAPD project goals for ALD group

6/10/2010

LAPD collaboration Meeting

Summary

Next plan

Gain test for several ALD functionalized MCP

MCPs are extremely sensitive to moisture Resistance optimization in vacuum

Testing of alternative ALD grown SEE layer

Process qualification on commercial ALD system

-(Beneq TFS 500, Tool installation is in progress)

Functionalization of 8”x8” MCPs on Beneq ALD system

After patent, write few publications

Thank you for your attention.

LAPD collaboration Meeting

196/10/2010