Scale-Up Activities in Atomic Layer Deposition at Argonne Jeffrey Elam, Anil Mane, Joe Libera December 9, 2011 Large Area Picosecond Photodetector Collaboration.

Scale-Up Activitiesin Atomic Layer Deposition at

Argonne

Jeffrey Elam, Anil Mane, Joe LiberaDecember 9, 2011

Large Area Picosecond Photodetector Collaboration MeetingDecember 9-10, 2011, Argonne National Laboratory

Outline

Introduction to ALD (1 slide) ALD on 33mm plates Challenges with scale-up to larger substrates Conclusions

2

AlCH3

CH3

CH3OH OH OH

AlCH3

CH3

CH3

A)

B)

OHAl(CH3)3OH OH

Trimethyl Aluminum(TMA)

CH4

AlCH3

AlCH3CH3

H2OAl

CH3

CH3

CH3OH OH OH

AlCH3

AlCH3CH3 Al

CH3

CH3

CH3

CH3

OH OH OHAl Al

CH3CH3

H2O

H2OOH

CH4

OHOH

Binary Reaction Sequence for Al2O3 ALD

1 ALD Cycle of TMA/H2O Deposits 1 Al2O3 “Monolayer”

3

4

Multiple 33mm MCPs in Tubular ALD Reactor

•Thickness uniformity on monitor Si(100) <2%• The resistive layer thickness ~800A• Similar thickness trend observed on second batch of 5 MCPs Excellent batch-to-batch reproducibility

Chem-2 Resistive Coating

5

Resistance Comparison for 9 MCPs (air vs. vacuum)

• Average resistance (2 batches of 5 plates)115 ±12 M ~10% resistance variation

Chem-2 Resistive Coating

Challenges to Coating Larger Areas

Need a bigger reactor Non-ideal ALD surface reactions High aspect ratios High surface areas

6

Large Substrate Reactor

From 1x1-in plates to 12-in x 18-in plates

7

2” tube

12x18” box

Coating 8” MCPs in Beneq

8

300 mm chamber

Non-Ideal ALD Surface Reactions

9

InCp + O3 →In2O3

In2O3 O3 O* + O2

Indium oxide catalyzes ozone destruction

In2O3 films were thinner downstream in reactor

In2O3 ALD in Large Substrate Reactor

Scale-up of ALD In2O3 to 12”x18” Substrates

InCp + H2O + O2InCp + O3

Thickness deviation: 2.5% Resistivity deviation: 6%

Thickness deviation: 45%

10

Non-self limiting ALD reactions can lead to non-uniform films in larger ALD systems

15 μm

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

Tun

gste

n E

DA

X S

ign

al

Distance (Microns)

Conformal coating on all exposed surfaces Aspect ratio ~ 1000

40 nm pores, 70 microns long

11

Coating High Aspect Ratios: ALD W in Anodic Alumina

Large Substrate Surface Area: Silica Gel Powder 100 micron particles, 30 nm pores (aspect ratio ~ 2000)

Surface area = 100 m2/g Powder bed fixture for ~1 g support

12

Self-Limiting Al2O3 ALD

Self-limiting growth on planar and porous surfaces

Exposures increased by x100

0

0.5

1

1.5

0 0.05 0.1 0.15 0.2

Al 2

O3 G

row

th R

ate

(Å/C

ycle

)

TMA Exposure (Torr s)

Silica GelPlanar Surface

0

1

2

3

0 5 10 15 20 25

Wei

ght

Gai

n (

%)

TMA Exposure (Torr s)

13

Surface Areas of Glass Capillary Arrays:

14

MCP Type d (µm) γ = l/d α ATotal (cm2)33mm diam 40 40 0.65 881

40 40 0.83 1,120 20 60 0.65 1,317

8in square 40 40 0.65 43,244 20 60 0.65 64,712

(thanks Jason M.)

Empty tube reactor: ~2000cm2

Empty LSR: ~4000 cm2

Empty Beneq 300mm: ~1600 cm2

MCP aspect ratio = 60 (we’ve done 10^5)

8” MCP surface area = 6.5 m2 (we’ve done 10^3)

Piece of cake…

Work Plan

15

1) Qualify Beneq for Chem2 coatings using coupons and 33mm MCPs in new 300mm chamber

2) Coat single 8”x8” MCPs in 300 mm chamber

200 mm chamber

3) Coat multiple (1-4) 8”x8” MCPs in 300 mm chamber

X) Coat multiple (20) 8”x8” MCPs in 3D chamber

300 mm chamber

<1% non-uniformity in 100 nm coating

16

Al2O3 ALD in 300 mm Reactor

Works great!

Chem-2 ALD in 300 mm Reactor

17

Test Metrics:•Optimized chemistry -2 baseline process on 300mm chamber:•Deposit 300mm wafer at same condition as MCP deposition.•Evaluated the resistivity uniformity across the large area

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

Precursor inlet

direction

300mm

Resistivity of Chem2 coating at different locations on 300mm wafer

18

0 5 10 15 20 25 30

2.00x109

4.00x109

6.00x109

8.00x109

1.00x1010

Res

istiv

ity(o

hm-c

m)

Location on wafer

Works great for Chem-2!

Chem-2 thickness NU on 300mm wafer with 8”x8” MCP on top:2D thickness map

19

Items Run-3

Average (nm) 42.905

STDV 4.484

1sigma 0.105

%sigma 10.450

Max (nm) 57.821

Min(nm) 36.843

% diff 48.893

-100 -50 0 50 100

-100

-50

0

50

100

Y

X

36.80

39.44

42.08

44.71

47.35

49.99

52.63

55.26

57.90

•We may need square chamber?

300m

m

300mm

1-sigma thickness: 10%

August 22, 2011

8” 40µm MCP Pair Gain Map

Y gain slice

X gain slice

Y gain slice

FIRST Gain map – Looks awful - multifiber visible, lots of gain non-uniformityThis is from the thickness non-uniformity

(thanks Ossy, Jason, SSL)

20

21

300 mm wafer

8” MCP

reactor wall

Troubleshooting in Beneq

Top View

Side View

ALD conductive coating with MCP substrate installed over Si(100) 300 mm wafer

Measure film thickness on Si wafer using 4-point probe conductivity (easy, quantitative)

assumed flow distribution

Process testing on 8” MCP on Beneq

22

Items Thickness data from Resistance

Average (nm) 75.169

STDV 3.412

1sigma 0.045

%sigma 4.539

Max(nm) 78.186

Min(nm) 63.107

% diff 20.060

-100 -50 0 50 100

-100

-50

0

50

100

YX

63.10

64.99

66.88

68.76

70.65

72.54

74.43

76.31

78.20

Precursor inlet

• Baseline process: 50 cycles conductive coating (No MCP)

1-sigma = 4%

Thickness values form resistance and 2D map:

23

Items Baseline Run-1 Run-2 Run-3 Run-3# of cycles 50cycles 50cycles 30cycles 30cycles 25cycles

Expected thickness (nm) 75 75 45 45 37

Dose time (s) 1 10 20 40 60

Average (nm) 75.169 56.289 25.263 42.905 35.491

G (nm/cycle) 1.50 1.13 0.842 1.43 1.42

STDV 3.412 32.299 13.352 4.484 8.448

1sigma 0.045 0.574 0.529 0.105 0.238

%sigma 4.539 57.381 52.851 10.450 23.804

Max (nm) 78.186 110.438 46.746 57.821 47.500

Min(nm) 63.107 0.236 2.196 36.843 14.884

% diff 20.060 195.776 176.348 48.893 91.900

-100 -50 0 50 100

-100

-50

0

50

100

Y

X

63.10

64.99

66.88

68.76

70.65

72.54

74.43

76.31

78.20

-100 -50 0 50 100

-100

-50

0

50

100

Y

X

0.000

13.81

27.63

41.44

55.25

69.06

82.88

96.69

110.5

-100 -50 0 50 100

-100

-50

0

50

100

Y

X

2.000

7.600

13.20

18.80

24.40

30.00

35.60

41.20

46.80

-100 -50 0 50 100

-100

-50

0

50

100

Y

X

36.80

39.44

42.08

44.71

47.35

49.99

52.63

55.26

57.90

-100 -50 0 50 100

-100

-50

0

50

100

Y

X

14.80

18.89

22.98

27.06

31.15

35.24

39.32

43.41

47.50

Tested many ideas, hardware, software, reactor breaks, etc. (3 months)

1-sigma = 4% 57% 52% 10% 24%

24

Troubleshooting in Beneq: Al2O3

Side View

ALD Al2O3 coating with MCP substrate installed over Si(100) 300 mm wafer

Visually assess coating uniformity

Measure film thickness on Si using ellipsometry

Troubleshooting in Beneq: Al2O3

Anil: “We have a flow problem… we need a square chamber”

50 nm

100 nm

150 nm

Precursor inlet

25

Si

MCP

Troubleshooting in Tubular Reactor

26

2cm x 30 cm Si(100) substrate, rest 2x20cm MCP 2 mm above Si500 cycles TMA/H2O for Al2O3

• Narrow gap under MCP• High surface area

2 inches

26

Troubleshooting in Tubular Reactor

27

2-5-2-5, 0.05 Torr doses

2-5-2-5, 0.2 Torr doses

2-5-2-5, 1 Torr doses

Some non-uniformity, not as bad as Beneq

Si

MCP

Si

Troubleshooting in Tubular Reactor

• Narrow gap under MCP• Narrow gap over MCP• High surface area

28

Troubleshooting in Tubular Reactor

2-5-2-5, 0.05 Torr doses

Same bad non-uniformity as in the Beneq

29

30

Si

Si

Troubleshooting in Tubular Reactor

2-5-2-5, 0.05 Torr doses

Nearly perfect uniformity

• Narrow gap under MCP”• Narrow gap over MCP• No high surface area

300 mm wafer

8” MCP

reactor wall

What is going wrong in Beneq?

Top View

Side View

actual flow distribution

• Narrow gap under MCP• Narrow gap over MCP• High surface area

• No flow in the gap• Slow outgassing/diffusion from MCP• Precursors mix, CVD

31

The problem: flow is bypassing the MCP Solution: we need to confine the flow so that

it is forced to pass in the gap between the plate(s) and the reactor wall.

We have a flow problem… we need a square reactor.

What is going wrong in Beneq?

50 nm

100 nm

150 nm

Precursor inlet

32

300 mm wafer

8” MCP

reactor wall

Potential Solution, Conclusions

Top View

Side View

Equal gap

Convert circle into square

CFD modeling would be helpful

Listen to Anil33