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SU-8 Testing (v1g)

Thin SU8 on glass slide

Test:

(1)Soft Bake (SB) and

(2)Post Exposure Bake (PEB)

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“Control” Recipe

• Spin Coating: 10 s @ 500 rpm; 30 s @ 2000 rpm – expected thickness: 600 nm

• Soft Bake (SB): 60 s @ 93°C• Exposure: 8 s @ 275 W• PEB: 60s @ 93°C• Develop: 4 min in SU8 developer• SU8 developer rinse • IPA rinse/Nitrogen Dry

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1st Set of Tests

• 4 samples; 8 devices/sample

• 4 Wells (W)+4 Blanks (B)/sample

• S1: “Control”: Misaligned (see next slide); All shorted; R(W) ~ 8.6 Ω; R(B) ~ 10 Ω

Test Parameters for S2-4:– SB (RT Evap) and PEB @ 60°C, same times for each

• S2: 8 min:

R(W) = (2.7±0.8) Ω; R(B) = (11±0) MΩ; C(B) = (15.0 ± 0.1) pF

• S3: 13 min: Also misaligned (see next slide)

R(W) = (4.9±?) Ω; R(B) = (6 ± 8) MΩ; C(B) = (17.0 ± 0.5) pF

• S4: 15 min:

R(W) = (4 ± 1) Ω; R(B) = (11±0) MΩ; C(B) = (17 ± 0) pF

• Cracking patterns seen in S2, S3, S4

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Findings/Discussion 1st Set• “Control”: All shorted

– The “misalignment” ONLY causes 1. Top contacts don’t fully overlap guide circles on bottom that could result in

the top contact not covering the well (is this the case? If not say so) – will NOT cause short

2. Top contacts touching two exposure regions

– either single + double exposures (normal) – NOT cause short,

– or single + no exposures (should not happen but may - according to Mark, but microscopy can tell us – presence of a well – check to confirm and revise here …) – MAY cause short (ONLY no exposure)

• RT Evap + PEB @ 60°C at various times: All good– All Wells are shorted with a narrow range of R

– All Blanks have good Cs also with narrow range• Next thing to do is to estimate thickness from geometry from C

– The two longer time ones exhibit ~10% larger C (difference in dielectric constants or thickness?)

– All three show undesirable cracking patterns (under baked/sticky surface or over baked – low solvent, bubbling etc.?)

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2nd Set of Test Samples

• 4 samples• 2 “Controls”: S5-6

Test Parameters for S7-8: – 1 min PEB @ 93°C and Vary SB time @ 60°C

• S7: SB: 2.5 min• S8: SB: 5 min

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2nd Test Results - “Control 1” S5Device Capacitanc

e(pF)Resistance(Ω)

Type

1 -1 29.4 B

2 -1 0.5 W

3 9.38 3.7x106 B

4 -1 24 W

5 -1 24 B

6 -1 7 W

7 -1 421 B

8 -1 17 W

Summary: W: 4/4 Shorted B: 3/4 ShortedR(W): (12 ± 10) ΩExcluding #3 R(B): (158± 230) ΩC(B,#3) – very low (9.38 pF) compared to 1st set but comparable to S6 (also a Control - next slide).

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“Control 2” S6Device Capacitanc

e(pF)Resistance(Ω)

Type

1 Damaged 9.7 4.6x106 W

2 9.33 8.3x106 B

3 Damaged 9.61 3.04x105 W

4 9.4 1.05x107 B

5 -1 142 W

6 9.25 1.1x107 B

7 -1 46 W

8 10.3 1.2x104 B

Summary: W: 2/4 Shorted (2 Damaged by high voltage – 1V) B: 0/4 ShortedR(W): (94± 68) Ω; C(B): (9.6± 0.5) pF

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2.5 min SB S7Device Capacitanc

e(pF)Resistance(Ω)

Type

1 -1 13.4 W

2 -1 428 B

3 -1 10.8 W

4 -1 294 B

5 -1 3.7 W

6 -1 5.7 B

7 -1 4.1 W

8 -1 11.6 B

Summary: All ShortedR(B): (185 ± 211) Ω; R(W): (8 ± 5) Ω

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5 min SB S8Device Capacitanc

e(pF)Resistance(Ω)

Type

1 -1 4.8 W

2 -1 16 B

3 -1 1.9 W

4 -1 44 B

5 -1 4.3 W

6 -1 ? B

7* 15.16 Very High W

8 15.25 0.57x106 B

Summary: W: 3/4 Shorted (why not 4/4?) B: 3/4 ShortedR(Blank): (30 ± 20) Ω (#8 excluded)R(Well): (3.7 ± 1.6) Ω (#7 excluded)7*: Re-measured and consistent with capacitance

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Findings/Discussion for 2nd Set (S5-S8)

• The two “Controls”: – S5 is essentially all shorted, but R(B) > 10R(W)

– S6 is nominally good aside from the 2 damaged devices. But, the 2 shorts are too resistive (~90 Ω) compared to the “benchmark” Set 1 (~few Ω).

– C(B) are ~ 9.5 pF rather than 15-17 pF for set 1 (thicker, lower dielectric constants, etc?)

– The “Control” recipe is at best marginal thus unreliable (2 shorted and one nominally good out of 3 samples in sets 1 and 2) – consistent with prior Si wafer work (Matt)

• S7 and S8 are all shorted, but 20R(W) < R(B) and R(W)<10Ω, These are more consistent with Set 1 aside from being all shorted.

• The one good blank out of S8 has capacitance consistent with Set 1 capacitances (S2).

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“Control 2” @ 20x

This image size is good (covering the entire crossbar) – perhaps larger ones covering up to the reference dots would be even better; at the current stage, there’s no need to have too many zoomed in images.

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“Control 2” 100x

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“Control1” 100x

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2.5min SB 100x

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5min SB 100x

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3rd Set of Test Samples

• 2 samples

Test Parameters for S9-10: – 1 min PEB @ 93°C and Vary SB time @ 60°C

(longer SB compared to 2nd set)

• S9: SB: 8 min• S10: SB: 12 min

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• Back Contact not continuous – visually can’t see where it’s broken

• Measured Cs (can measure 2-terminal R)• W: 2/4 Shorted B: 1/4 Shorted• C(B): (19.3 ± 0.6) pF (excl. #2)

Device Capacitance(pF)

Resistance(Ω)

Type

1 -1 W

2 -1 B

3 12 W

4 19 B

5 -1 W

6 19 B

7 19 W

8 20 B

8 min - S9

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12 min - S10Device Capacitanc

e(pF)Resistance(Ω)

Type

1 -1 4.5 W

2 -1 18 B

3 -1 6.7 W

4 -1 121 B

5 -1 3.9 W

6 -1 127 B

7 -1 5 W

8 -1 118 B

Summary: W: 4/4 Shorted B: 4/4 Shorted Avg Well Resistance: 5.0± 1.2Ω

Avg Blank Resistance: 96± 52Ω Double Exposed (16s)

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Discussion/Findings of Set 3

• S9: – pretty much all open circuit– C(B) slightly higher than Set 1: 19 pF vs 15 and

17 pF– Current measurements unreliable because the

back contact is not continuous without visual “flaws”

• S10:– All shorted– 10R(W) < R(B)– Consistent with Set 2