1 SU-8 Testing (v1l) Thin SU8 on glass slide Test: Soft Bake (SB) and Post Exposure Bake (PEB)

2 “Control” Recipe 1. Spin Coating: rpm; rpm –expected thickness: 600 nm 2. Soft Bake (SB): 60 93°C 3. Exposure: W setting (power meter readings: (11.3±0.1) mW/cm 2 - done before set #1 and after set #5) 4. PEB: 93°C 5. Develop: 4 min in SU8 developer 6. SU8 developer rinse 7. IPA rinse/Nitrogen Dry –1, 3, 6, 7 are the same for all “tests” –5 is also the same for tests 1-3, and for test 4: 1 min 2

3 1 st 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 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 3

4 Findings/Discussion 1 st 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 + 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 1. Next thing to do is to estimate thickness from geometry from C 1. The two longer time ones exhibit ~10% larger C (difference in dielectric constants or thickness?) 2. All three show undesirable cracking patterns (under baked/sticky surface or over baked – low solvent, bubbling etc.?)

5 2 nd Set of Test Samples 4 samples 2 “Controls”: S5-6 Test Parameters for S7-8: –1 min 93°C and Vary SB 60°C S7: SB: 2.5 min S8: SB: 5 min 5

6 2 nd Test Results - “Control 1” S5 DeviceCapacitance( pF) Resistance( Ω) Type 129.4B 20.5W x10 6 B 424W 524B 67W 7 421B 817W Summary: W: 4/4 Shorted B: 3/4 Shorted R(W): (12 ± 10) Ω Excluding #3 R(B): (158± 230) Ω C(B,#3) – very low (9.38 pF) compared to 1 st set but comparable to S6 (also a Control - next slide).

13 S5 “Control” 100x 13

7 “Control 2” S6 DeviceCapacitance( pF) Resistance( Ω) Type 1 Damaged9.74.6x10 6 W x10 6 B 3 Damaged x10 5 W x10 7 B 5142W x10 7 B 746W x10 4 B Summary: W: 2/4 Shorted (2 Damaged by high voltage – 1V) B: 0/4 Shorted R(W): (94± 68) Ω; C(B): (9.6± 0.5) pF

11 S6 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. 11

12 S6 “Control” 100x 12

8 2.5 min SB S7 DeviceCapacitance( pF) Resistance( Ω) Type 113.4W 2428B 310.8W 4294B 53.7W 65.7B 74.1W 811.6B Summary: All Shorted R(B): (185 ± 211) Ω; R(W): (8 ± 5) Ω

14 S7 2.5min SB 100x 14

9 5 min SB S8 DeviceCapacitance( pF) Resistance( Ω) Type 14.8W 216B 31.9W 444B 54.3W 6?B 7*15.16Very HighW x10 6 B Summary: W: 3/4 Shorted (why not 4/4?) B: 3/4 Shorted R(Blank): (30 ± 20) Ω (#8 excluded) R(Well): (3.7 ± 1.6) Ω (#7 excluded) 7*: Re-measured and consistent with capacitance

15 S8 5min SB 100x 15

10 Findings/Discussion for 2 nd 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 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). 10

16 3 rd Set of Test Samples 2 samples Test Parameters for S9-10: –1 min 93°C and Vary SB 60°C (longer SB compared to 2 nd set) S9: SB: 8 min S10: SB: 12 min 16

17 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) DeviceCapacitance( pF) Resistance( Ω) Type 1W 2 B 312W 419B 5W 619B 7 W 820B 8 min - S9

18 12 min - S10 DeviceCapacitance( pF) Resistance( Ω) Type 14.5W 218B 36.7W 4121B 53.9W 6127B 75W 8 118B Summary: W: 4/4 Shorted B: 4/4 Shorted Avg Well Resistance: 5.0± 1.2Ω Avg Blank Resistance: 96± 52Ω Double Exposed (16s)

19 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

20 4 th Set of Test Samples 3 samples Test Parameters for S11-13: –10 min 60°C and Vary SB 60°C –Develop: 1 min in SU8 developer (different from previous) S11: SB: 2 min S12: SB: 5 min S13: SB: 10 min 20

21 2 min SB S11 DeviceCapacitance( pF) Resistance( Ω) Type 1 Not Exposed-B 2 Not Exposed-W 3 2.4B 411.4W 59.5B 61.7W 712.4B W Summary: B: 3/3 Shorted; W: 2/3 Shorted, 1/3 open R(B): (8 ± 5) Ω; R(W): (7 ± 7) Ω Not exposed – “operator error” by Matt 1 Well open circuit – not fully opened (due to shorter developing time?)

22 5 min SB S12 DeviceCapacitance( pF) Resistance( Ω) Type W B 32.8W B 53.2W 6*0.21B 77.2W 86.2B Summary: W: 3/4 Shorted (#1 bad); B: 2/4 Shorted (2/4 good) R(W): (4 ± 2) Ω; R(B): (3 ± 4) Ω C(B): (15.6 ± 0.1) pF; C(W): (14 ± 0) *Device 6: looked different – mixed cracking and not cracking - could be partially developed away.

23 10 min SB S13 DeviceCapacitance( pF) Resistance(Ω ) Type 16.2W *B 36.1W 41.5B 5 Not Exposed--W 64.3B 76.0W 83.6B Summary: All Shorted R(B): (37 ± 70) Ω; R(W): (6.1± 0.1) Ω *Exclude?

24 Discussion/Findings of Set 4 All have cracking –Similar to Set 1 60°C is the possible cause Nearly All shorted (S11-13) – S11: All blanks short circuit R(W) ≈ R(B) –S12: R(W) ≈ R(B) C(B) ≈ C(B:Set1) ≈15pF –S13: R(B) > 6 R(W) Only 1 “high” R with the rest equal to R(W)

26 Distribution of Resistances for “Shorted” Wells for Sets 1-4 All devices with C = -1, i.e. Test 1-4 Stats: …

27 Distribution of Resistances for Shorted Blanks (all devices) All devices with C = -1, i.e. Test 1-4 Stats: …

25 RT 60 T1 E-good T T “Control” T1-3 inconsistent Cracking No-cracking E-no good Next set: RT 90 Keep track of time E-? Crack? Next set: “pseudo Control” Keep track of time E-? Crack? Consistency?

28 5 th Set of Test Samples 3 ‘pseudo-control’ samples: S14-16 –softbake and 90°C for 1 min –vary the ‘cooling’ time after PEB S14: Cooling time: ~40s S15: Cooling time: 3min S16: Cooling time: 2min 3 RT for various times two ‘lost’ – one dropped and another misaligned S17 temp. for 10min 90°C for 1min Cooling time: ~1 min

23 S14 DeviceCapacitance( pF) Resistance(Ω ) Type 16.2W 210-B 318W 41B 5 3W 6 0.9B 711W 8130B Summary: (1/4 open blanks) (4/4 shorted wells) R(B): (44 ± 75) Ω; R(W): (10 ± 6) Ω C(B): (10 ± 0) pF

23 S15 DeviceCapacitance( pF) Resistance(Ω ) Type 113W 214-B 318W 40.2B 522W 659.6B 716W B Summary: (2/4 open blanks) (4/4 shorted wells) R(B): (30 ± 42) Ω; R(W): (16 ± 4) Ω C(B): (14.3 ± 0.4) pF

31 S15 device 7 (well) 5x

23 S16 DeviceCapacitance( pF) Resistance(Ω ) Type 1145W B 310W 412-B 514W 65B 7 341W 810-B Summary: (3/4 open blanks) (4/4 shorted wells) R(B): 5 Ω; R(W): (127 ± 155) Ω C(B): (12 ± 1) pF

33 S16 device 6 (blank) 5x

23 S17 DeviceCapacitance( pF) Resistance(Ω ) Type 1*W 29.7**B 318W 410B 522W B 716W 810B Summary: (2/3 open blanks) (3/3 shorted wells) R(B): (10) Ω; R(W): (19 ± 3) Ω C(B): (10.2 ± 0.7) pF * not exposed ** double exposed

35 S17 device 3 (well) 5x

24 Discussion/Findings of Set 5 Wells have higher resistances than previous samples S14 (40 s wait) –R(B) ≈ 4R(W), but R(B) has high standard deviation 1/4 Blanks Good C(B): 10 pF S15 (3 min wait) –R(B) ≈ 2R(W), but R(B) has high standard deviation –2/4 Blanks Good C(B): (14.3 ± 0.4) pF S16 (2 min wait) –R(W) > R(B), but R(W) has high standard deviation ? –3/4 Blanks Good C(B): (12 ± 1) pF S17 (SB:RT/PEB:90°C) –R(W) ≈ 2R(B), –2/3 Blanks Good C(B): (10.2 ± 0.7) pF Summary: –All samples have cracking – around the crossbars –Double exposed areas (off crossbars) seem to have less ‘cracking’ –Blanks have inconsistent capacitance C = (12 ± 2) pF

Additional Questions Raised by Series 5 What’s causing the cracking in the “pseudo-control” samples? Initial “controls” (S5, S6) have no cracking. Comparison of some parameters/results –Exposure settings the same. Same Dose: 90 mJ/cm 2 –Develop time the same –Slightly lower SB/PEB temp: non-cracking/cracking: (93/90)°C –C(S6): (9.6± 0.5) pF, C(S14-16): (12± 2) pF RT SB 60°C vs 90°C –Both cracked. So PEB temp doesn’t heal cracking –R(W:60°C) < R(W:90°C); 5 Ω vs 18 Ω –C(B:60°C) > C(B:90°C); 16 pF vs 10 pF 37