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SU-8 Testing ( v1l)

SU-8 Testing ( v1l). Thin SU8 on glass slide Test: Soft Bake (SB) and Post Exposure Bake (PEB). 1. “ Control ” Recipe. Spin Coating: 10 s @ 500 rpm; 30 s @ 2000 rpm expected thickness: 600 nm Soft Bake (SB): 60 s @ 93°C

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SU-8 Testing ( v1l)

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

  2. “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 setting (power meter readings: (11.3±0.1)mW/cm2 - done before set #1 and after set #5) • PEB: 60s @ 93°C • Develop: 4 min in SU8 developer • SU8 developer rinse • 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 2

  3. 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 3 3

  4. Findings/Discussion 1st Set • “Control”: All shorted • The “misalignment” ONLY causes • 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 • 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.?) 4

  5. 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 5 5

  6. 2nd Test Results - “Control 1” S5 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 1st set but comparable to S6 (also a Control - next slide). 6

  7. S5 “Control”100x 13 13

  8. “Control 2” S6 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 7

  9. S6 “Control”@ 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 11

  10. S6 “Control”100x 12 12

  11. 2.5 min SB S7 Summary: All Shorted R(B): (185 ± 211) Ω; R(W): (8 ± 5) Ω 8

  12. S7 2.5min SB 100x 14 14

  13. 5 min SB S8 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 9

  14. S8 5min SB 100x 15 15

  15. 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). 10 10

  16. 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 16 16

  17. 8 min - S9 • 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) 17

  18. 12 min - S10 Summary: W: 4/4 Shorted B: 4/4 Shorted Avg Well Resistance: 5.0± 1.2Ω Avg Blank Resistance: 96± 52Ω Double Exposed (16s) 18

  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 19

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

  21. 2 min SB S11 • 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?) 21

  22. 5 min SB S12 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. 22

  23. 10 min SB S13 Summary: All Shorted R(B): (37 ± 70) Ω; R(W): (6.1± 0.1) Ω *Exclude? 23

  24. Discussion/Findings of Set 4 • All have cracking • Similar to Set 1 • PEB @ 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) 24

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

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

  27. Next set: SB @ 90 PEB @ 90 “pseudo Control”Keep track of time E-? Crack? Consistency? SB @ RT PEB @ 60 T1 E-good SB @ 60 PEB @ 93 T2-3 SB @ 60 PEB @ 60 T4 SB @ 93 PEB @ 93 “Control” T1-3 inconsistent Next set: SB @ RT PEB @ 90 Keep track of time E-? Crack? Cracking No-cracking E-no good 25

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

  29. S14 • 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

  30. S15 • 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 23

  31. S15 device 7 (well)5x

  32. S16 • Summary: (3/4 open blanks) (4/4 shorted wells) • R(B): 5 Ω; R(W): (127 ± 155) Ω • C(B): (12 ± 1) pF 23

  33. S16 device 6 (blank)5x

  34. S17 • 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 23

  35. S17 device 3 (well)5x

  36. 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 24

  37. 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/cm2 • 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 Ωvs 18 Ω • C(B:60°C) > C(B:90°C); 16 pF vs 10 pF

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