Thin SU-8 Testing on Glass Slides: Bake and Exposure Parameters Analysis

1. SU-8 Testing (v1f) Thin SU8 on glass slide Test: Soft Bake (SB) and Post Exposure Bake (PEB)

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 • PEB: 60s @ 93°C • Develop: 4 min in SU8 developer • SU8 developer rinse • IPA rinse/Nitrogen Dry

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: 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

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) • 30 min RT Evap+ various PEB time @ 60°C: 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 PEB 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.?)

5. 2ndSet 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

6. Finding Discussions for 2nd Set (S5-S8) • Comparing the Controls: S5 is essentially all shorted while S6 is nominally good aside from the 2 damaged devices. To note however the shorts are much higher resistances than from Set 1. • S7 and S8 are all shorted but with R(W) < R(B) and R(W)<10Ω

7. 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).

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

9. 2.5 min SB S7 Summary: All Shorted R(B): (185 ± 211) Ω; R(W): (8 ± 5) Ω

10. 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 (need to double check R)

11. “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.

12. “Control 2” 100x

13. “Control1” 100x

14. 2.5min SB 100x

15. 5min SB 100x

16. 3rd Set of Test Samples • 2 samples Test Parameters for S9-10: • 1 min PEB @ 93°C and Vary SB time @ 60°C • S9: SB: 8min • S10: SB: 12 min

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)

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)