2006
DOI: 10.1063/1.2164390
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Variation of absorption coefficient and determination of critical dose of SU-8 at 365 nm

Abstract: The absorption coefficient of thick-films of the negative photoresist SU-8 is observed to be time dependent during photolithographic exposure by I-line ultraviolet light (λ=365nm); varying linearly from 38±1cm−1 to 49±1cm−1 for a surface exposure dose of 415mJ∕cm2. We develop a general model which enables the exposure dose to be calculated at a given photoresist depth for a given exposure time. We determine the critical exposure dose for the subsequent polymerization of SU-8 having an arbitrary thickness to be… Show more

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Cited by 63 publications
(56 citation statements)
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“…The same process without reflection coating was also recently reported [64]. Another alternative was adding a top layer of a positive resist which can partially absorbs the UV light [30].…”
Section: Partial Exposure and Direct Writingmentioning
confidence: 83%
“…The same process without reflection coating was also recently reported [64]. Another alternative was adding a top layer of a positive resist which can partially absorbs the UV light [30].…”
Section: Partial Exposure and Direct Writingmentioning
confidence: 83%
“…[25] Using Equation 2, we calculated the absorption coefficient as well as the absorption depth (1/a) for all compositions ( Table 1). The absorption coefficient of 5.2 Â 10 À2 mm À1 is in good agreement with previous studies.…”
Section: Resultsmentioning
confidence: 99%
“…According to Table 1, the absorption depth at 3% w/w is about 1.2 mm which is clearly smaller than the layer thickness (2.9 mm). Considering that the photopolymerization process starts from the top of the sample, [25] this result indicates that only around 40% of the layer was polymerized through its thickness at the interference maxima positions. However, since the material in contact with the substrate was not cured, the solid SU-8 strips could be easily detached during the development step.…”
Section: Resultsmentioning
confidence: 99%
“…The intensity of the light propagating in the resist can be calculated from the UV absorption of the resist [19]:…”
Section: Simulation Of 3d Microstructure Shapementioning
confidence: 99%
“…The critical exposure dose of SU-8 ( ) was estimated from Ref. [19] to be 95 mJ/cm 2 . Thus, the shape of the microstructure can be expressed as:…”
Section: Simulation Of 3d Microstructure Shapementioning
confidence: 99%