I am using SU-8 2025
Spin coating at 4000 rpm for 30 s acoording to data sheet. Pre bake at 65 deg C for 3 min and 5 min at 95 deg C. After UV exposure post bake at 95 deg for 5 min. However I have found during developing that the unexposed area is also remaining on the Si substrate. So the pattern is not developing.
Can any one suggest what is going on and what to be done ?
Hi, Mrinal
Development rates vary depending on the thickness of the SU-8 that you made. Since you were unable to see a pattern, I would suggest maybe soaking the surface while agitating it in a fresh developer. And rinse with IPA and DW. Typically, if you see a white film while rinsing, then it probably needs to be developed more.
Hi,
As mentioned above, try to develop longer and with agitation with fresh developper. Rinsing the wafer with IPA tells you if it is undevelopped (white film). But even if you don't see this white film, it does not mean that it is fully developed. You should still check under the binocular to finely adjust the reaction.
If it does not solve the problem (note the pun), it might come from your exposure that is not following the pattern (bad contact or damaged mask).
Best,
Théo
It is possible that your aluminum mask is not blocking UV. Have a look at this chart from ThorLabs. Chrome will make a much better mask when working below 400nm.
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