Dear Rajib Ahmed I believe that the SU-8 xx mixtures are formulated in gamma-butyrolactone [CAS No. 96-48-0] and the SU-8 20xx mixtures are made with cyclopentanone [CAS No. 120-92-3]. You can add one of these readily available chemicals to your photoresist, but I would make sure that 1) the solvents are dry (I use baked out 4A molecular sieves), 2) the solvents are filtered before use (I use a 0.1 micron PTFE syringe filter), and 3) the resulting mixture is homogeneous. The last point should be easy to achieve because the mixture will be very thin and not very viscous. I usually degas the resist in a sonic bath at about 40 C before use. For very thin layers, I usually use a mixture that contains about 20 wt% SU-8. SU-8 5 is 52wt% solids; I would estimate SU-8 2 to have 46-47wt% solids. If you want to dilute that to 20wt%, you'd add about 1.3g of GBL per gram of SU-8 5. The spin coating parameters are: rotational speed = 4000 rpm, acceleration & deceleration = 300 rpm/s, time at speed = 30 s. This works well and gives an even coat on clean baked fused silica and glass. (These are essentially featureless, though, and I don't know what your case is.) Regards, Chris Blanford On Friday, August 9, 2002, at 02:11 pm, Rajib Ahmed wrote: > I was wondering if any of you ever used SU-8 as a dielectric coating. > Currently we have been using it in microfluidics applications, but the > problem is our coatings turn out quite thick. I believe we are using > SU-8 > 2 for this process. This is supposed to give you the thinnest coating > which I believe is in the order of ~2 micron. I was wondering if the > coating process can somehow be altered/modified to make it even thinner. > Any suggestions? Also we are spin coating SU-8 onto our substrates. I > am > suspecting that this process reveals its limitations in terms of > coverage > of the whole area. From visual inspection, I could see that there are > places where the coating didn't cover at all. Could anyone kindly > suggest > a more effective method of coating? -- Christopher F. Blanford Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK Phone: (44)/(0)-1865-282603; Fax: (44)/(0)-1865-272690 PGP keyID: 8D830BC9 http://pgp.mit.edu/