Hi Qing, I also had bubbling issue before when I used a similar type of thick film resist. I found that it is probably due to insufficient softbake time to remove a large amount of solvent from the spin-coated resist, especially your film is so thick. Those bubbles are mostly due to N2 evolution during optical exposure. Can you try increasing the softbake time to 3 mins or more for each successive bake? It may help. For the resist profile, are you doing exposure in proximity mode or vacuum contact mode? Gap between the mask and the wafer is definitely a great cause of the profile shape and angle. Vacuum contact is much better in make vertical profiles but defect generation can be a practical issue. Emulsion mask may also have difficulties in achieving highly vertical profile because of its material nature. Chrome mask is good for that purpose. Other development modalities such as puddle development, instead of immersion development, may get more vertical profile as well. Yours sincerely, Isaac Chan Ph.D. Candidate Dept. Electrical & Computer Engineering University of Waterloo 200 University Ave. W Waterloo, Ontario, Canada N2L 3G1 Tel: (519) 888-4567, ext. 6014 Fax: (519) 746-6321 iwchan@venus.uwaterloo.ca http://www.ece.uwaterloo.ca/~a-sidic On Mon, 16 Feb 2004, Qing Yao wrote: > Hi, > > I have difficulty in patterning thick photoresist. The following is what I did: > > 1> coat a 4" Si wafer with 5 layers of AZ4620 using a spinner. The thickness of each layer is about 10 microns and the total thickness of PR is about 50 microns. Bake the wafer at 110 degree centigrade for 1 min. after the deposition of each single layer. > > 2> print the image pattern on a transparency (emulsion down) using a 5080-dpi laser printer. put the transparency mask on top of the PR layer and put a 4" quartz plate on top of the mask. Then do Fusion Flood exposure. the dose is about 3300 mJ/cm2. Lots of bubbles are generated during the exposure process. > > 3> use 1:4 AZ400K to develop the PR for about 9 minutes. > > I used both optical microscope and surface profilometer to measure the side wall. The slope angle is about 50 degrees. > > However, I need the slope angle to be close to 90 degrees (at least larger than 80 degrees) so that it is almost perpendicular to the substrate. What can I do to achieve it? Would you please give me any suggestions? > > by the way, the thick photoresist layer is sort of mold (for electroless plating of Ni on Si substrate). > > > > > Best Regards, > > > Qing Yao > ___________________ > M&IE @ UIUC > _______________________________________________ > MEMS-talk@memsnet.org mailing list: to unsubscribe or change your list > options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk > Hosted by the MEMS Exchange, providers of MEMS processing services. > Visit us at http://www.memsnet.org/ >