Would you recommend using KOH to etch lapped surfaces in lieu of SC-1, SC-2, or other acid etching solutions? Standard cleans tend to leave undesirable silicon oxide layers (stains). We simply want to clean the surface - the KOH doesn't necessarily remove metals, though. Would you recommend a combination of steps using both acids and bases? George -----Original Message----- From: mems-talk-admin@memsnet.org [mailto:mems-talk-admin@memsnet.org] On Behalf Of Campman96@aol.com Sent: Sunday, January 06, 2002 11:59 AM To: mems-talk@memsnet.org Subject: [mems-talk] Etching <100> and <110> wafer in KOH and surface roughness This reply was intended Onnop. Many other readers presumed I was talking about other issues other members were having. Original reply as Follows: If you got poor results in etching (110) you either had too much water in your etch or your wafer was of axis by several degrees. What is your etch solution composed of and at what temperature are you etching at? An off axis wafer, which are sliced on purpose that way for diffusion control, will show what looks like a stair case of many steps. If the cause was too much water then you get pits and bumps and even lines. Let us know which problem you had and the solution is at hand. Excellent results can be obtained using KOH to etch silicon, but the presence of water in the etch changes the etching characteristics to result in undesirable results. In my production experience in etching several (8 to 10) mils (0.001") deep it is extremely important that the KOH be of high purity with very low moisture content. If the KOH is not from an unopened bottle and all free flowing pellets in the bottle than it has too much moisture already absorbed and will produce poor etching results. As the moisture level increases the etch rate for dislocations and stacking faults increases and the etch becomes less crystallographic in nature. Onnop, I hope this helps. Campman _______________________________________________ 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.mems-exchange.org/