From ahazeghi at stanford.edu Thu Sep 22 13:49:40 2005 From: ahazeghi at stanford.edu (Arash Hazeghi) Date: Thu, 22 Sep 2005 13:49:40 -0700 Subject: W wet etch Message-ID: Hi, Does anyone know what is the best way to etch W without harming the resist? I have been told to use H2O2 but I'm not sure if the resist would stand it? W is about 1um. Thanks a lot, Arash From mtang at snf.stanford.edu Thu Sep 29 14:09:49 2005 From: mtang at snf.stanford.edu (Mary Tang) Date: Thu, 29 Sep 2005 14:09:49 -0700 Subject: Particle Problem - or - Randy True is the SNF Labmember-of-the-month! Message-ID: <433C581D.5070507@snf.stanford.edu> Hi all -- A particle problem was reported which is now suspected to have originated in the spin rinse dryer at wbnonmetal. Randy's wafers and Jasmine's wafers were badly affected by this. They had processed material there on Tuesday afternoon. We strongly suspect that a wafer had been broken inside the spin rinse dryer, but cleaned itself after many cycles. A spin rinse dryer runs at very high speeds so that a broken wafer will become pulverized into silicon dust. Wafers processed there afterward will become contaminated for several cycles, until the chamber is flushed clean. The contamination that Randy describes (very fine, crystalline particles on the surface, varying in density from wafer to wafer and across some wafers, but spread out, not patchy) is very consistent with silicon dust in the spin rinse dryer. So... Let's make sure this doesn't happen again. If your wafer breaks in the spin rinse dryer, shut the dryer down, make a comment on Coral, and notify a staff member. Don't be afraid to tell someone -- accidents happen and wafers do break. Don't just wipe it up and let it go -- it needs to be thoroughly flushed, cycled several times, and then tested. It's not necessary to shutdown the wbnonmetal bench (although you should do this if in doubt), because people can still dry their wafers at wbnitride (you don't need to enable to use a spin rinse dryer.) But notifying a staff member and putting a note on the spin rinse dryer is something anyone can do. *Please realize that if you don't do this, you have contaminated other people's wafers. * Please also understand that wafers are subject to a lot of force in the spin rinse dryer. Think twice before putting wafers into the spin rinse dryer which may run the risk of breakage. (wafers with chips or damage on the edges, wafers with deep trenches following the <100> crystal planes, etc.) If you have processed wafers through wbnonmetal some time Tuesday and maybe even Wednesday, you should inspect your wafers for particles. Finally, I would like to add that Randy has been, absolutely, the model labmember through all of this. First, he was doing all the "good engineering practices" that we should all try to do: he began with a lot of extra wafers and split them up to minimize risk, he added in test wafers at each step, and he visually inspected after each critical step in the process. Somewhere between his inspections before P5000 etch and after wbnonmetal clean, he found the particles on his wafers. As soon as he discovered this, he made comments on Coral for these tools and notified staff members the following day. Having isolated the suspected steps, he then ran some more test wafers and verified that the P5000, the gasonics, and the wbnonmetal hot pots and rinse tanks were fine. Many thanks to Randy for following up on this problem and working with us on it! Mary -- Mary X. Tang, Ph.D. Stanford Nanofabrication Facility CIS Room 136, Mail Code 4070 Stanford, CA 94305 (650)723-9980 mtang at stanford.edu http://snf.stanford.edu