From patlu at Stanford.EDU Wed Oct 25 14:36:09 2006 From: patlu at Stanford.EDU (Patrick Lu) Date: Wed, 25 Oct 2006 14:36:09 -0700 Subject: first time etching small pieces, mounting advice needed Message-ID: <5ef4413c0610251436g7e4b35bakb20ef604636b59e6@mail.gmail.com> Hey all, I usually etch entire wafers, but now I have some smaller quartz-substrate chips. Anyone have advice on how I should mount these to my handle wafers? Tape? resist? Thanks for any info, Patrick -------------- next part -------------- An HTML attachment was scrubbed... URL: From wistey at snow.stanford.edu Wed Oct 25 16:13:51 2006 From: wistey at snow.stanford.edu (Mark Wistey) Date: Wed, 25 Oct 2006 16:13:51 -0700 Subject: first time etching small pieces, mounting advice needed In-Reply-To: <5ef4413c0610251436g7e4b35bakb20ef604636b59e6@mail.gmail.com> References: <5ef4413c0610251436g7e4b35bakb20ef604636b59e6@mail.gmail.com> Message-ID: At 2:36 PM -0700 10/25/06, Patrick Lu wrote: >I usually etch entire wafers, but now I have some smaller >quartz-substrate chips. Anyone have advice on how I should mount >these to my handle wafers? Tape? resist? It depends on the uniformity you need. For fairly large pieces, or if you don't need good uniformity in your etch, you can use double-sided *conductive* copper tape (see the instructions in the PQuest manual for the 3M part number). Cover the entire backside of your sample with the tape, but don't expose any of the copper. (Copper is bad for many people's projects.) The sample will get hot around the edges and corners, so it will etch faster there. If you need better uniformity, we've had very good results tightly packing the sample with fairly large dummy pieces, and using no tape under the sample itself. You want good thermal conduction between your sample and the dummy pieces. The dummies can be held on with copper tape, but we've had better results soldering them down with indium on a hotplate. For best results, the mounted height of the dummy should equal the height of your sample. Set the chiller and chuck to a low temperature (-10 and 0, respectively). Again, make sure there's no exposed indium, because exposed metal will change the plasma characteristics near your wafer. We've gotten <10% etch variation over ~95% of a 1" sample this way, compared with ~30% variation using copper tape. Whichever route you take, of course, make sure you're starting with one of the prime p-doped Si wafers specifically stocked for the PQuest, since other types are likely to fall off the pins and/or break. - Mark