From eap at gloworm.Stanford.EDU Wed Apr 1 03:03:16 2009 From: eap at gloworm.Stanford.EDU (Eric Perozziello) Date: Wed, 1 Apr 2009 02:03:16 -0800 (PST) Subject: Furnace Protocol In-Reply-To: <49C42346.3040304@stanford.edu> Message-ID: This is obviously a bigger issue than just furnace non-uniformity- FIRST: ?SNF began reducing the Tylan oxidation tubes' idle temperature to 500C from 800C during periods when tubes are not reserved.? This change was only recently discovered after tubes were noticed idling under the recipe "500AN."? The reason given was "to save?electricity."?? Users are now told to turn up the heat "right before you clean your wafers," but the temperature is far from uniform in the tube in one hour. ? There were no prior announcements or discussions with the general lab user base, and no calculations or tests were done before making this drastic change.?? As we might expect, this change has resulted in big variations in both in-wafer and wafer-to-wafer uniformity due to insufficient heat soak of the equipment. (My cat never studied physics, but even he is well aware, it takes a lot longer to warm some places in the house even though the thermostat reaches its setpoint.) Here are some reports from lab users: ? "It seems that the oxide thickness uniformity was still pretty good until at least Feb 2009.? Now the oxide thickness increases gradually from the top to the bottom of wafer (flat at bottom), with variations?of as much as 15nm within wafer (used to be < 5 nm)." ? And another: ? "very big variation in quals: According to the quals on 3/18, both in-wafer and wafer-to-wafer variation are very large. I also observed non uniform oxidation recently. We may need inspection." ? What is the purpose of running quals when nothing is done or said when they fail? Apathetically, the tubes are still being ramped down (31-March) almost two weeks after a bad qual, reiterated by users. ? SECOND:? ?TLC CLEANS used to be run twice a week on each tube because contamination diffuses in from the the tube, and not just because of tool usage.??This seems to be misunderstood by staff, given recent comments posted. Why bi-weekly cleans ceased is not clear, other than a lack of?necessity on the part of the lab to make real, working devices along with the lab users. We've gone from technician-run TLCCLEANS twice a week, to not running them often, to now technicians complaining when users run them. ? Can we please have a bona-fide engineer or scientist review any changes like this, AND POST THEM FOR COMMENT before wrecking people's experiments because of hasty, ill-conceived decisions?? (Especially when a modification is made to a manufacturer's design spec!) ? A few simple calculations/tests could be made by qualified people before costing users lots of time and effort. To paraphrase "the letter" drafted by students in Feb 2008, Is anyone accountable/responsible for these decisions? More than a year later, we really need to close the loop on these kinds of things.? Obviously "quality circles," "name tags," and "shadowing" didn't resolve the basic issues. From gunjim at stanford.edu Wed Apr 1 07:18:58 2009 From: gunjim at stanford.edu (Marika Gunji) Date: Wed, 1 Apr 2009 07:18:58 -0700 (PDT) Subject: Tylan1 reservation released today 12PM-4PM In-Reply-To: <342302849.653171238595480381.JavaMail.root@zm03.stanford.edu> Message-ID: <836940002.653191238595538139.JavaMail.root@zm03.stanford.edu> Would like to wait for tomorrow's qual and the non-uniformity problem to be solved. Thanks, Marika From nlatta at stanford.edu Thu Apr 23 14:34:53 2009 From: nlatta at stanford.edu (Nancy Latta) Date: Thu, 23 Apr 2009 14:34:53 -0700 Subject: Gas Calibration Message-ID: <49F0DEFD.4000604@stanford.edu> Folks, Starting Tuesday morning 28 April we will working on calibrating the O2/H2 gases. Historically, tylan1has yielded thinner oxide growth as compared to the other tylan oxidation furnaces. This calibration should be the furnace back into to line with the others. The work will continue through the reserved time on Tuesday and possible into other days. We may be reserving the other tylans for similar calibrations. What does this mean to you? You may see thicker oxides for times that you have characterized for wet oxidation. The thickness change might be 10% or more. The calibration work should have no affect on dry oxidations or anneals. Please refer to the coral comments for updates. Thanks for your cooperation, -Team Tylan