From mtang at snf.stanford.edu Wed Sep 5 14:24:17 2001 From: mtang at snf.stanford.edu (Mary Tang) Date: Wed, 05 Sep 2001 14:24:17 -0700 Subject: LTO Status Message-ID: <3B969801.D912DFB2@snf.stanford.edu> Hello Tylan users -- As you may very well know, LTO has had a spate of particle problems lately. The initial particle problem which put the system down a few weeks ago has been resolved, so is not the issue now. This latest series of particle problems has a different signature. This is what we think we know so far. It appears that the particles are actually pieces of film flaking off the tube and quartzware. The feeling is that the flaking/peeling is a film adhesion or film stress issue. This seems to coincide with a more frequent use of thick films deposited at 450 C, which is a higher temp than most other processes here. In fact, just before this last instance, one user deposited eleven (?!?) microns of LTO at 450 C. Before the previous instance, a user did two consecutive depositions at 450 C of three microns each. Gladys will be checking into the logs to see if thick depositions at 450 C do, indeed, correlate with peeling/flaking. If any of you has information on the film parameters, particularly film stress, for this 450 C process, PLEASE contact Gladys. Our alternative theory is that our process has drifted off the hairy edge (or rather, peeling edge.) Jim McVittie, Ray, and Mike, did some mass flow controller calibration checks which show that our gas flows are considerably off -- it isn't certain whether they have always been off by this amount or if we've slowly drifted this way over time. Gladys and Nancy are in the process of running tests using programs with corrected flows, which will be compared to current values. The tube is otherwise functional (good uniformity, good deposition thickness). The maintenance folk will be doing a tube pull and clean, but it is not certain when they can do this (tylan nitride is supposed to go tomorrow.) Until then, if you do not care about particles, the tube is usable. When the tube is changed and the process is brought back up, we are going to ask those of you who wish to deposit LTO at 450 to talk with Gladys before doing so. This is not to say labmembers cannot run thick 450 C LTO, but I'd certainly feel better (and I'm sure other LTO users as well) if we knew for certain this was not going to be a problem. To those of you who run this process: we would appreciate it if you could provide information about this film and maybe even help us design and run experiiments (if necessary) to characterize this process. Just as a note -- there is a policy limiting deposition thicknesses in a single run to 3 microns. Thicker runs (such as the 11 micron dep described above) go against stated policy. As there appears to be a general need for thicker films, we will probably have to revisit this policy -- those of you who need thick films, please work with us on this. In summary: 1. We think that the particle problem may be caused by an increase in the number of thick 450 C depositions. Gladys and Nancy are collecting data. 2. The tube will be pulled & cleaned, but timing is uncertain because of other furnace issues. Until then, LTO is pretty junky, but OK to use, if you don't care about particles. 3. When LTO comes back up, please DO NOT RUNS 450 C thick depositions (how thick is thick? I don't know, but will arbitrarily say "one micron" for now.) Help us get more info on this before we risk prematurely junking up another tube. Mary -- Mary X. Tang, Ph.D. National Nanofabrication Users' Network Stanford Nanofabrication Facility CIS Room 136, Mail Code 4070 Stanford, CA 94305 (650)723-9980 mtang at snf.stanford.edu From latta at snf.stanford.edu Thu Sep 13 17:39:07 2001 From: latta at snf.stanford.edu (Nancy Latta) Date: Thu, 13 Sep 2001 17:39:07 -0700 (PDT) Subject: LTO back! Message-ID: Folks, The uniformity tests are done. Not great, but good enough to release. Wafer to wafer within a boat = ~10% Within a wafer = ~10% Average thickness for all eight wafers can be found on the web in equipment archives. Nancy From beckwith at snf.stanford.edu Tue Sep 18 13:51:44 2001 From: beckwith at snf.stanford.edu (Sharleen Beckwith) Date: Tue, 18 Sep 2001 13:51:44 -0700 Subject: Problem tylanbpsg 2001-09-18 12:49:21: moving cable rubbing against metal panel Message-ID: >the boat doesn't want to come out or go in on its own due to the >cable rubbing against metal panel...but boat can still be manuevered >manually This is obviously not good! The potential for metal flakes are high when the cable is rubbing against metal.