From latta at snf.stanford.edu Fri Jan 12 10:47:54 2001 From: latta at snf.stanford.edu (Nancy Latta) Date: Fri, 12 Jan 2001 10:47:54 -0800 (PST) Subject: Nitride etch rates? Message-ID: Folks, I am trying to gather up information on nitride etch rates in the oxide and Si chambers. Can you pass me anything you have in you notes which might be helpful? I'll be happy to print the info up for all to use. Thanks, Nancy From booth at snf.stanford.edu Tue Jan 23 11:19:20 2001 From: booth at snf.stanford.edu (Len Booth) Date: Tue, 23 Jan 2001 11:19:20 -0800 Subject: The P5000 is available for use. Message-ID: <3A6DD938.6D10C323@snf.stanford.edu> From mcvittie at cis.Stanford.EDU Thu Jan 25 18:02:39 2001 From: mcvittie at cis.Stanford.EDU (Jim McVittie) Date: Thu, 25 Jan 2001 18:02:39 -0800 (PST) Subject: No More Dummy Wafers to be Provided Message-ID: Lampoly and P5000etch Users, Up until now we have provided dummy wafers for Lam and P5000 users to season the plasma etch chambers before use. Except for the AMT hexode system, we do not provide such wafers for the other etchers. This has become has burden on the staff. Since the use of these dummies is a user issue and does not affect these etchers for the most part, we have decided to let the users provide their own dummies. Below are some guidelines to help with you condition or season an etch chamber before use. Why is the running of dummies needed? In seasoning an etch chamber, one is trying to get the coating on the chamber walls to be same as what occurs during the etching of the actual device wafers. The reason for doing this is that your etch results depend on the reactive species concentrations in the plasma. These reactive species depend not only on the source gases and other process settings but also on the wall reactions which depend on what is on the surface of the walls. For most etch processes a equilibrium surface composition develops on the chamber walls after a few minutes. The dummies are used to let the chamber get to this equilibrium condition before the real etching begins. Hopefully, the result is that each of your device wafers etch same this time as the time before. What type of dummies are needed? Dummies need to reflect what the real device wafers look like at the particular etch step. If one is etching a typical poly-Si wafer where the resist coverage is about 50 %, one should use alternating resist and bare Si wafers for the dummies. If one is etching wafers that are mainly bare Si, then of course one should use just use bare Si dummies. In the case of oxide contact etching where the surface of the device wafers are usually > 90% resist, resist dummies should be used. Al etching is similar to poly-Si in that the resist coverage is usual around 50% so alternating resist and bare Al wafers are the best dummies. How many dummies should be run? The number of dummies depends on how long it has been since the last time the chamber was conditioned, if a different process has been run in the chamber, if the chamber has been open to air, or if the chamber has be giving a plasma clean. In industry, up to 25 dummies wafers can be run before starting to run production. For our use where our chambers tend to be dedicated, I typically recommend running 4 dummies each for 60 seconds. If your run is not critical, running no dummies may work ok for you. How many times can I reuse a dummy? This depends on the process. Obviously, a resist wafer with no resist left needs to be re-coated before further use. For bare Si wafers, the limits are black silicon formation and wafer thickness. Black silicon is when there is lots of micro-masking on the surface and the surface looks black. The problem with black silicon is that the wafer can start giving off particles. Wafer thickness is an issue because thinned wafer can break during clamping. I recommend replacing Si dummies after they have loss 1/3 of their thickness. Jim -------------------------------------------------------------- James P. McVittie Senior Research Scientist Allen Center for Integrated Systems jmcvittie at stanford.edu Stanford University Tel: (650) 725-3640 Rm. 336, 330 Serra Mall Fax: (650) 723-4659 Stanford, CA 94305-4075