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Technology Stocks : Advanced Micro Devices - Moderated (AMD) -- Ignore unavailable to you. Want to Upgrade?

To: Yousef who wrote (75588)	3/26/2002 9:47:55 AM
From: Elmer	Read Replies (2) \| Respond to of 275872

Thanks Yousef for your comments. I would add that the defect density number is measured at wafer sort and is primarily based on particulates. Assuming proper process control (not the 20 Sigma suggested by TWY<G>) the parametric failures shouldn't be a significant issue and aren't best screened at WS anyway. The single stuck@ fault model is the primary metric for screening at WS which is used for calculating defect density and best describes particulates, while any remaining parametric failures are caught at final test, hopefully at elevated temp. It's hard for people to grasp that 50% yield could be much better than 75% yield if the die sizes aren't the same. Eventually they'll realize what is meant by bad yields. EP

To: Yousef who wrote (75588)	3/26/2002 9:55:20 AM
From: Ali Chen	Read Replies (1) \| Respond to of 275872

Yousef, "The defect reduction methodologies of each company could be very different which could lead to very different results in reducing defects." Could be, would be, ... very definitive assessments <g> Didn't you tell us that both are buying their apple trees from the same place? Also, you forgot to turn in your homework: Message 17243360 Make it or break it, - Ali

To: Yousef who wrote (75588)	3/26/2002 10:49:11 AM
From: hmaly	Read Replies (1) \| Respond to of 275872

Yousef Re...These are generally process defects that are randomly distributed on the wafer (many times though there are patterns to the defects - like the edge has more than the center of the wafer). So defect density (DD) is the number of "killer" defects per square cm of wafer area. <<<<<<<< Please pardon my ignorance,your answer was quite clear, but I have a couple of follow up questions. Here you say that DD can have patterns, which intuitively seems to indicate that DD are caused by process problems,bad interconnects etc., however some have indicated that particulates are the main problem. Would these particulates necessary would be in the silicon material , or are they talking about contamination during processing, and would they be associated with patterns. From your description it would seem DD encompasses any type of killer defect. When you and Elmer state that AMD has DD problems, that only seems to eliminate bin speed and leakage problems as the source of AMD alledged problems. Can you define better what kind of DD problems you or Elmer are talking about, and why you believe that that is the problem. . Bad interconnects for example, or fuzzy imaging, bad DD methadology, etc. If we had something specific, it would be easier to say " You know what, Yousef said AMD had problems with yields because of imaging problems which leads blah,blah." Then we would have an idea of why you feel that DD is causing a bad yield problem for AMD.