C015 YIELD IMPROVEMENT

Abstract

In the wafer fab environment, defect density or what we used to call D0, is a very important index. It is the one that drives the yield performance. Therefore, to improve yield, we need to reduce the defect density. Defect is defined as imperfect film formation or pattern definition due to incorrect process conditions, external particles, or equipment contamination. They can be in random, clustered, or repeating. However, they are not always catastrophic. It is therefore divided into two categories, killing and not killing. Killer defects, such as pattern fail, are surely catastrophic and affecting the yield. However, presence of small particles in an open area most of the time would not really hurt the chip. Thus, it is important in identification of the types of the defects. In this thesis, defect density of 0.15 micron technology devices in SSMC was analyzed. Due to the novelty in the fab, this technology still has a high defect count which mostly lies in the front end processes. Therefore, since reducing defect count would increase the yield as said earlier, it is our objective to localize the source of defects and identify the root cause of the defects. From there, corrective action would then be taken to reduce the defect count.