Henry A. Bonges

Radial yield variations in semiconductor wafers

Detailed examination of yield data from several different products in two different technologies and two different wafer sizes has shown a pronounced radial dependence. In all cases, the yield profile has a distinct knee starting at about 10 mm from the wafer periphery, dropping steeply within the final 5 mm. The similarity in yield profile near the periphery across all the products examined suggests that edge yield loss is of a gross nature and is not caused by design, technology, wafer size, or random defects.

SOI charging prevention: chip-level net tracing and diode protection

In this paper we show that the SOI FET is conductive during processing, and also that a FET shunted across the gate and source/drain of another transistor does in fact protect that device against charging damage.

Radial Dependency of Reliability Defects on Silicon Wafers

A study analyzing reliability defects with respect to their original wafer location has recently been completed at IBM Burlington. The results of this study, which showed such defects to have a high radial dependency, are discussed herein. Equally important to these results is the process by which the results were obtained, a process termed Laser Chip ID. This process of permanently identifying chips by using a laser was found to be extremely useful and is also discussed in this paper.