Failure Analysis of E-Test Failure and Yield Enhancement in Wafer Fabrication

摘要

In wafer fabrication, some wafers were reported with E-Test failure and low yield issue. To understand the details, failure analysis was performed on a low yield wafer. Dash etch was used to identify the root cause. The wafer was first delayered to bare silicon using HF deprocessing, and was then subjected to Dash etch. Some experiments were carried out for the characterization of the etch time in HF and Dash etch solutions. After Dash etch, optical inspection results showed that there was no P~+ dopant on the low yield wafer at both the test pattern and die area. Based on failure analysis & fab investigation results, it was concluded that the low yield issue was due to missing P~+ implantation. In this paper, we will report the details of failure analysis & fab investigation results.