CMOS Backside Deprocessing With TMAH / IPA as a Sample Preparation Procedure for Failure Analysis

Abstract

This paper is about a sample preparation technique that is based on a previous research publication1. The technique was initially used for the investigation of salicide formation for CMOS process development. The initial results were very good and proved to be helpful with root cause failure analysis. Once the technique proved to be a viable failure analysis (FA) tool, a research team was formed to continue the development. This paper is written in conjunction with this team. The team is presently focused on developing a repeatable and reliable methodology of deprocessing CMOS devices from the backside. The team is also developing a methodology for post deprocessing analysis once the backside silicon is removed. The research that is presented here focuses on packaged as well as unpackaged devices. Etch rates and selectivity of tetramethylammoniumhydroxide (TMAH) is investigated along with temperature dependencies. Package material and chemical interference issues were discovered and remedied with special preparation techniques. Post deprocessing analysis is considered and many ideas are proposed as part of future research.