A new commixing sample preparation technology for the interface analysis of second wire bonding with TEM

The strength of wire bonds will directly affect device reliability, so the study of the microstructure at the bonding interface and relative issues would have its necessity. Comparing to other micro-region analysis methods, such as SEM, XPS, AES, but the TEM technique is a conformable analytical tool due to its great advantage in the spatial analytical precision and resolution aspects for the bonding interface micro-analysis, but its sample preparation is a big challenge. This paper was mainly about a new commixing sample preparation technology for TEM analysis of the interface of Second wire bonding in wire bonding process. Conventional sample preparation method in forms of mechanical grinding with ion milling would be time-consuming, hard to be localized, and whereafter with a lower success rate, while advanced FIB micro-machining technology only could cut and form the shallower feature in the sample, or it also would be time-consuming and reduce success rate. The commixing sample preparation process that we used had maintained the advantages of the both methods while avoiding the shortcomings of the both two, its feature shows: localization with high precision (it could localize the bonding interface area accurately); obtaining a thinner sample (about 80nm in thickness) with a larger sampling area(~3um); getting a higher success rate of sample preparation (approaching 100%), relatively less time-consuming (with only about 2 FIB working hours). This paper will describe the whole procedures of commixing sample preparation technology and also show the TEM analytical results of a real sample which adopt this technology. The microstructure, crystalline, and composition distribution in micro-region at the second wire bonding interface were clearly and accurately displayed.