Ascertaining of Copper Contamination from Various Sources in the Wafer Fab by Using VPD-TXRF Methodology

Abstract

Preventing and monitoring of Cu cross contamination become critical for the semiconductor industries since most of them are converting to mass-producing chips with copper (Cu), rather than aluminium (Al) as an interconnect element. Cu is a superior conductor of electricity, making it possible to shrink the electronic devices while further increasing performance. Presently, most of the Cu contamination emphasis on a wafer surface only using various methodologies. This in turn requires the need to improve the performance of analytical tool and to develop a new analytical measurement methodology for evaluating the levels of Cu contamination that might come from many sources in a wafer fab. In order to solve this problem, a new assessment methodology of using vapor phase decomposition and total X-ray fluorescence (VPD-TXRF) was introduced with the aim of establishing a trace elemental analysis. Currently, VPD-TXRF is mainly used as an analyzing tool to monitor Cu contamination on a wafer surface. However in this research, the same methodology is proof to be useful for measuring traces of Cu element induced from the other sources of contamination which is not necessarily from a wafer itself but also from the other sources in the whole fab. Gauge repeatability and reproducibility (GR&R) including component of variations study was applied in this research and the finding shows a positive results. A standard procedure and comparable sample also has been used which is ICPMS analyzing in purpose to set up a correlation with VPD-TXRF measurement data. Then this study aid to develop a valid procedure for Cu traces analysis, which served as a reference procedure to measure, monitor and control a Cu contamination. The final results validate this methodology as a distinguish method to measure a Cu contamination that come from many sources. Beside that, this methodology offers a cost saving since it uses a reclaim wafer as a sample preparation. Thus, this methodology is a key and can be used as process knowledge in accelerating advanced Cu interconnects development.