2.0mil Copper Wire - Tail Short Improvement and Robustness Study

Copper wire bonding technology has been introduced to the semiconductor manufacturing processes several years ago. However, copper interconnection technology still pose a challenge to most of the semiconductor players as the intrinsic hardness of copper material does come with technical challenges. With the spiraling of gold prices globally, the copper wire conversion and implementation has become even more attractive to maintain cost competitiveness and profitability. Fairchild Semiconductor have qualified S08 power discrete devices using 2.0 mil copper wire more than 2 years ago and have been running copper wire in production mode while continuing proliferation efforts, process research and development. This paper discussed about the tail short improvement and robustness study of 2.0 mil copper wire bonding. It covers the background and phenomenon of the tail short, investigations which include internal (machine setup variation, process window & etc) and external (shipping, handling, and storage conditions etc.) factors that could lead to the variation, failure analysis of copper wire material, experiment, and lastly, the improvement that yielded the solution. The analysis tool/equipment used throughout the investigation includes shock Log (recorder to check for the impact, temperature and humidity of copper wire during the product transportation), SEM (Scanning Electron Microscope), FIB (Focused Ion Beam), tensile tester, micro harness tester and other common analysis equipments. The tail short improvement study has been challenging and with the studies conducted in collaboration with the wire supplier, this yielded a favorable outcome resulting to a more robust copper wire bonding process.