High Heat Proofing Nano-Layered Film Cu Wiring Using Crystal Grain Growth Control

概要

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Cu is gaining a lot of attention as the main wiring material for next generation devices. However, Cu oxidizes in high-temperature heat treatments. For heat-proofing considerations, a Cr/Cu/Cr system is widely used. Currently, the required Cr layer is too thick and Cr is environmentally problematic. Therefore, we focused on the stable oxide, SnO2, and were able to increase heat proofing by covering Cr/Cu/Cr with SnO2. This was able to tolerate a heat treatment of 873 K for 1800 s in air. 873 K is the highest temperature in the PDP manufacturing process, which has an especially severe heat treatment for various devices. However, some oxidization along the grain boundary was observed. In order to further increase reliability, we then investigated the elucidation of an oxidation mechanism. We show clearly that Cu crystal grain growth is the most important factor for the oxidation. Based on this fact, we tried to control grain growth and improve heat proofing by inserting one or more Cr layers into the Cu layer. The result looks like a mille-feuille or Napoleon pastry. As a result, grain growth was controlled and heat proofing greatly improved.
The Japan Institute of Electronics Packagingの論文