Hirotaka Shida

High Performance Photoresist Planarization Process by CMP with Resin Abrasive for Trench-First Cu/Low-k Dual Damascene Process

High performance photoresist planarization technology by chemical mechanical polishing (CMP) was developed for the trench-first Cu/low-k dual damascene (DD) process to reduce the focus error in the lithography process. To improve the planarity for the wide trench area, the planarization properties of alumina and resin-based slurries were investigated for different resist baking temperatures. Excellent planarity was obtained by high resist baking temperatures and using alumina slurry. However it became clear that the scratches caused by alumina particles were a critical issue for yield improvement. To improve the planarity and reduce the scratch density, the CMP process with a soft resin-based slurry at a low resist baking temperature was investigated. The addition of a nonionic water-soluble polymer to the resin particles was quite effective for planarity improvement, and the scratch level could be kept low by using soft resin abrasion. The resist planarization technology with a resin-based slurry was adapted to the trench-first DD process. The focus error was reduced and the process window in the lithography process was enhanced compared to the conventional process without a resist CMP, indicating that the resist planarization technology could be a strong tool for the 45 nm technology node and beyond.