Development of Developer-Soluble Gap Fill Materials for Planarization in Via-First Dual Damascene Process

Abstract

Gap fill materials and planar-type bottom antireflective coating are needed for patterning metal trenches in the via-first dual damascene process. We have already reported on thermal cross-link gap fill materials and bottom antireflective coating as planarizing layers under a resist that can be spin-coated and etched faster than resists. In this study, developer-soluble gap fill materials were optimized in order to obtain excellent planarization, simplify the process, and increase wafer throughput. The developer-soluble gap fill materials using poly(4-hydroxystyrene) derivatives developed by an approach of the via-first dual damascene process was obtained by optimizing the concentration of the phenol group with solubility in the alkaline developer (0.26 N tetramethylammonium hydroxide, TMAH) and by thermal cross-link reaction. In addition to a superior via-filling performance, developer-soluble gap fill materials using poly(4-hydroxystyrene) derivatives showed a wide process window of prebake temperature, the controllable dissolution rate for the etch-back process, and a good CF4 etch rate of 1.4 times higher than that of a resist for etching the substrate. These results were attributed to the polymer structures of poly(4-hydroxystyrene) derivatives. Both dry plasma cleaning and wet developer cleaning can be used to remove residual gap fill materials after processing. This novel approach using developer-soluble gap fill materials as a new type of sacrificial material in an advanced lithography process makes this solution convenient for planarizing surfaces and is economically favorable owing to high throughput.