Subtractive Etching of Cu with Hydrogen-Based Plasmas

Abstract

Due to the inability to form volatile etch products at temperatures less than 180 oC, the damascene process has been the prevailing patterning technology for copper. A simple, hydrogen (H2) plasma-based, low temperature etch process was developed to allow an alternative method to damascene technology. Cu thin films were etched by a H2 plasma in an inductively coupled plasma (ICP) reactor at temperatures below room temperature (10 oC). This process achieved anisotropic Cu features and an etch rate of ~13 nm/min. Ion bombardment was a contributor to Cu removal, since the etch rates were essentially proportional to the platen power with a constant coil power. However, lower etch rates of Cu were observed in an Ar plasma than in the H2 plasma, despite the fact that Ar is a more efficient sputter gas. Based on Cu etch rates and patterning results, the etch process involve both chemical and physical characteristics.