Subtractive Etching of Cu at Low Temperature in Hydrogen-Based Plasmas

Abstract

Thin film patterning in integrated circuit processing has traditionally been performed by subtractive processes. However, over the past 25 years, the inability to plasma etch copper (Cu) interconnect patterns has led to patterning of Cu by an additive process: the damascene approach. In the current work, a simple subtractive, low temperature hydrogen (H2) plasma etch process is described that permits an alternative method to damascene technology. Cu thin films were etched in an H2 plasma using inductively coupled plasma (ICP) reactors at temperatures between -150 oC and +100 oC. This process achieves anisotropic Cu features (~82o) with a pure H2 etch rate of ~13 nm/min. Both physical (ion bombardment) and chemical contributions (neutral species) are critical to the Cu etch process.