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

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 (H-2) plasma etch process is described that permits an alternative method to damascene technology. Cu thin films were etched in an H-2 plasma using inductively coupled plasma (ICP) reactors at temperatures between -150 degrees C and + 100 degrees C. This process achieves anisotropic Cu features (similar to 82 degrees) with a pure H-2 etch rate of similar to 13 nm/min. Both physical (ion bombardment) and chemical contributions (neutral species) are critical to the Cu etch process.