Profile control in conductor metal wet etch with advanced photoresists

Abstract

Despite their long history in the electronics industry, copper metal layers remain important components as interconnection layers in IC fabrication due to their higher thermal and electrical conductivity as well as their higher electromigration resistance. Structuring the copper metal layer via wet chemical etching places demands on the photoresist mask, requiring resistance to harsh etch chemistry and good adhesion to the substrate to prevent delamination and defects. The photoresist formulation AZ® TD-2010 is a positive-tone, DNQ-based i-line photoresist that incorporates an additional surface-grafting component to deliver improved etch performance via enhanced photoresist adhesion on metal substrates. The in-situ priming of the photoresist formulation during the patterning process leads to a greater interfacial adhesion, resulting in steep sidewalls, with a greater than 20° increase in etch angle over formulations without adhesion promoter, while maintaining undercut depth and Cu CD. The AZ®TD-2010 photoresist can also be used at high thickness to cover topography steps formed from underlying layers, while also exhibiting high enough photospeed to maintain production throughput standards for IC manufacturing.