Investigation of TaN as the wet etch stop layer for HKMG-last integration in the 22 nm and beyond nodes CMOS technology

Abstract

In this work, tantalum nitride (TaN) was chosen as the wet etch stop layer (WESL) for its application in the 22 nm and beyond nodes CMOS technology. TaN WESL prevents the attacking of titanium nitride (TiN)/hafnium dioxide (HfO2) stack covering n-channel MOS (nMOS) regions from selectively stripping work function metals of p-channel MOS (pMOS) gate, i.e. TiN & titanium (Ti), by ammonia hydrogen peroxide mixture (APM) solution. In terms of etching selectivity to TiN & Ti, gate filling capability and work function tuning for both nMOS and pMOS, the properties of TaN films prepared by different methods such as physical vapor deposition (PVD) and atomic layer deposition (ALD) were investigated systematically.