Electron cyclotron resonance plasma etching of materials for magneto-resistive random access memory applications

Abstract

Dry etching of multilayer magnetic thin film materials is necessary for the development of sensitive magnetic field sensors and memory devices. The use of high ion density electron cyclotron resonance (ECR) plasma etching for NiFe, NiFeCo, TaN, and CrSi in SF6/Ar, CH4/H2/Ar, and Cl2/Ar plasmas was investigated as a function of microwave source power, rf chuck power, and process pressure. All of the plasma chemistries are found to provide some enhancement in etch rates relative to pure Ar ion milling, while Cl2/Ar provided the fastest etch rate for all four materials. Typical etch rates of 3000A/min were found at high microwave source power. Etch rates of these metals were found to increase with rf chuck power and microwave source power, but to decrease with increasing pressure in SF6/Ar, CH4/H2/Ar, and Cl2/Ar. A significant issue with Cl2/Ar is that it produces significant metal-chlorine surface residues that lead to post-etch corrosion problems in NiFe and NiFeCo. However, the concentration of these residues may be significantly reduced by in-situ H2 or O2 plasma cleaning prior to removal of the samples from the etch reactor.