Etch characteristics of magnetic tunnel junction stack using a high density plasma in a HBr/Ar gas

Abstract

Etch characteristics of magnetic tunnel junction (MTJ) stack masked with TiN thin films were investigated using an inductively coupled plasma reactive ion etching in HBr/Ar gas for the application of magnetic random access memory. The effect of HBr gas concentration on the etch profile of MTJ stacks was examined. As HBr gas concentration increased, the sidewall angles of etched patterns of MTJ stacks were slightly improved. The effect of etch parameters including coil rf power, dc-bias voltage, and gas pressure on the etch profile of MTJ stack was explored. At low coil rf power, low dc-bias voltage, and high gas pressure, the etching of MTJ stack displayed better etch profile. A high degree of anisotropic etching of MTJ stacks without redeposition was achieved using HBr/Ar gas at the optimized etch conditions.

Inductively Coupled Plasma Reactive Ion Etching of Magnetic Tunnel Junction Stacks in a CH3COOH/Ar Gas

“…[1][2][3][4] Generally, good etch profiles and fast etch rates of the MTJ stacks are achieved via formation of volatile etch byproducts that can be easily sputtered off. However, this particular gas chemistry has several drawbacks, such as the high toxicity of halogen gases, post etch corrosion and subsequent magnetization loss.…”

Influence of O2Gas on Etch Profile of Magnetic Tunnel Junction Stacks Etched in a CH4/O2/Ar Plasma

“…Some improvement on the etch rate was achieved but the etched sidewall angle of the patterns (hereafter called the etch slope) became slanted, which was unsatisfactory for high density MRAMs. [8][9][10][11][12][13][14] A CH 3 OH gas as a new etch gas to etch MTJ stacks was used and appeared to provide good etch profile of MTJ stacks. 15 Nevertheless, the etch profiles of the MTJ stacks with nanometer-sized patterns less than 100 nm were found to be inadequate, particularly for the nanometer-sized patterns with nanometer-sized spaces, and heavy redeposition on the etched sidewall of the MTJ stacks occurred.…”