Su Min Hwang

Effect of O2 on etch characteristics of Co2MnSi thin films in CH4/O2/Ar gas mixture

Co2MnSi thin films masked with TiN films were etched in CH4/Ar and CH4/O2/Ar plasmas by inductively coupled plasma reactive ion etching. The etch rates decreased with increasing CH4 concentration in CH4/Ar gas, whereas the etch selectivity increased. The addition of O2 to CH4/Ar gas resulted in significant improvement in the etch profile but a decrease in the etch rates. Optical emission spectroscopy showed that a variety of COx, OH, and H2O species were formed in the CH4/O2/Ar plasma, acting a role as a passivation layer to protect the pattern sidewalls. X-ray photoelectron spectroscopy also confirmed the formation of metal oxides on the film surface, which could be sputtered off easily by Ar ion bombardment. A high degree of anisotropy of Co2MnSi films was obtained in the CH4/O2/Ar etch gas.

Etch characteristics of CoFeB thin films and magnetic tunnel junction stacks in a H 2 O/CH 3 OH plasma

Inductively coupled plasma reactive ion etching of CoFeB thin films and magnetic tunnel junction (MTJ) stacks with nanometer-sized patterns was performed using H2O/CH3OH gas mixture. As the CH3OH concentration in H2O/CH3OH increased, the etch rate of both the CoFeB films and MTJ stacks increased, but the etch selectivity decreased while the etch profiles of CoFeB films and MTJ stacks improved. Field emission transmission electron microscopy observation clearly revealed that the MTJ stacks etched at 75% CH3OH in H2O/CH3OH gas mixture showed a good etch profile without any redeposition and a high degree of anisotropy. These results indicate that there were some chemical reactions between CHX in H2O/CH3OH plasma and the films that comprise the MTJ stacks, such as CoFeB magnetic films. It was confirmed that H2O/CH3OH gas mixture could be a good etch gas in attaining a high etch rate and high degree of anisotropy in the etch profile.

Influence of oxygen on characteristics of Zn(O,S) thin films deposited by RF magnetron sputtering

Zn(O,S) thin films were successfully deposited by reactive sputtering using Ar and O2 gas mixtures at 473 K. X-ray diffraction patterns revealed that the well crystallized Zn(O,S) films were deposited with increasing oxygen concentration in O2/Ar, resulting in a shift of the Zn peak of 28.5° to a higher angle, closer to the ZnO peak of 34.4°. Zn(O,S) films were composed of grains agglomerated from small particles, which grew gradually with increasing oxygen concentration. The depth profiles and energy dispersive spectroscopy results of the films indicated that the O/(O+S) ratio increased from 0.04 to 0.81, and all Zn(O,S) films were Zn rich with uniform concentrations of each component. X-ray photoelectron spectroscopy revealed that, as the oxygen concentration increased to 2%, the ZnS films were transformed to Zn(O,S) films via substitution of oxygen for sulfur.