ABSTRACT
The amorphous carbon layer (ACL), used as the hardmask for the etching of nanoscale semi-conductor materials, was etched using O2/CHF3 in addition to O2/N2 using pulsed dual-frequency capacitively coupled plasmas, and the effects of source power pulsing for different gas combinations on the characteristics of the plasmas and ACL etching were investigated. As the etch mask for ACL, a patterned SiON layer was used. The etch rates of ACL were decreased with the decrease of pulse duty percentage for both O2/N2 and O2/CHF3 due to decrease of the reactive radicals, such as F and O, with decreasing pulse duty percentage. In addition, at the same pulse duty percentage, the etch selectivity of ACL/SiON with O2/CHF3 was also significantly lower than that with O2/N2. However, the etch profiles of ACL with O2/CHF3 was more anisotropic and the etch profiles were further improved with decreasing the pulse duty percentage than those of ACL with O2/N2. The improved anisotropic etch profiles of ACL with decreasing pulse duty percentage for O2/CHF3 were believed to be related to the formation of a more effective passivation layer, such as a thick fluorocarbon layer, on the sidewall of the ACL during the etching with O2/CHF3, compared to the weak C-N passivation layer formed on the sidewall of ACL when using O2/N2.
ABSTRACT
The etch characteristics of magnetic tunneling junction (MTJ) related materials such as CoFeB, MgO, FePt, Ru, and W as hard mask have been investigated as functions of rf pulse biasing, substrate heating, and CH4/N2O gas combination in an inductively coupled plasma system. When CH4/N2O gas ratio was varied, at CH4/N2O gas ratio of 2:1, not only the highest etch rates but also the highest etch selectivity over W could be obtained. By increasing the substrate temperature, the linear increase of both the etch rates of MTJ materials and the etch selectivity over W could be obtained. The use of the rf pulse biasing improved the etch selectivity of the MTJ materials over hard mask such as W further. The surface roughness and residual thickness remaining on the etched surface of the CoFeB were also decreased by using rf pulse biasing and with the decrease of rf duty percentage. The improvement of etch characteristics by substrate heating and rf pulse biasing was possibly related to the formation of more stable and volatile etch compounds and the removal of chemically reacted compounds more easily on the etched CoFeB surface. Highly selective etching of MTJ materials over the hard mask could be obtained by using the rf pulse biasing of 30% of duty ratio and by increasing the substrate temperature to 200 degrees C in the CH4/N2O (2:1) plasmas.
ABSTRACT
The magnetic tunnel junction (MTJ)-related materials such as CoFeB, CoPt, MgO, and Ru, and W were etched using CH3OH in a pulse-biased inductively coupled plasma system and the effect of bias pulsing (100% 30% duty percentage) on the etch characteristics of the MTJ-related materials was investigated at the substrate temperature of 200 degrees C. The etch selectivity of MTJ-related materials over W was improved by using pulse-biasing possibly due to the formation of more stable and volatile etch products during the pulse-off time and the removal of the compounds more easily on the etched CoFeB surface during the pulse-on time. X-ray photoelectron spectroscopy also showed that the use of lower duty percentage decreases the residue thickness remaining on the etched MTJ materials indirectly indicated the higher volatility of the etch products by the bias pulsing. The etching of nano-patterned CoFeB masked with W also showed more anisotropic etch profile by pulse-biasing probably due to the increased the etch selectivity of CoFeB over W and the decreased redeposition of etch products on the sidewall of the CoFeB features. The most anisotropic CoFeB etch profiles could be observed by using CH3OH gas in the pulse biasing of 30% duty ratio.
