Atomic layer etching of Al₂O₃ using BCl ₃/Ar for the interface passivation layer of III-V MOS devices

The atomic layer etching (ALET) of Al₂O₃ has been studied for possible application in precise etch control and low damage etching of the Al₂O₃ layer for use as the interface passivation layer (IPL) between the high-k dielectric and the III-V compound semiconductors. Under the ALET condition, about 1 A°/cycle of Al₂O₃ corresponding to one monolayer per etch cycle and surface roughness similar to that of the reference, regardless of the number of etch cycles, were obtained. Therefore, etch depth could be controlled with atomic scale precision. In addition, during the ALET, the stoichiometry of Al₂O₃ and the Al/O ratio were maintained the same as those of the reference. Therefore, it is believed that the ALET of Al₂O₃ can reduce the plasma induced damage at the edge of an IPL because it can decrease the sidewall leakage by maintaining the stoichiometry of the sidewall Al₂O ₃ surface, in addition to, precisely controlling the etch depth and minimizing the amount of substrate recess.