Atomic layer etching of BeO using BCl3/Ar for the interface passivation layer of III-V MOS devices

BeO was investigated as the interface passivation layer (IPL) between a high-k dielectric and a III-V compound semiconductor substrate in metal-oxide-semiconductor (MOS) devices. One of the critical issues facing the fabrication of next generation MOS devices is the minimization of damage to the III-V semiconductor substrate during the etching of the thin IPL. In this study, atomic layer etching (ALET) was investigated for etching of BeO as the IPL on a GaAs substrate to control the etch depth precisely and to minimize the damage to the III-V semiconductor substrate. By using ALET to etch BeO, which uses BCl"3 as the adsorption gas for the formation of chloride compounds (Be-Cl and BCl-O) and Ar as the desorption gas for the removal of the chloride compounds, a self-limited, one-monolayer etch rate of about 0.75A/cycle was achieved with no increase of surface roughness and without change of surface composition. Moreover, under the BeO ALET conditions, which are able to precisely stop etching over the GaAs substrate after removing BeO, the exposed GaAs substrate showed surface composition and surface roughness similar to those of the as-received GaAs substrate.