Ion beam and chemically assisted ion beam etching of InP with anisotropic and smooth surfaces

In this paper, we investigate ion beam etching (IBE) and chemically assisted ion beam etching (CAIBE) of InP. While argon (Ar) alone is used for the IBE process, the CAIBE is carried out by using Ar/H₂/CH₄. The realization of CAIBE in an Ar/H₂ atmosphere is also achieved for the first time. The evolution of the surface roughness and morphology is presented comparatively by varying the acceleration voltage (V_acc), the discharge current (I_dis) and the ion incidence angle. The etch rate of the InP structures is studied as a function of I_dis and V_acc. The variation of the etch rate against the ion incidence angle is also investigated experimentally. A maximum etch rate of 70 nm min^-1 is observed for an acceleration voltage of 2 kV and a discharge current of 45 mA at a 30° ion incidence angle. It is also found that a drastic improvement of the surface roughness is observed for CAIBE using Ar/H₂ chemistry. In addition, the anisotropy of InP samples is also presented for two different masks, Al₂O₃ and titanium (Ti) for the CAIBE mode. The most anisotropic structure of 83° is performed using the Ti mask. Finally, the etched surfaces are quantified using the atomic force microscopy technique where the lowest root-mean-square roughness of 4.3 nm is found when using only Ar/H₂ gases.