Effect of Ultra Soft CMP Processing Parameters on Topography of HgCdTe Wafer Surfaces

In this study, ultra soft chemical mechanical planarization (CMP) of mercury cadmium telluride (MCT) surface using hydrogen peroxide (H2O2), silica (SiO2) and SDS containing slurry has been demonstrated. Effect of CMP processing parameters, such as platen velocity, the concentration of the oxidiser and abrasive, slurry pH and surfactant types on surface quality (roughness) has been studied. It has been found that the addition of an anionic surfactant (SDS) in the slurry solution effectively assisted in improving the surface quality as compared to the surfactant free counterpart. The CMP processed MCT surfaces have shown significant improvement in the root-mean-square (rms) surface roughness (Rq) and local/global surface planarity as compared to the as-grown MCT surfaces, which had very rough and wavy surface topography. The best rms surface roughness (Rq) of ∼1.6 nm over a scan area of 10 × 10 μm2 has been obtained under optimized slurry chemistry and processing parameters. This Rq value was found to be almost similar with increasing scan area size up to 481 × 361 μm2, an indication of excellent global surface planarity by the ultra soft CMP process.