HF/H₂ O₂ etching for removal of damage layer on as-transferred Si layer formed by ion-cut process

When a 100 nm thick Si layer was transferred onto a bare Si wafer by the hydrogen-induced-layer-transfer process, a spongy damage layer with microvoids was formed on the transferred layer because of hydrogen blistering. The surface-to-volume ratio of the damage layer was greater than that of the layer where blistering did not occur. Therefore, the damage layer was selectively etched by an HF/ H₂ O₂ mixture and completely removed (the etching rates of Si at 70°C for the bulk layer and damage layer were 0.45 and 13.8 nm/min, respectively). Consequently, a smooth, damage-free Si layer (root-mean-square roughness=2.74 nm) was obtained.