Quantitative model of sidewall redeposition and cleaning in ion beam etching for semiconductor device fabrication

Ion beam etching (IBE) is a widely used patterning technique in semiconductor device fabrication, particularly for devices sensitive to plasma-induced chemical contamination. However, a key challenge in the IBE process is the sputtering of target materials and their subsequent redeposition on the sidewalls of patterned structures. In this study, a quantitative model of sidewall redeposition and cleaning in the IBE process was proposed. The sputtered atoms from the front surface and the residual atoms removed from the sidewall were quantified, and the residual coverage on the sidewall was estimated under steady-state conditions. Based on this model, the degree of sidewall redeposition in a tilted-angle IBE process was quantitatively estimated from the ratio of the surface to the sidewall sputter yield, the incident ion angle, the redeposition fraction, and the pattern aspect ratio. These factors were further investigated, revealing that the apparently intricate sidewall redeposition is governed by only two key parameters: the incident ion angle and the pattern aspect ratio. A higher incident angle and a higher aspect ratio both lead to reduced sidewall redeposition. This model provides a practical and physically grounded tool for minimizing sidewall redeposition and optimizing sidewall cleaning in IBE processes, which is critical for advanced semiconductor device fabrication.