Bottom angle control mechanism and optimization of slanted gratings for optical applications

Slanted gratings serve as a crucial component in the optical waveguide couplers utilized in augmented virtual reality (AVR) devices. The flat bottom surface of slanted gratings ensures excellent diffraction efficiency of the couplers. However, achieving a flat bottom surface during the fabrication process poses challenges. This study presents a comprehensive investigation on the process control of the bottom angle using both simulation predictions based on available process parameters and experimental methods. The results obtained from the experimental procedures clearly demonstrate that the bottom angle is significantly influenced by the angular dependence of etching yield. Various ion incident energies and Ar/CHF3 gas components were employed to modulate the angular dependence of etching yield, thereby controlling the bottom angle in the reactive ion beam etching system. The effects of the ion incident energies and the flow ratios of the Ar/CHF3 gases on the bottom angle were thoroughly investigated. The findings of this study provide valuable insights for manufacturing slanted gratings and contribute to the advancement of AVR technology.