Enhancement of etching properties using pulsed inductively coupled plasma for high aspect ratio TiO₂ pillars in metalens fabrication

Metalens is one of the metamaterial applications, and it could be used in various ways, such as high-resolution imaging, phase gradient imaging, etc. TiO₂, known for its high refractive index and low optical loss in the visible wavelength range, is a promising candidate for metalens. This study investigated the effect of various pulsed plasma on the etching characteristics of high aspect ratio TiO₂ for high selective/uniform fabrication of planar metalenses. TiO₂ pillars of different sizes were etched using continuous wave (CW), bias pulsing, synchronous pulsing, and asynchronous pulsing. The results showed that while the etch rate decreased in the sequence of CW, synchronous, and asynchronous pulsing, the etch selectivity and ARDE effect improved in the same sequence. This finding suggests that asynchronous pulsed plasma techniques provide superior control over etch selectivity and ARDE. The study contributes to advancing plasma etching technology to produce high-precision, high-performance optical components such as metalenses.