Terahertz metal bi-grating fabrication using ultra-thick photoresist process

As a key part of terahertz vacuum electronic device, metal grating cant be fabricated using traditional methods due to its tiny dimension. The photoetching process of metal bi-grating for radiation source at some terahertz band was presented. The influence of the procedure (including substrate preparation, spin-coating, pre-bake, exposure, post-bake and developing) on photoetching was analyzed experimentally. The problems such as film drop and crack, films combination and the photoresist remaining at gaps which were caused by thick film and high aspect ratio, were solved by the optimizing the process parameters. Finally, a good film microstructure with steep side wall and smooth surface was achieved, with a thickness of 700 m and an aspect ratio of 14. The work presented in this paper provides a technological guide to the similarly related project.