Mask Design and Micro-Fabrication Technology Development for Transmission Lines in THz

Abstract

Transmission lines play an important role in many different applications in our daily life. Due to high data rate requirement in many areas, e.g. wireless communication, radio astronomy, etc., there is a growing interest in high frequency transmission line, especially in THz. The key issues are low conductor loss, low cost and easy fabrication. A novel design of silicon THz transmission lines, consisting of horn-shaped antenna and 60° bended band, can reduce serious conductor loss, which usually occurs in metal transmission lines, and have the features of low cost and easy fabrication. Three levels of mask were designed for forming the transmission lines in silicon. The main technologies used in the fabrication processes are optical lithography, thin film deposition, and wet etching. 50 μm thickness Si front side transmission line structure were formed using the 1st level mask. These deep Si structures were etched with SiO2 as etch mask. Obtuse angle and oblique sidewalls were observed, due to undercut below etch mask and <111> crystal orientation respectively. Dry etching is an alternative technology to address these two problems. 350 μm thickness Si backside transmission line structure were formed using the 2nd level mask. There deep Si structures were etched with B3 as etch mask. Possible fabrication technologies for 3rd level masks and improvement for structure were also discussed.