The etching process of the high aspect ratio of Si deep trench is the key technology in MEMS field. Having used Oxford Plasmalabsystem100 ICP-180 etcher with SF6 and C4F8 as the etching gas, the influence on the deep Si etching process of Bosch under different ICP power, bias voltage, temperature, pressure and other parameters has been studied. The experimental result shows that under appropriate parameters, the high-aspect ratio of silicon deep trench is greater than 26:1, the sidewalls’ vertical degree is 89.9°, and the etching rate is greater than 2μm/min; the high aspect ratio of SOI deep trench is greater than 28:1, the sidewalls’ vertical degree is 89.7°, and the etching rate is greater than 2μm/min.
In recent years, deep reactive ion etching (DRIE) has become a key process in the fabrication of microelectromechanical systems (MEMS). By combining the etching power of reactive ion etching and sidewall passivation, it provides a precise anisotropic etch that can be used to create very deep etches as well as very narrow structures in silicon. The standard Bosch process for DRIE alternates between two steps: etching and passivation. This combination provides the ability to etch very deep, vertical structures.
In this article, silicon was etched with the Bosch process and cryogenic processes for patterning high-aspect-ratio features. The two leading techniques were compared. The influences of process parameters on the aspect ratio, etching rate and sidewall roughness of silicon were studied. Strong dependence of etch rate on loading was observed. The result showed that the etching rate rely on the process parameters. The aspect ratio of 23 was obtained and is able to be further improved.