Deep Reactive-Ion Etching Process Development and Mask Selection
Abstract
Deep reactive-ion etching is an important process in the fabrication of microelectromechanical system devices, through-silicon vias, and dynamic random-access memory capacitors, among other devices and components. High-quality etching is a crucial step in device fabrication, where the etch quality is determined by three properties: aspect ratio (ratio of depth of etched feature to width of etched feature), selectivity (ratio of desired material’s etch rate to etch mask material’s etch rate), and sidewall profile (angle relative to feature bottom and sidewall roughness). A cryogenic-temperature deep reactive-ion etching process is developed to obtain 90°, smooth sidewalls and maximize the selectivity and aspect ratio through the optimization of oxygen gas flow rate, radio frequency power, and inductively-coupled plasma power on a (111) silicon substrate. The aspect-ratio-dependent etching effect and its impact on etch rate is also examined. Additionally, etch mask behaviors of selectivity and tendency to crack are characterized for 100 nm electron-beam evaporated chromium, 500 nm thermally-grown silicon dioxide, and 1.45 µm post-develop-baked AZ 5214 E-IR photoresist. The experimental results provide insight on how to adjust the etching process according to the specific device application and which material and film thickness is best to use as an etch mask.
Citation
Morse, Ethan (2020). Deep Reactive-Ion Etching Process Development and Mask Selection. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /188382.