Deep, vertical etching for GaAs using inductively coupled plasma/reactive ion etching

Deep etched structures in GaAs have many applications in optoelectronics and MEMS devices. These applications often require an anisotropic etch profile with smooth sidewalls as well as a high etch rate and high aspect ratio. Developing an etch process that demonstrates high selectivity for the etch mask is critical as etch times for deep grooves can be protracted due to the effect of RIE lag. In this work, the authors describe etching deep, vertical grooves in GaAs using Inductively Coupled Plasma/Reactive Ion Etching. The effects of RF power, pressure, and gas composition on mask selectivity, etch rate, and anisotropy are discussed. Using a SiO₂ etch mask and Cl₂ as the main etchant gas, grooves with a vertical sidewall and depths of >120 μm (aspect ratio of 9) have been achieved.