The influence of He addition on Cl-etching procedure for Si-nanoscale structure fabrication using reactive ion etching system

Chlorine-based plasma have been often used to etch several semiconducting materials including Si and III–V materials. The chlorine plasma etching is well suited for fabrication of Si-nanoscale structures due to its good control of undercutting and etch profile. Due to some drawbacks such as trenches and damages on the etch mask from physical ion assisted etching, the Cl2/He gas mixture using a conventional reactive ion etching system was utilized and the optimization procedures were performed. Therefore, the influence of the He flow rate was examined. As the He flow increases over 30% of the total inlet gas flow, the plasma state become stable and the etch rate starts to increase. For high flow rate over 60%, the relationship between the etch depth and the etch time was observed to be nearly linear. In addition, the etch rate has been turned out to be linearly increasing with the He flow rate. With this result, the Cl2/He mixture plasma has been utilized and tested for fabrication of the deep Si sidewall and nanosize Si pillar array.