Abstract
Reactive ion etching (RIE) of silicon nitride in a plasma system, with fluorine-based gas mixture, had been studied using an experimental design. With the dimensions of devices decreasing, the etching characteristics, such as etching rate and uniformity of etching rate, must be controlled and some complex tradeoffs need to be managed. For this reason, we initiated a program to optimize etching characteristics using Taguchi robust design as a Design of Experiment (DOE) methodology. This DOE consisted of four major variable parameters, which were RF power, chamber pressure and two processing gas. Depending on analyzed data, the effects of the each variable on etching performance are discussed and main factor is examined. The physical and chemical explanations have been based upon the etching model obtained with the DOE. Overall Taguchi method is a helpful tool to optimize the experimental variables and the aimed etching performance was investigated by using the model. The experimentally optimal results are as follows: low etching rate, 500A/min and applicable uniformity, 6% are achieved for the etching process with two kind of etching gas mixture, CF4/O2 and SF6/He together with measurements of plasma parameters. In addition, processes with CF4/He gas mixture with gaseous ratio ≦1/1 result in non-undercutting etching profile and smooth surface.