Actinometry study for etching characteristics of Ta film using chlorine plasma

Abstract

The etching characteristics of Ta thin film with chlorine plasma have been studied by electron cyclotron resonance (ECR) plasma etching system with actinometry analyzing method. In this research, normal etching process has been applied above 0.25mm, but below this pattern scale the RIE lag has been observed - pattern distortion. In order to overcome this phenomenon, the change of plasma chemistry has been investigated with actinometry method along the variation of the ECR plasma system parameters such as microwave power, RF power, working pressure and gas chemistry ( Ar composition in Cl2). As a result, it has been found that microwave power and RF power were the most effective variables in ECR plasma system on the density of Cl radical - the most reactive etching species. On the basis of these results, etching process was decomposed into two steps - sputtering dominant process and chemical reaction dominant process. By this double step etching process, accelerated formation of Ta chloride - byproduct during etching - by chemical reaction dominant process at the second step, following sputtering dominant process step, successfully protected sidewall due to its low volatility, resulting in the suppression of RIE lag