Measurement of Fluorocarbon Radicals Generated from C₄F₈/H₂ Inductively Coupled Plasma: Study on SiO₂ Selective Etching Kinetics

Abstract

The kinetics of highly selective SiO 2 etching were studied on the basis of appearance mass spectroscopy (AMS) measurement of fluorocarbon radicals generated from C 4 F 8 /H 2 inductlvely coupled plasma (ICP). Results obtained by varying of H 2 concentration in C 4 F 8 , total pressure and RF power implied that CF 1 radical played a major role in the polymer film deposition. In particular, radical measurements carried out by varying the length of a quartz tube which was set in front of an inlet of radicals effusing into AMS revealed that CF 2 radical might not contribute to the polymer deposition and that the sticking probability of CF 1 radical was reduced considerably in the presence of hydrogen. It was also observed that in etching using a capillary plate as a high-aspect-ratio mask, the carbon-rich polymer film is deposited on the Si bottom surface in the presence of hydrogen at high CF 1 /CF 2 radical density ratio. Accordingly, CF 1 radicals whose surface loss is suppressed in the presence of hydrogen are likely to arrive at deep the bottom surface, forming the carbon-rich polymer by reaction of hydrogen with fluorine from CF 1 radicals.