A new chemical dry etching

Abstract

A new method for etching by a plasma technique has been developed. Active species with a long lifetime are created by the discharge of CF4-O2 mixture and transported from the discharge region to the reaction region where samples are etched. Consequently, the immersion of the samples in the plasmas can be avoided and the condition of etching process can be easily controlled. An etching characteristics heavily depends on the ratio of flow rate of CF4 and of O2, and the maximum etching rate occurs at the ratio of about 1:1. Activation energies for the etch rate of poly-Si and SiO2 are 1.1 kcal/mol and 4.2 kcal/mol, respectively. Through a mass spec-trometric analysis the etching mechanism is hypothesized: (i) COF* creation by CF4-O2 discharge and (ii) F* formation by dissociation of COF* at the surface of samples. © 1976 The Japan Society of Applied Physics.