Highly Selective Contact Hole Etching Using Electron Cyclotron Resonance Plasma

Abstract

The SiO 2 etching process is one of the most significant processes in ultra-large-scale integration (ULSI) fabrication. In order to obtain fine contact holes, it is necessary to achieve both highly selective etching of SiO 2 over other materials, and non-reactive ion etch (non-RIE) lag. We investigated the etching characteristics and the effect of O 2 addition in C 4 F 8 +O 2 plasma using electron cyclotron resonance (ECR) discharge. In C 4 F 8 +O 2 plasma, we can obtain dense fluorocarbon films at low pressure, and films are more durable against ion bombardment than at high pressure. This film enables the suppression of O atoms to the Si surface, and the achievement of high SiO 2 -to-Si selectivity. By additional O 2 , dissociation of high-mass species such as C 2 F 5 proceeds, and at about 20%O 2 , low-mass species, such as C, CF, and CF 2 , increase. Thus we can obtain high SiO 2 -to-Si selectivity and high-aspect-ratio fine contact holes.