Bias power dependence of reactive ion etching lag in contact hole etching using inductively coupled fluorocarbon plasma

Abstract

This article describes the bias power dependence of reactive ion etching (RIE) lag from 1300to700W bias power in contact hole etching using inductively coupled C2F6 fluorocarbon plasma without additive gases at 2600W source power, 5mTorr operational pressure, and a total gas flow of 40SCCM (SCCM denotes cubic centimeter per minute at STP). RIE lag is estimated by etching multiple feature sizes on one wafer. In the discussion of the bias power dependence of RIE lag, the authors used an RIE lag model based on a solid angle model modified by a specular reflection on the wall of a contact hole. The RIE lag model indicates that the RIE lag characteristic is caused by the three-dimensional structure of the contact hole. The etched depth relates to a term of a cubic root of etch time. Moreover, a decrease in bias power slows the etch rates, but the maximum etched depth increases in contact hole etching. By decreasing the bias power from 1300to700W, the RIE lag characteristic can be dramatically improved in a limitation aspect ratio from 27 to 133.