Method of forming a contact hole of a dram

Abstract

The present invention relates to a method of forming a contact hole of a DRAM on the semiconductor wafer. The semiconductor wafer comprises a substrate, a first dielectric layer, two bit lines on the first dielectric layer, a second dielectric layer, and a photo-resist layer comprising an opening to define the pattern of the contact hole. The method comprises performing a first anisotropic etching process to vertically remove a portion of the two dielectric layers and two bit lines to grossly form the contact hole, removing the photo-resist layer in its entirety, performing a thermal oxidation to form a silicon oxide layer on the side walls of the two bit lines, then forming a silicon nitride layer on the surface of the contact hole, and performing a dry etching to remove the silicon nitride layer. There is a silicon oxide layer and a silicon nitride layer between the bit line and the contact hole, and the contact area of the contact hole will not be reduced.