Method of Forming Contact Holes
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
When contact holes are formed in an SiO2/Si3N4 double layer on a semiconductor substrate, an overhang of the Si3N4 layer at the contact hole edges is avoided by widening the holes in the photoresist mask prior to etching the SiO2 . Subsequently, the exposed Si3N4 and the exposed SiO2 are simultaneously etched. On the semiconductor substrate 1, an SiO2 layer 2, an Si3N4 layer 3, and a photoresist layer 4 are deposited. Layer 4 is structured to suit the desired via hole pattern. Using layer 4 as an etch mask, the Si3N4 layer 3 is selectively etched, preferably by reactive ion etching (RIE) in a CF4 atmosphere, until SiO2 layer 2 has been exposed. A schematic cross-sectional view of the structure at this stage is shown in Fig. 1. Subsequently, photoresist mask 4 (Fig.