METHOD OF FORMING CONTACT HOLES IN SiO2/Si3N4 COMPOSITE LAYERS ON SEMICONDUCTOR WAFERS
Original Publication Date: 1985-Jul-01
Included in the Prior Art Database: 2005-Feb-19
The formation of contact holes comprises the steps of completely stripping the oxide coating existing after semiconductor processing steps, regrowing an SiO2 layer and an overlying Si3N4 layer by chemical vapor deposition (CVD), and finally etching contact holes through the two layers. After completion of the steps necessary for forming devices in a semiconductor wafer 1, oxide coating 2 on the wafer surface is inhomogeneous in its thickness (Fig. 1). If after the application of an Si3N4 top layer 3, the pattern of contact holes 4, 5 is first etched into Si3N4 layer 3 and then into oxide coating 2, underetching of Si3N4 layer 3 causes the size of contact holes 4, 5 to deviate on the semiconductor surface from the pattern in Si3N4 layer 3 in dependence on the oxide thickness.