Recessed Oxide Without Bird's Beak
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
A scheme which will eliminate the "bird's beak" at the periphery of recessed oxide islands is described in this article. 1. At the surface of silicon substrate 2, form SiO2 layer 4. Through chemical vapor deposition (CVD) Si3N4 layer 6 and about 450- nanometer SiO2 layer 8. Using a mask defining the eventual recessed oxide regions, form windows in the composite of SiO2 layer 8, Si3N4 layer 6 and SiO2 layer 4. Further, etch exposed silicon 2 to a typical depth of about 400 nanometers. Selective reactive ion etching (RIE) is preferred for the above steps. The structure at this stage is shown in Fig. 1. 2. Through deposition of about 400 nanometers of polysilicon 10 and RIE, form sidewalls of polysilicon 10, as seen in Fig. 2. 3.