Framed Recessed Oxide Scheme for Dislocation‐Free Planar Si Structures

Abstract

Recessed oxide isolation is widely used to reduce defects and increase packing density in Si integrated circuits. Unfortunately, the use of layers to mask the Si during the formation of the recessed oxide creates an unevenness in the surface, known as bird's‐head, and the lateral oxidation due to the under the layer creates bird's‐beak. Bird's‐head and bird's‐beak limit packing density and performance. In the framed recessed oxide‐isolation process presented in this paper, the is allowed to cover the Si surface in narrow stripes to define the recessed oxide boundary; thus both limitations are avoided. The samples were analyzed by Sirtl etch and TEM methods. For a layer 500Å thick, no induced crystal defects were present, probably because of partial stress relief within the narrow stripes. For a layer more than 1000Å thick, dislocations appeared along the edges. The dislocations, which are of the 60° type on (111) slip planes with alternate Burger's vectors, relieve part of the intrinsic tensile stress of the.