Reduced Bird's Beak ROI Process
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Disclosed is a process for reducing the length of "bird's beak" associated with a recessed oxide isolation (ROI) region of semiconductor devices. The process uses phosphorous-doped polysilicon to achieve a rapid oxidation which lends itself to a reduced bird's beak. Referring to Fig. 1, starting with an N-Si, a thin layer of thermal oxide 2 and a layer of silicon nitride 3 are formed. The device region in the form of pedestal 1 is defined by reactive ion etching a trench. Then, another oxide layer 2' is grown in the trench. This oxide 2' will prevent any dopant in the subsequently deposited doped polysilicon layer from diffusing into the silicon. Silicon nitride 3 serves as an oxidation mask. Referring to Fig.