Elimination of Bird's Beak in ROI Process
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
The density and planarity of devices fabricated by the recessed oxide isolation (ROI) process is negatively impacted by the formation of the ""bird's beak'' during the ROI oxide growth, as shown by the Fig. 1, wherein the ROI is 10, silicon body 11, thin thermally grown silicon dioxide 12 and silicon nitride 13. The bird's beak can be prevented with an extra masking process in which a narrow strip of silicon nitride (about 2 microns wide) is deposited directly on the silicon surface. This prevents oxygen diffusion under the silicon nitride, and hence formation of the bird's beak. Alternatively, a self-aligned process can achieve the same goal without the use of the extra masking step.