H - Electricity – 01 – L
Patent
H - Electricity
01
L
356/164
H01L 21/762 (2006.01) H01L 21/00 (2006.01)
Patent
CA 1043473
A METHOD FOR FORMING RECESSED DIELECTRIC ISOLATION WITH A MINIMIZED "BIRD'S BEAK" PROBLEM ABSTRACT OF THE INVENTION In the fabrication of integrated circuits, a method is provided for forming recessed silicon dioxide isolation in integrated circuits in which the "bird's beak" problems associated with conventional sili- con dioxide-silicon nitride composite masking structures is minimized. A conventional composite mask comprising a bottom layer of silicon dioxide and an upper layer of silicon nitride having a plurality of openings defining the regions in the silicon substrate which are to be thermally oxidized is formed on a silicon substrate. Recesses are then etched in the silicon substrate in registration with the openings in the composite mask. Then, the silicon dioxide layer is, in effect, over-etched to extend the openings in the silicon dioxide to greater lateral dimensions than the openings in the silicon nitride layer whereby the silicon nitride at the periphery of the openings is under- cut. A layer of silicon is then deposited in the recesses covering the undercut portions of said silicon nitride layer. Then, the structure subjected to thermal oxidation whereby the silicon in and abutting the recesses is oxidized to form regions of recessed silicon dioxide substantially coplanar with the unrecessed portions of the silicon substrate. Because of the undercutting and the deposition of silicon in the recesses, the "bird's beak" effect is minimized.
254112
International Business Machines Corporation
Na
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