PBLOCOS with sandwiched thin silicon nitride layer

Details PBLOCOS with sandwiched thin silicon nitride layer PBLOCOS with sandwiched thin silicon nitride layer

1993-07-22

1995-03-14

Fourson, George

Fishing, trapping, and vermin destroying

437 70, H01L 2176

Patent

active

053977327

ABSTRACT:
A method of forming a silicon oxide isolation region with reduced bird's beak length on the surface of a silicon substrate is described. A layer of silicon oxide is formed on the surface of the silicon substrate. A first layer of silicon nitride is formed on the surface of the silicon oxide layer, to prevent diffusion of oxygen into the silicon oxide layer and the substrate during subsequent oxidation steps, thereby reducing the bird's beak length. A layer of polysilicon is formed on the surface of the silicon nitride layer. A second layer of silicon nitride is formed on the surface of the polysilicon layer. The second silicon nitride layer, the polysilicon layer and the first silicon nitride layer are patterned to form an oxidation mask and to form an opening over the silicon oxide layer. The silicon substrate is ion implanted through the opening to form a channel stop implant. The silicon substrate and silicon oxide layer in the region not masked by the oxidation mask are oxidized to form the silicon oxide isolation region. A thin surface oxide layer forms on the surface of the second silicon nitride layer during this oxidation step. The thin surface oxide layer and second silicon nitride layer are removed. The polysilicon layer is oxidized, and then removed. The first silicon nitride layer is then removed. Finally, the silicon oxide layer is removed to complete formation of the silicon oxide isolation region.

REFERENCES:
patent: 4829019 (1989-05-01), Mitchell et al.
patent: 5002898 (1991-03-01), Fritzinger et al.
patent: 5215930 (1993-06-01), Lee et al.
Ghandhi, S., VLSI Fabrication Principles: Silicon & Gallium Arsenide, 1983, John Wiley & Sons, p. 360.

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