Method of fabricating high density flat cell mask ROM

Details Method of fabricating high density flat cell mask ROM Method of fabricating high density flat cell mask ROM

1998-05-22

2000-05-02

Wilczewski, Mary

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

438276, 438278, 438561, 438564, 438589, H01L 218246

Patent

active

060571950

ABSTRACT:
A method of fabricating high-density flat cell mask ROM is disclosed. The method comprises, formed a plurality of trenches in a silicon substrate firstly. An oxynitride layer is then grown on resultant surfaces to about 1-5 nm, After refilling a plurality of trenches with a first in-situ phosphorus doping polysilicon layer or amorphous silicon, etching back the polysilicon layer to form a flat surface by a CMP process is achieved. Subsequently, a thermal oxidation process is carried out to grow an oxide layer and to form a plurality of buried bit lines by diffusing the conductive impurities in the polysilicon layer through the oxynitride layer into the silicon substrate. A second in-situ n+ doped polysilicon layer is deposited and patterned as word lines; then a patterned photoresist coated on the second polysilicon layer except predetermining coding regions. Finally, a coding boron implant into the predetermined coding region is done to form normally off transistors.

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patent: 5866457 (1999-02-01), Wen
patent: 5937280 (1999-08-01), Wen

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