Fishing – trapping – and vermin destroying
Patent
1988-06-07
1989-04-04
Hearn, Brian E.
Fishing, trapping, and vermin destroying
148DIG117, 148DIG122, 437 69, 437 63, 437162, 437968, H01L 2176
Patent
active
048182354
ABSTRACT:
The invention relates to an improved isolation structure to separate active regions of integrated circuits and a method of its preparation. These isolation structures eliminate the so-called "bird's beak effect" which reduces the effective device area and thereby permit the manufacture of high packing desnity VLSIs. In the process, a silicon substrate is initially coated, first with a stress-release layer and then with a layer of polysilicon. After the polysilicon is removed from the active device area and patterned, a silicon nitride layer and then a thick layer of photo-resist are coated on the structure. By means of etching, the tops of the polysilicon cusps are exposed. At this stage, the vertical side walls of the polysilicon cusps remain coated with silicon nitride. The polysilicon layer is then completely oxidized to form the field oxide layer. In the final step of the process, the remaining silicon nitride and the stress-release layers are removed. The resulting field oxide is clearly defined and free of the bird's beak effect.
REFERENCES:
patent: 4574469 (1986-03-01), Mastroianni et al.
patent: 4615746 (1986-10-01), Kawakita et al.
patent: 4757032 (1988-07-01), Contiero
Hearn Brian E.
Industry Technology Research Institute
Lewen Bert J.
Sternberg Henry
Wilczewski M.
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