Trench isolation using gated sidewalls

Details Trench isolation using gated sidewalls Trench isolation using gated sidewalls

1992-11-25

1994-01-04

Fourson, George

Fishing, trapping, and vermin destroying

437 61, 437203, H01L 2128, H01L 21311

Patent

active

052759652

ABSTRACT:
The invention is directed to improving trench isolation between active devices by using gated sidewalls. In a first embodiment, trenches are etched into the substrate and a thin oxide film is formed to passivate the trench sidewalls and serve as a sidewall gate oxide. The oxide is removed from the bottom of the trench while leaving the sidewall oxide intact. A thin poly layer is formed into the trench so that the thin poly does not completely fill the trench, yet the thin poly film will overlie the oxide sidewalls and make contact to the exposed substrate at the bottom of the trench. The trench is then completely filled with a conformal oxide that is planarized. The planarized oxide is etched during thermal oxide etch and a sacrificial oxide is grown. Following threshold adjust implants, the sacrificial oxide is removed and the final gate sidewall oxide is formed. In a second embodiment, the process steps vary by leaving the thin oxide film at the bottom of the trench and then forming a thin poly film over the thin film oxide. The steps then continue as in the first embodiment and the thin poly in the trench is later tied to the substrate at points on the die external from the trench.

REFERENCES:
patent: 4295924 (1981-10-01), Garnache
patent: 4673962 (1987-06-01), Chatterjee et al.
patent: 4679307 (1987-07-01), Barsony
patent: 4717682 (1988-01-01), Taka et al.
patent: 5010025 (1991-04-01), Solomon

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