Process for excavating trenches with a rounded bottom in a silic

Details Process for excavating trenches with a rounded bottom in a silic Process for excavating trenches with a rounded bottom in a silic

1989-12-12

1991-11-26

Chaudhuri, Olik

Fishing, trapping, and vermin destroying

437 70, 437 73, H01L 2176

Patent

active

050682024

ABSTRACT:
Encased (BOX) trench insolation structures in a silicon substrate are formed by firstly RIE etching an ONO multilayer (Oxide-Nitrite-Oxide) formed on the surface of a monocrystalline silicon substrate through a mask defining the active areas until exposing the silicon. A successive deposition of a conformable TEOS oxide layer followed by a "blanket" RIE etching, leave tapered "spacers" on the vertical etched flanks of the ONO multilayer. Through such a self-aligned "aperture" an isotropic plasma etching (round-etch) of the silicon is performed until the lateral, under-cut, etch front below the oxide spacers reaches the bottom layer of the isolation area defining etching previously conducted through the ONO multilayer. The peculiarities of the round-etch profile are thus fully exploited for more easily implanting the walls and bottom of the trench and avoiding the presence of electric field affecting sharp corners. The process maintains a precise lateral dimensional control and does not require special high resolution apparatuses.

REFERENCES:
patent: 3755001 (1973-08-01), Kodi et al.
patent: 3891469 (1975-06-01), Moriyama et al.
patent: 4271583 (1981-06-01), Kahng et al.
patent: 4538343 (1985-09-01), Pollack et al.
patent: 4942137 (1990-07-01), Siuan et al.

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