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Suitable Trench Shape for Dielectric Isolation

IP.com Disclosure Number: IPCOM000044020D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Beyer, KD: AUTHOR [+3]

Abstract

This article relates to the minimization of surface voids encountered during such CVD (chemical vapor deposition) trench filling processes as polysilicon or oxide filling. Surface voids, by allowing oxidation to occur within the trenches during subsequent processing, generate stresses which, in turn, generate defects. The disclosed technique creates a suitable trench shape by creating a "positive slope" sidewall, thereby eliminating surface voids while also reducing the size and rate of occurrence of any internal voids. By a novel application of the oxide sidewall technology for trench formation, a tapered trench opening is obtained, as shown in Figs. 1 through 3. Subsequent fabrication processes for obtaining a polysilicon filled trench are illustrated by Figs. 4 through 6.

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Suitable Trench Shape for Dielectric Isolation

This article relates to the minimization of surface voids encountered during such CVD (chemical vapor deposition) trench filling processes as polysilicon or oxide filling. Surface voids, by allowing oxidation to occur within the trenches during subsequent processing, generate stresses which, in turn, generate defects. The disclosed technique creates a suitable trench shape by creating a "positive slope" sidewall, thereby eliminating surface voids while also reducing the size and rate of occurrence of any internal voids. By a novel application of the oxide sidewall technology for trench formation, a tapered trench opening is obtained, as shown in Figs. 1 through 3. Subsequent fabrication processes for obtaining a polysilicon filled trench are illustrated by Figs. 4 through 6. Deep trench masking layers are initially defined using conventional lithography and RIE (reactive ion etching) [Fig. 2]. Sidewall layers are next removed from the upper surface and the trench bottom by RIE [Fig. 3], producing a "sloped sidewall" which extends into the silicon. The angle of this "positive slope" permits later closure of any surface holes in the CVD refill. The silicon trench is then etched (RIE) to its final depth and a second sidewall deposited [Fig. 4], this structure being composed either of "all oxide" or an oxide-nitride composite. The next step (of several alternatives available), used with polysilicon fill, is to include a...