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Voidless Final Closure Process for Polysilicon Trench

IP.com Disclosure Number: IPCOM000060343D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Ghez, RA: AUTHOR [+2]

Abstract

In the manufacture of semiconductor devices, voids can form in the polysilicon trench (PST) refill process. This article proposes a high rate poly-Si deposition followed by a low rate poly-Si deposition which acts to reduce the incidence of voids. For vertical wall trenches the conformal stage growth rate is depicted in Fig. 1. The growth rate from the pre-nucleated LPCVD (Low Pressure Chemical Vapor Deposition) poly film 4 is uniform on all surfaces and is essentially equal to the rate of growth on a blanket silicon surface for the high temperature poly-Si refill 1. Insulators 3 delineate the sidewalls in the Si 2. A SiCl4-H2 reaction at 1000ŒC is used for the bulk of the fill. At a later stage in the process, due to some enhancement of growth from the bottom corners, a cusp 5, Fig. 2, forms within the trench.

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Voidless Final Closure Process for Polysilicon Trench

In the manufacture of semiconductor devices, voids can form in the polysilicon trench (PST) refill process. This article proposes a high rate poly-Si deposition followed by a low rate poly-Si deposition which acts to reduce the incidence of voids. For vertical wall trenches the conformal stage growth rate is depicted in Fig. 1. The growth rate from the pre-nucleated LPCVD (Low Pressure Chemical Vapor Deposition) poly film 4 is uniform on all surfaces and is essentially equal to the rate of growth on a blanket silicon surface for the high temperature poly-Si refill 1. Insulators 3 delineate the sidewalls in the Si 2. A SiCl4-H2 reaction at 1000OEC is used for the bulk of the fill. At a later stage in the process, due to some enhancement of growth from the bottom corners, a cusp 5, Fig. 2, forms within the trench. After the initial cusp formation the effective fill rate increases rapidly in the vertical direction "d" (Fig. 3). At this final closure stage, voids can be formed as a result of surfaces meeting (as a result of the rapid vector growth) with voids being locked in. Thus, a fast closure rate contributes to void formation. This article proposes having the refill formation be considered a two-step process with the rates being decreased at the initial cusp formation. The lower rates can be achieved in situ by several ways: 1) reducing temperature; 2) reducing the input reactant, SiCl4, thus reducing its par...