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Recessed Oxide Without Bird's Beak

IP.com Disclosure Number: IPCOM000043273D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Jambotkar, CG: AUTHOR

Abstract

A scheme which will eliminate the "bird's beak" at the periphery of recessed oxide islands is described in this article. 1. At the surface of silicon substrate 2, form SiO2 layer 4. Through chemical vapor deposition (CVD) Si3N4 layer 6 and about 450- nanometer SiO2 layer 8. Using a mask defining the eventual recessed oxide regions, form windows in the composite of SiO2 layer 8, Si3N4 layer 6 and SiO2 layer 4. Further, etch exposed silicon 2 to a typical depth of about 400 nanometers. Selective reactive ion etching (RIE) is preferred for the above steps. The structure at this stage is shown in Fig. 1. 2. Through deposition of about 400 nanometers of polysilicon 10 and RIE, form sidewalls of polysilicon 10, as seen in Fig. 2. 3.

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Recessed Oxide Without Bird's Beak

A scheme which will eliminate the "bird's beak" at the periphery of recessed oxide islands is described in this article. 1. At the surface of silicon substrate 2, form SiO2 layer 4. Through chemical vapor deposition (CVD) Si3N4 layer 6 and about 450- nanometer SiO2 layer 8. Using a mask defining the eventual recessed oxide regions, form windows in the composite of SiO2 layer 8, Si3N4 layer 6 and SiO2 layer 4. Further, etch exposed silicon 2 to a typical depth of about 400 nanometers. Selective reactive ion etching (RIE) is preferred for the above steps. The structure at this stage is shown in Fig. 1. 2. Through deposition of about 400 nanometers of polysilicon 10 and RIE, form sidewalls of polysilicon 10, as seen in Fig. 2. 3. Remove the remaining portion of the SiO2 layer 8 using, for example, buffered HF, as shown in Fig. 3. 4. Form the typical 1 mm thick thermal SiO2 layer 12 at the exposed silicon/polysilicon surface, as illustrated in Fig. 4. The polysilicon sidewall 10 is then consumed and converted to SiO2 . Because of the presence of the polysilicon sidewall 10, the usual growth of bird's beak oxide at the top corners of silicon trenches, which occurs in the standard recessed oxide process, is prevented here. 5. Apply about a 1.2 mm thick coating of material 14, such as photoresist, which has the property of planarizing the surface, as shown in Fig. 5, and also has about the same rate of etching as SiO2 when an RIE agent...