Browse Prior Art Database

Self-Aligned Polysilicon Guard Ring for Schottky Barrier Diode

IP.com Disclosure Number: IPCOM000038439D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Antipov, I: AUTHOR

Abstract

A proposal suggests that a polysilicon (PolySi) guard ring be formed around Schottky barrier diode (SBD) anodes by a self-aligned process. Such a ring would provide protection against any oxide etches used in subsequent processing steps. The method proposes to use the undercut-refill technique to achieve the PolySi ring. In the process a layer 1 of Si3N4 (Fig. 1) is deposited on an SiO2 layer 2 above an N- substrate 3. The area defining the SBD anode is opened by etching the Si3N4 and SiO2 . The SiO2 is purposely undercut 4. Chemical vapor deposition (CVD) is used to deposit a thin layer 5 of PolySi (Fig. 2). This may be doped or undoped P- type PolySi. The PolySi layer effectively fills the undercut.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 81% of the total text.

Page 1 of 2

Self-Aligned Polysilicon Guard Ring for Schottky Barrier Diode

A proposal suggests that a polysilicon (PolySi) guard ring be formed around Schottky barrier diode (SBD) anodes by a self-aligned process. Such a ring would provide protection against any oxide etches used in subsequent processing steps. The method proposes to use the undercut-refill technique to achieve the PolySi ring. In the process a layer 1 of Si3N4 (Fig. 1) is deposited on an SiO2 layer 2 above an N- substrate 3. The area defining the SBD anode is opened by etching the Si3N4 and SiO2 . The SiO2 is purposely undercut 4. Chemical vapor deposition (CVD) is used to deposit a thin layer 5 of PolySi (Fig.
2). This may be doped or undoped P- type PolySi. The PolySi layer effectively fills the undercut. A reactive ion etch (RIE) is used to remove the PolySi from the monocrystalline silicon in the anode and from the top of the nitride. The RIE leaves a PolySi ring 6 (Fig. 3) under the nitride overhang. If the PolySi is undoped, it may be oxidized instead of using an RIE and then removed by an oxide etch. As the process is continued if doped P-type PolySi had been used, P- type impurities will diffuse into the monosilicon during the heat cycle to form a P- type guard ring. If the PolySi used were the undoped type, the N-type impurities will diffuse into the ring, forming N-type silicon. The SBD anode is completed by metal deposition. The precleaning oxide etches will have no adverse effect on the anode si...