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Self-Aligned Guard Ring Formation for Schottky Barrier Diodes Using Boron-Doped Oxides

IP.com Disclosure Number: IPCOM000046673D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Beyer, KD: AUTHOR

Abstract

A self-aligned process for forming p-doped guard rings around Schottky barrier diode contacts is described. Dielectric layers, such as thermal SiO2, CVD (chemical vapor deposited) SiO2 or combinations of SiO2/Si3N4, can be used in conjunction with straight walled contact openings or ones having a Si3N4 overhang. A 200 to 500 ˜ thick undoped polysilicon layer 13 and a 1000 to 5000 ˜ thick CVD boron-doped oxide layer 14 are deposited over contact openings 16 in a masking structure consisting of a Si3N4 layer 12 and a thermal SiO2 layer 11 covering the n-doped silicon substrate 10 (Fig. 1). During a timed directional reactive ion etch in CF4 of the boron doped oxide, the underlying polysilicon layer 13 acts as an etching stop layer and the doped oxide layer is removed everywhere except at sidewall locations 15 (Fig. 2).

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Self-Aligned Guard Ring Formation for Schottky Barrier Diodes Using Boron-Doped Oxides

A self-aligned process for forming p-doped guard rings around Schottky barrier diode contacts is described. Dielectric layers, such as thermal SiO2, CVD (chemical vapor deposited) SiO2 or combinations of SiO2/Si3N4, can be used in conjunction with straight walled contact openings or ones having a Si3N4 overhang. A 200 to 500 ~ thick undoped polysilicon layer 13 and a 1000 to 5000 ~ thick CVD boron-doped oxide layer 14 are deposited over contact openings 16 in a masking structure consisting of a Si3N4 layer 12 and a thermal SiO2 layer 11 covering the n-doped silicon substrate 10 (Fig. 1). During a timed directional reactive ion etch in CF4 of the boron doped oxide, the underlying polysilicon layer 13 acts as an etching stop layer and the doped oxide layer is removed everywhere except at sidewall locations 15 (Fig. 2). After the removal of the thin polysilicon layer by a timed wet polysilicon etch, the p-doped guard rings 18 are formed during a 30-minute heat treatment between 900 and 1050OEC in N2 or forming gas by the boron outdiffusion from the doped oxide sidewall 15 through the polysilicon into the silicon (Fig. 3). The process may be modified by the deposition of a 200 to 500 ~ thick boron-doped polysilicon layer on top of the dielectric structure prior to the contact opening. After the contact opening, a 1000 to 50000 ~ thick CVD boron-doped oxide layer is deposited. Durin...