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Technique to Eliminate N-N Leakage in ROI Technology

IP.com Disclosure Number: IPCOM000043375D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Bhatia, HS: AUTHOR [+3]

Abstract

A structure and process are described for preventing N-N leakage in a recessed oxide isolation (ROI) structure that includes, under the oxide regions, both a first diffused region in the substrate, prior to epi, that diffuses upwardly and a second diffusion from the bottom of the isolation trenches that diffuses downwardly. The starting structure is a p- substrate 1 containing n+ subcollectors 2. An isolation window is opened, followed by a boron diffusion which creates p+ areas 3. This is followed by epi 4 growth and heat treatment which causes both the n+ and p+ regions to diffuse upwards into the top layer (Fig. 1). A blanket layer 5 of SiO2 is created either by chemical vapor deposition (CVD) or thermal oxidation. This is followed by CVD of Si3N4 layer 6.

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Technique to Eliminate N-N Leakage in ROI Technology

A structure and process are described for preventing N-N leakage in a recessed oxide isolation (ROI) structure that includes, under the oxide regions, both a first diffused region in the substrate, prior to epi, that diffuses upwardly and a second diffusion from the bottom of the isolation trenches that diffuses downwardly. The starting structure is a p- substrate 1 containing n+ subcollectors 2. An isolation window is opened, followed by a boron diffusion which creates p+ areas 3. This is followed by epi 4 growth and heat treatment which causes both the n+ and p+ regions to diffuse upwards into the top layer (Fig. 1). A blanket layer 5 of SiO2 is created either by chemical vapor deposition (CVD) or thermal oxidation. This is followed by CVD of Si3N4 layer 6. The wafer is patterned with photoresist, and a trench is etched into the silicon for future ROI growth. About 2000 ~ of SiO2 7 is grown on the walls of the trench (Fig. 2). Using an isolation mask, the SiO2 layer 7 is etched away at the bottom of the trench. Another boron implantation is made and subsequent heat treatment causes a p+ region 8 to diffuse downward, meeting the p+ region 3 below it (Fig. 3). The wafer is then put through the standard ROI process to fill the trench and complete the isolation (Fig. 4).

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