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Diffused Trench Isolation With P Channels

IP.com Disclosure Number: IPCOM000083695D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 110K

Publishing Venue

IBM

Related People

Chang, AW: AUTHOR [+4]

Abstract

Diffused trench isolation (DTI) replaces the present reachup isolation diffusion, which 1) eliminates inversion of the recessed oxide insulation (ROI) base that forms an N-skin path from collector-to-collector 6, 2) eliminates ROI to diffused isolation misalignment which causes base-isolation shorts in the horizontal directions, and 3) prevents emitter-to-collector N-channel shorting by providing P-channel stops along the ROI wall.

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Diffused Trench Isolation With P Channels

Diffused trench isolation (DTI) replaces the present reachup isolation diffusion, which 1) eliminates inversion of the recessed oxide insulation (ROI) base that forms an N-skin path from collector-to-collector 6, 2) eliminates ROI to diffused isolation misalignment which causes base-isolation shorts in the horizontal directions, and 3) prevents emitter-to-collector N-channel shorting by providing P-channel stops along the ROI wall.

In addition, the DTI process increases the collector-isolation breakdown voltage, decreases collector-isolation capacitance, increases the collector-to- collector breakdown between adjacent devices, and allows tightening the dimensions of the horizontal device.

A thin oxide is grown inside the ROI trench and a window is opened in the oxide at the bottom of the ROI trench. High-concentration boron is diffused or deposited by an ion implant method in the window and through the thin oxide along the ROI walls.

When the ROI is grown, the P+ isolation diffusion at the bottom of the trench extends downward to the epi-substrate interface and the lateral P diffusion in the ROI wall expands to form a P-channel stop, thus preventing emitter-to-collector shorting along the ROI wall because of N-channeling.

Fig. 1 shows the presently used reachup ROI 4 isolation process, and illustrates the following potential problems: an N inversion channel 6 between adjacent N areas an N inversion channel 8 between the c...