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Prevention of CMOS Circuit Latch-Up

IP.com Disclosure Number: IPCOM000062057D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Lai, FS: AUTHOR [+2]

Abstract

This article relates generally to integrated circuit fabrication and, more particularly, to a method of constructing a diode clamp to avert forward biasing of complementary parasitic bipolar transistors. Latch-up of bulk CMOS integrated circuits can be prevented by constructing a Schottky diode clamp having a turn-on voltage lower than that necessary to bias the parasitic pnp transistor into an active mode. In the figure, the CMOS chip is fabricated to the point of source/drain formation using standard processes. A mask is then applied to the chip surface to expose only the p-channel drain. Thereafter, the drain is etched with anisotropic chemical etchants and coated with titanium silicide to form the Schottky diode. The silicided contact and guard ring provided by the p+ region produce a reliable Schottky diode.

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Prevention of CMOS Circuit Latch-Up

This article relates generally to integrated circuit fabrication and, more particularly, to a method of constructing a diode clamp to avert forward biasing of complementary parasitic bipolar transistors. Latch-up of bulk CMOS integrated circuits can be prevented by constructing a Schottky diode clamp having a turn- on voltage lower than that necessary to bias the parasitic pnp transistor into an active mode. In the figure, the CMOS chip is fabricated to the point of source/drain formation using standard processes. A mask is then applied to the chip surface to expose only the p-channel drain. Thereafter, the drain is etched with anisotropic chemical etchants and coated with titanium silicide to form the Schottky diode. The silicided contact and guard ring provided by the p+ region produce a reliable Schottky diode. Using the above-described approach, the emitter-base junction of the parasitic pnp transistor will not be biased into an active mode.

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