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Guard Ring Schottky Clamp for a Polysilicon Process

IP.com Disclosure Number: IPCOM000049707D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Samuels, DJ: AUTHOR [+2]

Abstract

Conventional processes for providing Schottky clamp transistor circuits utilize at best 15 masks whereby oxide-defined Schottky diodes frequently have been determined unstable and therefore representing reliability problems. Without adding additional masks, a way is devised to provide a P implanted Schottky guard-ring while still maintaining polysilicon contacts to the transistor.

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Guard Ring Schottky Clamp for a Polysilicon Process

Conventional processes for providing Schottky clamp transistor circuits utilize at best 15 masks whereby oxide-defined Schottky diodes frequently have been determined unstable and therefore representing reliability problems. Without adding additional masks, a way is devised to provide a P implanted Schottky guard-ring while still maintaining polysilicon contacts to the transistor.

The proposed technique basically takes into account diffusion "shorting" as a means of integrating the Schottky diode with the transistor. Thus, when making contact to the Schottky anode, contact is also made to the NPN transistor base.

This technique utilizes the following rules which have to be maintained: keeping recessed oxide isolation away from the Schottky, insuring that the Schottky has a three sigma contact coverage which in turn assures a minimum contact to the base, and insuring that P- implant has a three sigma "linkage" to the extrinsic base.

With this, a more reliable Schottky clamp is achieved with little added area and without requiring new masks.

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