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Schottky Barrier Diode With Self-Aligned Guard Ring

IP.com Disclosure Number: IPCOM000041500D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Chang, CS: AUTHOR [+2]

Abstract

A technique is disclosed to fabricate a very narrow self-aligned Pguard ring for a Schottky barrier diode (SBD). The overetched oxide hole under a nitride layer at the periphery of the diode anode contact hole is used to form a polysilicon diffusion source for the guard ring. The width of this diffusion source is very narrow and independent of mask alignment whereby a minimum P+ diffused area results, allowing minimum charge storage and improved circuit performance. The process steps described below include only the diode, but readily can be extended to the integration of transistors as well. Conventional processes are used for the subcollector diffusion, epitaxial growth, device isolation (either diffusion or oxidation) and the N+ reachthrough for the diode cathode contact (Fig. 1).

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Schottky Barrier Diode With Self-Aligned Guard Ring

A technique is disclosed to fabricate a very narrow self-aligned Pguard ring for a Schottky barrier diode (SBD). The overetched oxide hole under a nitride layer at the periphery of the diode anode contact hole is used to form a polysilicon diffusion source for the guard ring. The width of this diffusion source is very narrow and independent of mask alignment whereby a minimum P+ diffused area results, allowing minimum charge storage and improved circuit performance. The process steps described below include only the diode, but readily can be extended to the integration of transistors as well. Conventional processes are used for the subcollector diffusion, epitaxial growth, device isolation (either diffusion or oxidation) and the N+ reachthrough for the diode cathode contact (Fig. 1). The structure is coated with resist and exposed using the SBD anode mask. The nitride layer is removed by RIE (reactive ion etch) or by wet etch. The oxide layer is removed by wet etch and is overetched slightly to create a mouse hole under the layer around the periphery of the contact hole. A polysilicon layer, doped with boron, is deposited conformally by chemical vapor deposition (CVD). The mouse hole around the periphery is filled with this doped polysilicon (Fig. 2). The bulk of the polysilicon layer is then removed by isotropic RIE technique. A ring of polysilicon is left in the mouse hole in contact with the silicon surface (...