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Browse Prior Art Database

High Voltage Device Using Buried Contact Drain Diffusion

IP.com Disclosure Number: IPCOM000043555D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Kasold, JP: AUTHOR

Abstract

Using buried contact drain diffusion allows higher voltages to be used (15-25 volts) in standard Si-gate processes without any extra process steps to improve junction breakdown voltage. The drain diffusion is formed from the out-diffusion of phosphorus from the Polysilicon-1 layer 11 in the "buried contact" 12 region (Poly-1 in contact with the substrate). The out-diffused junction is deeper (1.2-1.5 mm) and has a lower doping gradient at its edges than a "standard" .5 mm arsenic ion-implanted junction, thereby increasing significantly the junction avalanche breakdown voltage to the substrate.

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High Voltage Device Using Buried Contact Drain Diffusion

Using buried contact drain diffusion allows higher voltages to be used (15-25 volts) in standard Si-gate processes without any extra process steps to improve junction breakdown voltage. The drain diffusion is formed from the out-diffusion of phosphorus from the Polysilicon-1 layer 11 in the "buried contact" 12 region (Poly-1 in contact with the substrate). The out-diffused junction is deeper (1.2-1.5 mm) and has a lower doping gradient at its edges than a "standard" .5 mm arsenic ion-implanted junction, thereby increasing significantly the junction avalanche breakdown voltage to the substrate. By overlapping the Poly-1 11 by Poly-2 13 on the channel side and by overlapping the ROX 14 with Poly-1 11 on its 3 other edges, the arsenic ion-implant (used for the "source" 15 diffusion and all "conventional" devices) is blocked from the thin oxide "drain" 16 region such that the only source of n-type dopant is the Poly-1 buried contact 12.

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