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Forming Double Diffused Regions

IP.com Disclosure Number: IPCOM000076726D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Fang, FF: AUTHOR [+2]

Abstract

In this technique double-diffused regions in semiconductors can be fabricated, in which the resulting structure has low capacitance relative to conventional double diffused regions.

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Forming Double Diffused Regions

In this technique double-diffused regions in semiconductors can be fabricated, in which the resulting structure has low capacitance relative to conventional double diffused regions.

In semiconductor devices, it is frequently necessary that the impurity concentration have a different value adjacent a diffused region than in the surrounding bulk material. This objective has in the past been achieved by subsequent diffusions in the semiconductor through the same diffusion opening. The second diffusion is contained within the first diffusion. However, when the diffused region is of significant size relative to the accompanying structure, there is an objectionable increase in capacitance.

In this process a layer 10 of masking material, preferably SiO(2) having a thickness on the order of 1000 angstroms is grown or deposited on wafer 12. An opening 14 is fabricated using conventional photolithographic techniques. A first relatively shallow diffused region 16 is formed by ion implantation, indicated schematically by arrow 18, which impinges the wafer 12 at an angle relative to the surface. Region 16 can be fashioned to extend outside the perimeter of window 14, as indicated in Fig. 1. The region is extended about the opening by rotating the wafer 12 in a plane normal to the wafer surface. As indicated in Fig. 2, a second ion implantation, indicated by arrow 20, is then performed with the ions directed normal to the surface of wafer 12. Th...