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Forming Buried Layer by Diffusion

IP.com Disclosure Number: IPCOM000090294D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Viva, OR: AUTHOR [+2]

Abstract

This method is for forming a semiconductor structure which utilizes a heavily doped buried layer as a decoupling capacitor. The structure in drawing A is illustrative of a prior device. The structure comprises transistor 10 formed by diffusion into upper epitaxial layer 12, subcollector 11 formed under the transistor 10 by diffusion from a buried region in lower epitaxial layer 13, and decoupling capacitor region 14 which is formed from a buried region in substrate 15 directly under transistor 10 and subcollector 11.

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Forming Buried Layer by Diffusion

This method is for forming a semiconductor structure which utilizes a heavily doped buried layer as a decoupling capacitor. The structure in drawing A is illustrative of a prior device. The structure comprises transistor 10 formed by diffusion into upper epitaxial layer 12, subcollector 11 formed under the transistor 10 by diffusion from a buried region in lower epitaxial layer 13, and decoupling capacitor region 14 which is formed from a buried region in substrate 15 directly under transistor 10 and subcollector 11.

Region 14 in substrate 15 is present during the heat treatments required for the epitaxial growth of layers 13 and 12, as well as for the diffusion steps in forming transistor 10. There is a tendency for region 14 to outdiffuse sufficiently far into layer 13 and even into layer 12 to thus interfere with the impurity distributions in subcollector 11 and in other regions of transistor 10. In order to insure against this tendency, layer 13 is made relatively thick. The extended heat treatment required for such a thick layer has an adverse effect on the impurity distribution within layer 14.

This method minimizes the above problems by forming the decoupling capacitor region 14', drawing B, by the simultaneous outdiffusion from buried regions 16 formed in substrate 15', not in the areas immediately below transistor 10' and subcollector 11', but laterally of these regions, and autodoping of the initial growth of epitaxial...