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Improved Ohmic Contacts in Openings

IP.com Disclosure Number: IPCOM000039410D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Deforge, P: AUTHOR [+5]

Abstract

According to the standard process, a phosphate silicate glass (PSG) layer is deposited during the low pressure chemical vapor deposition (LPCVD) process, both on the active face as well as onto the backside of the wafer. After the contact holes have been opened, a boron ion implantation followed by an annealing operation at high temperature is completed while the PSG layer on the backside is used as a source for the next wafer and causes undesired phosphorous diffusion into the contacts. This, in turn, causes a depletion of the boron concentration and even an inversion of the type of conductivity of the substrate and provides more resistive contacts. In order to avoid this problem while performing a photo-engraving step to form the contacts, an etching step has been added between the resist exposition and development steps.

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Improved Ohmic Contacts in Openings

According to the standard process, a phosphate silicate glass (PSG) layer is deposited during the low pressure chemical vapor deposition (LPCVD) process, both on the active face as well as onto the backside of the wafer. After the contact holes have been opened, a boron ion implantation followed by an annealing operation at high temperature is completed while the PSG layer on the backside is used as a source for the next wafer and causes undesired phosphorous diffusion into the contacts. This, in turn, causes a depletion of the boron concentration and even an inversion of the type of conductivity of the substrate and provides more resistive contacts. In order to avoid this problem while performing a photo-engraving step to form the contacts, an etching step has been added between the resist exposition and development steps. Buffer etch (40/1) to remove the PSG layer from the backside while the active face still remains protected. The present process allows the phosphorous source to be cancelled.

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