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Fabricating a Voltage Variable Capacitor

IP.com Disclosure Number: IPCOM000078107D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Ziegler, JF: AUTHOR

Abstract

A method for making semiconductor voltage-variable capacitors is described, which makes use of the fact that very high concentrations of arsenic in silicon has a sink effect on boron diffusions.

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Fabricating a Voltage Variable Capacitor

A method for making semiconductor voltage-variable capacitors is described, which makes use of the fact that very high concentrations of arsenic in silicon has a sink effect on boron diffusions.

A capacitor comprises two electrical conductors separated by an insulator. One begins with a silicon base 2 into which arsenic is diffused to a depth D1, to metallize the silicon and attain one electrical conductor of the desired capacitor. Boron is ion implanted into the silicon to a depth D2 and its profile P is shown in the figure.

If very high concentrations of arsenic are diffused into the silicon, it produces a sink effect on the boron diffusions so that the dotted line L becomes the left portion of the boron diffusion profile, causing the boron to be depleted in region
R. If contact 4 is made to the arsenic diffused silicon (one electrode) and another contact 6 is made to the boron diffused silicon (the second electrode), a capacitor is formed in that the depleted region R is an insulator.

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