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Integratable Symmetrical High Voltage MOSFET Structure

IP.com Disclosure Number: IPCOM000078135D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Krick, P: AUTHOR [+2]

Abstract

A metal oxide semiconductor field-effect transistor (MOSFET) structure has been devised, which allows the MOSFET to sustain drain to substrate potentials substantially higher than normal break~own voltages of most FET's, while not sacrificing their bilateral conduction capability, so as to permit their use in driver circuits for gas display panels and liquid crystals. Such driver circuits could be employed on chips having other integrated circuits fabricated thereon.

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Integratable Symmetrical High Voltage MOSFET Structure

A metal oxide semiconductor field-effect transistor (MOSFET) structure has been devised, which allows the MOSFET to sustain drain to substrate potentials substantially higher than normal break~own voltages of most FET's, while not sacrificing their bilateral conduction capability, so as to permit their use in driver circuits for gas display panels and liquid crystals. Such driver circuits could be employed on chips having other integrated circuits fabricated thereon.

On a p-type substrate 2, such as silicon, a diffusion of the source region 4 and the drain region 6 is carried out, but a two step diffusion takes place. The first region R1 is lightly doped with phosphorous and the second region R2 is heavily doped with arsenic. The heavily doped regions R2 permit ohmic contacts to be made to the source and drain regions, whereas the guard ring R1 around each diffused region allows for an open geometry, eliminates the need for two layers of metal to interconnect the circuits on a chip and makes subsequent ion implantation steps in the completion of an FET noncritical.

After the metal gates 8 and 10 are deposited on the gate insulation 12 of an FET, n-type ions are implanted between and on both sides of such gates. The dual gates 8 and 10, when one (10) of them is biased, reduces the normal component of the electrical fields due to gate 8 in drain region 6 so as to increase the reverse breakdown voltage in that r...