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Reduced Base Area Transistors

IP.com Disclosure Number: IPCOM000075729D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Magdo, IE: AUTHOR [+2]

Abstract

This device has a reduced base area, due to the elimination of margin around the collector base junction for contact alignment. Emitter side-wall effect is reduced. Higher base doping is permitted which enables better base contact, because of higher surface concentration. Emitter and base contacts are self-registered.

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Reduced Base Area Transistors

This device has a reduced base area, due to the elimination of margin around the collector base junction for contact alignment. Emitter side-wall effect is reduced. Higher base doping is permitted which enables better base contact, because of higher surface concentration. Emitter and base contacts are self- registered.

An oxide coating 10 is formed on the surface of a silicon wafer 12. An opening is made in the coating 10 to permit a base diffusion 14 to be formed in the wafer. The collector-base junction 16 extends under the oxide coating 10. A silicon nitride coating 18 is formed in the exposed base area and includes openings 18' and 18''. The openings 18' and 18'', as well as the underlying silicon, are oxidized either thermally or anodically to reduce surface concentration. The silicon nitride between openings 18' and 18'' is removed to expose the wafer for an emitter diffusion. An emitter-base junction 20 terminates at the oxidized sections 22' and 22''. The oxidized areas reduce the emitter sidewall effect. On removal of the remaining silicon nitride, openings are created in the base area for base contacts. The collector-base junction 16 is sufficiently beneath the oxide 10 so that metallization in the base openings will not adversely affect the device. Likewise, oxides 22' and 22'' protect the emitter-base junction 20 from metallization in the emitter electrode area.

To prevent further conflict between the collector-base junct...