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Method for Decoupling Intrinsic/extrinsic Base Depth in Advanced Transistors

IP.com Disclosure Number: IPCOM000061937D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hsieh, CM: AUTHOR [+2]

Abstract

A process has been developed which moves the intrinsic base closer vertically to the subcollector in semiconductor devices thereby reducing the region of lightly doped epitaxy. This will avoid the degradation of bipolar transistor switching speed which may occur at high currents due to base stretching.

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Method for Decoupling Intrinsic/extrinsic Base Depth in Advanced Transistors

A process has been developed which moves the intrinsic base closer vertically to the subcollector in semiconductor devices thereby reducing the region of lightly doped epitaxy. This will avoid the degradation of bipolar transistor switching speed which may occur at high currents due to base stretching.

In advanced transistors a minimum epi thickness is required to accommodate low CCB extrinsic base and other devices. This thickness becomes too great for shallow transistor structures and in such devices with a thick epi a lowly-doped N-epi region will remain under the intrinsic base. This causes base stretching at high current densities, thereby degrading transistor performance.

In developed process, it is proposed to decrease the extra epi under the intrinsic base. This will not change the extrinsic CCB and will also remove the concern over a possible extrinsic/ intrinsic linkup. Conventional processing of the transistor is done up to the extrinsic base 1 drive-in. A reactive ion etch is used to take the single crystal epi 2 to a depth of 3 below the single crystal surface such that the intrinsic base is close to the subcollector.

A chemical vapor deposition SiO2 is applied and the sidewall spacer 11 is formed. Boron ions are implanted and then the intrinsic base 5 drive-in accomplished. The polysilicon 4 is deposited in a conventional manner and arsenic ions are implanted in the emitter...