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Stabilized Lateral PNP Transistor

IP.com Disclosure Number: IPCOM000048792D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Michel, AE: AUTHOR [+2]

Abstract

The polysilicon emitter and base processes allow, with no additional process complexity, the addition of a stabilized lateral PNP transistor which is insensitive to oxide charges. An N+ doped "inversion block", as shown in the figure, is made by using the polysilicon emitter structure without the implantation step for the internal base.

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Stabilized Lateral PNP Transistor

The polysilicon emitter and base processes allow, with no additional process complexity, the addition of a stabilized lateral PNP transistor which is insensitive to oxide charges. An N+ doped "inversion block", as shown in the figure, is made by using the polysilicon emitter structure without the implantation step for the internal base.

A process for fabricating the stabilized lateral PNP transistor is as follows: 1. Define the device area by an appropriate isolation (not shown). 2. Deposit a layer of undoped polysilicon. The polysilicon layer contacts the silicon in the device region. 3. Oxidize the polysilicon to form an implantation screen and an etch mask (not shown). 4. Implant boron of appropriate energy so that it is confined to the now P+ polysilicon layer 4. 5. Define the emitter and collector regions with a protective resist, and etch the oxide from the remaining polysilicon. 6. Etch the polysilicon down to the isolation in the region surrounding the transistor and down to the silicon

in the base region. 7. Oxidize the base region and the exposed edges of the polysilicon to form silicon dioxide layer 5. 8. Chemical vapor deposit (CVD) a thick SiO(2) layer, and reactive ion etch the base region to form thick

oxide sidewalls 6. 9. Deposit another undoped polysilicon layer.
10. Implant arsenic of appropriate energy to confine

it to the polysilicon and of sufficient dose

to convert it to N+ layer 7.
11. Form an oxide layer...