Browse Prior Art Database

Two Dimensional PNP Transistor

IP.com Disclosure Number: IPCOM000051873D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Beresford, R: AUTHOR

Abstract

In a regular double-diffused pnp, as shown in Fig. 1, the base dose is implanted into the top surfaced silicon 12 of substrate 10, then driven in to counter-dope the implanted collector region 18, and contacted by the buried n+ sublayer 14. In the two-dimensional pnp shown in Fig. 2, the etch mask at this point is enlarged to insure that the oxide isolation 16 is exposed on three sides of the collector 18. The oxide 16 is then etched down below the silicon surface to expose a silicon sidewall.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 64% of the total text.

Page 1 of 2

Two Dimensional PNP Transistor

In a regular double-diffused pnp, as shown in Fig. 1, the base dose is implanted into the top surfaced silicon 12 of substrate 10, then driven in to counter-dope the implanted collector region 18, and contacted by the buried n+ sublayer 14. In the two-dimensional pnp shown in Fig. 2, the etch mask at this point is enlarged to insure that the oxide isolation 16 is exposed on three sides of the collector 18. The oxide 16 is then etched down below the silicon surface to expose a silicon sidewall.

For a recessed-oxide (ROX) type process, this sidewall will be slanted considerably, and an implant drive-in step may be used to make the base region. For a double-diffused implant-type process, the steep sidewall will require a diffusion step to make contact to the n+ sublayer 14. In either case, base contact is assured, and the doping parameters may be selected according to the desired base-width. In a regular double-diffused pnp, for example, a minimum drive-in time is determined by the requirement that the vertical diffusion equal or exceed the epi thickness. This constraint is removed in the two-dimensional pnp by exposing the silicon sidewall, and greater flexibility in determining the device base-width may be possible. Figs. 2 and 3 illustrate the device cross-sections after the base is in place.

The primary advantage gained in the new structure is that the collector can now extend under the injector to within about one base-width of th...