Browse Prior Art Database

Bipolar One Device Random Access Memory Cell

IP.com Disclosure Number: IPCOM000045600D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

El-Kareh, B: AUTHOR [+3]

Abstract

A bipolar dynamic random-access memory cell having one transistor and a serially connected storage capacitor is fully isolated by a dielectric medium so as to provide enhanced storage capacitance and increased immunity to radiation induced errors. A bipolar one-device cell is described in U.S. Patent 3,876,992.

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Bipolar One Device Random Access Memory Cell

A bipolar dynamic random-access memory cell having one transistor and a serially connected storage capacitor is fully isolated by a dielectric medium so as to provide enhanced storage capacitance and increased immunity to radiation induced errors. A bipolar one-device cell is described in U.S. Patent 3,876,992.

As shown in the figure, a P type semiconductor substrate 10 has formed thereon a thin layer 12 of dielectric material, preferably silicon dioxide, and a layer of single crystal N type silicon 14. The single crystal silicon layer 14 and the dielectric layer 12 may be made by any known method, such as disclosed in U.
S. Patent 3,919,060 or in IBM Technical Disclosure Bulletin 24, 11A, 5458-5459 (April 1982).

Trenches 16 are formed through silicon layer 14 and silicon dioxide layer 12 into substrate 10. The walls and floors of trenches 16 are oxidized to form silicon dioxide layers 18. Using, e.g., a dry etch technique, the silicon dioxide layers 18 are then removed only from the floor of trenches 16. Trenches 16 are filled with heavily doped P type polysilicon 20. A silicon dioxide layer 22 is grown on the surface of the single crystal silicon substrate 10. Simultaneously, a thicker oxide layer 22' is grown over the polysilicon 20 due to a higher growth rate.

A P type region 24 is formed in silicon layer 14, and an N type region 26 is formed within P type region 24, with region 26 being the emitter, region 24 bein...