Browse Prior Art Database

Reduced Bit Line Capacitance in VMOS Devices

IP.com Disclosure Number: IPCOM000051528D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Kenney, DM: AUTHOR

Abstract

When polysilicon word and bit lines of a VMOS memory cell cross in the V-groove, the bit line capacitance is reduced substantially by providing a thick dielectric material in the V-groove between the word and bit lines by utilizing a spin-on technique.

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Reduced Bit Line Capacitance in VMOS Devices

When polysilicon word and bit lines of a VMOS memory cell cross in the V- groove, the bit line capacitance is reduced substantially by providing a thick dielectric material in the V-groove between the word and bit lines by utilizing a spin-on technique.

One of the VMOS memory cells, illustrated in the figure, includes a Psubstrate 10 having an Npocket 12, utilized as a storage node, and a P-type epitaxial layer 14. A thick layer of silicon dioxide 16 is formed over epitaxial layer 14, and a V-groove 18 is formed by known techniques in epitaxial layer 14 with its apex extending into the Npocket 12. A thin silicon dioxide layer 20 is provided over the walls of the V-groove 18, and a first polysilicon layer is applied to the surface of the existing structure.

Applied over the first polysilicon layer and into the V-groove, by employing a spinning technique, is an organic material, preferably polymethylsiloxane resin dissolved in n-butylacetate, as disclosed in the article, "A New Paint On Diffusion Source" by K. D. Beyer, Journal of the Electrochemical Society, October 1976, Vol. 123, No. 10, pages 1556-1560, which is then decomposed into silicon dioxide and densified by heat treatment. This latter silicon dioxide material is etched from the planar surface of epitaxial layer 14 to a desired depth into the V- groove to form the thick dielectric material 22.

The first polysilicon layer is appropriately etched by using known...