Browse Prior Art Database

Integration Technique for Closed Field Effect Transistors

IP.com Disclosure Number: IPCOM000081096D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Cady, RC: AUTHOR [+2]

Abstract

This technique provides a method of integrating closed, or circular, field-effect transistors (FET's) into an array which may be used in read-only or nonvolatile read-mostly memories, as well as in other applications.

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 60% of the total text.

Page 1 of 2

Integration Technique for Closed Field Effect Transistors

This technique provides a method of integrating closed, or circular, field- effect transistors (FET's) into an array which may be used in read-only or nonvolatile read-mostly memories, as well as in other applications.

Fig. 1 shows a portion of an array including four circular FET's, each having a central drain region enclosed by a source region 12 and having a conductive gate electrode 14. In order to interconnect the devices there is provided a buried subdrain diffusion 16, which extends in a direction orthogonal to gate electrodes 14 and is isolated from the substrate as well as the source regions 12. Figs. 2 and 3 show cross sections of a single FET and further illustrate the integration technique.

A typical manufacturing process could include the steps of:
1) Surface deposition of strips of a relatively slow diffusing

N-type impurity, such as arsenic, on the surface of a P-type

semiconductor wafer 18.
2) Surface deposition of dots of a faster diffusing impurity,

such as phosphorous, over positions corresponding to the

enclosed drain regions.
3) Epitaxially growing a thin P-type semiconductor layer 20 on

wafer 18. As layer 20 is grown, both previously deposited

impurities will diffuse upward at their respective rates

forming buried subdrain 16 and N-type projections 22.
4) Diffusing circular source and drain regions in the surface

of epitaxial layer 20 by standard techniques. The presence

of N-type dif...