T-Gate transistor with improved SOI body contact structure

Details T-Gate transistor with improved SOI body contact structure T-Gate transistor with improved SOI body contact structure

1998-08-07

2001-11-13

Abraham, Fetsum (Department: 2811)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S346000, C257S387000, C257S365000, C257S366000, C257S153000

Reexamination Certificate

active

06316808

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to transistors and particularly to an improved SOI body contract structure and process for creating such a structure in a manufacturing environment.
GLOSSARY
BC refers to a transistor of the body contacted type.
PC represents a shape that denotes the shape of poly-silicon structures.
RX represents a shape that denotes an opening in the field oxide, exposing active silicon.
Delta-W is the difference in finished manufactured dimension from the dimension drawn in the design.
Dog bone or DOG BONE means a contact shaped as shown in
FIG. 11
having a shape generally like an “H”, dog bone or femur.
Top-to-top “T” refers to a shape that generally denotes two “T”s which are mirror images of one another having their tops aligned in a generally parallel direction as illustrated by FIG.
10
. Trademarks: S/390 and IBM are registered trademarks of International Business Machines Corporation, Armonk, N.Y. U.S.A. and Lotus is a registered trademark of its subsidiary Lotus Development Corporation, an independent subsidiary of International Business Machines Corporation, Armonk, N.Y. Other names may be registered trademarks or product names of International Business Machines Corporation or other companies.
BACKGROUND
A standard, non body contacted transistor will be described as is usually drawn as shown in
FIG. 8
below. The areas labeled “S” and “D” represent the source and drain of the transistor. The gate is labeled with the word “Gate.” The effective width of this transistor is determined only by the width of the RX opening in the oxide, which is the outer rectangle in this illustration. Any Delta-W term is due to any bias on the oxide opening. The tolerances that have to be included when computing the width are the RX image size and any tolerance on Delta-W. By special use of an existing process, the standard transistor structure can be improved and is useful in making complex circuits such as those used by IBM's S/390 processors. The problem with prior and existing SOI “BC” type body contact structures is that the cause the effective transistor width to vary depending upon the overlay tolerance between the PC and RX levels.
SUMMARY OF THE INVENTION
The invention illustrated in top view in
FIG. 7
, and provides a transistor in which the top part of the transistor can be and preferably is the same as existing structures, but the bottom part is the mirror image of the top part, and in the bottom part, the effect of PC to RX overlay is reversed, an “UP” misalignment will make the device width larger, while a “Down” misalignment will make the device width smaller. This removes the overlay tolerance from the effective transistor width.


REFERENCES:
patent: 5405795 (1995-04-01), Beyer et al.
SOI Technology: IBM's Next Advance In Chip Design, Aug. 6, 1998, Internet—http://www.chips.ibm.com/bluelogic/showcase/soi/soipaper.pdf.

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