Browse Prior Art Database

Notched Channel IGFET

IP.com Disclosure Number: IPCOM000083519D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Dunlop, LJ: AUTHOR [+2]

Abstract

Described is a semiconductor insulated gate field-effect transistor (IGFET), in which threshold voltage shifts from normal operating voltages in dielectric gate isolation devices can be eliminated.

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Notched Channel IGFET

Described is a semiconductor insulated gate field-effect transistor (IGFET), in which threshold voltage shifts from normal operating voltages in dielectric gate isolation devices can be eliminated.

Operations of dual-dielectric devices in the pinch-off mode will create electric fields near the drain, sufficient to cause charges to be introduced into the dual- dielectric medium. These charges will become trapped at the interface of the two dielectric materials in trapping centers that exist at this interface. When the charges are electrons, the resultant negative charge requires a high-positive voltage on the gate electrode to invert the channel and hence requires a higher threshold voltage.

The figure illustrates such a FET device and comprises a body of silicon 10 with diffused source and drain regions 11 and 12 separated by gate region 13. Overlying the gate region 13 is a silicon dioxide layer 14 coated by silicon nitride 15 and a gate electrode 16. The silicon nitride layer 15 has been removed close to the source and drain regions 11 and 12, so that the gate electrode 16 is directly in contact with the upper surface of the silicon dioxide layer 14.

This notched gate structure prevents the accumulation of charges at the interface of layers 14 and 15. These charges instead go directly into the metal gate layer 16 and are conducted therefrom. In this way, no threshold voltage shift occurs while the desirable features of the silicon nitride...