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Field Effect Transistor Gate Structure

IP.com Disclosure Number: IPCOM000079774D
Original Publication Date: 1973-Sep-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Dalal, HM: AUTHOR [+2]

Abstract

Gate dielectric layers are normally very thin, relative to the surrounding field insulation layer, in order to achieve relatively low-threshold voltages. However, any reaction between the date insulating layer and the conductive gate produces gate shorts and instability. For example, aluminum is unstable in contact with silicon nitride, having a tendency to form aluminum nitride. Another requirement for a stable gate metal is that the work function of the metal should be as high as possible. This condition is desirable, since under negative bias a metal acts as a source of electrons, and higher work functions will increase the energy barrier for the charge transport to the dielectric, thereby increasing the stability especially under negative bias.

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Field Effect Transistor Gate Structure

Gate dielectric layers are normally very thin, relative to the surrounding field insulation layer, in order to achieve relatively low-threshold voltages. However, any reaction between the date insulating layer and the conductive gate produces gate shorts and instability. For example, aluminum is unstable in contact with silicon nitride, having a tendency to form aluminum nitride. Another requirement for a stable gate metal is that the work function of the metal should be as high as possible. This condition is desirable, since under negative bias a metal acts as a source of electrons, and higher work functions will increase the energy barrier for the charge transport to the dielectric, thereby increasing the stability especially under negative bias.

This gate structure is a thin layer of Si(3)N(4) over the gate region of a field- effect transistor having a thickness on the order of 300-1,000 angstroms, and an overlying conductive layer of chromium. Since chromium is stable with Si(3)N(4), the resultant gate structure is stable and radiation hard.

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