Browse Prior Art Database

Composite Gate Electrode for MOSFET

IP.com Disclosure Number: IPCOM000103512D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 61K

Publishing Venue

IBM

Related People

Chao, HH: AUTHOR [+3]

Abstract

In MOSFET devices, a metal or metal silicide conductive layer is the gate electrode which is deposited over an underlying thermal SiO2 gate insulator layer. However, degradation of the gate insulator layer often occurs from the metal or metal silicide contact layer. In order to prevent this, a silicon-rich oxide layer is located between the underlying SiO2 gate insulator layer and the overlying metal or metal silicide contact layer.

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Composite Gate Electrode for MOSFET

      In MOSFET devices, a metal or metal silicide conductive layer
is the gate electrode which is deposited over an underlying thermal
SiO2 gate insulator layer.  However, degradation of the gate
insulator layer often occurs from the metal or metal silicide contact
layer.  In order to prevent this, a silicon-rich oxide layer is
located between the underlying SiO2 gate insulator layer and the
overlying metal or metal silicide contact layer.

      In the figure, a MOSFET 10 includes n+ regions 12 acting as
source and drain regions, and overlying thermal SiO2 gate insulator
layer, the intermediate silicon-rich oxide layer 16, and the top
contact layer 18, which is a metal or metal silicide layer.  Layer 16
serves as a buffer between the contact layer 18 and the gate
insulator layer 14 and minimizes degradation of the insulator layer
14 by the metal or metal silicide layer 18 in contact.  The composite
of layers 14 and 16 has a high yield and will control breakdown
characteristics.  Electrically, intermediate layer 16 is the
equivalent of a very thin oxide layer which does not change the
metal-semiconductor work function difference.

      Layer 16 is very conductive and, in actual circuit operation,
the buildup of space charge causes an almost total collapse of the
electric field in this layer which gives a very small voltage drop.
The net result is that the threshold voltage is almost the same as
the conventional structur...