Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – Insulated gate formation
Reexamination Certificate
1997-12-19
2001-06-05
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
Insulated gate formation
C438S592000, C438S621000, C438S647000
Reexamination Certificate
active
06242330
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to semiconductor devices and, more particularly, to a process for breaking silicide stringers extending between silicide areas of different active regions on a semiconductor device.
BACKGROUND OF THE INVENTION
Over the last few decades, the electronics industry has undergone a revolution by the use of semiconductor technology to fabricate small, highly integrated electronic regions. The most common semiconductor technology presently used is silicon-based. A large variety of semiconductor devices have been manufactured having various applications in numerous disciplines. Such silicon-based semiconductor devices often include metal-oxide-semiconductor (MOS) transistors, complimentary MOS (CMOS) transistors, bipolar transistors, BiCMOS transistors, etc.
Each of these semiconductor devices generally include a semiconductor substrate on which a number of transistors are formed. The particular structure of a given transistor can vary between transistor types. For example, MOS transistors generally include source and drain regions and a gate electrode which modulates current between the source and drain regions. Bipolar transistors generally include a base a collector, and an emitter. In addition to the active regions (e.g., source regions, drain regions, gate electrodes, bases, emitters, collectors, etc.) of the transistors, both bipolar and MOS transistors often include polysilicon lines, active regions which typically run over regions of the substrate, such as field oxide regions, and interconnect various portions of the region.
The various active regions on a semiconductor device are typically interconnected by metal lines. In most cases, a silicide is formed over some or all of the active regions in order to facilitate contact between the active regions and subsequent metal lines. The silicide areas also serve to reduce the sheet resistance of the active regions. Silicide areas are typically formed by depositing a layer of metal, such as tungsten, cobalt or titanium, over the substrate and annealing the wafer, typically in a two-step process. During the annealing process, the deposited metal reacts with underlying silicon and forms a metal silicidation layer.
It is typically desirable to minimize the resistivity of the silicide areas. The resistivity of the silicide areas generally depends upon the temperature at which the silicide reaction occurs as well as the type of metal used to form the silicide areas. Generally, the temperature of the reaction is a first order variable in the resultant resistivity. Higher silicide reaction temperatures result in silicide areas having lower resistivity. In conventional silicidation techniques, using elevated temperatures can however result in the formation of deleterious silicide stringers, which in some instances can extend between the silicide areas of adjacent active regions and electrically couple the active regions.
SUMMARY OF THE INVENTION
The present invention provides a process for breaking silicide stringers extending between silicide regions of different active regions on a semiconductor device. A semiconductor fabrication process, in accordance with one embodiment of the invention, includes forming two adjacent silicon active regions on a substrate and forming a metal layer over the two adjacent silicon active regions. The metal layer is then reacted with the silicon active regions to form a metal silicide on each silicon active region. This silicide reaction also forms one or more silicide stringers which extend from each silicon active region. Finally, at least part of each silicide stringer is removed. During the formation of the silicide stringers at least one silicide stringer may be formed which bridges the metal silicide over one of the silicon regions and the metal silicide over the other silicon region. In such circumstances, the removal process may, for example, break the silicide stringer and electrically decouple the two silicon active regions. The two silicon active regions may, for example, be a gate electrode and an adjacent source/drain region. As another example, the two adjacent active regions may be two nearby polysilicon lines.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.
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Cheek Jon
Hause Fred
Wristers Derick J.
Advanced Micro Devices , Inc.
Chaudhuri Olik
Louie Wai-Sing
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