Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-02-22
2001-03-20
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S520000, C438S931000, C438S522000
Reexamination Certificate
active
06204160
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to forming electrical contacts and junctions in silicon carbide. More specifically, but without limitation thereto, the present invention relates to incorporating dopants in silicon carbide from a gaseous ambient and concurrently activating the dopants by photo illumination.
The semiconductor silicon carbide (SiC) enjoys wide interest due to its applicability in high temperature, high power and photonic devices and circuits. However, greater difficulties in fabrication relative to silicon have prevented the full realization of its capabilities in these applications. The high melting point and limited diffusion of impurities in silicon carbide have greatly limited the use of ion implantation and furnace annealing commonly employed in the silicon microelectronics industry as a means of incorporating and activating dopants. These fabrication techniques are desirable for producing self-aligned field-effect transistor structures for use in discrete power devices and digital logic circuits. Ion implantation of n-type dopants, such as arsenic, in SiC has met with limited success; however, it requires annealing temperatures in excess of 1300° C. for activation, and ion implantation and annealing of p-type dopants has demonstrated only about 5% activation, insufficient for practical device fabrication. Alternative techniques are therefore desired to obtain a greater degree of dopant activation in SiC, particularly with p-type dopants.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming the problems described above, and may provide further related advantages. No embodiment of the present invention described herein shall preclude other embodiments or advantages that may exist or become obvious to those skilled in the art.
A method for making electrical contacts and junctions in silicon carbide of the present invention concurrently incorporates and activates dopants from a gaseous ambient. The low temperature processing of the present invention prevents the formation of crystalline defects during annealing and preserves the quantitative chemical properties of the silicon carbide. Improved activation of dopants incorporated in a silicon carbide sample is provided for making the electrical contacts and junctions.
An advantage of the method for making electrical contacts and junctions in silicon carbide of the present invention is that the formation of step bunching and other crystalline defects may be avoided.
Another advantage is that the stoichiometry of the SiC may be preserved.
Still another advantage is that volatile reaction of molten SiC with the atmosphere may be avoided.
Yet another advantage is that the method of the present invention concurrently incorporates and electrically activates dopant impurities at a low temperature relative to current methods.
The features and advantages summarized above in addition to other aspects of the present invention will become more apparent from the description, presented in conjunction with the following drawings.
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Ramirez Ayax D.
Russell Stephen D.
Everhart Caridad
Fendelman Harvey
The United States of America as represented by the Secretary of
Ward James A.
Whitesell Eric James
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