Semiconductor device manufacturing: process – Having diamond semiconductor component
Reexamination Certificate
1995-12-26
2001-02-06
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Having diamond semiconductor component
C438S969000
Reexamination Certificate
active
06184059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diamond-metal junction product in which a diamond semiconductor and a metal are integrated through an ohmic junction.
2. Description of the Related Art
In general, diamond has a large band gap of about 5.5 eV and a large carrier mobility (1800 cm
2
/V·S for electrons and 1600 cm
2
/V·S for holes), as well as a large thermal conductivity of about 20 W/cm·k. In addition, diamond exhibits a very high level of hardness and, hence, superior wear resistance. Thus, diamond possesses various advantageous properties which can never be offered by other materials.
In recent years, remarkable progress has been achieved in the technique for synthesizing diamond from gaseous phases, and it is now possible to form a diamond film by chemical vapor deposition (CVD).
Studies also have been made to develop a technique for producing semiconductors by doping diamond crystals with impurities. Shiomi et al. reported that a field effect transistor can be produced by forming, on an artificial diamond substrate, a diamond film containing boron as an impurity by a vapor synthesis technique and then forming Schottky junction metal and ohmic junction metal.
Hitherto, however, it has been difficult to form metal electrodes on diamond crystal by diamond-metal junction with a high degree of reproducibility of the characteristics of the product. Namely, characteristics of a diamond-metal junction material largely vary according to factors such as the conditions for forming the diamond, the conditions of processing after formation of the diamond and the methods of forming the electrodes.
For instance, whether the type of junction formed is an ohmic junction or a Schottky junction depends on whether a methane-hydrogen type gas or a carbon monoxide-hydrogen type gas is used as the material gas in forming the diamond. It is also known that a metal junction which has exhibited an ohmic nature is changed into a metal junction exhibiting a Schottky nature when diamond crystal is scrubbed with a chromic acid mixed solution. Characteristics also vary largely depending on whether the metal electrode is formed to make a point conduct or evaporation-deposited on the diamond layer.
Thus, it has been difficult to obtain a product having metal electrodes by a diamond-metal junction with a high degree of reproducibility.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a diamond-metal junction product which exhibits excellent ohmic characteristics.
A second object of the present invention is to provide ohmic junction electrodes which can be formed with high degree of reproducibility.
A third object of the present invention is to provide a diamond-metal junction product in which an ohmic junction is formed between a semiconductor diamond layer and a metal layer through the intermediary of a graphite layer having a thickness of at least 12 Å.
A fourth object of the present invention is to provide a diamond product comprising a stabilized outer surface of graphite formed on a diamond layer, wherein said outer surface of graphite has a thickness of at least 12 Å.
A fifth object of the present invention is to provide a diamond product comprising a semiconductor diamond layer having an outer surface region of graphite in contact with a metal electrode to form an ohmic junction with the electrode, wherein the outer surface region has a thickness of at least about 12 Å.
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Hirabayashi Keiji
Matsushima Masaaki
Canon Kabushiki Kaisha
Elms Richard
Fitzpatrick ,Cella, Harper & Scinto
Lebentritt Michael S.
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