Active solid-state devices (e.g. – transistors – solid-state diode – Schottky barrier
Reexamination Certificate
1999-08-10
2002-09-17
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Schottky barrier
C257S471000, C257S472000, C257S485000, C257S486000
Reexamination Certificate
active
06452244
ABSTRACT:
DESCRIPTION
Film-like composite structure and producing method thereof
1. Technical Field
The present invention relates to a film-like composite structure having a plurality of minute areas of different Schottky currents or Schottky barrier heights and producing method thereof.
2. Background Art
In a semiconductor device, various kinds of interfaces play a fundamental role for operation of the device. At the interfaces, there are potential variations and occur thermal non-equilibrium states of carriers. Among them, at a interface of a metal and a semiconductor, a potential barrier, namely, so-called Schottky barrier is known to occur. The Schottky barrier has a rectifying action. A rectifying metal-semiconductor junction, so-called Schottky junction has been used as a Schottky barrier diode, a Schottky gate transistor or the like, and constitutes a basis of semiconductor devices.
Although it is very important to control a Schottky barrier formed at a metal-semiconductor interface from design and production of the device points of view, a unified understanding of the formation mechanism of the barriers has not yet been obtained. In addition, upon connecting an electrode to an device, there is a metal-semiconductor interface. Accordingly, a non-rectifying ohmic contact is required to obtain, however, in general, it is extremely difficult to circumvent completely a rectifying barrier. Notwithstanding whether the Schottky barrier is used or the ohmic contact is used, it is essential to control the potential barrier at the metal-semiconductor interface. However, so far, there has been formed an interface level inevitably at the interface, accordingly it has been said that it is very difficult to control the Schottky barrier.
Further, when an interface is being formed, due to lattice defects, existence of impurities, interfacial reactions or the like on a surface of a semiconductor, it is difficult to form a uniform interface, that also makes difficult to control the potential barrier at the metal-semiconductor interface. This is partly due to an insufficient understanding of the formation process of the interface. To solve the aforementioned problem, an atomic level understanding and control of the formation process of the interface are essential.
As described above, so far, as Schottky barrier diodes, Schottky gate transistors or the like, various kinds of electronic devices which employ the Schottky barrier have been used. Those employ only an overall Schottky barrier at the metal-semiconductor interface, accordingly their usage has been restricted to such devices that control a current or an amount of electric charges by the whole interface.
Accordingly, it is demanded to, by controlling a potential barrier at a metal-semiconductor interface, produce an interface of a uniform potential barrier, and in addition to make an interface having areas of nanometer level of different potential barriers exist. If those were materialized, it would be expected that they would enable to produce minute semiconductor devices of nanometer level and develop further new functional devices such as mesoscopic devices or the like. However, until now, such an electronic device has not been found out.
On the other hand, as to the value of the Schottky barrier height itself, even for the same metal-semiconductor junctions, different values are reported depending on the state of the interface or the like. For example, in a NiSi
2
/Si(111) junction system, between the case where (111) face of Si and (111) face of NiSi
2
satisfy a complete epitaxial relation, and the case where they are in a twin relation, different values are reported for the value of the Schottky barrier height. In specific, whereas the former one is 0.65 eV, the latter one is 0.79 eV (R. T. Tung, Phys. Rev. Lett. 52, 461 (1984)). This is considered that there is difference between arrangements of Ni atoms and Si atoms at a interface and, this difference leads to the difference of the Schottky barrier height.
Although the aforementioned report shows that the Schottky barrier height differs depending on the difference of the interface structure, it postulates that the Schottky barrier heights in the measured junction area of the metal-semiconductor are the same. This only shows the difference of the Schottky barrier heights at the different metal-semiconductor junctions. Therefore, this does not show that, in a minute junction area of the metal-semiconductor, a plurality of areas of different Schottky barrier height exist. However, such a structure does not exceed the range of electronic devices using the conventional Schottky barrier.
As described above, the electronic devices of the conventional Schottky barrier make use of only the overall Schottky barrier height at the metal-semiconductor interface and a film structure where interfaces of different potential barrier exist with the area of nanometer level has not yet been obtained. From such a background, upon making semiconductor devices minute at the level of nanometer or realizing a new functional device, it is strongly demanded to control the potential barrier at the metal-semiconductor interface. In addition to preparation of the interfaces of a uniform potential barrier, a film-like composite structure where interfaces of different Schottky current and Schottky barrier height coexist at the area of nanometer level is demanded.
An object of the present invention is to provide, through realization of the control of the potential barrier of the metal-semiconductor interface, a film-like composite structure where a plurality of nanometer level areas of different Schottky currents and Schottky barrier heights exist in a minute area, and a producing method of the same.
DISCLOSURE OF INVENTION
A film-like composite structure of the present invention comprises a semiconductor layer having a flat portion, a metallic layer of a thickness of 20 nm or less formed on the flat portion of the semiconductor layer, and an intermediate layer of a thickness of 10 nm or less which is partly interposed between the semiconductor layer and the metallic layer and consisting of an insulator, a metal different from the metallic layer or a semiconductor different from the semiconductor layer. Here, the metallic layer has a first area contacting directly with the semiconductor layer, and a second area where the intermediate layer is interposed between the semiconductor layer and the metallic layer, and the Schottky barrier height is different from that of the first area, the first area and the second area each having an essentially uniform Schottky barrier height in each area, respectively.
In the film-like composite structure of the present invention, the first area and the second area are characterized in that the respective interfaces in the each area have an essentially uniform potential barrier, respectively.
In the film-like composite structure of the present invention, the second area can be disposed partly to the whole area of the metallic layer, for example, depending on the desired device pattern. The second area is formed according to the shape of the intermediate layer. For the specific shape of the intermediate layer, an island-like body of the maximum diameter of 100 nm or less, or a belt-like body of a width of 100 nm or less.
A producing method of a film-like composite structure of the present invention comprises a step of forming, on a semiconductor layer with a flat portion, an intermediate layer of a thickness of 10 nm or less consisting of an insulator, a first metal or a semiconductor different from the semiconductor layer, in an island-like or belt-like shape, and a step of forming, on the semiconductor layer having the intermediate layer, a metallic layer of a thickness of 20 nm or less consisting of a second metal different from the first metal, wherein on the semiconductor layer, a first area where the metallic layer and the semiconductor layer contact directly, and a second area where the intermediate layer is interposed between the metallic layer and the semiconductor layer, an
Miura Tadao
Sumiya Touru
Tanaka Shun-ichiro
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Japan Science and Technology Corporation
Lee Eddie
Nguyen Joseph
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