Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Responsive to non-optical – non-electrical signal
Reexamination Certificate
1998-10-15
2001-04-03
Mintel, William (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Responsive to non-optical, non-electrical signal
C257S254000, C257S417000, C257S418000, C257S420000, C438S050000, C438S052000
Reexamination Certificate
active
06211540
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor strain sensor, a method of processing the sensor, and a scanning probe microscope, particularly forming a Schottky-barrier by contacting metal to a beam portion of a probe made of a semiconductor substrate, detecting deflection of the probe as change of characteristic of the Schottky-barrier.
In the conventional scanning probe microscope (SPM), an exploring needle is attached at a free end of a probe, and deflection of the probe generated by movement up and down of the exploring needle response to raggedness of surface of a sample has been detected using optical interferometry of an optical polarization technique. However, there has been a problem that conventional microscope needs complex adjustment when using such an optical detecting method. On the other hand, recently a small-size, light-weight semiconductor strain sensor is widely used, which can output a deflection as an electric signal directly. The sensor is adopted for the probe of the SPM.
As shown in
FIG. 20
, for example, a probe-type semiconductor strain sensor comprises a cantilever arm portion (beam portion)
1
having a free end la formed by selectively etching a part of a semiconductor substrate
2
so as to have a U-shape and a gage portion
3
formed near a fixed end (root) of the cantilever arm portion
1
, and the gage portion
3
detects stress/strain at a portion of the cantilever in response to deflection of the free end
1
a
, and the strain is converted to an electric signal and outputted.
In the conventional semiconductor strain sensor, as described in Japanese Opened Patent No. 5-196458 for example, the gage portion is constructed with piezo resistance. As the electric resistance of the piezo resistance varies by applying stress, deflection is detected by measuring a resistance change of the piezo resistance at the resistance bridge circuit, such as Wheatstone bridge or the like.
As above-mentioned, when deflection of the probe is detected as stress/strain applied to piezo resistance, as the resistance rate of change for strain of the piezo resistance, namely voltage or current rate of change, is little and sensitivity is low, not only is a complex bridge circuit needed for the detecting, but an extremely accurate adjustment of each resistance constructing the resistance bridge is also needed.
An object of the present invention is to provide a semiconductor strain sensor solving the conventional above-mentioned problem by outputting deflection of the probe with high response speed as a large signal change, a method of processing the sensor, and a scanning probe microscope adopting the semiconductor strain sensor for the probe.
SUMMARY OF THE INVENTION
To solve the above-mentioned problem, the present invention is characterized by the following means:
(1) A semiconductor strain sensor of the present invention comprises a probe having a semiconductor probe supported like a cantilever, a first metal electrode having a Schottky junction on at least a surface of a beam portion of a semiconductor probe, a high concentration contact domain formed at surface of said semiconductor probe, and a second metal electrode connected to the high concentration contact domain.
(2) A method of processing a semiconductor strain sensor of the present invention comprises forming a semiconductor probe by etching a semiconductor substrate, forming a high concentration contact domain selectively at a surface of said semiconductor probe, selectively Schottky-joining the first metal electrode at a surface of a beam portion of said semiconductor probe, and contacting a second metal electrode to said high concentration contact domain.
(3) In the semiconductor strain sensor of the present invention, a thin film is formed on at least one of main surfaces of said semiconductor probe so that stress strain always appears on at least the Schottky junction.
(4) A scanning probe microscope of the present invention uses a semiconductor strain sensor where a Schottky junction domain is formed at a surface of a beam portion as a scanning probe.
According to the above-mentioned configuration (1), as stress/strain appears at a Schottky junction and the electric characteristic (diode characteristic) of the Schottky junction is sharply changed when the free end of the probe bends, deflection of the free end can be measured by detecting with a proper detecting circuit.
According to the above-mentioned configuration (2), a cantilever-type semiconductor stress/strain sensor having a Schottky junction can be produced easily.
According to the above-mentioned configuration (3), as stress/strain always appears without relation with displacement of the free end at Schottky junction and larger stress strain appears at the Schottky junction when the free end of the probe bends, the electric characteristic (diode characteristic) of the Schottky junction can be sharply changed. When a direction of deflection is set opposite to a direction of an exploring needle, the strain is measured with high accuracy as the angle between the surface of the sample and the exploring needle is about 90 degrees.
According to the above-mentioned configuration (4), as deflection of a probe is detected as a change of the electric characteristic of a Schottky junction, a surface shape of the sample can be observed with high sensitivity.
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patent: 5632841 (1997-05-01), Hellbaum et al.
patent: 5713667 (1998-02-01), Alvis et al.
patent: 5838005 (1998-11-01), Majumdar et al.
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patent: 695927A3 (1996-02-01), None
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Despont Michel
Ichihara Susumu
Shimizu Nobuhiro
Shirakawabe Yoshiharu
Takahashi Hiroshi
Adams & Wilks
Mintel William
Seiko Instruments Inc.
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