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■ Semiconductor Pressure Sensitive Device, Jpn. Pat. No. 46-5096 ■ Japanese Patent
Application SHO 43-9167 [Phase] Akira 43 (1968 19 Feb. 15 [Phase] Inventor Nobuhiko
Mizushima 3-11 Midoricho, Musashino City No. 9 Nippon Telegraph and Telephone Corporation
Electric Corporation Telecommunications Research Institute Inc. [Inc.] Inventor Ariyoshi Sakai
Musashino City Midoricho 3-9-11 Nippon Telegraph and Telephone Corporation
Telecommunications Research Institute Telecommunications Research Institute
Telecommunications Research Institute Ubiquitous Akira Okamoto Musashino City Midoricho 3Chome 9-11 Nippon Telegraph and Telephone Corporation Telecommunications Research
Institute 0 Applicant Nippon Telegraph and Telephone Public Corp. Selected Representative
Nippon Telegraph and Telephone Public Corp. Musashino Telecommunication Research
Laboratories General Manager Information Patent Department [Phase] cited document JP-B-4211765 (Jp, B1) NHK Technical Research Volume 18 No. 4 259 Page 262: Proceedings of IEEE
February 1966, pages 317 to 318
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the
present invention, a is a side view or a plan view, and FIGS. 2 and 3 are characteristic diagrams of
the embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor
pressure sensitive device utilizing the pressure effect exhibited by a Schottky junction formed by
the contact of a semiconductor and a metal that has been made to a deep level using radiation. A
large number of pressure-sensitive devices using solids are known conventionally, but those
using ferroelectrics do not have sufficient sensitivity, and they have extremely high impedance
when used in combination with transistor ratings. There is a drawback. In addition, a low
impedance element is required in the electro-acoustic transducer of the current telephone. For
this reason, a semiconductor pressure-sensitive element that exhibits pressure sensitivity in a low
impedance region is required, and an element using a pn junction is considered, and in this
element, at least 108 dyne / to obtain a detectable output. The pressure of about am 2 or more is
necessary, and it is insufficient as a temptation. This is because a device utilizing a pn junction
essentially can not transmit a pressure to a junction region in the semiconductor because a p or n
type semiconductor layer of 1 μm or more is essentially required. Furthermore, since this
element requires an ohmic electrode, processing such as an alloy or sintering must be performed,
which complicates the process and structure. In addition, pressure-sensitive devices having a
transistor structure are considered promising, but the structure is complicated and expensive,
and the pressure sensitivity is not sufficient. The present invention provides an electro-acoustic
transducer which has an extremely simple structure, high pressure sensitivity, and low
impedance and stable operation, and metal is applied to the semiconductor in which the internal
lattice atoms are displaced by irradiating the radiation. A semiconductor Schottky junction is
formed, or a Schottky junction is formed, and then radiation is applied to displace lattice atoms in
the semiconductor to impart pressure sensitivity. The element of the present invention has a low
loss of stress when pressurized because of the ability to use extremely thin and hard metals, and
therefore it can transmit 100% of the pressure to the junction region in the semiconductor
generated directly under the metal, so it is pressure sensitive. In addition, since the element of
the present invention uses a metal-semiconductor junction and the pressure side is metal, an
ohmic electrode is not required, and a metal film that forms a junction can be used immediately
as an electrode. This makes it possible to simplify the structure and reduce the cost. In addition,
since the element of the present invention is damaged in the junction region inside the
semiconductor by radiation, that is, rll11111EndPage: pressure sensitivity is enhanced by
displacement of lattice atoms, it is possible to use a metal-semiconductor junction. Together with
the advantages, it is a highly sensitive, low impedance, stable pressure sensitive element.
Next, it will be described in more detail with reference to the drawings. FIG. 1 is a view showing
the structure of the element used in the embodiment of the present invention, and FIG. 1 a is a
side view, FIG. 1 is a plan view, 1 is a semiconductor substrate, 2 is a mesa, 3 is a vapor deposited
metal film Pressure is applied to this surface. 4 is an ohmic contact to the semiconductor
substrate 1. In the embodiment, silicon is used as a semiconductor and tungsten is used as a
vapor deposition metal. A silicon wafer with a resistivity of 0.01 Ω-儂 is chemically polished to a
thickness of 500 μm, Au-8b (Sb-Q, 5%) is deposited on one side and fired to form an ohmic
contact, and tungsten on the other side is 500 Vacuum deposition was performed to a thickness
of 4 to form a Schottky junction. The processed wafer was cut into 3 mi × 3 mm bellets, and the
element was formed by mesa-etching the tungsten side to a diameter lim. The element was
irradiated with radiation from a tungsten side at an intensity of 1.1 × 10 5 roentgens / hour
using a CO 60 radiation source. 2 and 3 show the forward and reverse voltage-current
characteristics of this device. FIG. 2 shows the characteristics after irradiation for 360 hours, and
FIG. 3 shows the characteristics after 530 hours with the applied pressure as a parameter. The
element before irradiation of radiation showed no change in the voltage-current characteristics at
a uniaxial pressure of about 108 dyne / cIrL ′ ′. On the other hand, according to the present
invention, as can be seen from FIG. 2, after irradiation for 360 hours, when the applied pressure
is changed from 5xlO 'dyne / cIrL2 to 2x107 dyne / cIn "at reverse bias voltage 4v of the
junction, the reverse current is (4) shows a 7-fold change from 75 mA to 0.053 mA, and as can
be seen from FIG. 3, after 530 hours of irradiation, the reverse current is 0. 5 at the same applied
pressure change at a reverse bias voltage of 5 v. It has been found that the device of the present
invention exhibits a change of about 10 times from 007 mA to 0.07 mA, and the element of the
present invention shows a change in current with respect to a change in applied pressure, that is,
a pressure sensitivity is extremely high. Although the embodiment in which the radiation is
irradiated after the formation of the Schottky junction has been described, the present invention
is directed to a method in which the semiconductor is irradiated with radiation and then the
shock is generated [111111]. As a matter of course that has the effect of 聞様. The radiation
source is not limited to the above Co60 as long as it causes displacement of lattice atoms in the
semiconductor. The device of the present invention obtained as described above is compared
with the conventional device. The reverse current in the conventional pn junction device most
typically changes by about 100% with respect to the applied pressure of 10 9 dyne / crn 2.
This is a value derived directly from the pressure dependence of the band gap of the
semiconductor. Therefore, the device of the present invention has a pressure sensitivity which is
about three to four digits greater than that of the conventional pn junction device. Moreover, in
the transistor pressure-sensitive element currently regarded as most promising as a solidified
microphone, the rate of change of the above-mentioned pn junction element is further amplified
by the transistor, and the applied pressure is usually 10 7 to 1 8 dyne / crIL 2 On the other hand,
it has been confirmed by experiments that the current changes by about 100%. However, the
transistor pressure sensitive element has a problem in the reproducibility of pressure sensitivity.
Therefore, the device of the present invention has a pressure sensitivity which is more than an
order of magnitude greater than that of the conventional pn junction device. As described above,
since the element of the present invention is a diode having a particularly simple structure, it is
an excellent pressure-electric conversion element, which is stable in operation and low in cost.
Since the highly sensitive pressure effect of the element of the present invention is due to the
displacement of lattice atoms generated in the junction region of the semiconductor by the
radiation irradiation, the pressure sensitivity also to the general pn junction element by the
radiation irradiation It is possible to raise However, when using a pn junction, as described
above, the thickness needs to be greater than that of the p or n-type layer, so that the radiation
absorption by this layer is large, and the effective displacement of lattice atoms in the junction
region In order to cause irritability, high intensity radiation must be irradiated for a long time,
which is not practical. For example, when radiation is applied to a pn junction element having a 7
μ n-type layer on a p-type substrate under the same conditions as in the above embodiment, the
voltage-current characteristics due to pressure are Little change is observed. On the other hand,
since the device of the present invention is a metal-semiconductor Schottky junction device, the
above-mentioned defects can be eliminated since the junction region is directly below the metal.
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