JP2002340830A - Hydrogen gas detecting device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen gas detecting device capable of accurately, quickly and easily detecting a leakage of the hydrogen gas even under the non-oxygen environment such as the inert gas atmosphere and vacuum. SOLUTION: This hydrogen gas detecting device is provided with a first and a second insulating films 20 and 21 provided in a surface of a semiconductor substrate 10, a first detecting part 50 provided on the first insulating film 20 and having a first Pd thin film 30 mainly composed of Pd, and a second detecting part 51 provided on the second insulating film 21 and having a second Pd thin film 31 mainly composed of Pd and an electrode 43 formed of a conductor ohmic-connected to a back surface of the semiconductor substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen gas detecting device for detecting the concentration of hydrogen gas in an inert gas atmosphere or in a vacuum such as outer space under an oxygen-free environment.

[0002]

2. Description of the Related Art There are various types of hydrogen gas sensors such as a catalytic combustion type, a semiconductor type, and a solid electrolyte type.
None of these conventional hydrogen gas sensors operate in an oxygen-free environment such as an inert gas atmosphere or a vacuum, and operate only in the presence of an oxygen-containing gas such as air.

[0003] Using a conventional hydrogen gas sensor, there is a possibility of generation in a container for storing compressed hydrogen gas or a container for storing liquefied hydrogen which is installed in an explosion-proof atmosphere filled with an inert gas such as nitrogen or helium. A conventional detection method employed for detecting a certain leakage of hydrogen gas will be briefly described with reference to FIGS. The compressed hydrogen gas or liquefied hydrogen storage container 110 is surrounded by a container 120 filled with an inert gas to prevent explosion. A sampling pipe 130 communicates with the inert gas container 120, and a sample gas is collected by the hydrogen gas sensor 160 via the pipe 130. Reference numeral 131 denotes an air introduction pipe, reference numeral 140 denotes a suction pump, reference numerals 150 and 151 denote flow control valves, and reference numeral 152 denotes a mixer.

In such a conventional leak detection method, a part of the atmosphere in a container 120 filled with an inert gas is suctioned by a suction pump 140 to a mixer 152 via a sampling pipe 130 and a flow control valve 150. And lead. In addition, almost simultaneously with the start of the sampling of the hydrogen gas, the flow control valve 151 is opened, and air is introduced into the mixer 152 via the pipe 131. In the mixer 152, after the sampling gas and air are sufficiently mixed, the mixed gas becomes a mixed gas and is guided to the conventional hydrogen gas sensor 160 to detect hydrogen gas leakage.

FIG. 10 is a schematic diagram showing another conventional method for detecting hydrogen gas leakage in a liquefied hydrogen storage container installed in an explosion-proof atmosphere. The compressed hydrogen gas or liquefied hydrogen storage container 111 is surrounded by a container 120 filled with an inert gas via a heat insulating material 121. The sampling line is substantially the same as the method described above.

[0006]

However, the above-mentioned conventional hydrogen gas leak detection method has the following problems (1) to (3).

(1) Since the gas is sucked by the pump through the sampling pipe, it takes a long time to detect a gas leak when the gas leaks.

(2) If there are many places where leakage detection is desired, it is necessary to install a large number of suction pipes and suction pumps, and the number of points that can be detected is limited due to space limitations.

(3) In an oxygen-free environment where there is no oxygen-containing atmosphere, such as in space, on the moon, and on other planets, oxygen gas must be separately supplied to the sensor.

FIG. 11 shows another conventional example. The hydrogen storage container 111 is housed in a vacuum heat insulating container 122.
In this leak detection method, since the place where the hydrogen gas may leak is a vacuum, the atmosphere cannot be sampled. For this reason, a pressure gauge 161 is attached to the vacuum insulated container 122 to detect an increase in the internal pressure of the container 122. However, in this method, it is determined whether the increase in the internal pressure is due to leakage of hydrogen gas from the hydrogen storage container 111 or due to the intrusion of the atmosphere into the vacuum insulation container 122. There is a drawback that you can not do.

In addition, the conventional hydrogen gas sensor has an upper limit of the detection sensitivity of about 1000 ppm. Therefore, when it is necessary to detect even higher concentration hydrogen, the sampling gas is sufficiently introduced before being introduced into the sensor. There is also a problem that it needs to be diluted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is capable of accurately, quickly and easily leaking hydrogen gas even in an oxygen-free environment such as an inert gas atmosphere or a vacuum. It is an object of the present invention to provide a hydrogen gas detection device capable of detecting a hydrogen gas and a method of manufacturing the same.

[0013]

A hydrogen gas detector according to the present invention is a hydrogen gas detector for detecting the concentration of hydrogen gas in an oxygen-free environment. The first and second hydrogen gas detectors are provided on the surface of a semiconductor substrate. A first Pd thin film mainly composed of Pd and provided on the first insulating film.
A second Pd thin film mainly composed of Pd provided on the second insulating film, and an electrode made of a conductor ohmic-connected to the back surface of the semiconductor substrate. And a detecting unit.

The method of manufacturing a hydrogen gas detecting device according to the present invention is the method of manufacturing a hydrogen gas detecting device for detecting the concentration of hydrogen gas in an oxygen-free environment. Forming a first Pd thin film mainly composed of Pd on the first insulating film after exposing the surface of the first insulating film to ozone; And (iii) exposing the surface of the second insulating film to ozone, and then forming a second Pd thin film containing Pd as a main component on the second insulating film. Forming an electrode made of an ohmic-connected conductor on the back surface of the semiconductor substrate to obtain a second detector.

The method of manufacturing a hydrogen gas detecting device according to the present invention is the method of manufacturing a hydrogen gas detecting device for detecting the concentration of hydrogen gas in an oxygen-free environment. Forming a second insulating film; (ii)
After exposing the surface of the first insulating film to oxygen plasma,
Forming a first Pd thin film containing Pd as a main component on the first insulating film to obtain a first detecting portion; and (iii) exposing the surface of the second insulating film to oxygen plasma. After that, a second Pd thin film containing Pd as a main component is formed on the second insulating film, and an electrode made of an ohmic-connected conductor is formed on the back surface of the semiconductor substrate to form a second Pd thin film. Obtaining a detection unit.

The first detecting section measures the electric resistance of the first Pd thin film containing Pd as a main component. Further, the second detection unit measures a capacitance by applying a voltage between the second Pd thin film containing Pd as a main component and the back electrode. In this case, it is preferable that the thickness of the first insulating film be 300 nm or more. If the thickness of the first insulating film is less than 300 nm, the capacitance between the first Pd thin film and the semiconductor substrate increases, which may affect the operation of the second detection unit. Lower limit is 300n
m. Note that the upper limit of the thickness of the first insulating film is not particularly limited, but is practically 1 μm or so due to manufacturing restrictions.

Further, the thickness of the second insulating film is set to 20 to 150
It is preferably in the range of nm. If the thickness of the second insulating film is less than 20 nm, the insulating property becomes insufficient, and the second P
d When a small current flows when a voltage is applied between the thin film and the back electrode, there is a possibility that stable capacitance measurement may be difficult. Therefore, the lower limit is set to 20 nm. On the other hand, if the thickness of the second insulating film exceeds 150 nm, the capacitance between the second Pd thin film and the semiconductor substrate may be significantly reduced and the detection sensitivity may be reduced. And

Further, it is preferable that the first detecting section has a thin film containing Cr or Ti as a main component and having a thickness of 50 nm or less inserted between the first insulating film and the first Pd thin film. . If the thickness of the Cr or Ti thin film exceeds 50 nm, the detection sensitivity may be reduced.
nm.

The surface of the first insulating film at the lamination interface between the first insulating film and the first Pd thin film is exposed to ozone before lamination, and the second insulating film and the second Pd thin film are exposed to ozone before lamination. P
It is desirable that the surface of the second insulating film at the lamination interface with the d thin film is exposed to ozone before lamination,
At the lamination interface between the first insulating film and the first Pd thin film.
The surface of the insulating film is exposed to oxygen plasma before lamination, and the surface of the second insulating film at the lamination interface between the second insulating film and the second Pd thin film is exposed to oxygen plasma before lamination. It is desirable to have been.

Furthermore, it is desirable to have a heating element on the back surface of the semiconductor substrate. This is because if the temperature of the element is increased by causing the heating element to generate heat during operation, the response speed of the element when exposed to hydrogen is dramatically improved.

Further, a third insulating film provided on the surface of the semiconductor substrate and Pd formed on the third insulating film are formed.
And a third Pd thin film mainly composed of: a third insulating film and a third Pd thin film;
Is preferably formed. The third detection unit measures a current by applying a voltage between the third Pd thin film and the back surface electrode.

Further, it is preferable that the thickness of the third insulating film formed between the third Pd thin film and the semiconductor substrate is in the range of 1 to 3 nm. If the thickness of the third insulating film is less than 1 nm, it becomes difficult to ensure uniformity of the film thickness.
Since the Pd thin film and the semiconductor substrate directly contact each other to cause an electrical short circuit and lower the detection sensitivity, the lower limit was set to 1 nm. On the other hand, if the thickness of the third insulating film exceeds 3 nm,
Since the Pd thin film is electrically insulated from the semiconductor substrate and a current stops flowing even when a voltage is applied, the upper limit is set to 3 nm.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a hydrogen gas detecting device (hydrogen gas detecting element) according to a first embodiment of the present invention.
FIG. On the surface side of the n-type Si substrate 10, the first and second insulating films 20, which are mainly composed of SiO ₂ ,
21 and first and second Pd thin films 3 mainly containing Pd
0, 31 and electrodes 40 a, 40 b, 41 are provided, respectively, and a back surface electrode 43 is provided on the back surface side of the Si substrate 10. When a voltage is applied to both sides of the first Pd thin film 30, the first Pd thin film 30 functions as a first detection unit 50, and the second Pd thin film 31, the second insulating film 21, and the semiconductor substrate 10 apply a voltage. Then, the second detection unit 51
It functions as. That is, the first detection unit 5
At 0, the hydrogen concentration can be known by measuring the electric resistance between the pair of electrodes 40a, 40b.
Then, the hydrogen concentration can be known by measuring the capacitance between the electrodes 41 and 43.

The thickness of the first insulating film 20 is 500 to 100.
The thickness is in the range of 0 nm (0.5 to 1 μm), and the thickness of the second insulating film 21 is in the range of 20 to 150 nm. The second insulating film 21 is formed by selectively removing a part of the Si substrate 10 using a wet etching method or a dry etching method to form an opening, and then oxidizing the opening. It is.

The first Pd thin film 30 is made of a metal film having a thickness of 20 to 100 nm and containing Pd as a main component and alloyed with Cr, Ni or Ag so as to have an atomic ratio of 50% or less. It is formed in a rectangular shape or a meandering shape having many folded portions on one insulating film 20. At substantially both ends of the first Pd thin film 30, a pair of electrodes 40a and 40b having a thickness of 0.5 to 1 μm are formed.

Similarly, the second Pd thin film 31 is made of a metal film having a film thickness of 20 to 100 nm containing Pd as a main component and alloyed with Cr, Ni or Ag so as to have an atomic ratio of 50% or less. The second Pd thin film 31 is composed of the first and second
Are formed over the insulating films 20 and 21 of FIG. That is, one end of the second Pd thin film 31 is formed on the second insulating film 21, and the other end of the second Pd thin film 31 is formed on the first insulating film 20. Furthermore, the second on the other end side
Of the electrode 41 having a thickness of 0.5 to 1 μm on the Pd thin film 31 of FIG.
Are formed.

The surface electrodes 40a, 40b, 41 are made of Al, N
The back electrode 43 is made of a single layer or two or more layers composed mainly of i, Au, Ag, Ti, Cr or the like, and the back electrode 43 is also made of a single layer or two or more layers made of substantially the same material. Of the electrode film.

The electrodes 40a and 40b are used to connect the first Pd thin film 30 on the first insulating film 20 to the first detecting section 50.
To function as an external electric circuit (not shown) via a wire mainly composed of Al, Au or the like. On the other hand, the electrodes 41 and 43 are connected to an external electric circuit (not shown) and Al and Au in order to make the second Pd thin film 31 on the second insulating film 21 function as the second detecting section 51.
It is connected via a wire whose main component is etc.

Next, a method of manufacturing the hydrogen gas detecting device according to the present embodiment will be described with reference to FIGS.

(A) Si substrate 10 used in this embodiment
Is obtained by doping As as an impurity and having a resistivity of 1 × 1
An n-type Si film having a resistivity of 15 Ω · cm and a thickness of 20 μm doped with P (phosphorus) as an impurity is formed on an n-type Si single crystal substrate having a thickness of 0 ^-3 Ω · cm and a thickness of 0.5 mm. An epitaxially grown one was used. First, the substrate 10
The oxide film naturally formed on the surface of the substrate was removed by wet etching, and the substrate surface was cleaned.

(B) Next, chemical vapor deposition (CVD) using monosilane and oxygen diluted with an inert gas as source gases
Method) to form a 1 μm-thick SiO ₂ film as the first insulating film.
The film 20 was formed on the surface of the Si substrate 10. The insulating film forming step includes a chemical vapor deposition method using monosilane and nitrous oxide as a source gas, a chemical vapor deposition method using TEOS and oxygen as a source gas, a chemical vapor deposition method using TEOS and ozone as a source gas,
It can also be formed by a chemical vapor deposition method by thermal decomposition of TEOS or an RF sputtering method.

(C) Next, a photoresist is applied on the SiO ₂ film on the substrate, and the resist coating film is subjected to pattern exposure,
develop. As a result, a predetermined mask pattern 200 having an opening where the second insulating film 21 is to be formed was obtained. The size of the opening of the mask pattern 200 was 0.5 mm × 0.5 mm.

(D) Only the SiO ₂ film exposed at the opening of the mask pattern 200 was selectively removed by wet etching. The wet etching was performed at room temperature for 5 minutes using a mixed aqueous solution of hydrogen fluoride and ammonium fluoride. Note that a plasma dry etching method can be used instead of the wet etching method.

(E) The photoresist used as the mask pattern 200 was removed by washing with a solvent such as acetone. After removal of the resist, the surface was cleaned by irradiating it with ultraviolet rays in the air and exposing it to ozone generated in the irradiated part. Note that oxygen plasma exposure may be performed instead of the ozone exposure.

(F) Then, the Si substrate is heat-treated in pure oxygen gas, and the exposed portion of the Si substrate formed up to the step (e) is oxidized, so that the SiO ₂ film 21 as a _second insulating film is formed. Was formed. In this embodiment, a thickness of 20 mm is obtained by a heat treatment at 800 ° C. × 10 hours in oxygen at atmospheric pressure.
The SiO ₂ insulating film 21 of nm was obtained. In this step, the oxide layer 21b is simultaneously formed on the back surface of the substrate 10.

(G) When removing the unnecessary oxide layer 21b formed on the back surface of the substrate in the step (f), the photoresist 201 is used to protect the front surface of the Si substrate 10.
Is applied to form a protective mask.

(H) The oxide layer 21b on the back side was removed by wet etching.

(I) Next, a back surface electrode 43 is formed so as to cover the back surface of the substrate 10. In this embodiment, 100 nm thick Ti and 200 nm thick A
1, a three-layer film of Ni having a thickness of 500 nm was sequentially laminated to form a back electrode 43. Thus, ohmic contact with the Si substrate 10 can be achieved. Note that the back surface electrode 43 can also be formed using a sputtering method.

(J) The photoresist film 201 on the substrate surface side was removed by acetone washing. After removing the resist, the substrate was irradiated with ultraviolet rays in the air, and the substrate surface was cleaned with ozone generated in the irradiated part. The same effect can be obtained by performing oxygen plasma exposure instead of ozone exposure.

(K) In this embodiment, a 15 nm-thick Cr film and a 50 nm-thick PdCr film containing 10% Cr and 90% Pd at an atomic ratio of 50 nm using a stainless steel foil mask.
A first Pd thin film 30 made of an alloy was sequentially formed by a vacuum evaporation method. The location where the first Pd thin film 30 is formed is the upper surface of the first insulating film 20 having a thickness of 1 μm. The shape of the mask is a meandering shape having a plurality of folded portions each having a width of 1 mm and a length of 200 mm. 15 nm thick C
The r film is inserted to improve the adhesion of the Pd thin film 30, but the same effect can be obtained by inserting a Ti film instead of the Cr film. A mask in which a photoresist is applied, partially exposed using a photomask, and a photosensitive portion is removed by a development process may be used as the mask. According to this method, a finer line width can be obtained. Alternatively, after forming a thin film on the entire surface of the substrate by a vacuum deposition method, a resist pattern is formed by an exposure and development process using a photoresist and a photomask, and unnecessary portions are removed by a wet or dry etching method. Patterns can also be formed. Further, the first Pd thin film 30 can also be formed by a sputtering method. Further, the component of the first Pd thin film 30 is mainly composed of Pd,
An alloy in which Cr, Ni, Ag, or the like is adjusted to an arbitrary composition may be used.

(L) A second Pd thin film 31 made of an alloy of 10% of Cr and 90% of Pd in a 50 nm-thickness atomic ratio is vacuum-deposited by using the same method as in the step (k). It was sequentially formed by the method. The portion where the second Pd thin film 31 is to be formed is formed from the second SiO ₂ insulating film 21 having a thickness of 20 nm to the first SiO ₂ insulating film 20 having a thickness of 1 μm (1000 nm).
Straddled by.

(M) Using the same method as in the steps (k) and (l), the electrodes 40a, 40b, and 41 each having a two-layer structure of a 15-nm-thick Cr film and a 500-nm-thick Ni film are formed. Laminated and formed. That is, the pair of electrodes 40a, 4
Ob was formed on both ends of the meandering first Pd thin film 30. The pair of electrodes 40a and 40b and the back electrode 4
3 was connected to an external circuit (not shown) by a lead wire to form a first detection unit 50. The single electrode 41 was formed on the second Pd thin film 31. The second detection unit 51 was formed by connecting the front-side electrode 41 and the back-side electrode 43 to an external circuit (not shown) with a lead wire. The hydrogen gas detector 161 provided with the first and second detectors 50 and 51 thus manufactured can detect hydrogen with high sensitivity even in an oxygen-free environment.

Next, the operating characteristics of the first detector 50 will be described with reference to FIG.

FIG. 3 shows the hydrogen concentration (% by volume) on the horizontal axis.
FIG. 7 is a characteristic diagram showing the result of examining the correlation between the resistance value change (relative value) on the vertical axis. The change in the electric resistance of the first detection unit 50 (the electrodes 40a,
0b). Assuming that the resistance value in pure nitrogen gas is 1 (reference value), the resistance values for various hydrogen gas concentrations are indicated as relative values. In the figure, the characteristic line A shows the measurement result. As is clear from this, the resistance value of the first detection unit 50 increases due to the hydrogen exposure, and even under an anoxic environment, the characteristic line A is more than 5%. It has been found that the concentration of hydrogen can be detected, and that the resistance value of the first detection unit 50 increases and decreases almost directly in the low concentration region up to 5% of the hydrogen concentration. In addition, the first detection unit 50
The element did not break down even when exposed to hydrogen gas having a concentration of 100%, confirming that the hydrogen gas sensor had stable performance in an oxygen-free environment. Furthermore, it was confirmed that the same hydrogen detection performance was obtained for hydrogen in vacuum.

In the apparatus according to the present embodiment, the first detector 5
When 0 is exposed to hydrogen, the hydrogen diffuses into the thin film 30 containing Pd as a main component, enters the crystal lattice, and makes it difficult for electrons to flow, which is measured as an increase in resistivity. .

Next, the operating characteristics of the second detector 51 will be described with reference to FIG.

FIG. 4 shows the hydrogen concentration (ppm) on the horizontal axis.
FIG. 7 is a characteristic diagram showing the result of examining the correlation between the capacitances (relative values) on the vertical axis. The change in the capacitance of the second detection unit 51 (the capacitance between the electrodes 41 and 43) was measured in an oxygen-free environment in which a small amount of hydrogen gas was added to and mixed with nitrogen gas at atmospheric pressure. Specifically, the hydrogen concentration is set to 0 to 1
A constant voltage of 0.5 V was applied between the electrodes 41 and 43 with various changes in the range of 000 ppm, and the capacitance at that time was measured.

In the figure, a characteristic line B shows the measurement result. As is apparent from the drawing, the capacitance of the second detection unit 51 is rapidly increased by being exposed to a low concentration of hydrogen of 150 ppm or less. As a result, the sensitivity was found to be very high in the low concentration region. In addition, the second detection unit 51 did not break down even when exposed to hydrogen gas having a concentration of 100%, and it was confirmed that the second detection unit 51 had stable performance as a hydrogen gas sensor under an oxygen-free environment. Furthermore, it was confirmed that the same hydrogen detection performance was obtained for hydrogen in vacuum.

In the apparatus according to the present embodiment, the second detector 5
When 1 is exposed to hydrogen, the hydrogen diffuses into the thin film 31 containing Pd as a main component, and an electric dipole is formed at the interface with the second insulating film 21. This causes an increase in capacitance. It is what is measured.

According to the apparatus of the above embodiment, since the first and second detection units having two different functions are provided,
Hydrogen can be detected with high sensitivity and reliability even in an oxygen-free environment such as an inert gas atmosphere containing no oxygen or in a vacuum such as space. Further, the apparatus according to the present embodiment can measure not only hydrogen in a low concentration region but also hydrogen in a high concentration region.

(Second Embodiment) FIG. 5 shows a hydrogen gas detecting device (hydrogen gas detecting element) according to a second embodiment of the present invention.
FIG. Note that the present embodiment corresponds to the first
The description of the parts common to the first embodiment will be omitted.

In the hydrogen gas detection device 161A of this embodiment, a 1 μm (1000 nm) thick S
An iO ₂ insulating film 60 was provided, and a heating element 61 made of a conductive thin film such as a Ni—Cr alloy was formed on the SiO ₂ insulating film 60. The heating element 61 is connected to a power supply circuit (not shown) via a lead wire, and is configured to generate resistance heat by power supply.

The device 161A of the present embodiment has a heating element 61
In this case, the temperature of the element is raised by Joule heat generated by supplying power to the element, and the response speed in the case of hydrogen exposure is improved. In such an apparatus, the temperature of the element is set to 60 to 100
A temperature measuring element (not shown) is provided to keep the temperature constant at an arbitrary temperature within the range of ° C., and a controller (not shown) for controlling the amount of current supplied to the heating element 61 is provided.

According to the apparatus of the present embodiment, the diffusion rate of hydrogen in the thin film containing Pd as a main component is increased, and the time required for hydrogen leak detection can be greatly shortened. The required time was about 0.1 second, and it was confirmed that the device had high response performance.

(Third Embodiment) FIG. 6 shows a hydrogen gas detecting device (hydrogen gas detecting element) according to a third embodiment of the present invention.
FIG. Note that the present embodiment corresponds to the first
The description of the same parts as those of the second embodiment will be omitted.

In the hydrogen gas detector 161B of the present embodiment, a third detector 52 is further provided. The third detection unit 52 has substantially the same structure as the second detection unit 51, except that the third detection unit 52 is formed on the Si substrate 10.
The thickness of the third insulating film 22 containing iO ₂ as a main component is different from that of the second insulating film 21. That is, the thickness of the third insulating film 22 is set to 1.5 to 3.0 nm, which is smaller than the thickness of the second insulating film 21.

A method for forming the third insulating film 22 will be described. After exposing the surface of the Si substrate 10 by etching, the third insulating film 22 is immersed for a predetermined time in a mixed solution of sulfuric acid and hydrogen peroxide solution, and pulled up from the solution.
Wash using ultrapure water. Thereafter, an insulating film having a thickness of 2 nm was formed by exposure to ozone generated by irradiation with ultraviolet light in the air. Note that a similar insulating film 22 can be obtained by using oxygen plasma exposure instead of ozone exposure.

Next, the operation of detecting hydrogen in the third detector 52 will be described with reference to FIG. FIG. 7 shows the hydrogen concentration (ppm) on the horizontal axis and the current (relative value) on the vertical axis.
FIG. 9 is a characteristic diagram showing a result of examining a correlation between the two.
In an oxygen-free environment where only a small amount of hydrogen gas is added to and mixed with nitrogen gas at atmospheric pressure, minus 0.5 V is applied to the electrode 43.
Is applied to the electrode 42, the current flowing between the electrodes 42 and 43 was measured under various hydrogen concentration environments. In the figure, a characteristic line C shows a measurement result.
As is clear from this, even under an oxygen-free environment, the current value increased due to hydrogen exposure, and it was found that low-concentration hydrogen of 1300 ppm or less can be detected with high sensitivity. Also,
The element did not break down even when exposed to hydrogen having a concentration of 100%, and it was confirmed that the element had the same hydrogen detection performance with respect to hydrogen leaked in vacuum.

When the third detecting section 52 of this embodiment is exposed to hydrogen, the third Pd thin film 3 mainly composed of Pd is formed of hydrogen.
2, which lowers the potential barrier at the interface with the insulating film 22, which is measured as an increase in the current flowing between the electrodes 42 and 43.

According to the present embodiment, since the three types of detectors 50, 51, and 52 having different functions are combined, an oxygen-free atmosphere such as an inert gas atmosphere in which oxygen does not exist at all or a vacuum such as in space. Hydrogen can be detected with high sensitivity and certainty even under the above environment.

(Fourth Embodiment) FIG. 8 shows a hydrogen gas detecting device (hydrogen gas detecting element) according to a fourth embodiment of the present invention.
FIG. Note that the present embodiment corresponds to the first
Descriptions of parts common to the third embodiment are omitted. In this embodiment, an example will be described in which a plurality of hydrogen gas detection devices are attached to various portions of a liquefied hydrogen storage container and used for detecting hydrogen leakage.

The liquefied hydrogen storage container 111 is a vacuum insulated container 1
22 surrounds the periphery. Six hydrogen gas detectors 161a to 161a are provided on the outer wall of the vacuum heat insulating container 122.
61f are respectively mounted in place. These hydrogen gas detectors 161a to 161f can be connected to the respective wires 171a to 171f without breaking the vacuum of the vacuum heat insulating container 122.
Are respectively connected to the input side of the controller 180 via the. The output side of the controller 180 is connected to each power supply circuit of a display device and an alarm device (not shown).

When the detection signal is input from each of the hydrogen gas detectors 161a to 161f, the CPU of the controller 180 calls up predetermined mathematical expression data from the memory, and stores actual measurement value information obtained from the detection signal and predetermined mathematical expression. Is calculated based on the above equation to determine the hydrogen concentration. Then, the obtained hydrogen concentration and the measurement position are displayed on the screen of the display device, and when at least one hydrogen concentration value exceeds a predetermined threshold value, an alarm signal is sent to an alarm device to sound an alarm, and an operator is notified of the hydrogen concentration. Notify that a leak has occurred.

In this embodiment, it is possible to quickly and reliably detect, in a liquefied hydrogen storage container, which is a large-scale facility, a location where hydrogen gas has leaked with high sensitivity and in a high concentration range. The safety and reliability of the liquefied hydrogen storage container of the type can be remarkably improved.

[0066]

According to the present invention, the leakage of hydrogen can be detected with high sensitivity, quickly and reliably even in an oxygen-free environment without any oxygen. The device of the present invention is not limited to equipment on the earth, but can also be applied to equipment on space, the moon, or other planets, and has a wide range of applications. .

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a hydrogen gas detection device according to a first embodiment of the present invention.

FIGS. 2A to 2M are flowcharts illustrating a method for manufacturing a hydrogen gas detection device according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a correlation between a change in resistance value and a hydrogen concentration.

FIG. 4 is a characteristic diagram showing a correlation between capacitance (relative value) and hydrogen concentration (% by volume).

FIG. 5 is an enlarged sectional view showing a hydrogen gas detection device according to a second embodiment of the present invention.

FIG. 6 is an enlarged sectional view showing a hydrogen gas detection device according to a third embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a correlation between a current (relative value) and a hydrogen concentration.

FIG. 8 is a configuration block diagram schematically showing a liquefied hydrogen storage container provided with a hydrogen gas detection device according to a fourth embodiment of the present invention for detecting leaked gas.

FIG. 9 is a configuration block diagram schematically showing a conventional leak detection method in a compressed hydrogen storage container installed in an explosion-proof atmosphere.

FIG. 10 is a configuration block diagram schematically showing another conventional leak detection method for a liquefied hydrogen storage container installed in an explosion-proof atmosphere.

FIG. 11 is a schematic diagram showing a liquefied hydrogen storage container installed in a vacuum insulated container.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate, 20 ... 1st insulating film, 21 ... 2nd insulating film, 22 ... 3rd insulating film, 30 ... 1st Pd thin film, 31 ... 2nd Pd thin film, 32 ... 3rd Pd thin film, 40a, 40b, 41, 42 ... electrode (electrode film), 43 ... back electrode, 50 ... first detection unit, 51 ... second detection unit, 52 ... third detection unit, 111 ... liquefied hydrogen Storage container, 122: Vacuum insulated container, 161, 161A, 161B, 161a to 161f: Hydrogen gas detection device, 171a to 171f: Wiring, 180: Control device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Nomaru 10 Oecho, Minato-ku, Nagoya-shi, Aichi Prefecture Mitsubishi Heavy Industries, Ltd. No. 10 town Mitsubishi Heavy Industries, Ltd. Nagoya Aerospace Systems Works F-term (reference) 2G046 AA01 AA05 BA01 BA09 BB02 BB04 EA02 EA09 FB00 FE29 FE38 2G060 AA01 AB03 AE19 AF10 BA09 JA01

Claims (19)

[Claims] 1. A hydrogen gas detection device for detecting a concentration of hydrogen gas in an oxygen-free environment, comprising: a first and a second insulating film provided on a surface of a semiconductor substrate; and a first insulating film provided on the first insulating film. A first detector having a first Pd thin film mainly composed of Pd, a second Pd thin film mainly composed of Pd provided on the second insulating film, A second detection portion having an electrode made of a conductor that is ohmic-connected to the back surface thereof. 2. The apparatus according to claim 1, wherein the first detector measures an electric resistance of the first Pd thin film containing Pd as a main component. 3. The device according to claim 2, wherein the second detector measures a capacitance by applying a voltage between the second Pd thin film containing Pd as a main component and the back electrode. An apparatus according to claim 1. 4. The device according to claim 1, wherein the thickness of the first insulating film is 300 nm or more. 5. The semiconductor device according to claim 1, wherein said second insulating film has a thickness of 20 to 150.
2. The device according to claim 1, wherein the range is nm. 6. The device according to claim 1, wherein the semiconductor substrate is mainly composed of silicon. 7. The device according to claim 1, wherein the first and second insulating films are each mainly composed of silicon oxide. 8. The first detecting section further includes a thin film containing Cr or Ti as a main component and having a thickness of 50 nm or less inserted between the first insulating film and the first Pd thin film. The device of claim 1 comprising: 9. The lamination interface between the first insulation film and the first Pd thin film, wherein the surface of the first insulation film is exposed to ozone before lamination, and the second insulation film 2. The apparatus according to claim 1, wherein the surface of the second insulating film is exposed to ozone before lamination at a lamination interface between the second Pd thin film and the second Pd thin film. 10. The first insulating film surface at a lamination interface between the first insulating film and the first Pd thin film is exposed to oxygen plasma before lamination, and the second insulating film is 2. The apparatus according to claim 1, wherein the surface of the second insulating film at a lamination interface between the film and the second Pd thin film is exposed to oxygen plasma before lamination. 11. The apparatus according to claim 1, further comprising a heating element on a back surface of said semiconductor substrate. 12. A semiconductor device comprising: a third insulating film provided on a surface of the semiconductor substrate; and a third Pd thin film containing Pd as a main component and formed on the third insulating film. 2. The device according to claim 1, wherein a third detecting portion is formed by the third insulating film, the third Pd thin film, and the back electrode. 13. The third Pd,
13. The apparatus according to claim 12, wherein a voltage is applied between the thin film and the back electrode to measure a current. 14. The device according to claim 12, wherein the thickness of the third insulating film formed between the third Pd thin film and the semiconductor substrate is in a range of 1 to 3 nm. 15. The device according to claim 12, wherein the third insulating film contains silicon oxide as a main component. 16. A method of manufacturing a hydrogen gas detecting device for detecting a concentration of hydrogen gas in an oxygen-free environment, comprising: (i) forming first and second insulating films on a surface of a semiconductor substrate; After exposing the surface of the first insulating film to ozone,
Forming a first Pd thin film containing Pd as a main component on the first insulating film to obtain a first detecting portion; and (iii) exposing the surface of the second insulating film to ozone. Later, a second P containing Pd as a main component is formed on the second insulating film.
d. forming a thin film, and further forming an electrode made of an ohmic-connected conductor on the back surface of the semiconductor substrate to obtain a second detecting portion, thereby manufacturing a hydrogen gas detecting device. Method. 17. A method for manufacturing a hydrogen gas detection device for detecting a concentration of hydrogen gas in an oxygen-free environment, comprising: (i) forming first and second insulating films on a semiconductor substrate; Exposing the surface of the first insulating film to oxygen plasma, and then forming a first Pd thin film containing Pd as a main component on the first insulating film to obtain a first detecting portion; (Iii) after exposing the surface of the second insulating film to oxygen plasma, the second insulating film containing Pd as a main component is formed on the second insulating film.
Forming a Pd thin film, and further forming an electrode made of an ohmic-connected conductor on the back surface of the semiconductor substrate,
A method for producing a hydrogen gas detection device, comprising the steps of: 18. The method according to claim 16, further comprising exposing the silicon surface to ozone to form a third insulating film.
Or the production method according to any one of 17. 19. The method according to claim 16, further comprising exposing the silicon surface to oxygen plasma to form a third insulating film.