Hydrogen detection device and method for manufacturing same

Abstract

A hydrogen detection device (10) is provided with a hydrogen sensor (100) as a first resistive element, a resistor (R1) as a second resistive element, a reference element (100a) as a third resistive element, and a resistor (R2) as a fourth resistive element, which constitute a bridge circuit. At least the hydrogen sensor (100) and the reference element (100a) are formed in a single semiconductor chip (12). A hydrogen sensor (100) has a first electrode (103), a second electrode (106), a metal oxide layer (104), an insulating film (107b), and the like. The insulating film (107b) has an opening (106a) that exposes the second electrode (106). The reference element (100a) has a first electrode (103), a second electrode (106), a metal oxide layer (104), an insulating film (107b), and the like. The insulating film (107b) does not have an opening that exposes the second electrode (106).

Description

Technical Field

[0001] The present invention relates to a hydrogen detection device and a manufacturing method thereof, and in particular to a hydrogen detection device composed of a bridge circuit and a manufacturing method thereof. Background Art

[0002] Conventionally, a hydrogen detection device composed of a bridge circuit using four resistor elements has been proposed (for example, see Patent Document 1). The bridge circuit is a Wheatstone bridge circuit.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-152451 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, the hydrogen detection device of Patent Document 1 requires a heater and a temperature control unit, and further performance improvement is required.

[0008] Therefore, an object of the present invention is to provide a hydrogen detection device which is composed of a bridge circuit, does not necessarily require a heater, and can operate stably, and a method for manufacturing the same.

[0009] Means for solving problems

[0010] In order to achieve the above-mentioned purpose, a hydrogen detection device involved in one embodiment of the present invention comprises: a first resistor element, a second resistor element, a third resistor element and a fourth resistor element constituting a bridge circuit, one end of the first resistor element is connected to one end of the second resistor element, one end of the third resistor element is connected to one end of the fourth resistor element, the other end of the first resistor element is connected to the other end of the third resistor element, and the other end of the second resistor element is connected to the other end of the fourth resistor element, at least the first resistor element and the third resistor element among the first resistor element, the second resistor element, the third resistor element and the fourth resistor element are formed on a semiconductor chip, the first resistor element is a hydrogen sensor, and has: a first electrode and a second electrode, whose main surfaces are arranged opposite to each other; a first A metal oxide layer is configured to be in contact with the main surface of the first electrode and the main surface of the second electrode; and a first insulating film covers the first electrode, the second electrode and the first metal oxide layer, the first insulating film has a first opening that exposes the other surface of the second electrode opposite to the main surface without being covered by the first insulating film, and the third resistor element is a reference element, comprising: a third electrode and a fourth electrode, whose main surfaces are arranged opposite to each other; a second metal oxide layer is configured to be in contact with the main surface of the third electrode and the main surface of the fourth electrode; and a second insulating film covers the third electrode, the fourth electrode and the second metal oxide layer, the second insulating film does not have an opening that exposes the other surface of the fourth electrode opposite to the main surface without being covered by the second insulating film.

[0011] In order to achieve the above-mentioned purpose, a manufacturing method of a hydrogen detection device in one embodiment of the present invention is a manufacturing method of a hydrogen detection device having a first resistor element as a hydrogen sensor, a second resistor element, a third resistor element as a reference element, and a fourth resistor element constituting a bridge circuit, comprising: a stack forming step of forming a stack for the first resistor element and the third resistor element; and an opening forming step of forming an opening in the formed stack, in which a stack is formed as the first resistor element and the third resistor element, and a stack is formed consisting of: a first electrode and a second electrode, whose main surfaces are arranged opposite to each other; a metal oxide layer, which is arranged in contact with the main surface of the first electrode and the main surface of the second electrode; and an insulating film, which covers the first electrode, the second electrode and the metal oxide layer, in which, at least for the stack of the first resistor element, a first opening is formed in the insulating film so that the other surface of the second electrode opposite to the main surface is not covered by the insulating film and is exposed.

[0012] Effects of the Invention

[0013] According to the present invention, there are provided a hydrogen detecting device which is composed of a bridge circuit, does not necessarily require a heater, and can operate stably, and a method for manufacturing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : is an equivalent circuit diagram of the hydrogen detection device according to the embodiment.

[0015] Figure 2A Yes means Figure 1 A cross-sectional view of a structural example of a hydrogen sensor shown.

[0016] Figure 2B Yes means Figure 2A A top view of a structural example of a hydrogen sensor shown.

[0017] Figure 3 Yes means Figure 1 A cross-sectional view of a structural example of a reference element is shown.

[0018] Figure 4A It is a schematic diagram showing an overall configuration example of a hydrogen detection device according to an embodiment.

[0019] Figure 4B Yes means Figure 4A FIG. 1 is a plan view showing an example of a layout of wiring patterns of hydrogen sensors and reference elements in the hydrogen detection device shown.

[0020] Figure 5 1 is a flowchart showing a method for manufacturing a hydrogen detection device according to an embodiment.

[0021] Figure 6 Graphs showing experimental results of the time dependency and distance dependency of the output voltage (difference voltage) of the hydrogen detection device according to the embodiment.

[0022] Figure 7 It is a diagram showing the experimental results regarding the reaction of the hydrogen detection device according to the embodiment to hydrogen.

[0023] Figure 8 It is a schematic diagram showing an overall configuration example of a hydrogen detection device according to Modification 1 of the embodiment.

[0024] Fig. 9A It is a schematic diagram showing an overall configuration example of a hydrogen detection device according to a second modification of the embodiment.

[0025] Fig. 9B Yes means Fig. 9A FIG. 1 is a plan view showing an example of a layout of wiring patterns of hydrogen sensors and reference elements in the hydrogen detection device shown.

[0026] Fig.10This is a flowchart showing a method for manufacturing a hydrogen detection device according to Modification 2 of the embodiment.

[0027] Fig.11 It is a schematic diagram showing an overall configuration example of a hydrogen detection device according to a third modification of the embodiment. DETAILED DESCRIPTION

[0028] Hereinafter, the embodiments of the present invention will be described in detail using the accompanying drawings. In addition, the embodiments described below all represent a specific example of the present invention. The numerical values, shapes, materials, constituent elements, configuration positions of constituent elements, connection methods, steps, order of steps, etc. shown in the following embodiments are examples and do not limit the subject matter of the present invention. In addition, the figures are not necessarily strictly illustrated. In each figure, the same figure mark is marked for substantially the same structure, and repeated descriptions are omitted or simplified. In addition, "A and B are connected" means that A and B are electrically connected, which includes not only the case where A and B are directly connected, but also the case where A and B are indirectly connected in a state where other circuit elements are inserted between A and B.

[0029] Figure 1 2 is an equivalent circuit diagram of the hydrogen detection device 10 according to the embodiment. In this figure, a voltmeter 20 and a DC voltage source 21 are also shown as external devices.

[0030] The hydrogen detection device 10 includes a hydrogen sensor 100 as a first resistance element, a resistor R1 as a second resistance element, a reference element 100a as a third resistance element, and a resistor R2 as a fourth resistance element, which constitute a bridge circuit. One end of each of the hydrogen sensor 100 and the resistor R1 is connected to a terminal B, and one end of each of the reference element 100a and the resistor R2 is connected to a terminal D. The other ends of each of the hydrogen sensor 100 and the reference element 100a are connected to a terminal A, and the other ends of each of the resistor R1 and the resistor R2 are connected to a terminal D. The hydrogen sensor 100, the resistor R1, the reference element 100a, and the resistor R2 are formed on a single semiconductor chip 12.

[0031] In an environment without hydrogen, the hydrogen sensor 100 and the reference element 100a have the same resistance value. In an environment with hydrogen, only the resistance value of the hydrogen sensor 100 decreases according to the concentration of hydrogen. The resistor R1 and the resistor R2 have the same resistance value and are fixed resistance values ​​of, for example, 20Ω, made of polysilicon or the like.

[0032] Between the terminal A and the terminal C of such a hydrogen detection device 10, a DC voltage is applied from the DC voltage source 21, and the voltage of the terminal B is measured with respect to the terminal D by the voltmeter 20. Since the resistance value of the hydrogen sensor 100 decreases according to the hydrogen concentration, the resistance balance of the bridge circuit is destroyed, and a potential difference is generated between the terminal B and the terminal D, and this potential difference is measured by the voltmeter 20.

[0033] Figure 2A Yes means Figure 1 2 is a cross-sectional view of a structural example of a hydrogen sensor 100 shown in FIG. Figure 2B Yes means Figure 2A FIG. 1 is a top view of a structural example of a hydrogen sensor 100 shown in FIG. Figure 2A Indicates observation along the arrow direction based on Figure 2B A schematic cross section of a cross section taken along line IA-IA in FIG.

[0034] As main components, the hydrogen sensor 100 includes a first electrode 103 and a second electrode 106 arranged with their main surfaces facing each other, a metal oxide layer 104 as a first metal oxide layer arranged in contact with the main surface (i.e., upper surface) of the first electrode 103 and the main surface (i.e., lower surface) of the second electrode 106, and a first insulating film (insulating films 107a to 107c, 109a and 109b) covering the first electrode 103, the second electrode 106 and the metal oxide layer 104. The first insulating film has an opening 106a that exposes the other surface (i.e., upper surface) of the second electrode 106 that is not covered by the first insulating film. In this embodiment, the metal layer 106s is also removed from the opening 106a in order to expose the second electrode 106.

[0035] The hydrogen sensor 100 has three terminals (a first terminal TE1, a second terminal TE2, and a third terminal BE) for external connection. The first terminal TE1 and the second terminal TE2 are connected to the other surface of the second electrode 106 via the through hole 108. The third terminal BE is connected to the other surface (i.e., the lower surface) of the first electrode 103 opposite to the main surface (i.e., the upper surface) via the wiring 114 and the through hole 108. Figure 2A When the hydrogen sensor 100 is used in a horizontal mode in which a current flows horizontally to detect low-concentration hydrogen, the first terminal TE1 and the second terminal TE2 are connected to other resistor elements as one end and the other end of the hydrogen sensor 100. Figure 2A When used in a vertical mode for detecting high-concentration hydrogen by passing a current in the vertical direction, one of the first terminal TE1 and the second terminal TE2 and the third terminal BE are connected to other resistor elements as one end and the other end of the hydrogen sensor 100 .

[0036] The hydrogen sensor 100 shown in this figure is a dual-purpose type that can be used in either the horizontal mode or the vertical mode. However, the hydrogen sensor constituting the hydrogen detection device 10 is not limited to such a dual-purpose type, and may be, for example, a type dedicated to the horizontal mode without forming the third terminal BE.

[0037] The details of the structure and materials of each component are as follows.

[0038] The first electrode 103 is a planar electrode having two surfaces. One of the two surfaces of the first electrode 103 (i.e. Figure 2A The upper surface of the metal oxide layer 104 is in contact with the other surface (i.e. Figure 2A The lower surface of the insulating film 107a and the through hole 108 are connected. Figure 2B In the embodiment, the first electrode 103 is a rectangular shape having the same size as the second electrode 106. The first electrode 103 may be made of a material having a lower standard electrode potential than the metal constituting the metal oxide, such as tungsten, nickel, tantalum, titanium, aluminum, tantalum nitride, or titanium nitride. The standard electrode potential indicates a characteristic that the higher the value, the more difficult it is to oxidize. Figure 2A The first electrode 103 is formed of, for example, a transition metal nitride such as tantalum nitride (TaN) or titanium nitride (TiN), or a stack of these.

[0039] The metal oxide layer 104 is sandwiched between the first electrode 103 and the second electrode 106, and is composed of a metal oxide as a gas-responsive resistive film, and has a resistance value that changes reversibly according to the presence or absence of a hydrogen-containing gas in the gas that the second electrode 106 contacts. The metal oxide layer 104 only needs to have a property that the resistance changes due to hydrogen. For example, the metal oxide layer 104 is composed of an oxygen-deficient metal oxide. The parent metal of the metal oxide layer 104 can be selected from at least one of transition metals such as tantalum (Ta), hafnium (Hf), titanium (Ti), zirconium (Zr), niobium (Nb), tungsten (W), nickel (Ni), iron (Fe), and aluminum (Al).

[0040] Transition metals can take multiple oxidation states and therefore can achieve different resistance states through redox reactions. Here, the "oxygen vacancy degree" of a metal oxide refers to the ratio of the amount of oxygen vacancies in the metal oxide to the amount of oxygen in an oxide of a stoichiometric composition consisting of the same element as the metal oxide. Here, the amount of oxygen vacancies refers to the value obtained by subtracting the amount of oxygen in the metal oxide from the amount of oxygen in the metal oxide of a stoichiometric composition. If there are multiple metal oxides of a stoichiometric composition consisting of the same element as the metal oxide, the oxygen vacancy degree of the metal oxide is defined based on the one of the metal oxides of these stoichiometric compositions having the highest resistance value. Metal oxides of stoichiometric composition have more stable and higher resistance values ​​than metal oxides of other compositions.

[0041] For example, when the parent metal of the metal oxide layer 104 is tantalum (Ta), the oxide based on the stoichiometric composition defined above is Ta. 2 O 5 , so it can be expressed as TaO 2.5 .TaO 2.5 The oxygen vacancy degree of TaO is 0%, 1.5 The oxygen vacancy degree is (2.5-1.5) / 2.5=40%. In addition, the oxygen vacancy degree of metal oxides with excess oxygen is a negative value. It should be noted that in the present invention, unless otherwise specified, the oxygen vacancy degree can take a positive value, 0 or a negative value. Oxides with a small oxygen vacancy degree are closer to oxides of stoichiometric composition, so the resistance value is high, and oxides with a large oxygen vacancy degree are closer to the metal constituting the oxide, so the resistance value is low.

[0042] Figure 2A The metal oxide layer 104 shown has a first layer 104a connected to the first electrode 103, a second layer 104b connected to the first layer 104a and the second electrode 106, and an insulating separation layer 104i. The oxygen vacancy degree of the second layer 104b is less than that of the first layer 104a. For example, the first layer 104a is TaO X The second layer 104b is Ta with a smaller oxygen vacancy content than the first layer 104a. 2 O 5 In addition, the metal oxide layer 104 has an insulating separation layer 104 i on the outer periphery of the first electrode 103 in a plan view.

[0043] Here, the plan view refers to the Figure 2A In other words, the hydrogen sensor 100 of the present invention is observed from a viewpoint in the stacking direction, that is, from a viewpoint in the normal direction of any one of the planar first electrode 103 and the planar second electrode 106. For example, Figure 2B The upper surface of the hydrogen sensor 100 is shown.

[0044] The resistance state of such a metal oxide layer 104 decreases according to the hydrogen-containing gas (the larger the amount) in contact with the second electrode 106. In detail, when there is a hydrogen-containing gas in the gas to be detected, hydrogen atoms dissociate from the hydrogen-containing gas in the second electrode 106. The dissociated hydrogen atoms invade the metal oxide layer 104 and form impurity energy levels. In particular, they are concentrated near the interface with the second electrode 106, and the thickness of the second layer 104b is apparently thinned. As a result, the resistance value of the metal oxide layer 104 is reduced.

[0045] The second electrode 106 is a planar electrode having hydrogen dissociation properties and has two surfaces. One of the two surfaces of the second electrode 106 (i.e. Figure 2A The lower surface of the metal oxide layer 104 is in contact with the metal oxide layer 104, and the other surface (i.e. Figure 2A The second electrode 106 has an exposed portion 106e exposed to the outside air in the opening 106a. The second electrode 106 is made of a material having a catalytic effect of dissociating hydrogen atoms from gas molecules having hydrogen atoms, such as a noble metal such as platinum (Pt), iridium (Ir), palladium (Pd), or nickel (Ni), or an alloy containing at least one of them. Figure 2A The second electrode 106 is made of platinum (Pt). The second electrode 106 is connected to two terminals, namely, a first terminal TE1 and a second terminal TE2.

[0046] The first terminal TE1 is connected to the second electrode 106 via the through hole 108 .

[0047] The second terminal TE2 is connected to the second electrode 106 via the through hole 108. When the hydrogen sensor 100 is used in the horizontal mode, the first terminal TE1 and the second terminal TE2 are connected to an external detection circuit (here, the resistor R1 and the reference element 100a) driving the hydrogen sensor 100 via the openings TE1a and TE2a.

[0048] like Figure 2B As shown, the first terminal TE1 and the second terminal TE2 are arranged at a position sandwiching the exposed portion 106e in a plan view of the second electrode 106. With this arrangement, by applying a predetermined voltage between the first terminal TE1 and the second terminal TE2, the exposed portion 106e of the second electrode 106 is energized, that is, a current flows through the exposed portion 106e. It is considered that the energization of the exposed portion 106e of the second electrode 106 activates the hydrogen dissociation action of the exposed portion 106e. The predetermined voltage may be a voltage with opposite polarity.

[0049] In the hydrogen sensor 100, when the exposed portion 106e is energized, gas molecules containing hydrogen atoms come into contact with the exposed portion 106e, thereby changing the resistance value between the first terminal TE1 and the second terminal TE2. The above-mentioned detection circuit detects the change in resistance value (this detection is also called "horizontal mode"), and detects gas molecules containing low-concentration hydrogen atoms.

[0050] The third terminal BE is connected to the first electrode 103 via the opening BEa, the through hole 108, the wiring 114, and the through hole 108. The third terminal BE is connected to an external detection circuit that drives the hydrogen sensor 100 via the opening BEa. In the hydrogen sensor 100, the gas molecules containing hydrogen atoms contact the exposed portion 106e when the exposed portion 106e is energized, thereby changing the resistance between the first electrode 103 and the second electrode 106. In other words, the hydrogen sensor 100 changes the resistance value between at least one of the first terminal TE1 and the second terminal TE2 and the third terminal BE when the gas molecules containing hydrogen atoms contact the exposed portion 106e when the exposed portion 106e is energized. The change in resistance value is detected by the above-mentioned detection circuit (this detection is also referred to as "vertical mode"), and gas molecules containing high-concentration hydrogen atoms are detected.

[0051] Furthermore, the insulating film 102 , the insulating films 107 a to 107 c , and the insulating films 109 a and 109 b covering the main portion of the hydrogen sensor 100 are formed of a silicon oxide film, a silicon nitride film, or the like.

[0052] In addition, a metal layer 106s is formed on the upper surface of the second electrode 106 except for the opening 106a. The metal layer 106s is made of, for example, TiAlN and is formed as an etching stopper for forming a through hole, but is not essential.

[0053] In addition, the stack of the first electrode 103, the metal oxide layer 104, and the second electrode 106 is an element that can be used as a storage element of a resistance change memory (Re RAM). In the resistance change memory, two states of the high resistance state and the low resistance state that the metal oxide layer 104 can take are used as a digital storage element. In the hydrogen sensor 100 of the present invention, the high resistance state of the states that the metal oxide layer 104 can take is used. However, the hydrogen detection device 10 of the present invention is not limited to the use of the high resistance state, and may also be a method of using the resistance state.

[0054] It should be noted that in Figure 2A In the figure, the metal oxide layer 104 is shown to be composed of TaO X The first layer 104a of the material and the Ta with a small oxygen vacancy 2 O 5The example of a two-layer structure composed of the second layer 104b of the material, but it can also be Ta with a small oxygen vacancy degree. 2 O 5 or TaO X A layer structure of a material.

[0055] Figure 3 Yes means Figure 1 A cross-sectional view of a structural example of a reference element 100a is shown.

[0056] Refer to this figure and Figure 2A It can be seen that the reference element 100a is equivalent to Figure 2A The hydrogen sensor 100 shown in FIG. 1 is an element in which the opening 106a is not formed (that is, the opening 106a is blocked). That is, as a main component, the reference element 100a has a third electrode ( Figure 3 The first electrode 103) and the fourth electrode ( Figure 3 The second electrode 106), and the third electrode ( Figure 3 The first electrode 103) and the fourth electrode ( Figure 3 The second metal oxide layer ( Figure 3 The metal oxide layer 104), and the third electrode ( Figure 3 The first electrode 103), the fourth electrode ( Figure 3 The second electrode 106) and the second metal oxide layer ( Figure 3 The second insulating film (metal oxide layer 104) Figure 3 The second insulating film does not have the fourth electrode ( Figure 3 An opening in which the other surface of the second electrode 106) opposite to the main surface is not covered by the second insulating film and is exposed.

[0057] Figure 4A 1 is a schematic diagram showing an example of the overall structure of the hydrogen detection device 10 according to the embodiment. Here, the hydrogen sensor 100 and the reference element 100a are of a type dedicated to the horizontal mode (i.e., a type without a third terminal BE), and their cross-sectional structures are shown, while the resistors R1 and R2 are functionally shown.

[0058] As shown in this figure, the hydrogen detection device 10 is characterized in that the four resistance elements (hydrogen sensor 100, reference element 100a, resistors R1 and R2) constituting the bridge circuit are formed on a semiconductor chip 12. More specifically, the distance between the hydrogen sensor 100 and the reference element 100a, which have basically the same structure, is less than 2000μm in a plan view.

[0059] Figure 4B Yes means Figure 4A 1 is a plan view of a layout example of the wiring patterns of the hydrogen sensor 100 and the reference element 100a in the hydrogen detection device 10. In this plan view, there are shown a wiring pattern A1 that connects the second terminal TE2 of the hydrogen sensor 100 formed with the opening 106a and the second terminal TE2 of the reference element 100a not formed with the opening and is connected to the terminal A of the bridge circuit, a wiring pattern B1 that connects the first terminal TE1 of the hydrogen sensor 100 and the terminal B of the bridge circuit, and a wiring pattern D1 that connects the first terminal TE1 of the reference element 100a and the terminal D of the bridge circuit.

[0060] Figure 5 1 is a flowchart showing a method for manufacturing the hydrogen detection device 10 according to the embodiment. Figure 4A The method for manufacturing the hydrogen sensor 100 and the reference element 100a among the four resistor elements of the hydrogen detection device 10 shown.

[0061] Film formation and photolithography (pattern transfer and etching) are repeatedly performed on the semiconductor substrate to form a stacked body of the hydrogen sensor 100 and the reference element 100a, thereby forming, from the bottom layer, an insulating film 102 such as HDP-FSG (fluorine-doped glass based on high density plasma), an insulating film 107a as an interlayer insulating film such as P-TEOS (tetraethoxysilane based on plasma), a first electrode 103 such as TaN or TiN, and a TaN-based insulating film 107a. 2 O 5 with TaO 1.5 The stacked body is composed of a metal oxide layer 104 composed of a stacked body of a plurality of electrodes, such as a Pt second electrode 106, a metal layer 106s such as TiAlN, an insulating film 107b as an interlayer insulating film such as P-TEOS, an insulating film 109a as a protective film such as P-SiON (plasma-based silicon nitride oxide film), a first terminal TE1 and a second terminal TE2 as electrodes such as Au, an insulating film 107c as an interlayer insulating film such as HDP-NSG (high-density plasma-doped nitrogen-doped glass), and an insulating film 109b as a protective film such as P-SiON (stacked body forming step S10). Through this process, an intermediate product of the hydrogen sensor 100 before the opening 106a is formed and a completed product of the reference element 100a are manufactured.

[0062] Next, by photolithography (pattern transfer and etching) of the intermediate product of the hydrogen sensor 100, the metal layer 106s, the insulating film 107b, the insulating film 109a, the insulating film 107c, and a portion of the insulating film 109b are removed in a rectangular shape so that the upper surface of the second electrode 106 is exposed, thereby forming the opening 106a of the hydrogen sensor 100 (opening formation step S11). Through this process, the hydrogen sensor 100 is completed.

[0063] Next, experimental results related to the characteristics of the hydrogen detection device 10 of the present embodiment manufactured as described above will be described.

[0064] Figure 6 Graphs showing experimental results regarding the time dependency and distance dependency of the output voltage (difference voltage) of the hydrogen detection device 10 according to the embodiment.

[0065] Figure 6 (a) is in the absence of hydrogen, Figure 4A The distance between the hydrogen sensor 100 and the reference element 100a in the plan view of the hydrogen detection device 10 is changed as a parameter, and the time (horizontal axis) dependence of the differential voltage (vertical axis) appearing between the terminals BD of the bridge circuit is recorded. Regarding the distance, samples of the hydrogen detection device 10 with distances of 27 μm, 1920 μm, 3300 μm, 5220 μm, and 6600 μm were prepared, and the differential voltage was measured.

[0066] As shown in this figure, when the distance is 27μm and 1920μm, the differential voltage is almost 0 (V), indicating an ideal value, but when the distance is 3300μm, 5220μm, and 6600μm, the differential voltage shows a significant value (i.e., offset voltage) that deviates from the ideal value. In addition, at any distance, the differential voltage hardly changes over time.

[0067] Figure 6 (b) is to Figure 6 The results obtained in (a) are rewritten as a graph showing the distance (horizontal axis) dependence of the differential voltage (vertical axis).

[0068] As can be seen from this figure, in an environment where hydrogen does not exist, when the distance in a plan view between the hydrogen sensor 100 and the reference element 100a constituting the bridge circuit is approximately 2000 μm or less, the differential voltage output from the bridge circuit stably becomes 0 (V) as an ideal value regardless of time, but when the distance exceeds 2000 μm, the differential voltage output from the bridge circuit becomes a significant voltage that deviates from the ideal value. It is believed that this is because the hydrogen sensor 100 and the reference element 100a are formed on the same semiconductor chip 12 and have basically the same structure, but when they are separated by a certain distance or more, the highly sensitive bridge circuit detects a slight difference in the characteristics of the structure caused by the difference in the configuration position in the semiconductor chip 12.

[0069] This shows that when the distance between the hydrogen sensor 100 and the reference element 100a constituting the bridge circuit in a plan view is approximately 2000 μm or less, no offset voltage is generated due to the distance between them, and highly sensitive and stable hydrogen detection can be performed using the bridge circuit.

[0070] Figure 7 This is a graph showing the experimental results of the reaction of the hydrogen detection device 10 of the embodiment to hydrogen. Here, for the hydrogen detection device 10 in which the distance between the hydrogen sensor 100 and the reference element 100a is 27μm, after confirming that the differential voltage is 0mV in an environment without hydrogen, the hydrogen concentration of the environment of the hydrogen detection device 10 is set to 0.01% for 300msec, and then replaced with 100% air (i.e., hydrogen concentration 0%) for 600msec, then the hydrogen concentration is set to 0.1% for 300msec, and then replaced with 100% air (i.e., hydrogen concentration 0%) for 600msec, then the hydrogen concentration is set to 1.0% for 300msec, and then replaced with 100% air (i.e., hydrogen concentration 0%). The differential voltage (vertical axis) output by the hydrogen detection device 10 is shown. In addition, the concentration value is a percentage (%) of the volume ratio of the gas.

[0071] As shown in this figure, the hydrogen detection device 10, which includes the hydrogen sensor 100 and the reference element 100a arranged at a distance of 27 μm, outputs a differential voltage following the change in the hydrogen concentration of the environment. In particular, the differential voltage output from the hydrogen detection device 10 returns to a base voltage of 0 mV when the environment becomes hydrogen-free after reacting with hydrogen, and no offset voltage is generated.

[0072] In addition, in this experimental example, the distance between the hydrogen sensor 100 and the reference element 100 a is 27 μm, but it is estimated that the same result can be obtained if the distance is 2000 μm or less.

[0073] Next, hydrogen detection devices according to various modified examples of the embodiment will be described.

[0074] Figure 8 1 is a schematic diagram showing an overall configuration example of a hydrogen detection device 10a according to a first modification of the embodiment. Figure 4A Compared with the hydrogen detection device 10 of the illustrated embodiment, the difference lies in that, in the hydrogen detection device 10a of variant example 1, only the hydrogen sensor 100 and the reference element 100a of the four resistance elements constituting the bridge circuit are formed on a semiconductor chip 12, and the other two resistors R1 and R2 are mounted on the outside of the semiconductor chip 12 (printed substrate, etc. not shown).

[0075] Even in the hydrogen detection device 10a of the modified example 1 of the embodiment, the hydrogen sensor 100 and the reference element 100a are formed on one semiconductor chip 12, and basically have the same structure, and the distance between them in a plan view is less than 2000 μm, which is the same as the hydrogen detection device 10 of the embodiment, so it is considered to have the same characteristics as the hydrogen detection device 10 of the embodiment ( Figure 6 and Figure 7 characteristics shown).

[0076] Fig. 9A 1 is a schematic diagram showing an overall configuration example of a hydrogen detection device 10b according to a second modification of the embodiment. Figure 4A Compared with the hydrogen detection device 10 of the embodiment shown, the difference is that in the hydrogen detection device 10b of variant example 2, during the manufacturing process, the reference element 100b is temporarily formed with an opening 110a that is the same as the opening 106a of the hydrogen sensor 100, and then the inner side surface and bottom surface of the opening 110a are covered with a hydrogen impermeable membrane 110.

[0077] Fig. 9B Yes means Fig. 9A 1 is a plan view of a layout example of the wiring patterns of the hydrogen sensor 100 and the reference element 100b in the hydrogen detection device 10b shown in FIG. In this plan view, there are shown a wiring pattern A1 that connects the second terminal TE2 of the hydrogen sensor 100 formed with the opening 106a and the second terminal TE2 of the reference element 100b formed with the opening 110a and is connected to the terminal A of the bridge circuit, a wiring pattern B1 that connects the first terminal TE1 of the hydrogen sensor 100 and the terminal B of the bridge circuit, and a wiring pattern D1 that connects the first terminal TE1 of the reference element 100b and the terminal D of the bridge circuit.

[0078] Even in the hydrogen detection device 10b of the second modification of the embodiment, the hydrogen sensor 100 and the reference element 100b are formed on one semiconductor chip 12, and basically have the same structure, and the distance between them in a plan view is less than 2000 μm, which is the same as the hydrogen detection device 10 of the embodiment, so it is considered to have the same characteristics as the hydrogen detection device 10 of the embodiment ( Figure 6 and Figure 7 characteristics shown).

[0079] Fig.10 This is a flowchart showing a method for manufacturing a hydrogen detection device 10b according to a second variation of the embodiment. Fig. 9A The method for manufacturing the hydrogen sensor 100 and the reference element 100b among the four resistor elements of the hydrogen detection device 10b shown in FIG.

[0080] Film formation and photolithography (pattern transfer and etching) are repeatedly performed on the semiconductor substrate to form a stacked body of the hydrogen sensor 100 and the reference element 100b, thereby forming, from the bottom layer, an insulating film 102 made of HDP-FSG (fluorine-doped glass based on high density plasma), an insulating film 107a as an interlayer insulating film such as P-TEOS (tetraethoxysilane based on plasma), a first electrode 103 made of TaN or TiN, and a TaN-based insulating film 107a. 2 O5 with TaO 1.5 The stacked body is composed of a metal oxide layer 104 composed of a stacked body of a metal oxide layer 104, a second electrode 106 such as Pt, a metal layer 106s such as TiAlN, an insulating film 107b as an interlayer insulating film such as P-TEOS, an insulating film 109a as a protective film such as P-SiON (plasma-based silicon nitride oxide film), a first terminal TE1 and a second terminal TE2 as electrodes such as Au, an insulating film 107c as an interlayer insulating film such as HDP-NSG (high-density plasma-doped nitrogen-doped glass), and an insulating film 109b as a protective film such as P-SiON (stacked body formation step S20). Through this process, an intermediate product of the hydrogen sensor 100 before the opening 106a is formed and an intermediate product of the reference element 100b before the opening 110a is formed are produced.

[0081] Next, the metal layer 106s, the insulating film 107b, the insulating film 109a, the insulating film 107c, and a portion of the insulating film 109b are removed in a rectangular shape by photolithography (pattern transfer and etching) to expose the upper surface of the second electrode 106 relative to the intermediate product of the hydrogen sensor 100 and the intermediate product of the reference element 100b, respectively, thereby forming the opening 106a of the hydrogen sensor 100 and the opening 110a of the reference element 100b (opening formation step S21). Through this process, the hydrogen sensor 100 is completed.

[0082] Finally, the inner side and bottom of the opening 110a formed in the reference element 100b are covered with a hydrogen impermeable film 110 such as P-SiON (hydrogen impermeable film forming step S22). Through this process, the reference element 100b having the opening 110a whose inner side and bottom are covered with the hydrogen impermeable film 110 is completed. In addition, the formation of the hydrogen impermeable film 110 may be performed in the same process as the formation of the insulating film 109b (i.e., film formation using the same material).

[0083] Fig.11 : is a schematic diagram showing an overall configuration example of a hydrogen detection device 10c according to a third modification of the embodiment. Fig. 9A Compared with the hydrogen detection device 10b of the variant 2 of the embodiment shown, the difference is that in the hydrogen detection device 10c of the variant 3, only the hydrogen sensor 100 and the reference element 100b of the four resistance elements constituting the bridge circuit are formed on a semiconductor chip 12, and the other two resistors R1 and R2 are mounted on the outside of the semiconductor chip 12 (printed substrate, etc. not shown).

[0084] Even in the hydrogen detection device 10c of the modified example 3 of the embodiment, the hydrogen sensor 100 and the reference element 100b are formed on one semiconductor chip 12, have basically the same structure, and the distance between them in a plan view is less than 2000 μm, which is the same as the hydrogen detection device 10 of the embodiment, and therefore it is considered to have the same characteristics as the hydrogen detection device 10 of the embodiment ( Figure 6 and Figure 7 characteristics shown).

[0085] As described above, the hydrogen detection device 10 of the embodiment etc. includes the hydrogen sensor 100 as the first resistance element, the resistor R1 as the second resistance element, the reference element 100a as the third resistance element, and the resistor R2 as the fourth resistance element constituting a bridge circuit, one end of the hydrogen sensor 100 is connected to one end of the resistor R1, one end of the reference element 100a is connected to one end of the resistor R2, the other end of the hydrogen sensor 100 is connected to the other end of the reference element 100a, and the other end of the resistor R1 is connected to the other end of the resistor R2, and at least the hydrogen sensor 100 and the reference element 100a among the hydrogen sensor 100, the resistor R1, the reference element 100a, and the resistor R2 are formed on one semiconductor chip 12. The hydrogen sensor 100 includes a first electrode 103 and a second electrode 106 whose main surfaces are arranged facing each other, and a first metal oxide layer ( Figure 2A The metal oxide layer 104 covers the first electrode 103, the second electrode 106 and the first metal oxide layer ( Figure 2A The first insulating film has an opening 106a that allows the other surface of the second electrode 106, which is opposite to the main surface, to be exposed without being covered by the first insulating film. The reference element 100a has a third electrode ( Figure 3 The first electrode 103) and the fourth electrode ( Figure 3 The second electrode 106), and the third electrode ( Figure 3 The first electrode 103) and the fourth electrode ( Figure 3 The second metal oxide layer ( Figure 3 The metal oxide layer 104), and the third electrode ( Figure 3 The first electrode 103), the fourth electrode ( Figure 3 The second electrode 106) and the second metal oxide layer ( Figure 3 The second insulating film (metal oxide layer 104) Figure 3 The second insulating film does not have the fourth electrode ( Figure 3 An opening in which the other surface of the second electrode 106) opposite to the main surface is not covered by the second insulating film and is exposed.

[0086] Thus, the hydrogen sensor 100 and the reference element 100a constituting the highly sensitive bridge circuit are resistance variable elements having basically the same structure and are formed on one semiconductor chip 12. Therefore, in an environment without hydrogen, they show extremely close resistance values. In an environment with hydrogen, the resistance balance of the bridge circuit constituted by them is destroyed, and a potential difference is generated between the connection points of the two locations. Therefore, a hydrogen detection device that does not necessarily require a heater and can operate stably can be realized.

[0087] In addition, the distance between the hydrogen sensor 100 and the reference element 100a is 2000 μm or less in the plan view of the second electrode 106. This can reliably suppress the characteristic difference caused by the difference in the arrangement positions of the hydrogen sensor 100 and the reference element 100a in the semiconductor chip 12, and realize a highly accurate hydrogen detection device that can operate reliably and stably.

[0088] The hydrogen sensor 100 has a first terminal TE1 and a second terminal TE2 connected to the other surface of the second electrode 106 via the through hole 108 as one end and the other end of the hydrogen sensor 100. Thus, the hydrogen sensor 100 can be used in a highly sensitive horizontal mode, thereby realizing a hydrogen detection device suitable for detecting low-concentration hydrogen.

[0089] In addition, the opening 106a is formed between the first terminal TE1 and the second terminal TE2 in a plan view of the second electrode 106. Thus, the opening 106a is located on the path of the current, and the resistance change in the opening 106a can be reliably detected.

[0090] Furthermore, the hydrogen sensor 100 may include, as one of the one end and the other end of the hydrogen sensor 100, a terminal (first terminal TE1 or second terminal TE2) connected to the other surface of the second electrode 106 via the through hole 108, and a third terminal BE connected to the other surface of the first electrode 103 opposite to the main surface via the through hole 108. Thus, the sensitivity of the hydrogen sensor 100 is lower than when used in the horizontal mode, and thus a hydrogen detection device suitable for detecting high-concentration hydrogen can be realized.

[0091] In the hydrogen detection device 10b of the second modification, the second insulating film in the reference element 100b has a second opening ( 106a ) whose inner side and bottom are covered by the hydrogen impermeable film 110 at a position corresponding to the opening 106a in the first insulating film of the hydrogen sensor 100. Fig. 9AThus, in the manufacture of the hydrogen sensor 100 and the reference element 100b, a process of forming the opening can be provided in common, and the manufacturing process for the opening can be made common.

[0092] In addition, in the hydrogen detection device 10 of the embodiment, the hydrogen sensor 100, the resistor R1, the reference element 100a, and the resistor R2 are formed on one semiconductor chip 12. Thus, a small-sized hydrogen detection device is realized.

[0093] In addition, the hydrogen detection device 10 and the like according to the embodiment are provided with a hydrogen sensor 100 as a first resistance element, a resistor R1 as a second resistance element, a reference element 100a as a third resistance element, and a resistor R2 as a fourth resistance element constituting a bridge circuit, and a manufacturing method of the hydrogen detection device 10 includes: a stacked body forming step S20 of forming a stacked body for the hydrogen sensor 100 and the reference element 100a; and an opening forming step S21 of forming an opening in the stacked body formed, and in the stacked body forming step S20, an opening is formed as a stacked body for the hydrogen sensor 100 and the reference element 100a. A stacked body is formed to form a stacked body consisting of: a first electrode 103 and a second electrode 106, whose main surfaces are arranged opposite to each other; a metal oxide layer 104, which is arranged in contact with the main surface of the first electrode 103 and the main surface of the second electrode 106; and an insulating film 107b, etc., which covers the first electrode 103, the second electrode 106 and the metal oxide layer 104. In the opening forming step S21, at least for the stacked body of the hydrogen sensor 100, a first opening (opening 106a) is formed on the insulating film 107b, etc. so that the other surface of the second electrode 106 opposite to the main surface is not covered by the insulating film 107b, etc. and is exposed.

[0094] Thus, the hydrogen sensor 100 and the reference element 100 a constituting a highly sensitive bridge circuit are variable resistance elements having basically the same structure and are formed on one semiconductor chip 12 , so that a hydrogen detection device capable of stable operation without necessarily requiring a heater can be manufactured.

[0095] In addition, in the hydrogen detection device 10b of the second modification example, in the opening forming step S21, in addition to the stacked body of the hydrogen sensor 100, the second opening (110a) is formed in the insulating film 107b etc. so that the other surface of the second electrode 106 opposite to the main surface is not covered by the insulating film 107b etc. and is exposed, and the manufacturing method of the hydrogen detection device further includes a hydrogen impermeable film forming step S22 of covering the inner side surface and the bottom surface of the formed second opening (110a) with the hydrogen impermeable film 110. Thus, in the manufacturing of the hydrogen sensor 100 and the reference element 100b, the process of forming the opening can be provided in common, and the process of the opening can be made common.

[0096] The hydrogen detection device and the manufacturing method thereof according to the present invention are described above based on the embodiments and the variants, but the present invention is not limited to these embodiments and the variants. As long as it does not deviate from the main purpose of the present invention, the various modifications thought of by those skilled in the art are implemented in the present embodiment and the variants, and other methods constructed by combining the constituent elements of part of the embodiments and the variants are also included in the scope of the present invention.

[0097] In the above-mentioned embodiment and modification, the distance between the hydrogen sensor 100 and the reference element 100a is 2000 μm or less, but it is not necessarily necessary to be less than this distance. This is because if the hydrogen sensor 100 and the reference element 100a having basically the same structure are formed on the same semiconductor chip 12, they have extremely similar characteristics, so even if the distance between the hydrogen sensor 100 and the reference element 100a exceeds 2000 μm, depending on the concentration of hydrogen to be detected, sometimes the tiny offset voltage output by the bridge circuit will not become an obstacle.

[0098] In addition, when detecting low concentrations of hydrogen and suppressing the offset voltage output by the bridge circuit, as long as the distance between the other hydrogen sensor 100 and the reference element 100a is less than 2000μm, it can also be any distance, such as less than 1500μm, less than 1000μm, less than 500μm, less than 100μm, less than 50μm, less than 30μm, the minimum distance in the manufacturing process, etc.

[0099] In addition, in the above-mentioned embodiments and variations, an example is shown in which only a hydrogen detection device is formed on the semiconductor chip 12, but circuits other than the hydrogen detection device may also be formed, such as a buffer amplifier for amplifying the differential voltage output by the bridge circuit, a constant voltage power supply circuit for generating a voltage applied to the bridge circuit, etc.

[0100] [Industrial Availability]

[0101] The hydrogen detection device of the present invention can be used as a highly sensitive and stably operating hydrogen detection device using a bridge circuit, and can be used as a hydrogen detection device mounted on a fuel cell vehicle, for example.

[0102] Explanation of symbols

[0103] 10. 10a~10c Hydrogen detection device

[0104] 12Semiconductor Chips

[0105] 20Voltmeter

[0106] 21 DC voltage source

[0107] 100 Hydrogen sensor (first resistor element)

[0108] 100a, 100b reference element (third resistance element)

[0109] 102 insulation film

[0110] 103 first electrode

[0111] 104 Metal oxide layer

[0112] 104a1st floor

[0113] 104b Second floor

[0114] 104i Insulation separation layer

[0115] 106 second electrode

[0116] 106a, 110a, TE1a, TE2a, BEa openings

[0117] 106e exposed part

[0118] 106s metal layer

[0119] 107a, 107b, 107c, 109a, 109b insulation films

[0120] 108 through holes

[0121] 110 Hydrogen Impermeable Membrane

[0122] 114 Wiring

[0123] TE1 first terminal

[0124] TE2 second terminal

[0125] BE third terminal

[0126] R1, R2 resistors

[0127] A to D terminals

Claims

1. A hydrogen detection device, comprising: a first resistance element, a second resistance element, a third resistance element, and a fourth resistance element constituting a bridge circuit, One end of the first resistance element is connected to one end of the second resistance element, One end of the third resistor element is connected to one end of the fourth resistor element, The other end of the first resistor element is connected to the other end of the third resistor element, The other end of the second resistor element is connected to the other end of the fourth resistor element, At least the first resistance element and the third resistance element among the first resistance element, the second resistance element, the third resistance element and the fourth resistance element are formed in one semiconductor chip, The first resistive element is a hydrogen sensor having: The first electrode and the second electrode have their main surfaces arranged facing each other; A first metal oxide layer is arranged in contact with the main surface of the first electrode and the main surface of the second electrode; as well as a first insulating film covering the first electrode, the second electrode and the first metal oxide layer, The first insulating film has a first opening that exposes the other surface of the second electrode that is opposite to the main surface without being covered by the first insulating film. The third resistance element is a reference element having: The third electrode and the fourth electrode have their main surfaces arranged facing each other; A second metal oxide layer is arranged in contact with the main surface of the third electrode and the main surface of the fourth electrode; as well as a second insulating film covering the third electrode, the fourth electrode and the second metal oxide layer, The second insulating film does not have an opening that exposes the other surface of the fourth electrode that is opposite to the main surface without being covered by the second insulating film.

2. The hydrogen detection device according to claim 1, In a plan view of the second electrode, a distance between the first resistance element and the third resistance element is 2000 μm or less.

3. The hydrogen detection device according to claim 1 or 2, The first resistance element has a first terminal and a second terminal connected to the other surface of the second electrode via a through hole as one end and the other end of the first resistance element.

4. The hydrogen detection device according to claim 3, In a plan view of the second electrode, the first opening is formed between the first terminal and the second terminal.

5. The hydrogen detection device according to claim 1 or 2, The first resistor element has, as one end and the other end, a terminal connected to the other surface of the second electrode via a through hole, and a third terminal connected to the other surface of the first electrode opposite to the main surface via a through hole.

6. The hydrogen detection device according to any one of claims 1 to 5, The second insulating film has a second opening whose inner side surface and bottom surface are covered with a hydrogen impermeable film at a position corresponding to the first opening of the first insulating film.

7. The hydrogen detection device according to any one of claims 1 to 6, The first resistance element, the second resistance element, the third resistance element, and the fourth resistance element are formed in the one semiconductor chip.

8. A method for manufacturing a hydrogen detection device, A method for manufacturing a hydrogen detection device including a first resistor element as a hydrogen sensor, a second resistor element, a third resistor element as a reference element, and a fourth resistor element constituting a bridge circuit. The manufacturing method of the hydrogen detection device comprises: a stacked body forming step of forming a stacked body for the first resistor element and the third resistor element; as well as an opening forming step of forming an opening in the formed laminated body, In the stacked body forming step, as a stacked body for the first resistor element and the third resistor element, a stacked body consisting of: a first electrode and a second electrode, main surfaces of which are arranged opposite to each other; a metal oxide layer arranged in contact with the main surface of the first electrode and the main surface of the second electrode; and an insulating film covering the first electrode, the second electrode and the metal oxide layer is formed, In the opening forming step, at least for the stacked body of the first resistor element, a first opening is formed in the insulating film so that the other surface of the second electrode opposite to the main surface is not covered by the insulating film and is exposed.

9. The method for manufacturing a hydrogen detection device according to claim 8, In the opening forming step, in addition to the stack of the first resistor element, a second opening is formed in the insulating film so that the other surface of the second electrode opposite to the main surface is not covered by the insulating film and is exposed, The method for manufacturing a hydrogen detecting device further includes a hydrogen impermeable film forming step of covering the inner side surface and the bottom surface of the formed second opening with a hydrogen impermeable film.

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