Thermistor element and electromagnetic wave sensor

Abstract

To provide a thermistor element capable of reducing a resistance value of a thermistor film.SOLUTION: A thermistor element includes a thermistor film 5, a first electrode 6a provided in contact with one surface of the thermistor film 5, and a pair of second electrodes 6b provided in contact with the other surface of the thermistor film 5, and the thermistor film 5 is composed of an oxide having a spinel-type crystal structure and is [111] preferentially oriented in the film thickness direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a thermistor element and an electromagnetic wave sensor. [Background technology]

[0002] For example, there is a temperature sensor using a thermistor element (see, for example, Patent Document 1 below). There is also an electromagnetic wave sensor using a thermistor element (see, for example, Patent Document 2 below).

[0003] The electrical resistance of the thermistor film in a thermistor element changes in response to changes in the temperature of the thermistor film. In an electromagnetic wave sensor, infrared rays (electromagnetic waves) incident on the thermistor film are absorbed by the thermistor film or the material surrounding the thermistor film, causing the temperature of the thermistor film to change. This allows the thermistor element to detect infrared rays (electromagnetic waves).

[0004] According to the Stefan-Boltzmann law, there is a correlation between the temperature of the object being measured and the infrared radiation (radiant heat) emitted from the object by thermal radiation. Therefore, by detecting the infrared radiation emitted from the object using a thermistor element, it is possible to measure the temperature of the object without contact.

[0005] Furthermore, such thermistor elements are arranged in an array and are used in electromagnetic wave sensors such as infrared imaging elements (infrared image sensors) that two-dimensionally detect (image) the temperature distribution of a measurement object. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-348903 [Patent Document 2] International Publication No. 2019 / 171488 Summary of the Invention [Problem to be solved by the invention]

[0007] The thermistor element described in Patent Document 1 employs a current-in-plane (CIP) structure in which current flows in the in-plane direction of the thermistor film. However, because the resistance of the thermistor film is high in the CIP structure, as the device is made smaller, the resistance of the thermistor film between the electrodes becomes excessively large, making it difficult to extract a detection signal.

[0008] The present invention has been proposed in light of the above-mentioned conventional circumstances, and aims to provide a thermistor element that reduces the resistance value of the thermistor film, allowing for further miniaturization, and an electromagnetic wave sensor that is equipped with such a thermistor element, allowing for further miniaturization. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides the following means. (1) a thermistor film; a first electrode provided in contact with one surface of the thermistor film; a pair of second electrodes provided in contact with the other surface of the thermistor film; The thermistor film is made of an oxide having a spinel crystal structure and has a

[0111] preferred orientation in the film thickness direction. 、 The phrase "preferentially oriented in the film thickness direction" means that in a θ-2θ scan by out-of-plane measurement using an X-ray diffraction method, the diffraction peak intensity from the (111) plane of the spinel crystal structure is greater than the diffraction peak intensity from other crystal planes, or that in a θ-2θ scan by out-of-plane measurement using an X-ray diffraction method, only the diffraction peak from the (111) plane of the spinel crystal structure is observed. A thermistor element characterized by: (2) An electromagnetic wave sensor comprising the thermistor element described in (1). (3) The electromagnetic wave sensor according to (2) above, wherein the thermistor elements are arranged in a plurality of arrays. [Effects of the Invention]

[0010] As described above, according to the present invention, it is possible to provide a thermistor element that reduces the resistance value of the thermistor film, allowing for further miniaturization, and an electromagnetic wave sensor that is equipped with such a thermistor element, allowing for further miniaturization. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a plan view showing the configuration of a thermistor element according to an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view of the thermistor element taken along line AA shown in FIG. 1. [Figure 3] 2 is a plan view showing the configuration of an electromagnetic wave sensor including the thermistor element shown in FIG. [Figure 4] FIG. 4 is an exploded perspective view showing the configuration of the electromagnetic wave sensor shown in FIG. [Figure 5] FIG. 4 is a cross-sectional view showing the configuration of the electromagnetic wave sensor shown in FIG. [Figure 6] 1 is a graph showing the measurement results of the thermistor film in Example 1 by X-ray diffraction. [Figure 7] 1 is a graph showing the measurement results of the thermistor film in Comparative Example 1 by X-ray diffraction. [Figure 8] 10 is a graph showing the measurement results of the thermistor film in Example 2 by X-ray diffraction. [Figure 9] 10 is a graph showing the measurement results of the thermistor film in Comparative Example 2 by X-ray diffraction. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, the dimensions of the components may be shown at different scales to make them easier to see, and the dimensional ratios of the components may not necessarily be the same as in reality. Furthermore, the materials exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate changes within the scope of the present invention.

[0013] [Thermistor element] First, as one embodiment of the present invention, a thermistor element 4 shown in, for example, FIGS. 1 and 2 will be described. 1 is a plan view showing the configuration of thermistor element 4. FIG. 2 is a cross-sectional view of thermistor element 4 taken along line AA shown in FIG.

[0014] 1 and 2, the thermistor element 4 of this embodiment includes a thermistor film 5, a first electrode 6a provided in contact with one surface (the bottom surface in FIG. 2) of the thermistor film 5, and a pair of second electrodes 6b provided in contact with the other surface (the top surface in FIG. 2) of the thermistor film 5, and has a current-perpendicular-to-plane (CPP) structure in which current flows perpendicular to the surface of the thermistor film 5. The first electrode 6a and the second electrode 6b are arranged to sandwich the thermistor film 5, and the second electrode 6b faces the first electrode 6a in the film thickness direction of the thermistor film 5.

[0015] That is, in this thermistor element 4, it is possible to pass a current in a direction perpendicular to the surface of the thermistor film 5 from one second electrode 6b to the first electrode 6a, and also to pass a current in a direction perpendicular to the surface of the thermistor film 5 from the first electrode 6a to the other second electrode 6b.

[0016] The resistance value of the thermistor film 5 depends on the thickness of the thermistor film 5 and the opposing area between the first electrode 6a and the second electrode 6b. Therefore, by adopting the above-mentioned CPP structure, it is possible to reduce the resistance of the thermistor film 5 compared to the CIP structure.

[0017] The thermistor element 4 of this embodiment is characterized in that the thermistor film 5 is made of an oxide having a spinel crystal structure and has a preferred orientation of

[0111] in the film thickness direction of the thermistor film 5. The thermistor film 5 has a preferred orientation of

[0111] in the film thickness direction in the portion sandwiched between the first electrode 6a and the second electrode 6b.

[0018] Here, "preferentially oriented in the

[0111] direction in the film thickness direction" means that in a θ-2θ scan by out-of-plane measurement using X-ray diffraction, the diffraction peak intensity from the (111) plane of the spinel crystal structure is greater than the diffraction peak intensity from other crystal planes, or that in a θ-2θ scan by out-of-plane measurement using X-ray diffraction, only the diffraction peak from the (111) plane of the spinel crystal structure is observed.

[0019] The thermistor element 4 of this embodiment is not necessarily limited to a thermistor film 5 containing 100% oxide having a spinel crystal structure with a preferred orientation of

[0111] in the film thickness direction, and it is preferable that the proportion be at least 70% or more.

[0020] An oxide having a spinel crystal structure containing cobalt (Co), manganese (Mn), aluminum (Al) and at least one transition element is preferably used for the thermistor film 5. The transition element is preferably at least one of nickel (Ni), copper (Cu) and iron (Fe).

[0021] Furthermore, it is preferable to use an oxide having a spinel crystal structure containing nickel (Ni), manganese (Mn), aluminum (Al) and at least one transition element as the thermistor film 5. Furthermore, it is preferable that the transition element is at least one of cobalt (Co), copper (Cu) and iron (Fe).

[0022] The main component metal element is "Co and Mn" or "Ni and Mn" among the metal elements constituting the thermistor film 5. The main component metal element can be located in either the A site or the B site of the spinel crystal structure represented by the general formula AB2O4.

[0023] On the other hand, the minor component metal elements are “Al and transition elements.” The minor component transition elements can be located in either the A site or the B site, but Al is mainly located in the B site.

[0024] The first electrode 6a and the second electrode 6b can be made of, for example, a conductive film of platinum (Pt), gold (Au), palladium (Pd), ruthenium (Ru), silver (Ag), rhodium (Rh), iridium (Ir), osmium (Os), etc. Furthermore, by using platinum (Pt) with a preferred orientation in the film thickness direction for the first electrode 6a, it is possible to give the thermistor film 5 formed on the surface of the first electrode 6a a preferred orientation in the film thickness direction.

[0025] In the thermistor element 4 of this embodiment, the above-mentioned thermistor film 5 is made of an oxide having a spinel crystal structure, and this thermistor film 5 has a preferred orientation of

[0111] in the film thickness direction, which makes it possible to reduce the resistance value of the thermistor film 5 between the first electrode 6a and the second electrode 6b.

[0026] [Electromagnetic wave sensor] Next, an electromagnetic wave sensor 1 shown in, for example, FIGS. 3 to 5 will be described as one embodiment of the present invention. 3 is a plan view showing the configuration of the electromagnetic wave sensor 1. FIG. 4 is an exploded perspective view showing the configuration of the electromagnetic wave sensor 1. FIG. 5 is a cross-sectional view showing the configuration of the electromagnetic wave sensor 1.

[0027] In the drawings shown below, an XYZ Cartesian coordinate system is set, with the X-axis direction being a first direction X within a specific plane of the electromagnetic wave sensor 1, the Y-axis direction being a second direction Y that is perpendicular to the first direction X within the specific plane of the electromagnetic wave sensor 1, and the Z-axis direction being a third direction Z that is perpendicular to the specific plane of the electromagnetic wave sensor 1.

[0028] The electromagnetic wave sensor 1 of this embodiment is an application of the present invention to an infrared imaging element (infrared image sensor) that detects infrared rays (electromagnetic waves) emitted from the object to be measured, thereby detecting (imaging) the temperature distribution of the object to be measured in two dimensions.

[0029] Infrared rays are electromagnetic waves with wavelengths between 0.75 μm and 1000 μm. Infrared image sensors are used as infrared cameras for indoor and outdoor night vision, as well as non-contact temperature sensors for measuring the temperature of people and objects.

[0030] Specifically, as shown in Figures 3 to 5, this electromagnetic wave sensor 1 comprises a first substrate 2 and a second substrate 3 arranged opposite each other, and a plurality of thermistor elements 4 arranged between the first substrate 2 and the second substrate 3.

[0031] The first substrate 2 and the second substrate 3 are made of a silicon substrate that is transparent to electromagnetic waves of a certain wavelength (long wavelength infrared rays with wavelengths of 8 to 14 μm in this embodiment) (hereinafter referred to as "infrared rays") IR. Furthermore, a germanium substrate or the like can be used as a substrate that is transparent to infrared rays IR.

[0032] The first substrate 2 and the second substrate 3 are sealed around the periphery of their opposing surfaces with a sealant (not shown), thereby forming a sealed internal space K between them. The internal space K is also depressurized to a high vacuum. This suppresses the influence of heat due to convection in the internal space K in the electromagnetic wave sensor 1, and eliminates the influence of heat other than infrared rays IR emitted from the measurement object on the thermistor element 4.

[0033] The electromagnetic wave sensor 1 of this embodiment is not necessarily limited to a configuration in which the sealed internal space K described above is reduced in pressure, but may also be configured to have a sealed or open internal space K at atmospheric pressure.

[0034] The thermistor element 4 comprises a thermistor film 5 that detects infrared rays IR, a first electrode 6a provided in contact with one surface of the thermistor film 5, a pair of second electrodes 6b provided in contact with the other surface of the thermistor film 5, and a dielectric film 7 that covers the thermistor film 5, and has a CPP (Current-Perpendicular-to-Plane) structure in which current flows perpendicular to the surface of the thermistor film 5.

[0035] The dielectric film 7 may be made of, for example, aluminum nitride, silicon nitride, aluminum oxide, silicon oxide, magnesium oxide, tantalum oxide, niobium oxide, hafnium oxide, zirconium oxide, germanium oxide, yttrium oxide, tungsten oxide, bismuth oxide, calcium oxide, aluminum oxynitride, silicon oxynitride, aluminum magnesium oxide, silicon boride, boron nitride, or sialon (an oxynitride of silicon and aluminum).

[0036] The dielectric film 7 may be configured to cover at least a part of the thermistor film 5. In this embodiment, the dielectric film 7 is provided to cover both surfaces of the thermistor film 5.

[0037] The multiple thermistor elements 4 are formed to be the same size and rectangular (square in this embodiment) in plan view. The multiple thermistor elements 4 are arranged in an array in a plane parallel to the first substrate 2 and the second substrate 3 (hereinafter referred to as "in a specific plane"). That is, the multiple thermistor elements 4 are arranged in a matrix in a first direction X and a second direction Y that intersect each other (orthogonal in this embodiment) in the specific plane.

[0038] The thermistor elements 4 are arranged side by side at regular intervals in the first direction X, with the first direction X being the row direction, and the second direction Y being the column direction, and are also arranged side by side at regular intervals in the second direction Y.

[0039] The matrix number of the thermistor element 4 may be, for example, 640 rows x 480 columns, or 1024 rows x 768 columns, but is not necessarily limited to these matrix numbers and can be changed as appropriate.

[0040] On the first substrate 2 side, there are provided a first insulator layer 8, a wiring section 9 electrically connected to the circuit section 15 described later, and a first connection section 10 electrically connecting each thermistor element 4 and the wiring section 9.

[0041] The first insulator layer 8 is made of an insulating film laminated on one surface (the surface facing the second substrate 3) of the first substrate 2. Examples of insulating films that can be used include aluminum nitride, silicon nitride, aluminum oxide, silicon oxide, magnesium oxide, tantalum oxide, niobium oxide, hafnium oxide, zirconium oxide, germanium oxide, yttrium oxide, tungsten oxide, bismuth oxide, calcium oxide, aluminum oxynitride, silicon oxynitride, aluminum magnesium oxide, silicon boride, boron nitride, and sialon (an oxynitride of silicon and aluminum).

[0042] The wiring section 9 has a plurality of first lead wires 9a and a plurality of second lead wires 9b. The first lead wires 9a and the second lead wires 9b are made of a conductive film such as copper or gold.

[0043] The first lead wires 9a and the second lead wires 9b are located in different layers of the first insulator layer 8 in the third direction Z and are arranged to intersect three-dimensionally. Of these, the first lead wires 9a extend in the first direction X and are arranged side by side at regular intervals in the second direction Y. On the other hand, the second lead wires 9b extend in the second direction Y and are arranged side by side at regular intervals in the first direction X.

[0044] In plan view, each thermistor element 4 is provided in an area defined by the plurality of first lead wires 9a and the plurality of second lead wires 9b. In an area where each thermistor film 5 faces the first substrate 2 in the thickness direction (an area where they overlap in plan view), a window W that transmits infrared light IR is provided between the first substrate 2 and thermistor film 5.

[0045] The first connection portion 10 has a pair of first connection members 11a, 11b provided corresponding to each of the multiple thermistor elements 4. Furthermore, the pair of first connection members 11a, 11b has a pair of arm portions 12a, 12b and a pair of leg portions 13a, 13b.

[0046] Each of the arm portions 12a, 12b is made of a folded linear conductor pattern formed by a thin film of, for example, titanium or titanium nitride along the periphery of the thermistor element 4. Each of the leg portions 13a, 13b is made of a conductor pillar with a circular cross section formed by plating with, for example, copper, gold, an FeCoNi alloy, or an NiFe alloy (permalloy) and extending in the third direction Z.

[0047] One of the first connection members 11a has one arm portion 12a electrically connected to one of the second electrodes 6b and one leg portion 13a electrically connecting the one arm portion 12a and the first lead wiring 9a, and electrically connects the one second electrode 6b and the first lead wiring 9a.

[0048] The other first connecting member 11b has the other arm portion 12b electrically connected to the other second electrode 6b and the other leg portion 13b electrically connecting the other arm portion 12c and the second lead wiring 9b, and electrically connects the other second electrode 6b and the second lead wiring 9b.

[0049] As a result, the thermistor element 4 is supported in a suspended state in the third direction Z by a pair of first connecting members 11a, 11b positioned diagonally in the plane of the thermistor element 4. A space G is provided between the thermistor element 4 and the first insulator layer 8.

[0050] Although not shown, one surface of the first substrate 2 (the surface facing the second substrate 3) is provided with a plurality of selection transistors (not shown) for selecting one thermistor element 4 from the plurality of thermistor elements 4. The plurality of selection transistors are provided at positions corresponding to the plurality of thermistor elements 4 on the first substrate 2. Furthermore, each selection transistor is provided at a position that avoids the window portion W described above in order to prevent diffuse reflection of infrared rays IR and a decrease in incidence efficiency.

[0051] On the second substrate 3 side, there are provided a second insulator layer 14, a circuit section 15 that detects changes in the voltage output from the thermistor element 4 and converts it into brightness temperature, and a second connection section 16 that electrically connects each thermistor element 4 and the circuit section 15.

[0052] The second insulator layer 14 is made of an insulating film laminated on one surface (the surface facing the first substrate 2) of the second substrate 3. As the insulating film, the same insulating films as those exemplified for the first insulator layer 8 can be used.

[0053] The circuit section 15 is made up of a read out integrated circuit (ROIC), a regulator, an analog-to-digital converter (A / D converter), a multiplexer, etc., and is provided within the second insulating layer 14.

[0054] Furthermore, a plurality of connection terminals 17a, 17b corresponding to the plurality of first lead wires 9a and the plurality of second lead wires 9b are provided on the surface of the second insulator layer 14. The connection terminals 17a, 17b are made of a conductive film such as copper or gold.

[0055] One of the connection terminals 17a is located in an area on one side of the first direction X that surrounds the periphery of the circuit unit 15, and is arranged side by side at regular intervals in the second direction Y. The other of the connection terminals 17b is located in an area on one side of the second direction Y that surrounds the periphery of the circuit unit 15, and is arranged side by side at regular intervals in the first direction X.

[0056] The second connection portion 16 has a plurality of second connection members 18a, 18b provided corresponding to the plurality of first lead wires 9a and the plurality of second lead wires 9b, respectively. The plurality of second connection members 18a, 18b are made of conductor pillars with a circular cross section formed by plating with, for example, copper or gold, and extending in the third direction Z.

[0057] One second connection member 18a electrically connects one end of the first lead wire 9a to one connection terminal 17a. The other second connection member 18b electrically connects one end of the second lead wire 9b to the other connection terminal 17b. As a result, the multiple first lead wires 9a and the circuit unit 15 are electrically connected via one second connection member 18a and one connection terminal 17a. Also, the multiple second lead wires 9b and the circuit unit 15 are electrically connected via the other second connection member 18b and the other connection terminal 17b.

[0058] In the electromagnetic wave sensor 1 of this embodiment having the above-described configuration, infrared rays IR emitted from the object to be measured enter the thermistor element 4 through the window W from the first substrate 2 side.

[0059] In the thermistor element 4, infrared rays IR incident on a dielectric film 7 formed near the thermistor film 5 are absorbed by the dielectric film 7, and infrared rays IR incident on the thermistor film 5 are absorbed by the thermistor film 5, causing a change in the temperature of the thermistor film 5. In the thermistor element 4, the electrical resistance of the thermistor film 5 changes in response to a change in the temperature of the thermistor film 5, causing a change in the output voltage between the pair of second electrodes 6b. In the electromagnetic wave sensor 1 of this embodiment, the thermistor element 4 functions as a bolometer element.

[0060] In the electromagnetic wave sensor 1 of this embodiment, infrared rays IR emitted from the object to be measured are detected in a planar manner using multiple thermistor elements 4, and then the electrical signal (voltage signal) output from each thermistor element 4 is converted into a brightness temperature, thereby making it possible to detect (image) the temperature distribution (temperature image) of the object to be measured in two dimensions.

[0061] When a constant voltage is applied to the thermistor film 5 of the thermistor element 4, it is also possible to detect a change in the current flowing through the thermistor film 5 in response to a change in the temperature of the thermistor film 5 and convert this into a luminance temperature.

[0062] In the electromagnetic wave sensor 1 of this embodiment, even when a plurality of thermistor elements 4 are arranged in an array, it is possible to achieve further miniaturization.

[0063] The present invention is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the electromagnetic wave sensor to which the present invention is applied is not necessarily limited to the configuration of the infrared image sensor in which a plurality of thermistor elements 4 are arranged in an array as described above, and the present invention can also be applied to an electromagnetic wave sensor using a single thermistor element 4 or an electromagnetic wave sensor in which a plurality of thermistor elements 4 are arranged in a line. The thermistor element 4 can also be used as a temperature sensor for measuring temperature.

[0064] Furthermore, the electromagnetic wave sensor to which the present invention is applied is not necessarily limited to one that detects the above-mentioned infrared rays as electromagnetic waves, but may also be one that detects, for example, terahertz waves with a wavelength of 30 μm or more and 3 mm or less. [Example]

[0065] The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0066] In this example, the thermistor films of Examples 1 and 2 and Comparative Examples 1 and 2 shown in Table 1 below were prepared under the conditions shown in Tables 2 and 3 below, and their resistivities [Ω·cm] were measured.

[0067] [Table 1]

[0068] [Table 2]

[0069] [Table 3]

[0070] Example 1 In Example 1, first, a base film made of Pt (corresponding to the first electrode 6a of the thermistor element 4 shown in FIG. 2) was formed on a Si substrate with a thermal oxide film by DC sputtering under conditions of input power 300 W, deposition gas Ar, deposition pressure 0.05 Pa, and substrate temperature 25°C, as shown in Table 2. Next, a Co-Mn-Ni oxide film with a composition ratio of Co:Mn:Ni=44:43:13 was formed on this base film by DC sputtering under conditions of input power 300 W, deposition gas Ar, deposition pressure 0.02 Pa, and substrate temperature 25°C, as shown in Table 3. Then, a heat treatment was performed at a temperature of 250°C for 1 hour to form a thermistor film made of an oxide having a spinel crystal structure containing Co, Mn, and Ni.

[0071] The thermistor film of Example 1 has a spinel-type crystal structure, and measurement by θ-2θ scan using out-of-plane measurement of X-ray diffraction (hereinafter referred to as "θ-2θ scan using X-ray diffraction") revealed that it has a preferred orientation of <0111> in the film thickness direction, as shown in the graph in Figure 6. It was also found that the undercoat film made of Pt also has a preferred orientation of <0111> in the film thickness direction.

[0072] Furthermore, a thermistor element having a CPP structure was fabricated using the thermistor film of Example 1, and the resistivity was measured by passing a current perpendicular to the surface of the thermistor film. The resistivity of the thermistor film was found to be 307 Ω·cm.

[0073] (Comparative Example 1) In Comparative Example 1, first, an underlayer film made of SiO2 was formed on a Si substrate by RF sputtering under conditions of input power 900 W, deposition gas Ar, deposition pressure 0.9 Pa, and substrate temperature 25°C, as shown in Table 2. Next, a Co-Mn-Ni oxide film with a composition ratio of Co:Mn:Ni=44:43:13 was formed on this underlayer film by DC sputtering under conditions of input power 300 W, deposition gas Ar, deposition pressure 0.02 Pa, and substrate temperature 25°C, as shown in Table 3. After that, a heat treatment was performed at a temperature of 250°C for 1 hour to form a thermistor film made of an oxide having a spinel crystal structure containing Co, Mn, and Ni.

[0074] The thermistor film of Comparative Example 1 has a spinel crystal structure, and as a result of measurement by θ-2θ scanning using X-ray diffraction, it was found to be randomly oriented, as shown in the graph of FIG.

[0075] Furthermore, a thermistor element with a CIP structure (corresponding to the thermistor element 4 shown in FIG. 2 in which the first electrode 6a is replaced with an undercoat film made of SiO2) was fabricated using the thermistor film of Comparative Example 1. When a current was passed in the in-plane direction through the thermistor film to measure its resistivity, the resistivity of the thermistor film was found to be 531 Ω cm.

[0076] Example 2 In Example 2, first, a Pt base film (corresponding to the first electrode 6a of the thermistor element 4 shown in FIG. 2) was formed on a Si substrate with a thermal oxide film by DC sputtering under conditions of input power 300 W, deposition gas Ar, deposition pressure 0.05 Pa, and substrate temperature 25°C, as shown in Table 2. Next, a Co-Mn-Cu oxide film with a composition ratio of Co:Mn:Cu=44:42:14 was formed on this base film by DC sputtering under conditions of input power 300 W, deposition gas Ar, deposition pressure 0.02 Pa, and substrate temperature 25°C, as shown in Table 3. Then, a heat treatment was performed at 250°C for 1 hour to form a thermistor film made of an oxide having a spinel crystal structure containing Co, Mn, and Cu.

[0077] The thermistor film of Example 2 has a spinel-type crystal structure, and measurement by θ-2θ scanning using X-ray diffraction revealed that it has a preferred orientation of <0111> in the film thickness direction, as shown in the graph in Figure 8. It was also found that the undercoat film made of Pt also has a preferred orientation of <0111> in the film thickness direction.

[0078] Furthermore, a thermistor element having a CPP structure was fabricated using the thermistor film of Example 2, and the resistivity was measured by passing a current perpendicular to the surface of the thermistor film. The resistivity of the thermistor film was found to be 67 Ω·cm.

[0079] (Comparative Example 2) In Comparative Example 2, first, an underlayer film made of SiO2 was formed on a Si substrate by RF sputtering under conditions of input power 900 W, deposition gas Ar, deposition pressure 0.9 Pa, and substrate temperature 25°C, as shown in Table 2. Next, a Co-Mn-Cu oxide film with a composition ratio of Co:Mn:Cu=44:42:14 was formed on this underlayer film by DC sputtering under conditions of input power 300 W, deposition gas Ar, deposition pressure 0.02 Pa, and substrate temperature 25°C, as shown in Table 3. After that, a heat treatment was performed at a temperature of 250°C for 1 hour to form a thermistor film made of an oxide having a spinel crystal structure containing Co, Mn, and Cu.

[0080] The thermistor film of Comparative Example 2 had a spinel crystal structure, and measurement by θ-2θ scanning using X-ray diffraction revealed that it was randomly oriented, as shown in the graph of FIG.

[0081] Furthermore, a thermistor element with a CIP structure (corresponding to the thermistor element 4 shown in FIG. 2 in which the first electrode 6a is replaced with an undercoat film made of SiO2) was fabricated using the thermistor film of Comparative Example 2. When a current was passed in the in-plane direction through the thermistor film to measure its resistivity, the resistivity of the thermistor film was found to be 185 Ω cm.

[0082] As described above, in Example 1, it is possible to reduce the resistivity of the thermistor film more than in Comparative Example 1. That is, the resistivity in the direction of the

[0111] preferred orientation is smaller than the resistivity in the case of random orientation.

[0083] Furthermore, in Example 2, it is possible to reduce the resistivity of the thermistor film more than in Comparative Example 2. That is, the resistivity in the direction of the

[0111] preferred orientation is smaller than the resistivity in the case of random orientation.

[0084] In this way, since the thermistor film is made of an oxide having a spinel crystal structure and has a preferred orientation of

[0111] in the film thickness direction, it is possible to reduce the resistance value of the thermistor film between the first electrode and the second electrode that sandwich the thermistor film in the film thickness direction. [Explanation of symbols]

[0085] REFERENCE SIGNS LIST 1...electromagnetic wave sensor 2...first substrate 3...second substrate 4...thermistor element 5...thermistor film 6a...first electrode 6b...second electrode 7...dielectric film 8...first insulator layer 9...wiring portion 9a...first lead wiring 9b...second lead wiring 10...first connection portion 11a, 11a...first connection member 12a, 12b...arm portion 13a, 13b...leg portion 14...second insulator layer 15...circuit portion 16...second connection portion 17a, 17b...connection terminal 18a, 18b...second connection member IR...infrared (electromagnetic wave) G...space K...internal space

Claims

1. a thermistor film; a first electrode provided in contact with one surface of the thermistor film; a pair of second electrodes provided in contact with the other surface of the thermistor film, the thermistor film is made of an oxide having a spinel crystal structure and is preferentially oriented in the [111] direction in the film thickness direction; The thermistor element characterized in that the above-mentioned "preferentially oriented in the [111] direction in the film thickness direction" means a state in which, in a θ-2θ scan by out-of-plane measurement of X-ray diffraction, the diffraction peak intensity from the (111) plane of the spinel crystal structure is greater than the diffraction peak intensity from other crystal planes, or a state in which, in a θ-2θ scan by out-of-plane measurement of X-ray diffraction, only the diffraction peak from the (111) plane of the spinel crystal structure is observed.

2. An electromagnetic wave sensor comprising the thermistor element according to claim 1.

3. 3. The electromagnetic wave sensor according to claim 2, wherein a plurality of the thermistor elements are arranged in an array.

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