JP2017216380A - Ferroelectric element, thermoelectric converter, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric element containing a small amount of lead and low in noise.SOLUTION: A ferroelectric element 1 includes: a first electrode 3 and a second electrode 6; a first ferroelectric layer 4 provided between the first electrode 3 and the second electrode 6 and having a perovskite structure; and a second ferroelectric layer 5 provided between the first ferroelectric layer 4 and the second electrode 6 and having a perovskite structure. The first ferroelectric layer 4 has a thinner thickness and a higher electrical resistance than the second ferroelectric layer 5, and the second ferroelectric layer 5 contains no lead.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ferroelectric element, a thermoelectric conversion device, and an electronic apparatus.

  A pyroelectric material is known that exhibits a pyroelectric effect that changes its surface charge by polarization due to temperature change. The pyroelectric material is used as a heat detection element of a thermal photodetector. The thermal detector includes a light absorption layer and a heat detection element. The light absorbing layer absorbs light emitted from the object and converts the light into heat. Then, the heat detection element measures a change in temperature. The pyroelectric material is composed of a ferroelectric material. An element in which a ferroelectric is sandwiched between electrodes is also referred to as a ferroelectric element.

  As a material constituting the pyroelectric material, lead zirconate titanate has been used. Since this material contains lead as a constituent element, it is not preferable from the viewpoint of environmental problems. A pyroelectric material that does not use lead is disclosed in Patent Document 1. According to it, the pyroelectric material contains an oxide containing iron, manganese, bismuth and gadolinium.

JP2013-134081A

  A pyroelectric material containing no lead has a large leakage current. Further, noise is increased in the ferroelectric element having a large leakage current. Therefore, a ferroelectric element with a small amount of lead and low noise has been desired.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms or application examples.

[Application Example 1]
A ferroelectric element according to this application example, wherein the first electrode and the second electrode, the first ferroelectric layer having a perovskite structure disposed between the first electrode and the second electrode, A second ferroelectric layer disposed between the first ferroelectric layer and the second electrode and having a perovskite structure, wherein the first ferroelectric layer has an electrical resistance higher than that of the second ferroelectric layer. And the second ferroelectric layer does not contain lead.

  According to this application example, the ferroelectric element is arranged in the order of the first electrode, the first ferroelectric layer, the second ferroelectric layer, and the second electrode. The first ferroelectric layer and the second ferroelectric layer are ferroelectric layers having a perovskite structure. Therefore, when the temperature of the ferroelectric element changes, the ferroelectric element functions as a pyroelectric body whose polarization changes and the surface charge changes.

  The second ferroelectric layer does not contain lead. Therefore, even if the first ferroelectric layer contains lead, the second ferroelectric layer does not contain lead, so that both the first ferroelectric layer and the second ferroelectric layer contain lead. Lead content can be reduced.

  The first ferroelectric layer has a higher electrical resistance than the second ferroelectric layer. The first ferroelectric layer and the second ferroelectric layer are connected in series. Therefore, the electrical resistance can be increased as compared with the case where the second ferroelectric layer is used alone. And the leak current flowing between the first electrode and the second electrode can be reduced by increasing the electric resistance. Since the Johnson noise of the ferroelectric element is reduced by reducing the leakage current, the noise of the ferroelectric element can be reduced.

[Application Example 2]
In the ferroelectric element according to the application example, the first ferroelectric layer includes lead, zirconium, and titanium, and the second ferroelectric layer includes bismuth, lanthanum, and iron.

  According to this application example, the first ferroelectric layer includes lead, zirconium, and titanium, and the second ferroelectric layer includes bismuth, lanthanum, and iron. At this time, the first ferroelectric layer and the second ferroelectric layer can have a perovskite structure. Therefore, the ferroelectric element has a function as a pyroelectric material. The second ferroelectric layer is a dielectric layer not containing lead. The first ferroelectric layer can have a higher electrical resistance than the second ferroelectric layer. Therefore, the ferroelectric element described in Application Example 1 can be realized.

[Application Example 3]
In the ferroelectric element according to the application example, the first ferroelectric layer includes lead, zirconium, and titanium, and the second ferroelectric layer includes bismuth, gadolinium, and iron.

  According to this application example, the first ferroelectric layer includes lead, zirconium, and titanium, and the second ferroelectric layer includes bismuth, gadolinium, and iron. At this time, the first ferroelectric layer and the second ferroelectric layer can have a perovskite structure. Therefore, the ferroelectric element has a function as a pyroelectric material. The second ferroelectric layer is a dielectric layer not containing lead. The first ferroelectric layer can have a higher electrical resistance than the second ferroelectric layer. Therefore, the ferroelectric element described in Application Example 1 can be realized. Furthermore, since the sensitivity near normal temperature is good, it can be used at normal temperature.

[Application Example 4]
In the ferroelectric element according to the application example described above, the second ferroelectric layer includes manganese.

  According to this application example, the second ferroelectric layer contains bismuth, lanthanum, iron, and manganese. At this time, the second ferroelectric layer can reduce the leakage resistance as compared with the case where manganese is not included. Therefore, the noise of the ferroelectric element can be reduced.

[Application Example 5]
In the ferroelectric element according to the application example described above, the second ferroelectric layer is oriented in (111).

  According to this application example, the second ferroelectric layer is oriented in (111). At this time, since the amount of polarization of the second ferroelectric layer increases, the ferroelectric element can be made a sensitive element.

[Application Example 6]
In the ferroelectric element according to the application example described above, the first ferroelectric layer is thinner than the second ferroelectric layer.

  According to this application example, the first ferroelectric layer is thinner than the second ferroelectric layer. Since the second ferroelectric layer does not contain lead, the lead content can be suppressed by increasing the thickness of the layer not containing lead.

[Application Example 7]
A thermoelectric conversion device according to this application example is characterized in that the ferroelectric elements described above are two-dimensionally arranged.

  According to this application example, the thermoelectric conversion device has ferroelectric elements arranged two-dimensionally. Ferroelectric elements convert heat into electrical signals. Since the ferroelectric elements are two-dimensionally arranged, the thermoelectric converter can detect the heat distribution. The thermoelectric conversion device includes the ferroelectric element described above. The ferroelectric element described above is an element with low lead content and low noise. Therefore, the thermoelectric conversion device of this application example can be a thermoelectric conversion device including a ferroelectric element with low lead content and low noise.

[Application Example 8]
An electronic device according to this application example is an electronic device including a light detection unit that detects infrared rays, and includes the thermoelectric conversion device described above in the light detection unit.

  According to this application example, the electronic device includes the light detection unit that detects infrared rays. The light detection unit includes a thermoelectric conversion device in which ferroelectric elements are two-dimensionally arranged. Since the place irradiated with infrared rays is heated, the temperature rises. The thermoelectric conversion device detects the temperature distribution. Therefore, the electronic device can detect the distribution of the infrared light source via the infrared light. The thermoelectric conversion device includes the ferroelectric element described above. The ferroelectric element described above is an element with low lead content and low noise. Therefore, the electronic device of this application example can be an electronic device including a ferroelectric element with a low lead content and low noise.

[Application Example 9]
An electronic apparatus according to this application example includes the ferroelectric element described above.

  According to this application example, the electronic device includes the ferroelectric element described above. The ferroelectric element described above is an element with low lead content and low noise. Therefore, the electronic device of this application example can be an electronic device including a ferroelectric element with a low lead content and low noise.

1 is a schematic side cross-sectional view showing a structure of a ferroelectric element according to a first embodiment. The figure for demonstrating the leak resistance of a 1st ferroelectric layer and a 2nd ferroelectric layer. The figure for demonstrating the leakage current of a ferroelectric element. FIG. 6 is a schematic side cross-sectional view showing the structure of a ferroelectric element according to a second embodiment. FIG. 6 is a schematic side cross-sectional view showing the structure of a ferroelectric element according to a third embodiment. The schematic plan view which shows the structure of the sensor array in connection with 4th Embodiment. The schematic side sectional view which shows the structure of a sensor array. The block diagram which shows the structure of the sensor device in connection with 5th Embodiment. The schematic diagram for demonstrating the arrangement | sequence of a ferroelectric element. The block diagram which shows the structure of the infrared camera in connection with 6th Embodiment. The block diagram which shows the structure of the driving assistance device in connection with 7th Embodiment. The schematic perspective view which shows the motor vehicle carrying a driving assistance device. The block diagram which shows the structure of the security apparatus concerning 8th Embodiment. The schematic diagram which shows the house in which the security apparatus was installed. The block diagram which shows the structure of the controller of the game device concerning 9th Embodiment. The schematic diagram for demonstrating the usage method of a controller. The block diagram which shows the structure of the body temperature measuring apparatus concerning 10th Embodiment. The block diagram which shows the structure of the specific substance detection apparatus concerning 11th Embodiment. The schematic perspective view which shows the structure of the ultrasonic image diagnostic apparatus concerning 12th Embodiment. The schematic perspective view which shows the structure of an ultrasonic sensor. The schematic side sectional view which shows the structure of an ultrasonic element.

  Hereinafter, embodiments will be described with reference to the drawings. In addition, each member in each drawing is illustrated with a different scale for each member in order to make the size recognizable on each drawing.

(First embodiment)
In this embodiment, a characteristic example of a ferroelectric element will be described with reference to the drawings. The ferroelectric element according to the first embodiment will be described with reference to FIGS. FIG. 1 is a schematic sectional side view showing the structure of a ferroelectric element. As shown in FIG. 1, the ferroelectric element 1 is installed on a substrate 2. The ferroelectric element 1 includes a first electrode 3, a first ferroelectric layer 4, a second ferroelectric layer 5, and a second electrode 6.

  The first electrode 3, the first ferroelectric layer 4, the second ferroelectric layer 5, and the second electrode 6 are disposed in this order. The first ferroelectric layer 4 is disposed between the first electrode 3 and the second electrode 6 and has a perovskite structure. The second ferroelectric layer 5 is disposed between the first ferroelectric layer 4 and the second electrode 6 and has a perovskite structure. The first ferroelectric layer 4 is thinner than the second ferroelectric layer 5.

  The perovskite structure has a cubic unit cell. Each vertex of the cubic crystal, metal, body center and metal are installed. Oxygen is arranged in each face center of the cubic crystal centering on the metal of the body center. It is in the form of an octahedron made of oxygen and body metal. The orientation of the octahedron is easily distorted due to the interaction with the metal at each vertex. When strained, the phase transitions from cubic to orthorhombic or tetragonal with low symmetry. At this time, the valence electron distribution state of the perovskite structure and the interaction between the valence electron spins change. The perovskite structure changes between a ferroelectric material and an antiferroelectric material. At this time, the amount of polarization of the perovskite structure changes and functions as a pyroelectric body.

  The material of the first ferroelectric layer 4 contains lead, zirconium, and titanium, and is called PZT. The material of the second ferroelectric layer 5 includes bismuth, lanthanum, and iron, and does not include lead. Since the first ferroelectric layer 4 contains lead, zirconium, and titanium, it can have a perovskite structure. Similarly, since the second ferroelectric layer 5 contains bismuth, lanthanum, and iron, it can have a perovskite structure. The first ferroelectric layer 4 and the second ferroelectric layer 5 function as pyroelectric bodies that exhibit a pyroelectric effect in which the phase transition occurs near room temperature and the polarization amount changes rapidly. Therefore, when the temperature of the ferroelectric element 1 changes, the ferroelectric element 1 functions as a pyroelectric body whose polarization changes and the surface charge changes.

  The second ferroelectric layer 5 is oriented in (111). At this time, since the second ferroelectric layer 5 has a large amount of polarization, the ferroelectric element 1 can be made a highly sensitive element.

  An insulating film 7 is provided to cover the first electrode 3, the first ferroelectric layer 4, the second ferroelectric layer 5, and the second electrode 6. A portion of the insulating film 7 covering the first electrode 3 is opened and the first wiring 8 is provided. The first wiring 8 is connected to the first electrode 3. Similarly, a part of the insulating film 7 covering the second electrode 6 is opened and the second wiring 9 is provided. The second wiring 9 is connected to the second electrode 6. When the amount of polarization of the first ferroelectric layer 4 and the second ferroelectric layer 5 increases, a voltage higher than that of the second wiring 9 is detected in the first wiring 8.

  When the ferroelectric element 1 is used for an infrared light sensor, the first wiring 8 and the second wiring 9 are preferably made of a material that transmits infrared light. Further, the material of the first wiring 8 and the second wiring 9 is preferably a conductive and heat-resistant material, and is not particularly limited. The materials of the first wiring 8 and the second wiring 9 are ITO (Indium Tin Oxide), IZO (Indium-zinc oxide), ZnO (Zinc oxide), IGZO (Indium-gallium-zinc oxide), SnOx (tin oxide), IGO (Indium-gallium oxide), ICO (Indium-cerium oxide), or the like can be used. In the present embodiment, for example, ITO films are used for the first wiring 8 and the second wiring 9. Since the ITO film has heat resistance, the first wiring 8 and the second wiring 9 can be prevented from being damaged by heat.

  FIG. 2 is a diagram for explaining the leakage resistance between the first ferroelectric layer and the second ferroelectric layer. In FIG. 2, the vertical axis indicates leakage resistance, and the upper side indicates higher resistance than the lower side. The scale on the vertical axis is a logarithmic scale. The horizontal axis shows the first ferroelectric layer 4 and the second ferroelectric layer 5. The second ferroelectric layer 5 contains manganese and titanium in addition to bismuth, lanthanum, and iron. The second ferroelectric layer 5 is said to be BLFMT because of the material it contains.

The leak resistance of the first ferroelectric layer 4 is about 6E ¹¹ Ω, and the leak resistance of the second ferroelectric layer 5 is about 7E ⁸ Ω. Accordingly, the leakage resistance of the first ferroelectric layer 4 is about 1E ³ times larger than the leakage resistance of the second ferroelectric layer 5.

The noise due to the leak current is greatly contributed by the Johnson noise In of the ferroelectric element 1. Johnson noise In refers to noise caused by irregular thermal oscillation or Brownian motion of free electrons in the resistor. Johnson noise is also called thermal noise. Johnson noise In is expressed by the following equation using leakage resistance R, element capacitance C, Boltzmann coefficient K _B , and temperature T.
In = {(2K _B × T / C) ^1/2 } / R (Formula 1)
As shown in (Expression 1), the Johnson noise In is inversely proportional to the leak resistance R. Since the first ferroelectric layer 4 has a larger leakage resistance R than the second ferroelectric layer 5, Johnson noise In can be reduced. Note that the leak resistance R of the ferroelectric layer is also referred to as electric resistance.

  The first ferroelectric layer 4 has a higher electrical resistance than the second ferroelectric layer 5. The first ferroelectric layer 4 and the second ferroelectric layer 5 are connected in series. Accordingly, the electrical resistance can be increased as compared with the case where the second ferroelectric layer 5 alone is used. And the leak current which flows between the 1st electrode 3 and the 2nd electrode 6 can be made small by making electrical resistance high. Since the Johnson noise of the ferroelectric element 1 is reduced by reducing the leakage current, the noise of the ferroelectric element 1 can be reduced.

  The second ferroelectric layer 5 and the electrode are in ohmic contact, and when a voltage is applied, a current flows in proportion thereto. The first ferroelectric layer 4 and the electrode are in a Schottky contact and have a characteristic that current does not easily flow up to a certain voltage. When the first ferroelectric layer 4 is not included in the ferroelectric element 1, the second ferroelectric layer 5 and the first electrode 3 are in ohmic contact. By sandwiching the first ferroelectric layer 4 between the second ferroelectric layer 5 and the first electrode 3, the first ferroelectric layer 4 and the first electrode 3 are brought into Schottky contact. Leakage current can be reduced by changing the ohmic contact to a Schottky contact.

  FIG. 3 is a diagram for explaining the leakage current of the ferroelectric element. The horizontal axis of FIG. 3 shows the voltage applied between the first electrode 3 and the second electrode 6, and the right side in the figure is higher than the left side. The vertical axis indicates the leakage current flowing between the first electrode 3 and the second electrode 6, and the upper side in the figure is larger than the lower side.

  The first characteristic line 10 is a line indicating the current-voltage characteristic when only the second ferroelectric layer 5 is provided between the first electrode 3 and the second electrode 6. The second characteristic line 11 is a line indicating the current-voltage characteristic when only the first ferroelectric layer 4 is disposed between the first electrode 3 and the second electrode 6. The third characteristic line 12 is a line indicating the current-voltage characteristic of the ferroelectric element 1 in which the first ferroelectric layer 4 and the second ferroelectric layer 5 are disposed between the first electrode 3 and the second electrode 6. is there.

  The third characteristic line 12 has a characteristic between the first characteristic line 10 and the second characteristic line 11. The third characteristic line 12 can reduce the leakage current by about one digit in a wider voltage range than the first characteristic line 10. Accordingly, by arranging the second ferroelectric layer 5 so as to overlap the first ferroelectric layer 4, Johnson noise is reduced as compared with the case where only the second ferroelectric layer 5 is provided, and the noise of the ferroelectric element 1. Can be reduced.

  The second ferroelectric layer 5 contains manganese in addition to bismuth, lanthanum, and iron. At this time, the second ferroelectric layer 5 can reduce the leakage resistance as compared with the case where manganese is not included. Therefore, Johnson noise of the ferroelectric element 1 can be reduced.

  The first ferroelectric layer 4 is thinner than the second ferroelectric layer 5, and the second ferroelectric layer 5 does not contain lead. Therefore, even if the first ferroelectric layer 4 contains lead, the second ferroelectric layer 5 does not contain lead. Therefore, both the first ferroelectric layer 4 and the second ferroelectric layer 5 contain lead. The lead content can be reduced compared to sometimes.

  Next, a method for forming the first ferroelectric layer 4 and the second ferroelectric layer 5 will be described. First, the first electrode 3 is installed on the substrate 2. The first electrode 3 is formed by depositing iridium, iridium oxide, and platinum in this order. As a film forming method, a CVD method, a sputtering method, or the like can be used. Next, the first electrode 3 is patterned. As the patterning method, a known photolithography method and an etching method can be used in combination. Detailed description is omitted. Either the sputtering method or the sol-gel method can be used to form the first ferroelectric layer 4 and the second ferroelectric layer 5.

  In the sputtering method, a PZT sintered body having a specific component is used as a sputtering target, and an amorphous first piezoelectric film precursor film is formed on the first electrode 3 by sputtering. Next, an amorphous second piezoelectric film precursor film is formed on the first piezoelectric film precursor film by sputtering using a BLFMT sintered body of a specific component as a sputtering target.

  Next, the amorphous first piezoelectric film precursor film and the second piezoelectric film precursor film are heated, crystallized and sintered. This heating is performed in an oxygen atmosphere such as oxygen or a mixed gas of oxygen and an inert gas such as argon. In the heating step, the first piezoelectric film precursor film and the second piezoelectric film precursor film are heated at a temperature of 500 to 700 ° C. in an oxygen atmosphere. The first piezoelectric film precursor film and the second piezoelectric film precursor film are crystallized by heating.

  In the sol-gel method, a sol that is a hydrated complex of a hydroxide of titanium, zirconium, lead, or the like, which is a material of the first ferroelectric layer 4 is prepared. This sol is dehydrated to obtain a gel. The gel is heated and fired to prepare a first pyroelectric material layer that is an inorganic oxide. Starting from titanium, zirconium, lead, and further alkoxides or acetates of other metal components. This starting material is the first sol. This first sol is used as a composition mixed with an organic polymer compound. This organic polymer compound absorbs the residual stress of the first pyroelectric material layer during drying and firing, and reduces the risk of cracking in the first pyroelectric material layer.

  Next, the first sol composition is applied onto the first electrode 3. Various coating methods and printing methods are used as the coating method. After coating, the sol composition film is dried. Drying is performed by natural drying or by heating to a temperature of 80 ° C. or higher and 200 ° C. or lower. Next, the film of the first sol composition is fired. The firing temperature is in the range of 300 to 450 ° C. for about 10 to 120 minutes. The film of the first sol composition is gelled by firing.

  Next, re-firing is performed at different temperatures. The firing temperature is in the range of 400 to 800 ° C. for about 0.1 to 5 hours. In the refiring, the first stage of the temperature in the range of 400 to 600 ° C. is performed. Next, a 2nd step is performed at the temperature of the range of 600-800 degrees C or less. Thereby, the porous gel thin film is converted into a film made of a crystalline metal oxide. When this film is formed into a laminated film, the steps from application of the starting material to baking are repeated. Although the number of repetitions is not particularly limited, for example, in this embodiment, the process from the starting material coating to baking is repeated twice. Then pre-anneal. In this way, the first ferroelectric layer 4 is formed.

  Next, the second ferroelectric layer 5 is disposed on the first ferroelectric layer 4. A fatty acid metal salt is used for each of iron, manganese, bismuth, lanthanum, and titanium. Examples of the fatty acid constituting the fatty acid metal salt include formic acid, acetic acid, propionic acid, butyric acid, herbic acid, caproic acid, enanthic acid, and caprylic acid, with acetic acid being particularly preferred.

  Thereby, the solubility with respect to the organic solvent of a fatty-acid metal salt, the ease of the chemical reaction to the said oxide, etc. can be made suitable. In addition, when using a fatty acid metal salt about multiple types of metal elements, the same fatty acid may be used about each metal element, and a different fatty acid may be used. Moreover, about the fatty-acid metal salt of arbitrary metal elements, a single fatty acid may be used and you may use in combination of multiple types of fatty acid.

  Examples of the organic solvent for dissolving the fatty acid metal salt include fatty acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol (Poly) alkylene glycol monoalkyl ethers such as monomethyl ether and propylene glycol monoethyl ether; fatty acid esters such as ethyl acetate, n-propyl acetate, iso-propyl acetate, n-butyl acetate and iso-butyl acetate; benzene, Aromatic hydrocarbons such as toluene and xylene; ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, ethyl n-butyl ketone, diisopropyl ketone, and acetyl acetone; ethanol, propanol, Nord, ethylene glycol, alcohols such as glycerin and the like, may be used in combination of one or more kinds selected from these, it is preferable to use a fatty acid.

  In general, the fatty acid is particularly excellent in solubility of the fatty acid metal salt and has an appropriate viscosity. For this reason, fatty acids not only facilitate the handling of solvents and solutions, but can also more effectively prevent the occurrence of unintentional compositional variations at each site of the pyroelectric material produced. Moreover, since a fatty acid generally has a moderately high boiling point, a chemical reaction to the oxide by heating can be suitably advanced.

  Especially, as a fatty acid as an organic solvent which melt | dissolves a fatty acid metal salt, propionic acid is preferable. Thereby, the solubility with respect to the organic solvent of a fatty-acid metal salt, the ease of the chemical reaction to the said oxide, etc. can be made suitable. In addition, a chemical reaction can be performed at a relatively high temperature using a simple instrument or apparatus, and removal of the solvent after the chemical reaction is easy. As described above, the productivity of the pyroelectric material can be made particularly excellent, and it is possible to more reliably prevent the solvent from remaining unintentionally in the obtained pyroelectric material.

  Although the heating temperature (reaction temperature) of the solution which melt | dissolved the fatty acid metal salt in the organic solvent is not specifically limited, It is preferable that it is 90 to 250 degreeC, and it is more preferable that it is 100 to 200 degreeC. As a result, the second ferroelectric layer 5 having the target composition can be manufactured with higher productivity while preventing unintentional compositional variation in the obtained second ferroelectric layer 5. Similar to the process of manufacturing the first ferroelectric layer 4, when the film of the second ferroelectric layer 5 is formed as a laminated film, the processes from application of the starting material to firing are repeated. Although the number of repetitions is not particularly limited, for example, in this embodiment, the process from application of the starting material to baking is repeated 8 times. Then pre-anneal. In this way, the second ferroelectric layer 5 is formed.

  Subsequently, the second electrode 6 is disposed on the second ferroelectric layer 5. The second electrode 6 is formed of iridium oxide, platinum, iridium oxide, and iridium in this order. The same film formation method as that of the first electrode 3 can be used. Next, the first ferroelectric layer 4, the second ferroelectric layer 5, and the second electrode 6 are formed in a predetermined shape. As a method for forming the first ferroelectric layer 4 and the second ferroelectric layer 5, a known photolithography method and an etching method can be used in combination. Detailed description is omitted.

  Subsequently, an insulating film 7 is provided on the first ferroelectric layer 4 and the second ferroelectric layer 5. The insulating film 7 is a film in which an aluminum oxide film and silicon dioxide are laminated. The aluminum oxide film and silicon dioxide are formed by a CVD (Chemical Vapor Deposition) method. The silicon dioxide film is formed using, for example, TEOS (tetraethyl orthosilicate). Then, patterning is performed by combining a known photolithography method and an etching method. In patterning the insulating film 7, an opening is provided at a location facing the first electrode 3 and a location facing the second electrode 6.

  Next, the first wiring 8 and the second wiring 9 are installed. The first wiring 8 and the second wiring 9 are formed by patterning the ITO film layer. The ITO film is installed using a sputtering method, and is formed, for example, by causing argon ions to collide with an ITO target. The ITO film is patterned. At this time, the first wiring 8 and the second wiring 9 can be patterned using a known photolithography method and dry etching method. The ferroelectric element 1 is manufactured by the above process.

As described above, this embodiment has the following effects.
(1) According to this embodiment, the ferroelectric element 1 is arranged in the order of the first electrode 3, the first ferroelectric layer 4, the second ferroelectric layer 5, and the second electrode 6. The first ferroelectric layer 4 and the second ferroelectric layer 5 are ferroelectric layers having a perovskite structure. Therefore, when the temperature of the ferroelectric element 1 changes, the ferroelectric element 1 functions as a pyroelectric body whose polarization changes and the surface charge changes.

  The first ferroelectric layer 4 is thinner than the second ferroelectric layer 5, and the second ferroelectric layer 5 does not contain lead. Therefore, even if the first ferroelectric layer 4 contains lead, the second ferroelectric layer 5 does not contain lead. Therefore, both the first ferroelectric layer 4 and the second ferroelectric layer 5 contain lead. The lead content can be reduced compared to sometimes.

  The first ferroelectric layer 4 has a higher electrical resistance than the second ferroelectric layer 5. The first ferroelectric layer 4 and the second ferroelectric layer 5 are connected in series. Accordingly, the electrical resistance can be increased as compared with the case where the second ferroelectric layer 5 alone is used. And the leak current which flows between the 1st electrode 3 and the 2nd electrode 6 can be made small by making electrical resistance high. Since the Johnson noise of the ferroelectric element 1 is reduced by reducing the leakage current, the noise of the ferroelectric element 1 can be reduced.

  (2) According to this embodiment, the first ferroelectric layer 4 contains lead, zirconium, and titanium, and the second ferroelectric layer 5 contains bismuth, lanthanum, and iron. At this time, the first ferroelectric layer 4 and the second ferroelectric layer 5 can have a perovskite structure. Therefore, the ferroelectric element 1 has a function as a pyroelectric material. The second ferroelectric layer 5 is a dielectric layer not containing lead. The first ferroelectric layer 4 can have a higher electrical resistance than the second ferroelectric layer 5.

  (3) According to this embodiment, the second ferroelectric layer 5 contains bismuth, lanthanum, iron, and manganese. At this time, the second ferroelectric layer 5 can reduce the leakage resistance as compared with the case where manganese is not included. Therefore, the noise of the ferroelectric element 1 can be reduced.

  (4) According to this embodiment, the second ferroelectric layer 5 is oriented in (111). At this time, since the second ferroelectric layer 5 has a large amount of polarization, the ferroelectric element 1 can be made a highly sensitive element.

  (5) According to this embodiment, the first ferroelectric layer 4 is thinner than the second ferroelectric layer 5. Since the second ferroelectric layer 5 does not contain lead, the lead content can be suppressed by increasing the thickness of the layer not containing lead.

(Second Embodiment)
Next, an embodiment of the ferroelectric element will be described with reference to the schematic side sectional view showing the structure of the ferroelectric element shown in FIG. This embodiment is different from the first embodiment in that the compositions of the first ferroelectric layer 4 and the second ferroelectric layer 5 are different. Note that description of the same points as in the first embodiment is omitted.

  As shown in FIG. 4, the ferroelectric element 15 is installed on the substrate 2. The ferroelectric element 15 includes a first electrode 3, a first ferroelectric layer 16, a second ferroelectric layer 17, and a second electrode 6. A first ferroelectric layer 16, a second ferroelectric layer 17, and a second electrode 6 are laminated on the first electrode 3 in this order. The first ferroelectric layer 16 contains lead, zirconium, and titanium. The second ferroelectric layer 17 contains bismuth, gadolinium, and iron.

  The first ferroelectric layer 16 contains lead, zirconium, and titanium, and the second ferroelectric layer 17 contains bismuth, gadolinium, and iron. At this time, the first ferroelectric layer 16 and the second ferroelectric layer 17 can have a perovskite structure. Therefore, the ferroelectric element 15 has a function as a pyroelectric material. The second ferroelectric layer 17 is a dielectric layer not containing lead. The first ferroelectric layer 16 can have a higher electrical resistance than the second ferroelectric layer 17. Therefore, the ferroelectric element 15 can reduce the lead content. Further, the ferroelectric element 15 can realize an element with less noise. Furthermore, the ferroelectric element 15 can be used at room temperature because of its high sensitivity near room temperature.

  The first ferroelectric layer 16 is thinner than the second ferroelectric layer 17, and the second ferroelectric layer 17 does not contain lead. Therefore, even if the first ferroelectric layer 16 contains lead, the second ferroelectric layer 17 does not contain lead. Therefore, both the first ferroelectric layer 16 and the second ferroelectric layer 17 contain lead. The lead content can be reduced compared to sometimes. Since the second ferroelectric layer 17 does not contain lead, the lead content can be suppressed by increasing the thickness of the layer not containing lead.

(Third embodiment)
Next, an embodiment of the ferroelectric element will be described with reference to the schematic side sectional view showing the structure of the ferroelectric element shown in FIG. This embodiment is different from the first embodiment in that the positions of the first ferroelectric layer 4 and the second ferroelectric layer 5 are different. Note that description of the same points as in the first embodiment is omitted.

  As shown in FIG. 5, the ferroelectric element 20 is installed on the substrate 2. In the ferroelectric element 20, a second ferroelectric layer 5, a first ferroelectric layer 4, and a second electrode 6 are laminated on the first electrode 3 in this order. Also in this embodiment, when the temperature of the ferroelectric element 20 changes, the ferroelectric element 20 functions as a pyroelectric body whose polarization changes and the surface charge changes. When the polarization of the ferroelectric element 20 increases, the voltage of the second wiring 9 becomes higher than that of the first wiring 8.

  Also in the ferroelectric element 20, the first ferroelectric layer 4 is thinner than the second ferroelectric layer 5, and the second ferroelectric layer 5 does not contain lead. Therefore, even if the first ferroelectric layer 4 contains lead, the second ferroelectric layer 5 does not contain lead. Therefore, both the first ferroelectric layer 4 and the second ferroelectric layer 5 contain lead. The lead content can be reduced compared to sometimes. Since the second ferroelectric layer 5 does not contain lead, the lead content can be suppressed by increasing the thickness of the layer not containing lead.

  The first ferroelectric layer 4 has a higher electrical resistance than the second ferroelectric layer 5. The first ferroelectric layer 4 and the second ferroelectric layer 5 are connected in series. Accordingly, the electrical resistance can be increased as compared with the case where the second ferroelectric layer 5 alone is used. And the leak current which flows between the 1st electrode 3 and the 2nd electrode 6 can be made small by making electrical resistance high. Since the Johnson noise of the ferroelectric element 20 is reduced by reducing the leakage current, the noise of the ferroelectric element 20 can be reduced.

(Fourth embodiment)
Next, an embodiment of the sensor array will be described with reference to FIGS. FIG. 6 is a schematic plan view showing the structure of the sensor array. FIG. 7 is a schematic side sectional view showing the structure of the sensor array. As shown in FIG. 6, ferroelectric elements 25 are two-dimensionally arranged in a matrix in a sensor array 24 as a thermoelectric conversion device. As the ferroelectric element 25, any one of the ferroelectric element 1, the ferroelectric element 15, and the ferroelectric element 20 described above is used.

  The sensor array 24 includes a substrate 26 having a rectangular planar shape. In the plane direction of the substrate 26, the longitudinal direction is defined as the Y direction, and the direction orthogonal to the Y direction is defined as the X direction. The thickness direction of the substrate 26 is taken as the Z direction. In the center of the substrate 26, a recess 26a similar to the outer shape of the substrate 26 is provided.

  A sensor element 27 that converts heat into an electrical signal is installed in the recess 26a. The sensor element 27 includes a light absorption film that absorbs light such as infrared rays and converts it into heat. When the sensor array 24 is irradiated with infrared light, the light absorption film generates heat in the sensor element 27 where the infrared light is irradiated. The sensor element 27 outputs an electrical signal corresponding to the light intensity of the infrared light.

  The number of sensor elements 27 is not particularly limited. In this embodiment, for example, 20 sensor elements 27 are arranged in the X direction and 240 sensors are arranged in the Y direction. The sensor element 27 includes a first support column 28 and a second support column 29 installed on the bottom surface of the recess 26a.

  A support substrate 30 is installed between the first support column 28 and the second support column 29. A first arm 31 is disposed between the support substrate 30 and the first support column 28, and a second arm 32 is disposed between the support substrate 30 and the second support column 29. The support substrate 30 is supported by the first support column 28, the second support column 29, the first arm 31, and the second arm 32. There is a space between the support substrate 30 and the bottom surface of the recess 26a.

  A ferroelectric element 25 is installed on the support substrate 30. A light absorbing film is provided so as to cover the ferroelectric element 25. The light absorption film is a film made of a resin containing an additive such as a dye that easily absorbs infrared light. When the light absorption film is irradiated with infrared light, the light absorption film generates heat. Then, the heat of the light absorption film is transmitted to the ferroelectric element 25.

  The heat of the ferroelectric element 25 travels through the first arm 31 and the first support column 28 and reaches the substrate 26. Further, the heat of the ferroelectric element 25 reaches the substrate 26 through the second arm 32 and the second support column 29. Since the first arm 31 and the second arm 32 are thin, it is difficult to transfer heat. When the ferroelectric element 25 is irradiated with infrared rays and the temperature of the ferroelectric element 25 increases, the amount of heat of the ferroelectric element 25 stagnates in the ferroelectric element 25. The ferroelectric element 25 responds to heat and outputs an electrical signal corresponding to the amount of heat.

As described above, this embodiment has the following effects.
(1) According to the present embodiment, the ferroelectric elements 25 are two-dimensionally arranged in the sensor array 24. The ferroelectric element 25 converts heat into an electrical signal. Since the ferroelectric elements 25 are two-dimensionally arranged, the ferroelectric elements 25 can detect the heat distribution. The ferroelectric element 25 includes any one of the ferroelectric element 1, the ferroelectric element 15, and the ferroelectric element 20 described above. The ferroelectric element 1, the ferroelectric element 15, and the ferroelectric element 20 described above are elements having a low lead content and a low noise. Therefore, the sensor array 24 of the present embodiment can be a sensor array 24 including the ferroelectric elements 25 with a low lead content and low noise.

(Fifth embodiment)
Next, an embodiment of a sensor device as an electronic apparatus including the sensor array will be described with reference to FIGS. In the present embodiment, the ferroelectric element is provided with a film that absorbs infrared rays and converts the infrared rays into heat, and the ferroelectric elements function as infrared detection elements. FIG. 8 is a block diagram showing the configuration of the sensor device, and FIG. 9 is a schematic diagram for explaining the arrangement of the ferroelectric elements. In this embodiment, an example of a sensor device equipped with a sensor array 24 will be described. The description of the same points as in the fourth embodiment will be omitted.

  That is, in the present embodiment, as shown in FIG. 8, the sensor device 35 as an electronic device includes a sensor array 36 as a light detection unit that detects infrared rays, a row selection circuit 37, and a readout circuit 38. Further, the sensor device 35 includes an A / D conversion unit 39 and a control circuit 40. The row selection circuit 37 and the readout circuit 38 are collectively referred to as a drive circuit. The row selection circuit 37 is also called a row driver. By using this sensor device, for example, an infrared camera used in a night vision device or the like can be realized.

  The sensor array 24 is used as the sensor array 36, and the ferroelectric elements 25 are two-dimensionally arranged in a matrix. As the ferroelectric element 25, any one of the ferroelectric element 1, the ferroelectric element 15, and the ferroelectric element 20 is used. In addition, wirings with a plurality of row lines and a plurality of column lines are provided. Row lines are also referred to as word lines and scanning lines, and column lines are also referred to as data lines. One of the row lines and the column lines may be one. For example, when there is one row line, a plurality of ferroelectric elements 25 are arranged in a direction along the row line (lateral direction in the figure). On the other hand, when there is one column line, a plurality of ferroelectric elements 25 are arranged in a direction along the column line (vertical direction in the figure).

  As shown in FIG. 9, each ferroelectric element 25 of the sensor array 36 is disposed at a location corresponding to the intersection position of each row line and each column line. For example, one of the ferroelectric elements 25 is arranged at a location corresponding to the intersection position of the row line WL1 and the column line DL1. The other ferroelectric elements 25 are similarly arranged.

  Returning to FIG. 8, the row selection circuit 37 is connected to one or more row lines. Then, each row line is selected. For example, taking a 320 × 240 pixel QVGA (Quarter Video Graphics Array) sensor array 36 as shown in FIG. 9 as an example, row lines WL0, WL1, WL2,... WL239 are sequentially selected and scanned. . That is, a word selection signal that is a signal for selecting these row lines is output to the sensor array 36.

  The read circuit 38 is connected to one or more column lines. Then, a read operation for each column line is performed. Taking the QVGA sensor array 36 as an example, an operation of reading detection signals (detection current, detection charge) from the column lines DL0, DL1, DL2,.

  The A / D converter 39 performs a process of A / D converting the detection voltage (measurement voltage) acquired by the readout circuit 38 into digital data. Then, the digital data DOUT after A / D conversion is output. Specifically, the A / D converter 39 is provided with each A / D converter corresponding to each of the plurality of column lines. Each A / D converter performs A / D conversion processing of the detected voltage acquired by the reading circuit 38 in the corresponding column line.

  The control circuit 40 generates various control signals and outputs them to the row selection circuit 37, the readout circuit 38, and the A / D conversion unit 39. For example, a charge or discharge (reset) control signal is generated and output. Alternatively, a signal for controlling the timing of each circuit is generated and output.

As described above, this embodiment has the following effects.
(1) According to this embodiment, the sensor device 35 includes the sensor array 36 that detects infrared rays. The sensor array 36 includes a sensor array 24 in which the ferroelectric elements 25 are two-dimensionally arranged. Since the place irradiated with infrared rays is heated, the temperature rises. The sensor array 24 detects the temperature distribution. Therefore, the sensor device 35 can detect the distribution of the infrared light source via the infrared light. The sensor array 36 includes the ferroelectric element 25 described above. The ferroelectric element 25 described above is an element having a low lead content and a low noise. Therefore, the sensor device 35 of the present embodiment can be an electronic device including the ferroelectric element 25 with low lead content and low noise.

(Sixth embodiment)
Next, an embodiment of an infrared camera, which is one of electronic devices including a ferroelectric element in a light detection unit that detects infrared light, will be described with reference to a block diagram showing the configuration of the infrared camera in FIG. As shown in FIG. 10, an infrared camera 41 as an electronic device includes an optical system 42, a light detection unit 43, an image processing unit 44, a processing unit 45, a storage unit 46, an operation unit 47, and a display unit 48. ing.

  The optical system 42 includes, for example, one or a plurality of lenses and a driving unit that drives the lenses. Then, an object image is formed on the light detection unit 43. If necessary, focus adjustment is also performed.

  The light detection unit 43 uses the sensor device 35 of the above embodiment. Therefore, the light detection unit 43 includes the ferroelectric element 25. The light detection unit 43 includes a row selection circuit (row driver) in addition to the two-dimensionally arranged ferroelectric elements 25, a readout circuit that reads data from the ferroelectric elements 25 via the column lines, and an A / D conversion unit. Etc. Then, the data from the respective ferroelectric elements 25 arranged two-dimensionally are sequentially read out to form subject image data.

  The image processing unit 44 performs various image processing such as image correction processing based on the digital image data from the light detection unit 43.

  The processing unit 45 controls the entire infrared camera 41 and controls each block in the infrared camera 41. The processing unit 45 is realized by a CPU or the like, for example. The storage unit 46 stores various types of information, and functions as a work area for the processing unit 45 and the image processing unit 44, for example. The operation unit 47 is an interface for an operator to operate the infrared camera 41, and is realized by various buttons, a GUI (Graphical User Interface) screen, and the like. The display unit 48 displays, for example, an image acquired by the light detection unit 43, a GUI screen, and the like, and is realized by various displays such as a liquid crystal display and an organic EL display.

  In this way, a heat (light) distribution image can be provided using the light detection unit 43 in which the ferroelectric elements 25 are two-dimensionally arranged in two orthogonal directions. By using the light detection unit 43, an electronic device such as a thermography, an in-vehicle night vision, or a surveillance camera can be configured.

  Of course, it is provided in an analysis device that analyzes physical information of an object, a measurement device that performs measurement, a security device that detects fire and heat generation, a factory, etc. by using the ferroelectric element 25 for one cell or multiple cells as a sensor. Various electronic devices such as FA (Factory Automation) devices can also be configured.

As described above, this embodiment has the following effects.
(1) According to this embodiment, the infrared camera 41 includes the light detection unit 43, and the ferroelectric element 25 is used for the light detection unit 43. As the ferroelectric element 25, the ferroelectric element 1, the ferroelectric element 15, or the ferroelectric element 20 described above is used. The ferroelectric element 25 of the light detection unit 43 is an element having a low lead content and low noise. Therefore, the infrared camera 41 can be an electronic device including the ferroelectric element 25 with a low lead content and low noise.

(Seventh embodiment)
Next, an embodiment of a driving support device that is one of electronic devices using an infrared camera provided with a ferroelectric element that detects infrared rays in a light detection unit will be described with reference to FIGS. 11 and 12. FIG. 11 is a block diagram showing the configuration of the driving support device, and FIG. 12 is a schematic perspective view showing an automobile equipped with the driving support device.

  As shown in FIG. 11, the driving support device 51 as an electronic device includes a processing unit 52 including a CPU that controls the driving support device 51, and an infrared camera 41 that can detect infrared rays in a predetermined imaging region outside the vehicle. And a yaw rate sensor 54 for detecting the yaw rate of the vehicle. Further, the driving support device 51 includes a vehicle speed sensor 55 that detects the traveling speed of the vehicle, a brake sensor 56 that detects the presence or absence of a brake operation by the driver, a speaker 57, and a display device 58. . And the same camera as the infrared camera 41 in the said embodiment is used for the infrared camera 41 of this embodiment. Therefore, the infrared camera 41 includes the ferroelectric element 25.

  For example, the processing unit 52 of the driving support device 51 is configured to display an infrared image around the host vehicle obtained by imaging by the infrared camera 41 and the traveling state of the host vehicle detected by the yaw rate sensor 54, the vehicle speed sensor 55, and the brake sensor 56. Such a detection signal is used. Then, the processing unit 52 detects an object such as an object and a pedestrian existing in front of the traveling direction of the host vehicle using the infrared image and the detection signal. When it is determined that there is a possibility of contact between the detected object and the host vehicle, an alarm is output from the speaker 57 or the display device 58.

  As shown in FIG. 12, the infrared camera 41 is disposed near the center in the vehicle width direction at the front of the automobile. The display device 58 includes a HUD 59 (Head Up Display) that displays various types of information at a position that does not obstruct the driver's front view in the front window.

  (1) According to the present embodiment, the driving support device 51 includes the infrared camera 41. The infrared camera 41 includes a light detection unit 43, and the ferroelectric element 25 arranged in a two-dimensional manner is used for the light detection unit 43. As the ferroelectric element 25, the ferroelectric element 1, the ferroelectric element 15, or the ferroelectric element 20 described above is used. The ferroelectric element 25 of the light detection unit 43 is an element having a low lead content and low noise. Therefore, the driving support device 51 can be an electronic device including the ferroelectric element 25 with a low lead content and low noise.

(Eighth embodiment)
Next, an embodiment of a security device which is one of electronic devices using an infrared camera equipped with a ferroelectric element will be described with reference to FIGS. FIG. 13 is a block diagram illustrating a configuration of a security device, and FIG. 14 is a schematic diagram illustrating a house in which the security device is installed.

  As shown in FIG. 13, a security device 62 as an electronic device includes an infrared camera 41 that captures a monitoring area and a human sensor 63 that detects an intruder into the monitoring area. Further, the security device 62 processes the image data output from the infrared camera 41 to detect a moving body that has entered the monitoring area, and a human sensor detection that performs a human sensor 63 detection process. A processing unit 65 is provided. Further, the security device 62 includes an image compression unit 66 that compresses image data output from the infrared camera 41 by a predetermined method, transmission of compressed image data and intruder detection information, and transmission from an external device to the security device 62. A communication processing unit 67 for receiving various setting information and the like is provided. Further, the security device 62 includes a control unit 68 that performs condition setting, processing command transmission, and response processing on each processing unit of the security device 62 by the CPU. And the same camera as the infrared camera 41 in the said embodiment is used for the infrared camera 41 of this embodiment. Therefore, the infrared camera 41 includes the ferroelectric element 25.

  The motion detection processing unit 64 includes a buffer memory (not shown), a block data smoothing unit to which an output of the buffer memory is input, and a state change detection unit to which an output of the block data smoothing unit is input. The state change detection unit of the motion detection processing unit 64 has the same image data even in different frames taken by a moving image if the monitoring area is stationary. A change in state is detected by utilizing the difference in image data.

  As shown in FIG. 14, the security device 62 has an infrared camera 41 and a human sensor 63 installed under the eaves. The infrared camera 41 detects the imaging area 69, and the human sensor 63 detects the detection area 70.

  (1) According to the present embodiment, the security device 62 includes the infrared camera 41. The infrared camera 41 includes a light detection unit 43, and the ferroelectric element 25 is used for the light detection unit 43. As the ferroelectric element 25, the ferroelectric element 1, the ferroelectric element 15, or the ferroelectric element 20 described above is used. The ferroelectric element 25 of the light detection unit 43 is an element having a low lead content and low noise. Therefore, the security device 62 can be an electronic device including the ferroelectric element 25 with a low lead content and low noise.

(Ninth embodiment)
Next, an embodiment of a game machine which is one of electronic devices provided with a ferroelectric element that detects infrared rays as an infrared detection element in a light detection unit that detects infrared rays will be described with reference to FIGS. 15 and 16. . FIG. 15 is a block diagram showing the configuration of the controller of the game machine, and FIG. 16 is a schematic diagram for explaining how to use the controller.

  As shown in FIG. 15, a controller 73 as an electronic device used for a game device includes an imaging information calculation unit 74, an operation switch 75, an acceleration sensor 76, a connector 77, a processor 78, a wireless module 79, It is configured with.

  The imaging information calculation unit 74 includes an imaging unit 80 and an image processing circuit 81 for processing image data captured by the imaging unit 80. The imaging unit 80 includes a light detection unit 82, and an infrared filter 83 that is a filter that is connected to the light detection unit 82 and transmits only infrared rays, and an optical system 84 such as a lens are disposed. Then, the image processing circuit 81 processes the infrared image data obtained from the imaging unit 80, detects a high-luminance portion, detects the position of the center of gravity and the area thereof, and outputs these data. The photodetector element 82 of the present embodiment uses the ferroelectric element 25 of the above embodiment, and the ferroelectric element 25 includes the ferroelectric element 1, the ferroelectric element 15, or the ferroelectric described above. A body element 20 is used.

  The processor 78 outputs the operation data from the operation switch 75, the acceleration data from the acceleration sensor 76, and the high luminance partial data as a series of control data. The wireless module 79 modulates a carrier wave of a predetermined frequency with this control data and outputs it as a radio signal from the antenna 85.

  Data input through the connector 77 provided in the controller 73 is also processed by the processor 78 in the same manner as the above-described data, and is output as control data via the wireless module 79 and the antenna 85.

  As shown in FIG. 16, the game device 86 includes a controller 73, a game machine main body 87, a display 88, an LED module 89, and an LED module 90. The player 91 holds the controller 73 with one hand and plays the game. When the imaging unit 80 of the controller 73 is directed toward the screen 92 of the display 88, the imaging unit 80 detects infrared rays output from the two LED modules 89 and the LED module 90 installed in the vicinity of the display 88.

  Then, the controller 73 acquires the position and area information of the two LED modules 89 and LED modules 90 as information on the high luminance point. The data of the position and size of the bright spot is wirelessly transmitted from the controller 73 to the game machine main body 87, and the game machine main body 87 receives the data. When the player 91 moves the controller 73, the position and size data of the bright spot changes. By utilizing this, the game machine main body 87 can acquire an operation signal corresponding to the movement of the controller 73. The game device 86 can advance the game according to the operation signal.

As described above, this embodiment has the following effects.
(1) According to this embodiment, the controller 73 of the game device 86 includes the light detection unit 82, and the ferroelectric element 25 is used for the light detection unit 82. The ferroelectric element 25 of the light detection unit 82 is an element having a low lead content and a small noise. Therefore, the game device 86 can be an electronic device having the controller 73 provided with the ferroelectric element 25 with a low lead content and low noise.

(Tenth embodiment)
Next, an embodiment of a body temperature measuring apparatus which is one of electronic devices using an infrared camera provided with a ferroelectric element for detecting infrared rays as an infrared detection element in a light detection unit will be described with reference to FIG. FIG. 17 is a block diagram showing the configuration of the body temperature measuring device.

  As shown in FIG. 17, a body temperature measuring device 95 as an electronic device includes an infrared camera 41, a body temperature analyzing device 96, an information communication device 97, and a cable 98. The same camera as the infrared camera 41 of the sixth embodiment is used as the infrared camera 41 of the present embodiment. Therefore, the infrared camera 41 includes the ferroelectric element 25.

  The infrared camera 41 captures a predetermined target area, and transmits image information of the captured subject 99 to the body temperature analyzer 96 via the cable 98. The body temperature analysis device 96 includes an image reading processing unit and a body temperature analysis processing unit. The image reading processing unit reads the heat distribution image from the infrared camera 41. The body temperature analysis processing unit creates a body temperature analysis table based on the data from the image reading processing unit and the image analysis setting table. Then, the body temperature analysis processing unit transmits body temperature information transmission data to the information communication device 97 based on the body temperature analysis table. The data for transmitting body temperature information may include predetermined data corresponding to abnormal body temperature. In addition, when it is determined that a plurality of subjects 99 are included in the imaging region, information on the number of subjects 99 and the number of people with abnormal body temperature may be included in the body temperature information transmission data.

As described above, this embodiment has the following effects.
(1) According to this embodiment, the body temperature measuring device 95 includes the infrared camera 41. The infrared camera 41 includes a light detection unit 43, and the ferroelectric element 25 is used for the light detection unit 43. As the ferroelectric element 25, the ferroelectric element 1, the ferroelectric element 15, or the ferroelectric element 20 described above is used. The ferroelectric element 25 of the light detection unit 43 is an element having a low lead content and low noise. Therefore, the body temperature measuring device 95 can be an electronic device including the infrared camera 41 having the ferroelectric element 25 with a low lead content and low noise.

(Eleventh embodiment)
Next, a block diagram showing a configuration of the specific substance detection apparatus of FIG. 18 for one embodiment of a specific substance detection apparatus which is one of electronic devices including a ferroelectric element for detecting infrared rays as an infrared detection element in a light detection unit. Will be described.

  As shown in FIG. 18, the specific substance detection device 102 as an electronic device includes a control unit 103, an irradiation light unit 104, an optical filter 105, an imaging unit 106, and a display unit 107. The imaging unit 106 includes an optical system such as a lens (not shown) and a light detection unit, and the light detection unit includes a ferroelectric element 25 including an infrared absorption film that absorbs a wavelength in the terahertz range.

  The control unit 103 includes a system controller that controls the entire apparatus, and the system controller controls the light source driving unit and the image processing unit included in the control unit. The irradiation light unit 104 includes a laser device and an optical system that emits terahertz light that is an electromagnetic wave having a wavelength in the range of 100 μm to 1000 μm, and irradiates the person 108 to be inspected with terahertz light. The reflected terahertz light from the person 108 is received by the imaging unit 106 via the optical filter 105 that allows only the spectral spectrum of the specific substance 109 to be detected to pass. The image signal generated by the imaging unit 106 is subjected to predetermined image processing by the image processing unit of the control unit 103, and the image signal is output to the display unit 107. The presence of the specific substance 109 can be determined because the intensity of the received light signal varies depending on whether or not the specific substance 109 exists in the clothes of the person 108.

As described above, this embodiment has the following effects.
(1) According to the present embodiment, the specific substance detection apparatus 102 includes the light detection unit in the imaging unit 106, and the ferroelectric element 25 is used for the light detection unit. As the ferroelectric element 25, the ferroelectric element 1, the ferroelectric element 15, or the ferroelectric element 20 described above is used. The ferroelectric element 25 of the light detection unit is an element having a low lead content and a low noise. Therefore, the specific substance detection device 102 can be an electronic device including the ferroelectric element 25 with a low lead content and low noise.

(Twelfth embodiment)
Next, a characteristic example of an ultrasonic diagnostic imaging apparatus that is one of electronic devices including a ferroelectric element will be described with reference to the drawings. An ultrasonic diagnostic imaging apparatus will be described with reference to FIGS. FIG. 19 is a schematic perspective view showing the configuration of the ultrasonic diagnostic imaging apparatus. As shown in FIG. 19, the ultrasonic diagnostic imaging apparatus 112 as an electronic apparatus includes an ultrasonic probe 113 as an ultrasonic apparatus. The ultrasonic probe 113 has a substantially rectangular parallelepiped shape that is long in one direction. The longitudinal direction of the ultrasonic probe 113 is defined as the Z direction. The surface in the + Z direction of the ultrasonic probe 113 is a substantially flat surface, and the planar shape is a rectangle. The directions in which two orthogonal sides of the planar shape extend are defined as an X direction and a Y direction.

  An ultrasonic sensor 114 is installed on the + Z direction side of the ultrasonic probe 113. On the surface on the + Z direction side of the ultrasonic probe 113, the ultrasonic sensor 114 is exposed from the housing. A control unit 115 that controls the ultrasonic sensor 114 is installed inside the ultrasonic probe 113, and the ultrasonic sensor 114 and the control unit 115 are connected by a cable 116. The control unit 115 includes a CPU (Central Processing Unit) and a storage device. The storage device stores drive waveform data for driving the ultrasonic sensor 114 and a program indicating a procedure for driving the ultrasonic sensor 114. Then, the CPU drives the ultrasonic sensor 114 by outputting a drive waveform to the ultrasonic sensor 114 according to the program.

  The ultrasonic probe 113 is connected to the control device 118 via a cable 117. The control device 118 is a device that receives a data signal output from the ultrasonic probe 113 and analyzes and displays the data signal.

  The ultrasonic probe 113 is used by being pressed against the surface of the living body 119. The ultrasonic probe 113 emits ultrasonic waves from the ultrasonic sensor 114 toward the living body 119. Then, the ultrasonic sensor 114 receives the reflected wave reflected inside the living body 119. Since the reflected wave has a different return time depending on the reflected surface, the internal structure of the living body 119 can be nondestructively inspected by analyzing the return time of the reflected wave. The reflected wave signal received by the ultrasonic sensor 114 is output to the control unit 115. The control unit 115 includes an A / D conversion unit (Analog-to-digital), and converts a reflected wave signal into digital data. The data signal converted into digital data is transmitted to the control device 118 via the cable 116, the control unit 115, and the cable 117. The control device 118 receives and analyzes the reflected wave data signal. Then, the control device 118 converts the internal structure of the living body 119 into an image and displays it.

  FIG. 20 is a schematic perspective view showing the structure of the ultrasonic sensor. As shown in FIG. 20, the ultrasonic sensor 114 includes a substrate 120. Ultrasonic elements 121 are arranged in a matrix on the surface of the substrate 120 on the + Z direction side. In the drawing, the Y direction is a first direction 122, and the X direction is a second direction 123. The ultrasonic elements 121 are aligned in the first direction 122 and the second direction 123. The ultrasonic elements 121 aligned in the first direction 122 are referred to as a first ultrasonic element array 124, and the ultrasonic elements 121 aligned in the second direction 123 are referred to as a second ultrasonic element array 125. The ultrasonic element 121 has a function of emitting ultrasonic waves and a function of receiving reflected waves and converting them into electrical signals. The ultrasonic sensor 114 may include an element that emits ultrasonic waves and an element that receives reflected waves and converts them into electrical signals.

  In the present embodiment, for the sake of easy understanding, for example, the number of first ultrasonic element rows 124 in the drawing is 20 and the number of second ultrasonic element rows 125 is 6. Therefore, in the ultrasonic sensor 114, an ultrasonic element group 126 having 120 ultrasonic elements 121 is installed on the substrate 120. If the number of the first ultrasonic element rows 124 is 32 or more and the number of the second ultrasonic element rows 125 is 256 or more, the resolution becomes high, so that the detected ultrasonic image can be easily seen.

  Each ultrasonic element 121 in the first ultrasonic element row 124 is connected to a second electrode wiring 127 extending in the first direction 122. Similarly, each ultrasonic element 121 of the second ultrasonic element row 125 is connected to a third electrode wiring 128 extending in the second direction 123. A flexible cable 129 is installed at the end of the substrate 120 on the −Y direction side, and the second electrode wiring 127 is connected to the flexible cable 129. A flexible cable 130 is installed at the + X direction end of the substrate 120, and the third electrode wiring 128 is connected to the flexible cable 130.

  Further, each ultrasonic element 121 is connected to the first electrode wiring 131, and the first electrode wiring 131 is also connected to the flexible cable 129. The second electrode wiring 127 and the third electrode wiring 128 are connected to the control unit 115 via the cable 116. Then, the control unit 115 outputs a voltage signal to each ultrasonic element 121 through the second electrode wiring 127, the third electrode wiring 128, and the first electrode wiring 131. The ultrasonic element 121 receives a voltage signal and emits an ultrasonic wave according to the voltage signal.

  FIG. 21 is a schematic side sectional view showing the structure of the ultrasonic element. As shown in FIG. 21, the substrate 120 is provided with a recess 133 at a location facing the ultrasonic element 121. A part of the substrate 120 is thinned by the recess 133, and a vibration part 134 that vibrates in a thin place. The substrate 120 is a silicon substrate, and the recess 133 is formed by etching. In the vibrating portion 134, a silicon oxide film and a zirconium oxide film are stacked.

  A first electrode 135 is provided on the + Z direction side of the vibration part 134. The first electrode 135 is connected to the first electrode wiring 131. On the first electrode 135, the first ferroelectric layer 4 and the second ferroelectric layer 5 are disposed so as to overlap each other. A second electrode 136 is provided on the second ferroelectric layer 5. The first electrode 135, the first ferroelectric layer 4, the second ferroelectric layer 5, and the second electrode 136 constitute a ferroelectric element 137. An insulating film 138 is provided on the second electrode 136. A through hole is formed in the insulating film 138 on the second electrode 136. Further, the insulating film 138 is provided so as to cover the ferroelectric element 137 and the first electrode 135.

  A third electrode 139 is provided on the insulating film 138 at a location facing the second electrode 136. The third electrode 139 is connected to the third electrode wiring 128 extending in the second direction 123. The second electrode 136 and the third electrode 139 function as a capacitor with the insulating film 138 interposed therebetween.

  Further, a resistor 140 is provided on the insulating film 138 on the −Y direction side of the ferroelectric element 137. The resistor 140 is a film having electrical resistance. A connection wiring 143 that connects both ends of the resistor 140 and the second electrode 136 is provided. The connection wiring 143 is installed in the through hole and connected to the second electrode 136 through the through hole. Furthermore, the other end of the resistor 140 is connected to the second electrode wiring 127.

  On the insulating film 138, the second electrode wiring 127 is disposed through the + X direction side of the ferroelectric element 137. The second electrode wiring 127 is a wiring extending in the first direction 122. An insulating film 144 is provided to cover the second electrode wiring 127, the ferroelectric element 137, the third electrode 139, and the like.

As described above, this embodiment has the following effects.
(1) According to this embodiment, the ultrasonic diagnostic imaging apparatus 112 includes the ultrasonic element 121, and the ferroelectric element 137 is used for the ultrasonic element 121. The ferroelectric element 137 is an element in which a first ferroelectric layer 4 and a second ferroelectric layer 5 are laminated. Therefore, the ferroelectric element 137 is an element having a low lead content and a small noise. Therefore, the ultrasonic diagnostic imaging apparatus 112 can be an electronic device including the ferroelectric element 137 with low lead content and low noise.

  Although several embodiments have been described above, those skilled in the art can easily understand that many modifications are possible without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term anywhere in the specification or the drawings.

  The present invention can be widely applied to electronic devices using various ferroelectric elements. The wavelength of the light to detect is not ask | required. In addition, an electronic device having a ferroelectric element can be applied to, for example, a flow sensor that detects the flow rate of a fluid under a condition in which the amount of heat supplied and the amount of heat taken by the fluid are balanced. An electronic device including the ferroelectric element of the present invention can be provided in place of the thermocouple provided in the flow sensor, and other than light can be detected.

Note that the present embodiment is not limited to the above-described embodiment, and various changes and improvements can be added by those having ordinary knowledge in the art within the technical idea of the present invention. A modification will be described below.
(Modification 1)
In the first embodiment, the second ferroelectric layer 5 is provided so as to overlap the first ferroelectric layer 4. There may be a conductive layer between the first ferroelectric layer 4 and the second ferroelectric layer 5. Also at this time, the first ferroelectric layer 4 and the second ferroelectric layer 5 function as piezoelectric bodies. And the same effect can be acquired. Also in the second embodiment, there may be a conductive layer between the first ferroelectric layer 16 and the second ferroelectric layer 17. Also at this time, the first ferroelectric layer 16 and the second ferroelectric layer 17 act as piezoelectric bodies. And the same effect can be acquired. The same applies to the third embodiment, and the same effect can be obtained.

(Modification 2)
In the second embodiment, the first ferroelectric layer 16, the second ferroelectric layer 17, and the second electrode 6 are stacked in this order on the first electrode 3. The second ferroelectric layer 17, the first ferroelectric layer 16, and the second electrode 6 may be laminated on the first electrode 3 in this order. Also at this time, the same effect as that of the ferroelectric element 15 can be obtained.

  DESCRIPTION OF SYMBOLS 1,15,20,25 ... Ferroelectric element, 3 ... 1st electrode, 4,16 ... 1st ferroelectric layer, 5,17 ... 2nd ferroelectric layer, 6 ... 2nd electrode, 24 ... Heat Sensor array as electrical conversion device, 35 ... Sensor device as electronic device, 36 ... Sensor array as light detection unit, 41 ... Infrared camera as electronic device, 51 ... Driving support device as electronic device, 62 ... Electronic device As a security device, 73 as a controller as an electronic device, 95 as a body temperature measuring device as an electronic device, 102 as a specific substance detection device as an electronic device, and 112 as an ultrasonic diagnostic imaging device as an electronic device.

Claims (9)

A first electrode and a second electrode;
A first ferroelectric layer disposed between the first electrode and the second electrode and having a perovskite structure;
A second ferroelectric layer disposed between the first ferroelectric layer and the second electrode and having a perovskite structure;
The first ferroelectric layer has a higher electrical resistance than the second ferroelectric layer,
The ferroelectric element, wherein the second ferroelectric layer does not contain lead. The ferroelectric element according to claim 1, wherein
The first ferroelectric layer includes lead, zirconium, and titanium;
The ferroelectric element, wherein the second ferroelectric layer contains bismuth, lanthanum, and iron. The ferroelectric element according to claim 1, wherein
The first ferroelectric layer includes lead, zirconium, and titanium;
The ferroelectric element, wherein the second ferroelectric layer contains bismuth, gadolinium, and iron. The ferroelectric element according to claim 2, wherein
The ferroelectric element, wherein the second ferroelectric layer contains manganese. A ferroelectric element according to any one of claims 1 to 4, wherein
The ferroelectric element, wherein the second ferroelectric layer is oriented in (111). A ferroelectric element according to any one of claims 1 to 5, wherein
The ferroelectric element, wherein the first ferroelectric layer is thinner than the second ferroelectric layer.   A thermoelectric conversion device, wherein the ferroelectric elements according to any one of claims 1 to 6 are two-dimensionally arranged. An electronic device including a light detection unit that detects infrared rays,
An electronic apparatus comprising the thermoelectric conversion device according to claim 7 in the light detection unit.   An electronic apparatus comprising the ferroelectric element according to claim 1.

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