JP5691502B2 - THERMAL TYPE PHOTODETECTOR, THERMAL TYPE PHOTODETECTOR, ELECTRONIC DEVICE, AND THERMAL TYPE OPTICAL DETECTOR - Google Patents

Description

  The present invention relates to a thermal detector, a thermal detector, an electronic apparatus, a manufacturing method of the thermal detector, and the like.

  A thermal detector is known as an optical sensor. The thermal detector absorbs light emitted from an object by a light absorption layer, converts the light into heat, and measures a change in temperature with a heat detection element. Thermal detectors include a thermopile that directly detects a temperature rise accompanying light absorption, a pyroelectric element that detects a change in electrical polarization, and a bolometer that detects a temperature rise as a resistance change. Thermal detectors have a wide wavelength band that can be measured. In recent years, attempts have been made to manufacture smaller thermal detectors using semiconductor manufacturing technology (MEMS technology or the like).

  In order to improve the detection sensitivity and the responsiveness of the thermal detector, it is important to efficiently transfer the heat generated in the light absorption layer to the heat detection element.

  The structure of the heat detection element for improving the efficiency of heat transfer is described in Patent Document 1, for example. The infrared detection element (here, a thermopile type infrared detection element) described in Patent Document 1 has a high thermal conductive layer provided between an infrared detection unit and an infrared absorption layer. Specifically, a membrane is formed on the cavity, and the membrane is supported on the surrounding substrate by protruding beams provided at four corners. The central membrane portion is provided with an infrared absorption layer and a high thermal conductive layer, and the beam portion is provided with a thermopile element. The high thermal conductive layer is made of a material having excellent infrared reflectivity such as aluminum and gold.

Japanese Patent No. 3339276 No. 99/31471

    Moreover, in the infrared detection element described in Patent Document 1, a high heat transfer member is provided under the light absorption layer, but the heat detection element is not provided under the light absorption layer and the high heat transfer member. . Since the light infrared absorption layer is located away from the infrared detection unit heat detection element, the heat generated in the light infrared absorption layer cannot be directly supplied to the heat detection element infrared detection unit.

  In the infrared solid-state imaging device described in Patent Document 2, since the insulating layer constituting the infrared absorbing unit is located away from the temperature detector, the heat generated in the insulating layer of the infrared absorbing unit is directly heated. It cannot be supplied to the detector.

  According to at least one aspect of the present invention, for example, the detection sensitivity of a thermal detector can be improved.

A thermal detector according to one aspect of the present invention includes a substrate, a support member supported by the substrate via a cavity, and a pyroelectric material formed on the support member, the lower electrode and the upper electrode. A heat detection element having a structure sandwiching layers, a light absorption layer formed on the heat detection element, and the heat detection element are connected to the connection part by a connection part, and have a larger area than the connection part in plan view. And a heat transfer member that has a light-transmitting property with respect to light in at least a part of the wavelength range and includes a heat collecting part formed inside the light absorption layer, and the lower electrode includes: It has an extending part extending so as to surround the pyroelectric material layer in plan view, and the extending part is at least a part of the light transmitted through the heat collecting part of the heat transfer member It has a light reflection characteristic of reflecting light.
(1) One aspect of the thermal detector of the present invention is a substrate, a support member supported by the substrate via a cavity, and formed on the support member, and includes a lower electrode and an upper electrode. A thermal detection element having a structure sandwiching a pyroelectric material layer, a light absorption layer formed on the thermal detection element, and connected to the thermal detection element by a connection portion, and wider than the connection portion in plan view A heat transfer member having an area, having a light transmission property for light in at least a part of a wavelength range, and having a heat collecting portion formed inside the light absorption layer, and the lower portion The electrode has an extending portion extending around the pyroelectric material layer in a plan view, and the extending portion is at least a part of light transmitted through the heat collecting portion of the heat transfer member. It has a light reflection characteristic to reflect the light.

  In the thermal detector of this aspect, for example, a part of light (for example, infrared rays) incident on the thermal detector is first absorbed by the second light absorption layer, and the other is not absorbed by the heat transfer member. To reach. The heat transfer member is light transmissive with respect to light in at least a part of the wavelength range, and can be semi-transmissive in, for example, an infrared region (for example, a far infrared region). In the heat transfer member, for example, a part of the reached light is reflected and the other is transmitted through the heat transfer member. Part of the light transmitted through the heat transfer member is absorbed by the first light absorption layer, and the other light reaches the heat detection element.

  The heat detection element is formed on the support member. Here, the expression “to upper” may be directly above or may be an upper part (when another layer is interposed). In other places as well, it can be interpreted broadly.

  Further, the lower electrode of the heat detection element has an extending portion extending on the support member, and the extending portion has light reflection characteristics. That is, the lower electrode is made of a material having excellent conductivity (for example, a metal material). Generally, a metal material or the like has a high light reflectance. Therefore, most of the incident light is reflected on the surface of the extended portion of the lower electrode, which is a component of the heat detection element, and the reflected light is absorbed by the first light absorption layer and the second light absorption layer. Is done. Therefore, incident light can be converted into heat by using it without waste. In addition, part of the light reaching the surface of the support member may be reflected and absorbed by the first light absorption layer or the second light absorption layer. Also in this respect, the incident light can be effectively used.

  In addition, since the lower electrode (made of a metal material or the like) has high thermal conductivity, for example, the effect of transferring heat generated at a location far from the pyroelectric material layer in the light absorption layer to the pyroelectric material layer. Also demonstrates. That is, since the lower electrode extends, for example, widely on the support member, heat generated in a wide range in the light absorption layer can be efficiently transmitted to the pyroelectric material layer. In this respect, the lower electrode is a heat transfer member (ie, a second heat transfer member) that is different from the heat transfer member (ie, the heat transfer member (eg, the first heat transfer member) that is formed on the heat detection element) It can also be called a member))).

  The heat transfer member is made of a material having optical transparency (for example, semi-transmission of light), and includes a connection part and a heat collection part having a larger area than the connection part in plan view. The part is formed on the heat detection element. The heat collecting part of the heat transfer member plays a role of collecting heat generated in a wide area and transmitting it to the heat detection element, for example. As the heat transfer member, for example, a metal compound (for example, AlN or AlOx) having good heat conduction and light translucency can be used.

  The generation of heat in the first light absorption layer and the second light absorption layer and the transfer of the generated heat to the heat detection element in the case where the incident light exhibits the behavior described above are, for example, as follows: To be done. That is, a part of the light incident on the thermal detector is first absorbed by the second light absorption layer, and heat is generated in the second light absorption layer. In addition, the light reflected by the heat transfer member is absorbed by the second light absorption layer, thereby generating heat in the second light absorption layer.

  Further, a part of the light transmitted (passed) through the heat transfer member is absorbed by the first light absorption layer to generate heat. In addition, most (for example, most) of the light reaching the extended portion of the lower electrode is reflected on the surface and absorbed by at least one of the first light absorption layer and the second light absorption layer, Heat is generated in the first light absorption layer or the second light absorption layer. In addition, the light reflected on the surface of the support member is also absorbed by at least one of the first light absorption layer and the second light absorption layer, thereby generating heat in the first light absorption layer or the second light absorption layer. .

  The heat generated in the second light absorption layer is efficiently transmitted to the heat detection element via the heat transfer member, and the heat generated in the first light absorption layer is directly or heat transfer member. Is efficiently transmitted to the heat detection element via the. That is, the heat collecting part of the heat transfer member is formed so as to cover the heat detection element widely, and therefore, most of the heat generated by the first light absorption layer and the second light absorption layer is transferred to the generation location. Regardless, it can be efficiently transmitted to the heat detection element. For example, even heat generated at a location away from the heat detection element can be efficiently transferred to the heat detection element via a heat transfer member having high thermal conductivity.

  In addition, since the heat collection part of the heat transfer member and the heat detection element are connected by the connection part of the heat transfer member, the heat transmitted through the heat collection part of the heat transfer member is transferred to the connection part. It can be directly transmitted to the heat detection element via the. In addition, since the heat detection element is located below the heat transfer member (provided at a position overlapping in plan view), for example, the central portion of the heat transfer member in plan view and the heat detection element are connected in the shortest distance. Is possible. Therefore, the loss accompanying heat transfer can be reduced, and an increase in the occupied area can be suppressed.

  Moreover, in this aspect, since heat is generated by the two light absorption films, the absorption efficiency is increased. Further, heat can be directly transferred to the heat detection element via the first light absorption layer. Therefore, compared with the infrared detection element described in Patent Document 1 and the infrared solid-state imaging element described in Patent Document 2, the detection sensitivity of the thermal detector can be further improved. In the present embodiment, the heat detection element is connected to the heat transfer member. Therefore, the response speed is as high as the infrared detection element described in Patent Document 1. Moreover, in this aspect, since the heat transfer member is directly connected to the heat detection element, a higher response speed can be obtained as compared with the infrared solid-state imaging element described in Patent Document 2.

  (2) In another aspect of the thermal detector of the present invention, the light absorption layer is formed on the support member and around the thermal detection element.

  In this aspect, the light absorption layer is formed around the heat detection element in a plan view. Thereby, the heat generated in a wide range of the light absorption layer is efficiently transmitted to the heat detection element directly or indirectly via the heat transfer member. Therefore, the photodetection sensitivity of the thermal detector can be further increased. Moreover, the response speed of the thermal detector is further improved.

  (3) In another aspect of the thermal detector of the present invention, the light absorption layer includes the heat transfer member between the heat transfer member and the extended portion of the lower electrode of the heat detection element. A first light absorption layer formed in contact with the heat transfer member, and a second light absorption layer formed in contact with the heat transfer member on the heat transfer member.

  In this embodiment, a first light absorption layer and a second light absorption layer are provided as the light absorption layer, and a configuration in which the heat collection portion of the heat transfer member is sandwiched between these two light absorption layers is employed. Heat generated in a wide range of the first light absorption layer and the second light absorption layer is efficiently transmitted to the heat detection element directly or indirectly via a heat transfer member. Further, light reflected by the heat transfer member of incident light may be absorbed by the upper second light absorption layer, and light transmitted through the heat transfer member may be absorbed by the lower first light absorption layer. it can.

  According to the thermal detector of this aspect, the heat generated in a wide range in the two layers (multiple layers) of the light absorption layer can be efficiently transferred to the thermal detection element. The light detection sensitivity of the detector can be greatly improved. In addition, since the time required for heat transfer is shortened, the response speed of the thermal detector can be increased.

  (4) In another aspect of the thermal detector of the present invention, a first optical resonator for a first wavelength is provided between the surface of the extending portion of the lower electrode and the upper surface of the second light absorption layer. A second optical resonator for a second wavelength different from the first wavelength is configured between the lower surface of the second light absorbing layer and the upper surface of the second light absorbing layer. Yes.

  In this embodiment, two optical resonators having different resonance wavelengths are configured by adjusting the film thickness of each light absorption layer. The first optical resonator for the first wavelength is formed between the surface of the extending portion of the lower electrode, which is a component of the thermal detector, formed on the support member, and the upper surface of the second light absorption layer. Formed in. The light reflected by the surface of the extended portion of the lower electrode is absorbed by at least one of the first light absorption layer and the second light absorption layer. At this time, each light is formed by configuring the first optical resonator. The effective absorption rate in the absorption layer can be increased. The lower electrode is made of a material having excellent conductivity (for example, a metal material). Generally, a metal material or the like has a high light reflectance. Therefore, most of the light incident on the surface of the extending portion can be reflected upward. Therefore, light resonance tends to occur.

  Here, the first optical resonator can be, for example, a so-called λ / 4 optical resonator. That is, when the first wavelength is λ1, the distance between the surface of the extended portion RX of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 and the upper surface of the second light absorption layer is n · (λ1 / 4) The film thicknesses of the first light absorption layer and the second light absorption layer may be adjusted so as to satisfy the relationship (n is an integer of 1 or more). If the thickness of the lower electrode is very thin, the thickness can be ignored. In this case, the total thickness of the first light absorption layer and the second light absorption layer is n · (λ1 / 4). ) (N is an integer of 1 or more). Thereby, the incident light of wavelength λ1 and the light of wavelength λ1 reflected by the surface of the support member are canceled by mutual interference, and the effective absorption rate in the first light absorption layer and the second light absorption layer is increased.

  Further, as described above, the light reflected by the heat transfer member is absorbed by the second light absorption layer. At this time, by configuring the second optical resonator, the effective absorption rate in the second light absorption layer is increased. Can be increased. The second optical resonator can be, for example, a so-called λ / 4 optical resonator.

  That is, when the second wavelength is λ2, the distance between the lower surface of the second light absorption layer and the upper surface of the second light absorption layer (that is, the film thickness of the second light absorption layer) is n · (λ2 / By setting to 4), the second optical resonator can be configured. As a result, the incident light having the wavelength λ2 and the light having the wavelength λ2 reflected by the lower surface of the second light absorption layer (the interface between the first light absorption layer and the second light absorption layer) are canceled by mutual interference. The effective absorption rate in the two-light absorption layer can be increased.

  Moreover, according to this aspect, since resonance peaks occur at two different wavelengths, the wavelength band (wavelength width) of light that can be detected by the thermal detector can be expanded. In addition, the heat collection part of the heat transfer member and the light reflection layer are arranged in parallel to each other. Therefore, the parallelism between the upper surface of the light reflection layer and the upper surface of the second light absorption layer is maintained.

  (5) In another aspect of the thermal detector of the present invention, the heat transfer member also serves as a wiring for connecting the heat detection element to another element.

  As described above, the heat transfer member can be composed of, for example, a metal compound such as AlN or AlOx. However, since the metal-based material has good electrical conductivity, the heat transfer member can detect heat. It can also be used as wiring (including part of the wiring) for connecting the element to other elements. By using the heat transfer member also as the wiring, it is not necessary to separately provide the wiring, and the manufacturing process can be simplified.

  (6) In one aspect of the thermal detection device of the present invention, a plurality of the thermal detection detectors described above are two-dimensionally arranged.

  Thus, a plurality of thermal photodetectors (thermal photodetector elements) are two-dimensionally arranged (for example, arranged in an array along each of two orthogonal axes), and a thermal photodetector (thermal Type optical array sensor) is realized.

  (7) One aspect of the electronic device of the present invention includes the thermal detector according to any one of the above, and a control unit that processes an output of the thermal detector.

  Any of the above thermal detectors has high light detection sensitivity. Therefore, the performance of an electronic device equipped with this thermal detector is enhanced. Examples of the electronic device include an infrared sensor device, a thermography device, a vehicle-mounted night camera, a monitoring camera, and the like. Note that the control unit can be configured by, for example, an image processing unit or a CPU.

  (8) According to one aspect of the thermal detector of the present invention, a structure including an insulating layer is formed on a main surface of a substrate, a sacrificial layer is formed on the structure including the insulating layer, and the sacrificial layer A step of forming a support member thereon, and a structure in which a pyroelectric material layer is sandwiched between the lower electrode and the upper electrode on the support member, and the lower electrode is in plan view, the pyroelectric material layer And a step of forming a heat detection element having a light reflection characteristic for reflecting incoming light, and a first light so as to cover the heat detection element. Forming an absorption layer and planarizing the first light absorption layer; forming a contact hole in a part of the first light absorption layer; and then providing thermal conductivity and at least a part of a wavelength range of light. By forming a material layer having optical transparency and patterning the material layer, Forming a heat transfer member including a connection part connected to the heat detection element and a heat collecting part having a larger area than the connection part in plan view; and a second light absorption layer on the first light absorption layer A step of patterning the first light absorption layer and the second light absorption layer, a step of patterning the support member, and removing the sacrificial layer by etching to form a main surface of the substrate. And a step of forming a cavity between the structure including the insulating layer formed on the support member and the support member.

  In this embodiment, a multilayer structure including an interlayer insulating layer, a sacrificial layer, and a support member are stacked on the main surface of the substrate, and the lower electrode having light reflection characteristics (that is, also serves as the light reflection member) is formed on the support member. A heat detecting element including a lower electrode), a first light absorption layer, a heat transfer member, and a second light absorption layer. The upper surface of the first light absorption layer is planarized by a planarization process. In addition, a contact hole is provided in the first light absorption layer, and a connection portion of the heat transfer member is embedded in the contact hole. The heat collection part of the heat transfer member provided on the first light absorption layer is connected to a heat detection element (for example, the upper electrode of the pyroelectric capacitor) via the connection part. According to this aspect, it is possible to realize a small thermal detector with high detection sensitivity using semiconductor manufacturing technology (for example, MEMS technology). In addition, it is preferable to arrange | position the heat collection part of a heat-transfer member, and a light reflection layer mutually in parallel. Thereby, the parallelism between the upper surface of the light reflection layer and the upper surface of the second light absorption layer is maintained.

  Thus, according to at least one aspect of the present invention, for example, the detection sensitivity of a thermal detector can be significantly improved.

1A and 1B are a plan view and a cross-sectional view of an example of a thermal detector. 2A and 2B are diagrams showing examples of spectral characteristics (light reflection characteristics and light transmission characteristics) of the alumina plate in the far-infrared wavelength region, and two optical resonators are configured. Is a diagram showing an example of the detection sensitivity of the thermal detector in the case 3 (A) to 3 (E) are diagrams showing the main steps until the first light absorption layer is formed in the method for manufacturing a thermal detector. 4 (A) to 4 (C) are diagrams showing main steps until the first light absorption layer and the second light absorption layer are patterned in the method of manufacturing a thermal detector. 5 (A) and 5 (B) are diagrams showing main steps until the thermal photodetector is completed in the method for manufacturing the thermal photodetector. The figure which shows the other example of a thermal type photodetector Circuit diagram showing an example of a circuit configuration of a thermal detection device (thermal detection array) FIG. 7 illustrates an example of a structure of an electronic device FIG. 11 is a diagram illustrating another example of a structure of an electronic device

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

(First embodiment)
FIG. 1A and FIG. 1B are a plan view and a cross-sectional view of an example of a thermal detector. FIG. 1B is a cross-sectional view taken along the line AA ′ of the thermal detector shown in FIG. In FIGS. 1A and 1B, a single thermal detector is shown, but a plurality of thermal detectors are arranged in a matrix, for example, and a thermal detector array ( That is, a thermal detection device) can also be configured.

  The thermal photodetector shown in FIGS. 1A and 1B is a pyroelectric infrared detector (a kind of optical sensor) 200 (however, it is only an example and is not limited thereto). Absent). The pyroelectric infrared detector 200 transmits heat generated by light absorption in the two light absorption films 270 and 272 through a heat transfer member 260 having good heat conduction to a heat detection element (here, pyroelectric). It can be efficiently transmitted to the capacitor 230).

  The heat transfer member 260 has, for example, high thermal conductivity and at least a part of the wavelength band (at least a part of the wavelength band of the wavelength band (wavelength width) in which the thermal detector has detection sensitivity). For example, a metal compound such as AlN or AlOx). In addition, the light transmittance in the heat transfer member 260 will be described later with reference to FIG.

  The pyroelectric capacitor 230 as a heat detection element converts heat into an electric signal. Thereby, a detection signal (for example, a current signal) corresponding to the intensity of the received light is obtained. A pyroelectric capacitor 230 as a heat detection element is formed on the support member 215. Here, the expression “to upper” may be directly above or may be an upper part (when another layer is interposed). In other places as well, it can be interpreted broadly. This will be specifically described below.

(Example of the structure of a pyroelectric infrared detector as a thermal detector)
First, a cross-sectional structure is described with reference to FIG.

(Cross-section structure)
A pyroelectric infrared detector 200 as a thermal detector is constituted by a multilayer structure formed on a substrate (silicon substrate) 10. That is, the pyroelectric infrared detector as the thermal detector 200 is formed on a substrate (here, a silicon substrate) 10 and a first main surface (here, a surface) of the substrate 10, A structure 100 including an insulating layer (for example, a multilayer structure including an interlayer insulating layer: see FIG. 6 for a specific example of the multilayer structure), and an etching stopper film 130a formed on the surface of the structure 100 including the insulating layer; , Formed on the support member (membrane) 215 including the cavity portion (heat separation cavity) 102 for heat separation, the mounting portion 210 and the arm portions 212a and 212b, and the support member (membrane) 215. Pyroelectric capacitor 230 as a heat detection element, insulating layer 250 covering the surface of pyroelectric capacitor 230, first light absorption layer (for example, SiO ₂ layer) 270, and heat transfer member 260 (connection) Part CN and heat collecting part FL), and a second light absorption layer (for example, SiO ₂ layer) 272.

  The pyroelectric capacitor 230 includes a lower electrode (first electrode) 234, a pyroelectric material layer 232, and an upper electrode (second electrode) 236. Further, the lower electrode of the pyroelectric capacitor 230 has an extended portion RX extending around the pyroelectric material layer in a plan view (a plan view seen from a direction perpendicular to the surface of the substrate). RX has a light reflection characteristic of reflecting at least a part of the light transmitted through the heat collecting part FL of the heat transfer member 260. The “extending portion” can be rephrased as “an overhanging portion” or “an extended portion”.

  The first light absorption layer 270 is formed between the heat transfer member 260 (specifically, the heat collecting portion FL of the heat transfer member 260) and the extending portion RX of the lower electrode of the heat detection element (pyroelectric capacitor 230). The heat transfer member 260 (specifically, the heat collecting part FL of the heat transfer member 260) is formed in contact with the heat transfer member 260.

  The second light absorption layer 272 is formed on the heat transfer member 260 (specifically, the heat collection part of the heat transfer member 260) on the heat transfer member 260 (specifically, the heat collection part FL of the heat transfer member 260). FL).

  That is, the lower electrode 234 is made of a material having excellent conductivity (for example, a metal material). Generally, a metal material or the like has a high light reflectance. Therefore, most of the incident light is reflected on the surface of the extending portion RX of the lower electrode 234 that is a component of the pyroelectric capacitor 230, and the reflected light is reflected by the first light absorption layer 270 and the second light absorption. Absorbed at layer 272. Therefore, incident light can be converted into heat by using it without waste. In addition, part of the light reaching the surface of the support member 215 may be reflected and absorbed by the first light absorption layer 270 and the second light absorption layer 272. Also in this respect, the incident light can be effectively used.

  In the example of FIG. 1A and FIG. 1B, the extending portion RX of the lower electrode 234 is formed to extend to the outer periphery of the heat transfer member 260 in plan view. The extending portion RX can be extended to the outside of the outer periphery of the heat transfer member 260, and conversely, the extension can be stopped inside the outer periphery of the heat transfer member 260. However, if the area of the extended portion RX in the lower electrode 234 is too small, the effect of efficiently reflecting the light transmitted through the heat collecting portion FL of the heat transfer member 260 is weakened. Therefore, it is preferable that the extending portion RX is formed so as to protrude to at least the outer periphery (near the outer periphery) of the heat transfer member 260 in plan view. In addition, the extended portion RX is preferably provided around the pyroelectric material layer 232 in a plan view from the viewpoint of effectively using incident light. More preferably, it is provided around the entire circumference.

  In addition, since the lower electrode 234 is made of a metal material and has high thermal conductivity, for example, heat generated at a location far from the pyroelectric material layer 232 in the first light absorption layer 270 is transferred to the pyroelectric material layer 232. In addition, the effect of transmitting efficiently is also demonstrated. That is, since the lower electrode 234 extends, for example, widely on the support member 215, heat generated in a wide range in the first light absorption layer 270 can be efficiently transmitted to the pyroelectric material layer 232. Is possible. In this respect, the lower electrode 234 is a heat transfer member (i.e., a heat transfer member (a first heat transfer member, which is formed on the pyroelectric capacitor 230, for example). It can also be said that it also serves as two heat transfer members))).

  The substrate 10 and the multilayer structure 100 constitute a base (base). The base (base) supports the element structure 160 including the support member 215 and the pyroelectric capacitor 230 in the cavity 102. Further, for example, a semiconductor element such as a transistor or a resistor can be formed in a region of the silicon (Si) substrate 10 that overlaps the heat detection element (pyroelectric capacitor 230) in plan view (for example, the example of FIG. 6). See).

As described above, the etching stopper film (for example, Si ₃ N ₄ film) 130 a is provided on the surface of the multilayer structure 100 formed on the substrate 10, and the back surface of the support member (membrane) 215 is provided on the back surface. Etching stopper films (for example, Si ₃ N ₄ films) 130b to 130d are provided. The etching stopper films 130a to 130d are formed by removing a layer not to be etched in the step of removing the sacrificial layer (not shown in FIG. 1, reference numeral 101 in FIG. 3) in order to form the cavity 102. Play a role in preventing. However, the etching stopper film may be unnecessary depending on the material constituting the support member (membrane) 215.

  In addition, the pyroelectric capacitor 230 included in the element structure 160 is supported on the cavity 102 by a support member (membrane) 215 that is also a component of the element structure 160.

  Here, the support member (membrane) 215 can be formed, for example, by patterning a three-layer film of silicon oxide film (SiO) / silicon nitride film (SiN) / silicon oxide film (SiO) (see FIG. However, this is an example, and the present invention is not limited to this). The support member (membrane) 215 needs to stably support the pyroelectric capacitor 230, and thus the total thickness of the support member (membrane) 215 has a thickness that satisfies the required mechanical strength.

  An alignment film (not shown) is formed on the surface of the support member (membrane) 215, and the pyroelectric capacitor 230 is formed on the alignment film. As described above, the pyroelectric capacitor 230 includes a lower electrode (first electrode) 234, a pyroelectric material layer (for example, a PZT layer as a pyroelectric body: a lead zirconate titanate layer) 232 formed on the lower electrode, And an upper electrode (second electrode) 236 formed on the pyroelectric material layer 232.

Both the lower electrode (first electrode) 234 and the upper electrode (second electrode) 236 can be formed, for example, by laminating three layers of metal films. For example, a three-layer structure of iridium (Ir), iridium oxide (IrOx), and platinum (Pt) formed by, for example, sputtering in order from a position far from the pyroelectric material layer (PZT layer) 232 can be formed. As the pyroelectric material layer 232, for example, PZT (Pb (Zi, Ti) O ₃ : lead zirconate titanate) can be used as described above.

  When heat is transferred to the pyroelectric material layer (pyroelectric body), as a result, a change in the amount of electric polarization occurs in the pyroelectric material layer 232 due to the pyroelectric effect (pyroelectronic effect). By detecting the current accompanying the change in the amount of electric polarization, the intensity of the incident light can be detected.

  The pyroelectric material layer 232 can be formed by, for example, a sputtering method or an MOCVD method. The film thickness of the lower electrode (first electrode) 234 and the upper electrode (second electrode) 236 is, for example, about 0.4 μm, and the film thickness of the pyroelectric material layer 232 is, for example, about 0.1 μm.

  The pyroelectric capacitor 230 is covered with the insulating layer 250 and the first light absorption layer 270. A first contact hole 252 is provided in the insulating layer 250. The first contact hole 252 is used to connect the electrode 226 for the upper electrode (second electrode) 236 to the upper electrode (second electrode) 236.

  A second contact hole 254 is provided in the first light absorption layer 270 (and the insulating layer 250). The second contact hole 254 is provided through the first light absorption layer 270 and the insulating layer 250. The second contact hole 254 is used to connect the heat transfer member 260 to the upper electrode 236 of the pyroelectric capacitor 230. That is, the material constituting the heat transfer member 260 (for example, aluminum nitride (AlN) or aluminum oxide (AlOx)) is filled in the second contact hole 254 (the filled portion is denoted by reference numeral 228 in the figure). As a result, the connection portion CN in the heat transfer member 260 is formed.

  The heat transfer member 260 includes a heat collection portion FL that is a portion extending on the first light absorption layer 270 whose surface is planarized, and the heat collection portion FL as an upper electrode (second electrode) in the pyroelectric capacitor 230. Electrode) 236, which is a portion connected to 236.

  Here, the heat collection part FL of the heat transfer member 260 plays a role of collecting heat generated in a wide area and transmitting it to the pyroelectric capacitor 230 which is a heat detection element, for example. Note that the heat collection part FL may be formed in a form having a flat surface on the flattened first light absorption layer 270, for example. In this case, the "heat collection part" In other words, “a flat plate portion or a flat portion”.

  As described above, the heat transfer member 260 can be made of a material having high thermal conductivity and light transmittance (for example, semi-transparency) with respect to light in a desired wavelength band. AlN) or aluminum oxide (AlOx) can be used. Note that the material in the heat collecting portion FL and the material 228 in the connection portion CN (for example, the material of the contact plug embedded in the contact hole 254) can be different.

  Further, as shown in FIG. 1B (and FIG. 1A), the lateral width of the connection portion CN is W0, the lateral width of the pyroelectric material layer 232 is W1, and the heat collecting portion FL of the heat transfer member 260 is When the lateral width is W2, the relationship of W0 <W1 <W2 is established. The horizontal width of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 is set to W2. That is, as shown in FIG. 1A, the outer periphery (outer edge) of the heat transfer member 260 and the outer periphery (outer edge) of the lower electrode (first electrode) 234 substantially coincide with each other in plan view.

  As shown in FIG. 1B, the surface of the extended portion (RX) of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 when the first wavelength is λ1 and the second wavelength is λ2. And a distance H1 between the second light absorption layer 272 and the upper surface of the second light absorption layer 272 is set to n · (λ1 / 4) (n is an integer of 1 or more). Thus, the first optical resonator (λ1 / 4 optical resonator) is configured between the surface of the extended portion (RX) of the lower electrode (first electrode) 234 and the upper surface of the second light absorption layer 272. Has been. Since the film thickness of the lower electrode (first electrode) 234 is sufficiently thin, there is no particular problem even if the film thickness is ignored. Therefore, the film thickness H2 of the first light absorption layer 270 and the second light absorption layer 272 The total film thickness of the film thickness H3 can also be regarded as the distance H1 described above.

  The distance H3 between the lower surface of the second light absorption layer 272 and the upper surface of the second light absorption layer 272 (that is, the film thickness H3 of the second light absorption layer 272) is n · (λ2 / 4). Is set. Thus, a second optical resonator (λ2 / 4 optical resonator) is configured between the lower surface of the second light absorption layer 272 and the upper surface of the second light absorption layer 272. Since the film thickness of the heat collecting portion FL in the heat transfer member 260 is sufficiently thin, there is no particular problem even if the film thickness is ignored. Therefore, the film thickness H3 of the second light absorption layer 272 is set to the second optical resonator. It can be seen that The effect of configuring the first optical resonator and the second optical resonator will be described later. Further, the heat collecting part FL of the heat transfer member 260 and the light reflecting layer 235 are arranged in parallel to each other. Accordingly, the parallelism between the upper surface of the light reflection layer 235 and the upper surface of the second light absorption layer 272 is maintained.

(Layout configuration)
Next, a layout configuration will be described with reference to FIG. As shown in FIG. 1A, the support member (membrane) 215 includes a placement unit 210 on which the pyroelectric capacitor 230 is placed, and the placement unit 210 on the cavity (heat separation cavity) 102. Two arms, that is, a first arm portion 212a and a second arm portion 212b. The pyroelectric capacitor 230 is formed on the mounting portion 210 in the support member (membrane) 215. In addition, as described above, the element structure 160 includes the support member (membrane) 215, the pyroelectric capacitor 230, the first light absorption layer 270, the heat transfer member 260, and the second light absorption layer 272.

  As described above, the first arm portion 212a and the second arm portion 212b are formed by patterning, for example, a three-layer film of silicon oxide film (SiO) / silicon nitride film (SiN) / silicon oxide film (SiO). It can be formed by processing into an elongated shape. The elongate shape is used to increase heat resistance and suppress heat radiation (heat escape) from the pyroelectric capacitor 230.

  A wide tip 232a of the first arm portion 212a is supported on the cavity 102 by a first post 104a (a circular member shown in a broken line in FIG. 1A). Further, on the first arm portion 212a, one end (reference numeral 228) is connected to the lower electrode (first electrode) 234 of the pyroelectric capacitor 230, and the other end 231a is connected to the first post 104a. 229a is formed.

  For example, the first post 104a is provided between the structure 100 including the insulating layer shown in FIG. 1B and the distal end portion 232a of the first arm portion 212a. The first post 104a is, for example, a multi-layered wiring structure that is selectively formed in the cavity 102 and processed into a columnar shape (interlayer insulating layer, pyroelectric capacitor 230, transistor provided on the underlying silicon substrate 10, etc. And a conductive layer that constitutes a wiring for connecting the element.

  Similarly, the second arm portion 212b is supported on the cavity portion 102 by the second post 104b (a circular member in a plan view shown by a broken line in FIG. 1A). The wide end portion 232b of the second arm portion 212b is supported on the cavity portion 102 by the second post 104b (a circular member shown in a broken line in FIG. 1A). Also, on the second arm portion 212b, one end (reference numeral 226) is connected to the upper electrode (second electrode) 236 of the pyroelectric capacitor 230, and the other end 231b is connected to the second post 104b. 229b is formed.

  The second post 104b is provided between the structure 100 including the insulating layer shown in FIG. 1B and the distal end portion 232b of the second arm portion 212b. Further, the second post 104b is, for example, a columnar multilayer wiring structure (an interlayer insulating layer, a pyroelectric capacitor 230, and a transistor provided on the underlying silicon substrate 10 that is selectively formed in the cavity 102. And a conductive layer that constitutes a wiring for connecting elements such as the like.

  In the example shown in FIG. 1A, the element structure 160 including the support member 215 and the pyroelectric capacitor 230 is held in the cavity 102 using the first post 104a and the second post 104b. This configuration is effective when a plurality of pyroelectric capacitors 230 as heat detection elements are arranged at high density in the common cavity 102 (that is, when an array of heat detection elements is formed). However, this configuration is an example, and the present invention is not limited to this. For example, as shown in the example shown in FIG. 6, one cavity 102 is formed for each heat detection element (pyroelectric capacitor) 230, and the support member (membrane) 215 is an insulating layer around the cavity 102. You may make it support in the structure 100 containing these.

  In FIG. 1A, the pyroelectric capacitor 230 is disposed in the central region of the mounting portion 210 in the support member 215, and the pyroelectric capacitor 230 has a substantially square shape in plan view. Further, as shown in FIG. 1A, the lateral width of the connection portion CN of the heat transfer member 260 is W0, the lateral width of the pyroelectric material layer 232 in the pyroelectric capacitor 230 is W1, and the heat collecting portion of the heat transfer member 260 When the width of FL and the width of the lower electrode (first electrode) 234 are W2, the relationship of W0 <W1 <W2 is established.

  Therefore, the area of the heat collecting portion FL of the heat transfer member 260 in a plan view (a plan view seen from a direction perpendicular to the surface of the substrate 10, more specifically a plan view seen from the vertical upper direction) It is larger than the area of CN. Further, the area of the heat collecting part FL of the heat transfer member 260 in plan view is larger than the area of the pyroelectric capacitor 230.

  Further, as shown in FIG. 1A, the first light absorption layer 270 and the second light absorption layer 272 are on the support member 215 in a plan view, and the pyroelectric capacitor 230 which is a heat detection element. It is formed around. Therefore, the heat generated in a wide range of the first light absorption layer 270 and the second light absorption layer 272 passes directly to the pyroelectric capacitor 230 or via the heat transfer member 260 having a large area covering the wide range. Indirect and efficient.

  That is, heat generated in a wide range of the first light absorption layer 270 and the second light absorption layer 272 collects in the pyroelectric capacitor 230 in all directions (that is, from all directions). Here, the pyroelectric capacitor 230 is located below the center of the substantially square heat transfer member 260 in plan view. Therefore, the heat collected from all directions via the heat transfer member 260 is transmitted to the upper electrode (second electrode) 236 of the pyroelectric capacitor 230 through the connection portion CN at the shortest distance. Therefore, a large amount of heat is efficiently collected from a wide range, and the heat is transmitted to the upper electrode (second electrode) 236 of the pyroelectric capacitor 230 while minimizing the loss at the shortest distance. can do. Therefore, the light detection sensitivity of the thermal detector 200 can be further increased. Moreover, the response speed of the thermal detector is further improved.

  Further, as described above, the extension portion RX of the lower electrode (first electrode) 234 in the pyroelectric capacitor 230 also has an effect of transferring heat, and thus, for example, occurs in a wide region of the first light absorption layer 270. The collected heat is collected in the pyroelectric material layer 232 from all directions via the extended portion RX. In addition, an effect of efficiently transferring heat generated at a location far from the pyroelectric material layer 232 in the first light absorption layer 270 to the pyroelectric material layer 232 can be obtained.

  Moreover, in this embodiment, since heat is generated by the two light absorption films 270 and 272, the absorption efficiency is increased. In addition, heat can be directly transferred to the heat detection element 230 via the first light absorption layer 270. Therefore, compared with the infrared detection element described in Patent Document 1 and the infrared solid-state imaging element described in Patent Document 2, the detection sensitivity of the thermal detector can be further improved. In the present embodiment, the heat detection element 230 is connected to the heat transfer member 260. Therefore, the response speed is as high as the infrared detection element described in Patent Document 1. In the present embodiment, since the heat transfer member 260 is directly connected to the heat detection element 230, a higher response speed can be obtained as compared with the infrared solid-state imaging element described in Patent Document 2.

(About the operation of the thermal detector)
The thermal photodetector (thermal photodetector) 200 according to the present embodiment shown in FIGS. 1A and 1B operates as follows.

  That is, a part of light (for example, infrared rays) incident on the thermal detector 200 is first absorbed by the second light absorption layer 272 and the others reach the heat transfer member 260 without being absorbed. The heat transfer member 260 is light transmissive with respect to light in a wavelength band in which the thermal photodetector 200 has detection sensitivity, and is, for example, semi-transmissive with infrared light. In the heat transfer member 260, for example, part of the reached light is reflected and the other is transmitted through the heat transfer member 260. A part of the light transmitted through the heat transfer member 260 is absorbed by the first light absorption layer 270, and other light of the pyroelectric capacitor 230 as a heat detection element formed on the support member (membrane) 215. It reaches the surface of the extended portion RX of the lower electrode (first electrode) 234 and the surface of the support member (membrane) 215.

  Most (for example, most) of the light incident on the extended portion RX of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 is reflected by the surface thereof, and the first light absorption layer 270 and the second light absorption. By being absorbed by at least one of the layers 272, heat is generated in the first light absorption layer 270 or the second light absorption layer 272. That is, the presence of the extended portion RX of the lower electrode (first electrode) 234 reduces incident light that escapes downward through the support member (membrane) 215, and thus more. The incident light can be converted into heat, and the light can be effectively used.

Further, the light reflected by the surface of the support member (membrane) 215 is also absorbed by at least one of the first light absorption layer 270 and the second light absorption layer 272, and thereby, the first light absorption layer or the second light absorption layer. Heat is generated at. For example, when the first light absorption layer 270 is composed of a SiO ₂ layer (refractive index: 1.45) and the support member (membrane) 215 is composed of a SiN film (refractive index 2.0), the first light Since the refractive index of the film constituting the support member (membrane) 215 (that is, the refractive index of the support member 215) is larger than the refractive index of the absorption layer 270, the light that has reached the support member (membrane) 215 Most of the light is reflected on the surface of the support member (membrane) 215.

  Further, as a constituent element of the support member (membrane) 215, for example, a metal film such as a titanium (Ti) film is provided (particularly preferably provided on a surface where light is reflected), and the surface of the support member (membrane) 215 is provided. Increasing the reflectance of light is also effective. The light reflected by the surface of the support member (membrane) 215 is absorbed by the first light absorption layer 270 and the second light absorption layer 272.

  Generation of heat in the first light absorption layer 270 and the second light absorption layer 272 when incident light behaves as described above, and the generated heat to the pyroelectric capacitor 230 that is a heat detection element. Is transmitted as follows, for example.

  That is, a part of the light incident on the thermal detector 200 is first absorbed by the second light absorption layer 272 and heat is generated in the second light absorption layer 272. Further, the light reflected by the heat transfer member 260 is absorbed by the second light absorption layer 272, whereby heat is generated in the second light absorption layer 272.

  In addition, a part of the light transmitted (passed) through the heat transfer member 260 is absorbed by the first light absorption layer 270 to generate heat. Other light reaches the surface of the extending portion RX of the lower electrode (first electrode) of the pyroelectric capacitor 230 and the surface of the support member (membrane) 215.

  As described above, most (for example, most) of light incident on the surface of the extension portion RX of the lower electrode (first electrode) is reflected, and the reflected light is reflected by the first light absorption layer 270 and the second light. Absorbed by the absorption layer 272. Therefore, incident light can be converted into heat by using it without waste.

  In addition, since the extension portion RX of the lower electrode (first electrode) of the pyroelectric capacitor 230 has a heat collecting effect, the pyroelectric material layer efficiently absorbs heat generated in a wide range of the first light absorption layer 270. 232.

  Further, a part of the light reaching the surface of the support member (membrane) 215 is also reflected and absorbed by the first light absorption layer 270 and the second light absorption layer 272. Effective use is planned.

  The heat generated in the second light absorption layer 272 is efficiently transferred to the pyroelectric capacitor 230, which is a heat detection element, via the heat transfer member 260, and the heat generated in the first light absorption layer 270 is , And efficiently transmitted to the pyroelectric capacitor 230 via the heat transfer member 260.

  That is, the heat collection part of the heat transfer member 260 is formed so as to cover the heat detection element 230 widely, and therefore, most of the heat generated by the first light absorption layer 270 and the second light absorption layer 272 is reduced. Regardless of the place of the occurrence, it can be efficiently transmitted to the heat detection element. For example, even heat generated at a location away from the heat detection element 230 can be efficiently transferred to the pyroelectric capacitor 230 that is a heat detection element via the heat transfer member 260 having high thermal conductivity. it can.

  Moreover, since the heat collection part FL of the heat transfer member 260 and the pyroelectric capacitor 230 are connected by the connection part CN of the heat transfer member 260, the heat collection part FL is transmitted via the heat collection part FL of the heat transfer member 260. The generated heat can be directly transmitted to the pyroelectric capacitor 230 via the connection portion CN. Further, since the pyroelectric capacitor 230 as a heat detection element is located below (directly below) the heat transfer member 260 (provided at a position overlapping in plan view), for example, the center of the heat transfer member 260 in plan view Can be connected to the pyroelectric capacitor 230 in the shortest time. Therefore, the loss accompanying heat transfer can be reduced, and an increase in the occupied area can be suppressed.

  Thus, according to the thermal detector (here, pyroelectric infrared detector) described in FIGS. 1 (A) and 1 (B), two layers (multiple layers) of light absorption layers 270, The heat generated in a wide range in 272 can be efficiently transferred to the pyroelectric capacitor 230, which is a heat detection element, so that the light detection sensitivity of a small thermal detector (pyroelectric infrared detector) can be increased. It can be greatly improved. In addition, since the time required for heat transfer is shortened, the response speed of the thermal detector (pyroelectric infrared detector) can be increased.

  Further, the detection efficiency of the thermal detector is increased by the light reflection effect and the heat collection effect by the extension portion RX of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230.

  In the thermal detector (pyroelectric infrared detector) shown in FIGS. 1A and 1B, the first light absorption layer 270 and the second light absorption layer 272 are formed of the support member 215. (On the mounting part 210), it is formed around the pyroelectric capacitor 230 which is a heat detection element in a plan view. Accordingly, heat generated in a wide range of the first light absorption layer 270 and the second light absorption layer 272 is directly or indirectly via the heat transfer member 260 to the pyroelectric capacitor 230 that is a heat detection element. Are transmitted very efficiently. Therefore, the photodetection sensitivity of the thermal photodetector (pyroelectric infrared detector) can be further increased. Moreover, the response speed of the thermal detector (pyroelectric infrared detector) is further improved.

  Further, as described above, in the thermal detector (pyroelectric infrared detector) described in FIGS. 1A and 1B, the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 is not affected. A first optical resonator for the first wavelength λ1 is formed between the surface of the extending portion RX and the upper surface of the second light absorption layer 272, and the lower surface of the second light absorption layer 272 and the second A second optical resonator for the second wavelength λ2 different from the first wavelength λ1 is formed between the upper surface of the light absorption layer 272. That is, by adjusting the film thicknesses of the first light absorption layer 270 and the second light absorption layer 272, two optical resonators having different resonance wavelengths are configured.

  As described above, the light reflected by the extension RX of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 is absorbed by at least one of the first light absorption layer 270 and the second light absorption layer 272. At this time, by configuring the first optical resonator, the effective absorption rate in each light absorption layer can be increased.

  The first optical resonator can be, for example, a so-called λ / 4 optical resonator. That is, when the first wavelength is λ1, the distance H1 between the surface of the extended portion RX of the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 and the upper surface of the second light absorption layer 272 (lower electrode 234). Can be ignored, the total thickness H1 of the first light absorption layer 270 and the second light absorption layer 272) satisfies the relationship of n · (λ1 / 4) (n is an integer of 1 or more). Thus, the film thicknesses of the first light absorption layer 270 and the second light absorption layer 272 are adjusted. As a result, the incident light having the wavelength λ 1 and the light having the wavelength λ 1 reflected by the surface of the extending portion RX of the lower electrode 234 are canceled by mutual interference, and the first light absorbing layer 270 and the second light absorbing layer 272 Effective absorption rate increases.

  In addition, since the extension portion RX of the lower electrode 234 is made of a material having a high light reflectivity, most of the incident light can be reflected upward, and light resonance easily occurs.

  Further, the light reflected by the surface of the support member (membrane) 215 also causes mutual interference with the incident light, so that resonance in the first optical resonator is likely to occur.

  Further, as described above, the light reflected by the heat transfer member 260 is absorbed by the second light absorption layer 272. At this time, the second optical resonator constitutes the effective light in the second light absorption layer 272. Absorption rate can be increased. The second optical resonator can be, for example, a so-called λ / 4 optical resonator.

  That is, when the second wavelength is λ2, the distance between the lower surface of the second light absorption layer 272 and the upper surface of the second light absorption layer 272 (that is, the film thickness of the second light absorption layer) is n · ( By setting λ2 / 4), the second optical resonator can be configured. As a result, the incident light having the wavelength λ2 and the light having the wavelength λ2 reflected by the lower surface of the second light absorption layer (the interface between the first light absorption layer 270 and the second light absorption layer 272) are canceled by mutual interference. The effective absorption rate in the second light absorption layer 272 can be increased.

  In addition, since two optical resonators constitute resonance peaks at two different wavelengths, the peaks are combined and the wavelength band in which the thermal detector has detection sensitivity is expanded. That is, the wavelength band (wavelength width) of light that can be detected by the thermal detector can be expanded.

(About preferred examples of heat transfer members)
Next, a preferable example of the heat transfer member (heat transfer layer) will be described. As described above, the thermal detector 200 of the present embodiment employs a structure in which the heat collection part FL in the heat transfer member 260 is sandwiched between the first light absorption layer 270 and the second light absorption layer 272. In addition, the heat collection part FL of the heat transfer member 260 preferably has a large area in plan view so that heat generated at a position far from the pyroelectric capacitor 230 which is a heat detection element can also be collected. Under this circumstance, in order to absorb the light incident from above the thermal detector 200 by both the first light absorption layer 270 and the second light absorption layer 272, the heat transfer member 260 has a desired wavelength. It is preferable to use a light-transmitting material that transmits light in at least a part of the wavelength region in the band.

That is, the heat transfer member 260 is preferably made of a material having good heat transfer and heat conductivity. The heat transfer member 260 can be composed of, for example, aluminum nitride (AlN) or aluminum oxide (AlOx). Aluminum oxide is also called alumina, and for example, Al ₂ O ₃ can be used.

  2A and 2B are diagrams showing examples of spectral characteristics (light reflection characteristics and light transmission characteristics) of the alumina plate in the far-infrared wavelength region, and two optical resonators are configured. It is a figure which shows an example of the detection sensitivity of a thermal type photodetector in the case where it is.

  The far-infrared wavelength range is not particularly strict, but generally the far-infrared wavelength range is about 4 μm to 1000 μm. Infrared rays are always emitted from objects, and infrared rays are emitted more intensely at higher temperature objects. The wavelength of the peak of radiation is inversely proportional to the temperature. For example, the peak wavelength of infrared rays emitted from an object at room temperature of 20 ° C. is about 10 μm.

  FIG. 2A shows the reflectance and transmittance of the alumina plate in the wavelength range of 4 μm to 24 μm. The horizontal axis represents wavelength (μm), and the vertical axis represents relative intensity (arbitray unit: a.u.). In FIG. 2, the characteristic line Q1 indicating the transmittance is indicated by a one-dot chain line, the characteristic line Q2 indicating the reflectance is indicated by a solid line, and the characteristic line Q3 indicating the result of adding the transmittance and the reflectance is Shown in dotted lines.

  As shown in FIG. 2A, the reflectance varies considerably depending on the wavelength. On the other hand, the transmittance is almost zero in the wavelength region of 6 μm or more.

  Here, attention is paid to the transmittance and reflectance for light having a wavelength of 4 μm. The transmittance is 0.2 (that is, 20%), and the reflectance is 0.5 (that is, 50%). Further, attention is paid to the transmittance and reflectance with respect to light having a wavelength of 12 μm. The transmittance is almost 0 (0%), and the reflectance is about 0.43 (43%).

  Considering such spectral characteristics, for example, the first wavelength λ1 can be set to 4 μm and the second wavelength λ2 can be set to 12 μm. In this case, the film thickness of the first light absorption film 270 may be 3 μm, for example, and the film thickness of the second light absorption film 272 may be 1 μm, for example.

  When alumina having the spectral characteristics shown in FIG. 2A is used as the material of the heat transfer member 260, about 50% of the light having the wavelength of the first wavelength λ1 (= 4 μm) included in the incident light is About 20% of the light having the wavelength of the first wavelength λ1 (= 4 μm) reflected by the heat transfer member 260 made of alumina passes through the heat transfer member 260.

  The light of wavelength λ1 that has passed through the heat transfer member 260 reaches the support member (membrane) 215, is reflected on the surface thereof, rises again toward the second light absorption layer 272, and one of the rising light. The portion is reflected by the upper surface of the second light absorption layer 272 (the interface between the atmosphere and the first light absorption layer 272) and travels downward again. In this way, resonance at the wavelength λ1 can be generated in the first optical resonator.

  Further, about 43% of the light of wavelength λ2 (= 12 μm) included in the incident light is reflected by the heat transfer member 260 (almost no transmitted light is generated), and the reflected light passes through the second light absorption layer 272. A part of the rising light is reflected by the upper surface of the second light absorption layer 272 (the interface between the atmosphere and the second light absorption layer 272) and travels downward again. In this manner, resonance at the wavelength λ2 can be generated in the second optical resonator.

  As described above, the effective absorption rate of light in the first light absorption layer 270 and the second light absorption layer 272 can be increased by causing optical resonance.

  In addition, as shown in FIG. 2B, the wavelength band having the detection sensitivity of the thermal detector can be expanded. FIG. 2B is a diagram illustrating an example of the detection sensitivity of the thermal photodetector when two optical resonators are configured. In the example shown in FIG. 2B, the resonance peak P1 due to the first optical resonator appears at the wavelength λ1 (for example, λ1 = 4 μm), and the resonance peak P2 due to the second optical resonator is the wavelength λ2 (for example, λ2 = 12 μm). ). By combining these peak characteristics, the detection sensitivity P3 of the thermal photodetector 200 is expanded. That is, the thermal detector 200 having detection sensitivity in a wide wavelength range is realized. The same effect can be obtained when aluminum nitride (AlN) is used as the material of the heat transfer member 260.

  Thus, according to the thermal detector of the present embodiment, heat generated at a location far from the heat detection element is detected via the heat collecting portion FL of the heat transfer member (heat transfer layer) 260. It can be collected at high speed and efficiently in the pyroelectric capacitor 230 as an element. Further, by using mutual interference of light wavelengths (using light resonance), the effective light absorption efficiency in the first light absorption layer 270 and the second light absorption layer 272 can be increased, and The wavelength band in which the thermal detector has detection sensitivity can be widened.

(About manufacturing method of thermal detector)
Hereinafter, the manufacturing method of the thermal detector will be described with reference to FIGS. First, FIGS. 3A to 3E are referred to. FIG. 3A to FIG. 3E are diagrams showing main steps until the first light absorption layer is formed in the method of manufacturing a thermal detector.

In the step shown in FIG. 3A, a silicon substrate (which may have an element such as a transistor) is prepared, and a structure (for example, a multilayer wiring structure) including an insulating layer on the silicon substrate 10 is prepared. 100 is formed. An etching stopper film 130a is formed on the structure 100 including the insulating layer, and a sacrificial layer (for example, SiO ₂ layer) 101 is further formed.

  In the step of FIG. 3B, an etching stopper film 130 b is formed on the sacrificial layer 101. Next, a thick film (for example, a thick film composed of a laminated film of three layers) to be the support member (membrane) 215 is formed.

  In the step of FIG. 3C, a lower electrode (first electrode) 234, a pyroelectric material layer (PZT layer) 232 and an upper electrode (second electrode) 236 are laminated on the support member (membrane) 215, A pyroelectric capacitor 230 is formed as a heat detection element. At this time, the lower electrode (first electrode) 234 of the pyroelectric capacitor 230 is formed to have an extending portion RX that extends on the support member (membrane) 215.

  As a method for forming the pyroelectric capacitor 230, for example, an atomic layer CVD method can be used. Next, an insulating layer 250 is formed so as to cover the pyroelectric capacitor 230. The insulating layer 250 can be formed by, for example, a CVD method. Subsequently, the insulating layer 250 is patterned.

  3E, a first contact hole 252 is formed in the insulating layer 250 covering the pyroelectric capacitor 230, a metal material layer is subsequently deposited, and then the metal material layer is patterned. Thus, an electrode (and wiring) 226 connected to the upper electrode (second electrode) 236 is formed. In addition, in the process of FIG. 3E, an electrode connected to the lower electrode (first electrode) and wiring (not shown) are also formed.

In the step of FIG. 3E, a first light absorption layer (SiO ₂ layer or the like) 270 is formed by a CVD method. Next, the surface is planarized by, for example, CMP (Chemical Mechanical Polishing).

  FIG. 4A to FIG. 4C are diagrams showing main steps until the first light absorption layer and the second light absorption layer are patterned in the method for manufacturing a thermal detector. In the step of FIG. 4A, the second contact hole 254 is formed in the first light absorption layer 270. Subsequently, a heat transfer member (heat transfer layer) 260 is formed by depositing and patterning a material having high thermal conductivity and light transmittance, such as aluminum oxide (alumina: AlOx) and aluminum nitride (AlN). To do. The heat transfer member 260 has a heat collection part FL and a connection part CN. The second contact hole 254 is filled with a material such as alumina. The connection portion CN is constituted by the portion 238 filled with a material such as alumina. The heat collection part FL of the heat transfer member 260 and the light reflection layer 235 are arranged in parallel to each other.

In the step of FIG. 4B, a material layer (such as a SiO ₂ layer) to be a second light absorption layer is deposited on the first light absorption layer 270 and then patterned. Thereby, the second light absorption layer 272 is formed. In the step of FIG. 4C, the first light absorption layer 270 is patterned.

  FIG. 5A and FIG. 5B are diagrams showing the main steps until the thermal photodetector is completed in the manufacturing method of the thermal photodetector. In the step of FIG. 5A, the support member (membrane) 215 is patterned. Thereby, the mounting part 210, the 1st arm part 212a, and the 2nd arm part 212b are formed. In FIG. 5A, a reference numeral OP is attached to a portion (opening) removed by patterning.

  In the step of FIG. 5B, the sacrificial layer 101 is selectively removed by wet etching, for example. As a result, a cavity (thermal separation cavity) 102 is formed. The mounting portion 210 of the support member 215 is separated from the base portion (consisting of the substrate 10, the structure 100 including the insulating layer and the etching stopper film 130 a) by the cavity portion 102. Therefore, heat dissipation via the support member 215 is suppressed. In this way, a thermal detector is completed.

(Second Embodiment)
FIG. 6 is a diagram showing another example of a thermal detector. In the thermal detector 200 shown in FIG. 6, a cavity 102 is formed for each thermal detection element, and the support member (membrane) 215 is formed by a structure (a part of the base) around the cavity 102. Supported. In addition, a circuit component (here, a MOS transistor) is formed in a region of the substrate that overlaps the heat detection element in plan view, and the MOS transistor is a heat detection element via a multilayer wiring. Connected to pyroelectric capacitor 230. In the example of FIG. 6, the heat transfer member 260 is also used as wiring.

  That is, a source layer (S) and a drain (D) layer are formed on the substrate (silicon substrate) 10, and a gate insulating film INS and a gate electrode (for example, a polysilicon gate electrode) G are formed on the substrate 10. As a result, a MOS transistor which is a circuit component is formed.

  A structure 100 including an insulating layer is formed on the substrate 10. A base (base) is constituted by the substrate 10 and the structure 100 including the insulating layer.

  The structure 100 including an insulating layer is formed of a multilayer structure, and more specifically, a multilayer wiring structure. The multilayer wiring structure includes a first insulating layer 100a, a second insulating layer 100b, a third insulating layer 100c, a first contact plug CP1, a first layer wiring M1, a second contact plug CP2, and a second contact plug CP2. A second layer wiring M2 and a third contact plug CP3 are included. A part of the third insulating layer 100c is selectively removed to form a cavity (thermal separation cavity) 102.

  A pyroelectric capacitor 230 serving as a heat detection element is formed on the mounting portion 210 of the support member (membrane) 215. The heat transfer member 260 is formed between the first light absorption layer 270 and the second light absorption layer 272.

  A support member (membrane) 215, a pyroelectric capacitor 230, a first light absorption layer 270, a second light absorption layer 272, a heat transfer member 260, a fourth contact plug CP4, a third layer wiring M3, The element structure 160 is configured by the fifth contact plug CP5. As described above, the heat transfer member 260 also serves as part of the wiring that connects the pyroelectric capacitor 230, which is a heat detection element, to another element (here, a CMOS transistor formed on the substrate 10).

  That is, as described above, the heat transfer member 260 can be made of a metal compound such as AlN or AlOx, for example. However, since the metal-based material has good electrical conduction, the heat transfer member 260 Can also be used as wiring (including part of the wiring) for connecting the heat detection element to other elements. By using the heat transfer member 260 as a wiring, it is not necessary to provide a wiring separately, and the manufacturing process can be simplified.

(Third embodiment)
FIG. 7 is a circuit diagram showing an example of a circuit configuration of a thermal photodetection device (thermal photodetection array). In the example of FIG. 7, a plurality of photodetection cells (that is, thermal photodetectors 200a to 200d and the like) are two-dimensionally arranged. Scan lines (W1a, W1b, etc.) and data lines (D1a, D1b, etc.) are provided in order to select one photodetection cell from among a plurality of photodetection cells (thermal detectors 200a-200d, etc.). It has been.

  The thermal photodetector 200a as the first photodetector cell includes a piezoelectric capacitor ZC as the thermal photodetector 5 and an element selection transistor M1a. The potential relationship between the two electrodes of the piezoelectric capacitor ZC can be reversed by switching the potential applied to PDr1 (this potential reversal eliminates the need to provide a mechanical chopper). The other light detection cells have the same configuration.

  The potential of the data line D1a can be initialized by turning on the reset transistor M2. When reading the detection signal, the read transistor M3 is turned on. A current generated by the pyroelectric effect is converted into a voltage by the I / V conversion circuit 510, amplified by the amplifier 600, and converted into digital data by the A / D converter 700.

  In this embodiment, a plurality of thermal detectors are two-dimensionally arranged (for example, arranged in an array along each of two orthogonal axes (X axis and Y axis)). A device (thermal optical array sensor) is realized.

(Fourth embodiment)
FIG. 8 is a diagram illustrating an example of a configuration of an electronic device. Examples of the electronic device include an infrared sensor device, a thermography device, a vehicle-mounted night camera, a monitoring camera, and the like.

  As illustrated in FIG. 8, the electronic apparatus includes an optical system 400, a sensor device 410 (corresponding to the thermal detector 200 in the above-described embodiment), an image processing unit 420, a processing unit 430, and a storage Part 440, operation part 450, and display part 460. Note that the electronic apparatus of the present embodiment is not limited to the configuration in FIG. 8, and some of the components (for example, the optical system, the operation unit, the display unit, etc.) are omitted, or other components are added. Various modifications of the above are possible.

  The optical system 400 includes, for example, one or a plurality of lenses and a driving unit that drives these lenses. Then, an object image is formed on the sensor device 410. If necessary, focus adjustment is also performed.

  The sensor device 410 is configured by two-dimensionally arranging the photodetectors of the present embodiment described above, and is provided with a plurality of row lines (scanning lines (or word lines)) and a plurality of column lines (data lines). In addition to the two-dimensionally arranged photodetectors, the sensor device 410 includes a row selection circuit (row driver), a readout circuit that reads data from the photodetectors via column lines, an A / D converter, and the like. Can be included. By sequentially reading out data from each of the two-dimensionally arranged photodetectors, an object image can be captured.

  The image processing unit 420 performs various image processing such as image correction processing based on digital image data (pixel data) from the sensor device 410. The image processing unit 420 corresponds to a control unit that processes the output of the sensor device 410 (the thermal detector 200). The processing unit 430 performs overall control of the electronic device and each block in the electronic device. The processing unit 430 is realized by a CPU or the like, for example. The storage unit 440 stores various types of information, and functions as a work area for the processing unit 430 and the image processing unit 420, for example. The operation unit 450 serves as an interface for the user to operate the electronic device, and is realized by various buttons or a GUI (Graphical User Interface) screen, for example.

  The display unit 460 displays, for example, an image acquired by the sensor device 410, a GUI screen, and the like, and is realized by various displays such as a liquid crystal display and an organic EL display.

  As described above, the thermal detector for one cell is used as a sensor such as an infrared sensor, and the sensor device (thermal optical detector) is arranged by two-dimensionally arranging the thermal detector for one cell in two orthogonal axes. Detection device) 410, which can provide a heat (light) distribution image. The sensor device 410 can be used to configure an electronic device such as a thermography, a vehicle-mounted night vision camera, or a surveillance camera.

  As described above, the thermal detector according to the present invention has high light detection sensitivity. Therefore, the performance of an electronic device equipped with this thermal detector is enhanced.

  FIG. 9 is a diagram illustrating another example of the configuration of the electronic device. The electronic apparatus 800 in FIG. 9 includes a sensor unit 600 on which the thermal detector 200 and the acceleration detection element 503 are mounted. The sensor unit 600 can further be equipped with a gyro sensor or the like. The sensor unit 600 can measure different types of physical quantities. Each detection signal output from the sensor unit 600 is processed by the CPU 700. The CPU 700 corresponds to a control unit that processes the output of the thermal detector 200.

  As described above, according to at least one embodiment of the present invention, for example, the detection sensitivity of a thermal detector can be significantly improved.

  Although several embodiments have been described above, it is easily understood by those skilled in the art that many modifications can be made without substantially departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be 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 in any part of the specification or the drawings.

  In the above-described embodiment, a pyroelectric capacitor is used as the heat detection element. However, instead of this, a thermopile element or a bolometer element can be used.

10 substrate (eg silicon substrate),
100 a structure including an insulating layer (for example, a multilayer structure including at least one interlayer insulating layer), 102 cavity (thermal separation cavity),
104a, 104b 1st post and 2nd post,
130a to 130d Etching stopper film 200 Thermal detector, 210 Placement part of support member,
212 (212a, 212b) arm portions (first arm portion, second arm portion) of support member, 215 support member (membrane),
229a, 229b wiring (wiring formed on the arm portion),
226 electrode (wiring),
228 portion of the material constituting the heat transfer member filled in the second contact hole;
230 Pyroelectric capacitor as a heat detection element,
232 Pyroelectric material layer (PZT layer, etc.),
232a, 232b end of arm part,
234 Lower electrode (first electrode),
RX Lower electrode (first electrode) extension (overhang or extension),
236 Upper electrode (second electrode), 250 insulating layer,
252, 254 first contact hole and second contact hole,
260 heat transfer member,
270 1st light absorption layer, 272 2nd light absorption layer,
FL heat collecting member heat collecting part, CN heat transferring member connecting part,

Claims (8)

A substrate,
A support member supported via a cavity with respect to the substrate;
A heat detecting element formed on the support member and having a structure in which a pyroelectric material layer is sandwiched between a lower electrode and an upper electrode;
A light absorption layer formed on the heat detection element;
The heat detecting element is connected to the heat detecting element by a connecting portion, has a larger area than the connecting portion in a plan view, has light transmittance with respect to light in at least a part of the wavelength region, and is inside the light absorbing layer. A heat transfer member provided with a heat collecting part formed on,
The lower electrode has an extending portion extending so as to surround the pyroelectric material layer in a plan view, and the extending portion transmits light that has passed through the heat collecting portion of the heat transfer member. A thermal detector characterized by having a light reflection characteristic of reflecting at least a part thereof. The thermal detector according to claim 1,
The thermal light detector, wherein the light absorption layer is formed on the support member and around the heat detection element. The thermal detector according to claim 2, wherein
The light absorbing layer is
A first light absorbing layer formed in contact with the heat transfer member between the heat transfer member and the extended portion of the lower electrode of the heat detection element;
On the heat transfer member, a second light absorption layer formed in contact with the heat transfer member;
A thermal photodetector comprising: The thermal detector according to claim 3 , wherein
A first optical resonator for the first wavelength is configured between the surface of the extending portion of the lower electrode and the upper surface of the second light absorption layer,
A second optical resonator for a second wavelength different from the first wavelength is configured between a lower surface of the second light absorbing layer and an upper surface of the second light absorbing layer. Thermal type photo detector. The thermal detector according to any one of claims 1 to 4, wherein
The thermal detector according to claim 1, wherein the heat transfer member also serves as wiring for connecting the heat detection element to another element.   A plurality of the thermal detectors according to any one of claims 1 to 5, which are two-dimensionally arranged.   An electronic apparatus comprising: the thermal detector according to any one of claims 1 to 5; and a control unit that processes an output of the thermal detector. Forming a structure including an insulating layer on a main surface of the substrate, forming a sacrificial layer on the structure including the insulating layer, and forming a support member on the sacrificial layer;
The support member has a structure in which a pyroelectric material layer is sandwiched between a lower electrode and an upper electrode, and the lower electrode extends so as to surround the pyroelectric material layer in plan view. Forming a heat detecting element having a light reflection characteristic in which the extending portion reflects incoming light,
Forming a first light absorption layer so as to cover the heat detection element, and planarizing the first light absorption layer;
After forming a contact hole in a part of the first light absorption layer, forming a material layer having thermal conductivity and light transmittance for light in at least a part of the wavelength band, and patterning the material layer A step of forming a heat transfer member including a connection portion connected to the heat detection element and a heat collection portion having a larger area than the connection portion in plan view;
Forming a second light absorption layer on the first light absorption layer;
Patterning the first light absorption layer and the second light absorption layer;
Patterning the support member;
Removing the sacrificial layer by etching to form a cavity between the support member and the structure including an insulating layer formed on the main surface of the substrate;
The manufacturing method of the thermal type photodetector characterized by including.

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