JP2013134079A - Terahertz camera and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terahertz camera suppressing heat dissipation from a pyroelectric element.SOLUTION: A pyroelectric detector comprises a pyroelectric detection element, a support member 210 and a support part. The pyroelectric detection element includes a first electrode, a second electrode 236 and a pyroelectric material 232. The first electrode includes a capacitor 230 having a first region 233A and a second region 233B. The pyroelectric detection element further includes a layer insulating film 260 covering the capacitor, a first contact hole 252 formed in the layer insulating film and communicated to the second region of the first electrode, a first plug 226 buried in the first contact hole, a second contact hole 254 formed in the layer insulating film 260 and communicated to the second electrode, a second plug 228 buried in the second contact hole, a first electrode wiring layer 222 connected to the first plug, and a second electrode wiring layer 224 connected to the second plug. Heat conductivity of the second electrode wiring layer is lower than that of a material of the second electrode in a portion connected with the second plug.

Description

  The present invention relates to a terahertz camera and an electronic apparatus using the terahertz camera.

Terahertz waves are electromagnetic waves located between infrared and radio waves. The image measurement technology using terahertz waves has been studied for use in various fields. For example, there are a specific substance detection device using a terahertz camera, determination of counterfeit bills, detection of chemicals in envelopes, non-destructive inspection of buildings, and the like.
On the other hand, as an infrared camera, there is a camera using a pyroelectric detector. The applicant has invented a technique of using a pyroelectric detector in a terahertz camera because the wavelength of the terahertz wave is close to infrared.

  The pyroelectric detector cell has a detection element including a capacitor composed of a pyroelectric body connected to the upper electrode and the lower electrode, and various proposals have been made regarding the material of the electrode and the pyroelectric body and the electrode wiring structure. (Patent Documents 1 and 2).

  Capacitors including ferroelectrics connected to the upper and lower electrodes are used in ferroelectric memories, and various proposals have been made regarding electrodes suitable for ferroelectric memories and ferroelectric materials. (Patent Documents 3 and 4).

Japanese Patent Laid-Open No. 10-104062 JP 2008-232896 A JP 2009-71242 A JP 2009-129972 A

  In Patent Document 1, the lower electrode itself is routed and also used as a lower electrode wiring, and the upper electrode itself is routed and also used as an upper electrode wiring layer. The lower electrode and the upper electrode of the capacitor are made of a material having low electric resistance (for example, Pt or Ir) in view of required electric characteristics, and also have high thermal conductivity (Pt is 71.6 W / mK, Ir is 147 W). / MK). Therefore, in the technique of Patent Document 1, the heat of the detection element is transferred to the outside through the lower electrode wiring or the upper electrode wiring. Therefore, high characteristics cannot be secured as a pyroelectric detector based on a detection principle in which the amount of polarization of the pyroelectric material changes based on temperature.

  As a modification of the technique of Patent Document 1, a stack type in which a lower electrode wiring layer is connected to a lower surface of a lower electrode and an upper electrode wiring is connected to an upper surface of the upper electrode is used for a ferroelectric memory.

  Patent Document 2 discloses a planar type capacitor different from Patent Document 1. In Patent Document 2, a lower platinum film (8) as a lower metal thin film is formed on an Al203 thin film (6) having crystallinity formed on a single crystal semiconductor substrate (4), and the lower metal thin film (8) is formed. A ferroelectric thin film (10) is laminated only on a part of the upper surface, and an upper platinum film (12), which is an upper metal thin film, is laminated only on a part of the upper surface of the ferroelectric thin film (8) (FIG. 2). , 3 and claim 1). On the upper surfaces of the lower metal thin film (8) and the upper metal thin film (12), the wiring (16) formed of the metal thin film is connected to the exposed portion not covered with the insulating film (14) (paragraph 0033). ).

  However, Patent Document 2 is exclusively interested in the crystallinity of the lower metal thin film (8), the ferroelectric thin film (10), and the upper metal thin film (129), and is indifferent to the heat dissipation from the wiring (16). .

  According to some aspects of the present invention, in view of the detection principle in which the amount of polarization of the pyroelectric material changes based on the temperature, the heat is prevented from being dissipated through the wiring from the pyroelectric detection element. A terahertz camera using a pyroelectric detector that can realize detection characteristics can be provided.

A terahertz camera according to one embodiment of the present invention is provided.
A pyroelectric detection element for detecting a terahertz wave having a wavelength of 100 μm or more and 1000 μm or less;
A support member including a first surface and a second surface facing the first surface, the second surface facing the cavity, and mounting the pyroelectric detection element on the first surface;
A support part for supporting a part of the support member;
Have
The pyroelectric detection element is
A first electrode mounted on the support member; a second electrode; and a pyroelectric material disposed between the first and second electrodes, wherein the first electrode is formed by laminating the pyroelectric material. A capacitor that includes a first region and a second region that extends from the first region, the polarization amount of the capacitor changing based on temperature,
An interlayer insulating film covering the surface of the capacitor;
A first contact hole formed in the interlayer insulating film and leading to the second region of the first electrode;
A first plug embedded in the first contact hole;
A second contact hole formed in the interlayer insulating film and communicating with the second electrode;
A second plug embedded in the second contact hole;
A first electrode wiring layer formed on the interlayer insulating film and the support member and connected to the first plug;
A second electrode wiring layer formed on the interlayer insulating film and the support member and connected to the second plug;
Including
The material for forming the second electrode wiring layer has a thermal conductivity lower than that of a material for forming the second electrode in a portion connected to the second plug.

  According to one embodiment of the present invention, the planar capacitor structure can solve the problem of the stacked capacitor structure and improve the sensor characteristics. Further, the second electrode wiring layer connected to the pyroelectric material via the second plug and the second electrode is indispensable for driving the capacitor, but the second electrode wiring layer also functions as a heat dissipation path at the same time. In one embodiment of the present invention, the heat conductivity of the pyroelectric detection element can be suppressed by lowering the thermal conductivity of the second electrode wiring layer than that of the second electrode, so that heat is radiated from the pyroelectric body. improves.

  In one aspect of the present invention, the thermal conductivity of the material forming the first electrode wiring layer is lower than the thermal conductivity of the material forming the first electrode in a portion connected to the first plug. Can do.

  The first electrode wiring layer connected to the pyroelectric material via the first plug and the first electrode is also indispensable for driving the capacitor, but the first electrode wiring layer also functions as a heat dissipation path at the same time. In one embodiment of the present invention, by reducing the thermal conductivity of the first electrode wiring layer below that of the first electrode, it is possible to suppress the heat from being radiated from the pyroelectric body, and the thermal separability of the pyroelectric detection element is improved. improves.

  In one embodiment of the present invention, at least one of the first electrode wiring layer and the second electrode wiring layer can be formed of titanium nitride or titanium / aluminum / nitride.

  Titanium nitride or titanium / aluminum / nitride is sufficiently smaller than the thermal conductivity of metals such as platinum and iridium suitable as the first electrode material and the second electrode material.

  In one aspect of the present invention, the thermal conductance of the second electrode can be made larger than the thermal conductance of the first electrode.

  Since the first electrode is in direct contact with the support member and thermally diffuses by solid conduction, the first electrode should have a low thermal conductance. On the other hand, since the second electrode is not in direct contact with the support member or the like, the thermal conductance of the second electrode may be larger than that of the first electrode. Even in this case, if the thermal conductivity of the second electrode wiring layer is lowered, heat dissipation from the second electrode side can be suppressed.

  In one aspect of the present invention, the pyroelectric detection element may further include an electromagnetic wave absorbing member formed in a region upstream of the second electrode and the second electrode wiring layer in the electromagnetic wave incident direction. it can.

  As described above, when the electromagnetic wave absorbing member is disposed upstream of the capacitor in the electromagnetic wave incident direction, heat generated by the electromagnetic wave irradiation is transferred from the electromagnetic wave absorbing member to the pyroelectric body. Since the second electrode exists in this heat transfer path, suppressing heat dissipation from the second electrode wiring layer connected to the second electrode increases the heat transfer efficiency from the electromagnetic wave absorbing member to the pyroelectric material. Contribute. Therefore, the thermal separability of the pyroelectric detection element can be improved only by making the heat transfer coefficient of the second electrode wiring layer lower than that of the second electrode.

  In one aspect of the present invention, the electromagnetic wave absorbing member is formed so as to cover the entire surface of the second electrode in a plan view as viewed from the electromagnetic wave incident direction, and the pyroelectric material is the first electrode. Can be formed so as to cover the entire surface facing the surface in contact with the surface.

  If it carries out like this, the whole surface of a 2nd electrode can be made into an electromagnetic wave reflective surface, and electromagnetic wave absorption efficiency will be improved by returning the electromagnetic wave which permeate | transmitted the electromagnetic wave absorption member to the electromagnetic wave absorption member.

  In one aspect of the present invention, the electromagnetic wave absorbing member is formed in a position overlapping each of the first region of the first electrode and at least a part of the second region of the first electrode in plan view. Can do.

  In this way, in addition to increasing the volume of the electromagnetic wave absorbing member and increasing the electromagnetic wave absorption amount, the first electrode can also be an electromagnetic wave reflecting surface, and by returning the electromagnetic wave transmitted through the electromagnetic wave absorbing member to the electromagnetic wave absorbing member, The electromagnetic wave absorption efficiency is further improved.

  In one aspect of the present invention, the first electrode wiring layer includes a first connection portion connected to the first plug and a first connection portion that is drawn from the first connection portion and has a narrower width than the first connection portion. The second electrode wiring layer is connected to the second plug, and the second electrode wiring layer is drawn from the second connection portion and has a width narrower than that of the second connection portion. And a width of the second lead-out wiring portion can be made narrower than a maximum length of a cross section of the second contact hole.

  This increases the thermal resistance of the second lead-out wiring portion and improves the thermal separation characteristics of the pyroelectric detection element, and reduces the amount of electromagnetic wave reflection at the second lead-out wiring portion to reduce the electromagnetic wave reflection at the second electrode. The amount can be increased, and the electromagnetic wave absorption efficiency is increased.

  In one aspect of the present invention, the width of the first lead wiring portion can be made narrower than the maximum length of the cross section of the first contact hole.

  This increases the thermal resistance of the first lead-out wiring part and improves the thermal separation characteristics of the pyroelectric detection element, and also reduces the amount of electromagnetic wave reflection at the first lead-out wiring part to reduce the electromagnetic wave reflection at the first electrode. The amount can be increased, and the electromagnetic wave absorption efficiency is increased.

  In one embodiment of the present invention, a reducing gas barrier film may be further provided between the interlayer insulating film and the capacitor.

  Since the characteristics of the capacitor deteriorate when oxygen deficiency due to the reducing gas occurs during manufacturing or actual use, the capacitor can be protected by the reducing gas barrier layer.

A terahertz camera according to another aspect of the present invention is configured by two-dimensionally arranging the above-described pyroelectric detectors along two axial directions.
This pyroelectric detection device can provide a clear energy distribution image because the detection sensitivity is enhanced by the pyroelectric detector of each cell.

  An electronic apparatus according to another aspect of the present invention includes the terahertz camera described above.

1 is a schematic cross-sectional view of a planar capacitor according to an embodiment of the present invention. 1 is a schematic plan view of a pyroelectric detection device according to an embodiment of the present invention. It is a schematic sectional drawing of the pyroelectric detector for 1 cell of the pyroelectric detection apparatus which concerns on embodiment of this invention. It is a schematic sectional drawing of the manufacturing process which shows the supporting member and detection element which are formed on a sacrificial layer. It is a schematic sectional drawing which shows the modification which strengthened the reducing gas barrier property of wiring plug vicinity. It is a schematic sectional drawing for demonstrating the capacitor structure of a pyroelectric detector. It is a schematic sectional drawing of the pyroelectric detector which changed the arrangement | positioning area | region of an electromagnetic wave absorption film. It is a block diagram of the electronic device containing a pyroelectric detector. FIG. 9A and FIG. 9B are diagrams showing a configuration example of a pyroelectric detection device in which pyroelectric detectors are two-dimensionally arranged. It is sectional drawing which shows an example of the stack type capacitor which is a comparative example. It is sectional drawing which shows another example of the stack type capacitor which is a comparative example. It is a figure which shows the terahertz camera which concerns on embodiment of this invention.

1. Pyroelectric detection device A plurality of cell pyroelectric detectors 200 each having a support member 210 shown in FIG. 1 and a detection element 220 as a pyroelectric detection element mounted thereon are arranged in two axial directions, for example, orthogonal FIG. 2 shows a pyroelectric detection device arranged in the biaxial direction. Note that the pyroelectric detector may be composed of a pyroelectric detector for only one cell. In FIG. 2, a plurality of posts 104 are erected from a base (also referred to as a fixed part) 100. For example, a pyroelectric detector 200 for one cell supported by two posts (supports) 104 is arranged in two orthogonal directions. It is arranged in the axial direction. The area occupied by the pyroelectric detector 200 for one cell is, for example, 100 × 100 μm.

  As shown in FIG. 2, the pyroelectric detector 200 includes a support member (membrane) 210 connected to two posts (support portions) 104 and a detection element 220. An area occupied by the detection element 220 for one cell is, for example, 80 × 80 μm.

  The pyroelectric detector 200 for one cell is not contacted except for being connected to the two posts 104, and a cavity 102 (see FIG. 2) is formed below the pyroelectric detector 200. An opening 102 </ b> A communicating with the cavity 102 is disposed around the pyroelectric detector 200 in plan view. Thus, the pyroelectric detector 200 for one cell is thermally separated from the pyroelectric detectors 200 of the base 100 and other cells.

  The support member 210 has a mounting part 210A for mounting and supporting the detection element 220, and two arms 210B connected to the mounting part 210A, and the free ends of the two arms 210B are connected to the post 104. Has been. The two arms 210 </ b> B are thin and redundantly extended so as to thermally separate the detection element 220.

  FIG. 2 is a plan view in which members above the wiring layer connected to the upper electrode are omitted. FIG. 2 shows a first electrode (lower electrode) wiring layer 222 and a second electrode ( An upper electrode) wiring layer 224 is shown. Each of the first and second electrode wiring layers 222 and 224 extends along the arm 210 </ b> B and is connected to a circuit in the base portion 100 via the post 104. The first and second electrode wiring layers 222 and 224 are also formed to extend narrowly and redundantly in order to thermally isolate the detection element 220.

2. Planar type and stack type 2.1. Planar Type FIG. 1 shows a planar type capacitor 2340 employed in the pyroelectric detector of this embodiment. As a comparative example, FIGS. 10 and 11 show a stack type capacitor.

  In FIG. 1, the pyroelectric detector includes a detection element 220, a first surface 211A, and a second surface 211B opposite to the first surface 211A, and a support member on which the detection element 220 is mounted on the first surface 211A. 210. The second surface 211B of the support member 210 is disposed facing the cavity 102, and a part of the support member 210 is supported by the post (support portion) 104 shown in FIG.

  The detection element 220 includes a first electrode (lower electrode) 234, a second electrode (upper electrode) 236, and a pyroelectric body 232 as a pyroelectric material disposed between the first and second electrodes 234 and 236. The capacitor 230 has a polarization amount that changes based on temperature. The first electrode 234 includes a first region 233A in which the pyroelectric body 232 is stacked and a second region 233B formed to extend from the first region 233A. The capacitor 230 is supported by mounting the first electrode 234 on the support member 210.

  An interlayer insulating film (passivation film) 260 is formed so as to cover the surface of the capacitor 230. In the interlayer insulating film 260, a first contact hole 252 that communicates with the second region 233B of the first electrode 234 and a second contact hole 254 that communicates with the second electrode 236 are formed.

  A first plug 226 is embedded in the first contact hole 252. A first electrode wiring layer 222 connected to the first plug 226 is formed on the interlayer insulating film 260 and the support member 210. Similarly, a second plug 228 is embedded in the second contact hole 254. A second electrode wiring layer 224 connected to the second plug 228 is formed on the interlayer insulating film 260 and the support member 210.

2.2. Stack Type A stack type capacitor compared with the planar type of the present embodiment is shown in FIGS. The stack type capacitors shown in FIGS. 10 and 11 are different from the planar type capacitor shown in FIG. 1 in the wiring structure for the first electrode (lower electrode) 234.

  In FIG. 10, a contact hole 600 is formed in the first surface 211 </ b> A of the support member 210, and a first electrode wiring layer 602 is formed in the layer of the support member 210. One electrode 234 and the first electrode wiring layer 602 are connected.

  In this case, the first electrode wiring layer 602 is formed on the etching protection film 606 (not shown in FIG. 1) formed on the lower surface of the support member 210, and then the support member 210 is laminated. As will be described in detail later, the etching protective film 606 etches the support member 210 when forming the cavity 102 by isotropically etching the sacrificial layer after forming the support member 210 and the like laminated on the sacrificial layer. It is a film for protecting from.

  Here, after the first electrode wiring layer 602 is formed on the etching protection film 606, the first electrode wiring layer 602 is etched for patterning. At that time, as shown in the enlarged view of part B of FIG. 10, the etching protective film 606 is also etched together with the first electrode wiring layer 602, and a thin film portion is generated. When the etching protective film 606 is thinned, the performance of the protective film is deteriorated. If the etching protection film 606 is formed thick in advance in consideration of the thin film phenomenon, the heat from the detection element 220 is easily diffused through the etching protection film 606, and the thermal separation characteristic of the detection element 220 is deteriorated. .

  On the other hand, in the stacked capacitor shown in FIG. 11, the first electrode wiring layer 608 that contacts the first electrode 234 is formed on the uppermost layer of the support member 210. In that case, after forming the 1st electrode wiring layer 608 on the whole surface of the supporting member 210, the 1st electrode wiring layer 608 is patterned. Since a step is generated in this state, the surface layer of the support member 210 is flattened so as to be flush with the first electrode wiring layer 608 after the support member 210 is additionally laminated. Thereafter, the first electrode 234, the pyroelectric body 232, and the second electrode 236 are stacked and then patterned to have the shape of the capacitor 230. During the patterning of the capacitor 230, as shown in the enlarged view of part C of FIG. 11, the first electrode wiring layer 608 in the region other than the region directly under the first electrode 234 is etched to be thinned or a disconnection occurs. End up. In consideration of this phenomenon, even if the first electrode wiring layer 608 is formed thick, the film thickness of the first electrode wiring layer 608 varies due to etching and the thermal separation characteristics vary, so that the sensor characteristics are deteriorated.

2.3. Problems of Thermally Isolated Pyroelectric Detector and Countermeasures As described above, the planar capacitor is superior to the stacked capacitor from the viewpoint of sensor characteristics of the thermally separated detection element. However, there is a problem that the first and second electrode wiring layers function as a heat conduction path as a problem common to the planar type capacitor and the stack type capacitor.

  In other words, the first and second electrode wiring layers 222 and 224 are indispensable for driving the pyroelectric capacitor 230, while the heat of the capacitor 230 is dissipated from the first and second electrode wiring layers 222 and 224. End up.

  Therefore, in the present embodiment, the thermal conductivity of the material forming the first and second electrode wiring layers 222 and 224 is set to be the first and second electrodes 234 in the portion connected to the first and second plugs 226 and 228. , 236 is made lower than the thermal conductivity of the material (if it is a single layer, it is that single layer electrode material, and if it is a plurality of layers, it is the uppermost layer electrode material).

  The thermal conductivity of the material of the first and second electrodes 234 and 236 is, for example, 71.6 W / mK for platinum (Pt) and 147 W / mK for iridium (Ir). On the other hand, aluminum (Al), which is a general wiring material, is 237 W / mK, and copper (Cu) is 403 W / mK, and the thermal conductivity is usually high in the first and second electrodes 234 and 236.

  In the present embodiment, a metal material suitable as an electrode material for the first and second electrodes 234 and 236, for example, a material having lower thermal conductivity than platinum (Pt) or iridium (Ir), for example, titanium nitride (TiN) or The first and second electrode wiring layers 222 and 224 are formed of titanium / aluminum / nitride (TiAlN). For example, the thermal conductivity of titanium nitride (TiN) is 29 W / mK, the thermal conductivity of titanium-aluminum nitride (TiAlN) is 5 to 10 W / mK, and the electrodes of the first and second electrodes 234 and 236 Thermal conductivity is sufficiently lower than, for example, platinum (Pt) and iridium (Ir) which are metal materials suitable as materials.

  In this way, it is possible to suppress the heat of the pyroelectric body 232 from being dissipated through the first and second electrode wiring layers 222 and 224 that are indispensable for driving the capacitor 230, and the heat separation property of the detection element 220 is improved. .

  As will be described later, an electromagnetic wave absorber is disposed above the capacitor 230, and heat generated by the electromagnetic wave irradiation is transmitted from the electromagnetic wave absorber to the pyroelectric body 232. Since the second electrode (upper electrode) 236 is present in this heat transfer path, suppressing heat dissipation from the second electrode wiring layer 224 connected to the second electrode 236 is effective from the electromagnetic wave absorber to the pyroelectric body 232. Contributes to improving the heat transfer efficiency to. Therefore, the thermal separability of the detection element 220 can be improved only by making the heat transfer coefficient of the second electrode wiring layer 224 lower than that of the second electrode 236.

  In particular, as will be described later, in order to increase the heat transfer efficiency from the electromagnetic wave absorber to the pyroelectric body 232, the thermal conductance of the second electrode (upper electrode) 236 is made larger than the thermal conductance of the first electrode (lower electrode) 234. In such a case, the thermal separability of the detection element 220 can be effectively improved only by making the heat transfer coefficient of the second electrode wiring layer 224 lower than that of the second electrode 236. However, by making the heat transfer coefficient of the first electrode wiring layer 222 lower than that of the first electrode 234, the heat of the pyroelectric body 232 is dissipated through the first electrode 234 and the first electrode wiring layer 222. Therefore, the thermal isolation of the detection element 220 is further improved.

  Here, as shown in FIGS. 1 and 2, the first electrode wiring layer 222 is pulled out from the first connection portion 222A connected to the first plug 226 and the first connection portion 222A, and the first connection portion 222A. The first lead-out wiring part 222B having a narrower width can be included. Similarly, the second electrode wiring layer 224 includes a second connection portion 224A connected to the second plug 228 and a second lead-out wiring portion that is drawn from the second connection portion 224A and narrower than the second connection portion 224A. 224B.

  In the present embodiment, as shown in FIG. 2, the width W22 of the second lead-out wiring portion 224B is narrower than the maximum length W21 of the cross section of the second contact hole 254. The maximum cross-sectional length W21 of the second contact hole 254 is a diagonal length if the outer shape of the contact hole is rectangular, and a diameter if the outer shape is circular. In this embodiment, unlike Patent Document 2, there is no need to dispose an electromagnetic wave absorbing film in the second contact hole 254, so the size of the second contact hole 254 can be set to a minimum value in design. Since the width W22 of the second lead wiring part 224B is narrower than the maximum length W21 in the cross section of the second contact hole 254, the heat transfer characteristics can be deteriorated in proportion to the cross-sectional area. This can also improve the thermal separation property of the detection element 220.

  In addition to the above configuration, as shown in FIG. 2, the width W12 of the first lead-out wiring portion 222B can be made narrower than the maximum length W11 of the cross section of the first contact hole 252. As a result, the heat transfer characteristics of the first lead-out wiring portion 222B are also deteriorated, so that the heat separability of the detection element 220 can be further improved.

  Another technical significance of narrowing the widths W12 and W22 of the first and second lead-out wiring portions 222B and 224B is to improve the absorption efficiency in the electromagnetic wave absorption film, which will be described later.

3. Outline of Pyroelectric Detector FIG. 3 is a cross-sectional view showing the entire pyroelectric detector 200 shown in FIG. FIG. 4 is a partial cross-sectional view of the pyroelectric detector 200 during the manufacturing process. In FIG. 4, the cavity 102 of FIG. 3 is filled with a sacrificial layer 150. The sacrificial layer 150 exists from before the formation process of the support member 210 and the detection element 220 to after the formation process, and is removed by isotropic etching after the formation process of the detection element 220.

As shown in FIG. 3, the base 100 includes a substrate, for example, a silicon substrate 110, and a spacer layer 120 formed of an insulating film (for example, SiO ₂ ) on the silicon substrate 110. The post (support portion) 104 is formed by etching the spacer layer 120, and is formed of, for example, SiO ₂ . A plug 106 connected to one of the first and second electrode wiring layers 222 and 224 can be disposed on the post (support portion) 104. The plug 106 is connected to a row selection circuit (row driver) provided on the silicon substrate 110 or a readout circuit that reads data from the detector via a column line. The cavity 102 is formed simultaneously with the post 104 by etching the spacer layer 120. The opening 102A shown in FIG. 2 is formed by pattern-etching the support member 210.

The detection element 220 mounted on the first surface 211 </ b> A of the support member 210 includes a capacitor 230. The capacitor 230 includes a pyroelectric body 232, a first electrode (lower electrode) 234 connected to the lower surface of the pyroelectric body 232, and a second electrode (upper electrode) 236 connected to the upper surface of the pyroelectric body 232. Contains. The first electrode 234 may include an adhesion layer 234D that improves adhesion between the support member 210 and a first layer member (for example, a SiO ₂ support layer) 212 (see FIG. 4).

  The capacitor 230 is covered with a reducing gas barrier layer 240 that suppresses the entry of reducing gas (hydrogen, water vapor, OH group, methyl group, etc.) into the capacitor 230 in the process after the capacitor 230 is formed. This is because the pyroelectric body (such as PZT) 232 of the capacitor 230 is an oxide, and when the oxide is reduced, oxygen vacancies are generated and the pyroelectric effect is impaired.

As shown in FIG. 4, the reducing gas barrier layer 240 includes a first barrier layer 242 and a second barrier layer 244. The first barrier layer 242 can be formed, for example, by depositing aluminum oxide Al ₂ O ₃ by sputtering. Since no reducing gas is used in the sputtering method, the capacitor 230 is not reduced. The second barrier layer 244 can be formed, for example, by depositing aluminum oxide Al ₂ O ₃ by, for example, atomic layer chemical vapor deposition (ALCVD). A normal CVD (Chemical Vapor Deposition) method uses a reducing gas, but the capacitor 230 is isolated from the reducing gas by the first barrier layer 242.

Here, the total film thickness of the reducing gas barrier layer 240 is 50 to 70 nm, for example, 60 nm. At this time, the film thickness of the first barrier layer 242 formed by the CVD method is thicker than the second barrier layer 244 formed by the atomic layer chemical vapor deposition (ALCVD) method, and is 35 to 65 nm, for example, 40 nm even if it is thin. Become. On the other hand, the thickness of the second barrier layer 244 formed by atomic layer chemical vapor deposition (ALCVD) can be reduced. For example, aluminum oxide Al ₂ O ₃ is formed to a thickness of 5 to 30 nm, for example, 20 nm. Is done. The atomic layer chemical vapor deposition (ALCVD) method has excellent embedding characteristics as compared with the sputtering method and the like, and therefore can cope with miniaturization. In the first and second barrier layers 242 and 244, The reducing gas barrier property can be enhanced. In addition, the first barrier layer 242 formed by sputtering is less dense than the second barrier layer 244, but it is effective and lowers the heat transfer rate. Dissipation can be prevented.

  An interlayer insulating film 250 is formed on the reducing gas barrier layer 240. In general, when the source gas (TEOS) of the interlayer insulating film 250 chemically reacts, a reducing gas such as hydrogen gas or water vapor is generated. The reducing gas barrier layer 240 provided around the capacitor 230 protects the capacitor 230 from the reducing gas generated during the formation of the interlayer insulating film 250.

  On the interlayer insulating film 250, the first electrode (lower electrode) wiring layer 222 and the second electrode (upper electrode) wiring layer 224, which are also shown in FIGS. A first contact hole 252 and a second contact hole 254 are formed in the interlayer insulating film 250 in advance before the electrode wiring is formed. At that time, contact holes are similarly formed in the reducing gas barrier layer 240. The first electrode (lower electrode) 234 and the first electrode wiring layer 222 are electrically connected by the first plug 226 embedded in the first contact hole 252. Similarly, the second electrode (upper electrode) 236 and the second electrode wiring layer 224 are electrically connected by the second plug 228 embedded in the second contact hole 254.

  Here, when the interlayer insulating film 250 is not present, when the first electrode (lower electrode) wiring layer 222 and the second electrode (upper electrode) wiring layer 224 are subjected to pattern etching, the second reducing gas barrier layer 240 below the second insulating gas barrier layer 240 is subjected to pattern etching. The barrier layer 244 is etched and the barrier property is lowered. The interlayer insulating film 250 is necessary for ensuring the barrier property of the reducing gas barrier layer 240.

  Here, the interlayer insulating film 250 preferably has a low hydrogen content. Therefore, the interlayer insulating film 250 is degassed by annealing. Thus, the hydrogen content of the interlayer insulating film 250 is made lower than that of the passivation film 260 that covers the first and second electrode wiring layers 222 and 224.

Since the reducing gas barrier layer 240 on the top surface of the capacitor 230 is closed without a contact hole when the interlayer insulating film 250 is formed, the reducing gas during the formation of the interlayer insulating film 250 does not enter the capacitor 230. However, after contact holes are formed in the reducing gas barrier layer 240, the barrier properties deteriorate.
As an example for preventing this, for example, as shown in FIG. 4, the first and second plugs 226 and 228 (only the second plug 228 is shown in FIG. 4) are formed into a plurality of layers (first layer 228A and second layer 228B). A barrier metal layer is adopted as the first layer 228A. The reducing gas barrier property is secured by the barrier metal of the first layer 228A. The barrier metal of the first layer 228A is not preferably highly diffusible like titanium Ti, and titanium, aluminum, nitride TiAlN having low diffusibility and high reducing gas barrier property can be employed. As a method for cutting off the intrusion of the reducing gas from the contact hole, the reducing gas barrier layer 290 may be additionally provided so as to surround at least the second plug 228 as shown in FIG. The reducing gas barrier layer 290 may be used in combination with the first layer 228A of the second plug 228 or may exclude the first layer 228A. Note that the reducing gas barrier layer 290 may cover the first plug 226.

A SiO ₂ or SiN passivation film 260 is provided to cover the first and second electrode wiring layers 222 and 224. An electromagnetic wave absorber 270 is provided on the passivation film 260 at least above the capacitor 230. Although the passivation film 260 is also formed of SiO ₂ or SiN, it is preferable to use a different material having a high etching selectivity with respect to the lower passivation film 260 in view of the necessity of pattern etching of the electromagnetic wave absorber 270. An electromagnetic wave is incident on the electromagnetic wave absorber 270 from the direction of the arrow in FIG. 3, and the electromagnetic wave absorber 270 generates heat according to the amount of electromagnetic wave absorbed. When the heat is transferred to the pyroelectric body 232, the amount of spontaneous polarization of the capacitor 230 is changed by the heat, and the electromagnetic wave can be detected by detecting the charge due to the spontaneous polarization.

  Even if reducing gas is generated during the CVD formation of the passivation film 260 and the electromagnetic wave absorber 270, the capacitor 230 is protected by the barrier metal in the reducing gas barrier layer 240 and the first and second plugs 226 and 228.

A reducing gas barrier layer 280 is provided so as to cover the outer surface of the pyroelectric detector 200 including the electromagnetic wave absorber 270. The reducing gas barrier layer 280 needs to be formed thinner than the reducing gas barrier layer 240, for example, in order to increase the transmittance of electromagnetic waves (terahertz waves) incident on the electromagnetic wave absorber 270. For this purpose, an atomic layer chemical vapor deposition (ALCVD) method capable of adjusting the film thickness at the atomic size level is employed. This is because the ordinary CVD method is too thick and the terahertz wave transmittance deteriorates. In the present embodiment, for example, aluminum oxide Al ₂ O ₃ is formed to a thickness of 10 to 50 nm, for example, 20 nm. As described above, the atomic layer chemical vapor deposition (ALCVD) method has excellent embedding characteristics as compared with the sputtering method and the like, so that it is possible to form a dense film at the atomic level corresponding to miniaturization. Therefore, even if it is thin, the reducing gas barrier property can be enhanced.

Further, on the base 100 side, the walls defining the cavity 102, that is, the bottom wall 110 </ b> A and the side wall 104 </ b> A defining the cavity 102 are embedded in the cavity 102 in the process of manufacturing the pyroelectric detector 200. An etching stop film 130 is formed when the sacrificial layer 150 (see FIG. 4) is isotropically etched. Similarly, an etching stop film 140 is also formed on the lower surface of the support member 210 (the upper surface of the sacrificial layer 150). In this embodiment, the reducing gas barrier layer 280 is formed of the same material as the etching stop films 130 and 140. That is, the etching stop films 130 and 140 also have a reducing gas barrier property. The etching stop films 130 and 140 are also formed by depositing aluminum oxide Al ₂ O ₃ to a thickness of 20 to 50 nm by atomic layer chemical vapor deposition (ALCVD).

  Since the etching stop film 130 has a reducing gas barrier property, when the sacrificial layer 150 is isotropically etched with hydrofluoric acid in a reducing atmosphere, it is possible to prevent the reducing gas from penetrating the support member 210 and entering the capacitor 230. In addition, since the etching stop film 140 covering the base portion 100 has a reducing gas barrier property, it is possible to prevent the transistors and wirings of the circuit disposed in the base portion 100 from being reduced and deteriorated.

4). Structure of Support Member As shown in FIG. 3, a post (support part) 104, a support member 210, and a detection element 220 are stacked on the base 100 along a first direction D <b> 1 from the lower layer to the upper layer. The support member 210 mounts the detection element 220 on the first surface 211A side via the adhesion layer 234D, and the second surface 211B side faces the cavity 102. The adhesion layer 234 </ b> D is a part (lowermost layer) of the detection element 220.

As shown in FIG. 5, in the support member 210, at least the first layer member 212 on the first surface side in contact with the adhesion layer 234D is an insulating layer, for example, a SiO ₂ support layer. This SiO ₂ support layer (first layer member) 212 is second than the SiO ₂ support layer (first layer member) 212 when the direction opposite to the first direction D1 shown in FIG. The hydrogen content is smaller than that of, for example, the post (supporting portion) 104 which is another SiO ₂ layer positioned in the direction D2. This can be obtained by reducing the content of hydrogen or moisture in the film by increasing the O ₂ flow rate at the time of CVD film formation as compared with that at the time of normal interlayer insulating film CVD. Thus, the SiO ₂ support layer (first layer member) 212 becomes a low moisture film having a hydrogen content lower than that of, for example, the post (support portion) 104 which is another SiO ₂ layer.

When the water content of the uppermost SiO ₂ support layer (first layer member) 212 of the support member 210 in contact with the adhesion layer 234D is small, the SiO ₂ support layer even if exposed to a high temperature by heat treatment after the pyroelectric 232 is formed. (First layer member) The generation of reducing gas (hydrogen, water vapor) from 212 itself can be suppressed. In this way, it is possible to suppress the reducing species that enter the pyroelectric body 232 in the capacitor 230 from directly below the support 230 (on the support member 210 side), and to suppress oxygen deficiency in the pyroelectric body 232. it can.

For example, moisture in the post (support) 104, which is another SiO ₂ layer positioned in the second direction D2 than the SiO ₂ support layer (first layer member) 212, can also be a reducing species, but is away from the capacitor 230. The influence is less than that of the SiO ₂ support layer (first layer member) 212. However, since the moisture in the post (support part) 104 can also be a reducing species, a film having a reducing gas barrier property is provided in the support member 210 located in the second direction D2 rather than the SiO ₂ support layer (first layer member) 212. It is preferable to form it. A more specific structure of the support member 210 including this point will be described below.

As shown in FIG. 4, the support member 210 is along the second direction D2 shown in FIG. 3, and the SiO ₂ support layer (first layer member) 212, the intermediate layer (second layer member) 214 described above, Another SiO ₂ layer (third layer member) 216 can be laminated and formed.

That is, in this embodiment, the support member 210 that is warped with a single material is formed by stacking a plurality of different materials. Specifically, the first layer member 212 and the third layer member 216 can be formed of an oxide film (SiO ₂ ), and the second layer member 214 as an intermediate layer can be formed of a nitride film (for example, Si ₃ N ₄ ). .

For example, the compressive residual stress generated in the first layer member 212 and the third layer member 216 and the tensile residual stress generated in the second layer member 214 are caused to cancel each other. Thereby, the residual stress as the whole support member 210 can be further reduced or eliminated. In particular, the strong residual stress of the nitride film of the second layer member 214 is caused to cancel out by the reverse residual stresses of the first layer member 212 and the third layer member 216 which are two upper and lower oxide films. Thus, the stress that causes the support member 210 to warp can be reduced. Even if the support member 210 is formed of two layers of an oxide film (SiO ₂ ) in contact with the adhesion layer 234D and a nitride film (eg, Si ₃ N ₄ ), there is an effect of suppressing warpage. Note that if the support member 210 is formed by, for example, the method disclosed in Japanese Patent Application No. 2010-109035, the occurrence of warpage can be prevented. Therefore, the support member 210 does not necessarily have a laminated structure, and a single layer of SiO ₂ layer. It may be formed by.

Here, the nitride film (for example, Si ₃ N ₄ ) forming the second layer member 214 has a reducing gas barrier property. Accordingly, the support member 210 itself can be provided with a function of blocking a reducing inhibition factor that enters the pyroelectric body 232 of the capacitor 230 from the support member 210 side. Therefore, than the second layer member 214, the third layer member 216 located in the second direction D2 in FIG. 3, another SiO ₂ layer is large water content than SiO ₂ support layer (first layer member) 212 Even so, the second layer member 214 having a reducing gas barrier property can prevent the reducing species (hydrogen, water vapor) in the third layer member 216 from entering the pyroelectric body 232.

5. Capacitor structure 5.1. FIG. 6 is a schematic cross-sectional view for explaining the main part of this embodiment. As described above, the capacitor 230 includes the pyroelectric body 232 between the first electrode (lower electrode) 234 and the second electrode (upper electrode) 236. The capacitor 230 can detect the electromagnetic wave by utilizing the fact that the magnitude of the incident electromagnetic wave is converted into heat and the spontaneous polarization amount of the pyroelectric body 232 changes (pyroelectric effect or pyroelectronic effect). In the present embodiment, the incident electromagnetic wave is absorbed by the electromagnetic wave absorber 270 and the electromagnetic wave absorber 270 generates heat, and the electromagnetic wave passes through the solid heat conduction path between the electromagnetic wave absorber 270 and the pyroelectric body 232. Heat generated by the absorber 270 is transmitted.

  In the capacitor 230 of the present embodiment, the thermal conductance G1 of the first electrode (lower electrode) 234 in contact with the support member 210 is made smaller than the thermal conductance G2 of the second electrode (upper electrode) 236. In this way, the capacitor 230 can easily transfer heat due to electromagnetic waves to the pyroelectric body 232 via the second electrode (upper electrode) 236, and the heat of the pyroelectric body 232 can be transmitted to the first electrode (lower electrode) 234. This makes it difficult to escape to the support member 210 via the, thereby improving the signal sensitivity of the detection element 220. Moreover, since the thermal conductivity of the second electrode wiring layer 224 electrically connected to the second electrode 236 is also low as described above, the thermal separation characteristics of the pyroelectric detector 200 are improved.

  The structure of the capacitor 230 having the above characteristics will be described in more detail with reference to FIG. First, the thickness T1 of the first electrode (lower electrode) 234 is thicker than the second electrode (upper electrode) 236 (T1> T2). When the thermal conductivity of the first electrode (lower electrode) 234 is λ1, the thermal conductance G1 of the first electrode (lower electrode) 234 is G1 = λ1 / T1. When the thermal conductivity of the second electrode (upper electrode) 236 is λ2, the thermal conductance G2 of the second electrode (upper electrode) 236 is G2 = λ2 / T2.

  In order to make the relationship of thermal conductance G1 <G2, for example, if the materials of the first and second electrodes 234 and 236 are both the same single material such as platinum Pt or iridium Ir, λ1 = λ2. Since T1> T2 from FIG. 6, the relationship of G1 <G2 can be satisfied.

  First, consider that each of the first and second electrodes 234 and 236 is formed of the same material. In order for the capacitor 230 to align the crystal direction of the pyroelectric body 232, it is necessary to match the crystal lattice level of the interface with the first electrode 234 in the lower layer where the pyroelectric body 232 is formed. That is, the first electrode 234 functions as a crystal seed layer, but platinum Pt is preferable as the first electrode 234 because of its strong self-orientation. Iridium Ir is also suitable as a seed layer material.

  Further, the crystal orientation of the second electrode (upper electrode) 236 may be continuously connected from the first electrode 234 and the pyroelectric body 232 to the second electrode 236 without destroying the crystallinity of the pyroelectric body 232. preferable. Therefore, the second electrode 236 is preferably formed using the same material as the first electrode 234.

  Thus, when the second electrode 236 is formed of the same material as the first electrode 234, for example, a metal such as Pt or Ir, the upper surface of the second electrode 236 can be used as a reflective surface. In this case, as shown in FIG. 6, the distance L from the top surface of the electromagnetic wave absorber 270 to the top surface of the second electrode 236 is preferably λ / 4 (λ is the detection wavelength of the electromagnetic wave). As a result, the electromagnetic wave having the detection wavelength λ is multiple-reflected between the top surface of the electromagnetic wave absorber 270 and the top surface of the second electrode 236, so that the electromagnetic wave absorber 270 efficiently absorbs the electromagnetic wave having the detection wavelength λ. it can.

5.2. Next, the structure of the capacitor 230 of this embodiment shown in FIG. 6 will be described. In the capacitor 230 shown in FIG. 6, the crystal orientations of the pyroelectric body 232, the first electrode 234, and the second electrode 236 are arranged such that the preferential orientation direction is, for example, the (111) plane direction. By being preferentially oriented in the (111) plane orientation, the orientation ratio of the (111) orientation in the other plane orientation is controlled to 90% or more, for example. In order to increase the pyroelectric coefficient, the (100) orientation rather than the (111) orientation is preferable, but the (111) orientation is used in order to easily control the polarization with respect to the applied electric field direction. However, the preferred orientation direction is not limited to this.

  The first electrode 234 includes, in order from the support member 210, an orientation control layer (eg, an Ir layer) 234A that controls the orientation of the first electrode 234 so that the first electrode 234 is preferentially oriented to, for example, the (111) plane; Layer) 234B and a preferentially oriented seed layer (eg, Pt layer) 234C.

  The second electrode 236 includes, in order from the pyroelectric body 232 side, an alignment layer (for example, a Pt layer) 236A whose crystal orientation is aligned with that of the pyroelectric body 232, a second reducing gas barrier layer (for example, an IrOx layer) 236B, A resistance-reducing layer (for example, an Ir layer) 236C that lowers the resistance of the joint surface with the second plug 228 connected to the electrode 236 can be included.

  In this embodiment, the reason why the first and second electrodes 234 and 236 of the capacitor 230 have a multi-layer structure is that the detection element 220 having a small heat capacity is processed with low damage without reducing its capability, and crystal at the interface. The lattice level is matched, and the pyroelectric (oxide) 232 is isolated from the reducing gas even if the periphery of the capacitor 230 becomes a reducing atmosphere at the time of manufacture or use.

The pyroelectric material 232 is crystallized by preferentially orienting, for example, PZT (Pb (Zr, Ti) O ₃ generic name: lead zirconate titanate) or PZTN (PZT added with Nb) or the like in the (111) orientation Growing up. Use of PZTN is preferable in that it is difficult to be reduced even when a thin film is formed, and oxidation deficiency can be suppressed. In order to crystallize the pyroelectric material 232, it is crystallized from the formation stage of the first electrode 234 under the pyroelectric material 232.

For this purpose, an alignment control layer (Ir layer) 234A that functions as an alignment control layer is formed on the first electrode 234 by sputtering. As shown in FIG. 6, for example, a titanium / aluminum / nitride (TiAlN) layer or a titanium nitride (TiN) layer may be formed as the adhesion layer 234D under the orientation control layer 234A. This is because the adhesion between the SiO ₂ support layer 212 and the SiO ₂ which is the uppermost layer can be secured in the support members 210. Titanium (Ti) can also be applied as this type of adhesion layer 234D, but titanium (Ti), such as titanium (Ti), which has high diffusivity is not preferred, and titanium, aluminum, nitride having low diffusibility and high reducing gas barrier properties. (TiAlN) or titanium nitride (TiN) is preferred.

In addition, when the first layer member 212 of the support member 210 located below the adhesion layer 234D is formed of SiO ₂ , the surface roughness Ra on the adhesion layer side of the SiO ₂ layer in contact with the first electrode is less than 30 nm. It is preferable. This is because the flatness of the surface on which the support member 210 mounts the capacitor 230 can be ensured. If the surface on which the orientation control layer 234A is formed is a rough surface, the rough surface unevenness is reflected during crystal growth, which is not preferable.

The adhesion layer 234D can have a reducing gas barrier property. Titanium / aluminum / nitride (TiAlN) or titanium nitride (TiN) has a reducing gas barrier property. Therefore, even if the reducing gas leaks from the SiO ₂ support layer of the support member, the reducing gas barrier adhesion layer 234D can prevent the reducing gas from entering the capacitor 230.

The thermal conductivity of the adhesion layer 234 </ b> D can be made smaller than the thermal conductivity of the metal material forming the first electrode 234. This makes it difficult for the heat of the capacitor 230 to escape to the support member 210 side through the adhesion layer 234D, and the signal accuracy based on the temperature change in the pyroelectric body 232 can be improved. As described above, the adhesion layer 234D having good adhesion to the SiO ₂ support layer 212 can be made of titanium (Ti), and the thermal conductivity of titanium (Ti) is 21.9 (W / mK). The metal suitable for the first electrode 234, for example, platinum (Pt) thermal conductivity 71.6 (W / m · K) and iridium (Ir) heat conductivity 147 (W / m · K) is significantly smaller, The thermal conductivity of titanium / aluminum / nitride (TiAlN) or titanium nitride (TiN), which is a nitride of titanium, is further reduced depending on the nitrogen / titanium mixing ratio.

  The moisture catalyst activity of the adhesion layer 234D is preferably lower than the moisture catalyst activity of other materials of the first electrode 234. If the adhesive layer 234D has a low water catalytic activity for generating hydrogen by reacting with moisture, it is possible to suppress the generation of reducing gas due to reaction with OH groups or adsorbed water in the lower interlayer insulating film or on the surface.

The IrOx layer 234B functioning as a reducing gas barrier layer in the first electrode 234 has the first support member 210 exhibiting a reducing gas barrier property in order to isolate the pyroelectric body 232 from reducing inhibitors from below the capacitor 230. It is used together with a two-layer member (eg, Si ₃ N ₄ ) and an etching stop film (eg, Al ₂ O ₃ ) 140 of the support member 210. For example, degassing from the base 100 during firing of the pyroelectric material (ceramic) 232 or other annealing process, or a reducing gas used in the isotropic etching process of the sacrificial layer 150 becomes a reducing inhibitor.

  It should be noted that evaporative gas may be generated inside the capacitor 230 during high-temperature processing, such as during the pyroelectric body 232 firing step, but the escape path for the evaporative gas is secured by the first layer member 212 of the support member 210. The In other words, in order to escape the evaporated gas generated inside the capacitor 230, it is preferable that the first layer member 212 is not provided with a gas barrier property and the second layer member 214 is provided with a gas barrier property.

  In addition, the IrOx layer 234B has little crystallinity per se, but since it has a good compatibility with the Ir layer 234A in a metal-metal oxide relationship, it can have the same preferred orientation direction as the Ir layer 234A. .

  The Pt layer 234C functioning as a seed layer in the first electrode 234 serves as a seed layer of the preferential orientation of the pyroelectric body 232 and is (111) oriented. In the present embodiment, the Pt layer 234C has a two-layer structure. The first Pt layer forms the basis of the (111) orientation, and the second Pt layer forms microroughness on the surface so that the pyroelectric body 232 functions as a preferentially oriented seed layer. The pyroelectric material 232 is (111) oriented following the seed layer 234C.

  When the second electrode 236 is formed by sputtering, the interface is physically rough, trap sites are generated, and the characteristics may be deteriorated. Therefore, the first electrode 234, the pyroelectric body 232, and the second electrode 236 may be used. The crystal-level lattice matching is reconstructed so that the crystal orientations are continuously connected.

  The Pt layer 236A in the second electrode 236 is formed by sputtering, but the crystal direction of the interface becomes discontinuous immediately after sputtering. Therefore, after that, annealing treatment is performed to recrystallize the Pt layer 236A. That is, the Pt layer 236A functions as an orientation matching layer in which the crystal orientation of the pyroelectric material 232 is matched.

  The IrOx layer 236B in the second electrode 236 functions as a barrier for reducing deterioration factors from above the capacitor 230. Further, the Ir layer 236C in the second electrode 236 is used to reduce the resistance value between the IrOx layer 236B and the second plug 228 because the resistance value of the IrOx layer 236B is large. The Ir layer 236C is compatible with the IrOx layer 236B in the metal oxide-metal relationship, and can have the same preferred orientation direction as the IrOx layer 236B.

  As described above, in the present embodiment, the first and second electrodes 234 and 236 are arranged in multiple layers of Pt, IrOx, and Ir in order from the pyroelectric body 232 side, and the forming material is centered on the pyroelectric body 232. Symmetrical arrangement.

  However, the thickness of each layer of the multilayer structure forming the first and second electrodes 234 and 236 is asymmetric about the pyroelectric body 232. First, the total thickness T1 of the first electrode 234 and the total thickness T2 of the second electrode 236 satisfy the relationship (T1> T2) as described above. Here, the thermal conductivities of the Ir layer 234A, IrOx layer 234B, and Pt layer 234C of the first electrode 234 are λ1, λ2, and λ3, and the thicknesses are T11, T12, and T13. The thermal conductivities of the second electrode Ir layer 236C, IrOx layer 236B, and Pt layer 236A are λ1, λ2, and λ3 as in the first electrode 234, and the thicknesses thereof are T21, T22, and T23.

  Further, assuming that the thermal conductances of the Ir layer 234A, IrOx layer 234B, and Pt layer 234C of the first electrode 234 are G11, G12, and G13, G11 = λ1 / T11, G12 = λ2 / T12, and G13 = λ3 / C13. . When the thermal conductances of the Ir layer 236C, IrOx layer 236B, and Pt layer 236A of the second electrode 236 are G21, G22, and G23, G21 = λ1 / T21, G22 = λ2 / T22, and G13 = λ3 / T23.

Since the total thermal conductance G1 of the first electrode 234 is expressed by 1 / G1 = (1 / G11) + (1 / G12) + (1 / G13),
G1 = (G11 × G12 × G13) / (G11 + G12 + G13) (1)
Similarly, the total thermal conductance G2 of the second electrode 236 is expressed by 1 / G2 = (1 / G21) + (1 / G22) + (1 / G23).
G2 = (G21 × G22 × G23) / (G21 + G22 + G23) (2)
It becomes.

  Next, the thickness of each layer of the multilayer structure forming the first and second electrodes 234 and 236 is substantially as follows under the condition satisfying T11 + T12 + T13 = T1> T2 = T21 + T22 + T23.

Ir layer 234A, 236C T11: T21 = 1: 0.7
IrOx layers 234B, 236B T12: T22 = 0.3: 1
Pt layer 234C, 236A T13: T23 = 3: 1
The reason for this film thickness relationship is as follows. First, regarding the Ir layers 234A and 236C, the Ir layer 234A in the first electrode 234 functions as an orientation control layer. The purpose of the Ir layer 236C of the electrode 236 is to reduce the resistance, and the lower the resistance, the lower the resistance.

  Next, regarding the IrOx layers 234B and 236B, the barrier property of the reducing inhibitor from the lower side and the upper side of the capacitor 230 is that other barrier films (second layer member 214, reducing gas barrier layer 240, etching stop film 140 and reduction). The IrOx layer 234B of the first electrode 234 is thin, but the IrOx layer 236B of the second electrode 236 is thick in preparation for the low barrier property at the second plug 228. doing.

  Finally, with regard to the Pt layers 234C and 236A, the Pt layer 234C in the first electrode 234 functions as a seed layer that determines the preferred orientation of the pyroelectric body 232, whereas a predetermined thickness is required. Since the purpose of the Pt layer 236A of the second electrode 236 functions as an alignment matching layer that matches the alignment of the pyroelectric body 232, it may be formed thinner than the Pt layer 234C in the first electrode 234.

  The thickness ratio of the Ir layer 234A, IrOx layer 234B, and Pt layer 234C of the first electrode 234 is, for example, T11: T12: T13 = 10: 3: 15, and the Ir layer 236C and IrOx layer 236B of the second electrode 236 are set. The thickness ratio of the Pt layer 236A is, for example, T21: T22: T23 = 7: 10: 5.

  Here, the heat transfer coefficient λ3 of Pt is 71.6 (W / m · K), and the heat transfer coefficient λ1 of Ir is approximately λ1 = 147 (W / m · K), which is approximately the heat transfer coefficient λ3 of Pt. 2 times. The thermal conductivity λ2 of IrOx varies depending on the heat degree and the oxygen / metal ratio (O / M), but does not exceed the thermal conductivity λ1 of Ir. Substituting the relationship between the film thickness and the heat transfer coefficient into the equations (1) and (2) to obtain the magnitude relationship between G1 and G2, it can be seen that G1 <G2. Thus, even if the first and second electrodes 234 and 236 are formed in a multilayer structure as in this embodiment, G1 <G2 is satisfied from the relationship between the heat transfer coefficient and the film thickness.

  Further, as described above, when the first electrode 234 has the adhesion layer 234D on the joint surface with the support member 210, the thermal conductance C1 of the first electrode 234 becomes smaller, and therefore the relationship of G1 <G2 is satisfied. It becomes easy.

  Since the etching mask of the capacitor 230 deteriorates as the etching progresses, the sidewall of the capacitor 230 becomes narrower toward the upper side and wider toward the lower side as shown in FIG. However, since the taper angle with respect to the horizontal plane is about 80 degrees, the area expansion of the first electrode 234 relative to the second electrode 236 is small considering that the total height of the capacitor 230 is on the order of nanometers. Therefore, the heat transfer amount at the first electrode 234 can be made smaller than the heat transfer amount at the second electrode 236 due to the thermal conductance relationship between the first and second electrodes 234 and 236.

5.3. Modification of Capacitor Structure As described above, the single-layer structure and the multilayer structure have been described for each of the first and second electrodes 234 and 236 of the capacitor 230. Various other combinations with G1 <G2 are possible.

  First, the Ir layer 236C of the second electrode 236 can be deleted. In this case, if, for example, Ir is used as the material of the second plug 228, the purpose of reducing the resistance can be achieved. In this case, the thermal conductance G2 of the second electrode 236 becomes larger than that in the case of FIG. 6, so that the relationship G1 <G2 can be easily satisfied. In this case, the reflection surface defining L = λ / 4 shown in FIG. 6 is replaced with the Pt layer 236A of the second electrode 236, but the multiple reflection surface can be secured in the same manner.

  Next, the thickness of the IrOx layer 236B in the second electrode 236 of FIG. 6 can be made equal to or less than the thickness of the IrOx layer 234B in the first electrode 234. As described above, other barrier films (second layer member 214, reducing gas barrier layer 240, etching stop film 140 and reducing gas barrier layer 280) are used in combination with the barrier property of the reducing inhibitor from below and above the capacitor 230. Therefore, if the reducing gas barrier property in the second plug 228 is enhanced as shown in FIG. 5, for example, the thickness of the IrOx layer 236B in the second electrode 236 is thicker than the IrOx layer 234B in the first electrode 234. do not have to. As a result, the thermal conductance G2 of the second electrode 236 becomes larger, and the relationship of G1 <G2 is more easily established.

  Next, the IrOx layer 234B in the first electrode 234 of FIG. 6 can be deleted. Even if the IrOx layer 234B is deleted, the crystal continuity between the Ir layer 234A and the Pt layer 234C is not hindered, so there is no problem with respect to the crystal orientation. By deleting the IrOx layer 234B, the capacitor 230 does not have a barrier film against the reducing inhibitor from below. However, the second layer member 214 is present on the support member 210 that supports the capacitor 230, and the etching stop film 140 is present on the lower surface of the support member 210. The second layer member 214 and the etching stop film 140 are provided with a reducing gas barrier property. If the capacitor 230 is formed, a capacitor 230 can secure a barrier property against a reducing inhibitor from below.

  Here, when the IrOx layer 234B in the first electrode 234 is deleted, the thermal conductance G1 of the first electrode 234 increases. Therefore, it may be necessary to increase the thermal conductance G2 of the second electrode 236 in order to establish the relationship of G1 <G2. In that case, for example, it is conceivable to delete the IrOx layer 236B in the second electrode 236. If the IrOx layer 236B can be deleted, the Ir layer 236C is also unnecessary. This is because the Pt layer 236A functions as a low resistance layer instead of the Ir layer 236C. The barrier property of the reducing inhibitor from above the capacitor 230 can be secured by the reducing gas barrier layer 240 described above, the first layer 228A shown in FIG. 4, or the reducing gas barrier layer 290 shown in FIG.

  When the second electrode 234 of FIG. 6 is formed of only the Pt layer 236A as described above, the first electrode 234 is a single layer of the Pt layer 234C, two layers of the Ir layer 234A and the Pt layer 234C, or FIG. A three-layer structure including an Ir layer 234A, an IrOx layer 234B, and a Pt layer 234C can be used. In any of these cases, for example, if the thickness T11 of the Pt layer 234C of the first electrode 234 is larger than the thickness T21 of the Pt layer 236A of the second electrode 236 (T11> T21), the relationship of G1 <G2 is established. It can be easily established.

  As described above, in the present embodiment, the material for forming the first and second electrodes 234 and 236 in the portion connected to the first and second plugs 226 and 228 (in the case of a single layer, the single-layer electrode material is used. Platinum (Pt) or iridium (Ir) is employed as the uppermost electrode material in the case of a plurality of layers. In either case, by using, for example, titanium nitride (TiN) or titanium-aluminum-nitride (TiAlN) as the first and second electrode wiring layers 222 and 224, the first and second electrode wiring layers 222, 224 The thermal conductivity of the first and second electrodes 234 and 236 can be lowered and the thermal separation characteristics of the pyroelectric detector 200 can be improved.

6). Improvement of Electromagnetic Wave Absorption Efficiency by Reflection on Electrode Surface FIG. 7 is a cross-sectional view of a modified example in which the arrangement region of the electromagnetic wave absorber 270 of FIG. 3 is enlarged. The improvement of electromagnetic wave absorption efficiency due to reflection on the electrode surface will be described with reference to FIG.

  A part of the electromagnetic wave incident from the arrow direction in FIG. 7 is absorbed by the electromagnetic wave absorber 270 and converted into heat, and the other part is transmitted. At this time, in each embodiment of FIGS. 3 and 7, the transmitted electromagnetic wave is reflected on the surface of the second electrode (upper electrode) 236 and returned to the center side of the electromagnetic wave absorber 270 (R1 in FIG. 7). In this way, since the transmitted electromagnetic wave is given an opportunity to be absorbed again by the electromagnetic wave absorber 270 by reflection, the electromagnetic wave absorption efficiency is increased.

  Here, the reflection of the electromagnetic wave occurs not only on the second electrode (upper electrode) 236 but also on the second electrode wiring layer 224 (R1 'in FIG. 7). However, the electromagnetic wave reflected on the second electrode (upper electrode) 236 and the electromagnetic wave reflected on the second electrode wiring layer 224 have a height point at which the absorption maximum in the layer of the electromagnetic wave absorber 270 is obtained. Different. Therefore, the electromagnetic wave absorption efficiency decreases. If the second electrode wiring layer 224 is not present, the height point at which the absorption maximum of the electromagnetic wave reflected on the second electrode (upper electrode) 236 is constant is constant, but the second electrode wiring layer 224 is necessary.

  Therefore, by reducing the width W22 of the second electrode wiring layer 224 as described above, it is possible to suppress a decrease in electromagnetic wave absorption efficiency.

  In the embodiment of FIG. 7, the electromagnetic wave absorber 270 is also disposed at a position facing the second region 233B where the first electrode (lower electrode) 364 is enlarged. Thus, the volume of the electromagnetic wave absorber 270 increases, so that not only the amount of heat absorbed is increased, but also the electromagnetic wave can be reflected on the first electrode (lower electrode) 234 (R2 in FIG. 7). The amount of heat absorbed by the body 270 is further increased.

  In addition, simultaneously with the reflection of the electromagnetic wave on the first electrode (lower electrode) 234, it is also reflected on the first electrode wiring layer 222 (not shown in FIG. 7), causing the same problem as the second electrode. By reducing the width W12 of the one-electrode wiring layer 222, it is possible to suppress a decrease in electromagnetic wave absorption efficiency.

7). Electronic Device FIG. 8 shows a configuration example of an electronic device including the pyroelectric detector according to the present embodiment. This electronic apparatus includes an optical system 400, a sensor device (pyroelectric detector) 410, an image processing unit 420, a processing unit 430, a storage unit 440, an operation unit 450, and a display unit 460. Note that the electronic apparatus of the present embodiment is not limited to the configuration shown in FIG. 8, and some of the components (for example, an optical system, an operation unit, a 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 pyroelectric detectors 200 of the present embodiment described above, and is provided with a plurality of row lines (word lines, scanning lines) and a plurality of column lines (data lines). The sensor device 410 includes a row selection circuit (row driver), a readout circuit that reads data from the detector via a column line, an A / D conversion unit, and the like, in addition to the two-dimensionally arranged detectors. Can do. By sequentially reading data from each detector arranged two-dimensionally, it is possible to perform imaging processing of an object image.

  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 processing unit 430 controls the entire electronic device or controls 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 sensor device 410 is configured by using the pyroelectric detector for one cell as a sensor and arranging the pyroelectric detector for one cell in two dimensions, for example, in two orthogonal directions. In this way, a heat distribution image resulting from electromagnetic waves can be provided. Using this sensor device 410, an electronic device using a terahertz camera such as a specific substance detection device, determination of a counterfeit bill, detection of medicine in an envelope, and nondestructive inspection of a building can be configured.

  FIG. 9A shows a configuration example of the sensor device 410 in FIG. The sensor device includes a sensor array 500, a row selection circuit (row driver) 510, and a readout circuit 520. An A / D converter 530 and a control circuit 550 can be included. By using this sensor device, a high-performance terahertz camera can be realized.

  In the sensor array 500, for example, as shown in FIG. 2, a plurality of sensor cells are arranged (arranged) in the biaxial direction. A plurality of row lines (word lines, scanning lines) and a plurality of column lines (data lines) are provided. One of the row lines and the column lines may be one. For example, when there is one row line, a plurality of sensor cells are arranged in a direction (lateral direction) along the row line in FIG. On the other hand, when there is one column line, a plurality of sensor cells are arranged in a direction (vertical direction) along the column line.

  As shown in FIG. 9B, each sensor cell of the sensor array 500 is arranged (formed) at a location corresponding to the intersection position of each row line and each column line. For example, the sensor cell of FIG. 9B is disposed at a location corresponding to the intersection position of the row line WL1 and the column line DL1. The same applies to other sensor cells. The row selection circuit 510 is connected to one or more row lines. Then, each row line is selected. For example, taking a QVGA (320 × 240 pixel) sensor array 500 (focal plane array) as shown in FIG. 9B as an example, row lines WL0, WL1, WL2,... WL239 are sequentially selected (scanned). Perform the action. That is, a signal (word selection signal) for selecting these row lines is output to the sensor array 500.

  The read circuit 520 is connected to one or more column lines. Then, a read operation for each column line is performed. Taking the QVGA sensor array 500 as an example, an operation of reading detection signals (detection current, detection charge) from the column lines DL0, DL1, DL2,.

  The A / D conversion unit 530 performs a process of A / D converting the detection voltage (measurement voltage, ultimate voltage) acquired in the reading circuit 520 into digital data. Then, the digital data DOUT after A / D conversion is output. Specifically, the A / D converter 530 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 detection voltage acquired by the reading circuit 520 in the corresponding column line. Note that one A / D converter is provided corresponding to a plurality of column lines, and the detection voltage of the plurality of column lines can be A / D converted in a time division manner using this one A / D converter. Good.

  The control circuit 550 (timing generation circuit) generates various control signals and outputs them to the row selection circuit 510, the read circuit 520, and the A / D conversion unit 530. 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.

  FIG. 12 shows an example of a terahertz camera including the pyroelectric detector according to the present embodiment. The electromagnetic wave absorbing material of the above-described sensor device 410 is set so that the absorption wavelength is optimized by the terahertz wave, and an example in which the terahertz camera 1000 is configured in combination with the terahertz light irradiation unit is shown.

  The terahertz camera 1000 includes a control unit 1010, an irradiation light unit 1020, an optical filter 1030, an imaging unit 1040, and a display unit 1050. The imaging unit 1040 includes an optical system such as a lens (not shown) and a sensor device that optimizes the absorption wavelength of the electromagnetic wave absorber of the pyroelectric detector described above in the terahertz range.

  The control unit 1010 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 1020 includes a laser device that emits terahertz light (an electromagnetic wave having a wavelength in the range of 100 μm to 1000 μm) and an optical system, and irradiates the person 1060 to be inspected with terahertz light. The reflected terahertz light from the person 1060 is received by the imaging unit 1040 through the optical filter 1030 that allows only the spectral spectrum of the specific substance 1070 to be detected to pass. The image signal generated by the imaging unit 1040 is subjected to predetermined image processing by the image processing unit of the control unit 1010, and the image signal is output to the display unit 1050. The presence of the specific substance 1070 can be determined because the intensity of the received light signal varies depending on whether or not the specific substance 1070 is present in the clothes of the person 1060.

  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.

  The present invention can be widely applied to various pyroelectric detectors. Note that the wavelength of the electromagnetic wave to be detected is an effective technique particularly when the wavelength is a terahertz wave.

  100 base part (fixed part), 102 cavity part, 104 support part (post), 130, 140 etching stop film (reducing gas barrier layer), 200 pyroelectric detector, 210 support member, 211A first surface, 211B second surface , 212 1st layer member, 214 2nd layer member, 216 3rd layer member, 220 sensing element, 222 1st electrode wiring layer, 224 2nd electrode wiring layer, 222A 1st connection part, 224A 2nd connection part, 222B First lead wiring portion, 224B Second lead wiring portion, 226 First plug, 228 Second plug, 228A First layer (barrier metal layer), 230 capacitor, 232 pyroelectric body, 234 first electrode, 234A orientation control layer 234B First reducing gas barrier layer, 234C seed layer, 234D adhesion layer, 236 second electrode, 236A orientation Composite layer, 236B Second reducing gas barrier layer, 236C Low resistance layer, 240 reducing gas barrier layer, 250 interlayer insulating film, 260 interlayer insulating film (passivation film), 270 electromagnetic wave absorber (terahertz wave absorber), 280 reducing gas barrier layer (Etching stop film), 290 Reduction gas barrier layer, D1 first direction, D2 second direction, 1000 terahertz camera, 1020 irradiation light unit, 1040 imaging unit.

Claims (12)

A pyroelectric detection element for detecting a terahertz wave having a wavelength of 100 μm or more and 1000 μm or less;
A support member including a first surface and a second surface facing the first surface, the second surface facing the cavity, and mounting the pyroelectric detection element on the first surface;
A support part for supporting a part of the support member;
Have
The pyroelectric detection element is
A first electrode mounted on the support member; a second electrode; and a pyroelectric material disposed between the first and second electrodes, wherein the first electrode is formed by laminating the pyroelectric material. A capacitor that includes a first region and a second region that extends from the first region, the polarization amount of the capacitor changing based on temperature,
An interlayer insulating film covering the surface of the capacitor;
A first contact hole formed in the interlayer insulating film and leading to the second region of the first electrode;
A first plug embedded in the first contact hole;
A second contact hole formed in the interlayer insulating film and communicating with the second electrode;
A second plug embedded in the second contact hole;
A first electrode wiring layer formed on the interlayer insulating film and the support member and connected to the first plug;
A second electrode wiring layer formed on the interlayer insulating film and the support member and connected to the second plug;
Including
The terahertz camera characterized in that the thermal conductivity of the material forming the second electrode wiring layer is lower than the thermal conductivity of the material forming the second electrode in a portion connected to the second plug. In claim 1,
A terahertz camera, wherein a material forming the first electrode wiring layer has a thermal conductivity lower than that of a material forming the first electrode in a portion connected to the first plug. In claim 1 or 2,
At least one of the first electrode wiring layer and the second electrode wiring layer is formed of titanium nitride or titanium / aluminum / nitride. In any one of Claims 1 thru | or 3,
A terahertz camera, wherein the thermal conductance of the second electrode is larger than the thermal conductance of the first electrode. In any one of Claims 1 thru | or 4,
The pyroelectric detection element further includes an electromagnetic wave absorbing member formed in a region upstream of the second electrode and the second electrode wiring layer in the electromagnetic wave incident direction. In claim 5,
The electromagnetic wave absorbing member is formed to cover the entire surface of the second electrode in a plan view as viewed from the electromagnetic wave incident direction,
The terahertz camera, wherein the second electrode is formed so as to cover an entire surface of the pyroelectric material facing a surface in contact with the first electrode. In claim 5 or 6,
The terahertz, wherein the electromagnetic wave absorbing member is formed in a position overlapping each of the first region of the first electrode and at least a part of the second region of the first electrode in plan view. camera. In any of claims 5 to 7,
The first electrode wiring layer includes a first connection portion connected to the first plug, and a first lead-out wiring portion that is drawn from the first connection portion and is narrower than the first connection portion. ,
The second electrode wiring layer includes a second connection portion connected to the second plug, and a second lead-out wiring portion drawn out from the second connection portion and narrower than the second connection portion. ,
2. The terahertz camera according to claim 1, wherein a width of the second lead wiring portion is narrower than a maximum length of a cross section of the second contact hole. In claim 8,
A terahertz camera, wherein the width of the first lead wiring portion is narrower than the maximum length of the cross section of the first contact hole. In any one of Claims 1 thru | or 9,
A terahertz camera, further comprising a reducing gas barrier film between the interlayer insulating film and the capacitor.   A terahertz camera, wherein the pyroelectric detector according to any one of claims 1 to 10 is two-dimensionally arranged along two axial directions.   An electronic apparatus comprising the terahertz camera according to claim 1.