JP2012026860A - Pyroelectric photodetector and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection efficiency in a pyroelectric detector.
A pyroelectric detector 200 includes a lower electrode 234, a pyroelectric material layer 232 formed on the lower electrode, and an upper electrode 236 formed on the pyroelectric material layer. The electrode 234 includes a single material layer or a plurality of stacked material layers, and at least the uppermost layer of the single material layer or the stacked material layers also serves as a light absorption layer. The upper electrode 236 can be provided in a region covering the entire region of the pyroelectric material layer in plan view. In addition, at least the uppermost layer of the single material layer or the plurality of stacked material layers can also serve as a reducing gas barrier layer against a reducing gas that reduces the pyroelectric material 232. The reducing gas barrier layer can be formed on the side surface of the pyroelectric material layer 232.
[Selection] Figure 1

Description

  The present invention relates to a pyroelectric detector, an electronic device, and the like.

  A pyroelectric detector is known as a thermal detector. The pyroelectric detector detects an increase in the temperature of the light absorption film due to light absorption using, for example, a pyroelectric effect (pyroelectronic effect) of a ferromagnetic material. Crystals having a large dielectric constant, such as ferroelectrics (PZT: lead zirconate titanate) and lithium tantalate, change in the amount of electric polarization when heated or cooled. That is, if there is a change in temperature, the amount of spontaneous polarization changes, resulting in a change in the amount of surface charge. If there is no change in temperature, the surface charge is neutralized. As the polarization state changes, a pyroelectric current generated by a change in the surface charge amount flows between the electrodes connected to both ends of the ferroelectric crystal. By detecting the pyroelectric current (or the dielectric constant and the polarization amount accompanying the change in the polarization amount), the amount of the irradiated light (such as infrared rays) can be detected.

  An infrared detection element, which is one of the thermal detection elements, is applied to, for example, a human sensor in the small-scale element field, and is applied to, for example, an infrared camera device in the large-scale array field. In the past, it was developed as a military technology, but in recent years it has begun to be applied to consumer products, and various applications using infrared detection are expected in the future.

  A thin-film infrared detection element as a pyroelectric detector is described in Patent Document 1, for example. The thin-film infrared detection element described in Patent Document 1 has a structure in which a PZT film (reference numeral 10) is sandwiched between an upper electrode (reference numeral 12) and a lower electrode (reference numeral 8). An infrared absorption film (reference numeral 17) is provided.

JP 2008-232896 A

In the thin-film infrared detection element described in Patent Document 1, an upper electrode exists between the infrared absorption film and the PZT film. Therefore, the distance between the infrared absorption film and the PZT film inevitably increases.

  As described above, the heat generated in the infrared absorption film is transmitted to the PZT film, and the amount of electric polarization of the PZT film changes. In order to efficiently transfer the heat generated in the infrared absorption film to the PZT film, it is desirable to reduce the distance between the infrared absorption film and the PZT film. However, in Patent Document 1, as described above, there is a limit to shortening the distance between the infrared absorption film and the PZT film.

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

  (1) One aspect of the pyroelectric photodetector of the present invention includes a lower electrode, a pyroelectric material layer formed on the lower electrode, and an upper electrode formed on the pyroelectric material layer. The upper electrode includes a single material layer or a plurality of stacked material layers, and at least the uppermost layer of the single material layer or the stacked material layers is a light layer. A pyroelectric detector that also serves as an absorption layer.

  In this aspect, at least a part of the upper electrode constituting the pyroelectric detector is formed of a material layer having a high light absorption efficiency, and at least a part of the upper electrode also functions as a light absorption layer. That is, the upper electrode is constituted by a single layer material layer or a plurality of laminated material layers, and at least the uppermost layer of the single layer material layer or the laminated plurality of material layers is a light absorption layer. Also serves as.

  Since the upper electrode is formed in contact with the pyroelectric material layer (pyroelectric material), it is possible to dispose the light absorption layer constituting at least a part of the upper electrode in the vicinity of the pyroelectric material layer. is there. That is, the distance between the light absorption layer and the pyroelectric material layer can be minimized. Therefore, the heat generated in the light absorption layer can be transferred to the pyroelectric material layer most efficiently. Therefore, the detection efficiency in the pyroelectric detector can be improved.

  (2) In another aspect of the pyroelectric detector of the present invention, the upper electrode is provided in a region covering the entire region of the pyroelectric material layer in plan view.

  In this aspect, the upper electrode is provided so as to cover the entire region of the pyroelectric material layer in plan view. As a result, the contact area between the upper electrode and the pyroelectric material layer (pyroelectric body) increases, so that the thermal conductance in the heat transfer path increases (in other words, the thermal resistance decreases). Therefore, the heat generated in the light absorption layer constituting at least a part of the upper electrode can be more efficiently transferred to the pyroelectric material layer. Further, when the contact area between the upper electrode and the pyroelectric material layer (pyroelectric material) increases, the value of contact resistance (electrical resistance) decreases, which is advantageous in terms of electrical conduction.

  (3) In another aspect of the pyroelectric detector of the present invention, at least the uppermost layer of the single-layer material layer or the stacked material layers is a reduction that reduces the pyroelectric material. Also serves as a reducing gas barrier layer for gas.

  In this embodiment, a material having a reducing gas (for example, hydrogen gas) barrier property is further used as the material of the material layer constituting at least a part of the upper electrode. When an oxide such as PZT is exposed to a reducing gas (hydrogen or the like), the characteristics deteriorate and desired characteristics cannot be obtained. Therefore, in this aspect, a material having a high barrier property that prevents the reducing gas is selected as the material of the material layer constituting at least a part of the upper electrode, thereby preventing deterioration of characteristics of the pyroelectric material (pyroelectric material). can do.

  For example, a pyroelectric capacitor is covered with an insulating layer, a contact hole is opened in a part of the insulating layer, and a conductor layer (for example, an extraction electrode) connected to the upper electrode through the contact hole is formed. A case is assumed in which a tungsten plug constituting a part is formed. In this case, for example, when a contact hole is opened or a tungsten plug is buried, hydrogen gas (reducing gas or deteriorated gas that deteriorates the characteristics of the pyroelectric capacitor) may enter. In addition, even after the tungsten plug is completed, the tungsten plug does not particularly have a reducing gas barrier function, so that the reducing gas may pass through the tungsten plug and enter the pyroelectric material layer (pyroelectric body) side. obtain.

  However, according to this aspect, since the material layer (material film) having the reducing gas barrier ability exists on at least the uppermost surface of the upper electrode, the pyroelectric material layer (pyroelectric material) is reliably deteriorated in characteristics. Is prevented. Therefore, the reliability of the pyroelectric capacitor is improved.

  (4) In another aspect of the pyroelectric detector of the present invention, a reducing gas barrier is formed on a side surface of the pyroelectric material layer.

  As described above, at least the uppermost layer of the upper electrode has a material layer (material film) having a reducing gas barrier capability, but the material layer alone prevents the intrusion of the reducing gas from the side surface portion of the pyroelectric material layer. It cannot be stopped. Therefore, in this embodiment, a reducing gas barrier layer (having at least one reducing gas barrier layer) is formed only on the side surface of the pyroelectric material layer. As a result, it is possible to reliably prevent deterioration of characteristics due to intrusion of reducing gas from the side surface of the pyroelectric capacitor.

  (5) In another aspect of the pyroelectric detector of the present invention, at least the uppermost layer of the single-layer material layer or the stacked multiple-layer material layers is made of silicon carbide (SiC) or aluminum nitride. It is a layer mainly composed of (AlN).

  Both silicon carbide (SiC) and aluminum nitride (AlN) exhibit absorption characteristics with respect to light having a wavelength of about 8 μm to 12 μm, for example. Therefore, it can be used as a light absorption layer. Moreover, both can ensure the heat conductivity of about 60-320 W / m * k. In both cases, barrier properties against reducing gas are observed. Moreover, for example, about 0.3 to 1.3 (Ω · cm) can be secured, for example, as the specific resistance of SiC (one index of electrical resistance). In the case of AlN, the electrical conductivity is inferior to that of SiC, but the characteristics as a conductor can be ensured. Therefore, both materials have characteristics as an electrode layer, a light absorption layer, a heat transfer layer, and a reducing gas barrier layer.

  The layer mainly composed of silicon carbide (SiC) or aluminum nitride (AlN) can be formed by, for example, a sputtering method or a CVD method. For example, when a SiC target is used as the sputtering target, the target contains trace amounts of other metals such as B, Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn. May be. However, if silicon carbide (SiC) is the main component, necessary characteristics can be ensured. The same applies to AlN.

  In addition, the expression “mainly composed of silicon carbide (SiC) or aluminum nitride (AlN)” means that other materials such as metals are positively added when the material layer is formed. It is not excluded. For Al, an oxide (AlO) may be used.

  (6) In another aspect of the pyroelectric detector of the present invention, the upper electrode includes a first layer and a second layer as the stacked material layers, and the first layer includes the first layer It is the uppermost layer, and the second layer is a layer having Pt (platinum) or iridium (Ir) as a main component and having light reflection characteristics.

  In this embodiment, the upper electrode is composed of two material layers, and the lower layer is composed of a material layer mainly composed of Pt or Ir. As a result, a layer having a light reflection characteristic (light reflection layer) can be formed immediately below the light absorption layer. In this aspect, since there is a light absorption layer (a material layer that functions as) in the vicinity of the light reflection layer, there is an effect that the reflected light is efficiently absorbed by the light absorption layer and converted into heat.

  (7) In the pyroelectric detector of the present invention, the upper electrode is composed of the single-layer material layer, and the lower electrode is a single-layer lower electrode material layer or laminated. It is composed of a plurality of lower electrode material layers, and at least the uppermost layer of the single layer lower electrode material layer or the stacked multiple layers of lower electrode material layers is Pt (platinum). Alternatively, the light-reflecting layer is mainly composed of iridium (Ir).

  In this embodiment, the upper electrode is composed of a single material layer, while the lower electrode is composed of a material layer mainly composed of Pt or Ir. In the case of this structure, light coming from above the pyroelectric capacitor may be reflected by the lower electrode and incident on the light absorption layer (the material layer functioning as the upper electrode). Therefore, the amount of light absorbed by the light absorption layer can be increased. Further, by adjusting the thickness of the pyroelectric material layer (pyroelectric body) and setting the distance between the upper electrode and the lower electrode to ¼ of the wavelength λ of the light to be detected, due to the resonance of the light, The amount of light absorbed by the light absorption layer can be positively increased.

  (8) In another aspect of the pyroelectric detector of the present invention, an insulating film is formed on the upper electrode, a conductor layer is formed on the insulating film, and the conductor layer is formed of the insulating film. Is connected to the upper electrode through a contact hole formed in a part of the upper electrode, and at least the uppermost layer of the single layer material layer or the stacked material layers of the upper electrode is Etching resistance against etchant for forming contact hole.

  In this embodiment, the uppermost surface of the upper electrode also functions as an etching stopper when forming the contact hole. For example, a pyroelectric capacitor is covered with an insulating layer, a contact hole is opened in a part of the insulating layer, and a conductor layer (for example, an extraction electrode) connected to the upper electrode through the contact hole is formed. A case is assumed in which a tungsten plug constituting a part is formed. In the etching process when a contact hole is provided in a part of the insulating layer covering the pyroelectric capacitor, the uppermost surface of the upper electrode functions as an etching stopper, so that over-etching (the etching proceeds more than necessary) is surely prevented. Therefore, the manufacturing burden is reduced.

  (9) In another aspect of the pyroelectric detector of the present invention, a part of the upper electrode also serves as a wiring for connecting the upper electrode to another circuit component, and the lower electrode An insulating film is formed on at least a side surface of the pyroelectric capacitor constituted by the electrode, the pyroelectric material layer, and the upper electrode, and the wiring is formed on the insulating film formed on at least the side surface of the pyroelectric capacitor. It is arranged.

  For example, the wiring is disposed so as to pass on the side surface of the pyroelectric capacitor and reach a support member (for example, a membrane) on which the pyroelectric capacitor is mounted. In this case, heat is transmitted to the lower part of the pyroelectric capacitor via the wiring (metal), and part of the heat is also transmitted to the pyroelectric material layer. Therefore, according to this aspect, the heat generated in the light absorption layer (the material layer that functions as) can be more efficiently transferred to the pyroelectric material layer (pyroelectric body).

  (10) One aspect of the electronic device of the present invention includes any one of the above pyroelectric detectors.

  Since the detection efficiency of the pyroelectric detector is increased, the performance of an electronic device equipped with the pyroelectric detector is also improved.

1A to 1C are diagrams showing a structural example of a pyroelectric detector and a structural example of a comparative example. 2A to 2E are diagrams showing an example of a manufacturing method of the pyroelectric detector shown in FIG. 3 (A) to 3 (E) are diagrams showing an example of a method for manufacturing the pyroelectric detector shown in FIG. 1 (B). Plan view showing layout configuration of pyroelectric detection device Sectional drawing which shows the structural example of the pyroelectric detector shown by FIG. 6A and 6B are diagrams illustrating an example of a method for forming a cavity (thermal separation cavity). 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 always.

(First embodiment)
1A to 1C are diagrams illustrating a structural example of a pyroelectric detector and a structural example of a comparative example. 1A and 1B show an example of the structure of a pyroelectric detector according to this embodiment, and FIG. 1C shows a comparative example (a pyroelectric detector according to this embodiment. This is a comparative example for clarifying the characteristics of the structure, and is not a conventional example.

First, reference is made to FIG. A pyroelectric detector 200 shown in FIG. 1A includes a pyroelectric photodetector (for example, a pyroelectric infrared detector) 220 formed on a support member (membrane) 210. The pyroelectric detection element 220 includes a pyroelectric capacitor 230. Note that the support member (membrane) 210 can be constituted by, for example, a laminated film of three layers of Si ₃ N ₄ film / SiO ₂ film / Si ₃ N ₄ film. The support member (membrane) 210 needs to stably support the pyroelectric detection element 220, and therefore the total thickness of the support member (membrane) 210 is set to satisfy the required mechanical strength. ing.

  The pyroelectric capacitor 230 includes a lower electrode (first electrode) 234, a pyroelectric material layer (pyroelectric material: PZT layer) 232 formed on the lower electrode, and an upper electrode formed on the pyroelectric material layer 232. (Second electrode) 236. In the example of FIG. 1A, the upper electrode 236 is composed of a single-layer material layer, and the single-layer upper electrode 236 is a material layer that also serves as a light absorption film and a reducing gas barrier film.

  Further, the upper electrode 236 is provided in a region covering the entire region of the pyroelectric material layer 232 in plan view (this is the same as in the example of FIG. 1B). In FIG. 1A, a plan view is not shown. However, since the upper electrode 236 is formed so as to cover the pyroelectric capacitor 230, the upper electrode 236 is formed in a pyroelectric material in plan view. Obviously, the layer 232 is provided in a region covering the entire region.

  The upper electrode 236 can be composed of a layer mainly composed of silicon carbide (SiC) or aluminum nitride (AlN).

  Both silicon carbide (SiC) and aluminum nitride (AlN) exhibit absorption characteristics with respect to light having a wavelength of about 8 μm to 12 μm, for example. Therefore, it can be used as a light absorption layer. Moreover, both can ensure the heat conductivity of about 60-320 W / m * k. In addition, barrier properties against a reducing gas (hydrogen gas or the like) are recognized. Moreover, for example, about 0.3 to 1.3 (Ω · cm) can be secured, for example, as the specific resistance of SiC (one index of electrical resistance). In the case of AlN, the electrical conductivity is inferior to that of SiC, but the characteristics as a conductor can be ensured. Therefore, both materials have characteristics as an electrode layer, a light absorption layer, a heat transfer layer, and a reducing gas barrier layer.

  The layer mainly composed of silicon carbide (SiC) or aluminum nitride (AlN) can be formed by, for example, a sputtering method or a CVD method. For example, when a SiC target is used as the sputtering target, the target contains trace amounts of other metals such as B, Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn. May be. However, if silicon carbide (SiC) is the main component, necessary characteristics can be ensured. The same applies to AlN.

  In addition, the expression “mainly composed of silicon carbide (SiC) or aluminum nitride (AlN)” means that other materials such as metals are positively added when the material layer is formed. It is not excluded. For Al, an oxide (AlO) may be used.

In the example of FIG. 1A, a sidewall layer 240 is formed on the side surface of the pyroelectric capacitor 230. The sidewall layer 240 includes at least one reducing gas barrier layer (for example, an Al ₂ O ₃ film) 242 and an insulating layer (for example, an SiO ₂ film or an Si ₃ N ₄ film) 244.

  The pyroelectric capacitor 230 is covered with an interlayer insulating film 250. A part of the interlayer insulating film 250 is opened to form a contact hole 254, and electrical conduction between the extraction electrode 228 and the upper electrode 236 is ensured through the contact hole 254. The lead electrode 228 includes a contact plug (for example, a tungsten plug) 228a and an electrode 228b.

The lower electrode (first electrode) 234 is formed by laminating, for example, 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. 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.

  Light incident from above the pyroelectric capacitor 230 is absorbed by the upper electrode 236 (which also functions as a light absorption layer) and converted into heat. This heat is transmitted to the pyroelectric material layer (pyroelectric body) 232, and as a result, a change in the amount of electric polarization occurs in the pyroelectric material layer (pyroelectric body) 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.

  Next, an example of FIG. 1B will be described. Note that, in FIG. 1B, parts that are the same as those in the example of FIG. 1A are denoted by the same reference numerals (this is the same in the following drawings). In the example of FIG. 1B, the upper electrode (second electrode) 236 ′ includes a lower material layer 235 (described as the upper electrode (1) in FIG. 1B) and an upper material layer. 236 (described as an upper electrode (2) in FIG. 1B) is laminated. The structure of other parts is the same as the example of FIG.

  In the example of FIG. 1B, the upper electrode 236 ′ includes a lower material layer 235 and an upper (uppermost) material layer 236. The upper material layer 236 (upper electrode (1)) is a layer having light reflection characteristics, for example, containing Pt (platinum) or iridium (Ir) as a main component. Further, as described above, the upper material layer 236 (upper electrode (2)) is a material layer that also serves as a light absorption film and a reducing gas barrier film. For example, silicon carbide (SiC) or aluminum nitride (AlN) It is comprised by the layer which has as a main component.

In the comparative example shown in FIG. 1C, the upper electrode is a material layer such as Pt or Ir, a reducing gas barrier layer (for example, an Al ₂ O ₃ film) 242 and an insulating layer (for example, SiO _2). Film 244 or Si ₃ N ₄ film) 244 is formed so as to cover pyroelectric capacitor 230 ′. A contact hole 255 is formed in the insulating layer 250. In the comparative example shown in FIG. 1C, an insulating layer 301 is provided, and a light absorption film (for example, a thick SiO ₂ film) 303 is formed over the insulating layer 301.

  Next, advantages of the pyroelectric detector according to the present embodiment shown in FIGS. 1A and 1B will be described in comparison with the comparative example of FIG.

  In the example of FIGS. 1A and 1B, at least a part of the upper electrode 236 (or 236 ′) constituting the pyroelectric photodetector 200 (pyroelectric detection element 220) is absorbed by light. It is composed of a material layer having high efficiency, and at least a part of the upper electrode also functions as a light absorption layer. That is, the upper electrode is configured by a single material layer (example in FIG. 1A) or a plurality of stacked material layers (example in FIG. 1B). Therefore, at least the uppermost layer of the single-layer material layer or the plurality of stacked material layers also serves as the light absorption layer.

  Since the upper electrode (236 or 236 ′) is formed in contact with the pyroelectric material layer (pyroelectric body) 232, the light absorption layer 236 constituting at least a part of the upper electrode is formed on the pyroelectric material layer 232. It is possible to arrange them in close proximity. That is, the distance between the light absorption layer 236 and the pyroelectric material layer 232 can be minimized. Therefore, the heat generated in the light absorption layer 236 can be transferred to the pyroelectric material layer 232 most efficiently. Therefore, the detection efficiency in the pyroelectric detector 200 can be improved.

  In contrast, in the comparative example shown in FIG. 1C, the upper electrode 231 exists between the light absorption film 303 and the pyroelectric material layer 232. Therefore, there is a limit to shortening the distance between the light absorption film 303 and the pyroelectric material layer 232. In the comparative example shown in FIG. 1C, the height of the pyroelectric detection element is increased by the amount of the light absorption film 303, but in the example of FIGS. 1A and 1B, In addition, since it is not necessary to provide the light absorption film 303 separately, the height of the pyroelectric detection element can be suppressed accordingly.

  In the example of FIGS. 1A and 1B, as described above, the material layer 236 constituting at least the uppermost layer of the upper electrode is a region covering the entire region of the pyroelectric material layer in plan view. Is provided. As a result, the contact area between the material layer 236 constituting at least the uppermost layer of the upper electrode and the pyroelectric material layer (pyroelectric body) 232 is increased, so that the thermal conductance in the heat transfer path is increased (in other words, , Thermal resistance is reduced). Therefore, heat generated in the material layer 236 (also serving as the light absorption layer) constituting at least the uppermost layer of the upper electrode can be more efficiently transferred to the pyroelectric material layer 232. Further, when the contact area between the upper electrode 236 (236 ′) and the pyroelectric material layer (pyroelectric body) 232 increases, the value of contact resistance (electrical resistance) decreases, which is advantageous in terms of electrical conduction. Become.

  In the example of FIGS. 1A and 1B, the material layer 236 constituting at least the uppermost layer of the upper electrode (that is, of the single-layer material layer 236 or a plurality of stacked material layers) At least the uppermost layer 236) also serves as a reducing gas barrier layer for a reducing gas (such as hydrogen gas) that reduces the pyroelectric material (such as PZT). As described above, when an oxide such as PZT is exposed to a reducing gas (hydrogen or the like), the characteristics deteriorate and desired characteristics cannot be obtained. By selecting a material having a high barrier property that inhibits reducing gas as the material of the material layer 236 constituting at least the uppermost layer of the upper electrode, it is possible to prevent deterioration of the characteristics of the pyroelectric material (pyroelectric material).

  In the example of FIGS. 1A and 1B, the pyroelectric capacitor 230 is covered with an insulating layer 250, and a contact hole 254 is opened in a part of the insulating layer 250. Thus, a conductor layer (for example, a tungsten plug 228a constituting a part of the extraction electrode) connected to the upper electrode is formed. When the contact hole 254 is opened or the tungsten plug 228a is buried, hydrogen gas (reducing gas or deteriorated gas that deteriorates the characteristics of the pyroelectric capacitor) may enter. Further, even after the tungsten plug 228a is completed, the tungsten plug 228a does not particularly have a reducing gas barrier function, and therefore, the reducing gas passes through the tungsten plug and enters the pyroelectric material layer (pyroelectric body) side. There is also a possibility.

  However, in the example of FIGS. 1A and 1B, since there is a material layer (material film) 236 having a reducing gas barrier capability on at least the uppermost surface of the upper electrode, the pyroelectric material layer ( The deterioration of the characteristics of the pyroelectric body 232 is reliably prevented. Therefore, the reliability of the pyroelectric capacitor 230 is improved.

  In the example of FIGS. 1A and 1B, the reducing gas barrier layer 242 is formed on the side surface of the pyroelectric material layer 232 (that is, the sidewall layer 240 including the reducing gas barrier layer 242 is formed). Formed).

  As described above, in the example of FIGS. 1A and 1B, the material layer (material film) 236 having the reducing gas barrier ability exists in at least the uppermost layer of the upper electrode. It is not possible to prevent the intrusion of the reducing gas from the side surface portion of the pyroelectric material layer 232 alone. Therefore, in the example of FIGS. 1A and 1B, a reducing gas barrier layer (having at least one reducing gas barrier layer 242) is formed on the side surface of the pyroelectric material layer 232 (only on the side surface). Accordingly, it is possible to reliably prevent deterioration of characteristics due to intrusion of the reducing gas from the side surface of the pyroelectric capacitor 230.

  In the example of FIG. 1B, the upper electrode is formed by laminating a plurality of material layers, and Pt (platinum) or iridium (Ir) is the main component immediately below the uppermost material layer 236. A lower material layer 235 having light reflection characteristics is formed. Therefore, a layer (light reflection layer) 235 having light reflection characteristics can be formed immediately below the light absorption layer 236. That is, since there is the light absorption layer (a material layer that functions as) 236 in the vicinity of the light reflection layer 235, the effect that the reflected light is efficiently absorbed by the light absorption layer 236 and converted into heat is obtained. .

  In the example of FIG. 1A, the upper electrode is formed of a single material layer 236. On the other hand, at least the uppermost layer of the single-layer lower electrode material layer constituting the lower electrode 234 or the stacked plural layers of lower electrode material layers is mainly made of Pt (platinum) or iridium (Ir). It is composed of a layer having light reflection characteristics as a component.

  In the case of this structure, light coming from above the pyroelectric capacitor 230 may be reflected by the uppermost surface of the lower electrode 234 and enter the upper electrode (that is, the material layer functioning as a light absorption layer) 236. Therefore, the amount of light absorbed by the light absorption layer 236 can be increased. Further, by adjusting the thickness of the pyroelectric material layer (pyroelectric body) 232 and setting the distance between the upper electrode 236 and the lower electrode 234 to ¼ of the wavelength λ of the light to be detected, The amount of light absorbed by the light absorption layer 236 can be positively increased by resonance.

  Next, the manufacturing method of the example of FIG. 1 (A) and FIG. 1 (B) is demonstrated. 2A to 2E are diagrams illustrating an example of a manufacturing method of the pyroelectric detector shown in FIG.

  In the step shown in FIG. 2A, a lower electrode 234 and a pyroelectric material layer 232 are sequentially stacked on a support member (membrane) 210, and a reducing gas barrier layer 242 and an insulating layer 244 are sequentially stacked. Form. 2B, a part of the reducing gas barrier layer 242 and the insulating layer 244 are removed by anisotropic etching such as RIE (reactive ion etching). As a result, a sidewall layer 240 is formed.

  In the step of FIG. 2C, an upper electrode (light absorption film / reducing gas barrier film combined layer) 236 is formed. In the step of FIG. 2D, an insulating film 250 (interlayer insulating film) 250 is formed, and a part of the insulating film 250 is opened to form a contact hole 254. In the step of FIG. 2D, the extraction electrode 228 (including the contact plug 228a and the top electrode 228b) is formed.

  Next, the manufacturing method shown in FIG. 3 will be described. FIG. 3A to FIG. 3E are diagrams showing an example of a manufacturing method of the pyroelectric detector shown in FIG.

  The processes in FIGS. 3A and 3B correspond to the processes in FIGS. 2A and 2B described above, and are the same processes. In the step of FIG. 3C, an upper electrode (1) (a layer containing Pt or Ir as a main component) 235 and an upper electrode (2) (light absorption film / reducing gas barrier film combined layer) 236 are formed. Thereby, the upper electrode 236 'is formed. The processes of FIGS. 3D and 3E correspond to the processes of FIGS. 2D and 2E described above, and are the same processes.

  Thus, when manufacturing an optical sensor using the pyroelectric effect, a material having absorption characteristics for light such as infrared rays (more preferably, as the uppermost layer of a single layer upper electrode or a plurality of upper electrodes) Can improve the light detection efficiency in the pyroelectric detector by using a material layer made of a material having a high thermal conductivity, high conductivity, and a reducing gas barrier ability.

(Second Embodiment)
In the present embodiment, the configuration and the like of a pyroelectric detection device in which pyroelectric detectors are two-dimensionally arranged will be described.

1. Layout Configuration of Pyroelectric Photodetector FIG. 4 is a plan view showing the layout configuration of the pyroelectric detector. In FIG. 4, a plurality of posts 104 are erected from a base (or fixed portion) 100 and are supported by, for example, two posts (a pair of posts) 104 (for example, a pyroelectric infrared detector). ) 200 are arranged in a plurality of orthogonal biaxial directions. This constitutes a pyroelectric detector array. The area of the area occupied by the pyroelectric detector 200 for one cell is, for example, 30 μm × 30 μm.

  As shown in FIG. 4, the pyroelectric detector 200 includes a support member (membrane) 210 connected to two posts 104, a pyroelectric photodetector (for example, a pyroelectric infrared detector) 220, and the like. , Including. The area of the area occupied by the pyroelectric detection element 220 for one cell is, for example, 10 μm × 10 μm.

  The pyroelectric photodetector (pyroelectric infrared detector) 200 for one cell is not contacted except that it is connected to the two posts 104, and a hollow portion is provided below the pyroelectric photodetector 200. 102 (see FIG. 5) is formed, and an opening 102A communicating with the cavity 102 is disposed around the pyroelectric detector 200 in plan view. Thereby, 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 (membrane) 210 has a mounting part 210A for mounting and supporting the pyroelectric light detection element 220, and two arms 210B connected to the mounting part 210A, and the two arms 210B. Is connected to the post 104. The two arms 210 </ b> B are narrow and redundantly extended to thermally separate the pyroelectric detection element 220.

  FIG. 4 is a plan view in which members above the wiring layer connected to the upper electrode are omitted. FIG. 4 shows a wiring layer for the lower electrode (first electrode) connected to the pyroelectric detection element 220. 222 and a wiring layer 224 for the upper electrode (second electrode) are shown. Each of the wiring layers 222 and 224 extends along the arm 210B, and is connected to a circuit (not shown) in the base 100 via the post 104. Each of the electrode wiring layers 222 and 224 is also formed to extend narrowly and redundantly in order to thermally separate the pyroelectric detection element 220.

2. Example Structure of Pyroelectric Detector FIG. 5 is a sectional view showing an example structure of the pyroelectric detector shown in FIG. As shown in FIG. 5, the base 100 includes a substrate, for example, a silicon substrate 110, and a spacer layer formed of an interlayer insulating film on the silicon substrate 110 (for example, a plurality of layers are laminated like a multilayer wiring structure). Layer 120). The post 104 is formed by etching the spacer layer 120. A plug 106 connected to one of the wiring layers 222 and 224 can be disposed on the post 104. The plug 106 is connected to, for example, a row selection circuit (row driver: not shown) provided on the silicon substrate 110 or a readout circuit (not shown) that reads data from the photodetector 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. 4 is formed by pattern-etching the support member (membrane) 210.

  The pyroelectric detection element 220 mounted on the support member (membrane) 210 includes a pyroelectric capacitor 230. The pyroelectric capacitor 230 includes a pyroelectric body 232, a lower electrode (first electrode) 234 connected to the lower surface of the pyroelectric body 232, and an upper electrode (second electrode) 236 connected to the upper surface of the pyroelectric body 232. Including.

A side wall layer 240 is formed on the side surface of the pyroelectric capacitor 230. The sidewall layer 240 includes a reducing gas barrier layer 242 and an insulating film (SiO ₂ , Si ₃ N _4, etc.) 244. In FIG. 5, the membrane having the reducing gas barrier ability is shown by a thick solid line.

  An interlayer insulating film 250 is formed on the pyroelectric capacitor 230. 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. At least the uppermost layer of the upper electrode 236 has a reducing gas barrier capability, and a side wall layer 240 having a reducing gas barrier capability is provided on the side surface of the pyroelectric capacitor 230. Therefore, the pyroelectric capacitor 230 is not deteriorated by the reducing gas generated during the formation of the interlayer insulating film 250.

  A wiring layer 222 for a lower electrode (first electrode) and a wiring layer 224 for an upper electrode (second electrode) are disposed on the interlayer insulating film 250. 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. The first electrode (lower electrode) 234 and the first electrode wiring layer 222 are electrically connected by the first contact plug 226a 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 contact plug 228a embedded in the second contact hole 254.

  As described above, the uppermost surface of the upper electrode 236 also functions as an etching stopper when the second contact hole 254 is formed. When the second contact hole 254 is provided in a part of the interlayer insulating film 250, the uppermost surface of the upper electrode 236 functions as an etching stopper in the etching process, so that overetching (etching progresses more than necessary and the pyroelectric capacitor For example, part of 230 is removed by etching). Therefore, the manufacturing burden is reduced.

  In FIG. 5, an interlayer insulating film 250 is formed on at least the side surface of the pyroelectric capacitor 230, and a wiring layer 224 for the upper electrode (second electrode) is disposed on the interlayer insulating film 250. . In the example of FIG. 5, the wiring layer 224 is disposed so as to pass over the left side surface of the pyroelectric capacitor 230 and reach the support member (for example, membrane) 210 on which the pyroelectric capacitor 230 is mounted. Is done. According to this structure, heat is transmitted below the pyroelectric capacitor 230 via the wiring layer 224 (metal), and as a result, part of the heat is also transmitted to the pyroelectric material layer (PZT layer) 232. Therefore, heat generated in the material layer functioning as the light absorption layer of the upper electrode 236 can be more efficiently transferred to the pyroelectric material layer (PZT layer) 232.

  In FIG. 5, reference numeral 130 is an etching stop film provided on the surface (bottom surface and side surface) 100 </ b> A of the cavity (thermal separation cavity) 102, and reference numeral 140 is a support member (membrane) 210. It is an etching stop film | membrane provided in the back surface.

  FIGS. 6A and 6B are diagrams illustrating an example of a method for forming a cavity (thermal separation cavity). As shown in FIG. 6A, in the manufacturing process of the pyroelectric detector 200, a sacrificial layer 150 is embedded in the cavity (thermal separation cavity) 102. A support member (membrane) 210 is formed on the sacrificial layer 150, and a pyroelectric detection element 220 is formed on the support member (membrane) 210. Next, as shown in FIG. 6B, the sacrificial layer 150 is removed by isotropic etching. As a result, a cavity (thermal separation cavity) 102 is formed, and the pyroelectric detection element 220 is thermally separated from the base 100.

(Third embodiment)
FIG. 7 is a diagram illustrating an example of the configuration of an electronic device. The electronic device in FIG. 7 is, for example, an infrared camera. As illustrated, the electronic apparatus includes an optical system 400, a sensor device (thermal detector) 410 (reference numeral 200 in the above-described embodiment), an image processing unit 420, a processing unit 430, and a storage unit. 440, an operation unit 450, and a display unit 460. Note that the electronic apparatus according to the present embodiment is not limited to the configuration shown in FIG. 7, 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 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 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, since the detection efficiency of the sensor device 410 (pyroelectric photodetector 200) is increased, the performance of the electronic device in which the sensor device 410 is mounted is also improved.

  FIG. 8 is a diagram illustrating another example of the configuration of the electronic device. An electronic apparatus 800 in FIG. 8 includes a sensor unit 600 on which a thermal detector 200 and an acceleration detection element 500 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.

  As described above, according to at least one embodiment of the present invention, for example, detection efficiency in a pyroelectric detector can be 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. For example, the constituent material of the support member (membrane), the formation method thereof, and the like can be variously modified.

200 pyroelectric detector (thermal detector), 210 support member (membrane),
220 Pyroelectric detection element (infrared sensor element, etc.),
230 Pyroelectric capacitor, 234 Lower electrode,
232 Pyroelectric material layer (pyroelectric material: PZT layer, etc.),
236 Upper electrode (upper electrode / light absorption film / reducing gas barrier film combined layer)
250 insulating film, 228a contact plug, 228b electrode,
228 extraction electrode (or wiring),
252 and 254 contact holes (first contact hole, second contact hole)

Claims (10)

A lower electrode;
A pyroelectric material layer formed on the lower electrode;
An upper electrode formed on the pyroelectric material layer,
The upper electrode is constituted by a single material layer or a plurality of laminated material layers,
A pyroelectric detector, wherein at least an uppermost layer of the single-layer material layer or the plurality of stacked material layers also serves as a light absorption layer. The pyroelectric detector according to claim 1,
The pyroelectric detector, wherein the upper electrode is provided in a region covering the entire region of the pyroelectric material layer in plan view. The pyroelectric detector according to claim 1 or 2, wherein
At least the uppermost layer of the single-layer material layer or the stacked plural-layer material layers also serves as a reducing gas barrier layer for a reducing gas that reduces the pyroelectric material. . The pyroelectric detector according to claim 3, wherein
A pyroelectric detector, wherein a reducing gas barrier layer is formed on a side surface of the pyroelectric material layer. The pyroelectric detector according to any one of claims 1 to 4, wherein
The pyroelectric layer characterized in that at least the uppermost layer of the single-layer material layer or the stacked material layers is a layer mainly composed of silicon carbide (SiC) or aluminum nitride (AlN). Type photodetector. The pyroelectric detector according to any one of claims 1 to 5,
The upper electrode includes a first layer and a second layer as the plurality of stacked material layers, the first layer is the uppermost layer, and the second layer is made of Pt (platinum) or iridium ( A pyroelectric detector characterized by being a layer having Ir as a main component and having light reflection characteristics. The pyroelectric detector according to claim 5, wherein
The upper electrode is composed of the single material layer,
The lower electrode is composed of a single-layer lower electrode material layer or a plurality of stacked lower electrode material layers, and the single-layer lower electrode material layer or the stacked multiple layers A pyroelectric detector, wherein at least the uppermost layer of the lower electrode material layer is a layer having Pt (platinum) or iridium (Ir) as a main component and having light reflection characteristics. The pyroelectric detector according to any one of claims 1 to 7,
An insulating film is formed on the upper electrode, a conductor layer is formed on the insulating film, and the conductor layer is connected to the upper electrode through a contact hole formed in a part of the insulating film. And at least an uppermost layer of the single layer material layer or the plurality of stacked material layers in the upper electrode has etching resistance to the etchant for forming the contact hole. Type photodetector. A pyroelectric detector according to any one of claims 1 to 8, comprising:
A part of the upper electrode also serves as a wiring for connecting the upper electrode to other circuit components, and also includes a pyroelectric capacitor constituted by the lower electrode, the pyroelectric material layer, and the upper electrode. An insulating film is formed on at least a side surface of the pyroelectric detector, and the wiring is disposed on the insulating film formed on at least the side surface of the pyroelectric capacitor.   An electronic apparatus comprising the pyroelectric detector according to claim 1.

Images