Infrared sensor

Abstract

An infrared sensor (1) is provided with a semiconductor substrate (10), an insulating layer (20), an infrared reflection structure (30), a light receiving unit (40), a hollow support unit (50), and a thermoelectric conversion unit. The insulating layer (20) is located on the upper surface (11) of the semiconductor substrate (10). The infrared reflective structure (30) is provided in the insulating layer (20). The light receiving part (40) is located above the infrared reflection structure (30). The hollow support section (50) hollowly supports the light receiving section (40) such that a gap (51) is formed between the infrared reflection structure (30) and the light receiving section (40). The thermoelectric conversion unit generates an infrared detection signal on the basis of heat generated by the light receiving unit (40). The infrared reflecting structure (30) is configured from a plurality of metal vias (31) extending in the thickness direction of the insulating layer (20) in the insulating layer (20).

Description

Technical Field

[0001] The present disclosure relates to an infrared sensor. Background Art

[0002] Thermal infrared sensors are known that detect infrared rays by utilizing heat generated by a light receiving portion receiving infrared rays. Thermal infrared sensors are used, for example, in infrared imaging elements. For example, an infrared imaging element can be formed by arranging thermal infrared sensors as pixels in an array. If the heat capacity of the infrared light receiving portion of each pixel is reduced, the ability to follow changes in the power of the irradiated infrared rays becomes better, and high-speed imaging can be performed. In the case where the light receiving portion is formed of a thin film, the heat capacity can be reduced by reducing the area and thickness of the thin film.

[0003] However, if the area of ​​the light receiving part is reduced, the infrared power that can be absorbed by receiving light becomes weak. Moreover, if a light receiving part with a small area is used, it is difficult to obtain a temperature difference in space. In an infrared sensor (such as a thermopile type infrared sensor) that uses the Seebeck effect, that is, the electromotive force based on the temperature difference as a detection signal of infrared rays, if the temperature difference becomes smaller, the electromotive force becomes weak, and the S / N (Signal / Noise) ratio decreases. In response to this issue, in Patent Document 1, in an infrared sensor, the light receiving part is hollow supported by a hollow support part having a phononic crystal structure with excellent thermal insulation. In this way, the temperature difference in space can be maintained, and the reduction in S / N can be suppressed. Specifically, in a thermopile structure including a substrate, a light receiving part separated from the substrate, and a hollow support part that supports the light receiving part while separating the light receiving part from the substrate, a phononic crystal structure is provided in the hollow support part, a cold junction (cold contact point) is provided on the substrate side, and a hot junction (hot contact point) is provided on the light receiving part side. As a result, the hot junction temperature and the cold junction temperature on the light receiving part whose temperature changes due to infrared radiation do not immediately become uniform, but the temperature difference between the hot junction and the cold junction is maintained, and the electromotive force generated by the Seebeck effect can be effectively obtained.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 225058

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 6-318573

[0008] Non-patent literature

[0009] Non-patent literature 1: S.Basu, BJLee and M.Zhang, "Infrared Radiative Properties of Heavily Doped Silicon at Room Temperature", Journal of Heat Transfer, Vol.132, FEBRUARY 2010. Summary of the invention

[0010] In the present disclosure, an infrared sensor capable of improving the detection accuracy of infrared rays is provided.

[0011] An infrared sensor of one embodiment of the present disclosure comprises: a substrate; an insulating layer located on the upper surface of the substrate; a first infrared reflection structure arranged in the insulating layer; a light receiving portion located above the first infrared reflection structure; a hollow supporting portion for hollow-supporting the light receiving portion so that a gap is formed between the first infrared reflection structure and the light receiving portion; and a thermoelectric conversion portion for generating an infrared detection signal based on heat generated by the light receiving portion, wherein the first infrared reflection structure is composed of a plurality of first metal vias extending in the insulating layer along the thickness direction of the insulating layer.

[0012] According to the present disclosure, it is possible to improve the detection accuracy of infrared rays. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view showing an infrared sensor of a comparative example.

[0014] Figure 2A This is a cross-sectional view showing the infrared sensor according to the first embodiment.

[0015] Figure 2B This is a plan view when the infrared sensor according to Embodiment 1 is viewed from above.

[0016] Figure 2C It's perspective Figure 2B A top view of the light receiving portion and the hollow supporting portion of the infrared sensor shown in FIG.

[0017] Figure 3A This is a cross-sectional view for explaining the method of manufacturing the infrared sensor according to the first embodiment.

[0018] Figure 3B This is a cross-sectional view for explaining the method of manufacturing the infrared sensor according to the first embodiment.

[0019] Figure 3C This is a cross-sectional view for explaining the method of manufacturing the infrared sensor according to the first embodiment.

[0020] Figure 3D It is a cross-sectional view for explaining the manufacturing method of the infrared sensor of Embodiment 1.

[0021] Figure 3E It is a cross-sectional view for explaining the manufacturing method of the infrared sensor of Embodiment 1.

[0022] Figure 4A It is a top view of the infrared reflection structure of Embodiment 1 for the calculation of thermal behavior.

[0023] Figure 4B It is a cross-sectional view of the infrared reflection structure of Embodiment 1 for the calculation of thermal behavior.

[0024] Figure 5A It is a top view of the infrared reflection structure of the comparative example for the calculation of thermal behavior.

[0025] Figure 5B It is a cross-sectional view of the infrared reflection structure of the comparative example for the calculation of thermal behavior.

[0026] Figure 6 It is a graph showing the calculation results of the temperature change in the infrared reflection structures of Embodiment 1 and the comparative example.

[0027] Fig. 7A It is a cross-sectional view for explaining the process of mounting the infrared sensor of Embodiment 1 on a package.

[0028] Figure 7B It is a cross-sectional view for explaining the process of mounting the infrared sensor of Embodiment 1 on a package.

[0029] Figure 7C It is a cross-sectional view for explaining the process of mounting the infrared sensor of Embodiment 1 on a package.

[0030] Fig.7D It is a cross-sectional view for explaining the process of mounting the infrared sensor of Embodiment 1 on a package.

[0031] Figure 8 It is a cross-sectional view showing the setup for obtaining a correction coefficient for correcting an infrared detection signal.

[0032] Fig. 9 It is a graph showing an example of the relationship between the set temperature of a blackbody furnace and an infrared detection signal.

[0033] Fig.10 It is a top view when observing the infrared reflection structure of Modification 1 of Embodiment 1 from above.

[0034] Fig.11 This is a plan view of the infrared reflection structure according to the second modification of the first embodiment when viewed from above.

[0035] Fig.12 This is a cross-sectional view showing an infrared sensor according to Embodiment 2.

[0036] Fig.13A This is a cross-sectional view showing an infrared sensor according to Embodiment 3.

[0037] Fig. 13B This is a cross-sectional view showing a part of the infrared reflection structure included in the infrared sensor according to the third embodiment.

[0038] Fig. 13C This is a plan view when the infrared sensor according to Embodiment 3 is viewed from above.

[0039] Fig.14A This is a cross-sectional view showing an infrared sensor according to a fourth embodiment.

[0040] Fig. 14B This is a plan view when the infrared sensor according to Embodiment 4 is viewed from above. DETAILED DESCRIPTION

[0041] (Insights that form the basis of this disclosure)

[0042] Infrared sensors require an improvement in infrared detection accuracy. When a thin film light receiving unit is used as described above, the transmittance of the irradiated infrared light through the thin light receiving unit increases, and the S / N decreases. As a result, for example, if the light receiving unit is simply supported in a hollow manner for thermal insulation, it is difficult to obtain a stable electromotive force generated by the Seebeck effect.

[0043] In order to improve the reduction in S / N caused by the thin film of the light receiving part, the following method can be considered: a metal reflective film is set in the direction opposite to the light source direction when observed from the light receiving part, so that the infrared light after passing through the light receiving part is reflected again and reabsorbed by the light receiving part, thereby suppressing the reduction in the infrared absorption amount of the light receiving part. The metal reflective film in this case is formed, for example, directly below the light receiving part and on the substrate through an insulating film. In addition, for the material of the metal reflective film, high melting point metals such as tungsten (W) are suitable. The thermopile is composed of, for example, a P-type semiconductor and an N-type semiconductor, so the metal reflective film is exposed to high temperature during the process of doping impurities and annealing. Therefore, the metal reflective film composed of a high melting point metal can withstand this temperature.

[0044] The inventors of the present application have found that even if such a metal reflection film is used, there is a problem that the error of the infrared detection signal of the infrared sensor cannot be sufficiently reduced. Here, the problems in the infrared sensor using the metal reflection film are described with reference to the infrared sensor of the comparative example.

[0045] Figure 1 It is a cross-sectional view showing an infrared sensor 1X according to a comparative example.

[0046] like Figure 1 As shown in FIG. 1 , the infrared sensor 1X of the comparative example includes a semiconductor substrate 10, an insulating layer 20, a metal reflective film 30X, a light receiving portion 40, and a hollow support portion 50. In addition, the infrared sensor 1X includes a hot junction metal electrode 61 and a cold junction metal electrode 63p. In the infrared sensor 1X, an electromotive force corresponding to the temperature difference between the hot junction metal electrode 61 and the cold junction metal electrode 63p is generated.

[0047] The insulating layer 20 includes an insulating film 21 located on the semiconductor substrate 10 and an insulating film 22 located on the insulating film 21. The metal reflective film 30X is located on the insulating film 21. The metal reflective film 30X is made of a high melting point metal such as tungsten, for example. The light receiving unit 40 is supported by the hollow support unit 50 and is arranged above the metal reflective film 30X with a gap therebetween.

[0048] In forming the infrared sensor 1X, dry etching of tungsten and its adhesion layer constituting the metal reflection film 30X is two-stage etching requiring replacement of etching gas as described in Patent Document 2, which leads to a problem of poor productivity.

[0049] In addition, there is also a problem that the metal reflection film 30X becomes a factor causing a detection error in the infrared sensor 1X.

[0050] Specifically, the thermal conductivity of the electrical insulating film 21 used in a general electronic device is generally low. If heat is generated by the metal reflection film 30X formed on the insulating film 21 formed on the semiconductor substrate 10, it is difficult for the heat to escape to the semiconductor substrate 10 through the insulating film 21. The heat generated by the metal reflection film 30X is mainly generated by the absorption of a part of the infrared rays that the metal reflection film 30X fails to fully reflect by the metal reflection film 30X.

[0051] In addition, since the metal reflective film 30X is formed on the insulating film 21 with low thermal conductivity, it takes time for the temperature of the metal reflective film 30X to adapt to the temperature of the semiconductor substrate 10 that can be regarded as a heat bath. That is, although the ambient temperature around the infrared sensor 1X changes and the temperature of the semiconductor substrate 10 also changes, the temperature change of the metal reflective film 30X is slower than that of the semiconductor substrate 10. Moreover, the metal reflective film 30X absorbs a part of the infrared incident light whose incident amount changes all the time and its temperature changes, but it is difficult to grasp the temperature of the metal reflective film 30X itself. The metal reflective film 30X with unknown temperature is close to the light-receiving part 40, and the metal reflective film 30X and the light-receiving part 40 have a radiative relationship with each other. Therefore, the temperature of the hot-junction metal electrode 61 on the light-receiving part 40 is affected by the temperature of the metal reflective film 30X with unknown temperature. This influence also spreads to the temperature difference between the hot-junction metal electrode 61 and the cold-junction metal electrode 63p and the electromotive force generated by this temperature difference.

[0052] When the thermal time constant for the heat generated by the metal reflective film 30X to escape to the semiconductor substrate 10 and the air (when the gap 51 is air instead of vacuum) and the temperature to be moderated is set as τ, the temperature rise of the metal reflective film 30X will not be moderated unless it passes through several times, for example, 5 times the thermal time constant τ. Therefore, the temperatures of the light-receiving part 40 and the hot-junction metal electrode 61 include the influence of the temperature of the metal reflective film 30X within the past 5τ.

[0053] When the infrared sensor 1X detects infrared rays at a sampling rate less than 5τ, the (N - 1)th infrared detection information is mixed into the Nth infrared detection information as an error factor. That is, contrary to the purpose of setting the metal reflective film 30X to improve the S / N, this error factor is included in the S component. In order to eliminate this error factor, it is only necessary to make the sampling rate 5τ or more, but this 5τ becomes the speed limit for detection or shooting. Therefore, this error factor becomes a problem contrary to the aforementioned advantage of having good followability to changes in infrared power by using the light-receiving part 40 with a small heat capacity due to thinning.

[0054] The above is the description of the behavior of the heat generated in the metal reflective film 30X due to the infrared rays irradiated on the infrared sensor 1X, but the influencing factors of the temperature of the metal reflective film 30X that become error factors are not limited to this infrared ray. For example, when the ambient temperature around the infrared sensor 1 changes rapidly, the temperature of the semiconductor substrate 10 that is widely in contact with the environment also changes, but the temperature change of the metal reflective film 30X formed on the insulating film 21 is slower compared to that. The temperature of the semiconductor substrate 10 can be grasped by using a temperature sensor, for example, but the temperature of the metal reflective film 30X is unknown. Therefore, the influence of the metal reflective film 30X with unknown temperature on the temperature of the light-receiving part 40 via radiation becomes an error factor that is difficult to correct.

[0055] The inventors of the present application conducted intensive research and focused on metal vias connected to transistors formed on a substrate, and found that the above-mentioned problems can be solved by using the same metal vias in an infrared reflection structure, thereby obtaining a solution of the present disclosure. The details are described below.

[0056] (Overview of the present disclosure)

[0057] Examples of the infrared sensor of the present disclosure are shown below.

[0058] The infrared sensor of the first scheme of the present disclosure comprises: a substrate; an insulating layer located on the upper surface of the substrate; a first infrared reflection structure arranged in the insulating layer; a light receiving part located above the first infrared reflection structure; a hollow supporting part that hollow-supports the light receiving part so that a gap is formed between the first infrared reflection structure and the light receiving part; and a thermoelectric conversion part that generates an infrared detection signal based on heat generated by the light receiving part, and the first infrared reflection structure is composed of a plurality of first metal vias extending in the insulating layer along the thickness direction of the insulating layer.

[0059] Thus, the infrared light that has passed through the light receiving unit and through the gap is reflected by the first infrared reflecting structure and absorbed by the light receiving unit, thereby increasing the amount of infrared light absorbed by the light receiving unit. As a result, the infrared detection signal generated by the thermoelectric conversion unit based on the heat of the light receiving unit becomes larger, thereby improving the S / N.

[0060] In addition, the temperature of the first infrared reflective structure may rise due to the absorption of infrared rays. Therefore, when the temperature rises, the temperature of the light receiving part is affected by radiation or the like. Moreover, it is preferable that the temperature of the first infrared reflective structure is always known. One mode is that the temperature of the first infrared reflective structure is easy to quickly adapt to the state of the heat bath. In the infrared sensor of this scheme, the first infrared reflective structure is composed of a plurality of first metal vias extending in the thickness direction of the insulating layer in the insulating layer on the substrate. Therefore, the plurality of first metal vias can be in contact with the substrate or closer to the substrate than when a metal reflective film is formed on the insulating layer. As a result, the temperature of the plurality of first metal vias can quickly become equal to the temperature of the substrate which can be regarded as a heat bath and has a large heat capacity and is not easy to change in temperature. As a result, two advantages are brought about: (i) it is not easy to mix the N-1th infrared detection information into the Nth infrared detection information, and (ii) the temperature change of the first infrared reflective structure caused by the absorption of infrared rays at the Nth sampling time point is also small and the temperature of the first infrared reflective structure is regarded as equal to the substrate temperature. Therefore, the temperature of the first infrared reflection structure is not easy to change, and is not easy to affect the temperature of the light receiving part, so the error of the infrared detection signal generated by the thermoelectric conversion part can be reduced. In addition, by using a thermometer such as a thermistor to grasp the temperature of the substrate, the temperature of the plurality of first metal vias, that is, the temperature of the first infrared reflection structure, also becomes known. Therefore, by grasping the temperature of the substrate, the influence of the temperature of the first infrared reflection structure on the temperature of the light receiving part can be grasped in advance, so the infrared detection signal can be corrected. Therefore, the component of the infrared detection signal that depends on the temperature of the first infrared reflection structure can be eliminated by correction, thereby improving the detection accuracy.

[0061] Based on the above, the infrared sensor according to this solution can improve the detection accuracy of infrared rays.

[0062] In addition, the plurality of first metal vias can be formed by embedding metal into a via hole formed in the insulating layer and grinding it by CMP (Chemical Mechanical Polishing), which is a wiring process used in the conventional semiconductor device manufacturing. Therefore, the infrared sensor can be manufactured without using dry etching, which has poor productivity, which is used when forming a metal reflective film, thereby improving productivity.

[0063] In addition, for example, the infrared sensor of the second scheme of the present disclosure is further provided with a second infrared reflection structure configured in a manner to surround the light receiving portion and the gap when viewed from above, based on the infrared sensor of the first scheme, and the second infrared reflection structure is composed of a plurality of second metal vias extending in the insulating layer along the thickness direction of the insulating layer.

[0064] Thus, the reflected light that has not traveled toward the light receiving unit among the reflected light by the first infrared reflecting structure can be reflected by the second infrared reflecting structure and absorbed by the light receiving unit. Therefore, the infrared absorption amount of the light receiving unit can be further increased.

[0065] In addition, for example, the infrared sensor of the third scheme of the present disclosure is based on the infrared sensor of the second scheme, and the thermoelectric conversion part is a thermopile type thermoelectric conversion element having a hot junction metal electrode and a cold junction metal electrode, and one of the multiple second metal vias is connected to the cold junction metal electrode.

[0066] Thus, the heat of the cold junction metal electrode can be easily transferred to the substrate through the second metal via provided in the insulating layer on the substrate, so that the temperature of the cold junction metal electrode can be stabilized. As a result, the temperature difference between the hot junction metal electrode and the cold junction metal electrode is stabilized, and the accuracy of the infrared detection signal generated by the thermoelectric conversion unit can be improved.

[0067] In addition, for example, the infrared sensor of the fourth scheme of the present disclosure is further provided with a transistor for switching whether the infrared detection signal generated by the thermoelectric conversion unit is output from the cold junction metal electrode on the basis of the infrared sensor of the third scheme, wherein the transistor is formed on the substrate, and the input terminal of the transistor is electrically connected to the cold junction metal electrode via the second metal via.

[0068] This allows the transistor to be located below the cold junction metal electrode. As a result, the area of ​​the infrared sensor in a plan view can be reduced, and the infrared sensor can be miniaturized.

[0069] Furthermore, for example, an infrared sensor according to a fifth aspect of the present disclosure is the infrared sensor according to any one of the first to fourth aspects, wherein a portion of the outer peripheries of the plurality of first metal vias in a plan view are connected to one another.

[0070] This makes it easy to increase the density of the first metal vias in a plan view, thereby improving the infrared reflectivity of the first infrared reflective structure.

[0071] Furthermore, for example, an infrared sensor according to a sixth aspect of the present disclosure is the infrared sensor according to any one of the first to fifth aspects, wherein end surfaces of the plurality of first metal vias on the substrate side are in contact with the substrate.

[0072] Thus, the first metal via is directly bonded to the substrate which can be regarded as a heat bath. Therefore, even if a temperature disturbance is applied to the first metal via, the temperature of the first metal via can be made close to the temperature of the substrate more quickly.

[0073] In addition, for example, the infrared sensor of the 7th scheme of the present disclosure is based on the infrared sensor of any one of the 1st to 5th schemes, and further includes a gate electrode located on the upper surface of the substrate, and the end surface of the substrate side of the plurality of first metal vias is connected to the gate electrode.

[0074] Thus, the first metal via is connected to the substrate which can be regarded as a heat bath through a gate electrode including a nano-scale thin gate oxide film which does not easily hinder heat conduction. Therefore, even if a temperature disturbance is applied to the first metal via, the temperature of the first metal via can be made close to the temperature of the substrate more quickly.

[0075] In addition, for example, the infrared sensor of the 8th scheme of the present disclosure is based on the infrared sensor of any one of the 1st scheme to the 7th scheme, wherein the substrate has a high-concentration impurity region doped with impurities, the high-concentration impurity region is located at the upper end of the substrate and below the first infrared reflecting structure, and the impurity concentration of the high-concentration impurity region is higher than the impurity concentration of a portion of the substrate below the high-concentration impurity region.

[0076] The high-concentration impurity region of the substrate doped with impurities has a high reflectivity to infrared rays, so the reflectivity is increased by the synergistic effect of the reflection effect of the first metal via and the reflection effect of the high-concentration impurity region. Therefore, the infrared absorption amount of the light receiving part can be further increased.

[0077] Furthermore, for example, an infrared sensor according to a ninth aspect of the present disclosure is the infrared sensor according to any one of the first to eighth aspects, wherein the hollow support portion has a phononic crystal structure.

[0078] Due to the heat insulation of the phononic crystal structure of the hollow support portion, the heat of the light receiving portion whose temperature has changed due to infrared irradiation is less likely to be released, and thus the infrared detection sensitivity of the thermoelectric conversion portion is improved.

[0079] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0080] In addition, the embodiments to be described below are all embodiments showing general or specific examples. The numerical values, shapes, materials, constituent elements, configuration positions of constituent elements, connection methods, steps (processes), and the order of steps (processes) shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, the constituent elements that are not recorded in the independent claims among the constituent elements in the following embodiments are described as arbitrary constituent elements.

[0081] In addition, each figure is a schematic diagram and is not necessarily a strict illustration. Therefore, for example, the scales in each figure are not necessarily the same. In addition, in each figure, substantially the same structure is marked with the same reference numeral, and repeated descriptions are omitted or simplified.

[0082] In addition, in this specification, terms such as parallel that indicate the relationship between elements, terms such as rectangle that indicate the shape of an element, and numerical ranges are not expressions with strict meanings, but also mean that they include substantially the same range, for example, expressions that include a difference of several percent.

[0083] In addition, in this specification, the terms "above" and "below" do not refer to the upper direction (vertically above) and the lower direction (vertically below) in absolute spatial cognition, but are used as terms defined by relative positional relationships. Specifically, the light-receiving side of the infrared sensor is set to "above", and the side opposite to the light-receiving side is set to "below". In addition, the terms "above" and "below" are only used to specify the relative configuration between components, and are not intended to limit the posture of the infrared sensor when in use. In addition, the terms "above" and "below" are not only applicable to the case where two components are arranged at a distance from each other and there is another component between the two components, but also to the case where two components are arranged close to each other and the two components are connected.

[0084] In the present specification, unless otherwise specified, “viewed from above” means viewing from a direction perpendicular to the upper surface of the semiconductor substrate (that is, the thickness direction of the semiconductor substrate).

[0085] In the present specification, unless otherwise specified, ordinal numbers such as “first” and “second” do not mean the number or order of components but are used to distinguish components to avoid confusion between the same components.

[0086] (Implementation Method 1)

[0087] Hereinafter, the infrared sensor according to the first embodiment will be described.

[0088] [constitute]

[0089] First, the configuration of the infrared sensor according to Embodiment 1 will be described.

[0090] Figure 2A This is a cross-sectional view showing the infrared sensor 1 according to the first embodiment. Figure 2B This is a plan view when the infrared sensor 1 according to the first embodiment is viewed from above. Figure 2C is a perspective Figure 2BFIG. 1 is a top view of the light receiving portion 40 and the hollow supporting portion 50 of the infrared sensor 1 shown. Figure 2A Indicated in Figure 2B The infrared sensor 1 shown is a cross section of the metal wiring 84, the metal wiring 83, the metal wiring 71, the cold junction metal electrode 63p, the P-type semiconductor 65p, the hot junction metal electrode 61, the hot junction metal electrode 62, the P-type semiconductor 66p, and the cold junction metal electrode 64p cut along a line passing through them in this order. Figure 2B In FIG. 4 , the positions of the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p which are actually covered by the insulating film 41 are indicated by thick dotted lines. Figure 2B In FIG. 4 , the outline of the semiconductor 42 in the light receiving portion 40 which is actually covered by the insulating film 41 is shown by a dotted line. Figure 2C In FIG. 1 , outlines of the light receiving portion 40 and the hollow supporting portion 50 that are viewed through are shown by dotted lines.

[0091] like Figure 2A to Figure 2C As shown, the infrared sensor 1 includes a semiconductor substrate 10, an insulating layer 20, an infrared reflection structure 30, a light receiving portion 40, a hollow support portion 50, a thermoelectric conversion portion 60, and a transistor 80. The semiconductor substrate 10 is an example of a substrate. In addition, the infrared reflection structure 30 is an example of a first infrared reflection structure. The infrared sensor 1 is, for example, an infrared sensor chip formed using the semiconductor substrate 10.

[0092] The semiconductor substrate 10 is a substrate for forming the light receiving portion 40, the hollow support portion 50, the thermoelectric conversion portion 60, and the peripheral circuits. The semiconductor substrate 10 is, for example, a silicon substrate, but may also be a semiconductor substrate other than a silicon substrate. The thickness of the semiconductor substrate 10 is, for example, greater than the thickness of the insulating layer 20. A transistor 80 is formed on the upper surface 11 of the semiconductor substrate 10.

[0093] The transistor 80 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The transistor 80 includes a source 80s, a drain 80d, a gate 80g, and a well 80w. In addition, a gate oxide film is arranged between the gate 80g as a conductive layer and the channel region of the transistor 80. In this embodiment, the source 80s is the input terminal of the transistor 80, and the drain 80d is the output terminal of the transistor 80. In addition, depending on the type and concentration of impurities in the semiconductor substrate 10, the transistor 80 may not include the well 80w.

[0094] In this embodiment, whether to output the infrared detection signal generated by the thermoelectric conversion unit 60 is switched by turning on (ON) or off (OFF) the transistor 80. When the infrared sensor 1 is used as a pixel of an infrared imaging element, the transistor 80 assumes the function of a pixel selection switch. In addition, the infrared sensor 1 may also include a MOSFET formed on the semiconductor substrate 10 other than the transistor 80. The MOSFET other than the transistor 80 assumes, for example, a logic function of pixel selection or a detection signal amplification function.

[0095] The insulating layer 20 is located on the upper surface 11 of the semiconductor substrate 10. The insulating layer 20 includes an insulating film 21 located on the semiconductor substrate 10 and an insulating film 22 located on the insulating film 21 on the side opposite to the semiconductor substrate 10. The insulating film 21 and the insulating film 22 are sequentially stacked on the upper surface 11 of the semiconductor substrate 10 from the semiconductor substrate 10 side in this order along the thickness direction of the semiconductor substrate 10. The insulating film 21 and the insulating film 22 are made of, for example, silicon oxide (SiO 2 ) and other oxides, but can also be composed of insulating materials other than silicon oxide.

[0096] The infrared reflection structure 30 reflects the infrared incident light Lin that has passed through the light receiving unit 40 toward the light receiving unit 40. The infrared reflection structure 30 is provided in the insulating layer 20. The infrared reflection structure 30 is composed of a plurality of metal vias 31 extending in the thickness direction of the insulating layer 20 in the insulating layer 20. Specifically, the plurality of metal vias 31 are formed in a columnar shape in the insulating film 21, and stand in a row from the semiconductor substrate 10 in a manner extending in the thickness direction of the insulating film 21 in the insulating film 21. Each of the plurality of metal vias 31 is composed of a high melting point metal such as tungsten, for example.

[0097] In this embodiment, the plurality of metal vias 31 are separated from each other via the insulating film 21. In addition, the plurality of metal vias 31 are arranged in an array in multiple columns in the vertical and horizontal directions in a plan view. The plan view shape of the metal via 31 is, for example, a rectangle, but is not particularly limited.

[0098] In a plan view, the area where the plurality of metal vias 31 constituting the infrared reflective structure 30 are formed is larger than the light receiving portion 40 .

[0099] The thickness of the metal via 31 (the length in the vertical direction and the horizontal direction when viewed from above) is, for example, not less than 0.5 μm and not more than 1 μm. In addition, the distance between two metal vias 31 adjacent in the vertical direction or the horizontal direction when viewed from above (the length of the gap when viewed from above) is not less than 0.5 μm and not more than 1 μm. Thus, the pitch of the arrangement of the plurality of metal vias 31 is not less than 0.5 μm and not more than 1 μm, and is thin to a degree not less than 1 / 10 and not more than 1 / 5 of the wavelength of the infrared light received near 10 μm. Therefore, the infrared reflection structure 30 composed of the plurality of metal vias 31 can display the same as the above-mentioned Figure 1 The uniformly formed metal reflection film 30X has similar reflection characteristics as shown in FIG.

[0100] The end surfaces 32 of the plurality of metal vias 31 on the semiconductor substrate 10 side (lower side) are in contact with the upper surface 11 of the semiconductor substrate 10. The upper end surfaces of the plurality of metal vias 31 are covered with a thin insulating film, but may be exposed in the gap 51.

[0101] The light receiving portion 40 generates heat due to absorption of infrared rays, and the temperature of the light receiving portion 40 rises due to the heat. The amount of heat generated by the light receiving portion 40 depends on the amount of infrared rays absorbed in the light receiving portion 40. The light receiving portion 40 is located above the infrared reflecting structure 30. The light receiving portion 40 has a two-dimensional extension. The top view shape of the light receiving portion 40 is, for example, a square, but may also be other shapes such as a rectangle. The light receiving portion 40 overlaps with the infrared reflecting structure 30 when viewed from above. For example, the light receiving portion 40 is located as a whole on the inner side of a range in which a plurality of metal vias 31 are formed when viewed from above. The light receiving portion 40 is separated from the infrared reflecting structure 30, and a gap 51 is formed between the light receiving portion 40 and the infrared reflecting structure 30.

[0102] In this embodiment, the light receiving unit 40 includes a part of the insulating film 41 and a part of the thin film semiconductor 42. The light receiving unit 40 has a sandwich structure of the insulating film 41 and the semiconductor 42.

[0103] The insulating film 41 and the semiconductor 42 are arranged above the insulating layer 20. The insulating film 41 is formed on the gap 51 and the insulating layer 20. The semiconductor 42 is sandwiched by the insulating film 41 from above and below. N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p described later are formed on a portion of the semiconductor 42. The insulating film 41 is composed of, for example, silicon nitride (SiN), but may also be composed of an insulating material other than silicon nitride (for example, silicon oxide). The semiconductor 42 is, for example, polycrystalline silicon, but may also be a semiconductor other than polycrystalline silicon.

[0104] The hollow support portion 50 supports the light receiving portion 40 in a hollow manner so that a gap 51 is formed between the infrared reflective structure 30 and the light receiving portion 40. In addition, the gap 51 is located between the light receiving portion 40 and the hollow support portion 50 and the semiconductor substrate 10. In the present embodiment, the hollow support portion 50 is two arms that connect the light receiving portion 40 and the insulating layer 20. The hollow support portion 50 includes a part of the insulating film 41, and N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p that are parts of the semiconductor 42. The sidewalls of the gap 51 are formed by the insulating film 22 of the insulating layer 20. The gap 51 is, for example, a recessed portion formed in the insulating layer 20 by removing a part of the insulating film 22 of the insulating layer 20. Even if the insulating film 22 below the light receiving portion 40 is removed in this way to form the gap 51, the light receiving portion 40 is supported in a hollow manner by the hollow support portion 50. In addition, the gap 51 suppresses the transfer of heat from the light receiving unit 40 to the insulating layer 20 and the semiconductor substrate 10 , thereby suppressing a decrease in the temperature of the light receiving unit 40 that has risen due to receiving infrared rays.

[0105] In the infrared sensor 1, the infrared incident light Lin is incident from above, and a part of the infrared incident light Lin is absorbed by the light receiving unit 40. In addition, the infrared incident light Lin that has passed through the light receiving unit 40 is reflected on the upper surface of the plurality of metal vias 31 via the gap 51, and the reflected light Lre is also absorbed by the light receiving unit 40. As a result, the infrared absorption amount of the light receiving unit 40 is increased, and the temperature of the light receiving unit 40 is easily increased.

[0106] The thermoelectric conversion unit 60 generates an infrared detection signal based on the heat generated by the light receiving unit 40. The infrared detection signal is, for example, a voltage signal or a current signal. At least a portion of the thermoelectric conversion unit 60 is disposed in the hollow support portion 50. In the present embodiment, the thermoelectric conversion unit 60 is a thermopile type thermoelectric conversion element utilizing the Seebeck effect. The thermoelectric conversion unit 60 includes hot junction metal electrodes 61, 62, cold junction metal electrodes 63p, 63n, 64p, 64n, N-type semiconductors 65n, 66n, P-type semiconductors 65p, 66p, and metal wiring 67.

[0107] The hot contact metal electrodes 61 and 62 are located on the light receiving part 40. In addition, the hot contact metal electrodes 61 and 62 are located near the connection part between the light receiving part 40 and the hollow support part 50. In addition, the hot contact metal electrodes 61 and 62 are not particularly limited as long as they are located at a position where the temperature changes synchronously with the temperature of the light receiving part 40. For example, they can be located at a position adjacent to the light receiving part 40.

[0108] The cold contact metal electrodes 63p, 63n, 64p, 64n are located outside the light receiving portion 40 in a plan view. In addition, the cold contact metal electrodes 63p, 63n, 64p, 64n are located outside the gap 51 in a plan view. In addition, the cold contact metal electrodes 63p, 63n, 64p, 64n are located near the connection portion between the insulating layer 20 and the hollow support portion 50. The hot contact metal electrode 61 and the cold contact metal electrodes 63p, 64n are arranged so as to sandwich one arm of the hollow support portion 50. The hot contact metal electrode 62 and the cold contact metal electrodes 63n, 64p are arranged so as to sandwich the other arm of the hollow support portion 50.

[0109] N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p are respectively provided in the insulating film 41. N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p are respectively linearly extended along the hollow support portion 50. N-type semiconductor 66n and P-type semiconductor 65p pass through one arm of the hollow support portion 50. In addition, N-type semiconductor 65n and P-type semiconductor 66p pass through the other arm of the hollow support portion 50. N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p are respectively formed by doping semiconductor 42 with impurities (for example, boron (B) or phosphorus (P)).

[0110] One end of the N-type semiconductor 66n and one end of the P-type semiconductor 65p are in contact with the hot contact metal electrode 61 and are connected to the hot contact metal electrode 61. The N-type semiconductor 66n and the P-type semiconductor 65p form a hot contact by being electrically connected via the hot contact metal electrode 61. In addition, one end of the N-type semiconductor 65n and one end of the P-type semiconductor 66p are in contact with the hot contact metal electrode 62 and are connected to the hot contact metal electrode 62. The N-type semiconductor 65n and the P-type semiconductor 66p form a hot contact by being electrically connected via the hot contact metal electrode 62.

[0111] The other end of the P-type semiconductor 65p is connected to the cold contact metal electrode 63p, and is connected to the cold contact metal electrode 63p, thereby forming a cold contact. The other end of the N-type semiconductor 66n is connected to the cold contact metal electrode 64n, and is connected to the cold contact metal electrode 64n, thereby forming a cold contact. The other end of the P-type semiconductor 66p is connected to the cold contact metal electrode 64p, and is connected to the cold contact metal electrode 64p, thereby forming a cold contact. The other end of the N-type semiconductor 65n is connected to the cold contact metal electrode 63n, and is connected to the cold contact metal electrode 63n, thereby forming a cold contact.

[0112] The connection between the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p and the hot contact metal electrodes 61, 62 and the cold contact metal electrodes 63p, 63n, 64p, 64n is an ohmic connection. The N-type semiconductor 66n and the P-type semiconductor 65p that are ohmically connected to the same hot contact metal electrode 61 constitute a thermocouple. In addition, the N-type semiconductor 65n and the P-type semiconductor 66p that are ohmically connected to the same hot contact metal electrode 62 constitute a thermocouple.

[0113] When the light receiving unit 40 absorbs infrared rays and as a result the temperature of the hot junction is higher than the temperature of the cold junction, a large number of carriers gather on the cold junction side. As a result, the cold junctions of the N-type semiconductors 65n and 66n have a negative electromotive force relative to the cold junctions of the P-type semiconductors 65p and 66p. In the example shown in the figure, there are two pairs of cold junctions and hot junctions, and the metal wiring 67 electrically connects the cold junction metal electrode 64n and the cold junction metal electrode 64p. Therefore, the two thermocouples with electromotive force are connected in series, and the cold junction metal electrode 63n has a negative electromotive force relative to the cold junction metal electrode 63p. That is, a potential difference corresponding to the heat generated by the light receiving unit 40 is generated between the cold junction metal electrode 63p and the cold junction metal electrode 63n. At this time, the cold junction metal electrode 63n is maintained at a certain predetermined potential that serves as a reference, and when the transistor 80 is turned on, an infrared detection signal corresponding to the electromotive force is output from the cold junction metal electrode 63p via the transistor 80. The infrared detection signal is amplified by an amplifier, for example, and taken out to the outside. In addition, the temperature relationship between the "hot junction" and the "cold junction" of the thermoelectric conversion unit 60 is not necessarily that the temperature of the hot junction is higher than the temperature of the cold junction. For example, in the case where the infrared sensor 1 is used to detect the temperature of an object lower than the temperature of the infrared sensor 1 itself, the temperature of the hot junction is sometimes lower than the temperature of the cold junction. At this time, the polarity of the electromotive force of the thermoelectric conversion unit 60 is reversed.

[0114] The source 80s of the transistor 80 is electrically connected to the metal wiring 83 located above the insulating layer 20 via a metal via 81 extending in the thickness direction of the insulating layer 20 in the insulating layer 20. The metal wiring 83 is electrically connected to the cold junction metal electrode 63p via the metal wiring 71. The drain 80d of the transistor 80 is electrically connected to the metal wiring 84 located above the insulating layer 20 via a metal via 82 extending in the thickness direction of the insulating layer 20 in the insulating layer 20. The metal wiring 84 is, for example, electrically connected to a terminal for connecting to the outside. In addition, the metal wiring 84 can be a terminal. Thus, when the transistor 80 is in the on state, the infrared detection signal generated by the thermoelectric conversion unit 60 is output to the outside from the cold junction metal electrode 63p via the transistor 80.

[0115] Hot contact metal electrodes 61, 62, cold contact metal electrodes 63p, 63n, 64p, 64n, metal wiring 67, metal wiring 71, metal wiring 83 and metal wiring 84 are each made of metal such as aluminum. Metal vias 81, 82 are made of high melting point metal such as tungsten.

[0116] In addition, the hollow support portion 50 may have a phononic crystal structure. For example, a phononic crystal structure is formed in the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p passing through the hollow support portion 50. The artificial phononic crystal structure processed by semiconductor technology is a structure in which fine holes with a diameter of the order of tens of nanometers are dug out and arranged periodically. The period of the pores is, for example, greater than 1 nm and less than 300 nm. The pore diameter is, for example, greater than 10 nm and less than 50 nm.

[0117] Since the wavelength of the phonons that transport heat mainly involves the range of 1nm to 300nm, if the period is in such a range, the phononic crystal structure is likely to have high thermal insulation. Electron beam lithography is suitable for forming a phononic crystal structure with a period of more than 100nm and less than 300nm. In addition, block copolymer (BCP) lithography is suitable for forming a phononic crystal structure with a period of more than 1nm and less than 100nm. The semiconductor 42 (including the doped area) composed of polycrystalline silicon and the like contained in the hollow support portion 50 can be used to dig out fine through holes using the above-mentioned lithography and dry etching. At this time, if the aspect ratio of the hole (hole depth / hole diameter) is less than 5, the etching gas can easily enter the hole and easily process the hole. For example, the etching gas can etch a hole with a diameter of 20nm and penetrate a polycrystalline silicon film with a thickness of 100nm to form a phononic crystal structure with a hole diameter of 20nm.

[0118] The processing of holes with an aspect ratio greater than 5 will make it difficult to balance the processing shape and productivity. Therefore, the maximum film thickness of the light receiving part 40 suitable for making a phononic crystal structure is about 100nm. In order to match the impedance of the vacuum in the wavelength region of the infrared light to be detected and improve the light receiving efficiency, a metal film with a thickness of several nm can be formed on the surface of the light receiving part 40, but in this case, the thickness of the light receiving part 40 will not change significantly from about 100nm. In addition, when the thin film of the semiconductor 42 is used for the hollow support part 50 and the light receiving part 40, it is easy for infrared light to pass through because of its thinness. Therefore, a method of returning the reflected light Lre to the light receiving part 40 through the infrared reflection structure 30 to compensate for the infrared light received in the light receiving part 40 is effective. In addition, since the hollow support part 50 has a phononic crystal structure, the thermal insulation of the hollow support part 50 becomes higher and it is easy to maintain the temperature difference between the hot junction and the cold junction, so the sensitivity of the infrared sensor 1 can be improved. Furthermore, since the infrared sensor 1 uses the light receiving unit 40 which is thin and has a small heat capacity, the temperature difference between the hot junction and the cold junction can be sensitively changed according to the change of the irradiated infrared power, thereby realizing the infrared sensor 1 with high response speed.

[0119] [Manufacturing method of infrared sensor]

[0120] Next, a method for manufacturing the infrared sensor 1 of the present embodiment will be described. The manufacturing method described below is an example, and the method for manufacturing the infrared sensor 1 is not limited to the following example.

[0121] Figure 3A to Figure 3E This is a cross-sectional view for explaining the method of manufacturing the infrared sensor 1 according to the first embodiment.

[0122] First, if Figure 3A As shown, a semiconductor substrate 10 having a transistor 80 formed thereon is prepared, and an insulating film 21 is formed on the semiconductor substrate 10 by CVD (Chemical Vapor Deposition). The insulating film 21 is, for example, a silicon oxide film. Next, the insulating film 21 is engraved by dry etching at the portion where the metal vias 31, 81, and 82 are to be formed, thereby forming a through hole 25.

[0123] Then, if Figure 3BAs shown, tungsten is deposited in the through hole 25 by a vapor deposition process or the like, forming a plurality of metal vias 31 on the semiconductor substrate 10, a metal via 81b on the source 80s, and a metal via 82b on the drain 80d. After the deposition of tungsten, the upper surfaces of the insulating film 21, the plurality of metal vias 31, and the metal vias 81b and 82b are exposed by CMP. In addition, in the formation of the plurality of metal vias 31 and the metal vias 81b and 82b, titanium nitride or the like may be formed as a base adhesion layer before tungsten is deposited in the through hole 25.

[0124] Then, if Figure 3C As shown, an insulating film 22 is formed on the insulating film 21 by CVD. The insulating film 22 is, for example, a silicon oxide film. The insulating film 22 located below the light receiving portion 40 and above the infrared reflection structure 30 composed of a plurality of metal vias 31 (a portion where the gap 51 is formed later) is engraved by dry etching to form a concave space 53. Furthermore, a thin protective film 23 is deposited by CVD on the insulating film 22 in which the concave space 53 is formed. The protective film 23 is, for example, a silicon oxide film.

[0125] Then, if Figure 3D As shown, the material of the sacrifice layer 55 is deposited to fill the recessed space 53, and the insulating film 22 and the upper surface of the sacrifice layer 55 are exposed by CMP. The material of the sacrifice layer 55 is, for example, polysilicon.

[0126] Then, if Figure 3E As shown, the insulating film 22 above the metal vias 81b and 82b is dry-etched to embed tungsten in the same manner as the metal vias 81b and 82b, and CMP is performed again to fill the metal vias 81b and 82b with tungsten, thereby forming the metal vias 81 and 82.

[0127] After that, after forming the light receiving portion 40, the hollow support portion 50, the thermoelectric conversion portion 60, and various metal wirings, the sacrificial layer 55 is formed by using xenon fluoride (XeF 2 ) is etched and removed to form a gap 51, thereby obtaining Figure 2A to Figure 2C The infrared sensor 1 shown in the figure is formed by using, for example, a processing technique used in manufacturing semiconductor devices, in forming the light receiving portion 40, the hollow supporting portion 50, the thermoelectric conversion portion 60, and various metal wirings.

[0128] Thus, in the manufacturing method of the infrared sensor 1 of the present embodiment, the infrared reflection structure 30 using a high melting point metal such as tungsten can be formed by embedding tungsten in the through hole 25 and grinding it by CMP, which is a wiring process used in the conventional semiconductor device manufacturing. Therefore, the infrared sensor 1 can be manufactured without using dry etching which is criticized for having poor productivity when forming a metal reflection film, and avoiding two-stage etching which requires replacement of etching gas, thereby improving productivity.

[0129] [Thermal behavior of infrared reflective structure]

[0130] In the infrared reflection structure 30 composed of a plurality of metal vias 31 of this embodiment, heat generated by the infrared reflection structure 30 can be rapidly dissipated to the semiconductor substrate 10 compared to the infrared reflection structure composed of a metal thin film. The results of calculation using the finite element method on this thermal behavior are described below.

[0131] Figure 4A This is a top view of the infrared reflection structure 30 according to the first embodiment used for calculation of thermal behavior. Figure 4B This is a cross-sectional view of the infrared reflective structure 30 according to the first embodiment used for calculation of thermal behavior. Figure 5A This is a top view of an infrared reflection structure of a comparative example used for calculation of thermal behavior. Figure 5B This is a cross-sectional view of an infrared reflection structure of a comparative example used for calculation of thermal behavior.

[0132] First, the configuration of each component used for calculation of thermal behavior will be described.

[0133] like Figure 4A as well as Figure 4B As shown, the infrared reflection structure 30 is composed of a plurality of metal vias 31, the size of the metal vias 31 when viewed from the top is 1 μm square, and the length of the metal vias 31 in the thickness direction of the insulating film 21 is 4 μm. In addition, the plurality of metal vias 31 are arranged at intervals of 1 μm on the semiconductor substrate 10 with a thickness of 725 μm, and the gaps between the metal vias 31 are filled with the insulating film 21 composed of a silicon oxide film. When viewed from the top, the ratio of the total area of ​​the plurality of metal vias 31 to the area of ​​the surrounding insulating film 21 is 1 / 3. In addition, the thickness of the insulating film 21 is 4 μm.

[0134] In addition, if Figure 5A as well as Figure 5B As shown, the metal reflection film 30X of the infrared reflection structure as a comparative example is formed to cover the entire upper surface of the insulating film 21 and has a thickness of 0.5 μm. In addition, the thickness of the insulating film 21 is 3.5 μm. The insulating film 21 is formed on the semiconductor substrate 10 with a thickness of 725 μm.

[0135] Next, conditions for calculating thermal behavior will be described.

[0136] like Figure 4B as well as Figure 5B As shown, the bottom surface of the semiconductor substrate 10 is at room temperature (300K). The infrared rays that are not completely absorbed by the light receiving unit 40 (not shown) are irradiated from above to the infrared reflective structure 30 and the metal reflective film 30X. Most of them are reflected by the infrared reflective structure 30 and the metal reflective film 30X, but a part of them is absorbed by the infrared reflective structure 30 and the metal reflective film 30X and becomes heat. Therefore, 10nJ / μm is absorbed in the 0.5μm thickness of the surface layer. 3 The heat generation lasts for 10μs. Figure 4B In the structure shown in the figure, the 0.5 μm thick portion of the surface layer of the metal via 31 and the 0.5 μm thick portion of the surface layer of the insulating film 21 become heat generation sources. Figure 5B In the structure shown, the entire metal reflection film 30X having a thickness of 0.5 μm serves as a heat generation source.

[0137] In addition, the thermal conductivity and specific heat capacity of the metal via 31 and the metal reflective film 30X are set to 178 W / (m·K) and 0.13 J / (g·K), respectively. The thermal conductivity and specific heat capacity of the insulating film 21 are set to 1.4 W / (m·K) and 1.0 J / (g·K), respectively. The thermal conductivity and specific heat capacity of the semiconductor substrate 10 are set to 157 W / (m·K) and 0.70 J / (g·K), respectively.

[0138] Next, calculation results of thermal behavior will be described.

[0139] Figure 6 Graphs showing calculation results of temperature changes in the infrared reflection structures of Embodiment 1 and Comparative Example. Figure 6 In the figure, the 10 μs when the infrared light is irradiated and heat is generated and the 10 μs when the infrared light is not irradiated are shown. Figure 4A as well as Figure 5A The calculation results of the temperature change of points A to C are shown. Point A is the center point of the upper surface of the metal via 31. Point B is the point on the upper surface of the insulating film 21 that is farthest from the four metal vias 31 arranged two by two vertically and horizontally. Point C is the center point of the upper surface of the metal reflective film 30X. Figure 6 The vertical axis represents the difference between the temperature of each point A, point B, and point C and the average temperature of the surface of the semiconductor substrate 10 . Figure 6 The horizontal axis represents the time when the infrared irradiation start is set to 0 μs.

[0140] like Figure 6As shown, the temperature of point C of the metal reflective film 30X rises by about +0.008°C during the first 10μs of heat generation. On the other hand, for the infrared reflection structure 30 using the metal via 31, the metal via 31 has a good effect of allowing heat to flow to the semiconductor substrate 10. Specifically, the temperature rise of point A of the metal via 31 is suppressed to less than +0.0005°C during the first 10μs of heat generation. In addition, the temperature rise of point B of the insulating film 21 is also suppressed to about +0.0015°C. This result can be said to be a manifestation of the effect that the heat of the insulating film 21 also flows from the metal via 31 to the semiconductor substrate 10.

[0141] According to the above, based on Figure 6 From the results shown, it can be said that the infrared reflective structure 30 using the metal via 31 has the following two advantages.

[0142] The first feature is that the infrared reflective structure 30 maintains a temperature substantially equal to that of the semiconductor substrate 10 due to a small temperature rise caused by absorbing infrared rays. Specifically, although the temperature of points A and B rises due to the generation of heat, the amplitude is small and the degree of rise is significantly smaller than that of point C. This shows that if the temperature of the semiconductor substrate 10 is grasped using a temperature sensor such as a thermistor, the temperature of the infrared reflective structure 30 can also be grasped. For example, if the influence of the temperature of the infrared reflective structure 30 on the temperature of the light receiving portion 40 due to radiation is grasped in advance, the influence can be corrected during the actual operation of the infrared sensor 1.

[0143] The second feature is that the infrared reflective structure 30 is sensitive to temperature changes. Specifically, in the temperature change at point C, it is not saturated during the first 10μs when heat is generated, and it is not completely relaxed during the second half of the 10μs when no heat is generated. In contrast, the temperature changes at points A and B change to a stable state in about 2μs. For example, the N-1th sampling is performed at time 0μs, and the Nth sampling is performed at time 20μs. In this case, for point C of the metal reflective film 30X, in the Nth sampling, the past temperature rise does not fully disappear and remains. Therefore, the infrared detection information obtained by the Nth sampling is affected by the temperature rise of the metal reflective film 30X that remains through radiation. The rising temperature of the metal reflective film 30X is different from the temperature of the semiconductor substrate 10, and cannot be grasped by a temperature sensor such as a thermistor, so the influence cannot be eliminated by correction. On the other hand, in the infrared reflection structure 30 using the metal via 31, the temperature rise of the infrared reflection structure 30 generated in the first 10 μs is sufficiently alleviated and disappears in the Nth sampling, so this influence does not appear as an error in the infrared detection information obtained by sampling.

[0144] Furthermore, the greater the ratio of the total area of ​​the plurality of metal vias 31 to the area of ​​the surrounding insulating film 21 is than 1 / 3, the greater the above-mentioned effect will be.

[0145] Due to the above two features, the temperature of the infrared reflective structure 30 using the metal via 31 can be regarded as the same temperature as the semiconductor substrate 10 , and the temperature of the infrared reflective structure 30 can be understood by understanding the temperature of the semiconductor substrate 10 .

[0146] [Correction of infrared sensor detection results]

[0147] Next, a description will be given of correction of the detection result of the infrared sensor 1. As described above, in the infrared sensor 1, the influence of the temperature of the infrared reflection structure 30 can be corrected.

[0148] First, the infrared sensor package on which the infrared sensor 1 is mounted is described. For example, the infrared sensor 1 is mounted on the package together with a thermistor chip for use. Thus, the temperature of the semiconductor substrate 10 can be grasped from the temperature indication value of the thermistor chip. Figure 7A to Figure 7D 2 is a cross-sectional view for explaining the process of mounting the infrared sensor 1 of the first embodiment on the package 2. Figure 7A to Figure 7D In the figure, details such as wiring from the inside to the outside of the package 2 and the structure of the infrared sensor 1 are not shown.

[0149] like Fig. 7A As shown, the thermistor chip 3 and the infrared sensor 1 are brought close to each other, and the two are die-attached to the bottom surface of the cavity provided in the package 2. At this time, the bottom surface of the cavity of the package 2 is metallized, and the back surface of the thermistor chip 3 and the back surface of the infrared sensor 1 are also metallized, and the die is attached using a paste with good thermal conductivity. In this way, the temperatures of the semiconductor substrate 10 of the infrared sensor 1, the thermistor chip 3, and the bottom surface of the cavity of the package 2 can be made substantially the same. The package 2 is, for example, a ceramic package.

[0150] Then, if Figure 7B As shown in FIG. 1 , bonding wires 4 are used to connect the thermistor chip 3 and the infrared sensor 1. Then, as shown in FIG. Figure 7C as well as Fig.7D As shown, a cover 5 is provided to seal the cavity of the package 2. The cover 5 can be made of glass, germanium, or AR (AntiReflection) coated silicon with good transmittance near the wavelength of 10 nm infrared light. The cover 5 and the package 2 are bonded by AuSn bonding or the like.

[0151] Through the above steps, an infrared sensor package 6 is obtained. The infrared sensor package 6 includes, for example, an infrared sensor 1, a thermistor chip 3 for measuring the temperature of a semiconductor substrate 10 of the infrared sensor 1, a package 2 having a cavity for accommodating the infrared sensor 1 and the thermistor chip 3, and a cover 5 for sealing the cavity of the package 2. The infrared sensor package 6 may include an infrared imaging element instead of the infrared sensor 1, and the infrared imaging element includes an infrared sensor array in which a plurality of infrared sensors 1 are arranged in an array on a common semiconductor substrate 10.

[0152] The infrared sensor package 6 equipped with the infrared sensor 1 also has the thermistor chip 3 mounted therein. The temperature indication value of the thermistor chip 3 is considered to be the same as the temperature of the semiconductor substrate 10 of the infrared sensor 1 arranged close to the package 2. As a result, the temperature indication value of the thermistor chip 3 is also considered to be the same as the temperature of the infrared reflection structure 30, which is composed of a plurality of metal vias 31 arranged in contact with the semiconductor substrate 10 serving as a heat bath.

[0153] Next, the correction of the infrared detection signal of the infrared sensor 1 is described. By grasping the temperature of the semiconductor substrate 10 using a thermometer such as a thermistor, the temperature of the infrared reflection structure 30 is also known, and the influence of the temperature of the infrared reflection structure 30 on the temperature of the light receiving part 40 through radiation can be grasped in advance. As a result, it is possible to realize a correction for eliminating the component that depends on the temperature of the infrared reflection structure 30 contained in the infrared detection signal of the infrared sensor 1. Specifically, in a state where a certain power of infrared rays is irradiated to the light receiving part 40, the temperature of the semiconductor substrate 10 regarded as a heat bath is controlled, and the infrared detection signal based on the electromotive force generated in the thermoelectric conversion part 60 is measured, thereby implementing a temperature correction process. The temperature of the semiconductor substrate 10 is grasped by a temperature sensor such as a thermistor and controlled to an arbitrary temperature. Even if the power of the irradiated infrared rays is the same, if the temperature of the semiconductor substrate 10 and the temperature of the infrared reflection structure 30 is isothermal therewith change, the electromotive force of the thermoelectric conversion part 60 also changes. By understanding the amount of this change, it is possible to obtain a correction factor required for estimating infrared power from the electromotive force of the thermoelectric conversion unit 60. Figure 8 as well as Fig. 9 Explain in detail.

[0154] Figure 8 2 is a cross-sectional view showing an arrangement for obtaining a correction coefficient for correcting an infrared detection signal. Figure 8 As shown, Fig.7DThe infrared sensor package 6 shown is mounted on a substrate 91 and is set in a constant temperature chamber 92. In addition, a black body furnace 93 is set in the constant temperature chamber 92. The irradiation surface of the black body furnace 93 is configured to face the infrared sensor 1. The black body furnace 93 irradiates the infrared sensor 1 with infrared incident light Lin. A lens 94 for transmitting infrared rays is provided between the black body furnace 93 and the infrared sensor package 6. The lens 94 is fixed to the substrate 91 via a housing 95 on which the lens 94 is mounted. Through the lens 94, the infrared sensor 1 is imaged on the irradiation surface of the black body furnace 93 of uniform temperature at a predetermined field angle and distance. An amplifier IC (Integrated Circuit) 96 for amplifying the infrared detection signal of the infrared sensor 1 is installed on the substrate 91.

[0155] If the ambient temperature T in the thermostatic chamber 92 is changed 0 , then the temperature indication value T of thermistor chip 3 th Change. Temperature indication value T th The temperature of the semiconductor substrate 10 of the infrared sensor 1, that is, the temperature of the heat bath is shown. Fig. 9 2 is a diagram showing an example of the relationship between the set temperature of the black body furnace 93 and the infrared detection signal. Fig. 9 In FIG. 1 , the temperature indication value T of the thermistor chip 3 is shown. th The relationship between the set temperature of the black body furnace 93 and the infrared detection signal at 0°C, 40°C, and 80°C. Fig. 9 The vertical axis is the output voltage V of the amplifier IC96 which amplifies the infrared detection signal. 0 . Fig. 9 The horizontal axis is the set temperature T of the black body furnace 93 B .

[0156] like Fig. 9 As shown, even if the same set temperature T B The infrared radiation of the black body furnace 93, if the ambient temperature T 0 The influence of temperature indication value T th If the value of the infrared detection signal is different, the value of the infrared detection signal will also be different. Fig. 9 The infrared detection signal and the set temperature T B The relationship is based on each temperature indication value T th By mathematically formulating or tabulating, the temperature indication value T obtained from the thermistor chip 3 can be referred to. th In addition, the temperature indicator value T thThe temperature of the semiconductor substrate 10 shown indicates the temperature of the infrared reflection structure 30 formed by a plurality of metal vias 31. Therefore, the estimated temperature of the photographed object corrected using the mathematical formula or table will be corrected for the effect of the temperature of the infrared reflection structure 30 on the temperature of the light receiving portion 40 due to radiation.

[0157] In the infrared sensor 1, the temperature of the infrared reflection structure 30 is easily stabilized to be equal to the temperature of the semiconductor substrate 10 in a sufficiently short time relative to the sampling interval of the infrared detection signal, and the temperature difference between the infrared reflection structure 30 and the semiconductor substrate 10 is small and is considered to be equal. Therefore, after the above-mentioned temperature correction process, when the infrared sensor 1 is actually operating, the measured value of the temperature of the semiconductor substrate 10 is used, and a high-precision infrared sensor 1 can be realized that can eliminate the error caused by the temperature of the infrared reflection structure 30 to the temperature of the light receiving unit 40 through radiation. In addition, the use of the infrared sensor 1 can realize a high-precision infrared imaging element.

[0158] In the above, the thermistor chip 3 is used as the temperature sensor for measuring the temperature of the semiconductor substrate 10 , but the temperature sensor is not limited thereto. A band gap type temperature sensor having a pn junction embedded in the semiconductor substrate 10 may be used as the temperature sensor, similarly to the infrared sensor 1 .

[0159] As described above, the infrared sensor 1 of the present embodiment includes: a semiconductor substrate 10; an insulating layer 20 located on the upper surface 11 of the semiconductor substrate 10; an infrared reflection structure 30 provided in the insulating layer 20; a light receiving portion 40 located above the infrared reflection structure 30; a hollow support portion 50 that hollow supports the light receiving portion 40 to form a gap between the infrared reflection structure 30 and the light receiving portion 40; and a thermoelectric conversion portion 60 that generates an infrared detection signal based on the heat generated by the light receiving portion 40. The infrared reflection structure 30 is composed of a plurality of metal vias 31 extending in the thickness direction of the insulating layer 20 in the insulating layer 20.

[0160] Thus, the incident infrared light Lin that has passed through the light receiving unit 40 and the gap is reflected by the infrared reflection structure 30 and absorbed by the light receiving unit 40 as the reflected light Lre, thereby increasing the amount of infrared absorption in the light receiving unit 40. Therefore, the infrared detection signal generated by the thermoelectric conversion unit 60 based on the heat of the light receiving unit 40 becomes larger, and the S / N ratio can be improved.

[0161] In addition, the infrared reflective structure 30 may increase in temperature due to absorption of infrared rays. Therefore, when the temperature increases, the temperature of the light receiving unit 40 is affected by radiation or the like. In the infrared sensor 1, the infrared reflective structure 30 is composed of a plurality of metal vias 31 extending in the thickness direction of the insulating layer 20 in the insulating layer 20 on the semiconductor substrate 10. Therefore, the plurality of metal vias 31 can be in contact with the semiconductor substrate 10 or closer to the semiconductor substrate 10 than in the case of the metal reflective film 30X. Therefore, the heat of the plurality of metal vias 31 is easily transferred to the semiconductor substrate 10, which can be regarded as a heat bath and has a large heat capacity and is difficult to change in temperature. That is, the deviation between the temperature of the plurality of metal vias 31 and the semiconductor substrate 10 is small, and the infrared reflective structure 30 quickly adapts to the temperature of the semiconductor substrate 10. Therefore, the temperature of the infrared reflective structure 30 is not easy to change, and is not easy to affect the temperature of the light receiving unit 40, so that the error of the infrared detection signal generated by the thermoelectric conversion unit 60 can be reduced.

[0162] Furthermore, since the plurality of metal vias 31 are in contact with or close to the semiconductor substrate 10, the temperature of the plurality of metal vias 31 quickly adapts to the semiconductor substrate 10, and the temperature of the plurality of metal vias 31 and the semiconductor substrate 10 can be regarded as the same temperature. Therefore, if the temperature of the semiconductor substrate 10, whose temperature is easy to grasp, can be easily grasped, the temperature of the plurality of metal vias 31, whose temperature is difficult to grasp, can also be known. Therefore, by grasping the temperature of the semiconductor substrate 10, the influence of the temperature of the plurality of metal vias 31 on the light receiving unit 40 can be corrected, and the error of the infrared detection signal can be further reduced.

[0163] As described above, the infrared sensor 1 of this embodiment can improve the detection accuracy of infrared rays.

[0164] In addition, in the infrared sensor 1, the plurality of metal vias 31 are in contact with the semiconductor substrate 10, so that the heat of the plurality of metal vias 31 is easily transferred to the semiconductor substrate 10. Therefore, even if a temperature disturbance is applied to the infrared reflection structure 30 formed by the plurality of metal vias 31, the temperature of the infrared reflection structure 30 can be made close to the temperature of the semiconductor substrate 10 more quickly.

[0165] [Modifications]

[0166] In the infrared reflective structure 30 described above, the plurality of metal vias 31 are separated from each other, but the present invention is not limited thereto. Parts of the outer peripheries of the plurality of metal vias 31 in a plan view may also be connected to each other.

[0167] Fig.10 This is a plan view when the infrared reflective structure 30A according to the first modification of the first embodiment is viewed from above. Fig.11This is a top view of the infrared reflective structure 30B according to the second modification of the first embodiment when viewed from above. Fig.10 as well as Fig.11 In the figure, the illustration other than the infrared reflection structure is omitted.

[0168] The infrared sensor 1 of this embodiment may include an infrared reflecting structure 30A or an infrared reflecting structure 30B instead of the infrared reflecting structure 30. Infrared sensors of embodiments other than the first embodiment described below may include an infrared reflecting structure 30A or an infrared reflecting structure 30B instead of the infrared reflecting structure 30.

[0169] like Fig.10 As shown, the plurality of metal vias 31 constituting the infrared reflective structure 30A are not separated from each other, and a portion of the periphery of the metal vias 31 when viewed from above is connected to each other. Specifically, when viewed from above, the corner of the metal via 31 is connected to the corner of the metal via 31 adjacent to the metal via 31, forming a connecting portion 31a (common portion).

[0170] In addition, if Fig.11 As shown, the multiple metal vias 31 constituting the infrared reflective structure 30B are not separated from each other, and a portion of the periphery of the metal vias 31 when viewed from above is connected to each other. Specifically, when viewed from above, one side of the metal via 31 is connected to one side of the metal via 31 adjacent to the metal via 31, forming a connecting portion 31b. In addition, in the infrared reflective structure 30B, two or more of the multiple metal vias 31 are connected to each other in a continuous manner along a predetermined direction. Therefore, the two or more metal vias constitute a plate-shaped metal via 35. Fig.11 In the example shown, the infrared reflective structure 30B is composed of a plurality of metal vias 35. Although not shown, the plurality of metal vias 35 extend in the insulating layer 20 along the thickness direction of the insulating layer 20, respectively.

[0171] exist Fig.10 as well as Fig.11 In the infrared reflection structures 30A and 30B shown, the ratio of the area occupied by the plurality of metal vias 31 to the area occupied by the insulating layer 20 is likely to increase when viewed from above. Therefore, in the infrared reflection structures 30A and 30B, the reflectivity of infrared rays is further improved, and the infrared absorption amount of the light receiving unit 40 can be increased.

[0172] In addition, since the proportion of the metal vias 31 having higher thermal conductivity than the insulating layer 20 increases, the effect of adapting the temperature of the metal vias 31 and the insulating layer 20 around the metal vias 31 to the temperature of the semiconductor substrate 10 is improved.

[0173] Therefore, by using the infrared reflective structures 30A and 30B in the infrared sensor 1, the infrared detection accuracy can be further improved.

[0174] in addition, Fig.10 as well as Fig.11 Since the infrared reflection structures 30A and 30B shown are connected only to a portion of the periphery of the metal via 31, they can be formed, like the infrared reflection structure 30, without using dry etching which is criticized for having poor productivity, but by using a via formation process that has been used in semiconductor device manufacturing in the past, such as embedding tungsten and grinding using CMP.

[0175] (Implementation Method 2)

[0176] Next, an infrared sensor according to Embodiment 2 will be described. In the following description, differences from Embodiment 1 will be mainly described, and description of common points will be omitted or simplified.

[0177] Fig.12 2 is a cross-sectional view showing an infrared sensor 101 according to Embodiment 2. Fig.12 In the figure, it is shown that Figure 2A The cross section of the infrared sensor 101 at the same position. Fig.12 As shown, the infrared sensor 101 of the present embodiment is different from the infrared sensor 1 of the first embodiment in that it further includes a gate electrode 112 located on the upper surface 11 of the semiconductor substrate 10 .

[0178] The gate electrode 112 is composed of, for example, a gate polysilicon layer and a gate oxide film located between the gate polysilicon layer and the semiconductor substrate 10. The gate electrode 112 has a structure corresponding to a gate electrode of a MOSFET.

[0179] In the infrared sensor 101, the end surfaces 32 of the plurality of metal vias 31 on the semiconductor substrate 10 side are in contact with the gate electrode 112. The plurality of metal vias 31 are thermally connected to the semiconductor substrate 10 via the gate electrode 112.

[0180] In this way, in the infrared sensor 101, the plurality of metal vias 31 are bonded to the semiconductor substrate 10 via the thin gate oxide film of the gate electrode 112, so that the heat of the plurality of metal vias 31 is easily transferred to the semiconductor substrate 10. Therefore, even if a temperature disturbance is applied to the infrared reflection structure 30 composed of the plurality of metal vias 31, the temperature of the infrared reflection structure 30 can be made close to the temperature of the semiconductor substrate 10 more quickly.

[0181] (Implementation 3)

[0182] Next, an infrared sensor according to Embodiment 3 will be described. In the following description, differences from Embodiments 1 and 2 will be mainly described, and description of common points will be omitted or simplified.

[0183] Fig.13A This is a cross-sectional view showing an infrared sensor 201 according to the third embodiment. Fig. 13B This is a cross-sectional view showing a part of the infrared reflection structure 230 included in the infrared sensor 201 according to the third embodiment. Fig. 13C This is a plan view when the infrared sensor 201 according to the third embodiment is viewed from above. Fig.13A Shown in Fig. 13C The infrared sensor 201 shown is a cross section of the metal wiring 84, the metal wiring 83, the metal wiring 71, the cold junction metal electrode 63p, the P-type semiconductor 65p, the hot junction metal electrode 61, the hot junction metal electrode 62, the P-type semiconductor 66p, and the cold junction metal electrode 64p cut along a line passing through them in this order. Fig. 13B FIG. 2 shows a part of a cross section of the infrared sensor 201 cut along the infrared reflection structure 230 near the cold junction metal electrode 64p. Fig. 13C In FIG. 4 , the positions of the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p which are actually covered by the insulating film 41 are indicated by thick dotted lines. Fig. 13C In FIG. 1 , the outline of the semiconductor 42 in the light receiving portion 40 , which is actually covered by the insulating film 41 or the like, and the outlines of the plurality of metal vias 231 , 232 constituting the infrared reflection structure 230 are indicated by dotted lines.

[0184] like Figures 13A to 13C As shown, the infrared sensor 201 of this embodiment is different from the infrared sensor 1 of the first embodiment in that it further includes an infrared reflection structure 230 and a gate electrode 212 on the semiconductor substrate 10. The infrared reflection structure 230 is an example of a second infrared reflection structure.

[0185] The infrared reflection structure 230 is arranged to surround the light receiving unit 40 and the gap 51 in a plan view. The infrared reflection structure 230 is composed of a plurality of metal vias 231 and 232. Each of the plurality of metal vias 231 and 232 is composed of a high melting point metal such as tungsten. The plurality of metal vias 231 and 232 are located on the side of the gap 51 (in a direction perpendicular to the up and down direction).

[0186] The plurality of metal vias 231, 232 are arranged in a rectangular ring shape so as to surround the light receiving portion 40 and the gap 51 when viewed from above. In addition, the arrangement of the plurality of metal vias 231, 232 is not limited to a rectangular ring shape, but may be other shapes. In addition, there may be a portion of the ring (for example, one side or two sides of the rectangle) where the plurality of metal vias 231, 232 are not arranged. In addition, the plurality of metal vias 231, 232 are arranged in a row in the longitudinal or transverse direction, but may also be arranged in two or more rows.

[0187] The plurality of metal vias 231 and 232 are formed in the insulating layer 20 so as to extend in the thickness direction of the insulating layer 20. In addition, the plurality of metal vias 231 and 232 are formed in the insulating layer 20 so as to span from the insulating film 21 to the insulating film 22. In the present embodiment, the plurality of metal vias 231 and 232 are separated from each other via the insulating films 21 and 22. In addition, the plurality of metal vias 231 and 232 may be connected to each other at a part of the periphery when viewed from above.

[0188] The thickness of each metal via 231 and the metal via 232 (the length in the vertical and horizontal directions when viewed from above) is, for example, greater than 0.5 μm and less than 1 μm. The distance between two adjacent metal vias 231, or two adjacent metal vias 231 and metal vias 232 (the length of the gap when viewed from above) is, for example, greater than 0.5 μm and less than 1 μm. Thus, the spacing between the plurality of metal vias 231 and 232 is greater than 0.5 μm and less than 1 μm, and is thinner than 1 / 10 and less than 1 / 5 of the wavelength of the infrared light received near 10 μm. Therefore, the infrared reflection structure 230 composed of the plurality of metal vias 231 and 232 can show optical properties similar to those of a uniformly formed metal reflection film.

[0189] The incident infrared light Lin is reflected by the infrared reflective structure 30 in the incident direction, but a part of it is also reflected toward the side of the gap 51. The infrared reflective structure 230 reflects the reflected light Lre reflected toward the side of the gap 51, and the reflected light Lre is also absorbed by the light receiving unit 40. Therefore, the infrared absorption amount of the light receiving unit 40 can be increased.

[0190] In addition, when a plurality of infrared sensors 201 are arranged in an array and used in an infrared imaging element, the infrared reflection structure 230 can reflect at least a portion of the reflected light Lre reflected toward the side of the gap 51 in a manner that does not invade the adjacent infrared sensor 201. That is, in the infrared imaging element, mixing of infrared detection information between adjacent pixels can be suppressed.

[0191] The infrared reflection structure 230 includes a metal via 232 that contacts the cold contact metal electrodes 63p, 63n, 64p, 64n, and a metal via 231 that does not contact the cold contact metal electrodes 63p, 63n, 64p, 64n. The upper end surface of the metal via 232 contacts the cold contact metal electrodes 63p, 63n, 64p, 64n, and the upper end surface of the metal via 231 contacts the insulating film 41.

[0192] The metal via 232 in contact with the cold junction metal electrodes 63p, 63n, 64p, 64n stabilizes the temperature of the cold junction metal electrodes 63p, 63n, 64p, 64n to the same extent as the semiconductor substrate 10 regarded as a heat bath, and stabilizes the temperature difference between the cold junction metal electrodes 63p, 63n, 64p, 64n and the hot junction metal electrodes 61, 62 on the light receiving portion 40.

[0193] The end surface of the metal via 232 on the semiconductor substrate 10 side contacts the gate electrode 212 located between the metal via 232 and the semiconductor substrate 10. The gate electrode 212 is composed of, for example, a gate polysilicon layer and a gate oxide film located between the gate polysilicon layer and the semiconductor substrate 10. The gate electrode 212 has a structure equivalent to that of a gate electrode of a MOSFET. The metal via 232 is connected to the semiconductor substrate 10, which serves as a heat bath, via the gate polysilicon layer and the gate oxide film of the gate electrode 212. The reason for passing through the gate oxide film is to suppress the weak infrared detection signal from leaking to the semiconductor substrate 10 via the cold junction metal electrodes 63p, 63n, 64p, 64n. The gate oxide film has a low thermal conductivity but is thin, so the thermal resistance is small. For example, the length of the insulating layer 20 in the thickness direction of the metal via 232 and the thermal conductivity are set to 4 μm and 178 W / (m·K), respectively, the thickness and thermal conductivity of the gate polysilicon layer are set to 0.13 μm and 32 W / (m·K), respectively, and the thickness and thermal conductivity of the gate oxide film are set to 0.005 μm and 1.4 W / (m·K). In this case, the thermal resistance from the upper surface of the metal via 232 through the gate electrode 212 to the semiconductor substrate 10 can be suppressed to increase by about 30% compared with the case where there is no gate electrode 212 and the metal via 232 is in contact with the semiconductor substrate 10.

[0194] The end surface of the metal via 231 on the semiconductor substrate 10 side that is not in contact with the cold junction metal electrodes 63p, 63n, 64p, 64n is as shown in FIG. Fig. 13B In addition, the metal via 231 may not be in contact with the semiconductor substrate 10. For example, the gate electrode 212 may be disposed between the metal via 231 and the semiconductor substrate 10. In addition, the metal via 231 may be formed only in the insulating film 22 in the insulating layer 20.

[0195] In addition, the infrared reflective structure 230 may not include the metal via 232 .

[0196] (Implementation 4)

[0197] Next, an infrared sensor according to Embodiment 4 will be described. In the following description, differences from Embodiments 1 to 3 will be mainly described, and description of common points will be omitted or simplified.

[0198] Fig.14A It is a cross-sectional view showing an infrared sensor 301 according to a fourth embodiment. Fig. 14B This is a plan view when the infrared sensor 301 according to the fourth embodiment is viewed from above. Fig.14A Shown in Fig. 14B In the infrared sensor 301 shown, the metal wiring 84, the cold junction metal electrode 63p, the P-type semiconductor 65p, the hot junction metal electrode 61, the hot junction metal electrode 62, the P-type semiconductor 66p, and the cold junction metal electrode 64p are cut by lines passing through them in this order. Fig. 14B In FIG. 4 , the positions of the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p which are actually covered by the insulating film 41 are indicated by thick dotted lines. Fig. 14B In FIG. 4 , the outline of the semiconductor 42 in the light receiving portion 40 , which is actually covered by the insulating film 41 or the like, and the outlines of the plurality of metal vias 231 , 232 , and 333 constituting the infrared reflection structure 330 are indicated by dotted lines.

[0199] like Fig.14A as well as Fig. 14B As shown, the infrared sensor 301 of this embodiment is different from the infrared sensor 201 of the third embodiment in that it includes a semiconductor substrate 310 having a high-concentration impurity region 313 formed on the semiconductor substrate 10 instead of the semiconductor substrate 10. In addition, the infrared sensor 301 is different from the infrared sensor 201 of the third embodiment in that it includes an infrared reflection structure 330 instead of the infrared reflection structure 230. In addition, the infrared sensor 301 is different from the infrared sensor 201 of the third embodiment in that it does not include the metal wirings 71 and 83 and the metal via 81. The infrared reflection structure 330 is an example of the second infrared reflection structure. In addition, the semiconductor substrate 310 is an example of a substrate.

[0200] In the infrared sensor 301, the end surface 32 on the semiconductor substrate 310 side of the plurality of metal vias 31 constituting the infrared reflective structure 30 located below the light receiving unit 40 is in contact with a high-concentration impurity region 313 doped with impurities at a high concentration in the semiconductor substrate 310. The high-concentration impurity region 313 included in the semiconductor substrate 310 is located at the upper end of the semiconductor substrate 310 and below the infrared reflective structure 30.

[0201] The impurity concentration of the high-concentration impurity region 313 is higher than that of a portion of the semiconductor substrate 310 below the high-concentration impurity region 313. The impurity concentration of the high-concentration impurity region 313 is, for example, 10 19 cm -3 Above and 10 21 cm -3 The purpose is to utilize the impurity described in Non-Patent Document 1 to obtain 10 20 cm -3 For example, a silicon substrate doped with boron (B) at a high concentration has a property of having a higher reflectivity of infrared light than an undoped silicon substrate. The inventors of the present application have found that this property can be applied to the infrared sensor 301 of the present embodiment. That is, the incident infrared light Lin that is not completely reflected but transmitted through the plurality of metal vias 31 can be reflected on the surface of the high-concentration impurity region 313 of the semiconductor substrate 310 and returned to the light receiving unit 40. Therefore, the amount of infrared light absorbed in the light receiving unit 40 can be increased.

[0202] The infrared reflection structure 330 is composed of a plurality of metal vias 231, 232, and 333, and includes a metal via 333 instead of the metal via 232 connected to the cold junction metal electrode 63p in the infrared reflection structure 230 of the third embodiment. The upper end surface of the metal via 333 is connected to the cold junction metal electrode 63p. In addition, the lower end surface of the metal via 333 is connected to the source 80s of the transistor 80. That is, the metal via 333, which is a structure described in the third embodiment in which the cold junction metal electrode 63p is connected to the semiconductor substrate 310 which can be regarded as a heat bath so that the temperature of the cold junction metal electrode 63p is stabilized to be equal to the temperature of the semiconductor substrate 310, is also used for the electrical connection between the cold junction metal electrode 63p and the transistor 80. That is, the source 80s of the transistor 80 is electrically connected to the cold junction metal electrode 63p via the metal via 333. Thus, the transistor 80 that switches whether to output the infrared detection signal from the infrared sensor 301 can be arranged to be located below the cold junction metal electrode 63p. That is, when viewed from above, the transistor 80 overlaps with the cold junction metal electrode 63p. Thus, the area of ​​the infrared sensor 301 when viewed from above can be reduced, and the infrared sensor 301 can be miniaturized. In addition, by using the infrared sensor 301 in an infrared sensor array, a small infrared sensor array can be provided.

[0203] Furthermore, the semiconductor substrate 10 of the infrared sensor of Embodiments 1 to 3 may be provided with a high-concentration impurity region 313. Furthermore, in the infrared sensor 201 of Embodiment 3, the metal wirings 71 and 83 and the metal via 81 may not be provided, and the source 80s may be electrically connected to the cold junction metal electrode 63p via the metal via 333.

[0204] (Other embodiments)

[0205] The infrared sensor of the present disclosure is described above based on the embodiments, but the present disclosure is not limited to these embodiments. As long as it does not deviate from the main purpose of the present disclosure, the various modifications thought of by those skilled in the art are applied to the embodiments to obtain the scheme, and other schemes constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present disclosure.

[0206] For example, in the above embodiment, the end faces 32 of the plurality of metal vias 31 are in contact with the semiconductor substrate 10 , 310 or the gate electrode 212 , but the present invention is not limited thereto. A thin film or the like may be disposed between the plurality of metal vias 31 and the semiconductor substrate 10 , 310 or the gate electrode 212 .

[0207] In addition, for example, in the above-mentioned embodiment, the thermoelectric conversion unit 60 is a thermoelectric conversion element of a thermopile type, but the present invention is not limited thereto. The thermoelectric conversion unit 60 may be a thermoelectric conversion element having a thermoelectric conversion structure other than a thermopile structure.

[0208] Industrial Applicability

[0209] The infrared sensor disclosed in the present invention can be used for various purposes including the purposes of conventional infrared sensors, such as infrared imaging elements. In the infrared sensor disclosed in the present invention, a non-cooled and high-precision infrared sensor can be achieved, and therefore, it can also be applied to a drive monitor that can detect people at night, and a simple thermal imager that can efficiently measure collective body temperatures, etc.

[0210] Description of symbols

[0211] 1. 1X, 101, 201, 301 infrared sensor

[0212] 2 Packaging

[0213] 3 Thermistor Chip

[0214] 4 Bonding wire

[0215] 5. Lid

[0216] 6 Infrared sensor package

[0217] 10.310 semiconductor substrate

[0218] 11 Upper surface

[0219] 20 Insulation layer

[0220] 21, 22, 41 Insulation film

[0221] 23. Protective film

[0222] 25 Through Holes

[0223] 30, 30A, 30B, 230, 330 infrared reflection structure

[0224] 30X Metallic Reflective Film

[0225] 31, 35, 81, 81b, 82, 82b, 231, 232, 333 metal vias

[0226] 31a, 31b Connection part

[0227] 32 End face

[0228] 40 Light receiving part

[0229] 42 Semiconductors

[0230] 50 Hollow support

[0231] 51 Gap

[0232] 53 Recessed Space

[0233] 55 Sacrificial Layer

[0234] 60 Thermoelectric conversion unit

[0235] 61, 62 Hot junction metal electrode

[0236] 63n, 63p, 64n, 64p Cold junction metal electrode

[0237] 65n, 66n N-type semiconductor

[0238] 65p, 66p P-type semiconductor

[0239] 67, 71, 83, 84 Metal wiring

[0240] 80 transistors

[0241] 80d Drain

[0242] 80g Grid

[0243] 80s Source

[0244] 80w Trap

[0245] 91 substrate

[0246] 92 Constant temperature bath

[0247] 93 Blackbody furnace

[0248] 94 Lens

[0249] 95 Shell

[0250] 96 Amplifier IC

[0251] 112, 212 gate electrode

[0252] 313 High concentration impurity area

[0253] Lin Infrared incident light

[0254] Lre reflected light

Claims

1. An infrared sensor comprising: substrate; an insulating layer, located on the upper surface of the substrate; a first infrared reflection structure, disposed in the insulating layer; A light receiving part, located above the first infrared reflecting structure; A hollow supporting portion for hollowly supporting the light receiving portion so as to form a gap between the first infrared reflecting structure and the light receiving portion; as well as a thermoelectric conversion unit that generates an infrared detection signal based on the heat generated by the light receiving unit, The first infrared reflection structure is composed of a plurality of first metal vias extending in the insulating layer along a thickness direction of the insulating layer.

2. The infrared sensor according to claim 1, further comprising a second infrared reflection structure arranged so as to surround the light receiving portion and the gap in a plan view, The second infrared reflection structure is composed of a plurality of second metal vias extending in the insulating layer along a thickness direction of the insulating layer.

3. The infrared sensor according to claim 2, The thermoelectric conversion unit is a thermopile type thermoelectric conversion element having a hot junction metal electrode and a cold junction metal electrode. One of the plurality of second metal vias is connected to the cold junction metal electrode.

4. The infrared sensor according to claim 3, The device further comprises a transistor for switching whether the infrared detection signal generated by the thermoelectric conversion unit is output from the cold junction metal electrode. The transistor is formed on the substrate. The input terminal of the transistor is electrically connected to the cold junction metal electrode via the one second metal via.

5. The infrared sensor according to any one of claims 1 to 4, Parts of outer circumferences of the plurality of first metal vias in a plan view are connected to one another.

6. The infrared sensor according to any one of claims 1 to 4, End surfaces of the plurality of first metal vias on the substrate side are in contact with the substrate.

7. The infrared sensor according to any one of claims 1 to 4, further comprising a gate electrode located on the upper surface of the substrate, End surfaces of the plurality of first metal vias on the substrate side are in contact with the gate electrode.

8. The infrared sensor according to any one of claims 1 to 4, The substrate has a high-concentration impurity region doped with impurities, The high-concentration impurity region is located at the upper end of the substrate and below the first infrared reflection structure. The high-concentration impurity region has an impurity concentration higher than an impurity concentration in a portion of the substrate below the high-concentration impurity region.

9. The infrared sensor according to any one of claims 1 to 4, The hollow support portion has a phononic crystal structure.

Images