JP2000292257A - Thermal infrared sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal infrared sensor whose high sensitivity can be realized even when a pixel size is reduced and whose high definition can be realized easily. SOLUTION: In this infrared sensor, support legs 2 are arranged in the lower part of a light receiving part 1 which occupies the nearly whole face of a pixel size, a thermoelectric material 4 which is installed at the light receiving part 1 is connected, via a contact 6, to metals which are buried in the support legs 2 and whose thermal conductivity is small, and the support legs 2 are extended to the outside of the range of a pixel. At this time, the support legs 2 are arranged so as to be oblique to the arrangement direction B of the pixel. Then, when the support legs 2 are extended to the outside of the range of the pixel, they do not come into contact with the support legs 2' of an adjacent pixel light receiving part 1'. The conduction of heat from the light receiving part 1 can be reduced, and a fill factor (ratio of light receiving area to pixel area) which is large can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal infrared sensor, and more particularly, to a thermal infrared sensor having a thermal isolation structure.

[0002]

2. Description of the Related Art As an infrared sensor, a thermal infrared sensor having a heat separation structure is known. In this thermal infrared sensor, a large number of light receiving sections arranged in an array are thermally separated from the substrate by being supported separately from the substrate by corresponding supporting legs having low thermal conductivity. The thermal infrared sensor operates at room temperature, has the advantage of low noise at room temperature, and has the advantage of high sensitivity, and is particularly suitable for quantum infrared sensors that require sensor cooling at the liquid nitrogen temperature level. It has a comparable equivalent noise temperature (NETD). For this reason, in recent years, it has attracted attention, and its development competition is currently intensifying. This type of two-dimensional infrared sensor is being put to practical use, for example, as a night vision device, a fire detector, a night monitoring camera, a temperature measuring device, or a defense device.

In a thermal type two-dimensional infrared sensor, a large number of light receiving portions for receiving infrared rays are two-dimensionally arranged, and an electric signal corresponding to the amount of received light is sequentially read from each light receiving portion on the substrate side below the light receiving portion. A scanning circuit in which the scanning circuit portions are two-dimensionally arranged is formed.

A conventional thermal two-dimensional infrared sensor having a thermal separation structure will be described with reference to FIG. This thermal infrared sensor is described, for example, in SPIE Magazine, Vol.
9 “Infrared Imaging Systems” (1
992) /p.379, “Status of Uncooled Infrared Imagers” (SPIE Vol.168
9 “Infrared Imaging Systems” (1992) / 379,
"Status of uncooled infrared imagers"). In this example, as shown in FIG. 6, a diaphragm structure supported by two support legs 2 mainly made of a silicon nitride film on a substrate on which a signal processing circuit (scanning circuit) 3 made of a bipolar transistor is formed. A corresponding light receiving section 1 is formed. The signal circuit 3 has a size corresponding to the light receiving unit 1 and is electrically connected to the corresponding light receiving unit 1.

In the above-mentioned conventional thermal two-dimensional infrared sensor,
The light receiving unit 1 held apart from the substrate by the support legs 2 of each pixel has an infrared absorbing film that absorbs infrared light and a bolometer whose resistance value changes with temperature. Infrared rays are emitted from the detection target and focused on the sensor surface by an infrared lens. When the infrared absorbing film of each pixel absorbs infrared light, the temperature of the light receiving portion of each pixel formed of a thin film increases. The bolometer functions as a thermometer, and the temperature rise of the light receiving unit 1 is output as a change in the resistance value of the bolometer. In this way, electric signals generated by infrared rays having a two-dimensional intensity distribution on the pixel array are sequentially taken out of the sensor via the scanning circuit formed on the substrate surface.

[0006] The infrared light receiving sensitivity of the sensor is proportional to the temperature coefficient of resistance of the bolometer and the amount of received light, and is inversely proportional to the thermal conductivity of the supporting leg. Here, the amount of received light is proportional to the absorptance and the light receiving area of the infrared absorbing film.

[0007]

In general, an infrared two-dimensional sensor increases the spatial resolution as the number of pixels increases, but if the number of pixels is too large, the sensor size increases and the infrared lens diameter increases. Connect. In particular, an infrared lens is an expensive material, and it is necessary to reduce the sensor size as much as possible to obtain a low-cost sensor.

[0008] Higher resolution, which keeps the sensor size below a predetermined value and increases the number of pixels, involves a reduction in the area of the pixel size, and a reduction in the sensitivity of each light-receiving unit accompanying the reduction in the area. This is because, as shown in FIG. 6, in the conventional heat-separation type light-receiving unit structure, the supporting leg 2 is substantially in the same plane as the light-receiving unit 1, and the area of the light-receiving unit 1 is reduced due to the support leg 2. This is because it is considerably smaller than the area. In addition, since the reduction in the pixel size accompanying the high definition also results in a reduction in the length of the support leg 2 that supports the light receiving unit 1, the width of the support leg 2 must be reduced in order to maintain a small thermal conductivity. Required. But,
In order to support the thermal isolation structure, the support legs 2
There is a limit to the reduction of the width. That is, the reduction in the pixel size is generally accompanied by an increase in thermal conductivity, resulting in a decrease in sensitivity.

In order to maintain a certain level of light receiving sensitivity under a situation where a decrease in the light receiving area is unavoidable, the fill factor, that is, the pixel area, must be increased along with the improvement of the infrared absorptance and the temperature coefficient of resistance of the bolometer. It is required to improve the ratio of the light receiving area to that of the support legs and to reduce the thermal conductivity of the support legs. However, there is a limit in maintaining the light receiving sensitivity only by these measures.

[0010] In view of the above, it is an object of the present invention to provide a thermal infrared sensor that can realize high sensitivity of a light receiving section even if the pixel size is reduced and that can easily achieve high definition.

[0011]

In order to achieve the above object, the thermal infrared sensors of the present invention are arranged in an array at a predetermined pitch apart from each other, and each of them receives an infrared ray to raise the temperature. In a thermal infrared sensor in which the plurality of light receiving sections are provided, and the light receiving sections are supported separately from the substrate, supporting legs supporting the respective light receiving sections are disposed between the light receiving section and the substrate, In addition, it extends in a direction substantially parallel to the substrate surface.

According to the thermal infrared sensor of the present invention, the support leg is disposed between the light receiving portion and the substrate, so that the fill factor can be improved, and the support leg can be arranged substantially parallel to the substrate surface. By arranging and properly selecting the length, the thermal conductivity between the light receiving unit and the substrate can be suppressed low.

In a preferred aspect of the present invention, the wiring built in the support leg is electrically connected to an electrode of a thermoelectric material of the light receiving section via a contact located in the corresponding light receiving section.

In the thermal infrared sensor according to the present invention, the support legs having an appropriate length are employed. (1) The support legs extend substantially parallel to and separate from the support legs of the adjacent pixels, and have a pixel pitch. A configuration having the above length, (2) a configuration in which the support legs are arranged within the pixel pitch, and a configuration in which the support legs are bent in a plane parallel to the substrate surface, and (3) a pair of the support legs corresponds to each light receiving unit. The pair of support legs extend in mutually opposite directions from the corresponding light receiving portion; and (4) the pair of support legs are disposed line-symmetrically corresponding to the light receiving portions. It is preferable that the pair of support legs have any of a configuration having a length equal to or greater than the predetermined pitch, and a configuration in which the pair of support legs are bent in a plane parallel to the substrate. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments of the present invention with reference to the drawings. FIG.
1A and 1B show a thermal infrared sensor according to a first embodiment of the present invention, wherein FIG. 1A is a schematic perspective view, and FIG. 1B is a plan view. The thermal infrared sensor according to the present embodiment has a light receiving unit 1 that receives infrared rays and rises in temperature.
Is disposed below the surface of the light receiving unit 1, and the light receiving unit 1 is thermally separated from the substrate by the support leg 2. The wiring built in the support leg 2 and the metal electrode 5 of the thermoelectric material 4 of the light receiving section 1 are connected to a contact 6 located in a lower layer in the light receiving section 1.
To make electrical connection. The support legs 2 are arranged so as to be substantially parallel to the substrate surface, and have such a length that sufficient thermal insulation can be obtained. For easy understanding, a scanning circuit portion corresponding to the light receiving unit 1 formed on the substrate surface is denoted by reference numeral 3. The scanning circuit portion 3 corresponding to one light receiving portion has substantially the same size as the light receiving portion, and each scanning circuit portion 3 has a size corresponding to the pixel size and is arranged corresponding to the light receiving portion 1. ing. Each light receiving unit 1 is supported via a supporting leg 2 at a position of a corresponding scanning circuit portion 3,
A wiring built in the support leg 2 connects the light receiving section to the corresponding scanning circuit section 3.

As shown in FIG. 1B, when viewed in a direction perpendicular to the substrate surface, a direction A in which the support legs 2 extend is an X direction which is an arrangement direction of one pixel of a two-dimensionally arranged pixel array. B is arranged so as to cross diagonally. The pair of support legs 2 extending from one light receiving unit 1 are respectively extended in parallel and linearly with a corresponding support leg 2 ′ of the adjacent light receiving unit 1 ′ at a predetermined separation distance. I have. Each support leg 2 has a length of about twice the pixel pitch, and extends to and is supported on a corresponding scanning circuit portion of an adjacent light receiving unit in one connected light receiving unit. .

By adopting the support legs 2, 2 'having the above structure, the light receiving unit 1, which has an area substantially full of the pixel size,
1 ′ is held away from the substrate surface,
2 ′ makes it possible to suppress heat conduction. Thus, the light-receiving unit efficiently raises the temperature, and thus can detect infrared rays with high sensitivity. Here, as the thermoelectric material 4 for temperature detection, various types can be adopted, for example,
Examples include a bolometer type using a temperature change in resistance, a pyroelectric type using spontaneous polarization or a temperature change in dielectric constant, and a thermocouple type using thermoelectromotive force.

With reference to FIG. 2, a method of manufacturing the thermal infrared sensor according to the above embodiment will be described with reference to a diaphragm structure employing a bolometer as a thermoelectric material. First,
A two-dimensional scanning circuit 8 is formed on a semiconductor substrate 7 as shown in FIG. 2
The dimensional scanning circuit 8 has a structure in which scanning circuit portions (3 in FIG. 1) corresponding to the respective light receiving units are arranged in an array. On the front side of the scanning circuit 8, a wiring 9 usually made of aluminum or the like is provided.
And is electrically connected to each of the lower circuit elements. The upper portion of the wiring 9 is covered with an interlayer insulating film 10 such as a silicon oxide film, and the surface of the interlayer insulating film 10 has an uneven shape along the shape of the base when formed.

The surface of the interlayer insulating film 10 is flattened by removing its concavo-convex shape by CMP polishing (chemical mechanical polishing) or the like. Next, a first positive photosensitive polyimide is spin-coated on the wafer surface to a thickness of about 3 μm, and a portion of the interlayer insulating film 10 on the aluminum wiring 9 is exposed by exposure, thereby forming a first sacrificial layer made of polyimide. 11 is formed. Next, as shown in FIG. 1B, a second insulating film 12 made of a silicon nitride film or a silicon oxide film is
It grows to a thickness of 500 nm by the VD method. Note that FIG.
(B) to (d) are cross-sectional views taken along the IB-IIB direction along the extension direction A of the support leg in FIG. 1B.

Next, the second insulating film 12 and the interlayer insulating film 10 on the bottom surface of the opening of the first polyimide sacrificial layer 11 are opened at 1 μm square by using a photoresist method and a selective etching method. Is formed to expose the first through hole 13.

Next, using a photoresist method and a selective etching method, a leg metal 14 made of titanium wiring or the like and having a width of about 1 μm and covering the first through hole 13 is formed. At this time, as shown in FIG. 1B, the two leg metals 14 are in a direction obliquely intersecting with the X direction, which is the pixel arrangement direction, and on the light receiving unit side of the two leg metals 14. The tips extend linearly in such a direction that they approach each other.

Next, the leg metal 14 is again covered with a third insulating film 15 made of a silicon nitride film or a silicon oxide film having a thickness of 500 nm by the plasma CVD method.
The third insulating film 15 and the second insulating film 12 are formed along the leg metal 14 by using a photoresist method and a selective etching method.
Is selectively etched to a width of 2 μm to form elongated support legs 2 as shown in FIG.

Thereafter, as shown in FIG. 2B, a positive photosensitive polyimide is again spin-coated to a thickness of about 3 μm,
The third insulating film 15 on the tip of the leg metal 14 is exposed by an exposure and development process. Next, on the opening of the second sacrifice layer 16 where the third insulating film 15 is exposed and on the second sacrifice layer 16,
A fourth insulating film 17 made of a silicon nitride film or a silicon oxide film is grown to a thickness of 300 nm by a plasma CVD method.

Further, a second through hole 18 of 1 μm square is formed in the fourth and third insulating films 17 and 15 on the bottom surface of the opening of the second sacrificial layer 16 by using a photoresist method and a selective etching method. The tip of the part metal 14 is exposed. A slit-shaped metal electrode 5 having a width of about 1 μm is formed on the end of the light receiving portion including the exposed portion of the leg metal tip by, for example, titanium sputtering, a photoresist method, and a selective etching method. From above, vanadium oxide (V ₂ O ₅ )
Bolometer material such as 100n thickness by sputtering method
m, followed by a heat treatment at about 350 ° C. in a reducing atmosphere to change the V ₂ O ₅ phase to a low resistivity VO ₂ phase. Thereby, the temperature coefficient of resistance is -2% / K,
The semiconductor phase vanadium oxide 19 having a large resistance change with temperature is obtained.

Subsequently, as shown in FIG. 2C, a silicon oxide film 20 is formed to a thickness of 50 nm by a plasma CVD method.
To grow. Thereafter, the silicon oxide film 20 and the two layers of the VO ₂ phase vanadium oxide were formed at a pitch of 37 μm by about 35 μm × by using a photoresist method and a selective etching method.
A bolometer 19A made of vanadium oxide as a thermoelectric material is formed by processing into a 35 μm square rectangle. Thereby, via the second through hole 18 and the metal electrode 5,
The electrical contact between the leg metal 14 and the bolometer 19A is realized.

Next, a thickness of 3
A bolometer 1 covered with a silicon oxide film 20 by growing a fifth insulating film 21 made of a 00 nm silicon nitride film or the like.
Cover 9A. Further, titanium nitride or the like having a thickness of about 15 nm serving as an infrared absorbing film is deposited by sputtering to cover the upper part of the thermoelectric material. The deposited film is processed into a rectangular pattern (with a pixel size pitch) covering the bolometer by using a photoresist method and a selective etching method to form the infrared absorbing film 22.

Further, as shown in FIG. 2D, a slit-like opening 23 having a width of about 1 μm surrounding the bolometer 19A as a thermoelectric material is formed using a photoresist method and a selective etching method. Thereby, each light receiving unit is structurally separated from each other. Next, the second and first polyimide sacrificial layers 16 and 11 are successively selectively removed by ashing using an oxygen plasma gas. by this,
The light receiving section 1 including the bolometer 19A is supported by the support leg 2 having the leg metal 14 therein, and a bridge-like heat isolation structure having a cavity 24 between the light receiving section 1 and the substrate is formed. Thereby, each light receiving section 1 is supported independently and hollowly by the corresponding scanning circuit portion 3 and the corresponding supporting leg 2 formed on the substrate. In the present embodiment, 3
Despite the small pixel size of 7 μm square, the size of the light receiving portion is as large as 35 μm × 35 μm, and a fill factor of about 90% is obtained, and the thermal conductivity from the light receiving portion is 0.15 μW / K. A thermal infrared sensor having a simple thermal isolation structure can be obtained.

The wiring built in the support leg 2 supporting the light receiving section 1 and the slit-shaped metal electrode 5 of the thermoelectric material 4 of the light receiving section 1
Is electrically connected via a contact 6 located below the light receiving section 1. Therefore, a necessary voltage can be applied to the thermoelectric material 4 through the wiring in the two support legs 2, and
A signal serving as image information can be extracted. The slit-shaped metal electrode 5 of the thermoelectric material 4 is provided to reduce the contact resistance between the thermoelectric material 4 and the leg metal 14 when the contact resistance is too large. By appropriately expanding the contact area, the contact resistance can be reduced to a required level. Since the leg metal 14 and the metal electrode 5 are metal, the contact resistance is sufficiently smaller than the resistance of the thermoelectric material 4.

As described above, the cavity 24 is formed between the light receiving section 1 and the substrate. The infrared rays are absorbed by the light receiving unit 1 and stored as heat energy. The thickness of the polyimide film is reduced by a baking step, an exposure step, and a developing step after spin coating, and is reduced to 3 μm or less, for example, about 2 to 3 μm. Normally, since the thermal infrared sensor is housed in a vacuum package, heat does not diffuse through a vacuum gap, but mostly diffuses through the support legs 2. Therefore,
The temperature of the light receiving section 1 rises in inverse proportion to the thermal conductivity of the support leg 2. As described above, the light receiving section 1 absorbs infrared rays, is held hollow by the elongated support legs 2, and is almost thermally separated from the substrate. For this reason, the temperature of the light receiving section increases in inverse proportion to the thermal conductivity of the support leg 2. The temperature rise is converted into an electric signal by a thermoelectric material 4 such as a bolometer.

For example, the resistance value of a bolometer changes as the temperature rises. Therefore, when a bolometer is used as a thermoelectric material, the light receiving sensitivity of the infrared sensor is proportional to the temperature coefficient of resistance and the amount of received light of the bolometer and inversely proportional to the thermal conductivity of the legs. Here, the amount of received light is
It is proportional to the absorptance and the light receiving area of the infrared absorbing film. Therefore, in order to increase the sensitivity of the sensor, it is preferable that the light receiving area is large and the thermal conductivity of the support leg 2 is small.

In the structure of this embodiment, since the support leg 2 is disposed below the light receiving portion 1, the light receiving portion 1 and the support leg 2 are not located on the same plane, so that the support leg 2 has a pixel area. The area of the light receiving section 1 can be maximized with a pixel having a predetermined area without occupying a part.

In the thermal infrared sensor, from the structure in which the light receiving portion and the scanning circuit are formed in a repetitive pattern, as can be understood from FIG. In this case, when the support leg 2 is extended out of the pixel range, the support leg 2 comes into contact with the support leg 2 ′ of an adjacent pixel. Due to this contact, the thermal conductivity between the corresponding light receiving sections increases, causing sensitivity deterioration and crosstalk. According to the present invention, since the extension direction A of the support leg 2 extending from a similar position of each light receiving unit 1 is arranged so as to be inclined from the arrangement direction B of the light receiving units 1,
The support legs 2, 2 'in similar positions with respect to do not touch each other.

By providing the supporting legs 2 and 2 'below the light receiving portion, the supporting legs using a metal having low thermal conductivity such as titanium as a wiring material can be extended to a required length outside the pixel range. In addition, the thermal conductivity of the support leg 2 can be reduced to a level necessary for increasing the sensitivity of the light receiving unit 1.

The supporting leg 2 has a central titanium conductive film 14 having a width of about 1 μm and a thickness of about 0.1 μm, and an insulating film 1 made of a silicon oxide film or a silicon nitride film covering the titanium conductive film 14.
2, 14 have a width of 2 μm and a thickness of about 1 μm as a whole. Here, the strength of the support leg 2 is sufficiently maintained by the structure in which the support leg 2 extends substantially linearly in one direction.
The support leg 2 can stably hold the light receiving unit 1 in a hollow state without being depressed.

In the case of a conventional infrared sensor having a pixel size of 37 μm square and employing the conventional structure shown in FIG. 6, for example, the fill factor is about 65% and the thermal conductivity is about 0.3 μW / K. It has a thermal isolation structure of a degree, and its sensitivity is insufficient, which is about two-thirds of the desired value. However, in the present embodiment, the fill factor is about 1.4 times and the thermal conductivity is about half as compared with the conventional example, so that the sensitivity is improved to about 2.5 times, which is sufficient for practical use. Sensitivities can be improved.

In the thermal infrared sensor of the above embodiment,
As described above, even if the pixel size is reduced, the reduction in the amount of received light can be minimized and the thermal conductivity can be easily reduced to a required level, so that high definition and high sensitivity can be achieved at the same time.

In the above embodiment, the positive photosensitive polyimide is used as the polyimide. However, the same effect as in the above embodiment can be obtained by using a negative photosensitive polyimide or a non-photosensitive polyimide. .

FIGS. 3A and 3B and FIG.
(A)-(c) are the perspective view and top view which show the thermal-type infrared sensor of the 2nd Embodiment of this invention, respectively, and the process sectional drawing for every step. The thermal infrared sensor according to the present embodiment is different from the thermal infrared sensor according to the previous embodiment in that the striped metal electrode 5 in the thermal infrared sensor according to the previous embodiment extends in the surface of the light receiving portion and unfolds into a bolometer. Is different from the embodiment. The manufacturing process is performed in exactly the same manner up to the process of forming the second through hole 18 up to FIG.

Thereafter, as shown in FIG. 4 (a), titanium having a thickness of 100 nm as a bolometer material is formed by a sputtering method, and this titanium is formed by a photoresist method and a selective etching method. ), Width 1
A titanium bolometer 25 is formed by patterning in a zigzag shape of up to 2 μm. Next, a fifth insulating film 21 of a silicon nitride film or a silicon oxide film is formed to a thickness of about 1 μm, and titanium nitride or the like having a thickness of about 15 nm serving as an infrared absorbing film is deposited by sputtering. The deposited film is processed into a rectangular pattern (with a pixel size pitch) covering the bolometer by using a photoresist method and a selective etching method to form the infrared absorbing film 22.

Next, using a photoresist method and a selective dry etching method, the fifth insulating film 21 and the fourth insulating film 17 between the two infrared absorbing films 22 constituting the mutually adjacent pixels are processed, By forming the slit-like opening 23 having a width of about 1 μm, the second polyimide sacrificial layer 16 is formed.
Expose the surface. Finally, by the ashing process,
The second sacrifice layer 16 and the first sacrifice layer 11 are removed, and a cavity is formed between the light receiving unit 1, the support leg 2, and the substrate.

In this embodiment, the bolometer 25 is meandering in a serpentine shape in order to increase the resistance. However, the spacing between the serrated lines is as small as 0.6 μm. Occupy. For this reason, the bolometer 25 constitutes a cavity (resonator) that sufficiently reflects infrared rays in the vicinity of the 10 μm wavelength band and absorbs infrared rays between the infrared ray absorbing layer 22 and the titanium nitride infrared ray absorbing layer 22. A part can be formed. The leg metal 14 may be a metal having a low thermal conductivity other than titanium.

In the second embodiment, FIG.
As shown in (2), the two support legs 2 of each pixel are arranged in mirror symmetry (line symmetry), and the end portions of the support legs 2 on the light receiving unit 1 side are brought close to each other. However, the arrangement is not limited to this example. For example, they may be arranged asymmetrically as in the first embodiment.

Also, the example in which the wedge-shaped bolometer 25 is made of titanium of the same material as the leg metal has been described. However, the wedge-shaped portion may be formed of a material different from that of the leg metal.

FIG. 5A is a plan view of a thermal infrared sensor according to the third embodiment of the present invention. In this embodiment,
The shape of the support leg 2 differs from the shape of the support leg of the second embodiment in that the shape of the support leg 2 is not linear but bent in a plane parallel to the substrate surface. Even if such a configuration is adopted, the leg portion 2 is extended substantially linearly on average, and substantially the same effect as in the second embodiment can be obtained.

FIG. 5B shows a thermal infrared sensor according to a fourth embodiment of the present invention. The second embodiment is different from the first embodiment in that the support legs 2 are disposed only directly below the corresponding light receiving units and have a bend not in a straight line but in a plane parallel to the substrate surface. With this configuration, the light receiving section 2 has a sufficient length to realize the required heat separation while the support legs 2 are arranged compactly.
Almost the same effects as those of the embodiment can be obtained.

The support leg 2 according to the fourth embodiment includes a component in a direction perpendicular to the extension direction of the support leg 2 as in the third embodiment. In this case, the longer the length of the support leg in the vertical direction is, the smaller the horizontal holding force of the light receiving unit is. Therefore, the number of depressed pixels of the light receiving unit may be increased.
Therefore, it is preferable that the component in the direction perpendicular to the extension direction of the support leg 2 be as short as possible.

FIG. 5C shows a thermal infrared sensor according to a fifth embodiment of the present invention. In the present embodiment, a pair of support legs 2 and 2 ′ extending from one light receiving unit 1 extend in opposite directions, and one support leg 2 of each pixel is connected to a common wiring 26 such as a ground line. Have been. In this arrangement,
The bases of the two support legs do not fit within one pixel,
The light receiving section 1 is supported in the form of a spread base by the support legs 2 and 2 ′ extending in opposite directions, and can be held in a symmetrical form. Therefore, the light receiving unit 1 is more stably held.

In the above embodiment, the example in which the common wiring 26 is a ground line has been described. However, it is also possible to connect the support leg on one side of each pixel by a common output line. Further, the configuration of the above-described embodiment can be applied commonly to the first, third, and fourth embodiments in which the thermoelectric material is made of a material different from the electrode.

In a conventional pixel having a size of 50 μm square, the resolution performance of the light receiving portion is about 0.1 C, and practically sufficient resolution performance was obtained for the required contrast of 0.2 ° C. However, when the pixel size is reduced to a size of 37 μm square, the area is halved and the length of the support leg is reduced to 74% as compared with the conventional light receiving unit of 50 μm square size. / 3. By employing the thermal infrared sensor of the present invention and making the supporting legs sufficiently long, the required decomposition performance can be obtained. As described above, the infrared sensor of the present invention is particularly effective for pixels having a size of 50 μm or less.

As described above, the present invention has been described based on the preferred embodiment. However, the thermal infrared sensor of the present invention is not limited to the configuration of the above-described embodiment, and is not limited thereto. Various modifications and changes from the configuration are also included in the scope of the present invention.

[0051]

As described above, in the thermal infrared sensor of the present invention, by improving the structure of the supporting leg, the fill factor of the light receiving portion can be increased and the thermal conductivity of the supporting leg can be set to a required level. Because it can be kept low,
There is an effect that a highly sensitive and high-definition infrared sensor can be obtained.

[Brief description of the drawings]

FIG. 1A is a schematic perspective view of a thermal infrared sensor according to a first embodiment of the present invention, and FIG. 1B is a plan view thereof.

FIGS. 2A to 2D are cross-sectional views of the infrared sensor of FIG.

FIG. 3A is a schematic perspective view of a thermal infrared sensor according to a second embodiment of the present invention, and FIG. 3B is a plan view thereof.

4 (a) to 4 (c) are cross-sectional views of the infrared sensor of FIG. 4 in each process step.

FIGS. 5A to 5C are plan views of thermal infrared sensors according to third to fifth embodiments of the present invention, respectively.

FIG. 6 is a schematic perspective view of a conventional thermal infrared sensor.

[Explanation of symbols]

 1: light receiving portion 1 ': light receiving portion of adjacent pixel 2: supporting leg 2': supporting leg of adjacent pixel 3: scanning circuit portion 4: thermoelectric material 5: metal electrode 6: contact 7: semiconductor substrate 8: scanning circuit 9: Wiring 10: Interlayer insulating film 11: First sacrifice layer 12: Second insulating film 13: First through hole 14: 14 'leg metal A. Support leg direction B. Arrangement direction of pixels in the X direction 15: Third insulating film 16: Second sacrificial layer 17: Fourth insulating film 18: Second through hole 19: Vanadium oxide 20: Silicon oxide film 19A: Bolometer 21: Fifth insulating film 22 : Infrared absorbing film 23: Slit opening 24: Cavity 25: Titanium bolometer 26: Common wiring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G065 AA04 AB02 BA12 BA32 BA34 CA13 4M118 AA01 AA10 AB10 BA05 CA14 CA19 CA35 CB05 GA10

Claims (9)

[Claims] 1. A plurality of light receiving portions which are arranged in an array at a predetermined pitch and are spaced apart from each other, each of which has a plurality of light receiving portions which receive infrared rays and rise in temperature, and which are supported separately from the substrate. A thermal infrared sensor, wherein support legs for supporting each of the light receiving portions are disposed between the light receiving portion and the substrate, and extend in a direction substantially parallel to the substrate surface. Sensor. 2. The method according to claim 1, wherein the wiring embedded in the supporting leg is electrically connected to an electrode of a thermoelectric material of the light receiving unit via a contact located in the corresponding light receiving unit. 2. The thermal infrared sensor according to 1. 3. The thermal infrared sensor according to claim 2, wherein the electrode made of the thermoelectric material is configured as a part of a bolometer that extends almost entirely in the light receiving section. 4. The support leg extends linearly and substantially in parallel with the support leg of an adjacent light receiving unit adjacent to the corresponding light receiving unit, and has a length exceeding the predetermined pitch. The thermal infrared sensor according to claim 1, wherein: 5. The device according to claim 1, wherein the support leg is disposed immediately below a corresponding light receiving unit, and is bent in a plane parallel to a substrate surface. Infrared sensor. 6. A pair of support legs are provided corresponding to each of said light receiving portions, and said pair of support legs extend in opposite directions from the corresponding light receiving portion. Item 1
3. The infrared sensor according to any one of 3. 7. A pair of support legs are disposed symmetrically with respect to each of said light receiving portions, and each of said pair of support legs has a length equal to or greater than said predetermined pitch. The thermal infrared sensor according to claim 1. 8. The thermal infrared sensor according to claim 1, wherein the pixel size is about 50 μm or less. 9. The thermal infrared sensor according to claim 8, wherein the light receiving section has a size substantially equal to a pixel size.