JP4720599B2 - Infrared sensor - Google Patents

Description

  The present invention relates to an infrared sensor.

  Conventionally, as a thermal infrared sensor, a temperature detection unit is arranged away from one surface of a base substrate, and the temperature detection unit is attached to the base substrate via a heat insulating unit that thermally insulates the temperature detection unit and the base substrate. A supported infrared sensor has been proposed (see, for example, Patent Document 1).

  In the infrared sensor disclosed in Patent Document 1, the heat insulating portion is disposed apart from the one surface of the base substrate, and the temperature detecting portion is stacked on the side opposite to the base substrate side. It consists of two legs extended from the side edge, a gap is formed between the support part and the one surface of the base substrate, and metal wiring connected to the temperature detection part is attached to each leg part. Are formed along. Here, in the infrared sensor disclosed in Patent Document 1, the heat insulating portion is formed by patterning a laminated film of a silicon oxide film and a silicon nitride film. Moreover, in the infrared sensor disclosed in Patent Document 1, an infrared absorption layer that absorbs infrared rays is stacked on the temperature detection unit.

In Patent Document 1, an infrared sensor (infrared image) in which sensor units each including an infrared absorption layer and a temperature detection unit are arranged in a two-dimensional array (matrix shape) and each sensor unit constitutes a pixel. Sensor) is also disclosed.
JP 2000-97765 A

  By the way, in the infrared sensor disclosed in the above-mentioned Patent Document 1, improvement in performance such as sensitivity and response speed is expected, and in order to increase sensitivity by increasing the temperature change of the temperature detection unit due to infrared absorption. Increase the infrared absorption efficiency by increasing the overall length of each leg in the heat insulating part to reduce the thermal conductance of each leg (increasing the thermal resistance) and increasing the thickness of the infrared absorbing layer. It is possible.

  However, in the infrared sensor disclosed in Patent Document 1, if the total length of each leg is increased without changing the size of the temperature detection unit, the size of the entire sensor becomes large. When the thickness dimension of the infrared absorption layer is increased, the heat capacity of the infrared absorption layer is increased and the response speed is lowered. In addition, in the infrared sensor disclosed in Patent Document 1, the leg portion may be damaged due to an external force that causes the support portion to vibrate.

  The present invention has been made in view of the above-mentioned reasons, and the purpose thereof is to prevent the leg portion from being damaged due to an external force that causes the heat insulating portion to vibrate, and to improve the performance. It is to provide an infrared sensor that can be realized.

According to the first aspect of the present invention, there is provided a base substrate, a temperature detection unit that absorbs infrared rays and detects a temperature change due to the absorption, and a temperature detection unit such that the temperature detection unit is disposed away from one surface of the base substrate. And a heat insulating part that thermally insulates the temperature detecting part and the base substrate, the heat insulating part being spaced apart from the one surface of the base substrate and provided with a temperature detecting part, and a supporting part And a leg portion connecting the base substrate, the leg portion is a support post portion standing on the one surface side of the base substrate, and a beam portion connecting the upper end portion of the support post portion and the support portion. with the door, in a plane beam portion is orthogonal to the width direction along the one surface of the base substrate, the shape of the meandering of the corrugated plate shape distance changes periodically between the one surface of the base substrate It is formed in these.

  According to the present invention, the leg portion can be prevented from being damaged due to an external force that vibrates the heat insulating portion, the reliability is improved, and the leg portion is formed linearly. In comparison, the overall length of the leg can be increased, the thermal conductance can be reduced, and high sensitivity can be achieved.

Further, according to this invention, without increasing the area occupied by the legs that put in a plane parallel to the one surface of the base over the scan board, it is possible to lengthen the overall length of the leg.

According to a second aspect of the present invention, in the first aspect of the present invention, at least one of the leg portion and the support portion is formed of a porous material.

  According to this invention, compared with the case where the said leg part and the said support part are formed with a non-porous material, the heat capacity of the said heat insulation part can be reduced and the response speed can be further increased.

According to a third aspect of the invention, in the second aspect of the invention, the porous material is a material selected from the group consisting of porous silicon oxide, porous silicon oxide organic polymer, and porous silicon oxide inorganic polymer. It is characterized by being.

  According to this invention, in the formation of the portion formed of the porous material in the heat insulating portion, it is possible to employ a process in which a sol-gel solution is spin-coated on the one surface side of the base substrate and then dried. It is possible to easily form the heat insulating portion.

  The invention of claim 1 can prevent the leg portion from being damaged due to an external force that vibrates the heat insulating portion, and has an effect of improving performance.

  Hereinafter, the infrared sensor of the present embodiment will be described with reference to FIG.

  The infrared sensor of this embodiment absorbs infrared rays, and a rectangular plate-like base substrate 1 composed of a silicon substrate 1a and an insulating film 1b made of a silicon oxide film formed on one surface side of the silicon substrate 1a. In addition, the temperature detection unit 3 that detects a temperature change due to the absorption and the temperature detection unit 3 are supported so that the temperature detection unit 3 is spaced apart from one surface of the base substrate 1 (upper surface in FIG. 1B). And a heat insulating part 4 for thermally insulating the temperature detecting part 3 and the base substrate 1. Here, the heat insulating portion 4 is arranged so as to be separated from the one surface of the base substrate 1 and the temperature detecting portion 3 is formed on the side opposite to the base substrate 1 side, and the support portion 41 and the base substrate 1. And two leg portions 42, 42 connected to each other.

  The temperature detection unit 3 is a bolometer-type sensing element whose electric resistance value changes according to temperature, and includes a sensor layer including a titanium film on the support unit 41 side and a titanium nitride film on the titanium film. . Here, the titanium nitride film is provided as an antioxidant film for the titanium film. Note that the material of the sensor layer is not limited to titanium, and for example, amorphous silicon, vanadium oxide, or the like may be employed. The temperature detector 3 is not limited to a sensing element whose electric resistance value changes according to temperature, but includes a sensing element whose dielectric constant changes according to temperature, a thermopile type sensing element, a pyroelectric type sensing element, and the like. Any of the sensing elements may be employed, and can be formed using a general thin film forming technique by appropriately selecting the material. Here, for example, PZT, BST, or the like may be employed as the material of the sensing element whose dielectric constant varies with temperature.

  The temperature detection unit 3 is formed in a meandering shape (here, a zigzag shape), and both ends extend along the leg portions 42 and 42 of the heat insulating unit 4. Are electrically connected to the conductor patterns 10 and 10 made of a metal film (for example, an Al—Si film) on the one surface of the base substrate 1. Here, in the present embodiment, the same material as that of the sensor layer constituting the temperature detection unit 3 is adopted as the material of the wires 8 and 8 (here, a laminated film of a titanium film and a titanium nitride film), and the wires 8, 8 and the temperature detector 3 are formed simultaneously. In the present embodiment, Al—Si is adopted as the material of each conductor pattern 10, 10, and a part of each conductor pattern 10, 10 constitutes a pad. Therefore, temperature detection is performed through a pair of pads. The output of the unit 3 can be taken out to the outside.

  Moreover, in the infrared sensor of this embodiment, the infrared reflective film 6 that reflects the infrared light transmitted through the temperature detection unit 3 and the support unit 41 toward the temperature detection unit 3 is provided on the one surface of the base substrate 1. . Here, the infrared sensor of the present embodiment assumes infrared of a wavelength band of 8 μm to 13 μm radiated from the human body as the detection target infrared, and uses Al—Si as the material of the infrared reflecting film 6. ing.

  The leg portions 42 in the above-described heat insulating portion 4 include two cylindrical support post portions 42 a and 42 a erected on the conductor patterns 10 and 10 on the one surface side of the base substrate 1, and each support post portion. 42a and 42a are composed of beam portions 42b and 42b that connect the support portion 41 with the upper ends thereof, and a gap 7 is formed between the support portion 41 and the base substrate 1. Here, the outer peripheral shape of the support part 41 is a rectangular shape, and each beam part 42b, 42b is extended from the one end part of the longitudinal direction of the one side edge of the support part 41 in the direction orthogonal to the said one side edge. It is formed in a planar shape that extends along the direction from the one end to the other end of the one side edge, and has rotational symmetry with respect to the central axis along the thickness direction of the support portion 41. Has been placed. In addition, the line width of the part formed on the beam portions 42b and 42b of the leg portions 42 and 42 in the wirings 8 and 8 is the beam portion 42b in order to suppress heat transfer through the wires 8 and 8. , 42b is set to be sufficiently smaller than the width dimension. Moreover, the site | part currently formed in support post part 42a, 42a among wiring 8 and 8 is formed ranging over the whole inner peripheral surface of support post part 42a, 42a, and the surface of conductor pattern 10,10. The support post portions 42 a and 42 a are reinforced by the wires 8 and 8.

By the way, in the infrared sensor of this embodiment, the beam parts 42b and 42b in the leg parts 42 and 42 of the heat insulation part 4 are formed in a meandering shape in a plane perpendicular to the width direction along the one surface of the base substrate 1. (In this embodiment, the beam portions 42b and 42b are formed in a corrugated plate shape). Here, the distance between the beam portions 42b and 42b and the one surface of the base substrate 1 is periodically changed, and a portion having a relatively long distance from the base substrate 1 (hereinafter referred to as an upper stage portion). ) 42b ₁ , 42b ₁ and the base substrate 1 a relatively short portion (hereinafter referred to as the lower step portion) 42b ₂ , 42b ₂ is formed integrally with the upper step portion 42b ₁ , 42b ₁ 42 b ₃ , 42 b ₃ and lower step portions 42 b ₂ , 42 b ₂ are connected via etching stopper layers 43, 43 described later stacked on top of each other. In addition, each leg part 42 and 42 is the shape which the whole including the beam parts 42b and 42b and the support post parts 42a and 42a meandered in the surface orthogonal to the width direction along the said one surface of the base substrate 1. Is formed.

  Further, in the infrared sensor of this embodiment, most of the leg portions 42 and 42 of the heat insulating portion 4 (specifically, portions excluding the etching stopper layers 43 and 43) and the support portion 41 are formed of a porous material. ing. Here, porous silica, which is a kind of porous silicon oxide, is employed as the porous material of the legs 42, 42 of the heat insulating part 4 and the support part 41, but a kind of porous silicon oxide-based organic polymer. Methyl-containing polysiloxane, Si-H-containing polysiloxane which is a kind of porous silicon oxide-based inorganic polymer, silica aerogel, etc. may be employed. As the porous material, porous silicon oxide, If a material selected from the group consisting of a silicon oxide organic polymer and a porous silicon oxide inorganic polymer is employed, a sol-gel solution is spin-coated on the one surface side of the base substrate 1 in forming the heat insulating portion 4. Therefore, a drying process can be adopted, and the heat insulating portion 4 can be easily formed.

  Here, most of the legs 42, 42 in the present embodiment are composed of a porous silica film (porous silicon oxide film) having a porosity of 60%. However, if the porosity is too small, a sufficient heat insulating effect is achieved. However, if the porosity is too high, the mechanical strength becomes weak and the formation of the structure becomes difficult. Therefore, the porosity of the porous silica film may be appropriately set within a range of, for example, about 40% to 80%.

Here, the total thermal conductance G of the two beam portions 42b and 42b indicates that the thermal conductivity of the material of the beam portion 42b is α [W / (m · K)], and the beam portion 42b is formed linearly. If the length is L [μm] and the cross-sectional area of the beam portion 42b is S, G = 2 × α × (S / L), but if the material of the beam portion 42b is SiO ₂ If α = 1.4 [W / (m · K)], L = 50 [μm], S = 10 [μm ² ], the thermal conductance G is
G = 2 × α × (S / L) = 560 × 10 ⁻⁹ [W / K].

On the other hand, when the beam portion 42b is composed of a porous silica film having a porosity of 60% and the beam portion 42b has a meandering shape, the beam portion 42b is twice as long as the linear shape. If α = 0.05 [W / (m · K)], L = 100 [μm], S = 10 [μm ² ], the total thermal conductance G of the two beam portions 42b and 42b is
G = 2 × α × (S / L) = 1.0 × 10 ⁻⁸ [W / K]
Thus, the thermal conductance G can be set to a value smaller than 1/50 of the thermal conductance G of the comparative example in which the beam portion 42b is made of a silicon oxide film, and the heat transfer through the leg portions 42 and 42 can be further improved. It can be suppressed and high sensitivity can be achieved.

Further, the heat capacity C of the support portion 41 is such that the volume specific heat of the support portion 41 is c _v , the area of the support portion 41 (area of the cross section perpendicular to the thickness direction) is A [μm ² ], and the thickness of the support portion 41 is d. If [μm], C = c _v × A × d. Here, if the material of the support portion 41 is SiO ₂ , c _v = 1.8 × 10 ⁶ [J / (m ³ · K)], A = 2500 [μm ² ], d = 0. If 5 [μm], the heat capacity C of the support portion 41 is
C = c _v × A × d = 22.6 × 10 ⁻¹⁰ [J / K].

On the other hand, when the support portion 41 is composed of a porous silica film having a porosity of 60% as in this embodiment, c _v = 0.88 × 10 ⁶ [J / (m ³ · K)], A = 2500 [μm ² ], d = 0.5 [μm], the heat capacity C of the support portion 41 is
C = c _v × A × d = 11.0 × 10 ⁻¹⁰ [J / K]
Thus, the heat capacity C of the support portion 41 can be set to a value smaller than half that of the comparative example in which the support portion 41 is made of a silicon oxide film, and the time constant is reduced to increase the response speed. I can plan.

  Hereinafter, the manufacturing method of the infrared sensor of this embodiment is demonstrated, referring FIGS. 2 to 4, similarly to FIG. 1B, a cross section of a part corresponding to the A-A ′ cross section of FIG.

  First, an insulating film 1b made of a silicon oxide film is formed on one surface side of a single crystal silicon substrate (wafer until dicing described later) 1a as a basis of the base substrate 1 by, for example, a thermal oxidation method. The structure shown in 2 (a) is obtained.

  Thereafter, a metal film made of the material of the conductor patterns 10 and 10 and the infrared reflection film 6 (for example, on the entire surface of one surface side (the upper surface side in FIG. 2A) of the base substrate 1 made of the silicon substrate 1a and the insulating film 1b (for example, , Al-Si film, etc.) are formed by sputtering or the like, and then the metal film is patterned by using a photolithography technique and an etching technique, thereby forming conductor patterns 10, 10 each consisting of a part of the metal film, and By forming the infrared reflective film 6, the structure shown in FIG. 2B is obtained.

Next, a resist is spin-coated on the entire surface of the one surface side of the base substrate 1 to form a first sacrificial layer 21 made of a resist layer, and then the lower stage of the beam portion 42b on the first sacrificial layer 21. which is the material of the part 42b ₂ porous material (e.g., porous silica, silica airgel, etc.) by forming a first porous film 40a made of, the structure shown in Figure 2 (c). Here, in forming the first porous film 40a, when the porous material is porous silica, a process in which a sol-gel solution is spin-coated on the one surface side of the base substrate 1 and then dried by heat treatment. When the porous material is silica aerogel, the sol-gel solution is spin-coated on the one surface side of the base substrate 1 and then dried by supercritical drying. It can be easily formed by adopting a process.

After forming the first porous membrane 40a, by forming the lower step portion 42b ₂ of the beam portion 42b by patterning the first porous film 40a by using photolithography and etching, Fig. 2 The structure shown in (d) is obtained.

Thereafter, a stopper material film (for example, an Al—Si film) serving as a basis of the above-described etching stopper layer 43 is formed on the entire surface of the one surface side of the base substrate 1 by a sputtering method or the like. by forming the etching stopper layer 43 made of a part of the stopper material film on each respective lower portions 42b ₂ by patterning the stopper material film by using the etching technique, shown in FIG. 3 (a) Get the structure.

  Subsequently, a second sacrificial layer 22 made of a resist layer is formed by rotating a resist on the entire surface of the one surface side of the base substrate 1, and then the second sacrificial layer 22 and the first sacrificial layer are formed. 21 are formed to form circular opening portions 23 and 23 that expose portions of the conductor patterns 10 and 10 by etching the portions of the support post portions 42a and 42a corresponding to the respective formation scheduled regions. At the same time, a portion corresponding to the etching stopper layer 43 in the second sacrificial layer 22 is etched to form an opening 24 that exposes the surface of the etching stopper layer 43, thereby forming the structure shown in FIG. obtain.

Subsequently, a second porous film made of a porous material (for example, porous silica, silica airgel, etc.) that is a material of the heat insulating portion 4 is formed on the entire surface of the base substrate 1 on the one surface side. the remaining portion of the heat insulating portion 4 by patterning the second porous layer using a lithography technique and an etching technique (supporting portion 41, the upper portion 42b _1, the connecting portions 42b _3, each support post portions 42a) Is formed to obtain the structure shown in FIG. Here, in forming the second porous film, when the porous material is porous silica, a process of spin-coating the sol-gel solution on the one surface side of the base substrate 1 and then drying by heat treatment is performed. In the case where the porous material is silica aerogel, the sol-gel solution is spin-coated on the one surface side of the base substrate 1 and then dried by supercritical drying. Can be easily formed.

  After the formation of the heat insulating portion 4, a sensor material composed of a laminated film of a titanium layer and a titanium nitride film serving as a basis for the sensor layer and the wirings 8 and 8 on the entire surface of the base substrate 1 on the one surface side. By forming the layer 30 by sputtering or the like, the structure shown in FIG.

  Next, by patterning the sensor material layer 30 using a photolithography technique and an etching technique, the temperature detection part 3 and the wirings 8 and 8 each consisting of a part of the sensor material layer 30 are formed, whereby FIG. The structure shown in a) is obtained.

  Subsequently, the sacrificial layers 21 and 22 on the one surface side of the base substrate 1 are selectively removed by etching to obtain an infrared sensor having a structure shown in FIG. What is necessary is just to divide into the infrared sensor.

  In the infrared sensor of the present embodiment described above, the leg portions 42 and 42 connecting the support portion 41 and the base substrate 1 are formed in a meandering shape, so that the heat insulating portion 4 vibrates. When the leg portions 42 and 42 are prevented from being damaged due to an external force, the reliability is improved, and the beam portions 42b and 42b of the leg portions 42 and 42 are linearly formed. In comparison, the overall length of the legs 42, 42 can be increased, the thermal conductance can be reduced, and high sensitivity can be achieved. Further, each leg portion 42, 42 is formed in a shape in which each beam portion 42 b, 42 b meanders in a plane orthogonal to the width direction along the one surface of the base substrate 1. The total length of the legs 42, 42 can be increased without increasing the area occupied by the legs 42, 42 in a plane parallel to the one surface. In the present embodiment, the entire leg portion 42 including the beam portion 42b and the support post portion 42a is formed in a meandering shape, but at least a part of the leg portion 42b is formed in a meandering shape. It only has to be.

Further, in the infrared sensor of the present embodiment, since the support portion 41 is formed by a porous material, as compared with the case where the support portion 41 is formed by a non-porous material such as SiO ₂ or Si ₃ N ₄ The heat capacity of the support portion 41 can be reduced, and the response speed can be further increased. Furthermore, in the infrared sensor of this embodiment, since most of the leg portions 42 in the heat insulating portion 4 are also formed of a porous material, the leg portions 42 are formed of a non-porous material such as SiO ₂ or Si ₃ N _4. Compared to the conventional case, the thermal conductance of the leg part 42 can be reduced to increase the sensitivity, and the heat capacity of the leg part 42 can be reduced to increase the response speed. .

  Moreover, in the infrared sensor of this embodiment, the infrared reflective film 6 that reflects the infrared light transmitted through the temperature detection unit 3 and the support unit 41 toward the temperature detection unit 3 is provided on the one surface side of the base substrate 1. Therefore, the infrared absorption efficiency in the temperature detection unit 3 can be increased, and the temperature detection unit 3 can be highly sensitive.

  The infrared sensor described in the above embodiment is an infrared detection element provided with only one temperature detection unit 3. However, the temperature detection unit 3 is arranged in a two-dimensional array (matrix shape), and each temperature detection unit is arranged. May be an infrared image sensor that constitutes a pixel. In the infrared sensor described in the above embodiment, the temperature detection unit 3 is provided on the side of the support unit 41 opposite to the base substrate 1 side. However, the temperature detection unit 3 is provided on the base substrate 1 side of the support unit 41. It may be provided.

1A is a schematic perspective view, and FIG. 2B is a schematic cross-sectional view taken along line A-A ′ of FIG. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. It is principal process sectional drawing for demonstrating the manufacturing method same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base substrate 1a Silicon substrate 1b Insulating film 3 Temperature detection part 4 Heat insulation part 6 Infrared reflective film 7 Gap 8 Wiring 10 Conductive pattern 41 Support part 42 Leg part

Claims (3)

A temperature detection unit that supports the temperature detection unit so that the temperature detection unit is disposed away from one surface of the base substrate, and a temperature detection unit that absorbs infrared rays and detects a temperature change due to the absorption. And a heat insulating part that thermally insulates the base substrate, and the heat insulating part is arranged to be spaced apart from the one surface of the base substrate and the temperature detecting part is provided, and the support part and the base substrate are connected to each other. A leg portion, and the leg portion includes a support post portion erected on the one surface side of the base substrate, and a beam portion connecting the upper end portion of the support post portion and the support portion. in a plane perpendicular to the width direction along the one surface of the base substrate, to become formed into a shape distance is meandering of the corrugated plate shape that varies periodically between the one surface of the base substrate A featured infrared sensor. At least one of an infrared sensor mounting serial to claim 1, characterized by being made form a porous material of the support portion and the leg portion. The porous material is silicon oxide porous, No placing serial to claim 2, wherein the silicon oxide-based organic polymer porous, from the group of silicon oxide-based inorganic polymer porous a material selected Infrared sensor .

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