JP2010249779A - Infrared sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared sensor capable of improving not only reliability but also sensitivity. <P>SOLUTION: A thin film structure part 3a including an infrared absorption part 33 is supported by the periphery part of a trench part 11 in a base substrate 1. A passivation film 60 is formed on the uppermost surface layer side of the thin film structure part 3a and the base substrate 1. The infrared sensor includes: a first soaking layer 71 having resistance to an etchant used in the formation of the trench part 11, formed on the passivation film 60 in a form covering an area in which a plurality of hot contacts T1 of a thermopile 30a are concentrated in a plan view, and made of a heat conductive material having heat conductivity higher than that of the passivation film 60; and a second soaking layer 72 having resistance to the etchant, formed on the passivation film 60 in a form covering an area in which a plurality of cold contacts T2 of the thermopile 30a are concentrated, and made of the heat conductive material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an infrared sensor.

  Conventionally, an infrared sensor formed using a micromachining technique or the like has been researched and developed in various places (for example, see Patent Document 1).

  As shown in FIG. 26, the infrared sensor disclosed in Patent Document 1 includes an infrared absorbing portion 33 ′ made of gold black or the like and a thermopile 30a ′ that detects a temperature change of the infrared absorbing portion 33 ′. Provided on one surface side of the base substrate 1 formed using, and the base substrate 1 ′ is formed with a digging portion 11 ′ for thermally insulating the infrared absorbing portion 33 ′ from the base substrate 1 ′, The thin film structure portion 3a ′ having the infrared absorbing portion 33 ′ located on the inner side of the digging portion 11 ′ in a plan view on the one surface side of the base substrate 1 ′ is formed around the digging portion 11 ′ in the base substrate 1 ′. It is supported.

  Here, in the thermopile 30a ′, a plurality of polysilicon elements 134 ′ are formed across the thin film structure portion 3a ′ and the base substrate 1 ′, and one end portion of each polysilicon element 134 ′ is formed in the thin film structure portion 3a ′. A plurality of hot junctions T1 are formed by connecting a connecting metal portion (conductor) 136 ′ made of Al or the like to each of the polysilicon elements 134 ′ in the peripheral portion of the digging portion 11 ′ in the base substrate 1 ′. A plurality of cold junctions T2 are formed by connecting the connecting metal portion 136 ′ to the other end portion.

  Here, the infrared sensor having the configuration shown in FIG. 26 has a silicon oxide film 31 ′, a silicon nitride film 32 ′ on the silicon oxide film 31 ′, and the silicon nitride film 32 ′ on one surface side of the silicon substrate 1a ′. A thermal insulation layer 33 ′ composed of the upper silicon oxide film 131 ′ is formed, and each of the polysilicon elements 134 ′ is formed on the thermal insulation layer 33 ′, and the thermal insulation layer 33 ′ and each polysilicon are formed. An interlayer insulating film 50 ′ made of a laminated film of a silicon oxide film 151 ′ and a BPSG film 152 ′ is formed so as to cover the element 134 ′, and the above-described conductor portion 136 ′ is formed on the interlayer insulating film 50 ′. Each polysilicon element 134 'is connected through a contact hole.

  By the way, in the above-mentioned Patent Document 1, as a method for manufacturing the above-described infrared sensor, in forming the digging portion 11 ′, as shown in FIG. 27, an alkaline system which is an etchant used when forming the digging portion 11 ′ is used. A protective film 75 ′ having a two-layer structure made of a resin resistant to a solution (for example, potassium hydroxide, sodium hydroxide, etc.) is replaced with a silicon oxide film 61 ′ and a silicon nitride film 62 ′ on the outermost layer side of the thin film structure portion 3a ′. Are formed so as to cover the passivation film 60 ′ and the infrared absorbing portion 33 ′, and the portion corresponding to the digging portion 11 ′ in the silicon substrate 1 a ′ is anisotropically etched by the etchant. A manufacturing method is described in which the protective film 75 ′ is removed after the formation of the digging portion 11 ′.

  According to the manufacturing method of the infrared sensor of the above-mentioned patent document 1, after forming the protective film 75 ′ covering the passivation film 60 ′ and the infrared absorbing part 33 ′ on the outermost layer side of the thin film structure part 3 a ′, the dug part 11 is formed. For example, due to a step at the hot junction T1 or the cold junction T2, the cracks or pins running in the depth direction from the surface of the passivation film 60 ′ are formed on the passivation film 60 ′ and the interlayer insulating film 50 ′. Even if holes or the like are formed, it is possible to prevent the thermopile 30a ′ from being eroded by the etchant when forming the digging portion 11 ′ in the base substrate 1 ′. Here, the silicon nitride film 32 ′ of the thermal insulating layer 33 ′ described above prevents the etchant from entering from the back side of the thin film structure portion 3a ′ and reaching the thermopile 30a ′ when the digging portion 11 ′ is formed. It also has a function.

  In the infrared sensor having the configuration shown in FIG. 26, only one thermopile 30a ′ is provided on the one surface side of the base substrate 1 ′. However, the pixel portion including the thermopile 30a ′ is arranged in a two-dimensional array. And a structure in which each pixel unit arranged in a two-dimensional array includes a thermopile 30a ′ and a MOS transistor which is a pixel selection switching element for reading out the output of the thermopile 30a ′. Proposed.

Japanese Patent Laid-Open No. 2003-302285

  By the way, according to the manufacturing method of the infrared sensor disclosed in Patent Document 1, it is possible to prevent the thermopile 30a ′ from being eroded by the etchant used when forming the digging portion 11 ′. Improvements can be made and reliability can be improved.

  However, even higher sensitivity is desired for an infrared sensor manufactured by such a manufacturing method. In the infrared sensor having the configuration shown in FIG. 26, it is conceivable to reduce the heat capacity of the thin film structure portion 3a ′ by reducing the thickness dimension of the thin film structure portion 3a ′, thereby increasing the response speed. When the film thickness of the interlayer insulating film 50 ′ and the passivation film 60 ′ is reduced, the sensitivity is lowered, cracks and pinholes are easily generated in the passivation film 60 ′ and the interlayer insulating film 50 ′, and the thin film structure portion is formed. 3a ′ is likely to be warped, and there is a risk that the sensitivity is lowered due to the warp, and the reliability and manufacturing yield are lowered.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide an infrared sensor capable of improving not only reliability but also sensitivity.

  According to the first aspect of the present invention, an infrared absorption portion and a thermopile for detecting a temperature change of the infrared absorption portion are provided on one surface side of a base substrate formed using a silicon substrate, and the infrared absorption portion is provided on the base substrate. A digging portion for thermal insulation from the substrate is formed, and the thin film structure portion having the infrared absorbing portion located inside the digging portion in a plan view on the one surface side of the base substrate is a digging portion of the base substrate. An infrared sensor that is supported by a peripheral part and has a passivation film formed on the outermost layer side of the thin film structure part and the base substrate. The thermopile is a thin film of two polysilicon elements of different conductivity types. The structure portion has a plurality of hot junctions formed by joining with the first connecting metal portion, and two polysilicon conductors of different conductivity types. Having a plurality of cold junctions formed by joining the element to the periphery of the digging portion in the base substrate by the second connecting metal portion, and having resistance to an etchant used when forming the digging portion, and a flat surface A first soaking layer made of a thermally conductive material that is formed on the passivation film so as to cover a region where the plurality of hot contacts of the thermopile are provided in a concentrated manner in view, and has a higher thermal conductivity than the passivation film; A second soaking layer formed on the passivation film so as to cover a region where a plurality of cold junctions of the thermopile are concentrated and have resistance against the etchant. Features.

  According to the present invention, it is formed on the passivation film so as to cover a region having a resistance to the etchant used when forming the digging portion and a plurality of hot contacts of the thermopile are concentrated in a plan view. Passivation so as to cover a first soaking layer made of a heat conductive material having a higher thermal conductivity than the passivation film, and a region having a resistance to the etchant and where a plurality of cold junctions of the thermopile are concentrated. And a second soaking layer made of the thermally conductive material formed on the film, so that cracks and pinholes are formed in the passivation film due to steps at the hot and cold junctions. Even if cracks and pinholes are covered with the first soaking layer and the second soaking layer, the etchant used when forming the dug portion during manufacturing The thermopile can be further prevented from being eroded and the reliability can be improved. In addition, the temperature of the plurality of hot junctions can be made uniform by the first soaking layer during use, and the second soaking layer can be used. Thus, the temperature of the plurality of cold junctions can be made uniform, so that the sensitivity can be improved.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the material of each of the connecting metal portions and the thermally conductive material are the same.

  According to this invention, since the coefficient of thermal expansion of the material of each connection metal part and the thermally conductive material are equal, the stress generated in the thin film structure part due to the expansion and contraction of the thin film structure part accompanying a temperature change is generated. It can be mitigated.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the thermally conductive material is Al-Si.

  According to this invention, it is easy to process the first soaking layer and the second soaking layer.

  The invention of claim 1 has an effect that not only the reliability can be improved but also the sensitivity can be improved.

It is a plane layout figure of the principal part of the pixel part in the infrared sensor of an embodiment. It is a plane layout figure of the principal part of a pixel part in an infrared sensor same as the above. It is a plane layout figure of the pixel part in an infrared sensor same as the above. It is a plane layout figure of the pixel part in an infrared sensor same as the above. It is a plane layout figure of an infrared sensor same as the above. The principal part of the pixel part in an infrared sensor same as the above is shown, (a) is a planar layout view, (b) is a schematic sectional view corresponding to the D-D 'section of (a). The principal part of the pixel part in an infrared sensor same as the above is shown, (a) is a planar layout view, (b) is a schematic sectional view corresponding to the D-D 'section of (a). The principal part containing the cold junction in an infrared sensor same as the above is shown, (a) is a plane layout figure, (b) is a schematic sectional drawing. The principal part containing the hot junction in an infrared sensor same as the above is shown, (a) is a plane layout view, (b) is a schematic sectional view. It is a schematic sectional drawing of the principal part of the pixel part in an infrared sensor same as the above. It is a schematic sectional drawing of the principal part of the pixel part in an infrared sensor same as the above. It is principal part explanatory drawing of an infrared sensor same as the above. It is an equivalent circuit diagram of an infrared sensor same as the above. It is a schematic sectional drawing of the infrared module provided with the infrared sensor same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above. It is a schematic sectional drawing of the pixel part in the other structural example of an infrared sensor same as the above. It is a schematic sectional drawing of the pixel part in the other structural example of an infrared sensor same as the above. It is a schematic sectional drawing of the pixel part in the other structural example of an infrared sensor same as the above. It is a plane layout figure of a pixel part in other examples of composition of an infrared sensor same as the above. It is a plane layout figure of a pixel part in other examples of composition of an infrared sensor same as the above. It is a plane layout figure of a pixel part in other examples of composition of an infrared sensor same as the above. It is a principal part enlarged view of the plane layout figure of the pixel part of an infrared sensor same as the above. The infrared sensor of a prior art example is shown, (a) is a schematic plan view, (b) is a principal part plan view partly broken, (c) is a principal part schematic sectional drawing. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above.

(Embodiment 1)
Hereinafter, the infrared sensor A of the present embodiment will be described with reference to FIGS.

  The infrared sensor A of the present embodiment is an infrared array sensor, and a plurality of pixel units 2 (see FIG. 5) having a thermal infrared detection unit 3 and a MOS transistor 4 that is a pixel selection switching element include a base substrate 1. Are arranged in an array (here, a two-dimensional array) on one surface side. Here, the base substrate 1 is formed using a silicon substrate 1a. In the present embodiment, m × n (8 × 8 in the example shown in FIGS. 5 and 13) pixel units 2 are formed on the one surface side of one base substrate 1. The number and arrangement of 2 are not particularly limited. Further, in the present embodiment, the temperature sensing unit 30 of the thermal infrared detection unit 3 is configured by connecting a plurality (here, six) of thermopiles 30a (see FIG. 3) in series. The equivalent circuit of the temperature sensing unit 30 in the thermal infrared detection unit 3 is represented by a voltage source Vs corresponding to the thermoelectromotive force of the temperature sensing unit 30.

In addition, as shown in FIGS. 3, 6, and 13, the infrared sensor A of the present embodiment has one end of the temperature sensing unit 30 of each of the plurality of thermal infrared detection units 3 in each row via the MOS transistor 4 described above. A plurality of vertical readout lines 7 commonly connected to each column and a plurality of gate electrodes 46 of the MOS transistors 4 corresponding to the temperature sensing portions 30 of the thermal infrared detectors 3 of each row are commonly connected to each row. A horizontal signal line 6, a plurality of ground lines 8 in which the p ^{+ -type} well regions 41 of the MOS transistors 4 in each column are connected in common to each column, a common ground line 9 in which the ground lines 8 are connected in common, The other end of the temperature sensing unit 30 of the plurality of thermal infrared detectors 3 in each row is provided with a plurality of reference bias lines 5 commonly connected to each row, and all of the thermal infrared detectors 3 Reading the output of the temperature sensing unit 30 in time series And can be. In short, the infrared sensor A of the present embodiment is arranged in parallel with the thermal infrared detector 3 and the thermal infrared detector 3 on the one surface side of the base substrate 1 to read the output of the thermal infrared detector 3. A plurality of pixel portions 2 having the MOS transistors 4 are formed.

  Here, in the MOS transistor 4, the gate electrode 46 is connected to the horizontal signal line 6, the source electrode 48 is connected to the reference bias line 5 via the temperature sensing unit 30, and each reference bias line 5 is connected to the common reference bias line 5a. Are connected in common, the drain electrode 47 is connected to the vertical readout line 7, each horizontal signal line 6 is electrically connected to each pixel selection pad Vsel, and each vertical readout line 7 is individually connected to each other. Are electrically connected to the output pad Vout, the common ground line 9 is electrically connected to the ground pad Gnd, the common reference bias line 5a is electrically connected to the reference bias pad Vref, and the silicon substrate 1a is electrically connected. It is electrically connected to the substrate pad Vdd.

  Thus, the output voltage of each pixel 2 can be read sequentially by controlling the potential of each pixel selection pad Vsel so that the MOS transistors 4 are sequentially turned on. For example, if the potential of the reference bias pad Vref is 1.65, the potential of the ground pad Gnd is 0 V, the potential of the substrate pad Vdd is 5 V, and the potential of the pixel selection pad Vsel is 5 V, the MOS transistor 4 Is turned on, the output voltage of the pixel 2 (1.65 V + the output voltage of the temperature sensing unit 30) is read from the output pad Vout, and the MOS transistor 4 is turned off when the potential of the pixel selection pad Vsel is set to 0V. The output voltage of the pixel 2 is not read from the output pad Vout. In FIG. 5, the pixel selection pad Vsel, the reference bias pad Vref, the ground pad Gnd, the output pad Vout, etc. are all illustrated as pads 80 without being distinguished.

  Here, as shown in FIG. 14, the infrared sensor A, the signal processing IC chip B that performs signal processing of the output voltage that is the output signal of the infrared sensor A, and the infrared sensor A and the signal processing IC chip B are accommodated. In the case of configuring an infrared sensor module including the package C, a plurality of pads 80 of the infrared sensor A are electrically connected to the signal processing IC chip B through wirings 81 made of bonding wires. A pad (not shown), an amplifier circuit (not shown) for amplifying the output voltage of a pad (hereinafter referred to as an input pad) connected to the output pad Vout of the infrared sensor A among these pads, a plurality of pads An infrared image can be obtained by providing a multiplexer or the like that alternatively inputs the output voltage of the input pad to the amplifier circuit.

  The above-mentioned package C is formed in a rectangular box shape with one surface open, and a package main body 90 made of a multilayer ceramic substrate (ceramic package) on which the infrared sensor A and the signal processing IC chip B are mounted on the inner bottom surface side, and the infrared sensor A And a package lid 100 made of a metal lid, which is provided with a lens 110 for converging infrared rays and is covered on the one surface side of the package body 90, and an airtight space surrounded by the package body 90 and the package lid 100. It is a dry nitrogen atmosphere. Here, the peripheral portion of the package lid 100 is fixed to a rectangular frame-shaped metal pattern (not shown) formed on the one surface of the package body 90 by seam welding. The package body 90 is not limited to a multilayer ceramic substrate, and for example, a laminate of glass epoxy resin substrates may be used.

  Here, a shield conductor pattern 92 is formed on the inner surface of the package body 90, and the infrared sensor A and the signal processing IC chip are connected to the shield conductor pattern 92 of the package body 90 with a conductive bonding material (for example, Bonding is performed via bonding layers 95 and 95 made of solder, silver paste, or the like. In addition, the joining method of the infrared sensor A and the signal processing IC chip B and the package body 90 is not limited to a joining method using a conductive joining material such as solder or silver paste. A bonding method using -Sn eutectic or Au-Si eutectic may be employed. However, a bonding method capable of direct bonding such as a room temperature bonding method is more advantageous in improving the distance accuracy between the infrared sensor 5 and the lens 110 than a bonding method using a conductive bonding material.

  The material of the lens 110 is Si, which is a kind of infrared transmitting material. The lens 110 is formed using a LIGA process, or a semiconductor lens manufacturing method using an anodization technique (for example, Japanese Patent No. 3897055). For example, Japanese Patent No. 3897056). The lens 110 is adhered to the peripheral portion of the opening window 101 of the package lid 100 with a conductive adhesive (for example, solder, silver paste, etc.) so as to close the opening window 101 of the package lid 100, and the package The main body 90 is electrically connected to the shield conductor pattern 92. Therefore, in the above-described infrared sensor module, it is possible to prevent a decrease in the S / N ratio due to external electromagnetic noise. The lens 110 is provided with an appropriate infrared optical filter unit (a band pass filter unit, a broadband cutoff filter unit, etc.) formed by alternately laminating a plurality of types of thin films having different refractive indexes as necessary. You may do it.

  Further, in the above-described infrared sensor module, the base substrate 1 of the infrared sensor A has a rectangular outer peripheral shape, and all the pads 80 of the infrared sensor A are arranged side by side along one side of the outer peripheral edge of the base substrate 1, The signal processing IC chip B has a rectangular outer peripheral shape, and the pads electrically connected to the pads 80 of the infrared sensor A are arranged along one side of the outer peripheral edge of the signal processing IC chip B. Since the infrared sensor A and the signal processing IC chip B are arranged so that the one side of the base substrate 1 of the infrared sensor A and the signal processing IC chip B is closer than the other sides, the infrared sensor Since the wiring 81 connecting each pad 80 of A and each pad of the signal processing IC chip B can be shortened and the influence of external noise can be reduced, noise resistance is improved.

  Hereinafter, the structures of the thermal infrared detector 3 and the MOS transistor 4 will be described. In the present embodiment, as the silicon substrate 1a, a single crystal silicon substrate having an n-type conductivity and the (100) plane of the one surface is used.

  The thermal infrared detector 3 is formed in the formation area A1 of the thermal infrared detector 3 in each pixel unit 2 on the one surface side of the silicon substrate 1a, and the MOS transistor 4 is formed on the silicon substrate 1a. It is formed in the formation region A2 of the MOS transistor 4 in each pixel portion 2 on one surface side.

  Each pixel unit 2 includes an infrared absorption unit 33 (see FIGS. 1 and 6B) that absorbs infrared rays. In each pixel unit 2, the infrared absorption unit 33 is provided on the base substrate 1. A thin-film structure portion in which a digging portion 11 for thermal insulation from 1 is formed and has an infrared absorption portion 33 inside the digging portion 11 in a plan view on the one surface side of the base substrate 1 and covers the digging portion 11 3a is formed. Further, in each pixel portion 2, the thin film structure portion 3 a is juxtaposed along the circumferential direction of the digging portion by a plurality of linear slits 13, and each extends inward from the circumferential portion of the digging portion 11 in the base substrate 1. When a plurality of (six in the example shown in FIG. 3) small thin film structure portions 3aa are separated, a thermopile 30a is provided for each small thin film structure portion 3aa, and an output is taken out for each thermopile 30a. In comparison, all the thermopiles 30a are connected in series so that the output change with respect to the temperature change becomes large, and a connecting piece 3c that connects the adjacent small thin film structures 3aa, 3aa is formed. Below, each part divided | segmented corresponding to each small thin film structure part 3aa among the infrared absorption parts 33 is called the division | segmentation infrared absorption part 33a.

  Note that it is not always necessary to connect all of the plurality of thermopiles 30a formed in the thin film structure portion 3a, in the above example, all six thermopiles 30a in series. For example, a series circuit of three thermopiles 30a is provided. In this case, the sensitivity can be increased as compared with the case where all six thermopiles 30a are connected in parallel or the output is taken out for each thermopile 30a. Compared with the case where all the two thermopiles 30a are connected in series, the electric resistance of the temperature sensing unit 30 can be lowered and the thermal noise is reduced, so the S / N ratio is improved.

  Here, in the pixel portion 2, for each small thin film structure portion 3 aa, two planar strip-like bridge portions 3 bb and 3 bb connecting the base substrate 1 and the divided infrared absorbing portion 33 a are provided in the circumferential direction of the digging portion 11. A slit 14 having a U-shape in plan view is formed so as to be spatially separated from each other and to communicate with the digging portion 11 by separating the two bridge portions 3bb, 3bb and the split infrared absorbing portion 33a. Here, a portion of the base substrate 1 surrounding the thin film structure portion 3a in a plan view has a rectangular frame shape. The bridge portion 3bb is spatially separated from the split infrared ray absorbing portion 33a and the base substrate 1 by the slits 13 and 14 described above, except for the connecting portion between the infrared ray absorbing portion 33 and the base substrate 1. Here, the dimension in the extension direction of the small thin film structure portion 3aa from the base substrate 1 is 93 μm, the dimension in the width direction orthogonal to the extension direction of the small thin film structure portion 3aa is 75 μm, the width dimension of each bridge portion 3bb is 23 μm, Although the width of the slits 13 and 14 is set to 5 μm, these values are merely examples and are not particularly limited.

  The thin film structure 3a is formed on the silicon oxide film 1b formed on the one surface side of the silicon substrate 1a, the silicon nitride film 32 formed on the silicon oxide film 1b, and the silicon nitride film 32. The formed temperature sensitive part 30, the interlayer insulating film 50 made of a BPSG film formed so as to cover the temperature sensitive part 30 on the surface side of the silicon nitride film 32, the PSG film formed on the interlayer insulating film 50, and It is formed by patterning a laminated structure part with a passivation film 60 made of a laminated film with an NSG film formed on the PSG film.

In the present embodiment, portions of the silicon nitride film 32 other than the bridge portions 3bb and 3bb of the thin film structure portion 3a constitute the infrared absorbing portion 33 described above, and the silicon substrate 1a, the silicon oxide film 1b, the silicon nitride film 32, and the interlayer The insulating film 50 and the passivation film 60 constitute the base substrate 1. In the present embodiment, the laminated film of the interlayer insulating film 50 and the passivation film 60 is formed across the formation area A1 of the thermal infrared detector 3 and the formation area A2 of the MOS transistor 4. The portion formed in the formation region A1 of the thermal infrared detector 3 also serves as the infrared absorption film 70 (see FIG. 6B). Here, when the refractive index of the infrared absorption film 70 is n ₂ and the center wavelength of the infrared ray to be detected is λ, the thickness t2 of the infrared absorption film 70 is set to λ / 4n _2. The absorption efficiency of infrared rays of the target wavelength (for example, 8 to 12 μm) can be increased, and high sensitivity can be achieved. For example, when n ₂ = 1.4 and λ = 10 μm, t2≈1.8 μm may be set. In the present embodiment, the interlayer insulating film 50 has a thickness of 0.8 μm, the passivation film 60 has a thickness of 1 μm (the PSG film has a thickness of 0.5 μm, and the NSG film has a thickness of 0.5 μm). . In addition, the infrared absorption film 70 is not limited to the above-described configuration, and may be configured by, for example, a silicon nitride film.

  Moreover, in each pixel part 2, the inner peripheral shape of the dug part 11 is a rectangular shape, and the connecting piece 3c is formed in a cross shape in plan view, and an oblique direction intersecting with the extending direction of the small thin film structure part 3aa Small thin film structure portions 3aa, 3aa adjacent to each other, small thin film structure portions 3aa adjacent to each other in the extending direction of the small thin film structure portion 3aa, and small thin film structures adjacent to each other in the direction orthogonal to the extending direction of the small thin film structure portion 3aa The parts 3aa and 3aa are connected to each other.

  The thermopile 30a includes an elongated n-type polysilicon layer (n-type polysilicon element) 34 formed on the silicon nitride film 32 and straddling the small thin-film structure 3aa and the base substrate 1, and an elongated p-type poly. One end of the silicon layer (p-type polysilicon element) 35 is electrically divided by the first connecting metal portion 36 made of a metal material (for example, Al-Si) on the infrared incident surface side of the divided infrared absorbing portion 33a. The other end of the n-type polysilicon layer 34 of the thermocouple adjacent to each other on the one surface side of the base substrate 1 is provided (9 in the example shown in FIG. 3). And the other end portion of the p-type polysilicon layer 35 are joined and electrically connected by a second connecting metal portion 37 made of a metal material (for example, Al—Si). Here, in the thermopile 30a, the one end portion of the n-type polysilicon layer 34, the one end portion of the p-type polysilicon layer 35, and the first connecting metal portion 36 constitute a hot junction T1 on the split infrared absorbing portion 33a side. The other end portion of the n-type polysilicon layer 34, the other end portion of the p-type polysilicon layer 35, and the second connecting metal portion 37 constitute a cold junction T2 on the base substrate 1 side.

  Here, in the infrared sensor A of the present embodiment, the shape of the above-described dug portion 11 is a quadrangular pyramid shape, and the central portion in plan view has a larger depth dimension than the peripheral portion. The planar layout of the thermopile 30a in each pixel portion 2 is designed so that the hot junctions gather at the center of the thin film structure portion 3a. That is, in the middle two pixel portions 2 in the vertical direction of FIG. 3, as shown in FIGS. 1 and 3, the connecting portions 36 are arranged side by side along the juxtaposed direction of the three small thin film structure portions 3a. On the other hand, in the two upper pixel portions 2 in the vertical direction, as shown in FIG. 2 and FIG. 3, in the juxtaposition direction of the three small thin film structure portions 3aa, on the side closer to the middle small thin film structure portion 3aa. In the two lower pixel portions 2 in the vertical direction, the hot junctions T1 are concentrated, and as shown in FIG. 3, the small thin film structure in the middle in the juxtaposed direction of the three small thin film structure portions 3aa. The hot junctions T1 are concentrated on the side close to the portion 3aa. Thus, in the infrared sensor A of the present embodiment, the arrangement of the plurality of hot junctions T1 of the upper and lower small thin film structures 3aa in the vertical direction in FIG. 3 is the plurality of hot junctions of the middle small thin film structure 3aa. Since the temperature change of the hot junction T1 can be increased as compared with the case where the arrangement is the same as that of T1, the sensitivity can be improved.

  Further, the small thin film structure portion 3aa is formed from an n-type polysilicon layer that suppresses the warp of the small thin film structure portion 3aa and absorbs infrared rays in a region where the thermopile 30a is not formed on the infrared incident surface side of the silicon nitride film 32. An infrared absorption layer 39 (see FIGS. 3, 6 and 10) is formed. Further, the connecting piece 3c that connects adjacent small thin film structures 3aa, 3aa is provided with a reinforcing layer 39b (see FIG. 7) made of an n-type polysilicon layer that reinforces the connecting piece 3c. Here, the reinforcing layer 39 b is formed integrally with the infrared absorption layer 39. Therefore, in the infrared sensor A of the present embodiment, since the connecting piece 3c is reinforced by the reinforcing layer 39b, it is possible to prevent breakage due to stress generated due to external temperature change or impact during use. Damage during manufacturing can be reduced, and manufacturing yield can be improved. In the present embodiment, the length L1 of the connection piece 3c of the connection piece 3c shown in FIG. 7 is set to 24 μm, the width dimension L2 is set to 5 μm, and the width dimension L3 of the reinforcing layer 39b is set to 1 μm. The numerical value is an example and is not particularly limited. However, when the base substrate 1 is formed using the silicon substrate 1a and the reinforcing layer 39b is formed of an n-type polysilicon layer as in the present embodiment, the reinforcing layer 39b is etched when the digging portion 11 is formed. In order to prevent this, the width dimension of the reinforcing layer 39b is set to be smaller than the width dimension of the connecting piece 3c, and both side edges of the reinforcing layer 39b are positioned inside the both side edges of the connecting piece 3c in plan view. There is a need to.

  In addition, as shown in FIGS. 7 and 12B, the infrared sensor A of the present embodiment has chamfered portions 3d and 3d between the side edges of the connecting piece 3c and the side edges of the small thin film structure portion 3aa. A chamfered portion 3e is also formed between the side edges of the cross-shaped connecting piece 3c which are formed and are substantially orthogonal to each other. Therefore, in the infrared sensor A of the present embodiment, the stress concentration at the connecting portion between the connecting piece 3c and the small thin film structure portion 3aa is smaller than that in the case where the chamfered portion is not formed as shown in FIG. This can alleviate the residual stress generated during the manufacturing process and can reduce the damage during the manufacturing process, thereby improving the manufacturing yield. Further, it is possible to prevent damage due to stress generated due to an external temperature change or impact during use. In the example shown in FIG. 7, each of the chamfered portions 3 d and 3 e is an R chamfered portion having an R of 3 μm, but is not limited to the R chamfered portion, and may be a C chamfered portion, for example.

  In addition, the infrared sensor A of the present embodiment is routed to each pixel portion 2 so as to straddle the base substrate 1, one bridge portion 3 bb, the split infrared absorption portion 33 a, the other bridge portion 3 bb, and the base substrate 1. A fault diagnosis wiring 139 made of an n-type polysilicon layer is provided, and all the fault diagnosis wirings 139 are connected in series. Accordingly, by supplying power to the series circuit of the m × n failure diagnosis wirings 139, it is possible to detect the presence or absence of breakage such as breakage of the bridge portion 3bb.

The infrared absorbing layer 39, the reinforcing layer 39b, and the failure diagnosis wiring 139 described above have the same n-type impurity (for example, phosphorus) as the n-type polysilicon layer 34 and the same impurity concentration (for example, 10 ¹⁸ to 10 ²⁰ cm ^−3). And is simultaneously formed on the n-type polysilicon layer 34. Further, for example, boron may be adopted as the p-type impurity of the p-type polysilicon layer 35, and the impurity concentration may be appropriately set within a range of, for example, about 10 ¹⁸ to 10 ²⁰ cm ⁻³ . In the present embodiment, the impurity concentration of each of the n-type polysilicon layer 34 and the p-type polysilicon layer 35 is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the resistance value of the thermocouple can be reduced, and the S / N ratio can be improved. I can plan. The infrared absorption layer 39, the reinforcing layer 39b, and the failure diagnosis wiring 139 are doped with the same n-type impurity as the n-type polysilicon layer 34 at the same impurity concentration. The same impurity as that of the silicon layer 35 may be doped with the same impurity concentration.

By the way, in this embodiment, the refractive index of the n-type polysilicon layer 34, the p-type polysilicon layer 35, the infrared absorption layer 39, the reinforcing layer 39b, and the failure diagnosis wiring 139 is n ₁ , and the center wavelength of the infrared ray to be detected is set. when the lambda, so that to set the n-type polysilicon layer 34, p-type polysilicon layer 35, the infrared-absorbing layer 39, each of the thickness t1 reinforcing layer 39b and the fault diagnosis wirings 139 to lambda / 4n ₁ Therefore, the absorption efficiency of infrared rays having a wavelength to be detected (for example, 8 to 12 μm) can be increased, and high sensitivity can be achieved. For example, when n ₁ = 3.6 and λ = 10 μm, t 1 ≈0.69 μm may be set.

In the present embodiment, the impurity concentration of each of the n-type polysilicon layer 24, the p-type polysilicon layer 35, the infrared absorption layer 39, the reinforcing layer 39b, and the failure diagnosis wiring 139 is 10 ¹⁸ to 10 ²⁰ cm ⁻³ . Therefore, the reflection of infrared rays can be suppressed while increasing the infrared absorption rate, the S / N ratio of the output of the temperature sensing unit 30 can be increased, and the infrared absorption layer 39, the reinforcing layer 39b, and the failure Since the diagnostic wiring 139 can be formed in the same process as the n-type polysilicon layer 34, the cost can be reduced.

Here, the first connection metal portion 36 and the second connection metal portion 37 of the temperature sensing portion 30 are insulated and separated by the interlayer insulating film 50 on the one surface side of the base substrate 1 (FIG. 8). And FIG. 9). That is, the first connection metal portion 36 on the warm junction T1 side is electrically connected to the one end portions of the polysilicon layers 34 and 35 through the contact holes 50a ₁ and 50a ₂ formed in the interlayer insulating film 50, the second connecting metal part of the cold junction T2 side 37 is connected interlayer insulating film 50 contact holes _50a 3 formed, 50a ₄ through the above-described other end portion electrically both polysilicon layers 34 and 35 Yes.

  As can be seen from the above description, in the infrared sensor A of the present embodiment, the passivation film 60 is formed on both the thin film structure 3 a and the base substrate 1 on the outermost layer side of the thin film structure 3 a and the base substrate 1. The thermopile 30a includes an n-type polysilicon layer (n-type polysilicon element) 34 and a p-type polysilicon layer (p-type polysilicon element) 35 having different conductivity types in the first thin film structure portion 3a. The n-type polysilicon layer (n-type polysilicon element) 34 and the p-type polysilicon layer (p-type) having a plurality of hot junctions T1 formed by joining with the connecting metal portion 36 of The polysilicon element) 35 is formed by bonding the second connecting metal portion 37 around the perforated portion 11 of the base substrate 1. It has a cold junction T2 of the number.

  Here, the infrared sensor A of the present embodiment has resistance to an etchant (described later, for example, a TMAH solution) used when forming the dug portion 11, and has a plurality of hot junctions T1 of the thermopile 30a in plan view. The passivation film 60 is formed on the passivation film 60 so as to cover the concentrated area (in this embodiment, the area where all the hot junctions T1 are concentrated in each small thin film structure portion 30aa). A first soaking layer 71 (FIGS. 1, 2, 6, and 9) made of a heat conductive material (for example, a metal material such as Al—Si) having higher heat conductivity and resistance to the etchant. And a region where a plurality of cold junctions T2 of the thermopile 30a are provided in a concentrated manner (in this embodiment, all the sides of each small thin film structure portion 30aa The second soaking layer 72 (FIGS. 1, 2, 6 and 8) made of the above-described heat conductive material is formed on the passivation film 60 so as to cover the cold junction T2 in the region. ).

Further, as described above, the MOS transistor 4 is formed in the formation region A2 of the MOS transistor 4 in each pixel portion 2 on the one surface side of the silicon substrate 1a. Here, as shown in FIGS. 6 and 11, in the MOS transistor 4, a p ^{+ -type} well region 41 is formed on the one surface side of the silicon substrate 1a, and an n ⁺ -type drain is formed in the p ^{+ -type} well region 41. The region 43 and the n ^{+ -type} source region 44 are formed apart from each other. Further, the ^{p +} -type well region 41, ^{p ++} type channel stopper region 42 which surrounds the ^{n +} -type drain region 43 and ^{the n +} -type source region 44 is formed. Further, on the site located between the n ⁺ -type drain region 43 and the n ⁺ -type source region 44 in the p ⁺ -type well region 41, a gate insulating film 45 made of silicon oxide film (thermal oxide film) A gate electrode 46 made of an n-type polysilicon layer is formed. A drain electrode 47 made of a metal material (for example, Al—Si) is formed on the n ⁺ -type drain region 43, and a metal material (for example, Al—Si) is formed on the n ^{+ -type} source region 44. A source electrode 48 is formed. Here, the gate electrode 46, the drain electrode 47, and the source electrode 48 are insulated and separated by the interlayer insulating film 50 described above. That is, the drain electrode 47 is electrically connected to the n ⁺ -type drain region 43 through the contact hole 50 d formed in the interlayer insulating film 50, and the source electrode 48 is connected to the n ^{+ -type} through the contact hole 50 e formed in the interlayer insulating film 50. It is electrically connected to the source region 44.

By the way, in each pixel unit 2 of the infrared sensor A of the present embodiment, the source electrode 48 of the MOS transistor 4 and one end of the temperature sensing unit 30 are electrically connected, and the other end of the temperature sensing unit 30 is the reference bias line 5. Is electrically connected. In each pixel portion 2 of the infrared sensor A of the present embodiment, the drain electrode 47 of the MOS transistor 4 is electrically connected to the vertical readout line 7, and the gate electrode 46 is formed continuously and integrally with the gate electrode 46. It is electrically connected to a horizontal signal line 6 made of n-type polysilicon wiring. In each pixel unit 2, a ground electrode 49 made of a metal material (for example, Al—Si) is formed on the p ^{++ type} channel stopper region 42 of the MOS transistor 4. The p ^{++ -type} channel stopper region 42 is electrically connected to a common ground line 8 for element isolation by biasing to a lower potential than the n ⁺ -type drain region 43 and the n ^{+ -type} source region 44. The ground electrode 49 is electrically connected to the p ^{++ type} channel stopper region 42 through a contact hole 50f formed in the interlayer insulating film 50. On the passivation film 60, the heat conduction is performed on the passivation film 60 so as to cover a region where the gate electrode 46, the drain electrode 47, the source electrode 48, and the ground electrode 49 of the MOS transistor 4 are provided in a plan view. A protective metal layer 73 (FIGS. 6 and 11) made of a conductive material is formed.

  Hereinafter, the manufacturing method of the infrared sensor A of the present embodiment will be briefly described with reference to FIGS.

  First, a first silicon oxide film 31 having a first predetermined film thickness (for example, 0.3 μm) and a silicon nitride film having a second predetermined film thickness (for example, 0.1 μm) are formed on the one surface side of the silicon substrate 1a. An insulating layer forming step for forming an insulating layer made of a laminated film with the insulating film 32 is performed, and thereafter, using the photolithography technique and the etching technique, the insulating layer corresponding to the formation region A1 of the thermal infrared detecting portion 3 is used. The structure shown in FIG. 15A is obtained by performing an insulating layer patterning process in which a part corresponding to the formation region A2 of the MOS transistor 4 is removed while leaving a part of the part. Here, the silicon oxide film 31 is formed by thermally oxidizing the silicon substrate 1a at a predetermined temperature (for example, 1100 ° C.), and the silicon nitride film 32 is formed by LPCVD.

After the above-described insulating layer patterning step, a well region forming step for forming a p ^{+ -type} well region 41 on the one surface side of the silicon substrate 1a is performed, and subsequently, a p ^{+ -type} well on the one surface side of the silicon substrate 1 is performed. The structure shown in FIG. 15B is obtained by performing the channel stopper region forming step of forming the p ^{++ type} channel stopper region 42 in the region 41. Here, in the well region forming step, the second silicon oxide film (thermal oxide film) 51 is selectively formed by thermally oxidizing the exposed portion on the one surface side of the silicon substrate 1a at a predetermined temperature. The silicon oxide film 51 is patterned using a photolithographic technique and an etching technique using a mask for forming the p ^{+ -type} well region 41, and then ion implantation of a p-type impurity (for example, boron) is performed. After that, the p ^{+ -type} well region 41 is formed by performing drive-in. Further, in the channel stopper region forming step, a third silicon oxide film (thermal oxide film) 52 is selectively formed by thermally oxidizing the one surface side of the silicon substrate 1a at a predetermined temperature, and thereafter, p ^{++ type} The third silicon oxide film 52 is patterned using a photolithography technique and an etching technique using a mask for forming the channel stopper region 42, and then ion implantation of a p-type impurity (for example, boron) is performed. Then, drive-in is performed to form the p ^{++ type} channel stopper region 42. The first silicon oxide film 31, the second silicon oxide film 51, and the third silicon oxide film 52 constitute the silicon oxide film 1b on the one surface side of the silicon substrate 1a.

After the channel stopper region forming step described above, ion implantation of an n-type impurity (for example, phosphorus) is performed in the regions where the n ⁺ -type drain region 43 and the n ^{+ -type} source region 44 are to be formed in the p ^{+ -type} well region 41. perform source-drain formation step of forming a n ⁺ -type drain region 43 and the n ⁺ -type source region 44 by performing the drive from, after the source and drain formation step, heat to the first surface side of the silicon substrate 1a A gate insulating film forming step of forming a gate insulating film 45 made of a silicon oxide film (thermal oxide film) having a predetermined film thickness (for example, 600 mm) by oxidation is performed, and then, the entire surface of the one surface side of the silicon substrate 1a is formed. Gate electrode 46, horizontal signal line 6 (see FIG. 3), n-type polysilicon layer 34, p-type polysilicon layer 35, infrared absorption layer 39, reinforcement A polysilicon layer forming step of forming a non-doped polysilicon layer having a predetermined film thickness (for example, 0.69 μm) serving as a basis of the wiring 39b and the failure diagnosis wiring 139 by the LPCVD method is performed, and then the photolithography technique and the etching technique are used. Of the non-doped polysilicon layer, the gate electrode 46, the horizontal signal line 6, the n-type polysilicon layer 34, the p-type polysilicon layer 35, the infrared absorption layer 39, the reinforcing layer 39b, and the fault diagnosis wiring 139 are respectively corresponded. A polysilicon layer patterning step for patterning so that a portion remains is performed, and then, ion implantation of a p-type impurity (for example, boron) is performed on a portion corresponding to the p-type polysilicon layer 35 in the non-doped polysilicon layer. After that, the p-type polysilicon layer 35 is formed by driving. A p-type polysilicon layer forming step is performed, and then the n-type polysilicon layer 34, the infrared absorption layer 39, the reinforcing layer 39b, the failure diagnosis wiring 139, the gate electrode 46 and the horizontal signal line 6 among the non-doped polysilicon layers are formed. The n-type polysilicon layer 34, the infrared absorption layer 39, the reinforcing layer 39b, the failure diagnosis wiring 139, and the gate electrode 46 are obtained by performing driving after ion-implanting n-type impurities (for example, phosphorus) into the corresponding portions. Then, by performing the n-type polysilicon layer forming step for forming the horizontal signal line 6, the structure shown in FIG. The order of the p-type polysilicon layer forming step and the n-type polysilicon layer forming step may be reversed.

After the p-type polysilicon layer forming step and the n-type polysilicon layer forming step are completed, an interlayer insulating film forming step for forming an interlayer insulating film 50 on the one surface side of the silicon substrate 1a is performed, Contacts for forming the contact holes 50a ₁ , 50a ₂ , 50a ₃ , 50a ₄ , 50d, 50e, 50f (see FIGS. 8, 9, and 11) in the interlayer insulating film 50 by using the lithography technique and the etching technique. By performing the hole forming step, the structure shown in FIG. 16B is obtained. Here, in the interlayer insulating film formation step, a BPSG film having a predetermined film thickness (for example, 0.8 μm) is deposited on the one surface side of the silicon substrate 1a by the CVD method, and then at a predetermined temperature (for example, 800 ° C.). A planarized interlayer insulating film 50 is formed by reflow.

  After the contact hole forming step, the first connection metal portion 36, the second connection metal portion 37, the drain electrode 47, the source electrode 48, the reference bias line 5, and the vertical are formed on the entire surface of the silicon substrate 1a on the one surface side. A metal film (for example, Al--) having a predetermined film thickness (for example, 2 μm) serving as a basis for the readout line 7, the ground line 8, the common ground line 9, and the pads Vout, Vsel, Vref, Vdd, Gnd and the like (see FIG. 13). A metal film forming step of forming a Si film) by a sputtering method or the like, and then patterning the metal film using a photolithography technique and an etching technique to thereby form the first connecting metal portion 36 and the second connecting metal. Part 37, drain electrode 47, source electrode 48, reference bias line 5, vertical readout line 7, ground line 8, common ground line 9 and pads Vout, Vsel, ref, Vdd, by performing the metal film patterning step of forming a like Gnd, the structure shown in FIG. 17 (a). Etching in the metal film patterning step is performed by RIE. Moreover, the hot junction T1 and the cold junction T2 are formed by performing this metal film patterning process.

  After the metal film patterning step, a PSG film having a predetermined film thickness (for example, 0.5 μm) and a predetermined film thickness (for example, 0 μm) are formed on the one surface side of the silicon substrate 1a (that is, the surface side of the interlayer insulating film 50). And a passivation film forming step of forming a passivation film 60 made of a laminated film with a NSG film of .5 μm) by a CVD method, and then heat conduction made of the heat conductive material (for example, a metal material such as Al—Si). A heat conductive material film forming step of forming a conductive material film by sputtering or the like, and then patterning the heat conductive material film using a photolithography technique and an etching technique to thereby form the first soaking layer 71. The structure shown in FIG. 17B is obtained by performing a thermally conductive material film patterning step for forming the second soaking layer 72 and the protective metal 73. Note that the passivation film 60 is not limited to a stacked film of a PSG film and an NSG film, and may be a silicon nitride film, for example.

  After the above-described thermal conductive material film patterning step, a thermal insulating layer composed of a laminated film of the silicon oxide film 31 and the silicon nitride film 32, a temperature sensitive portion 30 formed on the thermal insulating layer, and a thermal insulating layer The above-described small thin film structure portion 3aa is patterned by patterning the laminated structure portion of the interlayer insulating film 50 formed so as to cover the temperature sensitive portion 30 on the surface side of the surface and the passivation film 60 formed on the interlayer insulating film 50. The structure shown in FIG. 18A is obtained by performing the stacked structure portion patterning step for forming. In the laminated structure patterning step, the slits 13 and 14 are formed.

After the laminated structure patterning step described above, a pad opening for forming a pad opening (not shown) for exposing the pads Vout, Vsel, Vref, Vdd, and Gnd using a photolithography technique and an etching technique. A formation step is performed, and then the above-described slits 13 and 14 are used as etchant introduction holes to introduce the etchant, and the silicon substrate 1a is anisotropically etched to form the digging portion 11 in the silicon substrate 1a. By performing the part forming step, the infrared sensor A in which the pixel parts 2 having the structure shown in FIG. 18B are arranged in a two-dimensional array is obtained. Here, the etching in the pad opening forming step is performed by RIE. In the trench forming step, a TMAH solution heated to a predetermined temperature (for example, 85 ° C.) is used as the etchant. However, the etchant is not limited to the TMAH solution, but other alkaline solutions (for example, ethylenediamine pyrocatechol). : EDP) may be used. In addition, since all the processes until the digging portion forming process is completed are performed at the wafer level, after the digging portion forming process is completed, a separation process for separating the individual infrared sensors A may be performed. Further, as can be seen from the above description, as for the manufacturing method of the MOS transistor 4, a well-known general MOS transistor manufacturing method is adopted, and a thermal oxide film is formed by thermal oxidation, a photolithography technique and etching. patterning the thermal oxide film by techniques, ion implantation of an impurity, by repeating the basic steps of the drive-in (diffusion of impurities), and p ⁺ -type well region 41, p ⁺⁺ type channel stopper region 42, n ⁺ form drain regions 43 An n ^{+ -type} source region 44 is formed.

  According to the infrared sensor A of the present embodiment described above, the infrared absorbing portion 33 and the thermopile 30a for detecting the temperature change of the infrared absorbing portion 33 are formed on the one surface side of the base substrate 1 formed using the silicon substrate 1a. A digging portion 11 is formed in the base substrate 1 to thermally insulate the infrared absorbing portion 33 from the base substrate 1. The digging portion 11 is formed inside the digging portion 11 in a plan view on the one surface side of the base substrate 1. The thin film structure portion 3a that is positioned and has the infrared absorption portion 33 is supported by the peripheral portion of the digging portion 11 in the base substrate 1, and the thin film structure portion 3a and the base substrate 1 on the outermost layer side of the thin film structure portion 3a and the base substrate 1 A passivation film 60 is formed so as to extend over the both, and has resistance to the above-mentioned etchant used when forming the dug portion 11, and in a plan view. A first soaking layer formed on the passivation film 60 so as to cover a region where the plurality of hot junctions T1 of the pile 30a are provided in a concentrated manner and made of a heat conductive material having a higher thermal conductivity than the passivation film 60. 71 and a second soaking material formed on the passivation film 60 and covering the region where the plurality of cold junctions T2 of the thermopile 30a are concentrated and provided with resistance to the etchant. Since the layer 72 is provided, even if cracks and pinholes are formed in the passivation film 60 due to a step at the hot junction T1 and the cold junction T2, the cracks and pinholes are first soaked. Since it is covered with the layer 71 and the second soaking layer 72, the thermopile 30a is immersed in the etchant used when forming the digging portion 11 during manufacturing. Can be prevented and reliability can be improved. In addition, the temperature of the plurality of hot junctions T1 can be made uniform by the first soaking layer 71 and the second soaking layer 72 can be used in use. Since the temperature of the plurality of cold junctions T1 can be made uniform, the sensitivity can be improved. In the infrared sensor A of the present embodiment, the infrared absorbing portion 33 formed of a part of the silicon nitride film 32 has a function of preventing the etchant from entering from the other surface side of the base substrate 1. Yes. The protective metal layer 73 formed on the passivation film 60 so as to cover the region where the gate electrode 46, the drain electrode 47, the source electrode 48, and the ground electrode 49 of the MOS transistor 4 are provided in a plan view. Etchant penetration is prevented and MOSFET 4 is also protected.

  Moreover, in the infrared sensor A of this embodiment, the material of each connection metal part 36 and 37 and the said heat conductive material are the same, The heat | fever of the material of each connection metal part 36 and 37 and the said heat conductive material is the same. Since the expansion coefficients are equal, it is possible to relieve the stress generated in the thin film structure portion 3a due to the expansion and contraction of the thin film structure portion 3a accompanying the temperature change. Further, since Al—Si is adopted as the heat conductive material, the processing of the first soaking layer 71 and the second soaking layer 72 by the above-described thermal conductive material film patterning step (thermal conductive material). The etching of the film is easy.

  Further, according to the infrared sensor A of the present embodiment, in each pixel unit 2, the dug portion 11 for thermally insulating the infrared absorption unit 33 from the base substrate 1 is formed on the base substrate 1. A thin film structure portion 3a having an infrared absorbing portion 33 inside the digging portion 11 in plan view on the one surface side and covering the digging portion 11 is formed, and the thin film structure portion 3a includes a plurality of linear slits 13. Are separated into a plurality of small thin film structure portions 3aa arranged in parallel along the circumferential direction of the dug portion 11 and extending inwardly from the circumference portion of the dug portion 11 in the base substrate 1, respectively. A thermopile 30a is provided for each thermopile, and all the thermopile 30a are electrically connected in a connection relationship in which the output change with respect to the temperature change is larger than when the output is taken out for each thermopile 30a. Thus, the response speed and the sensitivity can be improved, and the warping of each small thin film structure portion 3aa can be reduced by forming the connecting piece 3c that connects the adjacent small thin film structure portions 3aa and 3aa to each other. The structure stability can be improved and the sensitivity is stabilized.

  Moreover, since the infrared sensor A of this embodiment forms the above-mentioned dug part 11 in the shape of a square pyramid, when the base substrate 1 is formed using the silicon substrate 1a, the dug part 11 is made from an alkaline solution. It can be easily formed by anisotropic etching using the above etchant.

  Further, in the infrared sensor A of the present embodiment, on the infrared incident surface side of the silicon nitride film 32, in addition to the n-type polysilicon layer 34 and the p-type polysilicon layer 35, an infrared absorption layer 39, a reinforcing layer 39b, a failure diagnosis Since the wiring 139 is formed, the silicon nitride film 32 is prevented from being etched and thinned when the n-type polysilicon layer 34 and the p-type polysilicon layer 35 are formed (here, the above-described polysilicon layer patterning is performed). In the process, the silicon nitride film 32 can be prevented from being etched and thinned during over-etching when the non-doped polysilicon layer that is the basis of the n-type polysilicon layer 34 and the p-type polysilicon layer 35 is etched. The uniformity of the stress balance of the thin film structure portion 3a can be improved, and the infrared absorbing portion 33 is made thinner. Want also becomes possible to prevent warping of the small thin film structure 3aa, thereby improving the sensitivity. Here, the n-type polysilicon layer 34, the p-type polysilicon layer 35, the infrared absorption layer 39, the reinforcing layer 39b, and the failure diagnosis wiring 139 are the etching liquid (for example, TMAH solution) used in the above-described trench formation process. In order to prevent etching, it is necessary to design the shape in plan view so as not to be exposed on the inner surfaces of the slits 13 and 14.

  In the infrared sensor A of the present embodiment, the n-type polysilicon layer 34, the p-type polysilicon layer 35, the infrared absorption layer 39, the reinforcing layer 39b, and the failure diagnosis wiring 139 are set to the same thickness. Therefore, the uniformity of the stress balance of the small thin film structure portion 3aa is improved, and the warpage of the small thin film structure portion 3aa can be suppressed.

  In addition, since the infrared sensor A of the present embodiment includes the MOS transistor 4 for reading the output of the temperature sensing unit 30 for each pixel unit 2, the number of output pads Vout can be reduced, and the size and size can be reduced. Cost reduction can be achieved.

  By the way, in the above-described infrared sensor A, the digging portion 11 is formed by anisotropic etching using the dependence of the etching rate on the crystal plane orientation, using the silicon substrate having the one surface of (100) as the silicon substrate 1a. Is used as the silicon substrate 1a, and the silicon substrate having one surface of (110) is used as the silicon substrate 1a. As shown in FIG. You may form in the form penetrated in the thickness direction of silicon substrate 1a by anisotropic etching using. According to the configuration of FIG. 19, heat transfer from each small thin film structure portion 3aa of the thin film structure portion 3a to the base substrate 1 can be further suppressed, and higher sensitivity can be achieved.

  Further, as shown in FIG. 20, the digging portion 11 of the infrared sensor A is formed into a shape in which the inner surface of the digging portion 11 has a concave curved surface by using an etchant capable of isotropic etching as the etchant. It may be formed. According to the configuration shown in FIG. 20, the infrared light transmitted through the thin film structure portion 3 a can be reflected to the thin film structure portion 3 a side by the inner surface of the digging portion 11. The sensitivity can be improved.

  Further, as shown in FIG. 21, the infrared sensor A may have a configuration in which openings 12 for communicating a plurality of dug portions 11 are formed on the other surface side of the base substrate 1. 12, the region where the opening 12 is to be formed in the silicon substrate 1a from the other surface side of the base substrate 1 may be formed using an anisotropic etching technique using, for example, an ICP type dry etching apparatus. According to the infrared sensor A having the configuration shown in FIG. 21, similarly to the configuration shown in FIG. 20, heat transfer from each small thin film structure 3aa of the thin film structure 3a to the base substrate 1 can be further suppressed. High sensitivity can be achieved.

  Further, as shown in FIG. 22, the infrared sensor A has a direction in which small thin film structure portions 33a and 33a adjacent to each other in the extending direction of the small thin film structure portion 33a intersect the extending direction (that is, the small thin film structure portion 3aa). It is good also as a structure connected with the two connection pieces 3c spaced apart in the width direction. According to the infrared sensor A having the configuration shown in FIG. 22, since the connecting piece 3c connects the small thin film structure portions 3aa and 3aa adjacent in the extending direction of the small thin film structure portion 3aa, the small thin film structure portions 3aa, One end side of 3aa is directly supported by the peripheral portion of the digging portion 11 in the base substrate 1, while the other end side is a peripheral portion of the digging portion 11 in the base substrate 1 via the connecting piece 3c and another small thin film structure portion 3aa. As a result, each small thin film structure portion 3aa is supported at both ends by the base substrate 1, so that the warp of the small thin film structure portion 3aa can be reduced, the sensitivity is stabilized, and the manufacturing yield is improved. In addition, you may make it connect small thin film structure part 33a, 33a adjacent in the said extension direction by the one connection piece 3c in the center part of the width direction of small thin film structure part 3aa.

  Further, as shown in FIG. 23, the infrared sensor A has a small thin film structure adjacent in a direction orthogonal to the extending direction of the small thin film structure 3aa (the width direction of the small thin film structure 3aa, that is, the vertical direction in FIG. 23). The portions 3aa and 3aa may be connected to each other by one connecting piece 3c at a portion other than the bridge portion 3bb. According to the infrared sensor A having the configuration of FIG. 23, the connecting piece 3c connects the small thin film structure portions 3aa and 3aa adjacent to each other in the direction orthogonal to the extending direction of the small thin film structure portion 3aa. The torsional rigidity of the thin film structure portion 3aa is increased, the torsional deformation of each small thin film structure portion 3aa can be reduced, the sensitivity is stabilized, and the manufacturing yield is improved.

  In addition, as shown in FIGS. 24 and 25, the infrared sensor A may have a configuration in which the pixel portion 2 has a hexagonal shape in plan view and the pixel portions 2 are arranged in a honeycomb shape. Here, the thin film structure portion 3a is separated into six small thin film structure portions 3aa by the six slits 13, and the six small thin film structure portions 3aa are connected by the connecting piece 3c. The infrared sensor A having the configuration shown in FIG. 24 can prevent deformation of each small thin film structure portion 3aa and can increase the arrangement density of the pixel portions 2.

  By the way, in the infrared sensor A of each of the above embodiments, the MOS transistor 4 is provided in each pixel unit 2, but the MOS transistor 4 is not necessarily provided. The infrared sensor A does not necessarily need to be an infrared array sensor provided with the pixel units 2 in an array, and may be any sensor provided with at least one thermopile 30a.

A Infrared sensor 1 Base substrate 3a Thin film structure part 11 Digging part 30a Thermopile 33 Infrared absorption part 34 n-type polysilicon layer (n-type polysilicon element)
35 p-type polysilicon layer (p-type polysilicon element)
36 1st connection metal part 37 2nd connection metal part 71 1st soaking layer 72 2nd soaking layer T1 hot junction T2 cold junction

Claims (3)

  An infrared absorption portion and a thermopile for detecting a temperature change of the infrared absorption portion are provided on one surface side of a base substrate formed using a silicon substrate, and the infrared absorption portion is thermally insulated from the base substrate on the base substrate. A digging portion is formed, and the thin film structure portion having the infrared absorbing portion located inside the digging portion in a plan view on the one surface side of the base substrate is supported by a peripheral portion of the digging portion in the base substrate. An infrared sensor in which a passivation film is formed across the thin film structure portion and the outermost layer side of the base substrate, and the thermopile first connects two polysilicon elements of different conductivity types in the thin film structure portion. It has a plurality of hot junctions formed by joining with metal parts and has two polysilicon elements of different conductivity types as a base Having a plurality of cold junctions formed by joining with a second connecting metal part at the periphery of the digging part, having resistance to an etchant used when forming the digging part, and having a thermopile in plan view A first soaking layer formed on the passivation film so as to cover a region where a plurality of hot junctions are concentrated and having a higher thermal conductivity than the passivation film; and resistance to the etchant And a second soaking layer formed on the passivation film so as to cover a region where a plurality of cold junctions of the thermopile are provided in a concentrated manner. Sensor.   The infrared sensor according to claim 1, wherein the material of each of the connection metal portions and the thermally conductive material are the same.   The infrared sensor according to claim 1, wherein the thermally conductive material is a metal material.

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