JP2007078680A - Infrared sensor unit and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared sensor unit that is excellent in insulation performance and can be miniaturized. <P>SOLUTION: In the infrared sensor unit, a thermal type infrared sensor and a semiconductor device corresponding to this are formed on a common semiconductor base. An insulating upper layer is applied onto the semiconductor base to cover the semiconductor device formed on a surface section of the semiconductor base. The thermal type sensor is mounted on a sensor pedestal supported above the semiconductor device by a heat insulation supporting section, and the sensor pedestal and a heat insulation supporting member are made of a porous material stacked on the insulating upper layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an infrared sensor unit, and more particularly, to an infrared sensor unit including a thermal infrared sensor formed on a common semiconductor substrate and a semiconductor device related thereto, and a method for manufacturing the same.

Patent Document 1 (US Pat. No. 6,359,276) discloses an infrared sensor unit in which a thermal infrared sensor and a semiconductor device are arranged side by side on an upper surface of a semiconductor substrate. This thermal infrared sensor is supported on a semiconductor substrate by a porous heat insulating support, and this porous heat insulating support is realized as a part of the semiconductor substrate, on which the infrared sensor is placed. It insulates between the remaining semiconductor substrates. The porous heat insulating support is composed of a sensor pedestal and a pair of bridges that couple the sensor pedestal to the semiconductor substrate. The sensor pedestal and bridge are anodized on the surface layer of the doped region formed on the surface of the semiconductor substrate. It is formed by modifying to a porous body. Thus, in the prior art, the heat insulating support part for an infrared sensor is provided using the semiconductor substrate provided with the semiconductor device. However, in this case, since the heat insulating support portion is obtained by anodizing the surface layer portion of the semiconductor substrate in the lateral direction away from the semiconductor device, the infrared sensor is disposed immediately above the semiconductor device. There is a problem that cannot be done. Due to such limitations, it is difficult to reduce the size of the infrared sensor unit. In particular, when a thermal image sensor is constructed by two-dimensionally arranging a plurality of infrared sensor units, the sensor units cannot be arranged closely and the resolution is lowered.
US Pat. No. 6,359,276

  The present invention has been made to solve the above-described problems, and provides an infrared sensor unit that can be miniaturized together with a semiconductor device formed on a common semiconductor substrate.

  An infrared sensor unit according to the present invention includes a semiconductor substrate on which a semiconductor device is formed on a surface layer portion and an insulating upper layer that covers the semiconductor device is formed on an upper surface, and a sensor base on which a thermal infrared sensor is placed. A heat insulating support for supporting the sensor base is provided above the semiconductor device. Both the sensor base and the heat insulating support are formed of a porous material laminated on the upper surface of the insulating upper layer. For this reason, the infrared sensor can be placed above the semiconductor device in a sufficiently insulated state, making the entire infrared sensor unit compact and enabling applications where multiple infrared sensor units are densely arranged in two dimensions. It becomes.

  Preferably, the heat insulating support portion includes a pair of posts protruding to the insulating upper layer and a pair of horizontal beams extending from the posts and coupled to the sensor base, and the horizontal beam is parallel to the upper surface of the insulating upper layer. The sensor base is extended to be separated from the semiconductor device and supported. By providing such a post, the infrared sensor placed on the sensor pedestal can be supported at a sufficient distance above the semiconductor device, and sufficient heat insulation can be provided between the semiconductor substrate and the semiconductor device. Can be given.

  You may make it raise the sensitivity of an infrared sensor by forming the infrared reflector which reflects the infrared rays which pass an infrared sensor toward this infrared sensor in an insulating upper layer.

  Moreover, you may make it raise the sensitivity of an infrared sensor using the infrared rays absorber which coat | covers an infrared sensor alone or in combination with an infrared reflective film.

  The present invention further provides a method for manufacturing an infrared sensor unit. In this manufacturing method, after a semiconductor device is formed on the upper surface of the semiconductor substrate, an insulating upper layer is formed on the upper surface of the semiconductor substrate to hide the semiconductor device. Then, after forming a pair of terminal pads on the upper surface of the insulating upper layer, a sacrificial layer is laminated, and a through hole reaching each terminal pad is formed in the sacrificial layer. Next, the porous material is laminated on the sacrificial layer to form the porous layer, and the through-hole is filled with the porous material. Then, the heat insulation structure of a predetermined shape is obtained by selectively removing a part of porous layer. Before or after part of the porous layer is removed, a thermal infrared sensor is formed on the porous layer. Finally, the infrared sensor unit is obtained by removing the sacrificial layer. This heat insulation structure includes one post formed of a porous material filled in the above-mentioned through holes, a sensor base on which a thermal infrared sensor is placed, and a sensor base parallel to the upper surface of the insulating upper layer from each post. And a pair of horizontal beams. Each horizontal beam is formed with wiring from the infrared sensor to each terminal pad through each post. Therefore, by removing the sacrificial layer, the sensor base is supported above the semiconductor device by the horizontal beam and the post. In this method, the porous material can be selected from an appropriate material that is not limited to the semiconductor substrate, and sufficient mechanical strength and heat insulation performance can be realized. As the material, silicon oxide, siloxane organic polymer, siloxane inorganic polymer or silica airgel can be used.

  Furthermore, it is preferable to apply a sol-gel solution of a porous material on the sacrificial layer by spin coating. In this case, a porous layer having a uniform thickness can be easily formed.

  1 and 2 show an infrared sensor unit according to a first embodiment of the present invention. The infrared sensor unit includes a semiconductor device 20 formed on a surface layer portion of a single crystal silicon semiconductor substrate 10 and a thermal infrared sensor 30 supported by the semiconductor substrate 10 in a state of being separated from the semiconductor device 20. The The semiconductor device 20 is electrically connected to the infrared sensor 30 to give a sensor output to an external processing circuit. In this processing circuit, the sensor output relating to the amount of infrared light received by the infrared sensor is analyzed, and temperature measurement and infrared light are transmitted. Determine the presence of a radiating object. One typical usage is to configure a thermal image sensor by two-dimensionally arranging a plurality of infrared sensors.

  The semiconductor device 20 is, for example, a MOSFET transistor, and is turned on / off according to a trigger signal to give a sensor output. The transistor is formed on the upper surface of the semiconductor substrate 10 by a known method, and includes a doped well region 21 having a drain 22 and a source 23, a gate 24, a drain electrode 25, a source electrode 26, and a gate electrode. 28. Each of these electrodes is electrically connected to a terminal pad exposed on the upper surface of the infrared sensor unit. Hereinafter, the phrase “transistor” is used as a representative of the semiconductor device 20, but the present invention is not limited to using one transistor as shown. For example, when the insulating upper layer 12 made of SiO 2 or SiN is formed over substantially the entire upper surface of the semiconductor substrate 10 to cover the transistor 20 and an electrode pad associated with the transistor 20 is required on the upper surface, An insulating upper layer is formed except for the electrode pads.

  The thermal infrared sensor 30 is formed on the sensor pedestal 40, and the sensor pedestal is supported on the semiconductor substrate 10 by being separated from the transistor 20 by the heat insulating support 50. The thermal infrared sensor 30 is formed by forming a metal such as titanium on a band 32 patterned on the sensor pedestal 40, and gives an electric resistance that varies in proportion to the amount and intensity of incident infrared rays.

  The heat insulating support portion 50 includes a pair of posts 52 protruding on the semiconductor substrate 10 and a pair of horizontal beams 54 extending from each post to both ends of the sensor base 40 in parallel with the upper surface of the semiconductor substrate. The sensor pedestal 40, the post 52 and the horizontal beam 54 are formed of a porous material and efficiently insulate the infrared sensor 30 from the semiconductor substrate 10 and the transistor 20. The porous material used in the present embodiment is porous silica (SiO 2), and other examples include siloxane organic polymers, siloxane inorganic polymers, silica airgel, and the like. The patterned strip 32 extends through the beam 54 to the post 52 and is electrically connected to the terminal pads 14, 15 on the insulating upper layer 12. As shown in FIG. 3, the terminal pad 14 is connected to the reference voltage Vref, and the terminal pad 15 is connected to the source electrode 26 of the transistor 20. A gate electrode (not shown in FIG. 2) is connected to a corresponding terminal pad 28 through a buried line 27, and is connected to an external circuit that controls on / off of the transistor 20 through the pad 28. The drain electrode 25 is connected to the terminal pad 16 through a buried line 29, and provides a sensor output to an external circuit that detects infrared radiation from the target object.

  For example, an infrared reflector 17 made of a metal such as aluminum is formed on the upper surface of the insulating upper layer 12, and the infrared light that has passed through the infrared sensor 30 is reflected to the infrared sensor 30 side to increase the sensitivity of the infrared sensor 30. The distance (d) between the infrared sensor 30 and the infrared reflector 17 is set as d = λ / 4, where λ is the wavelength of infrared rays from the target object. When the infrared sensor 30 is used for human body detection, since the wavelength of infrared light from the human body is 10 μm, this distance (d) is 2.5 μm.

  The porosity of the porous material is preferably 40% to 80% in order to provide sufficient mechanical strength and a good heat insulating effect.

  The porous silica (SiO2) has an excellent heat insulation effect, so that the thermal conductivity of the semiconductor substrate 10 from the beam 54 is minimized, and at the same time, the heat capacity of the sensor base 40 is minimized and the sensitivity of the infrared sensor 30 is increased. Can do.

  The infrared sensor unit having the above-described configuration is manufactured through the processes shown in FIGS. After forming the transistor 20 on the upper surface of the semiconductor substrate 10, an insulating upper layer 12 of SiO2 is formed by thermal oxidation to cover the entire upper surface of the semiconductor substrate 10 as shown in FIG. Alternatively, the SiN insulating upper layer 12 is formed by a CVD method. Next, after the aluminum layer is formed on the insulating upper layer 12 by sputtering, this is selectively removed by etching, and the terminal pad 14 and the infrared reflector 17 are formed on the insulating upper layer 12 as shown in FIG. Form. Thereafter, a sacrificial layer 60 of an appropriate resist material is applied on the insulating upper layer 12 by a spin coating method, and then partially etched away to form the terminal pad 14 as shown in FIG. A through hole 62 to be exposed is formed. In addition to this, the sacrificial layer 60 may be formed of polyimide by spin coating, metal deposition, or polysilicon by CVD. When the sacrificial layer 60 is a resist material, the through-hole 62 is formed by lithography, and when the sacrificial layer 60 is polyimide, the through-hole 62 is formed by dry etching or wet etching, and the sacrificial layer 60 is made of metal or polysilicon. In this case, the through hole 62 can be formed by dry etching or wet etching.

  Next, porous silica (SiO 2) is applied to the entire upper surface of the sacrificial layer 60 by a spin coating method to form a porous layer 70 as shown in FIG. 52 is formed. Thereafter, the porous layer 70 is masked with an appropriate resist and selectively removed by etching to form the sensor base 40 and the beam 54 as shown in FIG. A hole 72 is formed. Next, after titanium is deposited in the sensor seat 40, the beam 54, and the through hole 72 by sputtering, a protective film of titanium nitride is formed on the titanium layer 80 as shown in FIG. Thereafter, the titanium layer 80 and the protective film are selectively removed to form an infrared sensor patterned band 32 on the sensor base 40 and the beam 54, as shown in FIG. The band 32 is electrically connected to the terminal pads 14 and 15 through the post 52. Finally, the sacrificial layer 60 is removed by etching to obtain the infrared sensor unit shown in FIG.

  5 and 6 show an infrared sensor unit according to the second embodiment of the present invention, which is basically the same as that of the first embodiment, and the structure of the thermal infrared sensor 30A is different. Similar members are indicated by numbers with an “A” appended to the end, and duplicate descriptions are omitted for the sake of brevity.

  The thermal infrared sensor 30A is configured by disposing an amorphous silicon resistance layer 130 between a lower electrode 131 and an upper electrode 132, and the electrodes are connected to terminal pads 14A and 15A via wiring 136, respectively. The resistance layer 130 disposed between the electrodes exhibits a resistance that changes in accordance with a change in the amount of incident infrared rays. The infrared sensor 30A configured as described above is mounted on the sensor base 40A, and the sensor base is supported on the semiconductor substrate 10A by the heat insulating support member 50A. The heat insulating support member 50A is formed of a porous material, and includes a pair of posts 52A and a pair of horizontal beams 54A extending from each post to both ends of the sensor base, as in the first embodiment. An infrared absorber 134 is provided on the upper electrode 132 to efficiently collect infrared rays. The infrared absorber 134 is formed of SiON, Si3N4, SiO2, or gold black.

  A process of manufacturing the infrared sensor unit will be described with reference to FIGS. 7 (A) to 8 (K). After the transistor 20A is formed on the single crystal silicon semiconductor substrate 10A, as shown in FIG. 7A, the entire upper surface of the semiconductor substrate 10A is covered with an insulating upper layer 12A of SiO2 formed by thermal oxidation. Next, the aluminum layer is coated on the insulating upper layer 12A by sputtering, and this is selectively etched away. As shown in FIG. 7B, the terminal pads 14A and 15A and the infrared reflection are formed on the insulating upper layer 12A. Leave body 17A. Thereafter, as shown in FIG. 7C, a sacrificial layer 60A of an appropriate resist material is applied to the entire surface of the insulating upper layer 12A by spin coating, and a part of the sacrificial layer 60A is removed by etching. As shown in (D), a through-hole 62A that exposes the terminal pads 14A and 15A is formed. Next, porous silica (SiO2) is applied to the entire upper surface of the sacrificial layer 60A by a spin coating method to form the porous layer 70A and the post 52A in the through-hole 62A. Etching is removed to form a through hole 72A that exposes the terminal pad 14A, as shown in FIG. Next, after vapor-depositing chromium on the porous layer 70A by sputtering, a part thereof is removed by etching, and as shown in FIG. 7F, the lower electrode 131 and the upper electrode 131 are formed on the porous layer 70A. A wiring 136 corresponding to is formed. Thereafter, amorphous silicon is deposited on the porous layer 70A through the lower electrode 131 by the CVD method, and selectively etched away to form a resistance on the lower electrode 131 as shown in FIG. Layer 130 is formed. Next, the porous layer 70A extending into the post 52A is selectively removed by etching to form a through hole 72A that exposes the corresponding terminal pad 15A, as shown in FIG. Further, after chromium is deposited on the porous layer 70A and the resistance layer 130, a part thereof is selectively removed by etching, and as shown in FIG. 8 (I), the upper electrode 132 and the upper electrode are removed. A wiring 136 extending to the terminal pad 15A is formed. Next, after depositing a SiON layer on the porous layer 70A through the upper electrode 132 and the corresponding wiring 136, the SiON layer is removed by etching, and as shown in FIG. Absorber 134 is formed. The sensor pedestal 40A and the beam 54 are formed by selectively removing the mask by masking with the porous layer 70A and an appropriate resist, and then the sacrificial layer 60 is removed by etching, and the infrared ray shown in FIG. A sensor unit is obtained.

  In the above-described embodiment, the porous layer and the corresponding member are formed of porous silica, but the present invention can use other porous materials, such as methyl-containing polysiloxane. Siloxane-based organic polymers, siloxane-based inorganic polymers such as SiH-containing siloxane, and silica airgel can be used.

  Further, the porous material may be a porous matrix composition comprising hollow fine particles and a matrix forming material. The hollow fine particles are particles having a hollow portion surrounded by an outer shell, and a metal oxide or silica is preferable as the outer shell. The hollow fine particles are selected from those disclosed in Japanese Patent Publication No. 2001-233611 or commercially available. In particular, the outer shell is selected from a single material of SiO2, SiOx, TiO2, TiOx, SnO2, CeO2, Sb2O5, ITO, ATO, Al2O3 or a mixture of any combination of these materials. The porous matrix composition forms a porous layer having a low thermal conductivity and a low specific heat after being coated on a substrate and dried. In the porous layer, the hollow fine particles are dispersed as a filler and are trapped in the matrix. The matrix-forming material includes a first type silicon compound having a siloxane bond, or a second type silicon compound that provides a siloxane bond when forming a film or layer. The second type silicon compound may have a siloxane bond. Examples of the first-type and second-type silicon compounds include organic silicon compounds, silicon halide compounds (for example, silicon chloride and silicon fluoride), and organic silicon halide compounds containing an organic group and halogen.

The silicon compound is a hydrolyzable organosilane, a hydrolyzed compound obtained by partially or completely hydrolyzing an organosilane, or a condensed compound of the hydrolyzed compound. RnSiY4-n represented by the formula
In the formula, R represents the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 9 carbon atoms, n represents an integer of 0 to 2, and Y represents a hydrolyzable functional group.
R in the above formula is an alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group). Group), aralkyl group (for example, 2-phenylethyl group, 2-phenylpropyl group, 3-phenylpropyl group), aryl group (for example, phenyl group, tolyl group), alkenyl group (for example, vinyl group, allyl group) Halogen substituted hydrocarbon groups (for example, chloromethyl group, γ-chloropropyl group, 3,3,3-trifluoropropyl group), substituted hydrocarbon groups (for example, γ-methacryloxypropyl group, γ-glycidoxy) Propyl group, 3,4-epoxycyclohexylethyl group, γ-mercaptopropyl group). Among these, an alkyl group having 1 to 4 carbon atoms and a phenyl group are preferable because of easy synthesis or availability.

Examples of the hydrolyzable functional group include an alkoxy group, an acetoxy group, an oxime group (—O—N═C—R (R ′)), an enoxy group (—O—C (R) ═C (R ′) R ″), An amino group, an aminoxy group (—O—N (R) R ′), an amide group (—N (R) —C (═O) —R ′) are included, and in these groups, R, R ′, R "" Is, for example, each independently a hydrogen atom or a monovalent hydrocarbon group).
Among these, an alkoxyl group is preferable from the viewpoint of availability.

Examples of the hydrolyzable organosilane include di-, tri-, and tetra-functional alkoxysilanes, acetoxysilanes, and oxime silanes in which n in the general formula (A) is an integer of 0 to 2. , Enoxysilanes, aminosilanes, aminoxysilanes, and amidosilanes. Among these, alkoxysilanes are preferable because of their availability.
Tetraalkoxysilane with n = 0 includes tetramethoxysilane and tetraethoxysilane, and organotrialkoxysilane with n = 1 includes methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, and phenyltrimethoxy. Silane, phenyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane are included. In addition, n = 2 diorganodialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane,
Methylphenyldimethoxysilane is included.

  In the above embodiment, an example is shown in which an infrared sensor that shows an electrical resistance value that varies according to the amount and rate of change of incident infrared rays is used. However, the dielectric constant changes according to changes in the amount of incident infrared rays A thermopile type that generates a thermoelectromotive force or a pyroelectric type that generates a voltage difference can be used.

It is a perspective view of the infrared sensor unit which concerns on the 1st Embodiment of this invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. It is a circuit diagram of said sensor unit. (A)-(H) are sectional drawings which show the manufacture process of said infrared sensor unit. It is a perspective view of the infrared sensor unit which concerns on the 2nd Embodiment of this invention. FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. (A)-(F) are sectional drawings which show the manufacture process of said infrared sensor unit. (G)-(K) are sectional drawings which show the manufacture process of said infrared sensor unit.

Explanation of symbols

10, 10A Semiconductor substrate 12, 12A Insulating upper layer 14, 14A Terminal pad 15, 15A Terminal pad 17, 17A Infrared reflector 20, 20A Semiconductor device 30, 30A Thermal infrared sensor 40, 40A Sensor base 50, 50A Thermal insulation support section 52, 52A Post 54, 54A Horizontal beam 60, 60A Sacrificial layer 62, 62A Through hole 70, 70A Porous layer 134 Infrared absorber

Claims (6)

A semiconductor substrate in which a semiconductor device is formed on the surface layer portion and an insulating upper layer covering the semiconductor device is formed on the upper surface; and
A thermal infrared sensor;
A sensor base for placing the thermal infrared sensor;
A heat-insulating support part for supporting the sensor base by floating from the upper surface of the semiconductor device,
The sensor base and the heat insulating support part are both formed of a porous material laminated on the upper surface of the insulating upper layer. The heat insulating support part is composed of a plurality of posts protruding on the semiconductor substrate and a plurality of horizontal beams, and each horizontal beam extends from each post in a form parallel to the insulating upper layer and is attached to the sensor base. The infrared sensor unit according to claim 1, wherein the sensor base is supported by being separated from the semiconductor device by being coupled. The infrared sensor unit according to claim 1, wherein an infrared reflector that reflects infrared light that has passed through the infrared sensor to the infrared sensor is formed on the semiconductor substrate. The infrared sensor unit according to any one of claims 1 to 3, wherein an upper surface of the infrared sensor is covered with an infrared absorber. Forming a semiconductor device on the upper surface of the semiconductor substrate;
Forming an insulating upper layer on the upper surface of the semiconductor substrate, covering the semiconductor device,
Forming a pair of terminal pads on a portion of the insulating upper layer;
A sacrificial layer is laminated on the upper surface of the insulating upper layer, and a pair of through holes exposing the terminal pads are formed in a part of the sacrificial layer,
Applying a layer of porous material on the upper surface of the sacrificial layer and filling the pores with the porous material to form a porous layer,
Etching the porous layer into a predetermined pattern to form a heat insulating structure,
Laminating a thermal infrared sensor on the upper surface of the heat insulating structure,
A method of removing the sacrificial layer by etching,
The heat insulating structure includes a pair of posts formed of a porous material filled in the through holes, a sensor base on which the thermal infrared sensor is mounted, and extends from each post in parallel with the upper surface of the insulating upper layer. And a pair of horizontal beams coupled to the sensor pedestal,
A wiring extending through the post from the thermal infrared sensor to the terminal pad is formed along each horizontal beam,
By removing the sacrificial layer, the sensor pedestal is supported on the upper surface of the semiconductor substrate by the horizontal beam in a state of being separated immediately above the semiconductor device. . 6. The method of manufacturing an infrared sensor unit according to claim 5, wherein the sol-gel solution of the porous material is applied onto the sacrificial layer by a spin coating method.

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