WO2012137539A1 - Ultraviolet sensor - Google Patents

Ultraviolet sensor Download PDF

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Publication number
WO2012137539A1
WO2012137539A1 PCT/JP2012/053424 JP2012053424W WO2012137539A1 WO 2012137539 A1 WO2012137539 A1 WO 2012137539A1 JP 2012053424 W JP2012053424 W JP 2012053424W WO 2012137539 A1 WO2012137539 A1 WO 2012137539A1
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WO
WIPO (PCT)
Prior art keywords
film
protective film
waves
ultraviolet
light
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PCT/JP2012/053424
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French (fr)
Japanese (ja)
Inventor
裕徳 難波
聡 和賀
康男 早川
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アルプス電気株式会社
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Priority to JP2013508782A priority Critical patent/JPWO2012137539A1/en
Publication of WO2012137539A1 publication Critical patent/WO2012137539A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/283—Interference filters designed for the ultraviolet
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02162—Coatings for devices characterised by at least one potential jump barrier or surface barrier for filtering or shielding light, e.g. multicolour filters for photodetectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
    • H01L31/03529—Shape of the potential jump barrier or surface barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/103—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN homojunction type

Definitions

  • the present invention relates to an ultraviolet sensor, and more particularly to an ultraviolet sensor capable of being thinned and capable of reducing manufacturing costs.
  • an ultraviolet sensor that can be mounted on a portable electronic device such as a mobile phone so that the amount of ultraviolet light can be measured simply and the ultraviolet light countermeasure can be taken effectively.
  • Such an ultraviolet sensor is required to be small and thin in addition to having good light receiving sensitivity with respect to the amount of ultraviolet light irradiated.
  • FIG. 7 a cross-sectional view of the ultraviolet sensor 101 disclosed in Patent Document 1 is shown in FIG.
  • the ultraviolet sensor 101 shown in FIG. 7 is composed of a semiconductor substrate 111, an insulating oxide film 112, and an SOI substrate 110 having an SOI (Silicon On Insulator) layer 113 stacked on the oxide film 112.
  • SOI Silicon On Insulator
  • N-type diffusion regions 114 and P-type diffusion regions 115 are alternately formed to constitute a lateral type diode including a lateral PN junction region.
  • the diode formed on the SOI substrate 110 has light receiving sensitivity in a wide wavelength region, the light reaching the SOI layer 110 is limited to a wavelength equal to or less than a predetermined wavelength (that is, shielding incident light of a predetermined wavelength or more)
  • the filter film 130 in order to provide a predetermined distance between the filter film 130 and the SOI layer 113, it is necessary to form a frame (not shown) for supporting the filter film 130 on the outer periphery of the semiconductor substrate 111.
  • the frame is provided so as to surround the SOI layer 113, and the filter film 130 is formed on the frame so as to cover the SOI layer 113.
  • the distance between the SOI layer 113 and the filter film 130 is formed.
  • a recessed package and store the SOI substrate 110 therein.
  • An insertion portion for fixing the filter film 130 is formed in the vicinity of the opening of the concave package, and the filter film 130 can be fixed using an adhesive.
  • the space between the SOI layer 113 and the filter film 130 is provided by appropriately designing the height of the package or forming the position of the insertion portion at a predetermined position.
  • the conventional ultraviolet sensor 101 since it is necessary to prepare such a frame or package and provide a space between the SOI layer 113 and the filter film 130, it is difficult to miniaturize and thin the ultraviolet sensor 101. Furthermore, since the process of forming the frame and the process of preparing the package and adhering the filter film 130 are required, it is difficult to reduce the manufacturing cost.
  • the filter film 130 is generally laminated on a quartz substrate (not shown) having good light transmittance and adhered to a frame or a package.
  • the quartz substrate is required to have sufficient strength so as to prevent breakage and cracking in the manufacturing process and to ensure reliability in a drop test and the like.
  • the quartz substrate is formed to have a thickness of, for example, about 0.3 mm to 0.5 mm, which has been an obstacle to reducing the thickness of the ultraviolet sensor 101. Further, the quartz substrate is an expensive member, which has been an obstacle to cost reduction.
  • An object of the present invention is to solve the above-mentioned problems, and to provide an ultraviolet sensor which can realize thinning and reduce the manufacturing cost.
  • the ultraviolet sensor according to the present invention transmits a light receiving element that generates light by receiving light containing ultraviolet light, a protective film laminated on the light receiving surface side of the light receiving element, and UV-A waves and UV-B waves. And the filter film is laminated on the surface of the protective film.
  • the filter film without providing a space between it and the protective film, and it is possible to omit the quartz substrate and the like used as a support substrate for the filter film. Can be realized.
  • the process of forming the frame for supporting the filter membrane and adhering the filter membrane, or the process of preparing and assembling the package, etc. is not necessary, so that the manufacturing cost can be reduced. Furthermore, since the filter film can be formed without using an expensive quartz substrate, the manufacturing cost can be further reduced.
  • the protective film is preferably formed to have a film thickness of 98 nm to 117 nm, 194 nm to 217 nm, or 291 nm to 314 nm.
  • the reflectance of UV-B waves generated by the filter film and the protective film can be suppressed to 45% or less, and the reflectance of UV-A waves can be suppressed to 50% or less Therefore, it is possible to provide an ultraviolet sensor having better light receiving sensitivity for UV-A waves and UV-B waves.
  • the difference between the reflectances of the UV-B wave and the UV-A wave can be suppressed to 10% or less, it is possible to suppress the variation in light receiving sensitivity to the UV-A wave and the UV-B wave.
  • the protective film is preferably formed using silicon oxide.
  • the SOI layer can be well protected, and characteristic deterioration due to external environment (humidity, temperature, etc.) or mechanical damage can be prevented.
  • the light transmittance in the wavelength range of UV-A waves and UV-B waves is high and the refractive index is low, it is possible to improve the light reception sensitivity of the ultraviolet sensor.
  • the filter film is composed of a multilayer film in which low refractive index materials (refractive index 1.3 to 1.5) and high refractive index materials (refractive index 1.9 to 2.2) are alternately laminated. Is preferred. In this way, UV-A waves and UV-B waves are transmitted, and good filter characteristics for blocking UV-C waves (ultraviolet light having a wavelength of about 280 nm or less) and visible light (light having a wavelength of about 400 nm or more) are obtained. be able to.
  • the light receiving element preferably includes a semiconductor substrate, an oxide layer formed on the semiconductor substrate, and an SOI layer formed on the oxide layer. is there. In this way, it is possible to provide an ultraviolet sensor that has good light receiving sensitivity to UV-A waves and UV-B waves, and that can be miniaturized and thinned.
  • the filter film can be formed without providing a space between the protective film, and the quartz substrate etc. used as a support substrate for the filter film can be omitted. Thinning can be realized.
  • the process of forming the frame for supporting the filter membrane and adhering the filter membrane, or the process of preparing and assembling the package, etc. is not necessary, so that the manufacturing cost can be reduced. Furthermore, since the filter film can be formed without using an expensive quartz substrate, the manufacturing cost can be further reduced.
  • the ultraviolet ray sensor of the present invention it is possible to provide an ultraviolet ray sensor which can realize a reduction in thickness and can reduce the manufacturing cost.
  • FIG. 2 is a schematic cross-sectional view of the ultraviolet sensor cut along the line II-II in FIG. It is a schematic cross section which shows the structure of the filter film in an ultraviolet sensor. It is a graph which shows the relationship of reflectance and wavelength when a filter film
  • (A) A graph showing the relationship between the average reflectance of UV-A waves and the average reflectance of UV-B waves and the film thickness of the protective film,
  • FIG. 1 the model top view of the ultraviolet-ray sensor 1 in this embodiment is shown.
  • FIG. 2 shows a schematic cross-sectional view of the ultraviolet sensor 1 cut along the line II-II in FIG.
  • the protective film 20 and the filter film 30 are omitted.
  • the ultraviolet sensor 1 of the present embodiment is stacked on a semiconductor substrate 11, an oxide film 12 formed on the semiconductor substrate 11, an SOI layer 13 formed on the oxide film 12, and an SOI layer 13.
  • a filter film 30 which transmits UV-A waves and UV-B waves.
  • the SOI substrate 10 is composed of the semiconductor substrate 11, the oxide film 12 and the SOI layer 13, and the semiconductor substrate 11 and the SOI layer 13 are insulated by the oxide film 12.
  • the E + -shaped N + region 14 and the ⁇ -shaped P + region 15 are formed to face each other.
  • the comb teeth 14a of the N + region 14 and the comb teeth 15a of the P + region 15 are formed, respectively, and the comb teeth 14a and the comb teeth 15a are spaced apart from each other. It is arranged to be engaged.
  • the N + region 14 is a high concentration N type diffusion region formed by diffusing an N type impurity such as phosphorus (P) or arsenic (As) at a relatively high concentration in the SOI layer 13.
  • the P + region 15 is a high concentration P type diffusion region formed by diffusing a P type impurity such as boron (B) to a relatively high concentration.
  • a P ⁇ region 16 in which a P-type impurity is diffused to a relatively low concentration is formed between the opposing N + region 14 and the P + region 15.
  • a lateral PN junction is formed by the N + region 14, the P + region 15 and the P ⁇ region 16 to form a lateral photodiode.
  • a depletion layer (not shown) is formed in the P ⁇ region 16, and when light including ultraviolet light is irradiated in the vicinity of the depletion layer, electron-hole pairs are generated.
  • wiring electrode layers (not shown) formed of conductive materials such as aluminum (Al), titanium (Ti), tungsten (W), etc. in N + region 14 and P + region 15 ) Is connected.
  • the wiring electrode layer is drawn to the outside through contact holes (not shown) formed in the protective film 20 and the filter film 30, and an output current generated by the received light can be extracted.
  • the wiring electrode layer and the contact hole are formed so as not to overlap with the P ⁇ region 16 which is the light receiving region.
  • the ultraviolet sensor 1 is not limited to the configuration as shown in FIG. 1, and the configuration in which the comb teeth 14a of the N + region 14 and the comb teeth 15a of the P + region 15 are increased, or the comb teeth are not provided.
  • the N + region 14 and the P + region 15 formed in an I shape may be opposed to each other.
  • the SOI substrate 10 is not particularly limited in its configuration or manufacturing method.
  • the SOI substrate 10 for example, one manufactured by a bonding method or a SIMOX (Silicon Implanted Oxide) method can be used.
  • a protective film 20 is formed on the light receiving surface side of the SOI layer 13.
  • the protective film 20 is formed to protect the SOI layer 13 from external environment (humidity, temperature, etc.), mechanical damage in the manufacturing process, chemical damage such as chemicals, and the like.
  • the protective film 20 is preferably formed of an insulating material having a high light transmittance in the wavelength range of UV-A waves and UV-B waves and a low refractive index.
  • an insulating material such as silicon oxide (SiO 2 ) or NSG (Nondoped Silica Glass) can be used, and in this embodiment, it is formed using silicon oxide.
  • UV light refers to light having a wavelength shorter than visible light, and refers to light with a wavelength of 100 nm to 400 nm.
  • UV (Ultraviolet) is synonymous with an ultraviolet-ray.
  • UV-A wave the long wavelength ultraviolet light
  • UV-B wave the intermediate wavelength ultraviolet light
  • UV- C wave the short wavelength ultraviolet light
  • UV-C waves have stronger energy than UV-A waves and UV-B waves, and are considered to have strong bactericidal action, but most of the UV-C waves of sunlight are absorbed by the ozone layer It has never been reached the earth. Therefore, the ultraviolet sensor 1 has good light receiving sensitivity for UV-A waves and UV-B waves, and for light of other wavelengths (UV-C waves and wavelength regions of visible light or more) Is required not to be detected.
  • the thickness of the SOI layer is formed to be approximately 200 nm to 400 nm.
  • the lateral photodiode formed on the SOI substrate 10 has light receiving sensitivity over a wide wavelength range including ultraviolet light and visible light. Therefore, the UV-A wave and the UV-B wave are transmitted, and the filter film 30 having a filter characteristic capable of shielding the UV-C wave and the visible light is laminated on the surface of the protective film 20.
  • the ultraviolet sensor 1 can detect the UV-A wave and the UV-B wave transmitted through the filter film 30 and received in the light receiving area of the lateral photodiode.
  • the filter film 30 is laminated on the surface of the protective film 20.
  • the filter film 30 can be formed without providing a space between the filter film 30 and the protective film 20.
  • the manufacturing cost can be reduced. Furthermore, since the filter film 30 can be formed without using an expensive quartz substrate, the manufacturing cost can be further reduced.
  • FIG. 3 shows a schematic cross-sectional view of the filter film 30 in the present embodiment.
  • low refractive index material reffractive index 1.3 to 1.5
  • high refractive index material reffractive index 1.9 to 2.2
  • MgF 2 magnesium fluoride
  • SiO 2 silicon oxide
  • Al 2 O 3 aluminum oxide
  • the high refractive index material 32 may be tantalum oxide (Ta 2 O 5 ), zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), lanthanum oxide (La 2 O 3 ), or any one of the respective materials. A mixed material etc. can be used.
  • the filter film 30 is configured such that the high refractive index material 32 is disposed on the protective film 20 side, and the low refractive index material 31 is disposed on the light receiving surface side of the filter film 30.
  • the low refractive index material 31 and the high refractive index material 32 can be formed by a thin film method such as a vapor deposition method, and form a multilayer film in which 20 or more layers are alternately stacked.
  • the filter film 30 has a configuration in which 24 layers are stacked, and the total thickness thereof is about 2 ⁇ m.
  • FIG. 4 shows the relationship between the reflectance of the filter film 30 alone and the wavelength of light in the present embodiment, and the relationship between the reflectance and the wavelength of light when the filter film 30 is stacked on the protective film 20.
  • the film thickness of the protective film 20 at this time is formed to be about 344 nm.
  • the reflectance of the filter film 30 alone is about 10% in the wavelength range (280 nm to 400 nm) of the UV-A wave and the UV-B wave, and the UV-C wave (280 nm or less) and In the visible light region (400 nm or more), the reflectance is 90% or more. That is, it can be said that the filter film 30 has a good filter characteristic of transmitting only the UV-A wave and the UV-B wave.
  • the thickness of the SOI layer 13 is thin as described above, so that the near infrared region Light of a wavelength in the region is transmitted without being absorbed by the photodiode of the SOI layer 13. For this reason, light in the near infrared region transmitted through the filter film 30 is not detected, and the detection sensitivity of the ultraviolet sensor 1 is not affected. Therefore, the ultraviolet sensor 1 can have good light receiving sensitivity to UV-A waves and UV-B waves.
  • the reflectance of UV-B waves (280 nm to 320 nm) increases to about 50% to 65%, and the reflectance of UV-A waves (320 nm to 400 nm) is about 22% to 50%, and the wavelength dependence is Increase.
  • the difference between the reflectance of the UV-A wave and the reflectance of the UV-B wave is also large.
  • the detection sensitivity of the ultraviolet sensor 1 is lowered. Since the UV-B wave has stronger energy than the UV-A wave, it is not preferable that the detection sensitivity of the UV-B wave is lowered. Also, as shown in FIG. 4, when the difference in reflectance between UV-A and UV-B waves is large, or when the wavelength dependency of the reflectance is large, the variation in detection sensitivity is large depending on the wavelength of incident light. Therefore, the detection accuracy of the ultraviolet ray sensor 1 may be reduced.
  • FIG. 5A shows the relationship between the average reflectance of the UV-A wave and the UV-B wave and the film thickness of the protective film 20 for the ultraviolet sensor 1 in which the protective film 20 and the filter film 30 are stacked on the SOI substrate 10.
  • the reflectances of the UV-A wave and the UV-B wave change with periodicity.
  • the reflectance of UV-A waves changes periodically in the range of about 33% to 51%
  • the reflectance of UV-B waves changes in the range of about 38% to 60%.
  • FIG. 5 (b) is a graph showing the difference between the average reflectance of the UV-A wave and the average reflectance of the UV-B wave shown in FIG. 5 (a).
  • FIG. 5 (b) shows the value calculated by (average reflectance of UV-B waves)-(average reflectance of UV-A waves), and in the region where the difference in average reflectance in the graph is positive, And UV-B waves are greater than UV-A waves.
  • the difference in average reflectance largely fluctuates with the film thickness of the protective film 20.
  • the ultraviolet sensor 1 is required to have good detection sensitivity for UV-B waves having stronger energy and to have small variation in detection sensitivity between UV-A waves and UV-B waves. There is.
  • the average reflectance of the UV-B wave shown in FIG. 5A is low and the difference in the average reflectance shown in FIG. 5B is close to zero.
  • the thickness of the protective film 20 is changed variously in FIGS. 5A and 5B, the thickness and the configuration of the filter film 30 are not changed, and they are shown in FIGS. 3 and 4. It has a configuration and filter characteristics.
  • the protective film 20 is formed of silicon oxide (SiO 2 ) which is a low refractive material having a refractive index of about 1.35 to 1.48.
  • both the reflectance of the UV-A wave (ultraviolet light of wavelength 320 nm to 400 nm) and the UV-B wave (ultraviolet light of wavelength 280 nm to 320 nm) generated by the filter film 30 and the protective film 20 can be reduced. Is possible.
  • ⁇ 311 nm is the central wavelength of the ultraviolet wavelength (280 nm to 350 nm).
  • the protective film 20 is more preferably formed to have a film thickness of 98 nm to 117 nm, 194 nm to 217 nm, or 291 nm to 314 nm.
  • the protective film 20 in this film thickness range, the reflectance of UV-B waves generated by the filter film 30 and the protective film 20 can be suppressed to 45% or less. Therefore, good light receiving sensitivity can be obtained for UV-B waves having stronger energy than UV-A waves.
  • the difference in reflectance between UV-A and UV-B waves can be suppressed to 10% or less, it is possible to suppress variations in light receiving sensitivity to UV-A waves and UV-B waves. .
  • FIG. 6 is a graph showing the relationship between the reflectance and the wavelength when the filter film 30 is stacked on the protective film 20 with different thicknesses.
  • the optical film thickness of the protective film 20 is 0.246 ⁇ ⁇ ⁇ 2 (actual film thickness about 102 nm), 0.246 ⁇ ⁇ ⁇ 4 (actual film thickness about 204 nm), 0.246 ⁇ ⁇ ⁇ 4 It shows the reflectance when it is formed on (the actual film thickness of about 306 nm).
  • any optical film thickness in the range of 0.246 ⁇ ⁇ ⁇ (2 ⁇ n ⁇ 0.3) to 0.246 ⁇ ⁇ ⁇ (2 ⁇ n + 0.3) ( ⁇ 311 nm, n is a natural number of 1 or more) And within the film thickness range of 98 nm to 117 nm, or 194 nm to 217 nm, or 291 nm to 314 nm. Further, as a comparison, the reflectance when the filter film 30 is laminated on the protective film 20 having an optical film thickness of 0.246 ⁇ ⁇ ⁇ 7 (actual film thickness of about 357 nm) is shown.
  • Each of the filter films 30 has the configuration and filter characteristics as shown in FIGS. 3 and 4.
  • the reflectance shows up to about 65% in the wavelength region of the UV-B wave
  • the average reflectance of the UV-B wave is as high as about 58%. Therefore, most of the incident UV-B wave light is reflected by the filter film 30 and the protective film 20, the amount of light received by the photodiode decreases, and the detection sensitivity decreases.
  • the wavelength dependency of the reflectance is large, and it can be seen that the reflectance changes from about 50% to 23%. In the case of such a characteristic, the variation in detection sensitivity becomes large depending on the wavelength of incident light, and there is a possibility that accurate measurement can not be performed.
  • the maximum reflectance in the wavelength region of the UV-B wave is All are suppressed to 50% or less, and the average reflectances are about 38%, 39%, and 42%, respectively (see FIG. 5A). Further, the reflectance in the wavelength region of the UV-A wave shows a flat characteristic with respect to the change of the wavelength, and the difference from the reflectance in the UV-B wave region is also suppressed small.
  • the filter film 30 is formed on the protective film 20 formed to have the above-mentioned film thickness, it is preferable that the UV-A wave and the UV-B wave are transmitted and the UV-C wave and the visible light are not transmitted. It can be said that it has filter characteristics.
  • the filter film 30 is laminated on the surface of the protective film 20 to realize the thinning of the ultraviolet sensor 1 and, by changing the film thickness of the protective film 20, the UV-A wave and the UV-B wave It has been shown that it is possible to provide an ultraviolet sensor 1 having good light receiving sensitivity and capable of suppressing variations in light receiving sensitivity to UV-A waves and UV-B waves.
  • UV sensor 10 SOI substrate 11 semiconductor substrate 12 oxide film 13 SOI layer 14 N + region 15 P + region 16 P- region 20 protective film 30 filter film 31 low refractive index material (refractive index 1.3 to 1.5) 32 High refractive index material (refractive index 1.9 to 2.2)

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  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
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  • Optics & Photonics (AREA)
  • Light Receiving Elements (AREA)
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Abstract

[Problem] The purpose of the present invention is to provide an ultraviolet sensor in which a thinner profile can be realized, and production costs can be reduced. [Solution] This ultraviolet sensor (1) has a light receiving element (2) for receiving light that includes ultraviolet light, and generating an electric current; a protective film (20) stacked on the light receiving side of the light receiving element (2); and a filter film (30) that transmits UV-A and UV-B waves. The filter film (30) is stacked on the surface of the protective film (20).

Description

紫外線センサUV sensor
　本発明は、紫外線センサに関し、特に、薄型化が可能であるとともに製造コストの低減が可能な紫外線センサに関する。 BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an ultraviolet sensor, and more particularly to an ultraviolet sensor capable of being thinned and capable of reducing manufacturing costs.
　近年、オゾン層の破壊により地上に照射される紫外線量が増加していることが知られており、人体や環境に及ぼす紫外線の影響が懸念されている。このため、簡便に紫外線量を計測して効果的に紫外線対策を行うことができるように、携帯電話等の携帯用電子機器に搭載可能な紫外線センサが求められている。このような紫外線センサは、照射される紫外線量に対して良好な受光感度を有することに加えて、小型、薄型であることが要求されている。 In recent years, it is known that the amount of ultraviolet rays irradiated to the ground increases due to the destruction of the ozone layer, and there is a concern about the influence of the ultraviolet rays on the human body and the environment. Therefore, there is a need for an ultraviolet sensor that can be mounted on a portable electronic device such as a mobile phone so that the amount of ultraviolet light can be measured simply and the ultraviolet light countermeasure can be taken effectively. Such an ultraviolet sensor is required to be small and thin in addition to having good light receiving sensitivity with respect to the amount of ultraviolet light irradiated.
　従来例の紫外線センサとして、例えば、特許文献１に開示されている紫外線センサ１０１の断面図を図７に示す。図７に示す紫外線センサ１０１は、半導体基板１１１と、絶縁性の酸化膜１１２と、酸化膜１１２の上に積層されたＳＯＩ（Ｓｉｌｉｃｏｎ　Ｏｎ　Ｉｎｓｕｌａｔｏｒ）層１１３を有するＳＯＩ基板１１０から構成されている。ＳＯＩ層１１３には、Ｎ型拡散領域１１４とＰ型拡散領域１１５とが交互に形成されており、ラテラルＰＮ接合領域を含むラテラル型のダイオードを構成している。ＳＯＩ層１１３の受光領域に紫外線が照射されると、紫外線量に応じた出力信号が発生して、これにより、紫外線量を検出することができる。 As a conventional ultraviolet sensor, for example, a cross-sectional view of the ultraviolet sensor 101 disclosed in Patent Document 1 is shown in FIG. The ultraviolet sensor 101 shown in FIG. 7 is composed of a semiconductor substrate 111, an insulating oxide film 112, and an SOI substrate 110 having an SOI (Silicon On Insulator) layer 113 stacked on the oxide film 112. In the SOI layer 113, N-type diffusion regions 114 and P-type diffusion regions 115 are alternately formed to constitute a lateral type diode including a lateral PN junction region. When the light receiving region of the SOI layer 113 is irradiated with ultraviolet light, an output signal corresponding to the amount of ultraviolet light is generated, whereby the amount of ultraviolet light can be detected.
　また、ＳＯＩ基板１１０に形成されたダイオードは、広い波長領域で受光感度を有するため、ＳＯＩ層１１０に到達する光を所定以下の波長に限定する（すなわち所定以上の波長の入射光を遮蔽する）ことができるフィルタ膜１３０が配置されている。図７に示すように、従来例の紫外線センサ１０１では、ＳＯＩ層１１３の受光面側に、ＳＯＩ層１１３と所定の間隔を空けてフィルタ膜１３０が配置されている。これにより、所定範囲の波長を選択して紫外線量を検出することができる。 In addition, since the diode formed on the SOI substrate 110 has light receiving sensitivity in a wide wavelength region, the light reaching the SOI layer 110 is limited to a wavelength equal to or less than a predetermined wavelength (that is, shielding incident light of a predetermined wavelength or more) A filter membrane 130 capable of As shown in FIG. 7, in the ultraviolet sensor 101 of the conventional example, the filter film 130 is disposed on the light receiving surface side of the SOI layer 113 at a predetermined distance from the SOI layer 113. Thereby, the wavelength of a predetermined range can be selected and the amount of ultraviolet rays can be detected.
特開２００８－２５８０００号公報JP 2008-258000 A
　しかしながら、フィルタ膜１３０とＳＯＩ層１１３との間に所定の間隔を設けるために、半導体基板１１１の外周に、フィルタ膜１３０を支持するためのフレーム（図示しない）を形成する必要がある。フレームはＳＯＩ層１１３を囲むように設けられており、フレーム上にＳＯＩ層１１３を覆うようにフィルタ膜１３０が形成される。このフレームの高さを適切に形成することにより、ＳＯＩ層１１３とフィルタ膜１３０との間隔を形成している。 However, in order to provide a predetermined distance between the filter film 130 and the SOI layer 113, it is necessary to form a frame (not shown) for supporting the filter film 130 on the outer periphery of the semiconductor substrate 111. The frame is provided so as to surround the SOI layer 113, and the filter film 130 is formed on the frame so as to cover the SOI layer 113. By appropriately forming the height of the frame, the distance between the SOI layer 113 and the filter film 130 is formed.
　あるいは、凹型のパッケージを用意して、その内部にＳＯＩ基板１１０を収納することも可能である。凹型のパッケージの開口部付近には、フィルタ膜１３０を固定するための嵌入部が形成されて、接着剤を用いてフィルタ膜１３０を固定することができる。この場合、パッケージの高さを適切に設計して、あるいは嵌入部の位置を所定の位置に形成してＳＯＩ層１１３とフィルタ膜１３０との間隔が設けられている。 Alternatively, it is also possible to prepare a recessed package and store the SOI substrate 110 therein. An insertion portion for fixing the filter film 130 is formed in the vicinity of the opening of the concave package, and the filter film 130 can be fixed using an adhesive. In this case, the space between the SOI layer 113 and the filter film 130 is provided by appropriately designing the height of the package or forming the position of the insertion portion at a predetermined position.
　従来の紫外線センサ１０１においては、このようなフレームあるいはパッケージを用意してＳＯＩ層１１３とフィルタ膜１３０との間隔を設ける必要があるため、紫外線センサ１０１の小型化、薄型化が困難であった。さらに、フレームを形成する工程や、パッケージを用意してフィルタ膜１３０を接着する工程が必要であることから、製造コストの低減が困難であった。 In the conventional ultraviolet sensor 101, since it is necessary to prepare such a frame or package and provide a space between the SOI layer 113 and the filter film 130, it is difficult to miniaturize and thin the ultraviolet sensor 101. Furthermore, since the process of forming the frame and the process of preparing the package and adhering the filter film 130 are required, it is difficult to reduce the manufacturing cost.
　また、フィルタ膜１３０は通常、良好な光透過性を有する石英基板（図示しない）上に積層されて、フレーム又はパッケージ等に接着される。この石英基板は、製造工程における破損や割れを防止するとともに落下試験等における信頼性を確保できるように、十分な強度を有することが求められている。石英基板は例えば０．３ｍｍ～０．５ｍｍ程度の厚みで形成されており、紫外線センサ１０１の薄型化の阻害要因となっていた。また、石英基板は高価な部材であり、コストダウンの妨げとなっていた。 Also, the filter film 130 is generally laminated on a quartz substrate (not shown) having good light transmittance and adhered to a frame or a package. The quartz substrate is required to have sufficient strength so as to prevent breakage and cracking in the manufacturing process and to ensure reliability in a drop test and the like. The quartz substrate is formed to have a thickness of, for example, about 0.3 mm to 0.5 mm, which has been an obstacle to reducing the thickness of the ultraviolet sensor 101. Further, the quartz substrate is an expensive member, which has been an obstacle to cost reduction.
　本発明は、上記課題を解決し、薄型化を実現できるとともに製造コストの低減が可能な紫外線センサを提供することを目的とする。 An object of the present invention is to solve the above-mentioned problems, and to provide an ultraviolet sensor which can realize thinning and reduce the manufacturing cost.
　本発明の紫外線センサは、紫外線を含む光を受光して電流を発生させる受光素子と、前記受光素子の受光面側に積層された保護膜と、ＵＶ－Ａ波とＵＶ－Ｂ波とを透過するフィルタ膜とを有し、前記フィルタ膜が前記保護膜の表面に積層されていることを特徴とする。 The ultraviolet sensor according to the present invention transmits a light receiving element that generates light by receiving light containing ultraviolet light, a protective film laminated on the light receiving surface side of the light receiving element, and UV-A waves and UV-B waves. And the filter film is laminated on the surface of the protective film.
　これによれば、保護膜との間に間隔を設けることなくフィルタ膜を形成できるとともに、フィルタ膜の支持基板として用いられていた石英基板等を省く事が可能であることから、紫外線センサの薄型化が実現できる。 According to this, it is possible to form the filter film without providing a space between it and the protective film, and it is possible to omit the quartz substrate and the like used as a support substrate for the filter film. Can be realized.
　また、フィルタ膜を支持するためのフレームを形成してフィルタ膜を接着する工程、あるいはパッケージを用意して組み立てる工程等が不要となることから、製造コストの低減を図ることができる。さらに、高価な石英基板を用いることなくフィルタ膜を形成することが可能であるため、製造コストをさらに低減することが可能である。 In addition, the process of forming the frame for supporting the filter membrane and adhering the filter membrane, or the process of preparing and assembling the package, etc. is not necessary, so that the manufacturing cost can be reduced. Furthermore, since the filter film can be formed without using an expensive quartz substrate, the manufacturing cost can be further reduced.
　したがって、本発明によれば、薄型化を実現できるとともに製造コストの低減が可能な紫外線センサを提供することができる。 Therefore, according to the present invention, it is possible to provide an ultraviolet sensor which can be made thin and which can reduce the manufacturing cost.
　本発明の紫外線センサにおいて、前記保護膜は、屈折率が１．３５～１．４８の低屈折材料により形成されており、前記保護膜の光学膜厚が０．２４６×λ×（２×ｎ－０．３）～０．２４６×λ×（２×ｎ＋０．３）（λ＝３１１ｎｍ、ｎは１以上の自然数）であることが好適である。こうすれば、フィルタ膜と保護膜とで発生するＵＶ－Ａ波（波長約３２０ｎｍ～４００ｎｍの紫外線）及びＵＶ－Ｂ波（波長約２８０ｎｍ～３２０ｎｍの紫外線）の反射率の増大を抑制することが可能である。したがって、ＵＶ－Ａ波及びＵＶ－Ｂ波はフィルタ膜を透過して紫外線センサの受光面に受光されるため、良好な受光感度を有する紫外線センサを提供することができる。 In the ultraviolet sensor according to the present invention, the protective film is formed of a low refractive material having a refractive index of 1.35 to 1.48, and an optical film thickness of the protective film is 0.246 × λ × (2 × n It is preferable that −0.3) to 0.246 × λ × (2 × n + 0.3) (λ = 311 nm, n is a natural number of 1 or more). In this way, it is possible to suppress the increase in the reflectance of the UV-A wave (ultraviolet light of wavelength about 320 nm to 400 nm) and the UV-B wave (ultraviolet light of wavelength about 280 nm to 320 nm) generated by the filter film and the protective film. It is possible. Therefore, since the UV-A wave and the UV-B wave are transmitted through the filter film and received by the light receiving surface of the ultraviolet sensor, it is possible to provide the ultraviolet sensor having a good light receiving sensitivity.
　本発明の紫外線センサにおいて、前記保護膜は、９８ｎｍ～１１７ｎｍ、または１９４ｎｍ～２１７ｎｍ、または２９１ｎｍ～３１４ｎｍの膜厚で形成されていることが好ましい。こうすれば、フィルタ膜と保護膜とで発生するＵＶ－Ｂ波の反射率を４５％以下に抑制することができ、また、ＵＶ－Ａ波の反射率を５０％以下に抑制することができるため、ＵＶ－Ａ波及びＵＶ－Ｂ波についてより良好な受光感度を有する紫外線センサを提供することができる。また、ＵＶ－Ｂ波とＵＶ－Ａ波の反射率の差を１０％以下に抑えることができるため、ＵＶ－Ａ波とＵＶ－Ｂ波に対する受光感度のばらつきを抑制することが可能となる。 In the UV sensor of the present invention, the protective film is preferably formed to have a film thickness of 98 nm to 117 nm, 194 nm to 217 nm, or 291 nm to 314 nm. In this way, the reflectance of UV-B waves generated by the filter film and the protective film can be suppressed to 45% or less, and the reflectance of UV-A waves can be suppressed to 50% or less Therefore, it is possible to provide an ultraviolet sensor having better light receiving sensitivity for UV-A waves and UV-B waves. In addition, since the difference between the reflectances of the UV-B wave and the UV-A wave can be suppressed to 10% or less, it is possible to suppress the variation in light receiving sensitivity to the UV-A wave and the UV-B wave.
　前記保護膜は酸化シリコンを用いて形成されていることが好ましい。こうすれば、ＳＯＩ層を良好に保護することが可能であり、外部の環境（湿度、温度等）や機械的損傷等による特性劣化を防ぐことができる。また、ＵＶ－Ａ波及びＵＶ－Ｂ波の波長領域における光透過率が高く、屈折率が低い材料であるため紫外線センサの受光感度を向上させることが可能となる。 The protective film is preferably formed using silicon oxide. By so doing, the SOI layer can be well protected, and characteristic deterioration due to external environment (humidity, temperature, etc.) or mechanical damage can be prevented. In addition, since the light transmittance in the wavelength range of UV-A waves and UV-B waves is high and the refractive index is low, it is possible to improve the light reception sensitivity of the ultraviolet sensor.
　前記フィルタ膜は、低屈折率材料（屈折率１．３～１．５）と高屈折率材料（屈折率１．９～２．２）とが交互に積層された多層膜で構成されていることが好適である。こうすれば、ＵＶ－Ａ波及びＵＶ－Ｂ波を透過させて、ＵＶ－Ｃ波（波長約２８０ｎｍ以下の紫外線）及び可視光（波長約４００ｎｍ以上の光）を遮蔽する良好なフィルタ特性を得ることができる。 The filter film is composed of a multilayer film in which low refractive index materials (refractive index 1.3 to 1.5) and high refractive index materials (refractive index 1.9 to 2.2) are alternately laminated. Is preferred. In this way, UV-A waves and UV-B waves are transmitted, and good filter characteristics for blocking UV-C waves (ultraviolet light having a wavelength of about 280 nm or less) and visible light (light having a wavelength of about 400 nm or more) are obtained. be able to.
　本発明の紫外線センサにおいて、前記受光素子は、半導体基板と、前記半導体基板上に形成された酸化層と、前記酸化層上に形成されたＳＯＩ層とを有し構成されていることが好適である。こうすれば、ＵＶ－Ａ波及びＵＶ－Ｂ波に対して良好な受光感度を有し、小型化、及び薄型化が可能な紫外線センサを提供することができる。 In the ultraviolet sensor according to the present invention, the light receiving element preferably includes a semiconductor substrate, an oxide layer formed on the semiconductor substrate, and an SOI layer formed on the oxide layer. is there. In this way, it is possible to provide an ultraviolet sensor that has good light receiving sensitivity to UV-A waves and UV-B waves, and that can be miniaturized and thinned.
　本発明によれば、保護膜との間に間隔を設けることなくフィルタ膜を形成できるとともに、フィルタ膜の支持基板として用いられていた石英基板等を省く事が可能であることから、紫外線センサの薄型化が実現できる。 According to the present invention, the filter film can be formed without providing a space between the protective film, and the quartz substrate etc. used as a support substrate for the filter film can be omitted. Thinning can be realized.
　また、フィルタ膜を支持するためのフレームを形成してフィルタ膜を接着する工程、あるいはパッケージを用意して組み立てる工程等が不要となることから、製造コストの低減を図ることができる。さらに、高価な石英基板を用いることなくフィルタ膜を形成することが可能であるため、製造コストをさらに低減することが可能である。 In addition, the process of forming the frame for supporting the filter membrane and adhering the filter membrane, or the process of preparing and assembling the package, etc. is not necessary, so that the manufacturing cost can be reduced. Furthermore, since the filter film can be formed without using an expensive quartz substrate, the manufacturing cost can be further reduced.
　したがって、本発明の紫外線センサによれば、薄型化を実現できるとともに製造コストの低減が可能な紫外線センサを提供することができる。 Therefore, according to the ultraviolet ray sensor of the present invention, it is possible to provide an ultraviolet ray sensor which can realize a reduction in thickness and can reduce the manufacturing cost.
本実施形態における紫外線センサの模式平面図である。It is a model top view of the ultraviolet sensor in this embodiment. 図１のＩＩ－ＩＩ線に沿って切断した紫外線センサの模式断面図である。FIG. 2 is a schematic cross-sectional view of the ultraviolet sensor cut along the line II-II in FIG. 紫外線センサにおけるフィルタ膜の構成を示す模式断面図である。It is a schematic cross section which shows the structure of the filter film in an ultraviolet sensor. フィルタ膜単体、及び保護膜表面にフィルタ膜を積層したときの、反射率と波長の関係を示すグラフである。It is a graph which shows the relationship of reflectance and wavelength when a filter film | membrane is laminated | stacked on the filter film single-piece | unit and protective film surface. （ａ）ＵＶ－Ａ波の平均反射率及びＵＶ－Ｂ波の平均反射率と保護膜の膜厚との関係を示すグラフ、（ｂ）ＵＶ－Ａ波の平均反射率とＵＶ－Ｂ波の平均反射率との差を示すグラフである。(A) A graph showing the relationship between the average reflectance of UV-A waves and the average reflectance of UV-B waves and the film thickness of the protective film, (b) Average reflectance of UV-A waves and UV-B waves It is a graph which shows a difference with average reflectance. 異なる厚さの保護膜表面にフィルタ膜を積層したときの、反射率と波長の関係を示すグラフである。It is a graph which shows the relation of reflectance and wavelength when a filter film is laminated on the protective film surface of different thickness. 従来例の紫外線センサを示す断面図である。It is sectional drawing which shows the ultraviolet-ray sensor of a prior art example.
　図１には、本実施形態における紫外線センサ１の模式平面図を示す。図２には、図１のＩＩ－ＩＩ線に沿って切断した紫外線センサ１の模式断面図を示す。なお、図１は保護膜２０及びフィルタ膜３０を省略して示している。図２に示すように、本実施形態の紫外線センサ１は、半導体基板１１、半導体基板１１上に形成された酸化膜１２、酸化膜１２上に形成されたＳＯＩ層１３、ＳＯＩ層１３に積層された保護膜２０、及びＵＶ－Ａ波とＵＶ－Ｂ波とを透過するフィルタ膜３０とを有し構成されている。半導体基板１１、酸化膜１２、及びＳＯＩ層１３からＳＯＩ基板１０が構成されており、半導体基板１１とＳＯＩ層１３とは、酸化膜１２によって絶縁されている。 In FIG. 1, the model top view of the ultraviolet-ray sensor 1 in this embodiment is shown. FIG. 2 shows a schematic cross-sectional view of the ultraviolet sensor 1 cut along the line II-II in FIG. In FIG. 1, the protective film 20 and the filter film 30 are omitted. As shown in FIG. 2, the ultraviolet sensor 1 of the present embodiment is stacked on a semiconductor substrate 11, an oxide film 12 formed on the semiconductor substrate 11, an SOI layer 13 formed on the oxide film 12, and an SOI layer 13. And a filter film 30 which transmits UV-A waves and UV-B waves. The SOI substrate 10 is composed of the semiconductor substrate 11, the oxide film 12 and the SOI layer 13, and the semiconductor substrate 11 and the SOI layer 13 are insulated by the oxide film 12.
　図１に示すように、ＳＯＩ層１３には、Ｅ字状に形成されたＮ＋領域１４とπ字状に形成されたＰ＋領域１５とが対向するように形成されている。Ｎ＋領域１４及びＰ＋領域１５には、それぞれＮ＋領域１４の櫛歯部１４ａとＰ＋領域１５の櫛歯部１５ａとが形成されており、櫛歯部１４ａと櫛歯部１５ａとは間隔を空けてかみ合わされるように配置されている。Ｎ＋領域１４は、ＳＯＩ層１３にリン（Ｐ）や砒素（Ａｓ）等のＮ型不純物を比較的高濃度に拡散させて形成された高濃度Ｎ型拡散領域である。また、Ｐ＋領域１５はボロン（Ｂ）等のＰ型不純物を比較的高濃度に拡散させて形成された高濃度Ｐ型拡散領域である。そして、対向するＮ＋領域１４とＰ＋領域１５との間には、Ｐ型不純物が比較的低濃度に拡散されたＰ－領域１６が形成されている。Ｎ＋領域１４、Ｐ＋領域１５及びＰ－領域１６によってラテラルＰＮ接合が形成されて、ラテラル型のフォトダイオードが形成されている。 As shown in FIG. 1, in the SOI layer 13, the E + -shaped N + region 14 and the π-shaped P + region 15 are formed to face each other. In the N + region 14 and the P + region 15, the comb teeth 14a of the N + region 14 and the comb teeth 15a of the P + region 15 are formed, respectively, and the comb teeth 14a and the comb teeth 15a are spaced apart from each other. It is arranged to be engaged. The N + region 14 is a high concentration N type diffusion region formed by diffusing an N type impurity such as phosphorus (P) or arsenic (As) at a relatively high concentration in the SOI layer 13. The P + region 15 is a high concentration P type diffusion region formed by diffusing a P type impurity such as boron (B) to a relatively high concentration. A P− region 16 in which a P-type impurity is diffused to a relatively low concentration is formed between the opposing N + region 14 and the P + region 15. A lateral PN junction is formed by the N + region 14, the P + region 15 and the P − region 16 to form a lateral photodiode.
　Ｐ－領域１６には空乏層（図示しない）が形成されており、空乏層近傍に紫外線を含む光が照射されると、電子－正孔対が発生する。図１及び図２では省略しているが、Ｎ＋領域１４及びＰ＋領域１５には、アルミニウム（Ａｌ）、チタン（Ｔｉ）、タングステン（Ｗ）等の導電材料により形成された配線電極層（図示しない）が接続されている。配線電極層は、保護膜２０及びフィルタ膜３０に形成されたコンタクトホール（図示しない）を通して外部へと引き出されており、受光した光によって発生した出力電流を取り出すことができる。なお、受光面積を確保するために、配線電極層及びコンタクトホールは受光領域であるＰ－領域１６と重ならないように形成されている。 A depletion layer (not shown) is formed in the P− region 16, and when light including ultraviolet light is irradiated in the vicinity of the depletion layer, electron-hole pairs are generated. Although not shown in FIGS. 1 and 2, wiring electrode layers (not shown) formed of conductive materials such as aluminum (Al), titanium (Ti), tungsten (W), etc. in N + region 14 and P + region 15 ) Is connected. The wiring electrode layer is drawn to the outside through contact holes (not shown) formed in the protective film 20 and the filter film 30, and an output current generated by the received light can be extracted. In order to secure the light receiving area, the wiring electrode layer and the contact hole are formed so as not to overlap with the P− region 16 which is the light receiving region.
　なお、紫外線センサ１は図１に示すような構成に限定されるものではなく、Ｎ＋領域１４の櫛歯部１４ａ及びＰ＋領域１５の櫛歯部１５ａを増やした構成や、櫛歯部を設けずにＩ字状に形成したＮ＋領域１４とＰ＋領域１５とを対向させた構成であっても良い。また、ＳＯＩ基板１０は、その構成や製造方法について特に限定されるものではない。ＳＯＩ基板１０は、例えば貼り合わせ法やＳＩＭＯＸ（Ｓｉｌｉｃｏｎ　Ｉｍｐｌａｎｔｅｄ　Ｏｘｉｄｅ）法等によって作製したものを用いることができる。 The ultraviolet sensor 1 is not limited to the configuration as shown in FIG. 1, and the configuration in which the comb teeth 14a of the N + region 14 and the comb teeth 15a of the P + region 15 are increased, or the comb teeth are not provided. Alternatively, the N + region 14 and the P + region 15 formed in an I shape may be opposed to each other. Further, the SOI substrate 10 is not particularly limited in its configuration or manufacturing method. As the SOI substrate 10, for example, one manufactured by a bonding method or a SIMOX (Silicon Implanted Oxide) method can be used.
　図２に示すように、ＳＯＩ層１３の受光面側には保護膜２０が形成されている。保護膜２０は、外部の環境（湿度、温度等）や製造工程における機械的損傷や化学薬品等の化学的損傷等からＳＯＩ層１３を保護するために形成されている。また、保護膜２０はＵＶ－Ａ波及びＵＶ－Ｂ波の波長領域における光透過率が高く、屈折率の低い絶縁性の材料により形成されることが好ましい。例えば酸化シリコン（ＳｉＯ2）やＮＳＧ（Ｎｏｎｄｏｐｅｄ　Ｓｉｌｉｃａ　Ｇｌａｓｓ）等の絶縁材料を用いることができ、本実施形態では酸化シリコンを用いて形成されている。 As shown in FIG. 2, a protective film 20 is formed on the light receiving surface side of the SOI layer 13. The protective film 20 is formed to protect the SOI layer 13 from external environment (humidity, temperature, etc.), mechanical damage in the manufacturing process, chemical damage such as chemicals, and the like. The protective film 20 is preferably formed of an insulating material having a high light transmittance in the wavelength range of UV-A waves and UV-B waves and a low refractive index. For example, an insulating material such as silicon oxide (SiO 2 ) or NSG (Nondoped Silica Glass) can be used, and in this embodiment, it is formed using silicon oxide.
　なお、紫外線とは、可視光よりも短い波長を有する光であり、波長１００ｎｍ～４００ｎｍの光を指す。また、ＵＶ（Ｕｌｔｒａｖｉｏｌｅｔ）は紫外線と同義である。紫外線波長領域のうち、３２０ｎｍ～４００ｎｍの領域は長波長紫外線（ＵＶ－Ａ波）、２８０ｎｍ～３２０ｎｍの領域は中波長紫外線（ＵＶ－Ｂ波）、１００ｎｍ～２８０ｎｍの領域は短波長紫外線（ＵＶ－Ｃ波）と区分されている。これらの波長領域によって人体や環境に与える影響が異なっている。ＵＶ－Ａ波は皮膚を黒化させ真皮に達して老化の原因になり、また、ＵＶ－Ａ波に比べて強いエネルギーをもつＵＶ－Ｂ波は、皮膚を炎症させ皮膚ガンを誘発する虞がある。ＵＶ－Ｃ波は、ＵＶ－Ａ波及びＵＶ－Ｂ波よりも強いエネルギーを有しており、強い殺菌作用があるとされているが、太陽光のＵＶ－Ｃ波のほとんどがオゾン層で吸収されて地上に達することはない。したがって、紫外線センサ１は、ＵＶ－Ａ波及びＵＶ－Ｂ波について良好な受光感度を有し、かつ、それ以外の波長の光（ＵＶ－Ｃ波、及び可視光以上の波長領域）に対しては検出しないことが求められる。 Ultraviolet light refers to light having a wavelength shorter than visible light, and refers to light with a wavelength of 100 nm to 400 nm. Moreover, UV (Ultraviolet) is synonymous with an ultraviolet-ray. In the ultraviolet wavelength range, the long wavelength ultraviolet light (UV-A wave) in the region of 320 nm to 400 nm, the intermediate wavelength ultraviolet light (UV-B wave) in the region of 280 nm to 320 nm, the short wavelength ultraviolet light (UV- C wave). These wavelength regions have different influences on the human body and the environment. UV-A waves darken the skin and reach the dermis and cause aging. Also, UV-B waves, which have stronger energy than UV-A waves, may cause skin irritation and induce skin cancer. is there. UV-C waves have stronger energy than UV-A waves and UV-B waves, and are considered to have strong bactericidal action, but most of the UV-C waves of sunlight are absorbed by the ozone layer It has never been reached the earth. Therefore, the ultraviolet sensor 1 has good light receiving sensitivity for UV-A waves and UV-B waves, and for light of other wavelengths (UV-C waves and wavelength regions of visible light or more) Is required not to be detected.
　本実施形態において、ＳＯＩ層の厚さは２００ｎｍ～４００ｎｍ程度に形成されている。この場合、ＳＯＩ基板１０に形成されたラテラル型フォトダイオードは、紫外線及び可視光を含む広い波長領域について受光感度を有する。そのため、ＵＶ－Ａ波及びＵＶ－Ｂ波を透過して、ＵＶ－Ｃ波及び可視光については遮蔽可能なフィルタ特性を有するフィルタ膜３０を保護膜２０の表面に積層している。これにより、紫外線センサ１は、フィルタ膜３０を透過してラテラル型フォトダイオードの受光領域に受光されたＵＶ－Ａ波及びＵＶ－Ｂ波を検出することが可能となる。 In the present embodiment, the thickness of the SOI layer is formed to be approximately 200 nm to 400 nm. In this case, the lateral photodiode formed on the SOI substrate 10 has light receiving sensitivity over a wide wavelength range including ultraviolet light and visible light. Therefore, the UV-A wave and the UV-B wave are transmitted, and the filter film 30 having a filter characteristic capable of shielding the UV-C wave and the visible light is laminated on the surface of the protective film 20. Thus, the ultraviolet sensor 1 can detect the UV-A wave and the UV-B wave transmitted through the filter film 30 and received in the light receiving area of the lateral photodiode.
　図２に示すように、フィルタ膜３０は保護膜２０の表面に積層されている。これにより、保護膜２０との間に間隔を設けることなくフィルタ膜３０を形成できる。また、従来の紫外線センサ１０１においてフィルタ膜１３０の支持基板として用いられていた石英基板を省く事が可能である。したがって、紫外線センサ１の薄型化が実現できる。 As shown in FIG. 2, the filter film 30 is laminated on the surface of the protective film 20. Thus, the filter film 30 can be formed without providing a space between the filter film 30 and the protective film 20. In addition, it is possible to omit the quartz substrate used as a support substrate of the filter film 130 in the conventional ultraviolet sensor 101. Therefore, thinning of the ultraviolet sensor 1 can be realized.
　また、フィルタ膜３０を支持するためのフレームを形成してフィルタを接着する工程や、パッケージを用意して組み立てる工程が不要であることから、製造コストの低減を図ることができる。さらに、高価な石英基板を用いることなくフィルタ膜３０を形成することが可能であるため、製造コストをさらに低減することが可能である。 Moreover, since the process of forming the frame for supporting the filter film 30 and adhering the filter and the process of preparing and assembling the package are unnecessary, the manufacturing cost can be reduced. Furthermore, since the filter film 30 can be formed without using an expensive quartz substrate, the manufacturing cost can be further reduced.
　図３には、本実施形態におけるフィルタ膜３０の模式断面図を示す。図３に示すように、フィルタ膜３０は、低屈折率材料（屈折率１．３～１．５）３１と高屈折率材料（屈折率１．９～２．２）３２とが交互に積層された多層膜で構成されている。低屈折率材料３１として、フッ化マグネシウム（ＭｇＦ2）、酸化シリコン（ＳｉＯ2）や、酸化シリコン（ＳｉＯ2）と酸化アルミニウム（Ａｌ2Ｏ3）の混合材等を用いることができる。また、高屈折率材料３２には、酸化タンタル（Ｔａ2Ｏ5）、酸化ジルコニウム（ＺｒＯ2）、酸化チタン（ＴｉＯ2）、酸化ランタン（Ｌａ2Ｏ3）のいずれか一つまたは各材料の混合材等を用いる事ができる。フィルタ膜３０は、保護膜２０側に高屈折率材料３２が配置されて、フィルタ膜３０の受光面側に低屈折率材料３１が配置されるように構成されている。 FIG. 3 shows a schematic cross-sectional view of the filter film 30 in the present embodiment. As shown in FIG. 3, in the filter film 30, low refractive index material (refractive index 1.3 to 1.5) 31 and high refractive index material (refractive index 1.9 to 2.2) 32 are alternately stacked. It is composed of a multilayer film. As the low refractive index material 31, magnesium fluoride (MgF 2 ), silicon oxide (SiO 2 ), a mixed material of silicon oxide (SiO 2 ) and aluminum oxide (Al 2 O 3 ), or the like can be used. The high refractive index material 32 may be tantalum oxide (Ta 2 O 5 ), zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), lanthanum oxide (La 2 O 3 ), or any one of the respective materials. A mixed material etc. can be used. The filter film 30 is configured such that the high refractive index material 32 is disposed on the protective film 20 side, and the low refractive index material 31 is disposed on the light receiving surface side of the filter film 30.
　低屈折率材料３１及び高屈折率材料３２は、蒸着法などの薄膜法により形成することができ、交互に２０層以上積層された多層膜となっている。本実施形態においてフィルタ膜３０は２４層積層された構成であり、その合計厚みは約２μｍである。 The low refractive index material 31 and the high refractive index material 32 can be formed by a thin film method such as a vapor deposition method, and form a multilayer film in which 20 or more layers are alternately stacked. In the present embodiment, the filter film 30 has a configuration in which 24 layers are stacked, and the total thickness thereof is about 2 μm.
　図４には、本実施形態におけるフィルタ膜３０単体の反射率と光の波長との関係、及びフィルタ膜３０を保護膜２０上に積層したときの反射率と光の波長の関係を示す。このときの保護膜２０の膜厚は約３４４ｎｍに形成されている。図４に示すように、フィルタ膜３０単体の反射率は、ＵＶ－Ａ波及びＵＶ－Ｂ波の波長領域（２８０ｎｍ～４００ｎｍ）において約１０％程度であり、ＵＶ－Ｃ波（２８０ｎｍ以下）及び可視光領域（４００ｎｍ以上）では９０％以上の反射率を示している。すなわち、フィルタ膜３０はＵＶ－Ａ波及びＵＶ－Ｂ波のみを透過する良好なフィルタ特性を有しているといえる。また、波長７５０ｎｍ以上の近赤外領域でフィルタ膜３０の反射率が低下しているが、ＳＯＩ層１３の厚さは上述のとおり２００ｎｍ～４００ｎｍ程度に薄く形成されていることにより、近赤外領域の波長の光はＳＯＩ層１３のフォトダイオードに吸収されずに透過してしまう。このため、フィルタ膜３０を透過した近赤外領域の光が検出されることはなく、紫外線センサ１の検出感度に影響を及ぼすことはない。したがって、紫外線センサ１はＵＶ－Ａ波及びＵＶ－Ｂ波に対して良好な受光感度を有することが可能となる。 FIG. 4 shows the relationship between the reflectance of the filter film 30 alone and the wavelength of light in the present embodiment, and the relationship between the reflectance and the wavelength of light when the filter film 30 is stacked on the protective film 20. The film thickness of the protective film 20 at this time is formed to be about 344 nm. As shown in FIG. 4, the reflectance of the filter film 30 alone is about 10% in the wavelength range (280 nm to 400 nm) of the UV-A wave and the UV-B wave, and the UV-C wave (280 nm or less) and In the visible light region (400 nm or more), the reflectance is 90% or more. That is, it can be said that the filter film 30 has a good filter characteristic of transmitting only the UV-A wave and the UV-B wave. In addition, although the reflectance of the filter film 30 is lowered in the near infrared region of a wavelength of 750 nm or more, the thickness of the SOI layer 13 is thin as described above, so that the near infrared region Light of a wavelength in the region is transmitted without being absorbed by the photodiode of the SOI layer 13. For this reason, light in the near infrared region transmitted through the filter film 30 is not detected, and the detection sensitivity of the ultraviolet sensor 1 is not affected. Therefore, the ultraviolet sensor 1 can have good light receiving sensitivity to UV-A waves and UV-B waves.
　しかし、保護膜２０の表面にフィルタ膜３０を積層した場合、保護膜２０とフィルタ膜３０との界面の反射の影響が付加されることにより反射率が変化してしまい、図４に示すように、ＵＶ－Ｂ波（２８０ｎｍ～３２０ｎｍ）の反射率は５０％～６５％程度まで増大し、ＵＶ－Ａ波（３２０ｎｍ～４００ｎｍ）での反射率は約２２％～５０％となり、波長依存性が増大する。また、ＵＶ－Ａ波の反射率とＵＶ－Ｂ波の反射率との差も大きくなっている。 However, when the filter film 30 is laminated on the surface of the protective film 20, the reflectance is changed by the influence of the reflection of the interface between the protective film 20 and the filter film 30, as shown in FIG. The reflectance of UV-B waves (280 nm to 320 nm) increases to about 50% to 65%, and the reflectance of UV-A waves (320 nm to 400 nm) is about 22% to 50%, and the wavelength dependence is Increase. In addition, the difference between the reflectance of the UV-A wave and the reflectance of the UV-B wave is also large.
　すなわち、入射したＵＶ－Ｂ波の多くがフィルタ膜３０及び保護膜２０で反射されてフォトダイオードの受光領域に受光されず、紫外線センサ１の検出感度が低下してしまうことになる。ＵＶ－Ｂ波はＵＶ－Ａ波に比べてより強いエネルギーを持つことから、ＵＶ－Ｂ波の検出感度が低下することは好ましくない。また、図４に示すようにＵＶ－Ａ波とＵＶ－Ｂ波との反射率の差が大きい場合、あるいは反射率の波長依存性が大きい場合、入射する光の波長により検出感度のばらつきが大きくなり紫外線センサ１の検出精度が低下してしまうおそれがある。 That is, most of the incident UV-B waves are reflected by the filter film 30 and the protective film 20 and are not received by the light receiving area of the photodiode, and the detection sensitivity of the ultraviolet sensor 1 is lowered. Since the UV-B wave has stronger energy than the UV-A wave, it is not preferable that the detection sensitivity of the UV-B wave is lowered. Also, as shown in FIG. 4, when the difference in reflectance between UV-A and UV-B waves is large, or when the wavelength dependency of the reflectance is large, the variation in detection sensitivity is large depending on the wavelength of incident light. Therefore, the detection accuracy of the ultraviolet ray sensor 1 may be reduced.
　このような課題を解決するため、フィルタ膜３０の膜構成を最適化する方法を試みたが、上述のように複数の材料を用いた多層膜であるため、ＵＶ－Ｂ波の反射率の増大を抑制し、かつ、ＵＶ－Ａ波及びＵＶ－Ｂ波の波長領域における反射特性をフラット化することは非常に困難であった。そのため、フィルタ膜３０と保護膜２０との間隔を設けずにフィルタ膜３０を積層して、良好な受光感度を実現することは困難であった。 In order to solve such problems, an attempt was made to optimize the film configuration of the filter film 30, but as described above, since it is a multilayer film using a plurality of materials, the reflectance of UV-B waves is increased It has been very difficult to suppress and flatten the reflection characteristics in the wavelength range of UV-A and UV-B waves. Therefore, it is difficult to achieve good light receiving sensitivity by laminating the filter film 30 without providing the space between the filter film 30 and the protective film 20.
　図５（ａ）には、ＳＯＩ基板１０に保護膜２０及びフィルタ膜３０を積層した紫外線センサ１について、ＵＶ－Ａ波及びＵＶ－Ｂ波の平均反射率と保護膜２０の膜厚との関係を示す。図５（ａ）に示すように、保護膜２０の膜厚を約７５μｍ～３７０ｎｍまで変化させると、ＵＶ－Ａ波及びＵＶ－Ｂ波の反射率が周期性を持って変化する。ＵＶ－Ａ波は、約３３％～５１％の範囲で反射率が周期的に変化しており、ＵＶ－Ｂ波は約３８％～６０％の範囲で反射率が変化している。ＵＶ－Ｂ波の平均反射率は、光学波長０．２４６×λ×２×ｎ（λ＝３１１ｎｍ、ｎは１以上の自然数）で最小値を示すような周期性を有して変化していることが示されている。 FIG. 5A shows the relationship between the average reflectance of the UV-A wave and the UV-B wave and the film thickness of the protective film 20 for the ultraviolet sensor 1 in which the protective film 20 and the filter film 30 are stacked on the SOI substrate 10. Indicates As shown in FIG. 5A, when the film thickness of the protective film 20 is changed to about 75 μm to 370 nm, the reflectances of the UV-A wave and the UV-B wave change with periodicity. The reflectance of UV-A waves changes periodically in the range of about 33% to 51%, and the reflectance of UV-B waves changes in the range of about 38% to 60%. The average reflectance of the UV-B wave changes with periodicity to show the minimum value at the optical wavelength 0.246 × λ × 2 × n (λ = 311 nm, n is a natural number of 1 or more) It is shown.
　また、図５（ｂ）には、図５（ａ）に示したＵＶ－Ａ波の平均反射率とＵＶ－Ｂ波の平均反射率との差を示したグラフである。図５（ｂ）は、（ＵＶ－Ｂ波の平均反射率）－（ＵＶ－Ａ波の平均反射率）により算出した値を示しており、グラフ中の平均反射率の差が正の領域は、ＵＶ－Ｂ波の反射率がＵＶ－Ａ波よりも大きいことを示す。図５（ｂ）に示すように、平均反射率の差は保護膜２０の膜厚により大きく変動する。上述のように、紫外線センサ１において、より強いエネルギーを有するＵＶ－Ｂ波について良好な検出感度を有するとともに、ＵＶ－Ａ波とＵＶ－Ｂ波との検出感度のばらつきが小さいことが求められている。したがって図５（ａ）に示す、ＵＶ－Ｂ波の平均反射率が低く、かつ図５（ｂ）に示す平均反射率の差が０に近いことが好ましい。なお、図５（ａ）及び図５（ｂ）において、保護膜２０の厚さは種々に変化させているが、フィルタ膜３０の膜厚、構成は変えずに、図３及び図４に示した構成、フィルタ特性を有するものを用いている。 Further, FIG. 5 (b) is a graph showing the difference between the average reflectance of the UV-A wave and the average reflectance of the UV-B wave shown in FIG. 5 (a). FIG. 5 (b) shows the value calculated by (average reflectance of UV-B waves)-(average reflectance of UV-A waves), and in the region where the difference in average reflectance in the graph is positive, And UV-B waves are greater than UV-A waves. As shown in FIG. 5 (b), the difference in average reflectance largely fluctuates with the film thickness of the protective film 20. As described above, the ultraviolet sensor 1 is required to have good detection sensitivity for UV-B waves having stronger energy and to have small variation in detection sensitivity between UV-A waves and UV-B waves. There is. Therefore, it is preferable that the average reflectance of the UV-B wave shown in FIG. 5A is low and the difference in the average reflectance shown in FIG. 5B is close to zero. Although the thickness of the protective film 20 is changed variously in FIGS. 5A and 5B, the thickness and the configuration of the filter film 30 are not changed, and they are shown in FIGS. 3 and 4. It has a configuration and filter characteristics.
　本実施形態の紫外線センサ１において、保護膜２０は、屈折率が約１．３５～１．４８の低屈折材料である酸化シリコン（ＳｉＯ2）から形成されている。このとき、保護膜２０の光学膜厚が０．２４６×λ×（２×ｎ－０．３）～０．２４６×λ×（２×ｎ＋０．３）（λ＝３１１ｎｍ、ｎは１以上の自然数）であることが好適である。こうすれば、フィルタ膜３０と保護膜２０とで発生するＵＶ－Ａ波（波長約３２０ｎｍ～４００ｎｍの紫外線）及びＵＶ－Ｂ波（波長約２８０ｎｍ～３２０ｎｍの紫外線）の反射率をともに減少させることが可能である。また、この光学膜厚の範囲であれば、比較的大きい反射率を示すＵＶ－Ｂ波についても、平均反射率を５５％以下に抑制することが可能である。したがって、より多くのＵＶ－Ａ波及びＵＶ－Ｂ波が、フィルタ膜３０と保護膜２０とを透過してフォトダイオードの受光領域で受光することができるため、良好な受光感度を有する紫外線センサ１を提供することができる。 In the ultraviolet sensor 1 of the present embodiment, the protective film 20 is formed of silicon oxide (SiO 2 ) which is a low refractive material having a refractive index of about 1.35 to 1.48. At this time, the optical film thickness of the protective film 20 is 0.246 × λ × (2 × n−0.3) to 0.246 × λ × (2 × n + 0.3) (λ = 311 nm, n is 1 or more). It is preferable that it is a natural number). In this way, both the reflectance of the UV-A wave (ultraviolet light of wavelength 320 nm to 400 nm) and the UV-B wave (ultraviolet light of wavelength 280 nm to 320 nm) generated by the filter film 30 and the protective film 20 can be reduced. Is possible. In addition, within the range of the optical film thickness, it is possible to suppress the average reflectance to 55% or less even for UV-B waves showing relatively high reflectance. Therefore, more UV-A and UV-B waves can pass through the filter film 30 and the protective film 20 and can be received by the light receiving area of the photodiode, so that the ultraviolet sensor 1 having a good light receiving sensitivity Can be provided.
　また、保護膜２０の光学膜厚が０．２４６×λ×（２×ｎ－０．２）～０．２４６×λ×（２×ｎ＋０．２）（λ＝３１１ｎｍ、ｎは１以上の自然数）の範囲であることがより好ましい。この場合、ＵＶ－Ｂ波の平均反射率を５０％以下に抑制することが可能であり、紫外線センサ１の受光感度を向上させることができる。 In addition, the optical film thickness of the protective film 20 is 0.246 × λ × (2 × n−0.2) to 0.246 × λ × (2 × n + 0.2) (λ = 311 nm, n is a natural number of 1 or more) More preferably, it is in the range of In this case, the average reflectance of the UV-B wave can be suppressed to 50% or less, and the light receiving sensitivity of the ultraviolet sensor 1 can be improved.
　なお、上記の光学膜厚範囲を示す式において、λ＝３１１ｎｍは紫外線波長（２８０ｎｍ～３５０ｎｍ）の中心波長である。 In the above equation showing the optical film thickness range, λ = 311 nm is the central wavelength of the ultraviolet wavelength (280 nm to 350 nm).
　本実施形態の紫外線センサ１において、保護膜２０は、９８ｎｍ～１１７ｎｍ、または１９４ｎｍ～２１７ｎｍ、または２９１ｎｍ～３１４ｎｍの膜厚で形成されていることが、より好ましい。この膜厚範囲で保護膜２０を形成することにより、フィルタ膜３０と保護膜２０とで発生するＵＶ－Ｂ波の反射率を４５％以下に抑制することができる。したがって、ＵＶ－Ａ波に比べて強いエネルギーを有するＵＶ－Ｂ波について良好な受光感度を得るができる。また、ＵＶ－Ａ波とＵＶ－Ｂ波の反射率の差を１０％以下に抑えることができるため、ＵＶ－Ａ波とＵＶ－Ｂ波とに対する受光感度のばらつきを抑制することが可能となる。 In the ultraviolet sensor 1 of the present embodiment, the protective film 20 is more preferably formed to have a film thickness of 98 nm to 117 nm, 194 nm to 217 nm, or 291 nm to 314 nm. By forming the protective film 20 in this film thickness range, the reflectance of UV-B waves generated by the filter film 30 and the protective film 20 can be suppressed to 45% or less. Therefore, good light receiving sensitivity can be obtained for UV-B waves having stronger energy than UV-A waves. In addition, since the difference in reflectance between UV-A and UV-B waves can be suppressed to 10% or less, it is possible to suppress variations in light receiving sensitivity to UV-A waves and UV-B waves. .
　図６は、異なる厚さの保護膜２０上にフィルタ膜３０を積層したときの、反射率と波長の関係を示すグラフである。図６には、保護膜２０の光学膜厚を０．２４６×λ×２（実膜厚約１０２ｎｍ）、０．２４６×λ×４（実膜厚約２０４ｎｍ）、０．２４６×λ×４（実膜厚約３０６ｎｍ）にそれぞれ形成したときの反射率を示す。いずれも０．２４６×λ×（２×ｎ－０．３）～０．２４６×λ×（２×ｎ＋０．３）（λ＝３１１ｎｍ、ｎは１以上の自然数）の範囲の光学膜厚であり、また、９８ｎｍ～１１７ｎｍ、または１９４ｎｍ～２１７ｎｍ、または２９１ｎｍ～３１４ｎｍの膜厚範囲内である。また、比較として光学膜厚０．２４６×λ×７（実膜厚約３５７ｎｍ）の保護膜２０上にフィルタ膜３０を積層したときの反射率を示す。なお、フィルタ膜３０はいずれも、図３及び図４に示したような構成、フィルタ特性を有するものである。 FIG. 6 is a graph showing the relationship between the reflectance and the wavelength when the filter film 30 is stacked on the protective film 20 with different thicknesses. In FIG. 6, the optical film thickness of the protective film 20 is 0.246 × λ × 2 (actual film thickness about 102 nm), 0.246 × λ × 4 (actual film thickness about 204 nm), 0.246 × λ × 4 It shows the reflectance when it is formed on (the actual film thickness of about 306 nm). Any optical film thickness in the range of 0.246 × λ × (2 × n−0.3) to 0.246 × λ × (2 × n + 0.3) (λ = 311 nm, n is a natural number of 1 or more) And within the film thickness range of 98 nm to 117 nm, or 194 nm to 217 nm, or 291 nm to 314 nm. Further, as a comparison, the reflectance when the filter film 30 is laminated on the protective film 20 having an optical film thickness of 0.246 × λ × 7 (actual film thickness of about 357 nm) is shown. Each of the filter films 30 has the configuration and filter characteristics as shown in FIGS. 3 and 4.
　図６に示すように、保護膜２０の光学膜厚を０．２４６×λ×７に形成した場合には、ＵＶ－Ｂ波の波長領域で最大約６５％の反射率を示しており、また、図５（ａ）に示すようにＵＶ－Ｂ波の平均反射率は約５８％と高い値となっている。したがって、入射するＵＶ－Ｂ波の光の多くがフィルタ膜３０及び保護膜２０で反射されてしまい、フォトダイオードに受光される光量が低下し検出感度が低下する。また、ＵＶ－Ａ波の波長領域においては反射率の波長依存性が大きくなっており、反射率が約５０％から２３％まで変化していることがわかる。このような特性の場合、入射する光の波長によって検出感度のばらつきが大きくなり、正確な測定ができないおそれがある。 As shown in FIG. 6, when the optical film thickness of the protective film 20 is formed to 0.246 × λ × 7, the reflectance shows up to about 65% in the wavelength region of the UV-B wave, and As shown in FIG. 5A, the average reflectance of the UV-B wave is as high as about 58%. Therefore, most of the incident UV-B wave light is reflected by the filter film 30 and the protective film 20, the amount of light received by the photodiode decreases, and the detection sensitivity decreases. In addition, in the wavelength region of the UV-A wave, the wavelength dependency of the reflectance is large, and it can be seen that the reflectance changes from about 50% to 23%. In the case of such a characteristic, the variation in detection sensitivity becomes large depending on the wavelength of incident light, and there is a possibility that accurate measurement can not be performed.
　これに対し、光学膜厚０．２４６×λ×２、０．２４６×λ×４、及び０．２４６×λ×６に形成した場合においては、ＵＶ－Ｂ波の波長領域における最大反射率はいずれも５０％以下に抑制されており、平均反射率はそれぞれ約３８％、３９％、４２％となっている（図５（ａ）参照）。また、ＵＶ－Ａ波の波長領域における反射率は、波長の変化に対してフラットな特性を示しており、ＵＶ－Ｂ波領域における反射率との差も小さく抑えられている。 On the other hand, when the optical film thickness is 0.246 × λ × 2, 0.246 × λ × 4, and 0.246 × λ × 6, the maximum reflectance in the wavelength region of the UV-B wave is All are suppressed to 50% or less, and the average reflectances are about 38%, 39%, and 42%, respectively (see FIG. 5A). Further, the reflectance in the wavelength region of the UV-A wave shows a flat characteristic with respect to the change of the wavelength, and the difference from the reflectance in the UV-B wave region is also suppressed small.
　また、ＵＶ－Ｃ波及び可視光の波長領域においては、ほぼ９０％以上の反射率を示している。したがって、フィルタ膜３０を、上記の膜厚で形成した保護膜２０上に形成した場合には、ＵＶ－Ａ波及びＵＶ－Ｂ波を透過してＵＶ－Ｃ波及び可視光は透過しない良好なフィルタ特性を有しているといえる。 In addition, in the wavelength range of UV-C waves and visible light, a reflectance of approximately 90% or more is exhibited. Therefore, when the filter film 30 is formed on the protective film 20 formed to have the above-mentioned film thickness, it is preferable that the UV-A wave and the UV-B wave are transmitted and the UV-C wave and the visible light are not transmitted. It can be said that it has filter characteristics.
　これにより、フィルタ膜３０を保護膜２０の表面に積層して、紫外線センサ１の薄型化を実現するとともに、保護膜２０の膜厚を変化させることによって、ＵＶ－Ａ波及びＵＶ－Ｂ波について良好な受光感度を有し、また、ＵＶ－Ａ波及びＵＶ－Ｂ波に対する受光感度のばらつきを抑制することが可能な紫外線センサ１を提供することができることが示された。 As a result, the filter film 30 is laminated on the surface of the protective film 20 to realize the thinning of the ultraviolet sensor 1 and, by changing the film thickness of the protective film 20, the UV-A wave and the UV-B wave It has been shown that it is possible to provide an ultraviolet sensor 1 having good light receiving sensitivity and capable of suppressing variations in light receiving sensitivity to UV-A waves and UV-B waves.
　１　紫外線センサ
　１０　ＳＯＩ基板
　１１　半導体基板
　１２　酸化膜
　１３　ＳＯＩ層
　１４　Ｎ＋領域
　１５　Ｐ＋領域
　１６　Ｐ－領域
　２０　保護膜
　３０　フィルタ膜
　３１　低屈折率材料（屈折率１．３～１．５）
　３２　高屈折率材料（屈折率１．９～２．２） Reference Signs List 1 UV sensor 10 SOI substrate 11 semiconductor substrate 12 oxide film 13 SOI layer 14 N + region 15 P + region 16 P- region 20 protective film 30 filter film 31 low refractive index material (refractive index 1.3 to 1.5)
32 High refractive index material (refractive index 1.9 to 2.2)

Claims (6)

  1. 　紫外線を含む光を受光して電流を発生させる受光素子と、
    　前記受光素子の受光面側に積層された保護膜と、
    　ＵＶ－Ａ波とＵＶ－Ｂ波とを透過するフィルタ膜とを有し、
    　前記フィルタ膜が前記保護膜の表面に積層されていることを特徴とする紫外線センサ。     A light receiving element that receives light including ultraviolet light and generates current;
    A protective film laminated on the light receiving surface side of the light receiving element;
    It has a filter film that transmits UV-A and UV-B waves,
    The ultraviolet ray sensor characterized in that the filter film is laminated on the surface of the protective film.
  2. 　前記保護膜は、屈折率が１．３５～１．４８の低屈折材料により形成されており、前記保護膜の光学膜厚が０．２４６×λ×（２×ｎ－０．３）～０．２４６×λ×（２×ｎ＋０．３）（λ＝３１１ｎｍ、ｎは１以上の自然数）であることを特徴とする請求項１に記載の紫外線センサ。 The protective film is formed of a low refractive material having a refractive index of 1.35 to 1.48, and the optical film thickness of the protective film is 0.246 × λ × (2 × n−0.3) to 0. The ultraviolet ray sensor according to claim 1, wherein 246 × λ × (2 × n + 0.3) (λ = 311 nm, n is a natural number of 1 or more).
  3. 　前記保護膜は、９８ｎｍ～１１７ｎｍ、または１９４ｎｍ～２１７ｎｍ、または２９１ｎｍ～３１４ｎｍの膜厚で形成されていることを特徴とする請求項１または請求項２に記載の紫外線センサ。 The ultraviolet sensor according to claim 1, wherein the protective film is formed to have a thickness of 98 nm to 117 nm, 194 nm to 217 nm, or 291 nm to 314 nm.
  4. 　前記保護膜は、酸化シリコンを用いて形成されていることを特徴とする請求項１から請求項３のいずれか１項に記載の紫外線センサ。 The ultraviolet ray sensor according to any one of claims 1 to 3, wherein the protective film is formed using silicon oxide.
  5. 　前記フィルタ膜は、低屈折率材料（屈折率１．３～１．５）と高屈折率材料（屈折率１．９～２．２）とが交互に積層された多層膜で構成されていることを特徴とする請求項１から請求項４のいずれか１項に記載の紫外線センサ。 The filter film is composed of a multilayer film in which low refractive index materials (refractive index 1.3 to 1.5) and high refractive index materials (refractive index 1.9 to 2.2) are alternately laminated. The ultraviolet sensor according to any one of claims 1 to 4, characterized in that.
  6. 　前記受光素子は、半導体基板と、前記半導体基板上に形成された酸化層と、前記酸化層上に形成されたＳＯＩ層とを有し構成されていることを特徴とする請求項１から請求項５のいずれか１項に記載の紫外線センサ。 The light receiving element is configured to have a semiconductor substrate, an oxide layer formed on the semiconductor substrate, and an SOI layer formed on the oxide layer. The ultraviolet sensor according to any one of 5.
PCT/JP2012/053424 2011-04-06 2012-02-14 Ultraviolet sensor WO2012137539A1 (en)

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