JP2002350228A - Ultraviolet sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet sensor having high accuracy and small size, and capable of stably detecting an arbitrary wavelength by enlarging the sensitivity ratio of a measured wavelength region to a non-measured wavelength region, and reducing an error of the measured wavelength region due to an angle of incidence of light. SOLUTION: This ultraviolet sensor at least includes a semiconductor layer having at least one or more elements among the group III elements, nitrogen, hydrogen and having sensitivity to 170 to 420 nm, and at least a filter is formed on the light receiving side of the semiconductor layer. The filter is adapted to cut light on the longer wavelength side than the wavelength where the sensitivity of the semiconductor layer is maximum at 170 to 420 nm and also on the longer wavelength side than the wavelength 20% of the maximum sensitivity at 170 to 420 nm of the semiconductor layer. Preferably the filter is a membrane laminated multi-layer filter, and preferably the surface of the filter is provided with a means for making uniform the directional property of light incidence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet sensor capable of measuring the amount of ultraviolet light in a desired wavelength range with little dependence on the angle of incidence.

[0002]

2. Description of the Related Art In recent years, one of the biggest problems in the global environment is that the amount of ultraviolet rays on the ground is increasing due to the destruction of the ozone layer. Ultraviolet rays have a serious effect on health, such as the occurrence of skin cancer, increased photosensitivity due to DNA damage, and photoaging. For this reason, it is necessary to measure ultraviolet rays in a wide range. As the ozone in the stratosphere decreases, the amount of ultraviolet light absorbed below 330 nm decreases, and the amount of ultraviolet light reaching the ground fluctuates. Especially UV
It is known that high-energy ultraviolet rays having a wavelength of 320 nm or less called -B cause DNA destruction and the like and cause various disorders to the skin.

[0003] For this reason, measuring the amount of UV-B ultraviolet rays is also important in environmental evaluation. In order to measure ultraviolet light in this wavelength range, a band-pass filter is used. However, a normal filter controls the transmittance by multiple reflection using a multilayer film. In the case where there is a secondary light, since there is also a transmission region in the long wavelength region as the secondary light, when extracting only the ultraviolet region, it is necessary to use another filter overlaid, and the transmittance is reduced. there were. In addition, the wavelength transmission range greatly varies depending on the incident angle, and it has been difficult to accurately measure the amount of UV-B ultraviolet light. In order to further reduce the angle dependence, a waveguide is provided on the sensor in order to approach linear incidence, and there is a disadvantage that the sensor becomes large. On the other hand, in a conventional ultraviolet detecting element using a silicon-based photodetector, deterioration of the element was so large that continuous measurement could not be performed.

[0004] As industrial equipment to which ultraviolet rays are applied, 254 nm or 365 nm is widely used in various fields such as a color image output device, an ozone generator or a semiconductor manufacturing device, and a stereolithography field.
There is a need for an inexpensive ultraviolet detector that is highly sensitive, stable for a long time, and inexpensive for a mercury lamp of nm. In these ultraviolet application fields, it is important to constantly measure ultraviolet rays and perform reaction, production or processing under a controlled amount of light in order to stabilize product quality. However, conventional ultraviolet detectors have many problems of silicon, and short-wavelength ultraviolet light and high-intensity ultraviolet light have a problem that silicon itself deteriorates and a long-wavelength cut filter used for cutting visible light deteriorates. I could not always monitor.

Further, Japanese Patent Application Laid-Open No. 8-136340 proposes a method of installing an ultraviolet sensor at a distance from a lamp. Since a large amount of heat is emitted from the ultraviolet light source, the temperature around the device under test is often high, and in the case of a semiconductor having a small band gap such as silicon, dark current is generated by heat carriers. Since it becomes impossible to operate due to an increase, it is necessary to devise a cooling means and an installation place. In particular, with respect to ultraviolet rays having a wavelength of 300 nm or less, various members used such as a polymer material and an adhesive are deteriorated. Therefore, deterioration of all materials used for the sensor is a problem.

[0006] Further, in the case of industrial 185 nm and 254 nm mercury lamps, an ultraviolet detector that is stable and inexpensive for a long period of time is required. However, in the case of a conventional ultraviolet detector using a silicon-based photodetector, deterioration of the element is required. And the measurement could not be performed continuously.

Further, the emission wavelength of the emission line of a mercury lamp is 435.8 nm or 546.0 in visible light in addition to ultraviolet light.
In the case of a photodetector that has a strong bright line at nm, 578 nm, etc. and is sensitive to visible light, a filter must be used. Therefore, in the case of a light-receiving element having a wide range of sensitivity, such as a silicon photodiode, the combination of a long-wavelength cut filter is complicated, so that there is a problem that ultraviolet transmittance is reduced and sensitivity is reduced. Since complete long-wavelength opacity cannot be achieved by the filter,
There were problems of sensitivity to visible light and light deterioration of the filter.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the sensitivity ratio between the measurement wavelength region and the non-measurement wavelength region and to reduce the error in the measurement wavelength region due to the incident angle of light to achieve high precision and small size. It is intended to provide an ultraviolet sensor capable of detecting a stable and arbitrary wavelength.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a predetermined amount of light is applied to the light-receiving side of a semiconductor layer containing a group III element, nitrogen, and hydrogen and having sensitivity to a predetermined wavelength. The present inventors have found that an ultraviolet sensor formed with a filter that cuts light having a wavelength solves the above-mentioned problem, and has come to correspond to the present invention. That is, the present invention provides <1> at least one or more of the group III elements, nitrogen, and hydrogen, and 170 to 420 nm.
A semiconductor layer having a sensitivity within the range, at least on the light-receiving side of the semiconductor layer, an ultraviolet sensor having a filter formed, wherein the filter has at least a sensitivity of the semiconductor layer of 170 to 420 nm. On the longer wavelength side than the maximum wavelength in the range, 17
An ultraviolet sensor characterized in that the filter is a filter that cuts light on a longer wavelength side than a wavelength at which the maximum sensitivity is 20% within a range of 0 to 420 nm.

<2> The ultraviolet sensor according to <1>, wherein the filter is a multilayer film filter. <3> A means for equalizing the directionality of light incidence is provided on the surface of the filter. <1>
Or it is an ultraviolet sensor as described in <2>.

<4> The ultraviolet ray according to <3>, wherein the means for making the direction of incidence of light uniform is a translucent plate provided on the filter and having a light scattering function. It is a sensor. <5> The ultraviolet sensor according to <3>, wherein the means for equalizing the directionality of the light incidence is a roughened surface of the filter.

<6> The device according to <3>, wherein the means for equalizing the direction of incidence of light is a light transmitting material provided on the filter and having a plurality of through holes. UV sensor. <7> The ultraviolet sensor according to <3>, wherein the means for equalizing the directionality of light incidence is a microlens array plate provided on the filter.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The ultraviolet sensor of the present invention comprises at least one or more of the group III elements, nitrogen, and
Including hydrogen, and includes a semiconductor layer having a sensitivity in the range of 170 to 420 nm, at least a filter is formed on the light receiving side of the semiconductor layer, the filter, at least, the sensitivity of the semiconductor layer 170-420
a filter that cuts light on the longer wavelength side than the wavelength that is the maximum in the range of nm and longer than the wavelength that is 20% of the maximum sensitivity of the semiconductor layer in the range of 170 to 420 nm. I have.

By using the semiconductor layer and the filter, an ultraviolet sensor having no sensitivity of the semiconductor layer in the secondary light region of the filter and having sensitivity only in a desired wavelength region can be obtained. In the present invention, "a filter cuts light" means that a filter cuts light.
It means that more than% of light is cut.

FIG. 1 shows an example of the transmittance of the filter, the sensitivity of the semiconductor layer, and the combined sensitivity of the two (that is, the sensitivity as an ultraviolet sensor). The filter has a wavelength longer than the wavelength (170 nm in FIG. 1) where the sensitivity of the semiconductor layer is maximum in the range of 170 to 420 nm, and 20% of the maximum sensitivity of the semiconductor layer in the range of 170 to 420 nm. The light on the longer wavelength side than a certain wavelength (a in FIG. 1) (hereinafter sometimes simply referred to as “specific long-wavelength light”) is cut by 90%, and the semiconductor layer passes through 10% of the light before passing through the filter. Is reached, the sensitivity of the semiconductor layer to a specific long-wavelength light is less than 20%, so the combined sensitivity is the sensitivity of the wavelength (170 nm) at which the sensitivity of the semiconductor layer is the maximum within the range of 170 to 420 nm. It is less than 1/50. Therefore, an ultraviolet sensor having substantially no sensitivity to a specific long wavelength light is obtained.

It is more preferable that the filter used in the present invention is capable of cutting 95% or more of specific long wavelength light. In this case, since the transmittance of the filter is less than 5%, 5% × 20% = 1/100, and the sensitivity of the ultraviolet sensor to long-wavelength light is 1/100.
Less than.

In the filter used in the present invention, the sensitivity of the semiconductor layer is longer on the longer wavelength side than the range of 170 to 420 nm.
Any material can be used as long as it can cut light of a long wavelength adjacent to a wavelength (a in FIG. 1) at which the maximum sensitivity of the semiconductor layer in the range of 170 to 420 nm becomes 20% (a in FIG. 1). It may have a region, that is, a secondary light region, and such a case is included in the scope of the present invention.
This is because the semiconductor layer itself has no sensitivity in such a long wavelength range.

For example, when a filter that cuts a long wavelength region of 320 nm or more of UV-B is used, the semiconductor layer in the present invention has no sensitivity in the long wavelength region and has no sensitivity. The region may have a transmission region for secondary light or the like. For this reason, the number of combinations of the filters can be reduced, and a highly sensitive and stable ultraviolet sensor can be obtained.

As the filter used in the present invention, an ultraviolet-permeable multilayer film filter, particularly a multilayer film filter combining dielectric multilayer films, is preferable. However, since the multilayer film filter uses multiple reflection, the interference wavelength may vary depending on the optical path length in the multilayer film. In this case, the transmission wavelength is different between normal incidence and oblique incidence, and even if the transmission wavelength and the non-transmission wavelength range are designed for normal incidence, these wavelength ranges greatly deviate for oblique incidence. Would.

For example, in a filter having a transmission band at a short wavelength of 320 nm or less and an opaque wavelength region between 320 and 450 nm and a transmission band at 450 nm or more, the opaque wavelength region is formed at an oblique incidence of 45 degrees. 280-380
nm, and a transmission wavelength range occurs at 380 nm or more.
In particular, in the measurement of UV-B, the influence of scattered light in addition to direct sunlight from the sun is great, and in the measurement of UV-B, it is important that measurement of oblique incidence be performed accurately.

When measuring the amount of ultraviolet light from a light source such as a mercury lamp whose incident direction of light is constant, the ultraviolet sensor of the present invention may be formed of only the semiconductor layer of the present invention and a filter. When measuring the amount of ultraviolet light from the incident light source, it is preferable to provide a means for equalizing the directionality of the incident light. This minimizes the change in the transmission spectrum of the filter with respect to the obliquely incident light source, and can solve the above problem. As a means for making the directionality of the light incident uniform, there is a means for changing the light obliquely incident on the surface of the filter in close contact with the semiconductor layer to scatter or vertical incidence.

As means for scattering the light obliquely incident on the surface of the filter, a translucent plate having a light scattering function as a light scattering substance or a diffusing substance may be provided on the light receiving surface side of the filter, or the surface of the filter may be directly scattered. Surface roughening and the like. Specific examples of the translucent plate and the like include a film that transmits ultraviolet light and is cloudy, and a roughened quartz plate and the like.

The above-mentioned film that transmits ultraviolet light and is opaque includes an opaque film, colored white, or
A material in which white fine powder is dispersed is used. Specific examples include PTFE and milky white glass.

Examples of the roughened quartz plate include a quartz plate roughened by using hydrogen fluoride or etching by mechanical means such as sandblasting. The object to be roughened is not limited to a quartz plate. In this case, the center line average roughness _Ra75 of the roughened quartz plate is preferably 0.1 to 10 μm, and more preferably 0.1 to 5 μm. Furthermore, as described later, when light is incident from the substrate side,
The translucent substrate used may be roughened. The degree of surface roughening in this case is the same as that of the roughened quartz plate.

In order to directly roughen the surface of the filter, mechanical means such as a file or sand blast may be used.
Furthermore, a chemical method such as etching can be used. In this case, the center line average roughness Ra _{75 of the} filter
Is preferably 0.1 to 10 μm, and 0.1 to 5 μm.
More preferably, it is μm.

On the other hand, as means for changing the obliquely incident light to vertical incidence, a light transmissive material having a plurality of through holes, a fiber-like material bundled, or a linear direction is provided on the light receiving surface side of the filter. Means for providing a microlens array plate for condensing light and the like can be given. As the light transmitting material having a plurality of through-holes, a material having a self-standing structure by etching an Al base material of an anodic oxide film can be used, or a material that is mechanically perforated can be used. The relationship between the thickness and the hole diameter is desirably that the hole diameter is 1 or more with respect to the thickness 2.

The semiconductor layer of the ultraviolet sensor according to the present invention comprises II
It contains at least one or more of group I elements (group number is 13 according to the revised version of IUPAC's 1989 inorganic chemical nomenclature) and nitrogen and hydrogen, and has a sensitivity in the range of 170 to 420 nm. Is a semiconductor layer having high sensitivity. As the group III element, specifically, B, Al,
Although Ga, In, and Tl are mentioned, it is preferable that it is at least one or more selected from Al, Ga, and In.

As a raw material of the group III element in the semiconductor layer, an organic metal compound containing one or more elements selected from Al, Ga and In can be used. As these organometallic compounds, liquids and solids such as trimethylaluminum, triethylaluminum, tertiary butylaluminum, trimethylgallium, triethylgallium, tertiarybutylgallium, trimethylindium, triethylindium, tertiarybutylindium, etc. are vaporized and used alone. Alternatively, it can be used in a mixed state by bubbling with a carrier gas. Hydrogen, hydrocarbons such as N ₂ , methane and ethane, and halogenated carbons such as CF ₄ and C ₂ F ₆ can be used as the carrier gas.

As the nitrogen raw material, N ₂ , NH ₃ , N
Gases and liquids such as F ₃ , N ₂ H ₄ and methyl hydrazine can be used by vaporizing or bubbling with a carrier gas. In the semiconductor layer, p,
An element can be doped into the film for controlling n.
The n-type elements that can be doped include Group IA (IUPA).
C, the group number according to the revised 1989 inorganic chemical nomenclature of C is 1) Li, and the IB group (the group number according to the IUPAC revised 1989 inorganic chemical nomenclature is 11) Cu, Ag, A
u, Mg of group IIA (group number 2 according to the revised version of IUPAC's inorganic chemical nomenclature 1989), group IIB (IUPA
According to the revised 1989 inorganic chemical nomenclature of C, the family number is 1
2) Si, Ge, S of Zn, IVA group (family number according to IUPAC revised 1989 inorganic chemical nomenclature 14)
n, Pb, S, Se, Te of the VIA group (the group number is 16 according to the revised edition of IUPAC's 1989 inorganic chemical nomenclature).
Can be mentioned. Among them, C, Si, Ge, and Sn are preferable from the viewpoint of controllability of charge carriers.

The p-type elements that can be doped include IA
Group Li, Na, K, IB group Cu, Ag, Au, II
Group A Be, Mg, Ca, Sr, Ba, Ra, Group IIB Zn, Cd, Hg, Group IVA C, Si, Ge, S
n, Pb, S, Se, Te of the VIA group (the group number is 16 according to the revised edition of IUPAC's 1989 inorganic chemical nomenclature),
Cr, Mo, W of group VIB (group number 6 according to the revised edition of IUPAC's 1989 inorganic chemical nomenclature) and F of group VIII
e (family number according to the revised IUPAC 1989 inorganic chemical nomenclature is 8), Co (the family number according to the revised IUPAC 1989 inorganic chemical nomenclature is 9), Ni (IUPAC)
According to the revised 1989 inorganic chemical nomenclature, the family number is 1
0). Above all, Be, Mg, C
a, Zn, and Sr are preferred from the viewpoint of controllability of charge carriers.

The semiconductor layer has a weak n-type undoped film, and can form an electric field inside by forming a Schottky barrier or forming a pn junction for obtaining photosensitivity. In order to expand the internal depletion layer, i
It can also be a type. From this point, the elements to be doped are particularly preferably Be, Mg, Ca, Zn, and Sr.

At the time of doping, SiH ₄ , Si ₂ H ₆ , GeH ₄ , GeF ₄ , SnH _4, etc. are used for n-type, and BeH ₂ , BeCl ₂ , etc. are used for i-type and p-type.
BeCl ₄ , cyclopentadienyl magnesium, dimethyl calcium, dimethyl strontium, dimethyl zinc, diethyl zinc and the like can be used in a gaseous state. For doping these elements into the film, known methods such as a thermal diffusion method and an ion implantation method can be adopted. The semiconductor may be single crystal or non-single crystal. Further, the semiconductor layer may be in an amorphous phase or a microcrystalline phase, or may be in a mixed state of a microcrystalline phase and an amorphous phase. The crystal system may be any one of a cubic system and a hexagonal system, or a state in which a plurality of crystal systems are mixed.

The crystal system may be either cubic or hexagonal, or may be a mixture of a plurality of crystal systems. The size of the microcrystal is 5 nm to 5 μm and can be measured by X-ray diffraction, electron beam diffraction, shape measurement using an electron micrograph of a cross section, or the like. Further, a film grown in a columnar shape, a film having a single peak in an X-ray diffraction spectrum and a highly oriented crystal plane direction, or a single crystal may be used.

The semiconductor layer has a hydrogen concentration of 0.5 atomic%.
It is preferable that at least 50 atomic% of hydrogen be contained. When hydrogen contained in the semiconductor layer is less than 0.5 atomic%, bond defects at crystal grain boundaries, or bond defects and dangling bonds inside the amorphous phase are eliminated by bonding with hydrogen,
Insufficient to inactivate the defect levels formed in the band, increase the number of coupling defects and structural defects, lower the dark resistance and lose the photosensitivity, so that it can function as a practical photoconductor. It may not be possible.

On the other hand, the hydrogen in the semiconductor layer is 50
If the atomic percentage is exceeded, the probability of hydrogen bonding to two or more group III elements and nitrogen increases, and these elements do not maintain a three-dimensional structure and form a two-dimensional and chain network. Because a large amount of voids are generated at the grain boundaries,
As a result, a new level is formed in the band, and the electrical characteristics are deteriorated, and the mechanical properties such as hardness are reduced. Further, the semiconductor layer is easily oxidized, and as a result, a large amount of impurity defects are generated in the semiconductor layer, so that good photoelectric characteristics may not be obtained.

The semiconductor layer contains 50 atomic% of hydrogen.
Is exceeded, hydrogen is inactivated for doping the dopant to control the electrical characteristics, so that an electrically active amorphous or microcrystalline optical semiconductor layer cannot be obtained as a result. There is. Note that the upper limit of the amount of hydrogen in the semiconductor layer is more preferably 30 atomic% or less.

The absolute value of the amount of hydrogen can be measured by hydrogen forward scattering (HFS). It can also be estimated by measuring the amount of hydrogen released by heating or measuring the infrared absorption spectrum. Further, these hydrogen bonding states can be easily measured by an infrared absorption spectrum. In addition, together with the hydrogen raw material, a one-coordinate halogen element (F, Cl, Br,
I) may be included.

In the above semiconductor layer, the relation between the number m of group III elements and the number n of nitrogen atoms preferably satisfies the following relational expression I. 0.5: 1.0.ltoreq.m: n.ltoreq.1.0: 0.5 Relational Expression I Outside this range, there is little tetrahedral bond in the bond between the group III element and the group V element. In some cases, and may not function as a good semiconductor.

The optical gap of the semiconductor layer can be arbitrarily changed depending on the mixing ratio of the group III element. Ga
In the case where N is higher than 3.2 to 3.5 eV on the basis of H, from the band gap capable of absorbing only a wavelength shorter than 300 to 330 nm by adding Al, only the absorption of 250 nm or less is possible. It can be changed up to the band gap (about 6.0 to 6.5 eV). The band gap can also be adjusted by adding Al and In. In the present invention, it is necessary to have a sensitivity in the range of 170 to 420 nm, and these compositions may be adjusted according to the purpose, and a semiconductor layer having sensitivity to an appropriate wavelength may be obtained.

The composition of each element in the semiconductor layer can be measured by a method such as X-ray photoelectron spectroscopy (XPS), electron microprobe, Rutherford back scattering (RBS), or secondary ion mass spectrometer.

The semiconductor layer can be manufactured as follows. However, the present invention is not limited to this. In the following manufacturing method, an example using at least one element selected from the group consisting of Al, Ga, and In as the group III element will be described.

FIG. 2 is a schematic structural view of an apparatus for forming a semiconductor layer for manufacturing a semiconductor light receiving element according to the present invention, wherein plasma is used as an activating means. In FIG.
1 is a container which can be evacuated and evacuated, 2 is an exhaust port, 3 is a substrate holder, 4 is a heater for heating the substrate, 5 and 6 are quartz tubes connected to the container 1, and gas introduction tubes 9 and 10, respectively. Is in communication with The quartz tube 5 is connected to a gas introduction tube 11, and the quartz tube 6 is connected to a gas introduction tube 12.

In this apparatus, for example, N ₂ is used as a nitrogen source and introduced into the quartz tube 5 from the gas introduction tube 9. For example, 2.4 is connected to a microwave waveguide 8 connected to a microwave oscillator (not shown) using a magnetron.
A microwave of 5 GHz is supplied to discharge into the quartz tube 5. For example, H ₂ is introduced into the quartz tube 6 from another gas introduction tube 10. A high frequency of 13.56 MHz is supplied from a high frequency oscillator (not shown) to the high frequency coil 7 to generate a discharge in the quartz tube 6. By introducing, for example, trimethylgallium from the gas introduction pipe 12 arranged on the downstream side of the discharge space, the substrate set on the substrate holder 3 is placed on the substrate.
An amorphous, microcrystalline, or single crystal gallium nitride optical semiconductor can be formed.

Whether it becomes amorphous, microcrystalline, highly oriented columnar grown polycrystal, or single crystal depends on the type of substrate, substrate temperature, gas flow pressure and discharge conditions. The substrate temperature is preferably from 100C to 600C. When the substrate temperature is high and / or when the flow rate of the group III element source gas is small, it tends to be microcrystals or single crystals. When the substrate temperature is lower than 300 ° C. and the flow rate of the group III element source gas is small, the material tends to be crystalline, and when the substrate temperature is higher than 300 ° C., II is lower than at low temperature.
Even when the flow rate of the group I source gas is large, it tends to be crystalline. Further, for example, when H ₂ discharge is performed, crystallization can be performed more than when H ₂ discharge is not performed. Instead of trimethylgallium, an organometallic compound containing indium or aluminum can be used, or these can be mixed. Also, these organometallic compounds,
The gas may be separately introduced from the gas introduction pipe 11.

A gas containing at least one element selected from C, Si, Ge and Sn, or a gas containing Be,
A gas containing at least one element selected from the group consisting of Mg, Ca, Zn, and Sr is supplied to the downstream side of the discharge space (gas introduction pipe 1).
1 or by introducing gas through a gas introduction pipe 12).
An amorphous, microcrystalline, or single crystal nitride semiconductor of any conductivity type such as a p-type or a p-type can be obtained. In the case of C, carbon of an organometallic compound may be used depending on conditions.

In the above-described apparatus, active nitrogen or active hydrogen formed by discharge energy may be controlled independently, or a gas such as NH ₃ containing both nitrogen and hydrogen atoms may be used. . Further, H ₂ may be added. Further, a condition under which active hydrogen is liberated from the organometallic compound may be used. In this way, activated group III atoms and nitrogen atoms are present on the substrate in a controlled state, and hydrogen atoms convert methyl and ethyl groups to inert molecules such as methane and ethane. Therefore, it is possible to form an amorphous or crystalline film with little or no carbon and suppressed film defects despite the low temperature. When obtaining a hydrogenated amorphous silicon film, microcrystalline silicon film, or crystalline silicon film, hydrogen is used instead of nitrogen gas, and a gas such as silane, disilane, or trisilane is used instead of an organic metal gas. It may be used. Further, a plasma CVD apparatus may be used.

In the above-described apparatus, the activating means may be a high frequency discharge, a microwave discharge, an electron cyclotron resonance method or a helicon plasma method, or one of them may be used. The above may be used. Further, in FIG. 2, high-frequency discharge and microwave discharge are used, but both may be microwave discharge or co-high-frequency discharge. Further, both may be of the electron cyclotron resonance type or the helicon plasma type. When discharging by high-frequency discharge, the high-frequency oscillator may be of an inductive type or a capacitive type. The frequency at this time is preferably 50 kHz to 100 MHz.

When different activating means (exciting means) are used, it is necessary to generate a discharge at the same pressure at the same time, and a pressure difference is provided between the discharge area and the film forming section (in the vessel 1). Is also good. When the same pressure is used, when different activation means (excitation means), for example, a microwave and a high-frequency discharge are used, the excitation energy of the excited species can be largely changed, which is effective for controlling the film quality.

In the method of forming a semiconductor layer according to the present invention, the substrate temperature can be kept low as compared with the formation of a general optical semiconductor. A material for formation, for example, indium tin oxide (ITO) provided on glass can be used as a material for forming a conductive substrate or a light-transmitting conductive layer described later. The semiconductor layer can be formed in an atmosphere in which at least hydrogen is activated, such as a reactive vapor deposition method, ion plating, or reactive sputtering.

The substrate used in the present invention may be conductive or insulating, and may be crystalline or amorphous. Examples of the conductive substrate include metals such as aluminum, stainless steel, nickel, and chromium and alloy crystals thereof, Si, Ga
Semiconductors such as As, GaP, GaN, SiC, and ZnO can be given. Alternatively, an insulating substrate having a substrate surface subjected to a conductive treatment can be used. Examples of the insulating substrate include a polymer film, glass, quartz, and ceramic. The conductive treatment is performed by forming a film of the above metal, gold, silver, copper, or the like by an evaporation method, a sputtering method, an ion plating method, or the like.

The light may be incident from the substrate side or the semiconductor layer side, but it is necessary for the light to reach the semiconductor layer through the filter. When light is incident from the substrate side, the substrate may be glass, quartz, sapphire, MgO,
Transparent inorganic materials such as LiF, CaF ₂ , fluorine resin, polyester, polycarbonate, polyethylene,
A transparent organic resin film or plate such as polyethylene terephthalate or epoxy, an optical fiber, a selfoc optical plate, or the like can be used. Among these, quartz, sapphire, MgO, LiF, CaF _{2 and the} like are preferable when measuring ultraviolet rays of 300 nm or less.

The transparent electrode provided on the transparent substrate is made of a transparent conductive material such as ITO, zinc oxide, tin oxide, lead oxide, indium oxide, copper iodide, and is formed by vapor deposition, ion plating, sputtering or the like. Or a metal such as Al, Ni, Au, or the like formed thin enough to be translucent by vapor deposition or sputtering. When measuring short wavelengths of 300 nm or less, a translucent metal electrode deposited is desirable. Alternatively, a light-transmitting electrode may be provided directly over the semiconductor layer, or a pair of electrodes in which the electrodes are provided with a certain gap therebetween may be used.

An example of an ultraviolet sensor using the semiconductor layer and the filter of the present invention is shown below. A semiconductor layer having sensitivity in the range of 170 to 420 nm according to the present invention is formed on the surface of a substrate, and a transparent conductive layer or a translucent conductive layer (light-transmitting conductive layer) is provided thereon as an electrode. The light-transmitting conductive layer desirably efficiently transmits ultraviolet light of 300 nm or less, and the above-described light-transmitting electrode can be used. Further, a filter for cutting the specific long wavelength light in the present invention is provided on the light receiving surface side. Here, the light-receiving surface side means a surface that receives ultraviolet light, and a filter is provided on the substrate side when receiving light from the substrate side, and a filter is provided on the semiconductor layer when receiving light from the opposite side of the substrate side. Will be provided. Further, a means for equalizing the directionality of light incidence may be provided on the filter.

With the above configuration, an ultraviolet sensor having no sensitivity to secondary light generated in a long wavelength region and having sensitivity only to a wavelength in a desired range can be manufactured. Further, by providing means for making the directionality of light incidence uniform, a change in wavelength due to oblique incidence can be suppressed.

[0055]

Embodiments will be described below with reference to embodiments. (Example 1) A semiconductor layer in the ultraviolet light quantity measuring device of the present invention was manufactured using the above-described device of FIG. 2, and an ultraviolet sensor was manufactured. A substrate obtained by sputtering indium tin oxide (ITO) at 1000 Å on a washed borosilicate glass substrate having a thickness of 0.2 mm is placed on a substrate holder 3, the inside of the container 1 is evacuated through an exhaust port 2, and the substrate is heated by a heater 4. Was heated to 350 ° C. Further, 1000 N ₂ gas is introduced into the quartz tube 5 having a diameter of 25 mm from the gas introduction tube 9.
sccm and introduced through microwave waveguide 8 at 2.45.
A microwave of GHz was set to an output of 250 W, matching was performed with a tuner, and discharge was performed. The reflected wave at this time is 0
W.

On the other hand, 500 sccm of H ₂ gas was introduced from the gas introduction tube 10 into the quartz tube 6 having a diameter of 30 mm. 1
The output of the high frequency of 3.56 MHz was set to 100W. The reflected wave was 0W. In this state, the gas introduction pipe 12
Trimethylgallium (TMGa) kept at 0 ° C
Was introduced through a mass flow controller while bubbling hydrogen at a pressure of 10 ⁶ Pa using hydrogen as a carrier gas. H ₂ gas was introduced into the cyclopentadienyl magnesium kept at 20 ° C. from the gas introduction tube 12 at a pressure of 65000 Pa, and introduced into a 1 sccm reaction region through a mass flow controller. At this time, the reaction pressure measured by a Baratron vacuum gauge was 66.5 Pa.
(0.5 Torr). Film formation is performed for 30 minutes and 0.1
A μm Mg-doped GaN: H film was prepared. The amount of hydrogen is 7
Atomic%.

Hydrogen was Ga-based by IR spectrum measurement.
H, NH were contained in this GaN film. A spot-like ring pattern was observed in the electron diffraction spectrum, indicating that the film was a crystalline film. The film was transparent. On this, Au having a diameter of 3 mm and a thickness of 0.01 μm is placed.
Was produced by vacuum evaporation. A quartz substrate having a thickness of 0.3 mm is provided on this electrode, and a 320 n
m and a filter of a dielectric multilayer film (manufactured by Asahi Spectroscopy Co., Ltd.) that transmits light having a short wavelength of not more than m and cuts light in a range of 320 to 450 nm was laminated thereon to produce an ultraviolet sensor.

The characteristics of the ultraviolet sensor were measured. As a result, from 250 nm to 3
It has been found that the filter has a sensitivity of 20 nm or less and can measure light perpendicularly incident on the filter. On the other hand, at an incident angle of 45 degrees, the sensitivity was 280 nm or less, and a sensitivity region was generated at a wavelength longer than 380 nm up to 430 nm, and ultraviolet light could not be measured accurately at oblique incidence.

The above characteristics were measured by irradiating the sensor with monochromatic light from a Xe light source using a spectroscope and changing the angle of the sensor with respect to the light source so that the distance could not be changed. The case where the sensitivity is 50% or more with respect to vertical incidence is defined as "sensitivity", and the case where the sensitivity is 50% or less with respect to vertical incidence is defined as "no sensitivity".

(Example 2) A quartz plate having a thickness of 0.2 mm whose surface was sandblasted to a roughness of 1.0 µm was _superposed on the filter in the same manner as in Example 1, An ultraviolet sensor was manufactured. When the characteristics were measured in the same manner as in Example 1, the transmission wavelength of the filter showed that the rise of the cut wavelength became gentle by 10%, but the measurable wavelength region did not change below 320 nm.
It turned out that it is possible to measure not only vertically incident light but also obliquely incident light. Note that “the rise of the cut wavelength becomes gentle by 10%” means that the half-value width on the long wavelength side of the transmission wavelength of the filter is increased by 10%.

Example 3 A filter was used in the same manner as in Example 1 except that the filter used in Example 1 was used after sandblasting the surface to a roughness of Ra ₇₅ of 1.0 μm.
An ultraviolet sensor was manufactured. The characteristics were measured in the same manner as in Example 1. As a result, the transmission wavelength of the filter became gentle with a rise of the cut wavelength of 10%, but the measurable wavelength region did not change at 320 nm or less. It was also found that oblique incident light can be measured.

(Example 4) An ultraviolet sensor was manufactured in the same manner as in Example 1 except that a Teflon (registered trademark) film having a thickness of 0.3 mm was laminated on the light receiving surface side of the filter. When the characteristics were measured in the same manner as in Example 1, the transmission wavelength of the filter was such that the rise of the cut wavelength was 10%.
Although it became gentle, there was no change in the measurable wavelength region below 320 nm, and it was found that measurement was possible not only for vertically incident light but also for obliquely incident light.

(Example 5) On the Au electrode side, a thickness of 0.1 mm was applied.
Same as Example 1 except that a 3 mm quartz substrate was provided, and an interference filter that transmits light at a half-width of 10 nm centered at 365 nm and has a light transmission region (secondary light region) near 710 nm was laminated. Thus, an ultraviolet sensor was manufactured. When the characteristics were measured in the same manner as in Example 1, it was found that there was sensitivity only at around 365 nm at normal incidence to the filter, and that light perpendicular to the filter could be measured. On the other hand, at an incident angle of 45 degrees, 365 nm was opaque, and the light of a mercury lamp having a peak at 365 nm incident on the filter at 45 degrees could not be measured accurately. Furthermore, a microlens array plate (manufactured by Corning, aperture diameter 0.2 m)
m and a thickness of 0.4 mm), and oblique incidence characteristics were measured in the same manner. Even at an incident angle of 45 degrees, as in the case of normal incidence when the microlens array plate was not stacked,
It has been found that there is sensitivity only around 365 nm, and it is possible to measure not only vertically incident light but also obliquely incident light.

[0064]

The present invention provides a highly accurate, small, and stable ultraviolet sensor that increases the sensitivity ratio between the measurement wavelength region and the non-measurement wavelength region and reduces errors in the measurement wavelength region due to the incident angle of light. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the transmittance of a filter, the sensitivity of a semiconductor layer, and the combined sensitivity.

FIG. 2 is a schematic configuration diagram showing a preferred embodiment of an apparatus for manufacturing a non-single-crystal optical semiconductor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Exhaust port 3 Substrate holder 4 Heater 5, 6 Quartz tube 7 High frequency coil 8 Micro waveguide 9-12 Gas introduction tube

Claims (7)

[Claims] At least one element selected from the group III elements, nitrogen and hydrogen, and
An ultraviolet sensor comprising a semiconductor layer having a sensitivity in a range of 70 to 420 nm, and a filter formed on at least a light receiving side of the semiconductor layer, wherein the filter has a sensitivity of at least 170 in the semiconductor layer. A filter that cuts light on the longer wavelength side than the wavelength maximum in the range of ~ 420 nm and longer wavelength than the wavelength which is 20% of the maximum sensitivity of the semiconductor layer in the range of 170 to 420 nm. And UV sensor. 2. The ultraviolet sensor according to claim 1, wherein the filter is a multilayer film filter. 3. The ultraviolet sensor according to claim 1, wherein a means for equalizing the direction of incidence of light is provided on a surface of the filter. 4. The ultraviolet sensor according to claim 3, wherein the means for equalizing the direction of incidence of the light is a translucent plate having a light scattering function provided on the filter. . 5. The ultraviolet sensor according to claim 3, wherein the means for making the direction of incidence of light uniform is a roughened surface of the filter. 6. The ultraviolet light according to claim 3, wherein the means for equalizing the directionality of the light incidence is a light transmitting material provided on the filter and having a plurality of through holes. sensor. 7. The ultraviolet sensor according to claim 3, wherein the means for equalizing the direction of incidence of light is a microlens array plate provided on the filter.