JP2009038157A - Light receiving element array, one-dimensional light receiving element array, and two-dimensional light receiving element array - Google Patents

Abstract

Provided is a light receiving element array capable of receiving light by distinguishing a plurality of wavelength ranges by a simple mechanism.
A light receiving element array for detecting light incident from an incident surface side, the light receiving element array being disposed on a light receiving layer of a compound semiconductor and an incident surface side of the light receiving layer, and having a transmission wavelength band. A plurality of different permeable membranes 7 and a plurality of electrodes 12 that individually capture currents generated in a plurality of light receiving portions in the light receiving layer corresponding to the plurality of permeable membranes are provided. The permeable membrane 7 is composed of a single layer or a plurality of layers.
[Selection] Figure 1

Description

  The present invention relates to a light receiving element array having a plurality of light receiving portions having sensitivity in different wavelength ranges, a one-dimensional light receiving element array, and a two-dimensional light receiving element array.

  Composition analysis of animals and plants or their derivatives can be performed by measuring the transmittance and reflectance of each band of infrared to near-infrared light, but until now, changing the light source or projecting to the sample In many cases, the transmittance and reflectance of the sample in each wavelength region are measured with different timings by changing the wavelength region of the light. For example, when the ratio of the amount of cellulose and moisture contained in paper or the like is obtained with one infrared sensor, it is necessary to measure the transmittance of light in three wavelength ranges including the background wavelength range. A method of measuring light in one wavelength range by rotating a three-hole filter wheel whose transmission band is adjusted to three wavelength ranges and synchronizing the transmission of the object to be measured in each band at different timings. Proposed (Patent Document 1).

  Also, a method for measuring the reflectance of these two bands while arranging an LED for measurement light and an LED for reference light and switching them in an electronic circuit in the measurement of the moisture of the object to be measured is disclosed ( Patent Document 2). According to the above Patent Documents 1 and 2, the transmittance or reflectance of each band can be determined with high accuracy in consideration of the degree of background modulation, and finally the moisture and cellulose content of the object to be measured. Measurement accuracy can be increased.

The above is the case of infrared to near-infrared light, but it may be necessary to determine the intensity distribution for each wavelength region in the visible light to infrared region as well. For example, in an image sensor used for image information processing for assisting safe driving of a vehicle, an example is an apparatus capable of imaging using near infrared light at night and using visible light in the daytime (Patent Literature). 3). In this example, a first light receiving element group having a light receiving sensitivity for near infrared light and a second light receiving element group having a light receiving sensitivity for visible light are uniformly mixed and arranged on one sensor chip. The configuration is disclosed. Specifically, since light having a long wavelength has a small attenuation in the light receiving element, the second light receiving element group having light receiving sensitivity for near infrared light has light receiving sensitivity for a deep position of the sensor chip and for visible light. The first light receiving element group discloses a structure to be formed at a shallow position. According to this configuration, the image processing can be performed as it is without switching the light reception signal between nighttime and daytime.
JP 7-260680 A JP-A-9-259882 JP 2003-274422 A

  However, in the configurations of Patent Documents 1 and 2, since two or more light sources or filters are switched to incident light while switching in a short time, the apparatus becomes large and two-dimensional information cannot be obtained about the sample. Further, in the configuration of Patent Document 3, it is necessary to change the depth position to one sensor chip to form two types of light receiving element groups, which complicates the manufacturing process and results in an expensive sensor chip.

  If a sensor chip capable of distinguishing and receiving light in a plurality of bands can be obtained more easily, there are a wide variety of practical applications. For example, in the analysis of animals and plants, it is very useful if information on transmittance or reflectance for each wavelength region of near-infrared light can be obtained with one inexpensive sensor chip. Furthermore, in addition to the above-mentioned information in the near infrared region, if new color information of visible light can be obtained, many new uses will be born. An object of the present invention is to provide a light receiving element array, a one-dimensional light receiving element array, and a two-dimensional light receiving element array that can receive light by distinguishing a plurality of wavelength ranges by a simple mechanism.

  The light receiving element array of the present invention detects light incident from the incident surface side. The light-receiving element array includes a compound semiconductor light-receiving layer, a plurality of transmission films arranged on the incident surface side of the light-receiving layer and having different transmission wavelength bands, and a plurality of light-receiving portions in the light-receiving layer corresponding to the plurality of transmission films. And a plurality of electrodes for separately capturing the current generated in step (b).

  With the above configuration, without using a large-scale spectroscopic device or a plurality of light sources having different emission wavelength ranges, the intensity of the absorption band of the object to be measured and other intensities such as the intensity of the background can be obtained based on a simple mechanism. Thus, qualitative and quantitative analysis can be performed with high accuracy. Qualitative and quantitative analysis of multiple substances in a mixed or mixed state is performed by increasing the number of transmission films that change the transmission wavelength range according to the absorption band or reflection band of the object to be measured according to the number of objects to be measured. be able to. Here, at least one of the paired p-part electrode and n-part electrode is divided into a plurality of parts corresponding to the permeable membrane as described above, and the other is a common electrode. There may be, and the above-mentioned purpose can be achieved. In addition, the range of the light receiving portion varies depending on the magnitude of the reverse bias voltage to be applied. However, here, the light receiving portion is used to mean a corresponding portion divided for each transmission film. In order to emphasize that the above light receiving unit corresponds to, for example, a pixel of the imaging device, it may be referred to as a unit light receiving unit.

  The above-mentioned permeable membrane is laminated on a laminate including a light-receiving layer of a compound semiconductor, and can be composed of a single layer or a plurality of layers. Thereby, an imaging device and various sensors can be reduced in size and weight rather than what includes an external optical component.

  The maximum transmission wavelength of each of the plurality of transmission films may be in the range of 1.65 μm to 3 μm. This makes it possible to use near-infrared light having an absorption band for many substances to be measured, and to easily perform qualitative and quantitative analysis of these substances.

  The light receiving layer may be any of InGaAs, GaInNAs, GaInNAsSb, and GaInNAsP. With this configuration, a light receiving element having sensitivity in the near infrared to visible range can be formed using a semiconductor light receiving device (chip) having a photodiode structure with a compound semiconductor multilayer structure. The above light-receiving layers may be collectively referred to as N-containing InGaAs-based layers or N-containing InGaAs-based light-receiving layers.

  The light receiving layer can be a semiconductor layer lattice-matched to InP. Thereby, the crystallinity of the light receiving layer can be improved, and a light receiving element array with a low dark current and hence with low noise can be obtained. In the case of lattice matching, when the lattice constant of the light receiving layer is a and the difference from the lattice constant of InP is Δa, | Δa / a | ≦ 0.002.

  Any of the plurality of permeable membranes may be a multilayer film. According to the multilayer film, an arbitrary transmission wavelength band can be designed relatively easily by combining a plurality of materials having different optical characteristics and changing a thickness, a repeating basic unit (a structure within one period), or the like. .

  Any of the above multilayer films can be formed of two or more layers of inorganic materials, oxides, nitrides, oxynitrides, fluorides, sulfides, and composites thereof. As a result, these materials are widely used for optical materials, film-forming materials are easily available, and optical characteristics such as wavelength dependency such as complex refractive index are relatively well known. A permeable membrane can be designed by using these optical characteristics, and a multilayer film can be actually produced.

  The permeable film may be a combination of a dielectric multilayer film and a semiconductor layer. As a result, a semiconductor layer epitaxially grown on the semiconductor laminate of the light-receiving element array, an irregularity formed on the laminate including the semiconductor substrate, and the convex portion used as a semiconductor layer, are used as part of the transmission film. This facilitates the formation of the permeable membrane.

  The semiconductor layer included in the transmissive film is located on the incident surface side of the stacked body including the light receiving layer, at a position corresponding to one or more of the plurality of light receiving portions, and the semiconductor layer and the semiconductor A plurality of transmission films can be formed by covering the surface layer of the laminated body where no layer is provided with a dielectric multilayer film. As a result, the material of the semiconductor layer whose wavelength dependency of the transmittance is well known is set according to the substance to be measured, and the ratio of one or more kinds of substances is obtained in combination with an appropriate dielectric multilayer film. It is possible to easily form a permeable membrane.

  The semiconductor layer included in the transmission film can be lattice-matched to InP and have an absorption edge wavelength shorter than that of the light receiving layer. This makes it possible to easily form a transmission film in which a layer for cutting light of a predetermined wavelength or less in the near infrared region is shared by the semiconductor layer. Further, the dark current can be lowered by improving the crystallinity. Further, by making lattice matching with InP, an increase in dark current can be prevented.

  The light receiving layer and the semiconductor layer included in the transmissive film may include one or more of group III elements In, Al, Ga and one or more of group V elements P, As, Sb, and N. , And a III-V group compound semiconductor. Thereby, the range of selection of the material of the permeable membrane can be widened while keeping the dark current low, and the permeable membrane can be easily produced according to the measurement, conditions and restrictions on the target substance.

  The semiconductor layer included in the light receiving layer and the transmissive film may be an InGaAs layer, or InGaAs containing one or more of Al, N, P, and Sb. Thereby, a light cut layer (absorption layer) can be formed with the semiconductor layer described above with respect to a substance having an absorption peak in the near infrared region such as water and sugar. As a result, a permeable membrane from which quantitative analysis of water, sugar, etc. can be easily obtained can be obtained by comparing with the signal light of the light receiving unit in which the semiconductor layer is not disposed. In this case, the dark current is low because the semiconductor layer is easily lattice matched to the semiconductor stack of the light receiving element array.

  Among the plurality of transmission films, a transmission film having a main transmission wavelength in the visible light region can be included. As a result, a visible light image that is visible to humans, that is, a color appearance can be additionally obtained, and the usefulness can be enhanced.

  The semiconductor substrate used to form the semiconductor multilayer structure including the light receiving layer is removed, and the transmission film whose main transmission wavelength is in the visible light region is combined with other transmission films for epi-down mounting of the semiconductor multilayer structure. It can arrange | position to the entrance plane side of a light receiving element. This prevents light in the near-infrared short wavelength side to visible region from being absorbed before reaching the light receiving unit, thereby avoiding a decrease in sensitivity in the wavelength region.

  Among the plurality of transmission films, a transmission film having a main transmission wavelength of 2.1 μm and a transmission film having a main transmission wavelength of 1.9 μm can be included. As a result, moisture and cellulose can be detected simultaneously.

  The one-dimensional light-receiving element array of the present invention is one of the above-described light-receiving element arrays in which one unit is one-dimensionally arranged with a region corresponding to the plurality of transmission films as a unit when viewed in plan. It is characterized by that. Needless to say, one unit is formed by combining a plurality of pixels or unit light receiving portions.

  By scanning using the one-dimensional array, the one-dimensional mapping information of the measurement target substance can be obtained more easily.

  In the two-dimensional light receiving element array of the present invention, in any one of the light receiving elements described above, an area corresponding to a plurality of transmission films in a plan view is taken as one unit, and the unit is two-dimensionally arranged. Features. In addition, the above-mentioned 1 unit includes a change in the arrangement order of the permeable membranes in an arbitrary direction within the unit, a unit rotated by 180 ° with the center point of the unit as a center of rotation, and a mirror surface on the center plane (The array change 1 unit), and the two-dimensional light receiving element array may be formed by combining the 1 unit and the array change 1 unit.

  With the above configuration, it is possible to easily obtain an in-plane distribution of the measurement target substance, an imaging device, and the like. In addition, a night-vision camera using natural space light can be configured.

  According to the present invention, it is possible to obtain a light receiving element, a one-dimensional array light receiving element, and a two-dimensional array light receiving element that can receive light by distinguishing a plurality of wavelength ranges by a simple mechanism.

(Embodiment 1)
FIG. 1 is a plan view showing a one-dimensional array light receiving element (sensor) 10 of the light receiving element according to Embodiment 1 of the present invention. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is a sectional view taken along line III-III. As shown in FIG. 1, in the light receiving element 10, elongated rectangular transmission films 7 are arranged one-dimensionally. The planar shape of the light receiving element 10 is, for example, a rectangle of 8 mm × 2 mm. At one end or the other end of the permeable membrane 7, a continuous structure of the p-part electrode 12, the wiring electrode 13, and the pad part 14 is arranged alternately. Each transmission film 7 or p-part electrode 12 corresponds to one light-receiving part or unit light-receiving part. In the one-dimensional array, for example, a total of 384 light receiving units are arranged in a row at a pitch of 20 μm.

  FIG. 2 is a cross-sectional view along the longitudinal direction of the transmission film 7 of the light receiving unit. This one light receiving portion has a laminated structure of (n-type InP substrate 1 / n-type InP buffer layer 2 / N-containing InGaAs light receiving layer 3 / InP window layer 4 / diffusion mask pattern 5 / transmission film 7). The p-type region 15 located so as to reach from the InAsP window layer 4 to the GaInNAs light-receiving layer 3 is formed by diffusion introduction of Zn from the opening of the diffusion mask pattern 5 made of a SiN film or the like having a thickness of about 100 nm. Is done.

  A p-type electrode 12 made of, for example, AuZn is provided in the p-type region 15, and an n-type electrode 11 made of, for example, AuGeNi is provided in ohmic contact with the back surface of the InP substrate 1. A wiring electrode 13 is electrically connected to the p-part electrode 12, and the wiring electrode 13 is electrically connected to the pad part 14. The pad portion 14 is connected to a control circuit and an arithmetic circuit by wire bonded.

  In the N-containing InGaAs light receiving layer 3, a pn junction is formed at a position corresponding to the boundary of the p-type region 15, and a reverse bias voltage is applied between the p-part electrode 12 and the n-part electrode 11. Creates a depletion layer. When signal light is incident from the InP window layer 4 side, near-infrared light excites electrons located in the valence band of the depletion layer of the N-containing InGaAs-based light receiving layer 3 to the conduction band, A photocurrent is generated between the electrodes.

  FIG. 3 is a cross-sectional view orthogonal to the longitudinal direction of the permeable membrane 7 of FIG. According to this cross-sectional view, the permeable membrane 7 is composed of three types of multilayer films 7a, 7b, and 7c, and the combinations in the same order are repeated. For example, as shown in FIG. 4, the transmission film 7 a has a wavelength of 2.1 μm as a main transmission wavelength and corresponds to an absorption band of cellulose having a wavelength of 2.1 μm. The permeable membrane 7b has a main transmission wavelength of 1.9 μm and corresponds to an absorption band of water having a wavelength of 1.9 μm. The transmission film 7c is a transmission film having another main transmission wavelength for other substances. For example, it can be used as a detection of background noise as a wavelength that is not an absorption band of cellulose and water.

  According to the one-dimensional array light receiving element 10 described above, for example, the cellulose content and the water content on the surface of the living body can be analyzed with high accuracy along a certain arbitrary direction. Further, by adjusting the main transmission wavelength of the permeable membrane to those other than cellulose and water, the content ratio of cellulose, water and other substances can be obtained with high accuracy.

Since the main transmission wavelength can be arbitrarily designed for the transmission film 7 by using a multilayer film such as SiO ₂ or TiO, an appropriate transmission film can be produced according to the measurement object or the imaging object. Is possible. The effects of the present invention will be described below with examples of specific apparatuses based on computer experiments.

(Embodiment 2)
FIG. 5 is a cross-sectional view of the light receiving element array 10 of the light receiving elements in the second embodiment of the present invention. Except for the part of the transmissive film 7, the structure and manufacturing method of the other parts are the same as those of the light receiving element array of the first embodiment shown in FIG. In the present embodiment, the transmissive film 7 includes a region A in which the semiconductor layer 7s and the dielectric multilayer film 7k are combined, and a region B having only the dielectric multilayer film 7k. As the semiconductor layer 7s, a semiconductor layer including InP itself that is lattice-matched with the InP window layer 4 is newly formed. In the case of epi-down mounting, the InP substrate 1 or the InP buffer layer 2 after the InP substrate is peeled off is left in a convex shape by etching as shown in FIG. 5 according to the pixel (unit light receiving portion). (See Example 3).

  In the region A, for example, a wavelength of 2.1 μm is set as a main transmission wavelength, and it corresponds to an absorption band of cellulose having a wavelength of 2.1 μm. In the region B, the main transmission wavelength is 1.9 μm, which corresponds to the absorption band of water having a wavelength of 1.9 μm. According to the light receiving element array 10 described above, for example, the cellulose content and moisture content on the surface of the living body can be analyzed simultaneously. Further, by adjusting the main transmission wavelength of the permeable membrane to other than water, the content ratio of water and other substances can be obtained with high accuracy.

(Example 1)
In Embodiment 1 of the present invention, an imaging device (two-dimensional light-receiving element array) based on a computer experiment capable of simultaneously imaging with visible light and imaging with cosmic natural light will be described. FIG. 6 is a plan view of the imaging device 10 according to the first embodiment of the present invention as viewed from the light incident side. In the imaging device 10, two types of transmission films 7d and 7e are two-dimensionally arranged in a checkered pattern on the light incident side. The size of the light incident surface is 20 mm wide × 16 mm long, the center distance (pitch) between the adjacent transmissive films 7d, 7e is 25 μm, and the transmissive films 7d, 7e or unit light receiving portions are arranged in a 640 × 512 array. . A combination of the adjacent unit light receiving portions 7d and 7e is a light receiving element array of one unit.

  7 is a cross-sectional view taken along line VII-VII in FIG. In this imaging device 10, epi-down mounting is performed in which the InP window layer 4 or the p-part electrode 12 side is electrically connected to a complementary metal-oxide semiconductor (CMOS) multiplexer by a junction bump 19. Then, the lower part of the InP substrate and the n-type buffer layer is removed, and the semiconductor layer on the light incident surface is constituted by the remaining n-type buffer layer 2a. For this reason, absorption of light in the near-infrared short wavelength side to visible region can be avoided by the lower layer portion of the InP substrate and the n-type InGaAs layer. On the remaining n-type InGaAs layer 2a, transmission films 7d and 7e are arranged so as to follow the pattern of the unit light-receiving portion shown in FIG. As a matter of course, the arrangement pattern of the unit light receiving portions overlaps with the arrangement pattern of the p-type region 15 when seen in a plan view. That is, the p-type region 15 and the p-part electrode 12 correspond to or accompany each of the unit light-receiving parts 7d and 7e.

  The transmission film 7d has a multilayer structure so as to have a high transmittance (main transmission wavelength) at least in the visible range of 400 nm to 750 nm. The transmission film 7e is designed to have a multilayer structure so as to have a high transmittance (main transmission wavelength) at least in the wavelength range 1500 nm to 2000 nm of cosmic natural light. With such a two-dimensional arrangement of the permeable membranes 7d and 7e, imaging with visible light and imaging with cosmic natural light can be performed side by side.

  Next, a method for manufacturing the imaging device shown in FIGS. 6 and 7 will be described. On the InP substrate 1, an n-type InGaAs buffer layer 2, a GaInNAs light-receiving layer 3 and an InP window layer 4 are epitaxially grown sequentially by MBE (Molecular Beam Epitaxy). The wavelength of the N-containing InGaAs-based light receiving layer 3 by photoluminescence (PL) measurement is about 2.0 μm, and the N amount by SIMS (Secondary Ion Mass Spectroscopy) analysis is 1.5%. The lattice constant deviation Δa / a = 0.01, that is, 1% between the InP window layer 4 calculated from the X-ray diffraction result and the GaInNAs light-receiving layer 3 is set to 1%.

Thereafter, a two-dimensional array is formed by vapor deposition, photolithography, and etching so that the pattern shown in FIG. 6 is obtained. That is, a Zn diffusion mask pattern 5 is formed, Zn is diffused and introduced to form a p-type region 15 for each unit light receiving portion, and a p-type electrode 12 is formed so as to make ohmic contact with each p-type region 15. Next, the protective film 6 is formed. A protective film 9 is provided on the exposed end surface of the semiconductor laminate. The n-part electrode 11 is formed in the form of one continuous conductor common to the plurality of p-part electrodes 12 so as to make ohmic contact with the remaining n-type buffer layer 2a. Further, in order to suppress absorption in the visible region to the near infrared region, the lower layers of the InP substrate and the n-type InGaAs buffer layer are removed by polishing and etching. The remaining n-type InGaAs layer 2a has a thickness of 0.1 μm. The semiconductor multilayer structure thus formed is epi-down mounted on the CMOS multiplexer 21 using bonding bumps 19 as shown in FIG. Two types of multilayer transmission films 7d and 7e provided on the light incident surface are produced and arranged in the pattern shown in FIG. 6 so that the transmission band includes the visible region or the cosmic natural light region. The multilayer permeable membrane 7d has a nine-layer structure with a combination of SiO ₂ / TiO ₂ . The total thickness of SiO ₂ is 1875 nm, and the total thickness of TiO ₂ is 400 nm. The multilayer transmission film 7e has a 31-layer structure with a combination of SiO ₂ / Si. The total thickness of SiO ₂ is 1360 nm and the total thickness of Si is 525 nm.

  The transmittance of the transmissive films 7d and 7e with respect to the wavelength is shown in FIGS. The transmissive film 7d transmits visible light but does not transmit the cosmic natural light band. That is, only visible light can be imaged. On the other hand, the transmissive film 7e transmits natural light from the universe but does not transmit visible light, and only the cosmic natural light can be imaged. According to such a configuration, a single imaging device can be used to simultaneously capture the visible light image and the night vision image, or the visible light imaging and the night vision imaging can be used separately. For example, it is always used as a night vision camera for monitoring, and when a person image (suspicious person) is captured in the monitoring, illumination is turned on, and at the same time, features such as a human phase can be imaged in detail with visible light. It can also be used as a surveillance camera during night driving of an automobile to monitor oncoming vehicles and roads with space natural light and to judge red and blue traffic signals from a visible image.

In addition to the above example, by changing the transmission band pattern of the multilayer transmission film, it can be used for simultaneous detection of substance components having an absorption peak in the near infrared band in parallel with imaging. For example, it is possible to detect an appearance image (such as a wound) and sugar content of a fruit. For the multilayer transmission film, TiO ₂ , SiO ₂ , SiON, Si, amorphous Si, Al ₂ O ₃ , Zr ₂ O ₃ , or other inorganic oxides may be used.

  FIG. 10 shows the detection wavelength in the near-infrared region of the imaging device 10 in the present embodiment. FIG. 10 also shows the wavelength distribution of natural light from the universe, and it can be seen that the above-mentioned wavelength region portion of cosmic natural light is almost completely included. For this reason, as described above, it is possible to capture a night vision image by the natural space light with high sensitivity. FIG. 10 shows a line that decreases from the short-wavelength side of the near infrared region to the visible region, and this schematically shows that the above-described n-type InGaAs layer 2a absorbs and the efficiency decreases. .

(Example 2)
FIG. 11 is a plan view showing the light receiving element array 10 according to the computer experiment of the second embodiment of the present invention. 12 is a cross-sectional view taken along line XII-XII in FIG. 11, and FIG. 13 is a cross-sectional view taken along line XIII-XIII. Three kinds of transmission films 7f, 7g, and 7h are arranged on the light incident surface of the light receiving element array 10. From the p-type region 15 corresponding to the region covered by these permeable membranes, the p-part electrode 12 that is in ohmic contact with the p-type region 15 is drawn out, passed through the wiring electrode 13 and the pad part 14, a control circuit or the like by a bonding wire or the like. To be contacted. The semiconductor laminated structure is a configuration of a normal photodiode, and is laminated with (n-type InP substrate 1 / n-type InP buffer layer 2 / N-containing InGaAs light receiving layer 3 / InP window layer 4 / Zn diffusion mask pattern 5). Has been. The Zn diffusion mask pattern 5 is provided also as a protective film. An n-part electrode 11 is provided on the back surface of the n-type InP substrate 1 and is paired with the p-part electrode 12.

  The manufacturing method of the above photodiode structure is as follows. First, an n-type InP buffer layer 2, a GaInNAs light-receiving layer 3, and an InP window layer 4 are sequentially epitaxially grown on the S-doped n-type InP substrate 1 by MBE. The center wavelength of PL light emission of the GaInNAs light receiving layer 3 is preferably 2.2 μm. The N amount of the GaInNAs light receiving layer 3 by SIMS analysis is 3%. The lattice constant deviation (Δa / a) between InP and GaInNAs light-receiving layer 3 calculated from the X-ray diffraction result is preferably 0.01.

Thereafter, a Zn diffusion mask pattern 5 is formed by vapor deposition, photolithography and etching. Next, Zn is diffused and introduced from the opening of the Zn diffusion mask pattern 5, and the p-type region 15 is formed so as to reach the GaInNAs light-receiving layer 3 through the InP window layer 4. Next, the multilayer transmission films 7f, 7g, and 7h are sequentially formed by vapor deposition, photolithography, and etching. The multilayer permeable membrane had a seven-layer structure with a combination of SiO ₂ / Si. The total film thickness of SiO ₂ and Si in the permeable films 7f, 7g, and 7h is as follows.
(Transmission film 7f): SiO ₂ 1500 nm, Si 990 nm
(Transparent film 7 g): SiO ₂ 1500 nm, Si 875 nm
(Transparent film 7h): SiO ₂ 1500 nm, Si 810 nm

  The transmittances of the transmissive films 7f, 7g, and 7h with respect to the wavelength are shown in FIGS. 14, 15, and 16, respectively. The permeable membrane 7f has a high transmittance only for the absorption wavelength of cellulose. The transmission film 7g has a high transmittance only in the wavelength region corresponding to the water absorption band (see FIG. 4). The transmission film 7h has a high transmittance only in a wavelength region that does not correspond to either absorption wavelength, that is, a wavelength region that corresponds to the background.

  According to said structure, the complicated structure like the method shown in patent document 1 is not required. That is, in the above document, a filter that selectively transmits the wavelength band of infrared rays (including the near-infrared region) is arranged at an equal distance from the center of the disc that rotates around the central axis, and the disc is rotated. While irradiating the disc with light, the object (cellulose or the like) is detected in synchronization with the passing timing of each filter. Regardless of such a complicated mechanism, in the above-described second embodiment, signals in the three wavelength regions are simultaneously irradiated to extract signals from the p-part electrodes 12 corresponding to the transmissive films 7f, 7g, and 7h. Can do. Alternatively, one light source having a wide wavelength band such as a halogen lamp may be used to irradiate the entire light receiving element array 10.

  Using the light receiving element array 10 described above, for example, a paper brand inspection apparatus can be configured. The light receiving element array 10 in this embodiment includes an arithmetic circuit in the control circuit unit, and the arithmetic circuit is accompanied by a storage means, and the storage means is prepared for each brand whose moisture content and cellulose weight are known. The calibration curve is stored. By obtaining a photocurrent corresponding to the permeable membrane having the transmission characteristics of FIGS. 14 to 16, it is possible to accurately associate with the calibration curve, and to specify the brand of the paper.

The above light receiving element array is merely an example. By changing the configuration of the multilayer permeable membrane, it can be used for simultaneous detection of other substances having absorption peaks in the near-infrared band, such as blood sugar, protein, sugar, starch, and lipid. For the multilayer transmission film, TiO ₂ , SiO ₂ , SiON, Si, amorphous Si, Al ₂ O ₃ , Zr ₂ O ₃ , or other inorganic oxides may be used.

(Example 3)
In Example 3 of the present invention, a two-dimensional light-receiving element array in which two types of permeable membranes are provided and the distribution of cellulose and water can be analyzed in parallel will be described. FIG. 17 is a plan view of the two-dimensional light receiving element array 10 according to the third embodiment of the present invention as viewed from the light incident side. In the two-dimensional light receiving element array 10, two types of regions A and B are two-dimensionally arranged in a checkered pattern on the light incident side. As will be described later, the transmission film is formed of a semiconductor layer and a multilayer dielectric layer in the region A, and the region B is formed of the same multilayer dielectric layer as the region A. The size of the light incident surface is the same as in Example 1, 20 mm wide × 16 mm long, the center distance (pitch) between the adjacent regions A and B is 25 μm, and the region A, B or the unit light receiving unit is 640 × 512. Becomes an array of A combination of the regions A and B of the adjacent unit light-receiving portions is a unit of light-receiving element array.

  18 is a cross-sectional view taken along line XVIII-XVIII in FIG. The imaging device 10 is characterized in that the transmissive film 7 is formed of a semiconductor layer 7s left in a convex shape of the n-type layer 2a and a dielectric multilayer film 7k formed over the entire surface including the semiconductor layer 7s. Have. Naturally, the semiconductor layer 7s is lattice-matched with the underlying layer. The structure of the light receiving element array other than the transmissive film is the same as that of the light receiving element array of Example 1 (see FIG. 7). That is, epi-down mounting is performed in which the InP window layer 4 or the p-part electrode 12 side is electrically connected to a complementary metal-oxide semiconductor (CMOS) multiplexer by the bonding bumps 19. The buffer layer on the InP substrate 1 is GaInNAs. In this embodiment, the lower layer portion of the n-type GaInNAs buffer layer 2 is partially removed, leaving a convex n-type GaInNAs layer 7s corresponding to the region A. A dielectric multilayer film 7k covers the entire surface including the n-type GaInNAs semiconductor layer 7s. In the region A, light of a predetermined wavelength can be cut because of the GaInNAs convex portion 7s.

  Next, a method for manufacturing the imaging device shown in FIGS. 17 and 18 will be described. On the InP substrate 1, an n-type GaInNAs buffer layer 2, a GaInNAs light-receiving layer 3, and an InP window layer 4 are sequentially epitaxially grown by MBE (Molecular Beam Epitaxy). The wavelength of the N-containing InGaAs-based light-receiving layer 3 by photoluminescence (PL) measurement is about 2.2 μm, and the N amount by SIMS (Secondary Ion Mass Spectroscopy) analysis is about 3%. The lattice constant deviation Δa / a = 0.01, that is, 1% between the InP window layer 4 calculated from the X-ray diffraction result and the GaInNAs light-receiving layer 3 is set to 1%. The absorption edge wavelength of the GaInNAs buffer layer 2 is about 2.0 μm, and the N amount by SIMS analysis is about 2%. Similarly, the lattice constant deviation Δa / a between the GaInNAs buffer layer 2 and the InP window layer 4 is set to 0.01, that is, 1%.

  Thereafter, a two-dimensional array is formed by vapor deposition, photolithography, and etching so that the pattern shown in FIG. 17 is obtained. That is, a Zn diffusion mask pattern 5 is formed, Zn is diffused and introduced to form a p-type region 15 for each unit light receiving portion, and a p-type electrode 12 is formed so as to be in ohmic contact with each p-type region 15. Next, the protective film 6 is formed. The n-part electrode 11 is formed in the form of one continuous conductor common to the plurality of p-part electrodes 12 so as to make ohmic contact with the remaining n-type buffer layer 2a. Similarly, the region other than the n-part electrode 11 formation region is covered with a mask, and the n-type GaInNAs buffer layer 2a is exposed only by wet etching in the n-part electrode formation region. In wet etching, the end face is covered with a protective film 9, and the n-part electrode 11 is provided in ohmic contact with the n-type GaInNAs buffer layer 2a.

Thereafter, the epitaxial layer is attached to a glass plate with the top of the epitaxial layer facing down, and the InP substrate is peeled off by polishing and wet etching. In the semiconductor layer 7s that cuts visible light, a predetermined portion is masked with respect to the GaInNAs buffer layer 2, and the other portions are removed by wet etching. After removing the mask, seven combined composite layers as the dielectric multilayer film 7k are repeatedly formed on the entire back surface. Regarding the total film thickness of each of SiO ₂ and Si, the total thickness of the SiO ₂ layer is preferably 1400 nm and the total thickness of the Si layer is 825 nm. The two-dimensional light receiving element array produced as described above is connected to the CMOS as shown in FIG.

  FIG. 19 and FIG. 20 show the results of computer experiments of the transmittance with respect to the wavelengths of the dielectric multilayer film 7k and the GaInNAs semiconductor layer 7s. In the region B having only the dielectric multilayer film 7k, light in both absorption peaks of water and cellulose is transmitted. On the other hand, in the region A where both the dielectric multilayer film 7k and the semiconductor layer 7s are arranged, only light in the absorption peak band of cellulose is transmitted.

  With the configuration described above, as in the apparatus shown in Patent Document 1, there is no need for the trouble or system of sequentially irradiating light of each wavelength of water or cellulose absorption band and detecting in synchronization with the timing. . In the two-dimensional light receiving element array 10 of the present embodiment, both the light of multiple wavelengths are applied at the same time, or the signals detected from the regions A and B are simultaneously used by using a light source of a wide wavelength band such as a halogen lamp. Can be detected. For cellulose, the signal from region A may be read, and for water, the signal for region A may be subtracted from the signal for region B. Further, in order to eliminate the influence of the background as in Patent Documents 1 and 2, an InP lattice-matched GaInNAs layer having an absorption edge in the 1.85 μm band is also grown, and the GaInNAs layer is obtained by the same method as described above. An area including can also be provided. In addition, since the two-dimensional array is used, the in-plane distribution of the object can be captured as the substance detection.

  The above two-dimensional light receiving element array is only an example. Simultaneous detection of several substances such as blood sugar, protein, sugar, starch, lipid, etc., which have other absorption peaks in the near infrared band by changing the configuration of the dielectric multilayer film and semiconductor layer lattice-matched to InP Can be used.

As a film used for the dielectric multilayer film, TiO ₂ , SiO ₂ , SiON, Si, amorphous Si, Al ₂ O ₃ , Zr ₂ O ₃ , and other inorganic oxides can be used. As a semiconductor layer (light cut layer) that is lattice-matched to InP and a semiconductor of the light receiving layer, an effect of increasing the wavelength, adding N, Sb, or an effect of shortening the wavelength is achieved based on InGaAs. What added Al and P to play may be used. If the In composition is changed according to the element to be added, lattice matching with the InP substrate can be achieved. Besides, In, Al, or Ga as a group III element and As, P, N, or Sb as a group V element may be combined and lattice matched to the InP substrate. Depending on the combination of the above elements, the detection wavelength band of interest can be freely selected and selected.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples of the present invention disclosed above are merely examples, and the scope of the present invention is the implementation of these inventions. It is not limited to the form. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the present invention, light having a plurality of different wavelength ranges can be received with high sensitivity by a simple mechanism, so that the constituent ratio peculiar to each substance can be detected with high accuracy. Further, by combining with a visible light region, a combination of a night vision image and a visible image is possible, so that it can be used for various monitoring devices.

It is a top view which shows the light receiving element array in Embodiment 1 of this invention. It is sectional drawing which follows the II-II line of the light receiving element array of FIG. It is sectional drawing which follows the III-III line of the light receiving element array of FIG. It is a figure which shows the water absorptivity and the transmittance | permeability of each permeable film with respect to a wavelength. It is sectional drawing which shows the light receiving element array in Embodiment 2 of this invention. It is a top view which shows the two-dimensional light receiving element array (imaging device) in Example 1 of this invention. It is sectional drawing which follows the VII-VII line of the light receiving element array of FIG. It is a figure which shows the transmittance | permeability of one permeable film of Example 1 with respect to a wavelength. It is a figure which shows the transmittance | permeability of the other permeable film of Example 1 with respect to a wavelength. It is a figure which shows the detection wavelength range in the near infrared region of Example 1 of this invention. It is a top view which shows the light receiving element array in Example 2 of this invention. It is sectional drawing which follows the XII-XII line | wire of the light receiving element array of FIG. It is sectional drawing which follows the XIII-XIII line of the light receiving element array of FIG. It is a figure which shows the transmittance | permeability of the 1st transmission film of Example 2 with respect to a wavelength. It is a figure which shows the transmittance | permeability of the 2nd permeable film of Example 2 with respect to a wavelength. FIG. 6 is a diagram showing the transmittance of the third (last) permeable membrane of Example 2 with respect to wavelength. 6 is a plan view showing a two-dimensional light receiving element array (imaging device) in Embodiment 3. FIG. It is sectional drawing which follows the XVIII-XVIII line of FIG. It is a figure which shows the transmittance | permeability of a dielectric multilayer film with respect to a wavelength. It is a figure which shows the transmittance | permeability of a semiconductor layer with respect to a wavelength.

Explanation of symbols

1 InP substrate, 2 buffer layer, 2a remaining buffer layer, 3 GaInNAs light receiving layer, 4 InP window layer, 5 Zn diffusion mask pattern, 6 protective film, 7, 7a to 7h transmission film, 7k dielectric combined with semiconductor layer Multilayer film, semiconductor layer in 7s transmission film, 9 protective film, 10 light receiving element, 11 n part electrode, 12 p part electrode, 13 wiring electrode, 14 pad part, 15 p type region, 19 junction bump, 21 CMOS multiplexer.

Claims (17)

A light receiving element array for detecting light incident from the incident surface side,
A compound semiconductor light-receiving layer;
A plurality of transmission films disposed on the incident surface side of the light receiving layer and having different transmission wavelength bands;
A light receiving element array, comprising: a plurality of electrodes for separately capturing currents generated in a plurality of light receiving portions in the light receiving layer corresponding to the plurality of transmission films.   2. The light receiving element array according to claim 1, wherein the transmissive film is stacked on a stacked body including the light receiving layer of the compound semiconductor and is formed of a single layer or a plurality of layers.   3. The light receiving element array according to claim 1, wherein a maximum transmission wavelength of each of the plurality of transmission films is in a range of 1.65 μm to 3 μm.   The light receiving element array according to any one of claims 1 to 3, wherein the light receiving layer is any one of InGaAs, GaInNAs, GaInNAsSb, and GaInNAsP.   The light receiving element array according to claim 1, wherein the light receiving layer is a semiconductor layer lattice-matched to InP.   The light receiving element array according to claim 1, wherein each of the plurality of transmission films is a multilayer film.   The multilayer film is formed of two or more layers of inorganic material, oxide, nitride, oxynitride, fluoride, sulfide, and a composite thereof, respectively. The light receiving element array according to 1.   The light-receiving element array according to claim 1, wherein the transmission film is a combination of a dielectric multilayer film and a semiconductor layer.   The semiconductor layer included in the transmissive film is located on the incident surface side of the stacked body including the light receiving layer, at a position corresponding to one or more of the plurality of light receiving portions, the semiconductor layer and the semiconductor layer 9. The light receiving element array according to claim 8, wherein the plurality of transmission films are formed by covering the surface layer of the stacked body on which the semiconductor layer is not provided with the dielectric multilayer film. .   10. The light receiving element array according to claim 8, wherein the semiconductor layer included in the transmission film is lattice-matched to InP and has an absorption edge wavelength shorter than that of the light receiving layer.   The light receiving layer and the semiconductor layer included in the transmission film include one or more of group III elements In, Al, and Ga, and one or more of group V elements P, As, Sb, and N. The light-receiving element array according to claim 8, wherein the light-receiving element array is a group III-V compound semiconductor.   The semiconductor layer included in the light receiving layer and the transmissive film is an InGaAs layer, or one or more of Al, N, P, and Sb are contained in InGaAs. The light receiving element array according to any one of claims 8 to 11.   The light receiving element array according to claim 1, wherein a transmission film having a main transmission wavelength in a visible light region is included in the plurality of transmission films.   The semiconductor substrate used to form the semiconductor multilayer structure including the light receiving layer is excluded, and the transmission film having the main transmission wavelength in the visible light region is epi-down mounted on the semiconductor multilayer structure together with other transmission films. The light receiving element array according to claim 13, wherein the light receiving element array is disposed on an incident surface side of the light receiving element.   The transmissive film having a main transmission wavelength of 2.1 μm and a transmissive film having a main transmission wavelength of 1.9 μm are included in the plurality of transmission films. Light receiving element array.   16. The one-dimensional light receiving device according to claim 1, wherein a region corresponding to the plurality of transmission films is defined as one unit, and one unit is arranged one-dimensionally. Element array. The light receiving element array according to any one of claims 1 to 15, wherein a region corresponding to the plurality of transmission films is defined as one unit, and the unit is two-dimensionally arranged. Element array.

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