Semiconductor light detecting element

Abstract

The light detecting element (10) of the present application includes: a semiconductor substrate (16) having a main surface (16a) on which a detected light is incident, and a back surface (16b) opposite to the main surface (16a), one or more light detecting regions (11) on the main surface (16a) side which generate charges in an amount corresponding to a light intensity of the detected light; and a light absorbing film (13) provided on the back surface (16b) of the semiconductor substrate (16). The light absorbing film (13) includes: a metal layer, i.e., a reflection layer (133), a resonance layer (132) provided between the reflection layer (133) and the semiconductor substrate (16), and a light absorbing layer (131) provided between the resonance layer (132) and the semiconductor substrate (16). In at least one of a wavelength of the detected light and a wavelength of spontaneous light generated in the light detecting region (11), a light transmittance in an inside of the resonance layer (132) is greater than a light transmittance in an inside of the light absorbing layer (131), and a light reflectance of a surface of the reflection layer (133) is greater than a light reflectance of a surface of the resonance layer (132). Thus, a semiconductor light detecting element capable of reducing reflection of light on the back surface of the semiconductor substrate is realized.

Description

Technical Field

[0001] This disclosure relates to a semiconductor optical detection element. Background Technology

[0002] Patent Document 1 discloses a technology related to a solid-state imaging element. This solid-state imaging element includes a sensor portion formed on the surface of a semiconductor substrate, which performs photoelectric conversion. A low-reflection film with low reflectivity to infrared light is formed on the back side of the semiconductor substrate. Patent Document 2 discloses a technology related to a silicon photomultiplier tube (SiPM). This SiPM includes multiple cells, each containing an avalanche photodiode.

[0003] [Existing Technical Documents]

[0004] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2007-305675

[0006] [Patent Document 2] U.S. Patent Application Publication No. 2013 / 0099100 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] As a semiconductor photodetector, there is a device such as a photodiode in which a photodetector region is formed on the surface of a semiconductor substrate. In such a semiconductor photodetector, when the light to be detected is incident from the surface side of the semiconductor substrate, a portion of it is not absorbed in the photodetector region and passes through the photodetector region. Then, it is reflected from the back side of the semiconductor substrate and reaches the photodetector region again, where it is absorbed.

[0009] Such behavior of the detected light causes the following problem: compared to detected light that is absorbed immediately after being incident on the light detection region, detected light that is reflected from the back of the semiconductor substrate and then absorbed by the light detection region experiences a delay in its absorption timing. Therefore, the waveform of the detection signal obtained by amplifying the charge output from the light detection region is temporally stretched, resulting in a decrease in temporal resolution.

[0010] Furthermore, in the case where a semiconductor photodetector has multiple pixels (or cells) each having a photodetection area, when the detected light is reflected from the back side of the semiconductor substrate of a certain pixel (or cell), if the detected light is absorbed by the photodetection area of ​​an adjacent pixel (or cell), crosstalk occurs between adjacent pixels (or adjacent cells). This crosstalk is not limited to the detected light; it also occurs in the light generated in the photodetection area (self-emission). Therefore, to improve the spatial and temporal resolution of the semiconductor photodetector, it is ideal to reduce the reflection of light from the back side of the semiconductor substrate.

[0011] The purpose of this invention is to provide a semiconductor photodetector that can reduce light reflection from the back side of a semiconductor substrate.

[0012] [Technical means to solve the problem]

[0013] The present invention relates to a semiconductor photodetector. The semiconductor photodetector comprises: a semiconductor substrate having a main surface on which a light to be detected is incident, and a back surface opposite to the main surface, and having one or more photodetector regions on the main surface side that generate an amount of charge corresponding to the light intensity of the light to be detected; and a light absorption film disposed on the back surface of the semiconductor substrate; wherein the light absorption film has a multilayer structure comprising a metal layer (i.e., a reflective layer), a resonant layer disposed between the reflective layer and the semiconductor substrate, and a light absorption layer disposed between the resonant layer and the semiconductor substrate, wherein at least one of the wavelength of the light to be detected and the wavelength of self-emission generated in the photodetector regions is present, the transmittance inside the resonant layer is greater than the transmittance inside the light absorption layer, and the light reflectance of the surface of the reflective layer is greater than the light reflectance of the surface of the resonant layer.

[0014] In this semiconductor photodetector, an amount of charge corresponding to the intensity of the light being detected incident from the main surface of the semiconductor substrate is generated in the photodetection region. Thus, the amount of incident light can be detected electrically. The light being detected that is not absorbed in the photodetection region reaches a light-absorbing film disposed on the back side of the semiconductor substrate. When self-emission occurs in the photodetection region, this self-emission also reaches the light-absorbing film.

[0015] The light-absorbing film of this semiconductor photodetector has a multilayer structure comprising a reflective layer, a resonant layer, and a light-absorbing layer. A portion of the light incident on the light-absorbing film is immediately absorbed in the light-absorbing layer. Light not absorbed by the light-absorbing layer passes through the light-absorbing layer and enters the resonant layer. Then, the light entering the resonant layer undergoes multiple reflections between the interface between the light-absorbing layer and the resonant layer, and between the interface between the resonant layer and the reflective layer, while being gradually absorbed within the light-absorbing layer.

[0016] Therefore, according to this light absorption film, extremely high absorption efficiency can be achieved compared to a light absorption film comprising a single layer. Thus, according to the aforementioned semiconductor photodetector element, light reflection from the back side of the semiconductor substrate can be effectively reduced, thereby suppressing the reduction in temporal resolution and reducing crosstalk between adjacent pixels (adjacent units).

[0017] [The effects of the invention]

[0018] The semiconductor photodetector according to an embodiment of the present invention can reduce light reflection from the back side of a semiconductor substrate. Attached Figure Description

[0019] Figure 1 This is a partial cross-sectional view of a light detection device according to one embodiment.

[0020] Figure 2 A schematic plan view of the semiconductor photodetector element in a photodetector device.

[0021] Figure 3 This is a circuit diagram of a photodetector.

[0022] Figure 4 Figures (a) to (c) are used to illustrate the manufacturing process of a light detection device according to one embodiment.

[0023] Figure 5 Figures (a) to (c) are used to illustrate the manufacturing process of a light detection device according to one embodiment.

[0024] Figure 6 (a) and (b) are diagrams illustrating the manufacturing process of a light detection device according to one embodiment.

[0025] Figure 7 (a) and (b) are diagrams illustrating the manufacturing process of a light detection device according to one embodiment.

[0026] Figure 8 A diagram illustrating the cross-sectional structure of the laminate created for verification purposes.

[0027] Figure 9 A diagram illustrating the cross-sectional structure of the laminate created for verification purposes.

[0028] Figure 10 The curve of a voltage signal waveform containing crosstalk is schematically shown.

[0029] Figure 11 To illustrate the curve of the dark count rate measured by changing the threshold of the comparator when the sample is placed in a dark chamber.

[0030] Figure 12The curves show the relationship between the reverse bias voltage and the crosstalk probability for each sample in the embodiment.

[0031] Figure 13 Curves showing the dark current characteristics of each sample in the embodiments caused by self-emission are provided.

[0032] Figure 14 A diagram illustrating the cross-sectional structure of a light-absorbing film.

[0033] Figure 15 The diagram is intended to schematically show the configuration of a light-absorbing film disposed on the back side of a semiconductor substrate.

[0034] Figure 16 A partial cross-sectional view showing the structure of the light detection element in the first variation example.

[0035] Figure 17 A partial cross-sectional view showing the structure of the light detection element in the second variation example.

[0036] Figure 18 A partial cross-sectional view showing the structure of the light detection element in the third variation example.

[0037] Figure 19 A partial cross-sectional view showing the structure of the optical detection element in the fourth variation example.

[0038] Figure 20 A partial cross-sectional view showing the structure of the light detection element in the fifth variation example.

[0039] Figure 21 A partial cross-sectional view showing the structure of the light detection element in the sixth variation example.

[0040] Figure 22 A partial cross-sectional view showing the structure of the light detection element in the seventh variation example.

[0041] Figure 23 A partial cross-sectional view showing the structure of the optical detection element in the 8th variation example.

[0042] Figure 24 A partial cross-sectional view showing the structure of the light detection element in the 9th variation example. Detailed Implementation

[0043] Hereinafter, embodiments of the semiconductor photodetector element will be described in detail with reference to the accompanying drawings. Furthermore, in the description of the drawings, the same symbols are used to denote the same elements, and repeated descriptions are omitted. The present invention is not limited to these examples.

[0044] Figure 1 This is a partial cross-sectional view of the light detection device 1A of this embodiment. Figure 2This is a schematic plan view of the semiconductor photodetector element (hereinafter referred to as photodetector element) 10 included in the photodetector device 1A. Figure 3 This is the circuit diagram of the photodetector 1A.

[0045] Optical detection device 1A, such as Figure 1 As shown, the system includes: a photodetector 10, a glass substrate 31, and a mounting substrate 35. The mounting substrate 35 is disposed opposite to the photodetector 10. The glass substrate 31 is disposed opposite to the photodetector 10. The photodetector 10 is disposed between the mounting substrate 35 and the glass substrate 31.

[0046] The photodetector 10 in this embodiment is a photodiode array. The photodetector 10 has a rectangular semiconductor substrate 16 when viewed from above. The semiconductor substrate 16 includes a main surface 16a and a back surface 16b facing away from each other. Detected light is incident on the main surface 16a. In one example, the semiconductor substrate 16 is a Si substrate or an InP substrate. The thickness of the semiconductor substrate 16 (the distance between the main surface 16a and the back surface 16b) is, for example, 1 μm or more and 1000 μm or less.

[0047] The photodetector element 10 includes a plurality of photodetector regions 11 formed on a semiconductor substrate 16. These photodetector regions 11 generate an amount of charge corresponding to the light intensity of the detected light. Quenching resistors 21 are connected in series in each photodetector region 11. One photodetector region 11 constitutes a unit in the photodetector element 10.

[0048] Each photodetector region 11 is connected in parallel, with each region connected in series with a quenching resistor 21, and is reverse-biased from the power supply. The output current from the photodetector region 11 is detected by the signal processing unit 36, described later. Figure 2 In order to clarify the structure, some characters are omitted. Figure 1 The description of the insulating film 41 shown.

[0049] Each photodetector region 11 has a semiconductor region 14 of a second conductivity type (e.g., p-type). The semiconductor region 14 is formed on the main surface 16a side of the semiconductor substrate 16. The planar shape of the semiconductor region 14 is, for example, a polygon (an octagon in this embodiment). In addition, the semiconductor substrate 16 has a semiconductor region 12 of a first conductivity type (e.g., n-type). The semiconductor region 12 occupies the area in the semiconductor substrate 16 other than the semiconductor region 14.

[0050] Light detection area 11 Figure 2As shown, the semiconductor substrate 16 has electrodes 22 and 23 respectively disposed on the main surface 16a side. Electrode 22 is electrically connected to the semiconductor region 14. Electrode 23 is formed on the semiconductor substrate 16 outside the semiconductor region 14 when viewed from the main surface 16a side via an insulating film 41. Additionally, the photodetector region 11 has electrodes (not shown) and 24 respectively disposed on the back surface 16b side of the semiconductor substrate 16, which are electrically connected to the semiconductor substrate 16. Electrode 24 is formed on the back surface 16b of the semiconductor substrate 16 via an insulating film 42.

[0051] The photodetector element 10 has a quenching resistor 21 formed on a semiconductor substrate 16 outside the semiconductor region 14, separated by an insulating film 41, for each photodetector region 11. That is, the quenching resistor 21 is disposed on the main surface 16a side of the semiconductor substrate 16. One end of the quenching resistor 21 is connected to an electrode 22, and the other end is connected to an electrode 23. The quenching resistor 21 has a higher resistivity than the electrode 22 to which it is connected. The quenching resistor 21 may contain, for example, polycrystalline silicon. As a method for forming the quenching resistor 21, CVD (Chemical Vapor Deposition) can be used.

[0052] The photodetector element 10 includes a plurality of through electrodes 26. Each through electrode 26 is disposed for each of the photodetector regions 11. The through electrodes 26 are formed through the space between the main surface 16a and the back surface 16b. That is, the through electrodes 26 are disposed within a through hole 15 that penetrates the semiconductor substrate 16. The inner surface of the through hole 15 extends in the thickness direction of the semiconductor substrate 16 (i.e., in a direction perpendicular to the main surface 16a and the back surface 16b).

[0053] An insulating film 42 is also formed within the through-hole 15. A through-electrode 26 is disposed on the inner surface and bottom surface of the through-hole 15, separated by the insulating film 42. One end of the through-electrode 26 is connected to electrode 23, and is electrically connected to the semiconductor region 14 of the photodetector region 11 via electrode 23, quenching resistor 21, and electrode 22. The other end of the through-electrode 26 is connected to electrode 24.

[0054] The through-electrode 26 is disposed in the region between the light detection regions 11 when viewed from above. In this embodiment, the light detection regions 11 are arranged in two dimensions in M ​​rows in a first direction and in N columns in a second direction orthogonal to the first direction (M and N are natural numbers). The through-electrode 26 is formed in the region surrounded by the four light detection regions 11. Since the through-electrode 26 is provided for each light detection region 11, it is arranged in two dimensions in M ​​rows in the first direction and in N columns in the second direction.

[0055] Electrodes 22, 23, 24 and through electrode 26 comprise metal. Examples of metals used for electrodes 22, 23, 24 and through electrode 26 include single-layer films of Al, Ti, Cu, Ni, AlCu, etc., or multilayer films of Al / Ni, Al / Ti / Cu, Ti / Cu, Ti / Cu / Ni, Ti / Cu / Ti, etc. Furthermore, the designation A / B / C indicates that layers A, B, and C are sequentially stacked starting from the semiconductor substrate 16 side.

[0056] When the semiconductor substrate 16 is an InP substrate, AuGe / Ni and other materials are commonly used as electrode materials. Depending on the process design, electrode 24 and through electrode 26 can be formed integrally. Sputtering can be used as the method for forming electrodes 22, 23, 24 and through electrode 26.

[0057] When using Si, group 3 elements such as boron are used as p-type impurities, while group 5 elements such as nitrogen, phosphorus, or ascorbate are used as n-type impurities. Even if the n-type and p-type conductivity types of a semiconductor are interchanged, the device can still function. These impurities can be added using diffusion or ion implantation.

[0058] As materials for insulating films 41 and 42, insulating silicon compounds such as SiO2, SiN, or SiO, insulating metal oxides such as Al2O3 or TiO2, or insulating resins can be used. As methods for forming insulating films 41 and 42, in the case where insulating films 41 and 42 contain SiO2, thermal oxidation or CVD methods can be used.

[0059] In the above-described structure, a photodiode (e.g., an avalanche photodiode) serving as the light detection region 11 is formed by constructing a pn junction between the n-type semiconductor region 12 and the p-type semiconductor region 14. The semiconductor region 12 is electrically connected to an electrode (not shown) formed on the back side 16b, and the semiconductor region 14 is electrically connected to electrode 22. A quenching resistor 21 is connected in series with respect to the light detection region 11 (see reference). Figure 3 ).

[0060] When each photodetector region 11 is an avalanche photodiode, each photodetector region 11 operates in Geiger mode. In Geiger mode, a reverse voltage (reverse bias) larger than the breakdown voltage of the photodetector region 11 is applied between the anode and cathode of the photodetector region 11. That is, a negative potential V1 is applied to the anode, and a positive potential V2 is applied to the cathode. The polarities of these potentials are relative, and one potential can also be set to ground. The anode is a p-type semiconductor region 14, and the cathode is an n-type semiconductor region 12.

[0061] When photons of the detected light are incident on the photodetector region 11, photoelectric conversion occurs inside the semiconductor substrate 16, generating photoelectrons. In the vicinity of the pn junction interface of the semiconductor region 14, avalanche multiplication occurs, and the amplified charge carriers flow towards the electrode 22 formed on the main surface 16a of the semiconductor substrate 16. That is, when photons are incident on any unit (photodetector region 11) of the photodetector element 10, electron multiplication occurs after photoelectric conversion, and a current signal is extracted from the electrode 24.

[0062] The photodetector 10 includes a light-absorbing film 13. The light-absorbing film 13 is disposed on the back surface 16b of the semiconductor substrate 16, between the back surface 16b of the semiconductor substrate 16 and the insulating film 42. The light-absorbing film 13 is provided to absorb the detected light that is not absorbed by the photodetector region 11 and / or the self-emission generated within the photodetector region 11. The light-absorbing film 13 has a multilayer structure including a light-absorbing layer 131, a resonant layer 132, and a reflective layer 133.

[0063] A light-absorbing layer 131 is disposed between the resonant layer 132 and the semiconductor substrate 16. The thickness of the light-absorbing layer 131 is in the range of several nm to several μm. The resonant layer 132 is disposed between the reflective layer 133 and the semiconductor substrate 16, specifically between the reflective layer 133 and the light-absorbing layer 131. The thickness of the resonant layer 132 is in the range of several nm to several hundred μm.

[0064] In one example, the optical thickness of the resonant layer 132 is an integer multiple of one-quarter of the wavelength λ1 of the detected light or the wavelength λ2 of the self-emission generated in the light detection region 11. Alternatively, the optical thickness of the resonant layer 132 may be within ±20% of an integer multiple of λ1 / 4 or λ2 / 4. The wavelength λ1 of the detected light is in the range from the visible band to the near-infrared band, for example, from 350 nm to 1200 nm. In the case where the light detection region 11 is an avalanche photodiode, the wavelength λ2 of the self-emission generated in the light detection region 11 is, for example, from 700 nm to 1100 nm. The thickness of the reflective layer 133 is in the range of tens of nm to several mm.

[0065] Furthermore, at least one of wavelengths λ1 and λ2, the transmittance inside the resonant layer 132 is greater than the transmittance inside the light-absorbing layer 131. In other words, the extinction coefficient of the resonant layer 132 is less than the extinction coefficient of the light-absorbing layer 131. The light-absorbing layer 131 is, for example, made of metal. The metal constituting the light-absorbing layer 131 may include tungsten silicide (WSi) selected from... x Materials can be one or more from the group consisting of Ti, TiN, and Cr. In one example, the light-absorbing layer 131 mainly comprises tungsten silicide, and in one embodiment is composed of tungsten silicide.

[0066] The resonant layer 132 mainly comprises silicon compounds such as SiO2, SiN, and SiON, and in one embodiment is composed of SiO2, SiN, or SiON. The resonant layer 132 may be transparent at at least one of wavelengths λ1 and λ2. Furthermore, being transparent means being transparent relative to the target wavelength, i.e., having a transmittance of 70% or more.

[0067] Furthermore, at least one of wavelengths λ1 and λ2, the light reflectivity of the surface of the reflective layer 133 is greater than the light reflectivity of the surface of the resonant layer 132. Moreover, in this embodiment, the term "light reflectivity of the surface of the reflective layer" refers to the light reflectivity of the surface of the reflective layer on the resonant layer side, and the term "light reflectivity of the surface of the resonant layer" refers to the light reflectivity of the surface of the resonant layer on the light-absorbing layer side.

[0068] The reflective layer 133 is a metal layer. The metal constituting the reflective layer 133 may include one or more materials selected from the group consisting of Al, Al-based alloys (AlCu, AlSi, etc.), Cu, Ag, and Au. In one example, the reflective layer 133 mainly comprises Al, and in one embodiment it is composed of Al.

[0069] like Figure 1 As shown, the mounting substrate 35 has a flat main surface 35a. The mounting substrate 35 is rectangular in shape when viewed from above. The main surface 35a faces the back surface 16b of the semiconductor substrate 16. The mounting substrate 35 includes a plurality of electrodes 27 disposed on the main surface 35a. The electrodes 27 are disposed corresponding to the through electrodes 26. Specifically, the electrodes 27 are formed on each region of the main surface 35a opposite to the electrodes 24.

[0070] Electrodes 24 and 27 are connected by bump electrode 25. Thus, through electrode 26 is electrically connected to electrode 27 via electrode 24 and bump electrode 25. Furthermore, quenching resistor 21 is electrically connected to electrode 27 via electrode 23, through electrode 26, electrode 24, and bump electrode 25. Electrode 27 is made of the same metal as electrodes 22, 23, 24, and through electrode 26. Bump electrode 25, for example, primarily comprises solder.

[0071] The substrate 35 includes Figure 3 The signal processing unit 36 ​​is shown. Specifically, the mounting substrate 35 constitutes an ASIC (Application Specific Integrated Circuit). Each electrode 27 is electrically connected to the signal processing unit 36 ​​via wiring (not shown) formed within the mounting substrate 35. Output signals from each photodetector region 11 are input to the signal processing unit 36, and the signal processing unit 36 ​​processes these output signals.

[0072] The signal processing unit 36 ​​includes a CMOS circuit that converts the output signals from each photodetector region 11 into digital pulses. Furthermore, the mounting substrate 35 is configured such that each unit (photodetector region 11) includes circuitry for recording time information. The circuitry for recording time information uses a time-to-digital converter (TDC) or a time-to-amplitude converter (TAC). Therefore, differences in wiring spacing within the mounting substrate 35 do not affect the time resolution.

[0073] A passivation film 43 is disposed on the back surface 16b of the semiconductor substrate 16, and an opening 43a is formed in the passivation film 43 at a position corresponding to the bump electrode 25. A passivation film 44 is disposed on the main surface 35a of the mounting substrate 35, and an opening 44a is formed in the passivation film 44 at a position corresponding to the bump electrode 25.

[0074] The passivation films 43 and 44 are, for example, composed of polyimide-based, phenolic-based, epoxy-based resin insulating films, SiO2 / resin insulating films, SiN / resin insulating films, SiON / resin insulating films, SiO2 films, SiN films, or SiON films. As a method for forming the passivation films 43 and 44, spin coating can be used when the film is a resin insulating film, and CVD (Chemical Vapor Deposition) can be used when the film is a SiO2 film.

[0075] The glass substrate 31 has a front surface 31a and a back surface 31b that face each other. The glass substrate 31 is rectangular in shape when viewed from above. The back surface 31b faces the front surface 16a of the semiconductor substrate 16. Both the front surface 31a and the back surface 31b are flat. The glass substrate 31 is bonded to the photodetector 10 via an optical adhesive 32 and is optically connected. Alternatively, the glass substrate 31 can be directly formed on the photodetector 10.

[0076] A scintillator (not shown) can be optically attached to the main surface 31a of the glass substrate 31 via an additional optical adhesive. The scintillating light from the scintillator is transmitted through the glass substrate 31 as the detection light and incident on the photodetector element 10.

[0077] Next, refer to Figures 4-7 The manufacturing method of the aforementioned optical detection device 1A will be described. Figures 4-7 This is a diagram illustrating the manufacturing process of the light detection device 1A according to this embodiment.

[0078] First, such as Figure 4As shown in (a), a semiconductor substrate 16 having semiconductor regions 12 and 14 is fabricated. In this step, for example, a semiconductor substrate of a first conductivity type is prepared, and a plurality of semiconductor regions 14 of a second conductivity type are formed by ion implantation from the main surface side of the semiconductor substrate. At this time, the regions other than semiconductor regions 14 become semiconductor regions 12.

[0079] Next, as Figure 4 As shown in (b), a quenching resistor 21, electrodes 22 and 23, and an insulating film 41 are formed on the main surface 16a of the semiconductor substrate 16. In this step, firstly, a lower portion of the insulating film 41 is formed. Then, after forming an opening in the portion of the lower portion of the insulating film 41 located on the semiconductor region 14, the quenching resistor 21, electrodes 22 and 23 are formed on the lower portion of the insulating film 41. At this time, the electrode 22 is connected to the semiconductor region 14 through the opening. Then, an upper portion of the insulating film 41 is formed, through which the quenching resistor 21, electrodes 22 and 23 are covered.

[0080] Next, as Figure 4 As shown in (c), the optical adhesive 32 is sandwiched between the glass substrate 31 and the insulating film 41 to bond them together. Thus, the glass substrate 31 is optically connected to the photodetector element 10. Next, the back surface 16b of the semiconductor substrate 16 is polished to thin the semiconductor substrate 16. In this step, for example, mechanical polishing or chemical polishing is used to thin the semiconductor substrate 16.

[0081] Then, as Figure 5 As shown in (a), a light-absorbing film 13 is formed on the back side 16b of the semiconductor substrate 16. In one example, the light-absorbing layer 131 is formed by sputtering (e.g., WSi). x The resonant layer 132 (e.g., SiO2) is formed by CVD, and the reflective layer 133 (e.g., AlCu) is formed by sputtering.

[0082] Next, as Figure 5 As shown in (b), through-holes 15 are formed in the light-absorbing film 13 and the semiconductor substrate 16. In this step, for example, a dry etching method or a wet etching method is appropriately selected to form the through-holes 15, and etching is stopped when the electrode 23 is exposed. Alternatively, the light-absorbing film 13 may be formed after the through-holes 15 are formed.

[0083] Next, as Figure 5 As shown in (c), an insulating film 42 is formed on the back surface 16b of the semiconductor substrate 16 (on the light-absorbing film 13), the inner side surface of the through-hole 15, and the bottom surface (on the electrode 23). Then, as Figure 6As shown in (a), an opening 42a is formed in the portion of the insulating film 42 located on the bottom surface (on the electrode 23) of the through hole 15. In this step, the opening 42a is formed, for example, by etching the insulating film 42 until the electrode 23 is exposed.

[0084] Next, as Figure 6 As shown in (b), a metal film is formed on the inner side and bottom surface of the through hole 15, and in the area surrounding the through hole 15 in the back surface 16b. As a result, a through electrode 26 is formed on the inner side and bottom surface of the through hole 15, and an electrode 24 is formed on the back surface 16b.

[0085] Next, as Figure 7 As shown in (a), a passivation film 43 is formed on the back surface 16b of the semiconductor substrate 16 and within the through-hole 15, covering the electrode 24 and the through-hole 26. Then, as shown in (a), Figure 7 As shown in (b), an opening 43a is formed in the portion of the passivation film 43 located on the electrode 24 by etching. Subsequently, a bump electrode 25 covering the opening 43a is formed.

[0086] Furthermore, prior to the formation of the bump electrode 25, an under-bump metal (UBM) is formed in the area exposed by the self-passivation film 43 of the electrode 24. The UBM contains a material that provides excellent electrical and physical bonding with the bump electrode 25. Electroless plating can be used as a method for forming the UBM. The bump electrode 25 can be formed using a solder ball mounting method or a printing method.

[0087] Next, the photodetector 10 is connected to the separately prepared mounting substrate 35 by bumps (see reference). Figure 1 Then, the laminate containing the glass substrate 31, the light detection element 10, and the mounting substrate 35 is cut to form a single piece. Through the above steps, the light detection device 1A of this embodiment is manufactured. Alternatively, after cutting the laminate containing the glass substrate 31 and the light detection element 10 to form a single piece, the light detection element 10 and the mounting substrate 35 of the laminate can be connected by protrusions.

[0088] The effects obtained by the photodetector 10 of this embodiment, as described above, will be explained. In the photodetector 10 of this embodiment, an amount of charge corresponding to the light intensity of the detected light incident from the main surface 16a of the semiconductor substrate 16 is generated in the photodetector region 11. Thus, the incident light amount of the detected light can be detected electrically. The detected light that is not absorbed in the photodetector region 11 reaches the light absorption film 13 provided on the back surface 16b of the semiconductor substrate 16. In the case where self-emission occurs in the photodetector region 11, this self-emission also reaches the light absorption film 13.

[0089] The light-absorbing film 13 has a multilayer structure comprising a light-absorbing layer 131, a resonant layer 132, and a reflective layer 133. A portion of the light incident on the light-absorbing film 13 is immediately absorbed in the light-absorbing layer 131. Light not absorbed by the light-absorbing layer 131 passes through the light-absorbing layer 131 and enters the resonant layer 132. Then, the light entering the resonant layer 132 undergoes multiple reflections within the light-absorbing layer 131 at the interface between the light-absorbing layer 131 and the resonant layer 132, and at the interface between the resonant layer 132 and the reflective layer 133.

[0090] Therefore, according to this light absorption film 13, extremely high absorption efficiency can be achieved compared to a single-layer light absorption film. Thus, the light detection element 10 according to this embodiment can effectively reduce light reflection at the back surface 16b of the semiconductor substrate 16, thereby suppressing the reduction in temporal resolution and reducing crosstalk between adjacent units.

[0091] As mentioned above, the optical thickness of the resonant layer 132 can be within ±20% of an integer multiple of the wavelength λ1 of the detected light or the wavelength λ2 of the self-emission generated in the light detection region 11 (i.e., λ1 / 4 or λ2 / 4).

[0092] In this case, the phase of the light reflected at the interface between the light-absorbing layer 131 and the resonant layer 132 is offset from the phase of the light reflected at the interface between the resonant layer 132 and the reflective layer 133 by approximately π (rad), thus canceling each other out. Therefore, the absorption efficiency (extinction efficiency) of the light-absorbing film 13 can be further improved.

[0093] As described above, the light detection region 11 can be an avalanche photodiode or a pn junction photodiode. For example, in this case, an amount of charge corresponding to the intensity of the detected light can be generated in the light detection region 11.

[0094] Furthermore, especially when the light detection region 11 is an avalanche photodiode, self-emission (secondary photons) is generated in the light detection region 11. The light detection element 10 of this embodiment can also reduce crosstalk caused by self-emission generated in the light detection region 11 by appropriately designing the light absorption film 13. Therefore, the light detection element 10 of this embodiment is particularly effective when the light detection region 11 is an avalanche photodiode.

[0095] As in this embodiment, the photodetector 10 may include a through electrode 26 that connects the main surface 16a and the back surface 16b, with one end on the main surface 16a side electrically connected to the photodetector region 11. In this case, the mounting substrate 35 can be disposed on the back surface 16b, which is opposite to the main surface 16a on which the detected light is incident. Even if the majority of photodetector regions 11 are arranged in a two-dimensional pattern on the main surface 16a, the charge (output current) from each photodetector region 11 can still be easily extracted.

[0096] Furthermore, since there is no need to provide wiring such as bonding lines for electrical connection with the mounting substrate 35 on the main surface 16a, the fill factor of the photodetector 10 can be increased. In other words, the size of the photodetector 10 can be miniaturized and it can be housed in a small package.

[0097] In addition, to improve the ease of forming the through electrode 26, the semiconductor substrate 16 can be thinned (see reference). Figure 5 (a) However, if this is done, the distance between the light incident surface (main surface 16a) and the back surface 16b of the semiconductor substrate 16 becomes shorter, which easily leads to a decrease in time resolution and crosstalk between adjacent cells. The photodetector 10 according to this embodiment can suppress the decrease in time resolution and reduce crosstalk between adjacent cells, which is particularly effective when the through electrode 26 is provided on the semiconductor substrate 16.

[0098] As in this embodiment, the photodetector 10 can be bonded to the glass substrate 31. In this case, the mechanical strength of the semiconductor substrate 16 can be further reduced, thus allowing for further thinning of the semiconductor substrate 16. Consequently, the formation of the through-hole 15 becomes easier, and the response characteristics of the photodetector 10 are improved.

[0099] The following is an example illustrating the effectiveness of this embodiment in reducing crosstalk. Figure 8 and Figure 9 The diagram illustrates the cross-sectional structure of the laminates 100A and 100B, which were fabricated for verification purposes.

[0100] like Figure 8As shown, the laminate 100A has a structure formed by sequentially stacking bonding resin 102, an alloy layer 103 of Al and Cu, a SiO2 layer 104 formed by CVD, a WSi layer 105, a Si layer 106, and a SiO2 layer 107 on a supporting glass 101. The WSi layer 105, SiO2 layer 104, and alloy layer 103 correspond to the light-absorbing layer 131, the resonant layer 132, and the reflective layer 133 of this embodiment, respectively. The Si layer 106 corresponds to the semiconductor substrate 16 of this embodiment. Figure 9 As shown, the laminate 100B has a structure formed by sequentially stacking bonding resin 102, Al and Cu alloy layer 103, resin insulating layer 108 (phenolic resin), Si layer 106, and SiO2 layer 107 on the support glass 101.

[0101] In these laminates 100A and 100B, the thickness of the supporting glass 101 is set to 300 μm, the thickness of the bonding resin 102 is set to 10 μm, the thickness of the alloy layer 103 is set to 1000 nm, the thickness of the SiO2 layer 104 is set to 100 nm, the thickness of the WSi layer 105 is set to 23 nm, and the thickness of the resin insulating layer 108 is set to 5000 nm. Then, the thickness of the Si layer 106 is varied in the range of 20 μm to 70 μm, and multiple samples are made for each of the laminates 100A and 100B.

[0102] In addition, in the Si layer 106 of each stack, semiconductor regions 110 arranged in a two-dimensional pattern of 26 rows and 26 columns are formed as multiple units (photodetection regions) and wiring (not shown). Semiconductor regions 110 are equivalent to semiconductor regions 14 in this embodiment. The size of each unit is set to 50 μm on each side. Then, quenching resistors are formed in each unit, and the configuration is set to concentrate the output of charge. The output charge is converted into a voltage signal by a broadband amplifier, pulses with a height above a threshold are extracted by a comparator, and the number of pulses is counted by a counter circuit.

[0103] Figure 10 To schematically illustrate the voltage signal waveform including crosstalk, when one photon is detected in each of the above samples, a pulse signal G12 with a height of one photon fraction is output. Here, the pulse height of one photon fraction is defined as one photon equivalent (pe). If crosstalk occurs between adjacent units, in addition to the pulse signal G12 with a height of one photon fraction, a pulse signal G11 with a height of two photon fractions (or more) will also appear in the voltage signal waveform.

[0104] If the threshold of the comparator relative to the voltage signal is set to, for example, 0.5pe (line D1 in the figure), then these pulse signals G11 and G12 do not need to be distinguished from each other, and are counted as one pulse each. Alternatively, if the threshold of the comparator relative to the voltage signal is set to, for example, 1.5pe (line D2 in the figure), then pulse signal G12 is not detected, and only pulse signal G11 is counted.

[0105] Figure 11 To illustrate an example where the sample is placed in a dark chamber, and the count rate of autoluminescence (hereinafter referred to as dark count rate) is measured by varying the threshold of the comparator. Figure 11 In the diagram, the vertical axis represents the dark count rate (unit: cps (counts per second)) and the horizontal axis represents the threshold (unit: V).

[0106] Within range A1, where the threshold is below 1.0 (pe), pulse signals of all pulse heights are counted, resulting in a higher dark count rate. Furthermore, within range A2, where the threshold is above 1.0 (pe) but below 2.0 (pe), the dark count rate decreases by one stage from range A1 because pulse signals of height 1.0 (pe) are not counted. Thus, the dark count rate decreases in stages corresponding to the increase in the threshold.

[0107] Set the dark count rate of range A1 to N 0.5p.e. Set the dark count rate of range A2 to N. 1.5p.e. When, the crosstalk probability, representing the degree of crosstalk, is expressed through N. 0.5p.e. With N 1.5p.e. The ratio (N) 1.5p.e. / N 0.5p.e. The higher the crosstalk probability, the greater the degree of crosstalk.

[0108] Figure 12 Curves illustrating the relationship between reverse bias and crosstalk probability for each sample in the embodiments. Figure 12 In the figure, the vertical axis represents the crosstalk probability (unit: %), and the horizontal axis represents the overvoltage relative to the operating voltage (unit: V). Curves G21 to G23 in the figure represent the case of the above-mentioned stack 100B (i.e., without the light absorption film), and curves G24 to G26 in the figure represent the case of the above-mentioned stack 100A (i.e., with the light absorption film). In addition, curves G21 and G24 represent the case where the thickness of Si layer 106 is set to 20 μm, curves G22 and G25 represent the case where the thickness of Si layer 106 is set to 45 μm, and curves G23 and G26 represent the case where the thickness of Si layer 106 is set to 70 μm.

[0109] Reference Figure 12It is known that the thinner the Si layer 106, the greater the probability of crosstalk. This means that the thinner the semiconductor substrate 16, the easier it is to generate crosstalk. Additionally, referring to... Figure 12 It is evident that the crosstalk probability is exceptionally low in laminate 100A (with a light-absorbing film) compared to laminate 100B (without a light-absorbing film). This means that in this embodiment, the crosstalk is significantly reduced by the light-absorbing film 13 provided in the light-detecting element 10. Furthermore, although this result is related to self-emission, it is assumed that the same applies to the detected light.

[0110] Figure 13 Curves illustrating the dark current characteristics of each sample in the embodiments due to self-emission are shown. Figure 13 In the figure, the vertical axis represents the magnitude of the dark current (unit: A), and the horizontal axis represents the reverse bias voltage (unit: V). Curves G31 to G33 in the figure represent the case of the above-mentioned stack 100B (without the light absorption film), and curves G34 to G36 in the figure represent the case of the above-mentioned stack 100A (with the light absorption film). In addition, curves G31 and G34 represent the case where the thickness of the Si layer 106 is set to 20 μm, curves G32 and G35 represent the case where the thickness of the Si layer 106 is set to 45 μm, and curves G33 and G36 represent the case where the thickness of the Si layer 106 is set to 70 μm.

[0111] If reference Figure 13 It can be seen that the thinner the Si layer 106, the narrower the range of usable reverse bias voltage (the lower the reverse bias voltage when the dark current increases sharply). This means that the thinner the semiconductor substrate 16, the narrower the range of usable reverse bias voltage. Furthermore, if we refer to... Figure 13 It can be seen that, in laminate 100A (with light absorption film), compared with laminate 100B (without light absorption film), the range of usable reverse bias voltage is larger (the reverse bias voltage is larger when the dark current increases sharply).

[0112] For example, when comparing curves G31 and G34, even though the thickness of the Si layer 106 is the same, the dark current increases near 57.5V in curve G31, while it increases near 61V in curve G34. Therefore, the usable reverse bias voltage range is approximately +3.5V wider in curve G34 compared to curve G31. This means that in this embodiment, by providing the light absorption film 13 to the photodetector element 10, the self-emitted light can be effectively absorbed, thereby expanding the usable reverse bias voltage range.

[0113] The function of the light absorption film 13 in this embodiment will be explained in detail. Figure 14 A diagram illustrating the cross-sectional structure of the light-absorbing film 13.

[0114] As described above, the light-absorbing film 13 has a multilayer structure comprising a light-absorbing layer 131, a resonant layer 132, and a reflective layer 133. A portion of the light L reaching the light-absorbing film 13 is reflected at the surface of the light-absorbing layer 131, while the remainder enters the interior of the light-absorbing layer 131. At this time, if the sheet resistance of the light-absorbing layer 131 is made to match the spatial impedance of the adjacent semiconductor substrate 16, the surface reflectivity is zero, and all the light L enters the interior of the light-absorbing layer 131.

[0115] Light L entering the interior of the light-absorbing layer 131 is gradually absorbed at a rate calculated based on the extinction coefficient of the light-absorbing layer 131. Therefore, if the light-absorbing layer 131 is sufficiently thick, almost all of the light L will be absorbed by the light-absorbing layer 131. However, increasing the thickness of the light-absorbing layer 131 leads to a decrease in sheet resistance and an increase in the surface reflectivity of the light-absorbing layer 131. Therefore, in this embodiment, the thickness of the light-absorbing layer 131 is limited, while allowing a portion of the light L to pass through the light-absorbing layer 131.

[0116] A portion of the light L that passes through is reflected at the interface between the resonant layer 132 and the light-absorbing layer 131, returning to the light-absorbing layer 131. Hereinafter, this reflected light will be referred to as the first reflected light. In the case where the light-absorbing layer 131 contains metal and the resonant layer 132 contains dielectric, the impedance of the resonant layer 132 is greater than the impedance of the light-absorbing layer 131 (in other words, the refractive index of the resonant layer 132 is less than the refractive index of the light-absorbing layer 131), therefore the first reflected light does not have a phase shift of π (rad).

[0117] Additionally, the remainder of light L enters the interior of the resonant layer 132 through this interface. Light L entering the interior of the resonant layer 132 reaches the interface between the resonant layer 132 and the reflective layer 133 with almost no attenuation, and undergoes total internal reflection at this interface. Hereinafter, this reflected light will be referred to as the second reflected light. The second reflected light re-enters the interior of the resonant layer 132 and proceeds to the light-absorbing layer 131. Since the impedance of the reflective layer 133 is close to 0Ω (in other words, its refractive index is close to infinity), the second reflected light exhibits a phase shift of π (rad).

[0118] When the second reflected light reaches the light-absorbing layer 131, if the phase difference between the second and first reflected light is π (rad), they cancel each other out. Therefore, the optical thickness of the resonant layer 132 (in other words, the optical spacing between the light-absorbing layer 131 and the reflective layer 133) only needs to be 1 / 4 of the wavelength of light L. However, since the electric field amplitudes of the first and second reflected light are not exactly the same, they do not completely cancel each other out, and a portion of the reflected light is incident on the light-absorbing layer 131. The reflected light incident on the light-absorbing layer 131 is absorbed in the light-absorbing layer 131. In addition, a portion of the second reflected light remains inside the resonant layer 132, undergoing multiple reflections, but is gradually absorbed by the light-absorbing layer 131. In this way, almost all of the light L is absorbed by the light-absorbing layer 131.

[0119] A design example of the light-absorbing film 13 will be explained. Figure 15 The diagram schematically illustrates the configuration in which the light-absorbing film 13 is disposed on the back side 16b of the semiconductor substrate 16.

[0120] In this embodiment, such as Figure 15 As shown, the light-absorbing layer 131 of the light-absorbing film 13 is connected to the semiconductor substrate 16. Here, the semiconductor substrate 16 is made of Si or InP. The wavelength of light L is set to 1.55 μm. The light-absorbing layer 131 is made of WSi, the resonant layer 132 is made of SiO2, and the reflective layer 133 is made of Al.

[0121] The characteristic impedance of air is 377Ω, and the refractive index of Si and InP is approximately 3.5. Therefore, the characteristic impedance of semiconductor substrate 16 is 377Ω / 3.5 = 108Ω. Additionally, the resistivity of tungsten silicide (WSi2) is 2.48 × 10⁻⁶. -4 Ω·cm. Therefore, the preferred thickness t of the light-absorbing layer 131 is...

[0122] [Number 1]

[0123]

[0124] Figure it out.

[0125] Furthermore, the specific refractive index of SiO2 is 1.48, therefore the preferred thickness of the resonant layer 132 is calculated as 1.55 μm / 1.48 / 4 = 262 nm. Additionally, the specific resistivity of Al is 2.65 × 10⁻⁶. -6 Ω·cm; additionally, the resistivity of Al is 2.65 × 10⁻⁶ Ω·cm. -6 Ω·cm, therefore, by setting the reflective layer 133 to a sufficient thickness, for example, 1 μm, the sheet resistance becomes 0.0265 Ω. The impedance of SiO2 is

[0126] [Number 2]

[0127]

[0128] Therefore, the reflection coefficient at the interface between the resonant layer 132 and the reflective layer 133 is 0.998.

[0129] Following the above approach, the design of the light absorption film 13 corresponding to the wavelength λ1 of the detected light or the wavelength λ2 of the self-emission becomes easier. Table 1 below shows design examples of the light absorption film 13 when the wavelength λ1 of the detected light is 600 nm, 800 nm, and 1000 nm. In addition, Table 2 below shows design examples of the light absorption film 13 when the wavelength λ2 of the self-emission is in the range of 700 nm to 1100 nm.

[0130] [Table 1]

[0131]

[0132] [Table 2]

[0133]

[0134]

[0135] Furthermore, in the above design example, it is assumed that light L is incident from a direction perpendicular to the surface of the light-absorbing film 13 (in other words, the thickness direction of the light-absorbing film 13). However, if light L is incident from a direction oblique to the surface of the light-absorbing film 13, the incident angle of light L can be incorporated into the above design. That is, it is sufficient to calculate the propagation angle of light within each layer 131 to 133 based on the refractive index of each layer 131 to 133, and set the thickness of each layer 131 to 133 to take into account this propagation angle.

[0136] (Example of variation)

[0137] Figure 16 This is a partial cross-sectional view showing the structure of the light detection element 10A in the first variation of the above embodiment. This light detection element 10A differs from the light detection element 10 described above in that it lacks the glass substrate 31 and optical adhesive 32, but is identical to the light detection element 10 in other aspects. In this structure, the same effects as in the above embodiment can be achieved.

[0138] Furthermore, in the case where the glass substrate 31 is not provided as in this variation, light loss (absorption and reflection) caused by the glass substrate 31 and the optical adhesive 32 can be avoided, thereby improving the light detection efficiency. In addition, the generation of exhaust gas from the optical adhesive 32 can be avoided. Furthermore, additional optical components such as scintillators or microlenses can be directly mounted on the light incident surface of the light detection element.

[0139] Figure 17 This is a partial cross-sectional view showing the structure of the light detection element 10B in the second variation of the above embodiment. The light detection element 10B differs from the light detection element 10 in that the light absorption film 13 is formed not only on the back surface 16b but also on the inner side surface and bottom surface of the through-hole 15; otherwise, it is the same as the light detection element 10. In this case, the insulating film 42 and the through electrode 26 are disposed within the through-hole 15 via the light absorption film 13.

[0140] With such a structure, light reflection at the inner surface of the through-hole 15 can be suppressed in addition to the back surface 16b, thus further suppressing the reduction in time resolution and further reducing crosstalk between adjacent units. When fabricating the photodetector 10B of this variation, the light-absorbing film 13 can be formed after the through-hole 15 is formed. Furthermore, as in the above embodiment, when the light-absorbing film 13 is formed only on the back surface 16b and not on the inner surface or bottom surface of the through-hole 15, it has advantages such as simplified manufacturing steps, reduced labor time, and lower costs.

[0141] Figure 18 This is a partial cross-sectional view showing the structure of the light detection element 10C in the third variation of the above-described embodiment. This light detection element 10C differs from the light detection element 10B in that it lacks the glass substrate 31 and optical adhesive 32, but is identical to the light detection element 10B in other aspects. With this structure, it can achieve the same effects as the first and second variations.

[0142] Figure 19 This is a partial cross-sectional view showing the structure of the light detection element 10D in the fourth variation of the above embodiment. The light detection element 10D differs from the light detection element 10 at the point where the inner surface of the through-hole 15 is inclined relative to the thickness direction of the semiconductor substrate 16 (i.e., the direction perpendicular to the main surface 16a and the back surface 16b), but is identical to the light detection element 10 at other points. In this case, the inner diameter of the through-hole 15 increases from the main surface 16a towards the back surface 16b. In this structure, the same effects as in the above embodiment can be achieved.

[0143] Figure 20 This is a partial cross-sectional view showing the structure of the light detection element 10E in the fifth variation of the above-described embodiment. This light detection element 10E differs from the light detection element 10D described above in that it lacks the glass substrate 31 and optical adhesive 32, but is identical to the light detection element 10D in other aspects. In this structure, the same effects as in the above-described embodiment can be achieved. Furthermore, by omitting the glass substrate 31, the same effects as in the first variation can be achieved.

[0144] Figure 21This is a partial cross-sectional view showing the structure of the light detection element 10F in the sixth variation of the above embodiment. The light detection element 10F differs from the light detection element 10D in that the light absorption film 13 is formed not only on the back surface 16b but also on the inner side and bottom surface of the through-hole 15. In other points, it is identical to the light detection element 10D. In this case, it can achieve the same effect as the second variation.

[0145] Figure 22 This is a partial cross-sectional view showing the structure of the light detection element 10G in the seventh variation of the above-described embodiment. This light detection element 10G differs from the light detection element 10F in that it lacks the glass substrate 31 and optical adhesive 32, but is identical to the light detection element 10F in other aspects. With this structure, it can achieve the same effects as in the fifth and sixth variations.

[0146] Figure 23 This is a partial cross-sectional view showing the structure of the photodetector 10H in the eighth variation of the above embodiment. The photodetector 10H has a bonding line 28 replacing the bump electrode 25 and through electrode 26 in the above embodiment, and has a glass substrate 33 and optical adhesive 34 replacing the glass substrate 31 and optical adhesive 32 in the above embodiment.

[0147] Specifically, no through-hole 15 is formed in the semiconductor substrate 16, and the electrode 23 is exposed through an opening 41a formed on the upper surface of the insulating film 41. Bonding wires 28 are provided in each of the plurality of units. Furthermore, one end of the bonding wire 28 is connected to a portion of the electrode 23 exposed at the opening 41a. Moreover, the other end of the bonding wire 28 is connected to a circuit board (not shown) having the same circuitry as the mounting substrate 35 in the above embodiment.

[0148] The light-absorbing film 13 is formed over the entire back surface 16b of the semiconductor substrate 16. On the side of the light-absorbing film 13 opposite to the semiconductor substrate 16 (i.e., the surface of the reflective layer 133), the glass substrate 33 is bonded to it via an optical adhesive 34. This structure achieves the same effects as the embodiments described above. Furthermore, since it is not necessary to form a through electrode 26, the manufacturing process is simplified, reducing labor time and lowering costs.

[0149] Figure 24 This is a partial cross-sectional view showing the structure of the light detection element 10J in the ninth variation of the above-described embodiment. This light detection element 10J differs from the light detection element 10H in that it lacks the glass substrate 33 and optical adhesive 34, but is identical to the light detection element 10H in other aspects. In this structure, the same effects as in the eighth variation can be achieved. Furthermore, by omitting the glass substrate 33, the same effects as in the first variation can be achieved.

[0150] The semiconductor photodetector is not limited to the above-described embodiments and configurations, but can be varied in various ways.

[0151] A quenching resistor 21 is electrically connected to a through electrode 26, but this is not a limitation. Multiple quenching resistors (e.g., four quenching resistors) 21 can be electrically connected to a through electrode 26. In this case, the commonality of the through electrodes 26 between units is sought, thereby reducing the number of through electrodes 26 formed on the semiconductor substrate 16. As a result, the reduction in the mechanical strength of the semiconductor substrate 16 can be suppressed. The number of quenching resistors electrically connected to a through electrode 26 is not limited to "4", and can be "3" or less, or "5" or more.

[0152] In the case where multiple quenching resistors 21 are electrically connected to a through electrode 26, it is preferable that the wiring distance from each photodetector region 11 through the corresponding quenching resistor 21 to the through electrode 26 is equal. In this case, in the configuration that seeks commonality of the through electrode 26 between units, a reduction in time resolution can also be prevented.

[0153] The shape of the semiconductor region 14 is not limited to the shape described above, and may also be other shapes (e.g., circular). In addition, the number (number of rows and columns) or arrangement of the photodetector regions 11 is not limited to those described above.

[0154] The light detection element 10 has multiple light detection areas 11, but is not limited to this. The light detection element may also have a single light detection area 11. In this case, it can also suppress the reduction of temporal resolution.

[0155] The light detection device 1A has a configuration that outputs the output current from multiple light detection areas 11 in a concentrated (batch) manner, but is not limited thereto. The light detection element can also be applied to a light detection device that outputs the output current from multiple light detection areas 11 (pixels) individually for each light detection area 11. Such a light detection device can be used, for example, as an imaging device such as a CCD. In this case, the "unit" in the above embodiment is replaced with a "pixel", and the light detection element can reduce crosstalk between adjacent pixels.

[0156] The semiconductor photodetector element of the above embodiment is configured to include: a semiconductor substrate having a main surface on which the detected light is incident and a back surface opposite to the main surface, and having one or more photodetector regions on the main surface side that generate an amount of charge corresponding to the light intensity of the detected light; and a light absorption film disposed on the back surface of the semiconductor substrate; wherein the light absorption film has a multilayer structure including a metal layer, i.e., a reflective layer, a resonant layer disposed between the reflective layer and the semiconductor substrate, and a light absorption layer disposed between the resonant layer and the semiconductor substrate, wherein at least one of the wavelength of the detected light and the wavelength of self-emission generated in the photodetector region is present, the transmittance inside the resonant layer is greater than the transmittance inside the light absorption layer, and the light reflectance of the surface of the reflective layer is greater than the light reflectance of the surface of the resonant layer.

[0157] In the aforementioned semiconductor photodetector, the following configuration can be adopted: the optical thickness of the resonant layer is within ±20% of an integer multiple of either one-quarter of the wavelength of the detected light or one-quarter of the wavelength of the self-emitted light.

[0158] In this case, the phase of the light reflected at the interface between the light-absorbing layer and the resonant layer is offset by approximately π (rad) from the phase of the light reflected at the interface between the resonant layer and the reflective layer, thus canceling each other out. Therefore, the absorption efficiency (extinction efficiency) of the light-absorbing film can be further improved.

[0159] In the aforementioned semiconductor photodetector element, one or more photodetector regions can be configured as avalanche photodiodes or pn junction photodiodes. For example, in this case, an amount of charge corresponding to the intensity of the detected light can be generated in the photodetector region.

[0160] Furthermore, especially in the case where the light detection region is an avalanche photodiode, self-emission is generated in the light detection region. In the aforementioned semiconductor photodetector, crosstalk caused by self-emission generated in the light detection region can also be reduced. Therefore, the aforementioned semiconductor photodetector is particularly effective when the light detection region is an avalanche photodiode.

[0161] The aforementioned semiconductor photodetector can be configured such that it has a through electrode that connects the main surface and the back surface, with one end on the main surface electrically connected to the photodetector region. In this case, a wiring board or similar material can be disposed on the back surface opposite to the main surface where the light is incident, and even if a plurality of photodetector regions are arranged on the main surface, the charge (output current) from each photodetector region can be easily extracted.

[0162] Furthermore, to improve the ease of forming the through electrode, the semiconductor substrate can be thinned. However, if this is done, the distance between the light incident surface (main surface) and the back surface of the semiconductor substrate becomes shorter, which easily leads to a decrease in temporal resolution and crosstalk between adjacent pixels (adjacent units). According to the semiconductor photodetector described above, the decrease in temporal resolution can be suppressed, and crosstalk between adjacent pixels (adjacent units) can be reduced, making it particularly effective when the through electrode is disposed on the semiconductor substrate.

[0163] In the aforementioned semiconductor photodetector, the following configuration can be adopted: the light absorption layer mainly comprises tungsten silicide, and the resonant layer mainly comprises SiO2. In this case, a light absorption film with high absorption efficiency can be achieved.

[0164] [Industry availability]

[0165] This invention can be used as a semiconductor photodetector element that can reduce light reflection from the back side of a semiconductor substrate.

[0166] Symbol Explanation

[0167] 1A: Optical Detection Device

[0168] 10, 10A~10H, 10J: Optical detection element

[0169] 11: Light detection area

[0170] 12: Semiconductor Region

[0171] 13: Light Absorption Film

[0172] 14: Semiconductor Region

[0173] 15: Through hole

[0174] 16: Semiconductor substrate

[0175] 16a: Main face

[0176] 16b: Back

[0177] 21: Quenching resistance

[0178] 22, 23, 24, 27: Electrodes

[0179] 25: Bump electrode

[0180] 26: Through electrode

[0181] 28: Joint line

[0182] 31: Glass substrate

[0183] 31a: Main face

[0184] 31b: Back

[0185] 32: Optical adhesive

[0186] 33: Glass substrate

[0187] 34: Optical adhesives

[0188] 35: Mounting substrate

[0189] 35a: Main face

[0190] 36: Signal Processing Department

[0191] 41, 42: Insulating film

[0192] 41a, 42a: Opening

[0193] 43,44: Passivation film

[0194] 43a, 44a: Opening

[0195] 100A, 100B: Laminated structures

[0196] 101: Supporting glass

[0197] 102: Bonding resin

[0198] 103: Alloy layer

[0199] 104: SiO2 layer

[0200] 105: WSi layer

[0201] 106: Si layer

[0202] 108: Resin insulation layer

[0203] 110: Semiconductor Region

[0204] 131: Light Absorption Layer

[0205] 132: Resonant Layer

[0206] 133: Reflective layer

[0207] L: Light

[0208] V1: Negative potential

[0209] V2: Positive potential.

Claims

1. A semiconductor photodetector element, comprising: A semiconductor substrate having a main surface as the incident surface of the light to be detected, and a back surface opposite to the main surface, and having one or more light detection regions on the main surface side that generate a charge corresponding to the light intensity of the light to be detected; and A light-absorbing film is disposed on the back side of the semiconductor substrate and absorbs at least one of the detected light incident from the main surface that is not absorbed by the light detection area and is transmitted through it, and the self-emission generated in the light detection area. Each of the one or more photodetector regions has a semiconductor region of a second conductivity type formed on the main surface side of the semiconductor substrate, wherein the area of ​​the semiconductor substrate other than the semiconductor region of the second conductivity type is occupied by a semiconductor region of a first conductivity type. The semiconductor region of the second conductivity type is electrically connected to the electrode disposed on the main surface side of the semiconductor substrate. The light-absorbing film has a multilayer structure comprising a reflective layer as a metal layer, a resonant layer disposed between the reflective layer and the semiconductor substrate, and a light-absorbing layer disposed between the resonant layer and the semiconductor substrate. In at least one of the wavelength of the detected light and the wavelength of the self-emitted light generated in the light detection region, the transmittance inside the resonant layer is greater than the transmittance inside the light absorption layer, and the light reflectance of the surface of the reflective layer is greater than the light reflectance of the surface of the resonant layer.

2. The semiconductor photodetector element as described in claim 1, wherein, The optical thickness of the resonant layer is within ±20% of an integer multiple of either one-quarter of the wavelength of the detected light or one-quarter of the wavelength of the self-emitted light.

3. The semiconductor photodetector element as described in claim 1, wherein, The one or more light detection regions are avalanche photodiodes.

4. The semiconductor photodetector element as described in claim 2, wherein, The one or more light detection regions are avalanche photodiodes.

5. The semiconductor photodetector element according to any one of claims 1 to 4, wherein, It further includes a through electrode that extends between the main surface and the back surface, with one end on the main surface side electrically connected to the light detection area.

6. The semiconductor photodetector element according to any one of claims 1 to 4, wherein, The light-absorbing layer mainly contains tungsten silicide, and the resonant layer mainly contains SiO2.

7. The semiconductor photodetector element as described in claim 5, wherein, The light-absorbing layer mainly contains tungsten silicide, and the resonant layer mainly contains SiO2.

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