Photodetector

Abstract

To provide a photodetector capable of suppressing noise.SOLUTION: A photodetector according to an embodiment includes: a plurality of cell regions disposed in an array; and an element isolation region provided between the cell regions. Each of the cell regions includes: a semiconductor layer having a first face and a second face opposite to the first face; a first semiconductor region of a first conductivity type provided in the semiconductor layer; a second semiconductor region of a second conductivity type provided between the first semiconductor region and the first face; an electrode in contact with the second semiconductor region; and a plurality of metal regions having a part surrounded by the first semiconductor region and another part surrounded by the second semiconductor region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a light detection device. [Background technology]

[0002] As a photodetector for detecting weak light, a silicon photomultiplier (SiPM) has been developed, in which multiple cell regions are arranged in an array and each cell region is equipped with an avalanche photodiode (APD).SiPMs have high detection sensitivity, capable of detecting a single incident photon.

[0003] However, because SiPMs have high detection sensitivity, suppressing noise generation is a challenge. The types of noise that need to be suppressed include crosstalk noise and delay noise.

[0004] Crosstalk noise occurs when secondary photons generated by an electron avalanche are incident on an adjacent cell region, while delayed noise occurs when carriers generated in a cell region cause an electron avalanche after a certain time has elapsed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-61064 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a photodetector capable of suppressing noise. [Means for solving the problem]

[0007] A photodetector according to one aspect of the present invention is a photodetector including a plurality of cell regions arranged in an array and an isolation region provided between the cell regions, wherein the cell region includes a semiconductor layer having a first surface and a second surface opposite to the first surface, a first semiconductor region of a first conductivity type provided in the semiconductor layer, a second semiconductor region of a second conductivity type provided between the first semiconductor region and the first surface, an electrode in contact with the second semiconductor region, and a plurality of metal regions each partially surrounded by the first semiconductor region and partially surrounded by the second semiconductor region. the plurality of metal regions are surrounded by the element isolation region, and the plurality of metal regions are arranged at predetermined intervals on the first surface. . [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic top view of a photodetector according to a first embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view of a photodetector according to a first embodiment. [Figure 3] FIG. 2 is an enlarged schematic cross-sectional view of the photodetector according to the first embodiment. [Figure 4] FIG. 2 is an enlarged schematic top view of the photodetector according to the first embodiment. [Figure 5] FIG. 2 is an enlarged schematic cross-sectional view of the photodetector according to the first embodiment. [Figure 6] FIG. 10 is a schematic cross-sectional view of a photodetector according to a comparative example. [Figure 7] FIG. 10 is an equivalent circuit diagram of a photodetector according to a comparative example. [Figure 8] FIG. 3 is an explanatory diagram illustrating the operation and effect of the photodetector according to the first embodiment. [Figure 9] FIG. 4 is an enlarged schematic cross-sectional view of a photodetector according to a modified example of the first embodiment. [Figure 10] FIG. 4 is an enlarged schematic top view of a photodetector according to a modified example of the first embodiment. [Figure 11] FIG. 10 is an enlarged schematic cross-sectional view of a photodetector according to a second embodiment. [Figure 12] FIG. 4 is an enlarged schematic top view of a photodetector according to a second embodiment. [Figure 13] FIG. 10 is an enlarged schematic cross-sectional view of a photodetector according to a third embodiment. [Figure 14] FIG. 10 is an enlarged schematic top view of a photodetector according to a third embodiment. [Figure 15] FIG. 10 is an enlarged schematic cross-sectional view of a photodetector according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the same or similar components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0010] In this specification, the upward direction of the drawing may be referred to as "up" and the downward direction of the drawing may be referred to as "down" in order to indicate the positional relationship of parts, etc. In this specification, the concepts of "up" and "down" do not necessarily refer to the direction of gravity.

[0011] In this specification, n + shape, n shape, n - When there is a notation with form, n + shape, n shape, n - This means that the concentration of n-type impurities decreases in the order of n-type. + shape, p shape, p - If there is a form notation, p + shape, p shape, p - This means that the p-type impurity concentration decreases in the order of the type.

[0012] In this specification, the distribution and absolute value of the impurity concentration of a semiconductor region can be measured using, for example, secondary ion mass spectrometry (SIMS), and the relative magnitude relationship between the impurity concentrations of two semiconductor regions can be determined using, for example, scanning capacitance microscopy (SCM).

[0013] Qualitative and quantitative analysis of the chemical composition of the components constituting the photodetector herein can be performed, for example, by SIMS or energy dispersive X-ray spectroscopy (EDX). Furthermore, for measuring the thickness of the components constituting the photodetector and the distance between the components, for example, a transmission electron microscope (TEM) can be used. Furthermore, for identifying the materials constituting the photodetector, for example, X-ray diffraction analysis (XRD), electron beam diffraction analysis (EBD), and X-ray photoelectron spectroscopy (XPS) can be used.

[0014] (First embodiment) The photodetector of the first embodiment is a photodetector having a plurality of cell regions arranged in an array and an element isolation region provided between the cell regions, and the cell region includes a semiconductor layer having a first surface and a second surface opposite to the first surface, a first semiconductor region of a first conductivity type provided in the semiconductor layer, a second semiconductor region of a second conductivity type provided between the first semiconductor region and the first surface, an electrode in contact with the second semiconductor region, and a plurality of metal regions, partly surrounded by the first semiconductor region and partly surrounded by the second semiconductor region.

[0015] The following description will be given taking as an example a case where the first conductivity type is p-type and the second conductivity type is n-type.

[0016] FIG. 1 is a schematic top view of the photodetector according to the first embodiment.

[0017] 1, the photodetector 100 includes a cell region 100a and an element isolation region 100b. A plurality of cell regions 100a are arranged in an array. One APD is provided in each cell region 100a.

[0018] 1, the number of cell regions 100a arranged in an array is 49, but the number of cell regions 100a is not particularly limited and may be, for example, 10 to 1000.

[0019] The shape of the cell region 100a is, for example, rectangular when viewed from above. The shape of the cell region 100a is, for example, square when viewed from above. The length of one side of the cell region 100a is, for example, 10 μm or more and 100 μm or less.

[0020] The element isolation regions 100b are provided between the cell regions 100a. The element isolation regions 100b surround each cell region 100a. The element isolation regions 100b have the function of electrically isolating the adjacent cell regions 100a from each other.

[0021] 2 is a schematic cross-sectional view of the photodetector of the first embodiment, taken along the line AA' in FIG.

[0022] The photodetector 100 includes a semiconductor layer 10. The semiconductor layer 10 includes a p-type semiconductor region 11 (first semiconductor region) and an n-type semiconductor region 12 (second semiconductor region). The p-type semiconductor region 11 includes a substrate portion 11a (first portion), a low impurity concentration portion 11b (second portion), and a high impurity concentration portion 11c (third portion).

[0023] The photodetector 100 includes a surface electrode 16 (electrode), a metal region 18, an element isolation insulating layer 22 (insulating layer), a resistive layer 24, a first contact portion 26, a second contact portion 28, a first wiring layer 30, and a second wiring layer 32.

[0024] The semiconductor layer 10 has a first surface (F1 in FIG. 2) and a second surface (F2 in FIG. 2). Hereinafter, the first surface F1 will also be referred to as the front surface. The second surface F2 will also be referred to as the back surface.

[0025] The semiconductor layer 10 is, for example, silicon. The semiconductor layer 10 is, for example, single crystal silicon.

[0026] The cell region 100a includes a semiconductor layer 10. The semiconductor layer 10 of the cell region 100a includes a p-type semiconductor region 11 and an n-type semiconductor region 12.

[0027] The p-type semiconductor region 11 of the cell region 100a includes a substrate portion 11a, a lightly doped portion 11b, and a heavily doped portion 11c.

[0028] The substrate portion 11a is p + The substrate portion 11a is provided on the second face F2 side.

[0029] For example, a ground potential (GND) is applied to the substrate portion 11a.

[0030] The lightly doped portion 11b is p - The lightly doped portion 11b is provided between the substrate portion 11a and the first face F1.

[0031] The low impurity concentration portion 11b is, for example, an epitaxially grown layer formed on the substrate portion 11a by epitaxial growth. The p-type impurity concentration of the low impurity concentration portion 11b is lower than the p-type impurity concentration of the substrate portion 11a.

[0032] The thickness of the low impurity concentration portion 11b in the direction from the first face F1 toward the second face F2 is, for example, not less than 1 μm and not more than 5 μm.

[0033] The high impurity concentration portion 11c is a p-type semiconductor. The high impurity concentration portion 11c is provided between the low impurity concentration portion 11b and the first face F1. The high impurity concentration portion 11c is provided between the low impurity concentration portion 11b and the n-type semiconductor region 12.

[0034] The high impurity concentration portion 11c is formed by, for example, ion-implanting p-type impurities from the surface of the semiconductor layer 10. The p-type impurity concentration of the high impurity concentration portion 11c is higher than the p-type impurity concentration of the low impurity concentration portion 11b.

[0035] The n-type semiconductor region 12 is + The n-type semiconductor region 12 is provided between the p-type semiconductor region 11 and the first face F1. The n-type semiconductor region 12 is provided between the high impurity concentration portion 11c and the first face F1.

[0036] The thickness of the n-type semiconductor region 12 in the direction from the first face F1 to the second face F2 is, for example, not less than 100 nm and not more than 1 μm.

[0037] In the cell region 100a, an APD is formed by the p-type semiconductor region 11 and the n-type semiconductor region 12. In the cell region 100a, the APD is formed by the substrate portion 11a, the low impurity concentration portion 11b, the high impurity concentration portion 11c, and the n-type semiconductor region 12.

[0038] The cell region 100a includes a surface electrode 16. The surface electrode 16 is electrically connected to the n-type semiconductor region 12. The surface electrode 16 contacts the n-type semiconductor region 12.

[0039] The surface electrode 16 is a conductor, such as a metal.

[0040] 3 is an enlarged schematic cross-sectional view of the photodetector of the first embodiment, a cross-sectional view of the cell region 100a, and a cross-section taken along line CC' in FIG.

[0041] Fig. 4 is an enlarged schematic top view of the photodetector of the first embodiment, Fig. 4 is a top view of the first face F1 of the cell region 100a, Fig. 4 is a top view of Fig. 3.

[0042] Fig. 5 is an enlarged schematic cross-sectional view of the photodetector of the first embodiment. Fig. 5 is a cross-section taken along line BB' in Fig. 3. Fig. 5 is a cross-section parallel to the first plane F1.

[0043] The cell region 100a includes a plurality of metal regions 18 on the surface side of the semiconductor layer 10. The plurality of metal regions 18 are arranged on the surface of the semiconductor layer 10 at predetermined intervals.

[0044] The metal region 18 is located, for example, in a trench 17 provided in the surface of the semiconductor layer 10. The metal region 18 is formed, for example, by filling the trench 17 provided in the surface of the semiconductor layer 10 with a metal.

[0045] A portion of the metal region 18 is surrounded by the p-type semiconductor region 11. Another portion of the metal region 18 is surrounded by the n-type semiconductor region 12.

[0046] A portion of the metal region 18 is surrounded by the p-type semiconductor region 11 in a cross section parallel to the first face F1. Another portion of the metal region 18 is surrounded by the n-type semiconductor region 12 in a cross section parallel to the first face F1.

[0047] 5, the lower portion 18a of the metal region 18 is surrounded by the p-type semiconductor region 11. The lower portion 18a of the metal region 18 is surrounded by the high impurity concentration portion 11c.

[0048] For example, as shown in FIG. 4, an upper portion 18b of the metal region 18 is surrounded by the n-type semiconductor region 12.

[0049] The metal region 18 passes through the n-type semiconductor region 12 and reaches the p-type semiconductor region 11. The metal region 18 passes through the n-type semiconductor region 12 and reaches the high impurity concentration portion 11c.

[0050] The metal region 18 contacts the p-type semiconductor region 11. The metal region 18 contacts the high impurity concentration portion 11c. The metal region 18 contacts the n-type semiconductor region 12.

[0051] The junction between the metal region 18 and the p-type semiconductor region 11 is, for example, a Schottky junction. The junction between the metal region 18 and the high impurity concentration portion 11c is, for example, a Schottky junction. The junction between the metal region 18 and the n-type semiconductor region 12 is, for example, a Schottky junction.

[0052] The maximum width between the metal regions 18 on the first face F1 is, for example, 1 nm or more and 1 μm or less. The distance between two adjacent metal regions 18 on the first face F1 is, for example, 10 nm or more and 100 nm or less.

[0053] The metal region 18 is made of a metal, such as aluminum (Al), tungsten (W), silver (Ag), copper (Cu), nickel (Ni), gold (Au), titanium (Ti), or cobalt (Co).

[0054] In addition, on the first face F1 of the cell region 100a, the n-type semiconductor region 12 is surrounded by the p-type semiconductor region 11. On the first face F1 of the cell region 100a, the n-type semiconductor region 12 is surrounded by, for example, a low impurity concentration portion 11b.

[0055] The element isolation region 100b includes a semiconductor layer 10, an element isolation insulating layer 22, and a resistive layer .

[0056] The element isolation region 100b includes the p-type semiconductor region 11. The element isolation region does not include the n-type semiconductor region 12.

[0057] In the element isolation region 100b, the p-type semiconductor region 11 contacts the first face F1. In the element isolation region 100b, for example, the low impurity concentration portion 11b contacts the first face F1.

[0058] The element isolation insulating layer 22 is provided on the first face F1 side of the semiconductor layer 10. The element isolation insulating layer 22 is provided on the surface of the semiconductor layer 10. The element isolation insulating layer 22 is made of, for example, silicon oxide.

[0059] The resistive layer 24 is provided on the element isolation insulating layer 22. The element isolation insulating layer 22 is provided between the semiconductor layer 10 and the resistive layer 24.

[0060] The resistivity of the resistive layer 24 is higher than the resistivity of the surface electrode 16 .

[0061] The resistive layer 24 is a metal or a semiconductor, for example, polycrystalline silicon.

[0062] The resistive layer 24 is electrically connected to the surface electrode 16. One end of the resistive layer 24 is electrically connected to the surface electrode 16 via a first contact portion 26 and a first wiring layer 30.

[0063] The other end of the resistive layer 24 is electrically connected to the second wiring layer 32 via a second contact portion 28 .

[0064] The resistivity of the resistive layer 24 is, for example, higher than the resistivity of the first contact portion 26. The resistivity of the resistive layer 24 is, for example, higher than the resistivity of the second contact portion 28. The resistivity of the resistive layer 24 is, for example, higher than the resistivity of the first wiring layer 30. The resistivity of the resistive layer 24 is, for example, higher than the resistivity of the second wiring layer 32.

[0065] For example, a positive power supply potential Vr is applied to the second wiring layer 32. For example, a positive power supply potential Vr is applied to the surface electrode 16.

[0066] Next, the operation and effects of the photodetector 100 of the first embodiment will be described.

[0067] Fig. 6 is a schematic cross-sectional view of a photodetector 900 of a comparative example. The photodetector 900 of the comparative example is similar to the photodetector 900 of the first embodiment in that it is a SiPM provided with multiple APDs. Fig. 6 is a diagram corresponding to Fig. 2 of the first embodiment.

[0068] The photodetector 900 of the comparative example differs from the photodetector 100 of the first embodiment in that the cell region 100a does not include the metal region 18. The photodetector 900 of the comparative example also differs from the photodetector 100 of the first embodiment in that the low impurity concentration portion 11b is thick.

[0069] Hereinafter, the operation of the SiPM provided with multiple APDs will be described with reference to the photodetector device 900 of the comparative example.

[0070] Fig. 7 is an equivalent circuit diagram of the photodetector of the comparative example, which is also an equivalent circuit diagram of the photodetector of the first embodiment.

[0071] Each cell region 100a is one APD. The APD in each cell region 100a is connected in series with one resistive layer 24. In the photodetector device 900, a plurality of APDs, each with a resistive layer 24 connected in series, are connected in parallel.

[0072] As shown in FIG. 6, a ground potential (GND) is applied to the substrate portion 11a, and a positive power supply voltage (Vr) is applied to the second wiring layer 32, so that a reverse bias voltage is applied to the APD.

[0073] A depletion layer spreads across the pn junction between the n-type semiconductor region 12 and the p-type semiconductor region 11 of the APD in the semiconductor layer 10. In particular, the depletion layer spreads across the low impurity concentration portion 11b, which has a low p-type impurity concentration. The low impurity concentration portion 11b functions as a light absorption layer that absorbs photons.

[0074] For example, when a photon is incident on the depletion layer of the cell region 100a, electron-hole pairs are generated. The generated electrons and holes flow toward the pn junction and are accelerated in the amplification layer, which has a steep potential gradient at the pn junction interface, causing an electron avalanche. The electron avalanche amplifies the current flowing through the APD, allowing, for example, the incidence of one photon to be detected by one cell region 100a.

[0075] As shown in FIG. 7, the photodetector 900 has a plurality of cell regions 100a connected in parallel, and is therefore able to count the number of photons incident simultaneously.

[0076] The resistive layer 24 connected to each cell region 100a functions as a quenching resistor, which has the function of terminating the electron avalanche generated in the APD by dropping its voltage.

[0077] The photodetector 900 has high detection sensitivity, and therefore is required to suppress noise, which includes crosstalk noise and delay noise.

[0078] Crosstalk noise occurs, for example, when secondary photons generated by an electron avalanche are incident on an adjacent cell region 100a. From the viewpoint of improving the detection sensitivity of the photodetector 900, it is preferable that the thickness of the low impurity concentration portion 11b, where a depletion layer is formed and which functions as a light absorption layer, is thick. However, if the thickness of the low impurity concentration portion 11b is increased, secondary photons are more likely to be incident on the adjacent cell region 100a, which may increase the crosstalk noise.

[0079] Furthermore, delay noise occurs when carriers remaining in the low impurity concentration portion 11b cause an electron avalanche over time. Increasing the thickness of the low impurity concentration portion 11b increases the number of remaining carriers, which may increase the delay noise.

[0080] Therefore, from the viewpoint of suppressing noise, it is desirable to reduce the thickness of the low impurity concentration portion 11b that functions as a light absorption layer while maintaining the high detection sensitivity of the photodetector 900.

[0081] In the photodetector 100 of the first embodiment, the cell region 100a includes a metal region 18. The photodetector 100 includes the metal region 18 in the cell region 100a, making it possible to achieve high detection sensitivity.

[0082] Therefore, it is possible to reduce the thickness of the low impurity concentration portion 11b while maintaining high detection sensitivity, thereby suppressing noise in the photodetector 100. This will be described in detail below.

[0083] 8A and 8B are diagrams illustrating the operation and effect of the photodetector of the first embodiment. Fig. 8A is a cross-sectional view of a portion including the metal region 18. Fig. 8B is a band diagram of the region enclosed by the dotted line in Fig. 8A.

[0084] Metal structures on the order of several to several hundred nanometers exhibit extremely large absorption characteristics for light with wavelengths that depend on the metal type, size, shape, etc. This is because the resonance between the free electrons in the metal and the incident light causes the light to become localized in the metal structure. This resonant state is called a plasmon.

[0085] Closely located metals and semiconductors interact through two main processes:

[0086] The first process is PIRET (plasmon-induced resonance energy transfer). The enhanced electric field generated near the metal structure by plasmons acts as if the incident light is trapped and localized in the metal structure. The localized light induces optical excitations across the band gap in the neighboring semiconductor.

[0087] Light localized in the metallic structure can significantly improve the probability of photoexcitation at the pn junction. As shown in Figure 8(b), the carriers generated in the amplifying layer by PIERT, both electrons and holes, are accelerated according to the potential gradient and contribute to the electron avalanche.

[0088] The second process is DET (direct energy transfer). Light localized in a metal structure creates electron-hole pairs in the metal during its deactivation process. If the metal structure and the semiconductor form a Schottky junction, carriers are injected into the semiconductor with a certain probability.

[0089] As shown in Figure 8(b), electron-hole pairs excited in the metal structure cross the Schottky barrier and are injected into the semiconductor layer. The electrons and holes injected into the semiconductor layer are accelerated according to the potential gradient and contribute to the electron avalanche.

[0090] According to the principle explained above, the interaction between the metal region 18 and the semiconductor layer 10 significantly improves the light absorption sensitivity of the photodetector 100. This significantly improves the detection sensitivity of the photodetector 100. This makes it possible to reduce the thickness of the low impurity concentration portion 11b while maintaining high detection sensitivity. This makes it possible to suppress noise in the photodetector 100.

[0091] From the viewpoint of realizing the effect of DET, the junction between the metal region 18 and the p-type semiconductor region 11 is preferably a Schottky junction, and the junction between the metal region 18 and the n-type semiconductor region 12 is preferably a Schottky junction.

[0092] From the viewpoint of realizing a Schottky junction, when the semiconductor layer 10 is silicon, the metal of the metal region 18 is preferably aluminum (Al), tungsten (W), silver (Ag), copper (Cu), nickel (Ni), or gold (Au).

[0093] (Variation) Fig. 9 is an enlarged schematic cross-sectional view of a photodetector according to a modified example of the first embodiment. Fig. 9 is a view corresponding to Fig. 3 of the first embodiment. Fig. 9 is a cross-section taken along CC' in Fig. 10.

[0094] Fig. 10 is an enlarged schematic top view of a photodetector according to a modified example of the first embodiment. Fig. 10 is a top view of the first face F1 of the cell region 100a. Fig. 10 is a top view of Fig. 9.

[0095] The photodetector of the modified example of the first embodiment differs from the photodetector 100 of the first embodiment in that the cell region 100a further includes an insulating region 19 surrounded by a metal region .

[0096] In a cross section parallel to the first face F1, the insulating region 19 is surrounded by the metal region 18. The insulating region 19 is, for example, silicon oxide.

[0097] The metal region 18 is formed of, for example, a metal thin film. For example, the trench 17 provided in the semiconductor layer 10 is filled with the metal thin film, and then the inside of the metal thin film is filled with an insulating material, thereby forming the structure of the cell region 100a shown in FIGS.

[0098] The photodetector of the modified example of the first embodiment also provides the same effects as the photodetector 100 of the first embodiment.

[0099] As described above, according to the first embodiment and the modified example, a photodetector capable of suppressing noise can be realized.

[0100] (Second embodiment) The photodetector of the second embodiment differs from the photodetector of the first embodiment in that the cell region further includes insulating films provided between the metal region and the first semiconductor region and between the metal region and the second semiconductor region. Hereinafter, some of the content that overlaps with the first embodiment may be omitted.

[0101] The photodetector of the second embodiment is a SiPM provided with a plurality of APDs, similar to the first embodiment.

[0102] Fig. 11 is an enlarged schematic cross-sectional view of the photodetector of the second embodiment. Fig. 11 is a view corresponding to Fig. 3 of the first embodiment. Fig. 11 is a cross-section taken along CC' in Fig. 12.

[0103] Fig. 12 is an enlarged schematic top view of the photodetector of the second embodiment. Fig. 12 is a top view of the first face F1 of the cell region 100a. Fig. 12 is a top view of Fig. 11.

[0104] In the photodetector of the second embodiment, the cell region 100a includes an insulating film 20. The insulating film 20 is provided between the metal region 18 and the p-type semiconductor region 11, and between the metal region 18 and the n-type semiconductor region 12. The insulating film 20 is, for example, silicon oxide.

[0105] For example, an insulating film 20 is formed by thermal oxidation in a trench 17 provided in a semiconductor layer 10. Thereafter, the inside of the insulating film 20 is filled with metal, thereby forming the structure of the cell region 100a shown in FIGS.

[0106] In the photodetector of the second embodiment, the metal region 18 is not in contact with the semiconductor layer 10, and therefore the effect of DET cannot be obtained. However, the effect of PIRET can be obtained in the same way as in the photodetector 100 of the first embodiment. Therefore, it is possible to suppress noise in the photodetector.

[0107] As described above, according to the second embodiment, a photodetector capable of suppressing noise can be realized.

[0108] (Third embodiment) The third embodiment of the photodetector device is a photodetector device having a plurality of cell regions arranged in an array and an element isolation region provided between the cell regions, and the cell region includes a semiconductor layer having a first surface and a second surface opposite to the first surface, a first semiconductor region of a first conductivity type provided in the semiconductor layer, a second semiconductor region of a second conductivity type provided between the first semiconductor region and the first surface, an electrode in contact with the second semiconductor region, and a plurality of metal regions provided on the side of the first surface of the semiconductor layer and between the first semiconductor regions and the second semiconductor region.

[0109] The photodetector of the third embodiment differs from the photodetector of the first embodiment in that a second semiconductor region is provided between the metal region and the first semiconductor region. Hereinafter, some of the description overlapping with the first embodiment may be omitted.

[0110] The photodetector of the third embodiment is a SiPM provided with a plurality of APDs, similar to the first embodiment.

[0111] Fig. 13 is an enlarged schematic cross-sectional view of the photodetector of the third embodiment. Fig. 13 is a view corresponding to Fig. 3 of the first embodiment. Fig. 13 is a cross-section taken along CC' in Fig. 14.

[0112] Fig. 14 is an enlarged schematic top view of the photodetector of the third embodiment. Fig. 14 is a top view of the first face F1 of the cell region 100a. Fig. 14 is a top view of Fig. 13.

[0113] In the photodetector of the third embodiment, the metal region 18 is provided on the first face F1 side of the semiconductor layer 10. The metal region 18 is provided on the first face F1. The metal region 18 is provided on the n-type semiconductor region 12. The metal region 18 contacts the n-type semiconductor region 12.

[0114] The n-type semiconductor region 12 is provided between the metal region 18 and the p-type semiconductor region 11. The metal region 18 and the p-type semiconductor region 11 are spaced apart in a direction from the second face F2 toward the first face F1.

[0115] The junction between the metal region 18 and the n-type semiconductor region 12 is, for example, a Schottky junction.

[0116] The photodetector of the third embodiment can obtain the effects of DET and PIRET. Therefore, it is possible to reduce the thickness of the low impurity concentration portion 11b while maintaining high detection sensitivity. Therefore, it is possible to suppress noise in the photodetector.

[0117] As described above, according to the third embodiment, a photodetector capable of suppressing noise can be realized.

[0118] (Fourth embodiment) The photodetector of the fourth embodiment differs from the photodetector of the third embodiment in that it further includes an insulating film provided between the metal region and the second semiconductor region. Hereinafter, some of the content that overlaps with the first or third embodiment may be omitted.

[0119] The photodetector of the fourth embodiment is a SiPM provided with a plurality of APDs, similar to the third embodiment.

[0120] Fig. 15 is an enlarged schematic cross-sectional view of a photodetector according to the fourth embodiment, which corresponds to Fig. 13 of the third embodiment.

[0121] In the photodetector of the fourth embodiment, the cell region 100a includes an insulating film 20. The insulating film 20 is provided between the metal region 18 and the n-type semiconductor region 12. The insulating film 20 is, for example, silicon oxide.

[0122] In the photodetector of the fourth embodiment, the metal region 18 is not in contact with the semiconductor layer 10, and therefore the effect of DET cannot be obtained. However, the effect of PIRET can be obtained in the same way as in the photodetector of the third embodiment. Therefore, it is possible to suppress noise in the photodetector.

[0123] As described above, according to the fourth embodiment, a photodetector capable of suppressing noise can be realized.

[0124] In the first to fourth embodiments, the first conductivity type is p-type and the second conductivity type is n-type. However, the first conductivity type may be n-type and the second conductivity type may be p-type. In this case, for example, a positive power supply potential Vr is applied to the substrate portion 11a. Also, for example, a ground potential (GND) is applied to the second wiring layer 32.

[0125] In the first to fourth embodiments, the semiconductor layer 10 is made of silicon, but the semiconductor layer 10 may be made of a semiconductor other than silicon, such as silicon carbide (SiC).

[0126] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or changed with components of another embodiment. These embodiments and modifications thereof are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0127] 10 Semiconductor layer 11 p-type semiconductor region (first semiconductor region) 12 n-type semiconductor region (second semiconductor region) 16 Surface electrode (electrode) 18 Metal area 18a Lower part (partial) 18b Upper part (another part) 19 Insulation Area 20 insulating film 22 Element isolation insulating layer (insulating layer) 24 Resistance layer 100a cell area 100b Element isolation region 100 Photodetector F1 First Side F2 Second side

Claims

1. A photodetector device comprising a plurality of cell regions arranged in an array and an element isolation region provided between the cell regions, The cell area is a semiconductor layer having a first surface and a second surface opposite to the first surface; a first semiconductor region of a first conductivity type provided in the semiconductor layer; a second semiconductor region of a second conductivity type provided between the first semiconductor region and the first surface; an electrode in contact with the second semiconductor region; a plurality of metal regions, each of which is partially surrounded by the first semiconductor region and partially surrounded by the second semiconductor region; Including, the plurality of metal regions are surrounded by the element isolation region; The plurality of metal regions are arranged at predetermined intervals on the first surface.

2. 2. The photodetector device of claim 1, wherein the metal region contacts the first semiconductor region and the metal region contacts the second semiconductor region.

3. 3. The photodetector device according to claim 2, wherein the junction between the metal region and the first semiconductor region and the junction between the metal region and the second semiconductor region are Schottky junctions.

4. 4. The photodetector device according to claim 1, wherein the cell region further includes an insulating region surrounded by the metal region.

5. 2. The photodetector device according to claim 1, wherein the cell region further includes an insulating film provided between the metal region and the first semiconductor region and between the metal region and the second semiconductor region.

6. The element isolation region is the semiconductor layer; an insulating layer provided on the first surface side of the semiconductor layer; 6. The photodetector device according to claim 1, further comprising: a resistive layer, the insulating layer being provided between the resistive layer and the semiconductor layer, and the resistive layer being electrically connected to the electrode.

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