Light detection device and ranging device

Abstract

A light detection device (1) according to an embodiment of the present disclosure comprises: a first semiconductor substrate (11) which has a first surface (11S1) and a second surface (11S2) that are opposite to each other, has a plurality of pixels arranged in an array in an in-plane direction therein, wherein each of the plurality of pixels is provided with a single photon avalanche diode for multiplying carriers by means of a high electric field region; a second semiconductor substrate (21) which is superposed on the first surface (11S1) side of the first semiconductor substrate (11), has a third surface (21S1) that faces the first surface (11S1) of the first semiconductor substrate (11) and a fourth surface (21S2) that is on the opposite side of the third surface (21S1), and is provided with one or a plurality of transistors; and a light-shielding structure which extends in the superposition direction on at least the fourth surface (21S2) side of the second semiconductor substrate (21) and is provided so as to surround at least each of the plurality of pixels.

Description

Light detection and ranging devices

[0001] The present disclosure relates to, for example, a photodetector and a distance measuring device using an avalanche photodiode.

[0002] For example, Patent Document 1 discloses a photodetector element in which a light-shielding film is provided between a metal pad and a wiring layer stacked on the surface opposite the light-receiving surface of a semiconductor substrate on which an avalanche photodiode element is formed. The light-shielding film has an opening at a location where a contact electrode is to pass through, and is formed over almost the entire surface except for the opening.

[0003] Japanese Patent Application Laid-Open No. 2023-107794

[0004] Incidentally, in photodetection devices, it is required to suppress crosstalk.

[0005] It is desirable to provide a light detection device and a range finder that can suppress crosstalk.

[0006] A photodetector according to one embodiment of the present disclosure includes a first semiconductor substrate having opposing first and second surfaces, a plurality of pixels arranged in an array in an in-plane direction, and a single-photon avalanche diode that multiplies carriers by a high electric field region, provided in each of the plurality of pixels; a second semiconductor substrate stacked on the first surface side of the first semiconductor substrate, having a third surface facing the first surface of the first semiconductor substrate and a fourth surface opposite the third surface, and having one or more transistors provided thereon; and a light-shielding structure extending in the stacking direction at least on the fourth surface side of the second semiconductor substrate and provided so as to surround at least each of the plurality of pixels.

[0007] A distance measuring device according to one embodiment of the present disclosure includes an optical system, a photodetector, and a signal processing circuit that calculates the distance to the object to be measured from the output signal of the photodetector, and has the photodetector according to one embodiment of the present disclosure as the photodetector.

[0008] In the photodetector and distance measuring device according to an embodiment of the present disclosure, a first semiconductor substrate having an avalanche photodiode provided in each of a plurality of pixels and a second semiconductor substrate having one or more transistors provided thereon are stacked. A light-shielding structure is provided on a surface (fourth surface) of the second semiconductor substrate opposite to a surface (third surface) facing the first semiconductor substrate, the surface extending in the stacking direction and surrounding at least each of the plurality of pixels. This prevents light reflected by the second semiconductor substrate from leaking into adjacent pixels.

[0009] FIG. 1 is a cross-sectional schematic diagram illustrating an example of a configuration of a photodetector according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram illustrating an example of a planar configuration of a photodetector corresponding to Sec1 shown in FIG. 1 . FIG. 3 is a schematic diagram illustrating an example of a planar configuration of a photodetector corresponding to Sec2 shown in FIG. 1 . FIG. 4 is a schematic diagram illustrating an example of a planar configuration of a photodetector corresponding to Sec3 shown in FIG. 1 . FIG. 5 is a block diagram illustrating an example of a schematic configuration of the photodetector shown in FIG. 1 . FIG. 6 is an example of an equivalent circuit diagram of a unit pixel of the photodetector shown in FIG. 1 . FIG. 7 is a cross-sectional schematic diagram illustrating an example of a configuration of a photodetector according to Modification 1 of the present disclosure. FIG. 8 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 2 of the present disclosure corresponding to Sec1 shown in FIG. 1 . FIG. 9 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 2 of the present disclosure corresponding to Sec2 shown in FIG. 1 . FIG. 10 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 3 of the present disclosure corresponding to Sec1 shown in FIG. 1 . FIG. 11 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 3 of the present disclosure, corresponding to Sec 2 shown in FIG. 1 . FIG. 12 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 4 of the present disclosure, corresponding to Sec 1 shown in FIG. 1 . FIG. 13 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 4 of the present disclosure, corresponding to Sec 2 shown in FIG. 1 . FIG. 14 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 5 of the present disclosure, corresponding to Sec 1 shown in FIG. 1 . FIG. 15 is a schematic diagram illustrating an example of a planar configuration of a photodetector according to Modification 5 of the present disclosure, corresponding to Sec 2 shown in FIG. 1 . FIG. 16 is a cross-sectional schematic diagram illustrating an example of a configuration of a photodetector according to Modification 6 of the present disclosure. FIG. 17 is a schematic diagram illustrating an example of a planar configuration of a photodetector corresponding to Sec 1 shown in FIG. 16 . FIG. 18 is a schematic diagram illustrating an example of a planar configuration of a photodetector corresponding to Sec 2 shown in FIG. 16 . FIG. 19 is a cross-sectional schematic diagram illustrating an example of a configuration of a photodetector according to Modification 7 of the present disclosure. Fig. 20 is a schematic diagram showing an example of a planar configuration of a photodetector corresponding to Sec3 shown in Fig. 19. Fig. 21 is a schematic cross-sectional view showing an example of a configuration of a photodetector according to Modification 8 of the present disclosure. Fig. 22 is a functional block diagram showing an example of an electronic device using the photodetector shown in Fig. 1 etc.Fig. 23A is a schematic diagram showing an example of the overall configuration of a light detection system using the light detection device shown in Fig. 1. Fig. 23B is a diagram showing an example of the circuit configuration of the light detection system shown in Fig. 23A. Fig. 24 is a block diagram showing an example of the general configuration of a vehicle control system. Fig. 25 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description is one specific example of the present disclosure, and the present disclosure is not limited to the following aspects. Furthermore, the present disclosure is not limited to the arrangement, dimensions, dimensional ratios, etc. of the components shown in the drawings. The description will be given in the following order. 1. Embodiment (Photodetector in which, as a light-shielding structure, through-wiring or through-contacts that penetrate a semiconductor substrate in which transistors are provided are provided between adjacent pixels) 2. Modifications 2-1. Modification 1 (Another Example of the Configuration of the Photodetector) 2-2. Modification 2 (Another Example of the Configuration of the Photodetector) 2-3. Modification 3 (Another Example of the Configuration of the Photodetector) 2-4. Modification 4 (Another Example of the Configuration of the Photodetector) 2-5. Modification 5 (Another Example of the Configuration of the Photodetector) 2-6. Modification 6 (Another Example of the Configuration of the Photodetector) 2-7. Modification 7 (Another Example of the Configuration of the Photodetector) 2-8. Modification 8 (Another Example of the Configuration of the Photodetector) 3. Application Examples 4. Application Examples

[0011] 1. Embodiment FIG. 1 schematically illustrates an example of a cross-sectional configuration of a photodetector (photodetector 1) according to an embodiment of the present disclosure. FIG. 2 schematically illustrates an example of a planar configuration of the photodetector 1 corresponding to Sec1 shown in FIG. 1. FIG. 3 schematically illustrates an example of a planar configuration of the photodetector 1 corresponding to Sec2 shown in FIG. 1. FIG. 4 schematically illustrates an example of a planar configuration of the photodetector 1 corresponding to Sec3 shown in FIG. 1. Note that FIG. 1 illustrates a cross section corresponding to line II shown in FIGS. 2 and 3. The photodetector 1 is applicable to, for example, a range image sensor (a range image device 1000 described below, see FIG. 22 ) that measures distances using a time-of-flight (ToF) method, an image sensor, and the like.

[0012] The photodetector 1 has a stacked configuration in which a semiconductor substrate 11 in which a plurality of unit pixels P are arranged in an array in an in-plane direction and a light-receiving element 12 is provided in each of the plurality of unit pixels P, and a semiconductor substrate 21 in which one or more transistors constituting a readout circuit are provided are stacked. The semiconductor substrate 11 has a first surface 11S1 and a second surface 11S2 that face each other. The semiconductor substrate 21 has a third surface 21S1 and a fourth surface 21S2 that face each other, and the third surface 21S1 is disposed opposite the first surface 11S1 of the semiconductor substrate 11. In the photodetector 1 of this embodiment, through-hole wiring Vx is provided on the fourth surface 21S2 side of the semiconductor substrate 21 in the stacking direction (Z-axis direction), penetrating between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21 and extending to the first surface 11S1 of the semiconductor substrate 11, so as to surround the plurality of unit pixels P.

[0013] Here, the semiconductor substrate 11 corresponds to a specific example of a "first semiconductor substrate" according to an embodiment of the present disclosure. The semiconductor substrate 21 corresponds to a specific example of a "second semiconductor substrate" according to an embodiment of the present disclosure. The light-receiving element 12 corresponds to a specific example of a "single-photon avalanche diode" according to an embodiment of the present disclosure. The through-wiring Vx corresponds to a specific example of a "light-shielding structure" according to an embodiment of the present disclosure.

[0014] [Overall Configuration of Photodetector] Fig. 5 shows a schematic configuration of the photodetector 1 shown in Fig. 1, and Fig. 6 shows an example of an equivalent circuit of a unit pixel P of the photodetector 1 shown in Fig. 1. The photodetector 1 has, for example, a pixel array section 100A in which a plurality of unit pixels P are arranged in an array in the row and column directions. As shown in Fig. 5, the photodetector 1 has a pixel array section 100A and a bias voltage application section 110. The bias voltage application section 110 applies a bias voltage to each unit pixel P of the pixel array section 100A. In this embodiment, a case will be described in which electrons are read out as signal charges.

[0015] As shown in FIG. 6, the unit pixel P includes a light-receiving element 12, a quenching resistance element 120 made of a p-type MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and an inverter 130 made of, for example, a complementary MOSFET.

[0016] The light receiving element 12 converts incident light into an electrical signal by photoelectric conversion and outputs the signal. Additionally, the light receiving element 12 converts incident light (photons) into an electrical signal by photoelectric conversion and outputs a pulse corresponding to the incidence of the photons. The light receiving element 12 is, for example, a SPAD (Single Photon Avalanche Diode) element. The SPAD element has a characteristic that, for example, when a large negative voltage is applied to the cathode, an avalanche multiplication region 12X (depletion layer) is formed, and electrons generated in response to the incidence of one photon undergo avalanche multiplication, resulting in a large current flow. For example, the anode of the light receiving element 12 is connected to the bias voltage application unit 110, and the cathode is connected to the source terminal of the quenching resistance element 120. The anode of the light receiving element 12 is connected to the bias voltage application unit 110, and a device voltage V ＢＤ is applied.

[0017] The quenching resistance element 120 is connected in series with the light-receiving element 12, with its source terminal connected to the cathode of the light-receiving element 12 and its drain terminal connected to a power supply (not shown). Ｅ The quenching resistor 120 detects that the voltage due to the electrons avalanche-multiplied in the light-receiving element 12 is a negative voltage V ＢＤ When the voltage reaches the initial voltage, the photodetector 12 emits the electrons multiplied by the photodetector 12, thereby performing quenching to return the voltage to the initial voltage.

[0018] The inverter 130 has an input terminal connected to the cathode of the light-receiving element 12 and the source terminal of the quenching resistor element 120, and an output terminal connected to a downstream arithmetic processing unit (not shown). The inverter 130 outputs a light-receiving signal based on the carriers (signal charges) multiplied by the light-receiving element 12. More specifically, the inverter 130 shapes the voltage generated by the electrons multiplied by the light-receiving element 12. The inverter 130 then outputs a light-receiving signal (APD OUT) that generates a pulse waveform, such as that shown in FIG. 6 , starting from the arrival time of one font to the arithmetic processing unit. For example, the arithmetic processing unit performs arithmetic processing to determine the distance to the subject based on the timing of the occurrence of a pulse indicating the arrival time of one font in each light-receiving signal, thereby determining the distance for each unit pixel P. Then, based on these distances, a distance image is generated in which distances to the subject detected by multiple unit pixels P are arranged in a plane.

[0019] [Cross-sectional configuration of photodetector] The photodetector 1 is a so-called back-illuminated photodetector in which, for example, a second substrate 20 and a third substrate 30 are stacked in this order on the front surface side of a first substrate 10 (for example, the front surface (first surface 11S1) side of a semiconductor substrate 11 constituting the first substrate 10), and light is received from the back surface side of the first substrate 10 (for example, the back surface (second surface 11S2) of a semiconductor substrate 11 constituting the first substrate 10).

[0020] As described above, the photodetector 1 has the first substrate 10, the second substrate 20, and the third substrate 30 stacked in this order.

[0021] The first substrate 10 includes a semiconductor substrate 11 made of, for example, a silicon substrate and an interlayer insulating layer 19 provided on the first surface 11S1 side of the semiconductor substrate 11. For example, a light receiving portion 13 and a multiplication portion 14 constituting a light receiving element 12 for each unit pixel P are embedded in the semiconductor substrate 11. The semiconductor substrate 11 further includes a pixel separation portion 17 that electrically separates adjacent unit pixels P. The pixel separation portion 17 is provided between a plurality of unit pixels P adjacent in the row and column directions so as to extend between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11. In other words, the pixel separation portion 17 is provided in a lattice pattern in the entire pixel array portion 100A in a plan view. The first surface 11S1 of the semiconductor substrate 11 further includes a contact layer 15 (anode) electrically connected to the light receiving portion 13 and a contact layer 16 (cathode) electrically connected to the multiplication portion 14.

[0022] The second substrate 20 includes, for example, a semiconductor substrate 21 made of a silicon substrate and a multilayer wiring layer 24 provided on the fourth surface 21S2 side of the semiconductor substrate 21. As described above, the semiconductor substrate 21 has opposing third and fourth surfaces 21S1 and 21S2. The third surface 21S1 of the semiconductor substrate 21 faces the first surface 11S1 of the semiconductor substrate 11 via the interlayer insulating layer 19, and the fourth surface 21S2 faces the fifth surface 31S1 of the semiconductor substrate 31 via the multilayer wiring layer 24 of the second substrate 20 and the multilayer wiring layer 32 of the third substrate 30. Some of the transistors constituting the readout circuit are provided on the fourth surface 21S2 of the semiconductor substrate 21. As an example, of the readout circuit, a quench circuit including a quenching resistance element 120 and a pulse shaping circuit including some or all of the inverter circuit are provided on the semiconductor substrate 21, while other circuits are provided on, for example, the semiconductor substrate 31 of the third substrate 30. The semiconductor substrate 21 is further provided with separation portions 22 that separate the semiconductor substrate 21 into a plurality of portions. The separation portions 22 penetrate between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21, and for example, a through wiring Vx is arranged in the separation portion 22 provided between adjacent unit pixels P. The through wiring Vx extends from the fourth surface 21S2 side of the semiconductor substrate 21 to the first surface 11S1 of the semiconductor substrate 11 and is provided so as to surround the plurality of unit pixels P, thereby constituting a light-shielding structure.

[0023] The third substrate 30 has, for example, a semiconductor substrate 31 made of a silicon substrate, and a multilayer wiring layer 32. The semiconductor substrate 21 has opposing fifth and sixth surfaces 31S1 and 31S2, and the multilayer wiring layer 32 is formed on the fifth surface 31S1. The multilayer wiring layer 32 is formed with, for example, a bias voltage application unit 110 including a cathode voltage generation circuit, an anode voltage generation circuit, and a modulation voltage generation circuit, and logic circuits including a vertical drive circuit, a column signal processing circuit, a horizontal drive circuit, and an output circuit.

[0024] In the figures, the symbols "p" and "n" represent p-type semiconductor regions and n-type semiconductor regions, respectively. Furthermore, the "+" or "-" at the end of "p" represents the impurity concentration of the p-type semiconductor region. Similarly, the "+" or "-" at the end of "n" represents the impurity concentration of the n-type semiconductor region. Here, the more "+"s, the higher the impurity concentration, and the more "-"s, the lower the impurity concentration. This also applies to the subsequent figures.

[0025] As described above, the semiconductor substrate 11 has a first surface 11S1 and a second surface 11S2 facing each other. The semiconductor substrate 11 has, for example, a p-well (p) common to a plurality of unit pixels P. The semiconductor substrate 11 is provided with an n-type semiconductor region (n) 111, for example, with an n-type impurity concentration controlled, which constitutes the light receiving section 13 for each unit pixel P. The semiconductor substrate 11 further has a p-type semiconductor region (p ＋ ) 14X and n-type semiconductor region (n ＋ ) 14Y are provided in the semiconductor substrate 11. As a result, a light receiving element 12 is formed for each unit pixel P. The semiconductor substrate 11 further includes a p-type semiconductor region (p) 112, for example, between the light receiving element 12 and a pixel separating portion 17 that electrically separates the adjacent unit pixels P.

[0026] The light receiving element 12 has a multiplication region (avalanche multiplication region 12X) that avalanche-multiplies carriers using a high electric field region. The avalanche multiplication region 12X is formed by applying a large negative voltage to the cathode (contact layer 16), and the light receiving element 12 is a SPAD element that can avalanche-multiply electrons generated by the incidence of one photon.

[0027] The light receiving section 13 has a photoelectric conversion function of absorbing light incident from the second surface 11S2 side of the semiconductor substrate 11 and generating carriers according to the amount of light received. As described above, the light receiving section 13 is configured to include the n-type semiconductor region (n) 111 in which the impurity concentration is controlled to be n-type, and the carriers (electrons) generated in the light receiving section 13 are transferred to the multiplication section 14 by the potential gradient.

[0028] The multiplication section 14 avalanche-multiplies carriers (electrons in this case) generated in the light receiving section 13. The multiplication section 14 is, for example, a p-type semiconductor region (p ＋ ) 14X and an n-type semiconductor region (n) 111 having a higher impurity concentration than the n-type semiconductor region (n) ＋ ) 14Y. ＋ ) 14X and n-type semiconductor region (n ＋ ) 14Y is provided on the first surface 11S1 side, and the n-type semiconductor region (n ＋ ) 14Y, p-type semiconductor region (p ＋ ) 14X are laminated in this order. ＋ The area of ​​the n-type semiconductor region (n ＋ ) 14Y in the XY plane direction, and is provided over the entire surface of the unit pixel P partitioned by the pixel separating portion 17. However, the present invention is not limited to this, and the p-type semiconductor region (p ＋ ) 14X may be formed, for example, inside the p-type semiconductor region (p) 112.

[0029] In the light receiving element 12, a p-type semiconductor region (p ＋ ) 14X and n-type semiconductor region (n ＋ The avalanche multiplication region 12X is formed at the junction with the p-type semiconductor region (p) 14Y. The avalanche multiplication region 12X is formed by the p-type semiconductor region (p ＋ ) 14X and n-type semiconductor region (n ＋ ) 14Y. In the avalanche multiplication region 12X, electrons (e － ) is multiplied.

[0030] The first surface 11S1 of the semiconductor substrate 11 further includes a p-type semiconductor region (p) electrically connected to the n-type semiconductor region (n) 111 that constitutes the light receiving section 13. ＋＋ ) contact layer 15 and an n-type semiconductor region (n ＋ ) 14Y and the n-type semiconductor region (n ＋＋) and a contact layer 16 made of .

[0031] The contact layer 15 is provided, for example, along the pixel separating portion 17 so as to surround the light receiving portion 13, and is connected to the bias voltage application portion 110 as the anode of the light receiving element 12. For example, one contact layer 16 is provided approximately in the center of the unit pixel P, and is connected to the source terminal of the quenching resistance element 120 as the cathode.

[0032] The pixel separating portion 17 electrically separates adjacent unit pixels P and is provided in a grid pattern in the pixel array portion 100A in a plan view, for example, to separate each of the unit pixels P. The pixel separating portion 17 extends between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11, and for example, penetrates the semiconductor substrate 11. The pixel separating portion 17 is composed of, for example, an insulating film 17A and a light-shielding film 17B embedded in the insulating film 17A. The pixel separating portion 17 may be provided from the first surface 11S1 side of the semiconductor substrate 11, or may be formed from the second surface 11S2 side of the semiconductor substrate 11.

[0033] The insulating film 17A is made of, for example, silicon oxide (SiO ｘ The light-shielding film 17B is formed using, for example, a metal material having light-shielding properties, such as tungsten (W), aluminum (Al), copper (Cu), cobalt (Co), nickel (Ni), or titanium (Ti), or a silicon compound thereof. Alternatively, the light-shielding film 17B may be formed using polysilicon (Poly-Si). The light-shielding film 17B may be provided with a widened portion 17X formed on the second surface 11S2 of the semiconductor substrate 11 in order to suppress the incidence of obliquely incident light between adjacent unit pixels P.

[0034] For example, a layer having a fixed charge (fixed charge layer 18) may be provided on the side and bottom surfaces of the pixel separation portion 17 and the second surface 11S2 of the semiconductor substrate 11. The fixed charge layer 18 may be a film having a positive fixed charge or a film having a negative fixed charge.

[0035] The fixed charge layer 18 is preferably formed using a semiconductor material or a conductive material having a wider band gap than the semiconductor substrate 11. This makes it possible to suppress the generation of dark current at the interface of the semiconductor substrate 11. The fixed charge layer 18 is preferably formed using a material such as hafnium oxide (HfO ｘ ), aluminum oxide (AlO ｘ ), zirconium oxide (ZrO ｘ ), tantalum oxide (TaO ｘ ), titanium oxide (TiO ｘ ), lanthanum oxide (LaO ｘ ), praseodymium oxide (PrO ｘ ), cerium oxide (CeO ｘ ), neodymium oxide (NdO ｘ ), promethium oxide (PmO ｘ ), samarium oxide (SmO ｘ ), europium oxide (EuO ｘ ), gadolinium oxide (GdO ｘ ), terbium oxide (TbO ｘ ), dysprosium oxide (DyO ｘ ), holmium oxide (HoO ｘ ), thulium oxide (TmO ｘ ), ytterbium oxide (YbO ｘ ), lutetium oxide (LuO ｘ ), yttrium oxide (YO ｘ ), hafnium nitride (HfN ｘ ), aluminum nitride (AlN ｘ ), hafnium oxynitride (HfO ｘ N ｙ ) and aluminum oxynitride (AlO ｘ N ｙ ) etc.

[0036] For example, a wiring layer consisting of one or more wires may be formed in the interlayer insulating layer 19. The wiring layer is for supplying a voltage to be applied to the semiconductor substrate 11 and the light-receiving element 12, or for extracting carriers generated in the light-receiving element 12, for example.

[0037] The wiring layer is formed using, for example, aluminum (Al) or copper (Cu).

[0038] The interlayer insulating layer is made of, for example, silicon oxide (SiO ｘ ), TEOS, silicon nitride (SiN ｘ ) and silicon oxynitride (SiO ｘ N ｙ ) or a laminated film made of two or more of these.

[0039] As described above, the semiconductor substrate 21 has a third surface 21S1 and a fourth surface 21S2 that face each other. For example, as shown in FIG. 3, the semiconductor substrate 21 is separated into a plurality of islands by separation portions 22 that penetrate between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21. One or a plurality of transistors that constitute a readout circuit are formed on the fourth surface 21S2 of the semiconductor substrate 21 that is separated into islands. For example, a p-MOS transistor 211 and an n-MOS transistor 212 that constitute a pulse shaping circuit including an inverter circuit are formed on each semiconductor substrate 21 that is separated into islands. The p-MOS transistor 211 has, for example, a planar structure and includes a gate 241 and a p-type semiconductor region (p ＋ The n-MOS transistor 212 has, for example, a planar structure, and includes a gate 241 and an n-type semiconductor region (n ＋ The semiconductor substrate 21 on which the p-MOS transistor 211 and the n-MOS transistor 212 are formed has an n-type semiconductor region (n ＋ ) or p-type semiconductor region (p ＋ ) is formed as a well contact.

[0040] The isolation portion 22 corresponds to a specific example of a "first isolation portion" according to an embodiment of the present disclosure. As described above, the isolation portion 22 is intended to separate the semiconductor substrate 21 into a plurality of islands. The isolation portion 22 has a so-called FTI (Full Trench Isolation) structure that penetrates between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21. The isolation portion can be formed, for example, by forming an opening in the semiconductor substrate 21 on the fourth surface 21S2 side and filling the opening with an insulating film.

[0041] The multilayer wiring layer 24 includes a gate 241, a wiring layer 242 consisting of one or more wirings, a plurality of pad portions 244, and through contacts V1a, V1b and a contact V2 that penetrate the semiconductor substrate 21 in the Z-axis direction, formed within an interlayer insulating layer 243.

[0042] The wiring layer 242, like the wiring layer formed in the interlayer insulating layer 19, serves to, for example, supply voltage to be applied to the semiconductor substrate 11 and the light-receiving element 12 and extract carriers generated in the light-receiving element 12. Some of the wiring in the wiring layer 242 is electrically connected to the contact layer 15 via a through-contact V1a. Some of the wiring in the wiring layer 242 is electrically connected to the contact layer 16 via a through-contact V1b. Some of the wiring in the wiring layer 242 is also used to supply voltage to the semiconductor substrate 21 and the p-MOS transistor 211 and n-MOS transistor 212 formed on the semiconductor substrate 21. For example, some of the wiring in the wiring layer 242 is electrically connected to the gates 241 of the p-MOS transistor 211 and the n-MOS transistor 212 via contact V2, and to the sources 211S, 212S and drains 211D, 212D and well contacts of the p-MOS transistor 211 and the n-MOS transistor 212, although not shown.

[0043] The gate 241 and the wiring layer 242 are formed using, for example, aluminum (Al) or copper (Cu).

[0044] The interlayer insulating layer 243 is made of, for example, silicon oxide (SiO ｘ ), TEOS, silicon nitride (SiNｘ ) and silicon oxynitride (SiO ｘ N ｙ ), a low-k film such as fluorine- or carbon-doped glass, or a laminated film made of two or more of these.

[0045] The pads 244 are used for connection to the third substrate 30, and are embedded in the surface of the interlayer insulating layer 243 on the side opposite to the semiconductor substrate 31. The pads 244 are formed using, for example, copper (Cu).

[0046] The through contacts V1a, V1b, and V2 are formed using a metal material having light-shielding properties, such as tungsten (W), aluminum (Al), copper (Cu), cobalt (Co), nickel (Ni), or titanium (Ti), or a silicon compound thereof.

[0047] The multilayer wiring layer 24 further includes through-hole wirings Vx that penetrate the semiconductor substrate 21 in the Z-axis direction. When viewed, for example, per unit pixel P, the through-hole wirings Vx are arranged symmetrically with respect to, for example, the X-axis direction and the Y-axis direction in a planar view. Specifically, as shown in FIGS. 2 and 3 , the through-hole wirings Vx are continuously formed to surround each of the unit pixels P and extend from the fourth surface 21S2 of the semiconductor substrate 21 to the first surface 11S1 of the semiconductor substrate 11. In other words, the through-hole wirings Vx are provided between adjacent unit pixels P and are arranged in a grid pattern in the pixel array section 100A in a planar view. That is, the through-hole wirings Vx are provided at the same positions as the pixel separation sections 17 provided on the first substrate 10 so as to overlap with them in a planar view. The through-hole wirings Vx are formed using, for example, a metal material having light-shielding properties, such as tungsten (W). This makes it possible to prevent light L generated in the multiplication section 14 from leaking into adjacent unit pixels P due to reflection by the wiring layer 242, for example, as shown in FIG.

[0048] The through wiring Vx may be electrically connected to other wirings, or may be in an electrically floating state without being connected to other wirings.

[0049] The through wiring Vx can be formed as follows. First, the semiconductor substrate 21 is bonded to the interlayer insulating layer 19 of the first substrate 10 so that the first surface 11S1 of the semiconductor substrate 11 faces the third surface 21S1 of the semiconductor substrate 21. Next, the fourth surface 21S2 of the semiconductor substrate 21 is polished, for example, by chemical mechanical polishing (CMP), to thin the semiconductor substrate 21 to a predetermined thickness, and then openings are formed by photolithography and etching to separate the semiconductor substrate 21 into multiple islands. Next, an insulating film is buried in the openings by, for example, chemical vapor deposition (CVD) or atomic layer deposition (ALD), to form the isolation portions 22. Note that, as in the photodetector 1B described below, the semiconductor substrate 21 may have an isolation region 23 having a so-called shallow trench isolation (STI) structure that isolates transistors. Next, after forming the p-MOS transistor 211, the n-MOS transistor 212, etc. on each semiconductor substrate 21 separated into islands, an interlayer insulating layer 243 is formed. Subsequently, openings are formed by photolithography and etching on the gates 241 of the p-MOS transistor 211 and the n-MOS transistor 212, on the semiconductor substrate 21, and through the isolation portion 22. After that, a metal film (e.g., tungsten (W)) is embedded in these openings by, for example, CVD or ALD, and the metal film formed on the interlayer insulating layer 243 is removed by CMP. As a result, for example, through contacts V1a, V1b, and a contact V2 that electrically connect the contact layers 15 and 16 provided on the semiconductor substrate 11 to the p-MOS transistor 211 and the n-MOS transistor 212 are formed, along with through wiring Vx.

[0050] The through wiring Vx is not limited to the above, and may be formed in a process different from that for forming the through contacts V1a, V1b, and the contact V2.

[0051] As described above, the semiconductor substrate 31 has the opposing fifth surface 31S1 and sixth surface 31S2. A plurality of transistors that form a logic circuit are formed on the fifth surface 31S1 of the semiconductor substrate 31.

[0052] The multilayer wiring layer 32 includes, for example, a gate wiring 321 of a transistor constituting a logic circuit, and wiring layers 322, 323, 324, and 325 including one or more wirings, stacked in this order from the semiconductor substrate 21 side with an interlayer insulating layer 326 in between. A plurality of pad electrodes 327 are embedded in the surface of the interlayer insulating layer 326 opposite to the semiconductor substrate 21 side (surface 32S1 of the multilayer wiring layer 32). The plurality of pad electrodes 327 are electrically connected to some of the wirings of the wiring layer 325 through vias V3.

[0053] The interlayer insulating layer 326 is made of, for example, silicon oxide (SiO ｘ ), TEOS, silicon nitride (SiN ｘ ) and silicon oxynitride (SiO ｘ N ｙ ), fluorine- or carbon-doped glass, or the like, or a laminated film made of two or more of these.

[0054] The gate wiring 321 and the wiring layers 322, 323, 324, and 325 are formed using, for example, aluminum (Al), copper (Cu), tungsten (W), or the like, similar to the wiring layer 242.

[0055] The pad electrode 327 is exposed on the bonding surface with the second substrate 20 (surface 32S1 of the multilayer wiring layer 32), and is used, for example, for connection to the second substrate 20. Like the pad portion 244, the pad electrode 327 is formed using, for example, copper (Cu).

[0056] On the light-receiving surface (second surface 11S2) side of the semiconductor substrate 11, for example, a microlens 43 is provided for each unit pixel P via a protective layer 41 and a color filter 42. The color filter 42 may be omitted.

[0057] The microlens 43 is a lens that focuses light incident from above onto the light receiving element 12. For example, the microlens 43 is made of silicon oxide (SiO ｘ ) or organic film.

[0058] In the photodetector 1, for example, the first substrate 10 and the second substrate 20 are electrically connected via through contacts V1a and V1b. The second substrate 20 and the third substrate 30 are bonded, for example, by CuCu bonding between the pad electrodes 327 and pad portions 244 formed on the respective bonding surfaces. This electrically connects the first substrate 10, the second substrate 20, and the third substrate 30 to one another.

[0059] [Operations and Effects] The photodetector 1 according to the present embodiment has a stacked configuration in which a semiconductor substrate 11 in which a plurality of unit pixels P are arranged in an in-plane array and a light-receiving element 12 is provided in each of the plurality of unit pixels P is stacked with a semiconductor substrate 21 in which one or more transistors constituting a readout circuit are provided. In this embodiment, as a light-shielding structure, through-hole wiring Vx extends from the surface (fourth surface 21S2) of the semiconductor substrate 21 opposite the surface (third surface 21S1) facing the semiconductor substrate 11 to the surface (first surface 11S1) of the semiconductor substrate 21 facing the semiconductor substrate 11. The through-hole wiring Vx is provided, for example, on the pixel separation portion 17 so as to continuously surround the plurality of unit pixels P. This prevents, for example, light L reflected on the fourth surface (21S2) of the semiconductor substrate 21 from leaking into adjacent unit pixels P. This will be described below.

[0060] In the SPAD technology, a high bias voltage is applied to multiply carriers generated by photoelectric conversion of incident light, allowing a large signal to be extracted.

[0061] In photodetectors with such SPAD elements arranged in an array, transistors for driving pixels are provided on a semiconductor substrate (second substrate) separate from the semiconductor substrate (first substrate) on which the SPAD elements are formed, and these substrates are stacked to form a three-dimensional structure. In such photodetectors, through-contacts for connecting electrodes from the surface of the second substrate opposite the surface facing the first substrate to the first substrate, and wiring connecting contacts for connecting electrodes to transistors formed on the surface of the second substrate opposite the surface facing the first substrate, are generally formed of a light-reflective metal film such as copper (Cu). Reflection from this metal film causes light leakage (crosstalk) into adjacent pixels. For example, in SPAD elements, hot carrier light emission occurs during avalanche multiplication, and this light can reach the wiring and cause crosstalk.

[0062] In contrast to this, in the present embodiment, as described above, the light-shielding structure is such that the through wirings Vx extend from the surface (fourth surface 21S2) of the semiconductor substrate 21, on which one or more transistors constituting the readout circuit are provided, opposite the surface (third surface 21S1) facing the semiconductor substrate 11, through the semiconductor substrate 21 to the surface (first surface 11S1) of the semiconductor substrate 11 facing the semiconductor substrate 21, so as to continuously surround a plurality of unit pixels P. This prevents light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 from leaking into adjacent unit pixels P.

[0063] As described above, the photodetector 1 of this embodiment can suppress crosstalk.

[0064] Furthermore, in this embodiment, the through wiring Vx that constitutes the light-shielding structure can be formed together with the through contacts V1a, V1b and contact V2 that electrically connect the contact layers 15, 16 provided on the semiconductor substrate 11 to the p-MOS transistor 211 and the n-MOS transistor 212. Therefore, it is possible to realize a light-shielding structure that suppresses crosstalk without increasing the number of manufacturing steps.

[0065] However, because the above-mentioned wiring patterns can be designed relatively freely, for example, regions with different wiring densities are formed within a pixel, and the amount of light reflection varies depending on the density of the wiring. In other words, in a photodetector employing the above-mentioned three-dimensional structure, the asymmetry of the wiring pattern causes crosstalk to be asymmetric with respect to the pixels above, below, left, and right, resulting in variations in pixel characteristics. For example, metal plugs such as tungsten (W) used for through contacts and contacts absorb wavelengths in the near-infrared region detected by the SPAD element, which complicates the impact of light generated by internal emission on adjacent pixels.

[0066] In contrast to this, in the present embodiment, when viewed in units of unit pixels P, for example, the through wirings Vx constituting the light-shielding structure are continuously formed so as to surround each of the plurality of unit pixels P so as to be symmetrical with respect to, for example, the X-axis direction and the Y-axis direction in a plan view, thereby making it possible to reduce the asymmetry of pixel characteristics.

[0067] Next, Modifications 1 to 8, application examples, and applied examples of the present disclosure will be described. In the following, the same components as those in the above embodiment will be given the same reference numerals, and the description thereof will be omitted as appropriate.

[0068] 7 is a schematic diagram illustrating an example of a cross-sectional configuration of a light detection device (light detection device 1A) according to Modification 1 of the present disclosure. Like the light detection device 1 of the above embodiment, the light detection device 1A is applicable to, for example, a range image sensor (a range image device 1000 described below) or an image sensor that performs distance measurement by the ToF method.

[0069] In the above embodiment, an example was shown in which the through wiring Vx constituting the light-shielding structure extends in the Z-axis direction on the fourth surface 21S2 side of the semiconductor substrate 21, penetrates between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21, and contacts the first surface 11S1 of the semiconductor substrate 11. However, this is not limiting. In the photodetector 1A of this modified example, a gap is provided between the semiconductor substrate 11 and the end of the through wiring Vx on the semiconductor substrate 11 side, which extends in the Z-axis direction on the fourth surface 21S2 side of the semiconductor substrate 21 and penetrates between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21. An interlayer insulating layer constituting the interlayer insulating layer 19 is formed between the end on the semiconductor substrate 11 side and the semiconductor substrate 11. Except for this point, the photodetector 1A has substantially the same configuration as the photodetector 1 of the above embodiment.

[0070] Even with this configuration, the photodetector 1A of this modification can reduce leakage of light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 into adjacent unit pixels P, thereby suppressing crosstalk. Furthermore, in the photodetector 1A of this modification, a margin can be secured for the process of forming the through wiring Vx by allowing a gap between the end of the through wiring Vx on the semiconductor substrate 11 side and the semiconductor substrate 11, and therefore the through wiring Vx having a light-shielding structure can be formed more easily than in the above embodiment.

[0071] (2-2. Modification 2) Fig. 8 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 2 of the present disclosure, which corresponds to Sec1 shown in Fig. 1. Fig. 9 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 2 of the present disclosure, which corresponds to Sec2 shown in Fig. 1.

[0072] In the above embodiment, an example has been shown in which the through wirings Vx constituting the light-shielding structure are continuously formed so as to surround each of the plurality of unit pixels P, but the present invention is not limited to this. In the photodetector 1 of this modified example, the through wirings Vx constituting the light-shielding structure are formed intermittently. Specifically, as shown in FIGS. 8 and 9 , the photodetector 1 of this modified example has notches provided at the intersections of the through wirings Vx extending in the X-axis direction and the Y-axis direction. Except for this point, the photodetector 1 of this modified example has substantially the same configuration as the photodetector 1 of the above embodiment.

[0073] Even with this configuration, the photodetector 1 of this modified example can reduce leakage of light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 into adjacent unit pixels P, thereby suppressing crosstalk. Furthermore, in this modified example, notches are provided at the intersections of the through-wires Vx extending in the X-axis direction and the Y-axis direction, so that the influence of stress due to stress and the like can be reduced compared to the through-wires Vx of the above embodiment.

[0074] (2-3. Modification 3) Fig. 10 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 3 of the present disclosure, which corresponds to Sec1 shown in Fig. 1. Fig. 11 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 3 of the present disclosure, which corresponds to Sec2 shown in Fig. 1.

[0075] In the above embodiment, an example has been shown in which the through wirings Vx constituting the light-shielding structure are continuously formed so as to surround each of the plurality of unit pixels P, but the present invention is not limited to this. In the photodetector 1 of this modified example, the through wirings Vx constituting the light-shielding structure are formed intermittently. Specifically, as shown in FIGS. 10 and 11 , the photodetector 1 of this modified example has a plurality of pillar-shaped through wirings Vx arranged between adjacent unit pixels P. Except for this point, the photodetector 1 of this modified example has substantially the same configuration as the photodetector 1 of the above embodiment.

[0076] The gaps W between the plurality of pillar-shaped through-wires Vx are preferably less than the wavelength (detection wavelength) at which photoelectric conversion is performed in the light receiving element 12. This prevents light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 from leaking into adjacent unit pixels P due to transmission between the plurality of pillar-shaped through-wires Vx.

[0077] Even with this configuration, the photodetector 1 of this modification, like the above embodiment, can prevent light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 from leaking into adjacent unit pixels P, thereby suppressing crosstalk. Also, like the above modification 2, this modification can reduce the influence of stress due to stress and the like, compared to the through wiring Vx of the above embodiment.

[0078] (2-4. Modification 4) Fig. 12 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 4 of the present disclosure, which corresponds to Sec1 shown in Fig. 1. Fig. 13 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 4 of the present disclosure, which corresponds to Sec2 shown in Fig. 1.

[0079] In the above-described embodiment and modified examples 1 to 3, examples have been shown in which the through wirings Vx constituting the light-shielding structure are provided between adjacent unit pixels P, that is, in plan view, at the same position as the pixel separating portion 17 provided on the first substrate 10 so as to overlap therewith, but the present invention is not limited to this. The through wirings Vx constituting the light-shielding structure only need to be provided in the vicinity of the pixel separating portion 17 in plan view, and in the photodetector 1 of this modified example, the through wirings Vx constituting the light-shielding structure are provided at positions offset in the X-axis direction, the Y-axis direction, or both directions from between adjacent unit pixels P. Except for this point, the photodetector 1 of this modified example has substantially the same configuration as the photodetector 1 of the above-described embodiment.

[0080] Even with this configuration, the photodetector 1 of this modified example can reduce leakage of light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 into adjacent unit pixels P, thereby suppressing crosstalk.

[0081] (2-5. Modification 5) Fig. 14 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 5 of the present disclosure, which corresponds to Sec1 shown in Fig. 1. Fig. 15 is a schematic diagram illustrating an example of a planar configuration of a photodetector 1 according to Modification 5 of the present disclosure, which corresponds to Sec2 shown in Fig. 1.

[0082] For example, when a plurality of pillar-shaped through wirings Vx are arranged at predetermined intervals as a light-shielding structure as in the above-mentioned variant example 3, the pillar-shaped through wirings Vx may be arranged in two alternating rows between adjacent unit pixels P so as to fill the spaces between the adjacent through wirings Vx, as shown in Figures 14 and 15.

[0083] Even with this configuration, the photodetector 1 of this modified example can reduce leakage of light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 into adjacent unit pixels P, thereby suppressing crosstalk.

[0084] (2-6. Modification 6) FIG. 16 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1B) according to modification 6 of the present disclosure. FIG. 17 is a schematic diagram showing an example of a planar configuration of photodetector 1B corresponding to Sec1 shown in FIG. 16. FIG. 18 is a schematic diagram showing an example of a planar configuration of photodetector 1 corresponding to Sec2 shown in FIG. 16. Like the photodetector 1 of the above embodiment, the photodetector 1B is applicable to, for example, a range image sensor (range image device 1000 described below) or an image sensor that performs distance measurement by the ToF method.

[0085] In the above embodiment, an example was shown in which the light-shielding structure includes through-hole wirings Vx extending in the Z-axis direction on the fourth surface 21S2 side of the semiconductor substrate 21 and penetrating between the third surface 21S1 and the fourth surface 21S2 of the semiconductor substrate 21, provided between adjacent unit pixels P. However, this is not limited to this. In the photodetector 1B of this modified example, the light-shielding structure includes multiple contacts Vy extending in the Z-axis direction on the fourth surface 21S2 side of the semiconductor substrate 21, with their ends in contact with the same surface as the fourth surface 21S2 of the semiconductor substrate 21, provided between adjacent unit pixels P. The contacts Vy correspond to a specific example of a "connection wiring" according to one embodiment of the present disclosure. Except for this point, the photodetector 1B of this modified example has substantially the same configuration as the photodetector 1 of the above embodiment.

[0086] Furthermore, in the photodetector 1B, an etching stopper layer 25 having an etching rate different from that of the interlayer insulating layer 243 may be provided on the fourth surface 21S2 of the semiconductor substrate 21. This allows the contact Vy to be disposed at a desired position in the Z-axis direction within the unit pixel P. Specifically, the contact Vy can be disposed in the isolation portion 22 having an FTI structure or the element isolation region 23 having an STI structure. The element isolation region 23 corresponds to a specific example of a "second isolation portion" as an embodiment of the present disclosure. The element isolation region 23 electrically isolates each transistor when multiple transistors are provided on each semiconductor substrate 21 separated by the isolation portion 22.

[0087] The end of the contact Vy facing the fourth surface 21S2 of the semiconductor substrate 21 may be connected to an active region, such as the sources 211S, 212S or drains 211D, 212D, of the p-MOS transistor 211 or the n-MOS transistor 212 provided on the semiconductor substrate 21, the gate 241, or a well contact. The end of the contact Vy opposite the end facing the fourth surface 21S2 of the semiconductor substrate 21 may or may not be connected to the wiring layer 242. In other words, the contact Vy may be a so-called dummy pattern that is not connected to other wiring or the like. This allows the contact Vy to alleviate wiring constraints.

[0088] Even with this configuration, the photodetector device 1B of this modified example can reduce leakage of light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 into adjacent unit pixels P, thereby suppressing crosstalk, as in the above embodiment.

[0089] (2-7. Modification 7) Fig. 19 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1C) according to modification 7 of the present disclosure. Fig. 20 is a schematic diagram showing an example of a planar configuration of the photodetector 1C corresponding to Sec3 shown in Fig. 19. Like the photodetector 1 of the above embodiment, the photodetector 1C is applicable to, for example, a range image sensor (range image device 1000 described below) or an image sensor that measures distance by the ToF method.

[0090] The wiring layer 242 formed in the multilayer wiring layer 24 of the second substrate 20, which causes crosstalk, has an asymmetric wiring pattern within a pixel, with dense and sparse wiring regions present, as can be seen from, for example, Fig. 4 . In the photodetector 1C of this modification, as shown in Fig. 20 , a plurality of contacts Vy forming a light-shielding structure are disposed in the sparse wiring region within the unit pixel P. Except for this point, the photodetector 1C of this modification has substantially the same configuration as the photodetector 1 of the above embodiment.

[0091] In this way, in the photodetector 1C of this modified example, a plurality of contacts Vy are arranged in an area where the wiring is sparse within the unit pixel P. This makes it possible to block light L reflected by, for example, the wiring layer 242 on the fourth surface (21S2) side of the semiconductor substrate 21 with the plurality of contacts Vy, while also reducing variations in pixel characteristics due to asymmetry in the wiring pattern.

[0092] 21 is a schematic diagram illustrating an example of a cross-sectional configuration of a photodetector (photodetector 1D) according to modification 8 of the present disclosure. Similar to the photodetector 1 of the above embodiment, the photodetector 1D is applicable to, for example, a range image sensor (range image device 1000 described below) or an image sensor that measures distance using the ToF method.

[0093] In the above embodiment, an example was shown in which the through wiring Vx that constitutes the light-shielding structure is in contact with the insulating film 17A of the pixel separating portion 17 provided in the semiconductor substrate 11, but the present invention is not limited to this. In a photodetector 1D of this modified example, the light-shielding film 18B that constitutes the pixel separating portion 17 extends to the fourth surface 21S2 of the second substrate 20, and the light-shielding film 18B and the contact Vy are connected. Except for this point, a photodetector 1C of this modified example has substantially the same configuration as the photodetector 1 of the above embodiment.

[0094] As described above, in the photodetector 1D of this modification, the light-shielding film 17B constituting the pixel separator 17 is used as a component of the "light-shielding structure" of the present disclosure, and extends in the Z-axis direction on the fourth surface 21S2 side of the semiconductor substrate 21, with its ends connected to a plurality of contacts Vy that are in contact with the same surface as the fourth surface 21S2 of the semiconductor substrate 21. Even with this configuration, the photodetector 1D of this modification can reduce leakage of light L reflected on the fourth surface (21S2) side of the semiconductor substrate 21 into adjacent unit pixels P, thereby suppressing crosstalk, as in the above embodiment.

[0095] 21 shows an example in which the contact Vy and the light-shielding film 17B are in contact with each other, but the present invention is not limited to this. For example, a gap may be formed between the contact Vy and the light-shielding film 17B, as in Modification 1.

[0096] 22 shows an example of the schematic configuration of a distance image device 1000 as an electronic device equipped with a photodetector (e.g., photodetector 1) according to any of the above-described embodiments and Modifications 1 to 8. This distance image device 1000 corresponds to a specific example of a "distance measuring device" of the present disclosure.

[0097] The range image device 1000 includes, for example, a light source device 1100 , an optical system 1200 , a light detection device 1 , an image processing circuit 1300 , a monitor 1400 , and a memory 1500 .

[0098] The distance image device 1000 can obtain a distance image corresponding to the distance to the illuminated object 1600 by receiving light (modulated light or pulsed light) projected from the light source device 1100 toward the illuminated object 1600 and reflected from the surface of the illuminated object 1600.

[0099] The optical system 1200 is configured with one or more lenses, and guides image light (incident light) from the irradiation object 1600 to the photodetector 1, forming an image on the light receiving surface (sensor section) of the photodetector 1.

[0100] The image processing circuit 1300 performs image processing to construct a distance image based on the distance signal supplied from the light detection device 1, and the distance image (image data) obtained by this image processing is supplied to the monitor 1400 for display, or supplied to the memory 1500 for storage (recording).

[0101] In the range imaging device 1000 configured in this manner, by applying the above-described photodetector (for example, the photodetector 1), it is possible to calculate the distance to the illuminated object 1600 based solely on the light-receiving signals from the highly stable unit pixels P, and generate a highly accurate range image. In other words, the range imaging device 1000 can acquire a more accurate range image.

[0102] (Application Example 2) Fig. 23A is a schematic diagram illustrating an example of the overall configuration of a light detection system 2000 including a light detection device (e.g., the light detection device 1). Fig. 23B is a diagram illustrating an example of the circuit configuration of the light detection system 2000. The light detection system 2000 includes a light emitting device 2001 serving as a light source unit that emits infrared light L2, and a light detection device 2002 serving as a light receiving unit. The light detection device 2002 may be, for example, the light detection device 1 described above. The light detection system 2000 may further include a system control unit 2003, a light source driving unit 2004, a sensor control unit 2005, a light source side optical system 2006, and a camera side optical system 2007.

[0103] The photodetector 2002 can detect light L1 and light L2. Light L1 is external ambient light reflected by the object (measurement target) 2100 ( FIG. 23A ). Light L2 is light emitted by the light-emitting device 2001 and then reflected by the object 2100. Light L1 is, for example, visible light, and light L2 is, for example, infrared light. Light L1 can be detected by a photoelectric conversion unit in the photodetector 2002, and light L2 can be detected by a photoelectric conversion region in the photodetector 2002. Image information of the object 2100 can be obtained from light L1, and distance information between the object 2100 and the photodetector system 2000 can be obtained from light L2. The photodetector system 2000 can be installed in, for example, an electronic device such as a smartphone or a mobile object such as a car. The light-emitting device 2001 can be configured, for example, by a semiconductor laser, a surface-emitting semiconductor laser, or a vertical-cavity surface-emitting laser (VCSEL). The method of detecting the light L2 emitted from the light-emitting device 2001 by the photodetector 2002 can be, for example, an iTOF method, but is not limited to this. In the iTOF method, the photoelectric conversion unit can measure the distance to the subject 2100, for example, by using the time-of-flight (TOF) of light. The method of detecting the light L2 emitted from the light-emitting device 2001 by the photodetector 2002 can also be, for example, a structured light method or a stereo vision method. For example, in the structured light method, a predetermined pattern of light is projected onto the subject 2100, and the distance between the photodetector system 2000 and the subject 2100 can be measured by analyzing the distortion of the pattern. In addition, in the stereo vision method, for example, two or more cameras are used to acquire two or more images of the subject 2100 viewed from two or more different viewpoints, thereby measuring the distance between the photodetector system 2000 and the subject. The light emitting device 2001 and the light detecting device 2002 can be controlled synchronously by a system control unit 2003 .

[0104] 4. Application Examples (Application Examples to Mobile Bodies) The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, a robot, construction machinery, or agricultural machinery (tractor).

[0105] FIG. 24 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0106] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 24, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0107] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0108] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0109] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0110] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0111] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0112] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0113] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0114] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0115] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying the passengers of the vehicle or the outside of the vehicle of information. In the example of Fig. 24, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0116] FIG. 25 is a diagram showing an example of the installation position of the imaging unit 12031.

[0117] In FIG. 25, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0118] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0119] 25 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0120] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0121] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which travels autonomously without relying on driver operation.

[0122] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0123] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0124] The above describes the embodiments, variations 1 to 8, and application examples. However, the present disclosure is not limited to the above embodiments, and various modifications are possible. For example, it is not necessary to include all of the components described in the above embodiments. Conversely, other layers may be included. For example, if the photodetector 1 detects light other than visible light (e.g., near-infrared light (IR)), the color filter 42 may be omitted.

[0125] The polarity of the semiconductor regions constituting the photodetector of the present disclosure may be reversed.Furthermore, the photodetector of the present disclosure may use holes as signal charges.

[0126] Furthermore, in the photodetector device of the present disclosure, the potentials of the anode and cathode are not limited as long as avalanche multiplication occurs when a reverse bias is applied between them.

[0127] Furthermore, in the above-described embodiments, examples have been shown in which silicon is used as the semiconductor substrate 11, but the semiconductor substrate 11 may also be, for example, germanium (Ge) or a compound semiconductor of silicon (Si) and germanium (Ge) (for example, silicon germanium (SiGe)).

[0128] The effects described in the above embodiments are merely examples, and other effects may be achieved, or may further include other effects.

[0129] The present disclosure may also be configured as follows. According to the present technology configured as follows, it is possible to prevent light from leaking into adjacent pixels and suppress crosstalk. (1) A photodetector comprising: a first semiconductor substrate having opposing first and second surfaces, a plurality of pixels arranged in an array in an in-plane direction, each of the plurality of pixels being provided with a single-photon avalanche diode that multiplies carriers by a high electric field region; a second semiconductor substrate stacked on the first surface side of the first semiconductor substrate, having a third surface facing the first surface of the first semiconductor substrate and a fourth surface opposite the third surface, and having one or more transistors; and a light-shielding structure extending in the stacking direction at least on the fourth surface side of the second semiconductor substrate and provided so as to surround at least each of the plurality of pixels. (2) The photodetector according to (1), wherein the light-shielding structure is continuously formed so as to surround each of the plurality of pixels. (3) The photodetector according to (1) or (2), wherein the light-shielding structure is formed intermittently so as to surround each of the plurality of pixels. (4) The photodetector according to (3), wherein gaps in the intermittently formed light-shielding structure are shorter than the wavelength at which photoelectric conversion is performed in the single-photon avalanche diode. (5) The photodetector according to any one of (1) to (4), wherein the first semiconductor substrate further has pixel separation sections provided between the plurality of pixels, extending between the first surface and the second surface, and optically separating the plurality of adjacent pixels, and the light-shielding structure is provided at least on or near the pixel separation sections in a planar view. (6) The photodetector according to any one of (1) to (5), wherein the light-shielding structure includes one or more through-wirings that penetrate the second semiconductor substrate. (7) The photodetector according to (6), wherein an end of the one or more through-holes on the first semiconductor substrate side is connected to the first semiconductor substrate. (8) The photodetector according to (6) or (7), wherein the one or more through-holes have a gap between the end on the first semiconductor substrate side and the first semiconductor substrate.(9) The photodetector according to any one of (6) to (8), wherein the one or more through-holes are arranged symmetrically with respect to a first direction and a second direction orthogonal to the first direction in a plan view. (10) The photodetector according to any one of (6) to (9), wherein the one or more through-holes are arranged continuously or intermittently so as to surround each of the plurality of pixels. (11) The photodetector according to any one of (6) to (10), wherein the first semiconductor substrate further has a pixel separation section that is arranged between the plurality of pixels and extends between the first surface and the second surface to optically separate the plurality of adjacent pixels, and the one or more through-holes are arranged at least on or near the pixel separation section in a plan view. (12) The photodetector according to any one of (6) to (11), wherein the second semiconductor substrate further has a first isolation portion that penetrates between the third surface and the fourth surface and separates the second semiconductor substrate into a plurality of portions, and the one or more through-hole wirings penetrate the first isolation portion. (13) The photodetector according to any one of (1) to (12), wherein the light-shielding structure includes one or more connection wirings that are provided on the fourth surface side of the second semiconductor substrate and extend in the stacking direction. (14) The photodetector according to (13), wherein end portions of the one or more connection wirings on the second semiconductor substrate side are connected to at least one of active regions and gates of the one or more transistors that are provided on the fourth surface of the second semiconductor substrate. (15) The photodetector according to (13) or (14), wherein the second semiconductor substrate further has a second isolation portion that isolates the plurality of adjacent transistors provided on the fourth surface, and ends of the one or more connection wirings on the second semiconductor substrate side are connected to the second isolation portion. (16) The photodetector according to any one of (13) to (15), further comprising an etching stopper layer between the second semiconductor substrate and ends of the one or more connection wirings on the second semiconductor substrate side.(17) The photodetector according to any one of (14) to (16), wherein a metal wiring extending in the in-plane direction is connected to an end of the one or more connection wirings on a side opposite to the second semiconductor substrate side. (18) The photodetector according to any one of (1) to (17), wherein the first semiconductor substrate further has a pixel separating portion provided between the plurality of pixels, extending between the first surface and the second surface, and optically separating the plurality of adjacent pixels, the pixel separating portion further penetrating the second semiconductor substrate and also serving as the light-shielding structure. (19) A distance measuring device comprising an optical system, a photodetector, and a signal processing circuit that calculates a distance to a measurement object from an output signal of the photodetector, wherein the photodetector comprises: a first semiconductor substrate having opposing first and second surfaces, on which a plurality of pixels are arranged in an array in an in-plane direction, and a single-photon avalanche diode that multiplies carriers by a high electric field region, provided in each of the plurality of pixels; a second semiconductor substrate stacked on the first surface side of the first semiconductor substrate, having a third surface facing the first surface of the first semiconductor substrate and a fourth surface opposite the third surface, and on which one or more transistors are provided; and a light-shielding structure that extends in the stacking direction at least on the fourth surface side of the second semiconductor substrate and is provided so as to surround at least each of the plurality of pixels.

Claims

1. A photodetector comprising: a first semiconductor substrate having opposing first and second surfaces, with a plurality of pixels arranged in an array in an in-plane direction, each of the plurality of pixels being provided with a single-photon avalanche diode that multiplies carriers by a high electric field region; a second semiconductor substrate stacked on the first surface side of the first semiconductor substrate, with a third surface facing the first surface of the first semiconductor substrate and a fourth surface opposite the third surface, and with one or more transistors provided; and a light-shielding structure extending in the stacking direction at least on the fourth surface side of the second semiconductor substrate, and provided so as to surround at least each of the plurality of pixels.

2. The photodetector according to claim 1, wherein the light-shielding structure is formed continuously so as to surround each of the plurality of pixels.

3. The photodetector according to claim 1, wherein the light-shielding structure is formed intermittently so as to surround each of the plurality of pixels.

4. The photodetector device according to claim 3, wherein the gaps in the intermittently formed light-shielding structure are less than the wavelength of light that is photoelectrically converted in the single-photon avalanche diode.

5. The photodetector device according to claim 1, wherein the first semiconductor substrate further has pixel separation sections that are provided between the plurality of pixels and extend between the first surface and the second surface, optically separating the plurality of adjacent pixels, and the light-shielding structure is provided at least on or in the vicinity of the pixel separation sections in a plan view.

6. The photodetector device according to claim 1, wherein the light-shielding structure includes one or more through-wirings that penetrate the second semiconductor substrate.

7. The photodetector according to claim 6, wherein an end of said one or more through-wirings on said first semiconductor substrate side is connected to said first semiconductor substrate.

8. The photodetector according to claim 6, wherein the one or more through-wires have a gap between an end thereof on the first semiconductor substrate side and the first semiconductor substrate.

9. The photodetector according to claim 6, wherein the one or more through-wires are arranged symmetrically with respect to a first direction and a second direction perpendicular to the first direction in a plan view.

10. The photodetector device according to claim 6, wherein the one or more through-wirings are provided continuously or intermittently so as to surround each of the plurality of pixels.

11. The photodetector device described in claim 6, wherein the first semiconductor substrate further has pixel separation sections that are provided between the plurality of pixels and extend between the first surface and the second surface, optically separating the plurality of adjacent pixels, and the one or more through wirings are provided at least on or in the vicinity of the pixel separation sections in a planar view.

12. The photodetector device described in claim 6, wherein the second semiconductor substrate further has a first separation portion that penetrates between the third surface and the fourth surface and separates the second semiconductor substrate into multiple portions, and the one or more through-wirings penetrate the first separation portion.

13. The photodetector according to claim 1, wherein the light-shielding structure includes one or more connection wirings provided on the fourth surface side of the second semiconductor substrate and extending in the stacking direction.

14. The photodetector device described in claim 13, wherein the end of the one or more connection wirings on the second semiconductor substrate side is connected to at least one of the active region and gate of the one or more transistors provided on the fourth surface of the second semiconductor substrate.

15. The photodetector device described in claim 13, wherein the second semiconductor substrate further has a second isolation portion that isolates adjacent ones of the plurality of transistors provided on the fourth surface, and the ends of the one or more connection wirings on the second semiconductor substrate side are connected to the second isolation portion.

16. The photodetector according to claim 13, further comprising an etching stopper layer between the second semiconductor substrate and an end of the one or more connection wirings on the second semiconductor substrate side.

17. The photodetector according to claim 14, wherein a metal wiring extending in the in-plane direction is connected to an end of the one or more connection wirings opposite to the second semiconductor substrate side.

18. The photodetector device of claim 1, wherein the first semiconductor substrate further has pixel separation sections that are provided between the plurality of pixels and extend between the first surface and the second surface, optically separating the plurality of adjacent pixels, and the pixel separation sections further penetrate the second semiconductor substrate and also serve as the light-shielding structure.

19. A distance measuring device comprising an optical system, a photodetector, and a signal processing circuit that calculates the distance to an object to be measured from the output signal of the photodetector, wherein the photodetector comprises: a first semiconductor substrate having opposing first and second surfaces, with a plurality of pixels arranged in an array in the in-plane direction, and each of the plurality of pixels being provided with a single-photon avalanche diode that multiplies carriers in a high electric field region; a second semiconductor substrate stacked on the first surface side of the first semiconductor substrate, with a third surface facing the first surface of the first semiconductor substrate and a fourth surface opposite the third surface, and with one or more transistors provided; and a light-shielding structure extending in the stacking direction at least on the fourth surface side of the second semiconductor substrate, and provided so as to surround at least each of the plurality of pixels.

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