JP2022089651A - Light detection device and distance measurement device - Google Patents

Abstract

To provide a light detection device and a distance measurement device, capable of reducing generation of a dark current.SOLUTION: A light detection device 1 includes: a semiconductor substrate 21 that has a first surface 11S1 and a second surface 11S2 that face each other and a pixel array unit in which a plurality of pixels P are arranged in an array; light reception units 13 that correspond to each pixel P, are embedded in the first surface 11S1 side of the semiconductor substrate 21, generate a carrier corresponding to a received light amount through photoelectric conversion, and comprise a semiconductor having a narrower bandgap than the semiconductor substrate 21; and multiplication units 14 that are disposed in a vicinity of surfaces of the light reception units 13 roughly flush with the first surface 11S1 of the semiconductor substrate 21, avalanche-multiply the carriers generated by the light reception units 13, and comprise a semiconductor having a narrower bandgap than the semiconductor substrate 21.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to, for example, a photodetector using an avalanche photodiode and a ranging device including the same.

For example, Patent Document 1 discloses a photodetector in which an avalanche photodiode is provided for each pixel and a semiconductor region surrounding the avalanche photodiode is provided to separate adjacent pixels.

International Publication No. 2018/07453

By the way, in the photodetector constituting the distance measuring device, it is required to reduce the generation of dark current.

It is desirable to provide a photodetector and a ranging device capable of reducing the generation of dark current.

The photomultiplier tube of one embodiment of the present disclosure has a semiconductor substrate having a first surface and a second surface facing each other, and having a pixel array portion in which a plurality of pixels are arranged in an array, and a semiconductor for each pixel. A light receiving portion made of a semiconductor that is embedded and formed on the first surface side of the substrate and has a bandgap narrower than that of the semiconductor substrate while generating carriers according to the amount of received light by photoelectric conversion, and abbreviated as the first surface of the semiconductor substrate. It is provided near the surface of the light receiving portion forming the same surface, and is provided with a photomultiplier tube made of a semiconductor having a bandgap narrower than that of a semiconductor substrate, as well as multiplying the carriers generated in the light receiving section by an avalanche.

The ranging device of one embodiment of the present disclosure includes an optical system, a photodetector, and a signal processing circuit that calculates the distance from the output signal of the photodetector to the object to be measured, and includes photodetection. As the device, the photodetector according to the embodiment of the present disclosure is provided.

In the photodetector of one embodiment and the distance measuring device of one embodiment of the present disclosure, a light receiving portion formed by being embedded in the first surface side of a semiconductor substrate having a first surface and a second surface facing each other, A photomultiplier tube provided near the surface of the photomultiplier tube that forms substantially the same surface as the first surface of the semiconductor substrate is formed by using a semiconductor having a narrower bandgap than the semiconductor substrate to form a photomultiplier tube. Alleviate lattice mismatch at the interface with the multiplying part.

It is sectional drawing which shows an example of the structure of the photodetector which concerns on embodiment of this disclosure. It is a plan schematic diagram which shows an example of the structure of the pixel array part of the photodetector shown in FIG. It is a block diagram which shows an example of the schematic structure of the photodetector shown in FIG. It is an example of the equivalent circuit diagram of the unit pixel of the photodetector shown in FIG. It is a plane schematic diagram which shows the other example of the plane composition of the unit pixel of the photodetector shown in FIG. It is a plane schematic diagram which shows the other example of the plane composition of the unit pixel of the photodetector shown in FIG. It is a plane schematic diagram which shows the other example of the plane composition of the unit pixel of the photodetector shown in FIG. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 1 of this disclosure. It is sectional drawing which shows the other example of the structure of the photodetector which concerns on the modification 1 of this disclosure. It is sectional drawing which shows the other example of the structure of the photodetector which concerns on the modification 1 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 2 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 3 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 4 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 5 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 6 of this disclosure. It is sectional drawing which shows the other example of the structure of the photodetector which concerns on the modification 6 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 7 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 8 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 9 of this disclosure. It is sectional drawing which shows an example of the structure of the photodetector which concerns on the modification 10 of this disclosure. It is sectional drawing which shows the other example of the structure of the photodetector which concerns on the modification 10 of this disclosure. FIG. 3 is a functional block diagram showing an example of an electronic device using the photodetector shown in FIG. 1 and the like. It is a block diagram which shows an example of the schematic structure of a vehicle control system. It is explanatory drawing which shows an example of the installation position of the vehicle exterior information detection unit and the image pickup unit.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description is a specific example of the present disclosure, and the present disclosure is not limited to the following aspects. Further, the present disclosure is not limited to the arrangement, dimensions, dimensional ratio, etc. of each component shown in each figure. The order of explanation is as follows.
1. 1. Embodiment (photodetector in which the light receiving portion and the multiplying portion are formed of a material having a narrower bandgap than the Si substrate)
1-1. Configuration of photodetector 1-2. Manufacturing method of photodetector 1-3. Action / effect 2. Modification example 2-1. Modification 1 (Example in which an n-type diffusion region is provided on the outer edge of the light receiving portion)
2-2. Modification 2 (an example in which a guard ring is provided around the multiplying part)
2-3. Modification 3 (Example in which contact electrodes are provided on the light receiving portion and the multiplying portion, respectively)
2-4. Modification 4 (Example in which a photomultiplier part is provided on the light receiving part)
2-5. Deformation example 5 (Example in which the side surface of the multiplying part is an inclined surface)
2-6. Modification 6 (example in which the multiplying part is made smaller)
2-7. Modification 7 (Example in which a buffer layer is provided between the semiconductor substrate and the light receiving portion)
2-8. Modification 8 (Example in which a light reflecting layer is provided at a position facing the light receiving element of the multilayer wiring layer)
2-9. Modification 9 (Example in which a concave-convex structure is provided on the light incident surface of a semiconductor substrate)
2-10. Modification 10 (Other examples of the configuration of the pixel separation unit)
3. 3. Application example 4. Application example

<1. Embodiment>
FIG. 1 schematically shows an example of a cross-sectional configuration of a photodetector (photodetector 1) according to an embodiment of the present disclosure. FIG. 2 schematically shows an example of the planar configuration of the pixel array unit 100A of the photodetector 1 shown in FIG. FIG. 3 is a block diagram showing a schematic configuration of the photodetector 1 shown in FIG. 1, and FIG. 4 shows an example of an equivalent circuit of a unit pixel P of the photodetector 1 shown in FIG. Is. The photodetector 1 is applied to, for example, a distance image sensor (distance image device 1000 described later, see FIG. 20) or an image sensor that measures a distance by a ToF (Time-of-Flight) method.

(1-1. Configuration of photodetector)
The photodetector 1 has, for example, a pixel array unit 100A in which a plurality of unit pixels P are arranged in an array in the row direction and the column direction. As shown in FIG. 3, the photodetector 1 has a bias voltage application unit 110 together with the pixel array unit 100A. The bias voltage application unit 110 applies a bias voltage to each unit pixel P of the pixel array unit 100A. In this embodiment, a case where holes are read out as signal charges will be described.

As shown in FIG. 4, the unit pixel P includes, for example, a light receiving element 12, an inverter 120, an N-type MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) 130, 140, a P-type MOSFET 150, and a buffer circuit. It has 160 and.

The light receiving element 12 converts the incident light into an electric signal by photoelectric conversion and outputs the signal. Incidentally, the light receiving element 12 converts the incident light (photons) into an electric signal by photoelectric conversion, and outputs a pulse corresponding to the incident of the photons. The light receiving element 12 is, for example, a SPAD element, and in the SPAD element, for example, when a large positive voltage that causes avalanche multiplication is applied to the cathode, electrons generated in response to the incident of one photomultiplier cause avalanche multiplication. It has the characteristic that a large current flows. The light receiving element 12 is connected to, for example, an N-type MOSFET 130 whose cathode is connected to a power source of a voltage Vop corresponding to the breakdown voltage of the light receiving element 12 and whose anode is a current source.

The source of the N-type MOSFET 130 is connected to the ground potential GND. Here, the voltage Vop is a voltage obtained by adding the excess bias voltage Ve to the voltage Vbd, which is the breakdown voltage of the light receiving element 12. A reference voltage Vref is input to the gate of the N-type MOSFET 130. The N-type MOSFET 130 is a current source that outputs a current corresponding to the ground potential GND and the reference voltage Vref from the drain.

The anode of the light receiving element 12 is connected to the drain of the N-type MOSFET 130, and the voltage Van taken out from the connection point is input to the inverter 120. The inverter 120 makes a determination, for example, with respect to the input voltage Van, and outputs a signal Vinv that is inverted each time the voltage Van exceeds the threshold voltage Vth in the positive direction or the negative direction. The signal Vinv output from the inverter 120 is output as signal Vpls via, for example, the buffer circuit 160.

At the connection point where the anode of the light receiving element 12 and the drain of the N-type MOSFET 130 are connected, the drain of the N-type MOSFET 140 and the drain of the P-type MOSFET 150 are further connected. In the P-type MOSFET 150, the source is connected to the power supply voltage VDD corresponding to the excess bias voltage Ve, and the signal STBY is input to the gate. When the signal STBY is in the low state, the source and drain of the P-type MOSFET 150 are turned on, and the voltage Van of the anode of the light receiving element 12 is forcibly set to the voltage VDD. As a result, the voltage VCTH _-AN between the cathode and the anode of the light receiving element 12 becomes the voltage Vbd.

The source of the N-type MOSFET 140 is connected to the ground potential GND. The signal Vinv output from the inverter 120 is input to the gate of the N-type MOSFET 140 as a control signal Vctrl. In the N-type MOSFET 140, the signal Vinv, that is, the control signal Vctrl is turned on in the high state, and the anode of the light receiving element 12 is connected to the ground potential GND.

In the photodetector 1, for example, the logic substrate 20 is laminated on the front surface side of the sensor substrate 10 (for example, the front surface (first surface 11S1) side of the semiconductor substrate 11 constituting the sensor substrate 10), and the back surface side of the sensor substrate 10 is formed. (For example, it is a so-called back-illuminated photodetector that receives light from the back surface (second surface 11S2) of the semiconductor substrate 11 constituting the sensor substrate 10). In the photodetector 1 of the present embodiment, the light receiving portion 13 constituting the light receiving element 12 is embedded and formed on the first surface 11S1 side of the semiconductor substrate 11, and the light receiving portion 13 is formed in the vicinity of the surface 13S1 of the light receiving portion 13, specifically, the light receiving portion. On the surface 13S1 inside the 13, a multiplying portion 14 constituting the light receiving element 12 is formed together with the light receiving portion 13, and each is formed by using a semiconductor having a narrower bandgap than the semiconductor substrate 11.

The sensor substrate 10 has, for example, a semiconductor substrate 11 made of a silicon substrate and a multilayer wiring layer 18. The semiconductor substrate 11 has a first surface 11S1 and a second surface 11S2 facing each other, and a light receiving element 12 is embedded in the first surface 11S1 for each unit pixel P.

As described above, the photomultiplier tube 12 has a multiplying region (avalanche multiplying region) in which carriers are multiplied by an avalanche in a high electric field region. For example, a large positive voltage is applied to the cathode to multiply the avalanche. It is a SPAD element that can form a region (poor layer) and multiply the electrons generated by the incident of one photomultiplier avalanche.

The light receiving element 12 has, for example, a light receiving unit 13 and a multiplying unit 14. The light receiving portion 13 and the multiplying portion 14 are each formed of a semiconductor having a narrower bandgap than the semiconductor substrate 11 as described above. Specifically, the light receiving portion 13 and the multiplying portion 14 are formed by using a germanium (Ge) or a compound semiconductor of silicon (Si) and germanium (Ge) (for example, silicon germanium (SiGe)).

The light receiving unit 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. The light receiving portion 13 is formed by being embedded in, for example, the first surface 11S1 side of the semiconductor substrate 11, and the surface 13S1 thereof forms substantially the same surface as, for example, the first surface 11S1 of the semiconductor substrate 11. The light receiving unit 13 is composed of, for example, an n-type semiconductor region (n) 131 in which the impurity concentration is controlled to be n-type. The carriers (electrons) generated in the light receiving unit 13 are transferred to the multiplying unit 14 by the potential gradient.

The multiplying section 14 multiplies the carriers (electrons) generated in the light receiving section 13 by an avalanche. The multiplying portion 14 is composed of, for example, a p-type semiconductor region (p ⁺ ) 141 having an impurity concentration controlled to be p-type, which is provided in the vicinity of the surface 13S1 of the light receiving portion 13.

The surface 13S1 of the light receiving unit 13 is further provided with an n-type contact electrode 15 that is electrically connected to the cathode. The n-type contact electrode 15 is composed of, for example, an n-type semiconductor region (n ⁺⁺ ) 151 having a higher impurity concentration than the n-type semiconductor region 131. It is continuously formed around 14. A p-type contact electrode 16 electrically connected to the anode is provided on the surface 14S1 of the multiplying portion 14. The p-type contact electrode 16 is composed of, for example, a p-type semiconductor region (p ⁺⁺ ) 161 having a higher impurity concentration than the p-type semiconductor region 141, and is formed, for example, substantially in the center of the multiplying portion 14 in a plan view. Has been done.

In the light receiving element 12, the avalanche multiplying region 12X is formed at the junction between the n-type semiconductor region 131 constituting the light receiving portion 13 and the p-type semiconductor region 141 constituting the multiplying portion 14. The avalanche multiplication region 12X is a high electric field region (depletion layer) formed at the boundary surface between the n-type semiconductor region 131 and the p-type semiconductor region 141 by a large positive voltage applied to the cathode. In the avalanche multiplying region 12X, the electrons (e ⁻ ) generated by one photon incident on the light receiving element 12 are multiplied.

In FIG. 2, a photomultiplier tube 14 and a p-type contact electrode 16 having a substantially rectangular shape and a frame shape having a substantially rectangular outer diameter are similarly formed inside the light receiving portion 13 having a substantially rectangular planar shape. Although the example in which the n-type contact electrode 15 is provided around the multiplying portion 14, the shapes of the multiplying portion 14, the n-type contact electrode 15 and the p-type contact electrode 16 are not limited to this. For example, the multiplying portion 14 and the p-type contact electrode 16 may have a polygonal shape other than a rectangle as shown in FIG. 5A. In particular, when the pixel size is small, the multiplying portion 14 and the p-type contact electrode 16 should have a circular shape as shown in FIG. 5B from the viewpoint of lateral edge electric field relaxation (for example, in the XY plane direction). Is preferable. Further, when the pixel size is small, as shown in FIG. 5C, the n-type contact electrodes 15 may be provided intermittently at the four corners of the light receiving portion 13. This reduces unintended breakdowns in areas other than the multiplying section 14.

The semiconductor substrate 11 is further provided with a pixel separation unit 17. The pixel separation unit 17 electrically and / or optically separates adjacent unit pixels P, and is provided, for example, in a pixel array unit 100A in a grid pattern. The pixel separation unit 17 includes, for example, a light-shielding film 17A extending between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11, and an insulating film 17B provided between the light-shielding film 17A and the semiconductor substrate 11. It is composed of. The light-shielding film 17A is formed, for example, by using a conductive material having a light-shielding property. Examples of such a material include tungsten (W), silver (Ag), copper (Cu), aluminum (Al), an alloy of Al and copper (Cu), and the like. The insulating film 17B is formed by using, for example, a silicon oxide (SiO _x ) film or the like.

The multilayer wiring layer 18 is provided on the first surface 11S1 opposite to the light incident surface (second surface 11S2) of the semiconductor substrate 11. In the multilayer wiring layer 18, wiring layers 181, 182 composed of one or a plurality of wirings are laminated with an interlayer insulating layer 183 in between. The wiring layers 181, 182 are for supplying a voltage applied to the semiconductor substrate 11 and the light receiving element 12, and for taking out the carriers generated in the light receiving element 12, for example. The wiring layer 181 and the wiring layer 182 are electrically connected via the via V2, and a part of the wiring of the wiring layer 181 is further electrically connected to the n-type contact electrode 15 and the p-type contact electrode 16 via the via V1. Is connected. A plurality of pad electrodes 184 are embedded in the surface of the interlayer insulating layer 183 opposite to the semiconductor substrate 11 side (surface 18S1 of the multilayer wiring layer 18). The plurality of pad electrodes 184 are electrically connected to a part of the wiring of the wiring layer 182 via the via V3. Although FIG. 1 shows an example in which two wiring layers 181, 182 are formed in the multilayer wiring layer 18, the total number of wiring layers in the multilayer wiring layer 18 is not limited and may be a single layer. , Or three or more wiring layers may be formed.

The interlayer insulating layer 183 is, for example, a single-layer film made of one of silicon oxide (SiO _x ), TEOS, silicon nitride (SiN _x ), silicon oxynitride (SiO _x N _y ), or any of these. It is composed of a laminated film composed of two or more types.

The wiring layers 181, 182 are formed of, for example, aluminum (Al), copper (Cu), tungsten (W), or the like.

The pad electrode 184 is exposed on the joint surface with the logic substrate 20 (the surface 18S1 of the multilayer wiring layer 18), and is used for connection with the logic substrate 20, for example. The pad electrode 184 is formed by using, for example, copper (Cu).

The logic substrate 20 has, for example, a semiconductor substrate 21 made of a silicon substrate and a multilayer wiring layer 22. The logic board 20 is provided with, for example, the bias voltage application unit 110 described above, an inverter 120 provided for each unit pixel P, an N-type MOS FET 130, 140, a P-type MOSFET 150, a buffer circuit 160, and the like.

The multilayer wiring layer 22 includes a gate wiring 221 of a transistor constituting an inverter 120, an N-type MOS FET 130, 140, a P-type MOSFET 150, and a buffer circuit 160, and a wiring layer 222, 223, 224, 225 including one or a plurality of wirings. And are laminated in order from the semiconductor substrate 21 side with the interlayer insulating layer 226 in between. A plurality of pad electrodes 227 are embedded in the surface of the interlayer insulating layer 226 opposite to the semiconductor substrate 21 side (surface 22S1 of the multilayer wiring layer 22). The plurality of pad electrodes 227 are electrically connected to a part of the wiring of the wiring layer 225 via the via V4.

Similar to the interlayer insulating layer 183, the interlayer insulating layer 117 is simply composed of, for example, one of silicon oxide (SiO _x ), TEOS, silicon nitride (SiN _x ), silicon oxynitride (SiO _x N _y ), and the like. It is composed of a layered film or a laminated film composed of two or more of these.

The gate wiring 221 and the wiring layer 222, 223, 224, 225 are formed by using, for example, aluminum (Al), copper (Cu), tungsten (W), or the like, similarly to the wiring layers 181, 182.

The pad electrode 227 is exposed on the joint surface with the sensor substrate 10 (surface 22S1 of the multilayer wiring layer 22), and is used for connection with the sensor substrate 10, for example. Like the pad electrode 184, the pad electrode 227 is formed by using, for example, copper (Cu).

In the photodetector 1, for example, a CuCu bond is formed between the pad electrode 184 and the pad electrode 227. As a result, the cathode of the light receiving element 12 is electrically connected to the power supply of the voltage Vop corresponding to the breakdown voltage of the light receiving element 12 provided on the logic board 20 side, and the anode of the light receiving element 12 is on the logic board 20 side. It is electrically connected to the N-type MOSFET 130 provided as a current source.

On the light incident surface (second surface 11S2) side of the semiconductor substrate 11, for example, a microlens 31 is provided for each unit pixel P via a passivation film (not shown). Further, a light-shielding portion 32 is provided between the adjacent microlenses 31.

The microlens 31 is for condensing light incident from above on the light receiving element 12, and is formed by using, for example, silicon oxide (SiO _x ) or the like.

The light-shielding unit 32 suppresses crosstalk of obliquely incident light between adjacent pixels. The light-shielding unit 32 is provided, for example, between adjacent unit pixels P in the pixel array unit 100A, and is provided in a grid pattern in the pixel array unit 100A, for example, like the pixel separation unit 17. Like the light-shielding film 17A, the light-shielding portion 32 is formed by using a conductive material having a light-shielding property. Specifically, it is formed by using tungsten (W), silver (Ag), copper (Cu), aluminum (Al), an alloy of Al and copper (Cu), or the like.

(1-2. Manufacturing method of photodetector)
The photodetector 1 can be manufactured, for example, as follows. First, an opening having a predetermined depth is formed for each unit pixel P on the first surface 11S1 of the semiconductor substrate 11 made of a silicon substrate. At this time, for example, by using two or more semiconductor substrates made of different materials such as an SOI substrate as the silicon substrate, the SiO ₂ layer in the layer serves as a stopper and the depth of the opening can be controlled. Subsequently, a semiconductor layer made of, for example, germanium (Ge) or silicon germanium (SiGe) is formed in the opening by an epitaxial crystal growth method such as the Metal Organic Chemical Vapor Deposition (MOCVD) method. .. Next, for example, after flattening the surface of the semiconductor layer by CMP (Chemical Mechanical Polishing), the p-type or n-type impurity concentration is controlled in the semiconductor layer by ion injection, and the n-type semiconductor region 131 (light receiving unit 13) is controlled. ), 151 (n-type contact electrode) and p-type semiconductor region 141 (magnification portion 14), 161 (p-type contact electrode 16) are formed.

Subsequently, an oxide film such as silicon oxide (SiO _x ) or a nitride film such as (SiN _x ) is patterned on the first surface 11S1 of the semiconductor substrate 11 as a hard mask, and then the semiconductor substrate 11 is etched, for example. Form a through hole to penetrate. Next, the insulating film 17B and the light-shielding film 17A are sequentially formed in the through holes by, for example, a CVD (Chemical Vapor Deposition) method, a PVD (Physical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, or a thin-film deposition method. Subsequently, for example, the light-shielding film 17A and the insulating film 17B formed on the first surface 11S1 of the semiconductor substrate 11 are removed by CMP using a hard mask as a stopper, and then the multilayer wiring layer is placed on the first surface 11S1 of the semiconductor substrate 11. 18 is formed. After that, the separately created logic board 20 is pasted together. At this time, the plurality of pad electrodes 184 exposed on the joint surface (surface 18S1) of the multilayer wiring layer 18 and the plurality of pad portions 217 exposed on the joint surface (surface 22S) of the multilayer wiring layer 22 on the logic substrate 20 side are formed. CuCu is joined. Subsequently, the second surface 11S2 of the semiconductor substrate 11 is polished by, for example, CMP, and then the passivation film, the light-shielding portion 32, and the microlens 31 are formed in this order. This completes the photodetector 1 shown in FIG.

(1-3. Action / effect)
In the light detection device 1 of the present embodiment, the surface of the light receiving portion 13 embedded in the first surface 11S1 side of the semiconductor substrate 11 and the surface of the light receiving portion 13 forming substantially the same surface as the first surface 11S1 of the semiconductor substrate 11. The multiplying portion 14 provided in 13S1 is formed by using a semiconductor having a narrower band gap than the semiconductor substrate 11 (for example, a germanium (Ge) or a compound semiconductor of silicon (Si) and germanium (Ge)). , The lattice mismatch at the interface between the light receiving portion 13 and the multiplying portion 14 was alleviated. This will be described below.

In recent years, as a photodetector, a distance image sensor that measures a distance by the ToF method has attracted attention. The distance image sensor includes a pixel array unit in which a plurality of pixels are arranged in a matrix, and the efficiency of the entire device is determined by the pixel dimensions and the pixel structure.

By the way, as a method of improving the altitude with respect to near infrared light in a photodetector having an avalanche photodiode element for each unit pixel P, it is conceivable to increase the thickness of the semiconductor layer on which the avalanche region is formed. However, if the semiconductor layer is made thicker, the timing jitter characteristics may deteriorate.

As another method for improving the altitude with respect to near-infrared light in the above-mentioned photodetector, it is conceivable to form a light receiving portion using a semiconductor having a narrow bandgap. For example, the light receiving portion is formed by using a low bandgap semiconductor, for example, germanium (Ge), and an avalanche multiplying region is formed at the junction with the silicon substrate. However, when an avalanche multiplying region is formed in the heterojunction, there is a risk that dark current will increase at the junction interface due to lattice mismatch.

On the other hand, in the present embodiment, the light receiving portion 13 and the multiplying portion 14 embedded and formed on the first surface 11S1 side of the semiconductor substrate 11 are provided with a semiconductor having a narrower bandgap than the semiconductor substrate 11 (for example, germanium (for example, germanium). It was formed using Ge) or a compound semiconductor of silicon (Si) and germanium (Ge). As a result, the lattice mismatch at the interface between the light receiving portion 13 and the multiplying portion 14 is alleviated.

As described above, in the photodetector 1 of the present embodiment, both the light receiving unit 13 and the multiplying unit 14 have a narrower bandgap than the semiconductor substrate 11, for example, germanium (Ge) or silicon (Si) and germanium (Ge). ), Since it is formed by using the compound semiconductor of), it is possible to reduce the generation of dark current at the interface between the light receiving portion 13 and the multiplying portion 14.

Further, in the light detection device 1 of the present embodiment, the light receiving element 12 including the light receiving unit 13 and the multiplying unit 14 is composed of germanium (Ge), silicon (Si), and germanium (Ge), which are low band gap semiconductors. Since it is formed using a compound semiconductor (for example, silicon germanium (SiGe)), the thickness of the light receiving portion 13 is improved by the amount that the sensitivity to near infrared light is improved as compared with the case where silicon (Si) is used. Can be reduced. Therefore, it is possible to improve the timing jitter characteristic.

Next, modifications 1 to 10 of the present disclosure, as well as application examples and application examples will be described. Hereinafter, the same components as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

<2. Modification example>
(2-1. Modification 1)
FIG. 6 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1A) according to the first modification of the present disclosure. The photodetector 1A is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The photodetector 1A of the present modification is provided with an n-type semiconductor region (n ⁺ ) 132 having a higher impurity concentration than the n-type semiconductor region 131 in the vicinity of the semiconductor substrate 11 of the light receiving unit 13, according to the above embodiment. Is different. This n-type semiconductor region 132 corresponds to a specific example of the "third semiconductor region" of the present disclosure.

In the optical detection device 1A, the n-type semiconductor region 132 having a higher impurity concentration than the n-type semiconductor region 131 is located in the vicinity of the semiconductor substrate 11 of the light receiving unit 13, specifically, in the peripheral portion of the light receiving unit 13. It is provided. In this modification, the n-type contact electrode 15 connected to the cathode is formed in the n-type semiconductor region 132.

As a result, the cathode potential can be selectively applied to the vicinity of the semiconductor substrate 11, that is, the side surface portion of the light receiving portion 13 and the bottom surface portion opposite to the multiplying portion 14, and the peripheral portion of the light receiving portion 13 and the light receiving portion are received. A potential gradient is formed between the surface 13S1 of the portion 13 and the multiplying portion 14 formed substantially in the center in a plan view. Therefore, the carriers (electrons) generated in the light receiving unit 13 by the photoelectric conversion can be efficiently transferred to the multiplying unit 14. Therefore, in addition to the effect of the above embodiment, the timing jitter characteristic can be further improved.

In this modification, as shown in FIG. 6, the n-type semiconductor region 132 having a higher impurity concentration than the n-type semiconductor region 131 and having a uniform impurity concentration is placed in the vicinity of the semiconductor substrate 11 of the light receiving unit 13. Although the provided example is shown, an n-type semiconductor region having a different impurity concentration or a different impurity species may be formed in the vicinity of the semiconductor substrate 11 of the light receiving portion 13.

Specifically, for example, as shown in FIG. 7, an n-type semiconductor region (n ⁺ ) 132 having a higher impurity concentration than the n-type semiconductor region 131 is formed on the side surface portion of the light receiving unit 13, and the light receiving unit 13 is formed. An n-type semiconductor region (n ⁺⁺ ) 133 having a higher impurity concentration than the n-type semiconductor region 132 may be provided on the bottom surface. In this way, by providing the n-type semiconductor region 133 having a higher impurity concentration on the bottom surface of the light receiving unit 13, carriers (electrons) generated in the light receiving unit 13 by photoelectric conversion are more efficiently transferred to the multiplying unit 14. It becomes possible to do.

Further, in the n-type semiconductor region 131 surrounded by the n-type semiconductor region 132 or by the n-type semiconductor region 132 and the n-type semiconductor region 133, for example, as shown in FIG. 8, the second semiconductor substrate 11 An impurity concentration gradient may be formed in which the impurity concentration decreases continuously or stepwise from the surface 11S2 side toward the first surface 11S1. This also makes it possible to efficiently transfer the carriers generated in the light receiving unit 13 by the photoelectric conversion to the multiplying unit 14.

(2-2. Modification 2)
FIG. 9 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1B) according to the second modification of the present disclosure. The photodetector 1B is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. In the photodetector 1B of this modification, the p-type semiconductor region (p) 142 having a lower impurity concentration than the p-type semiconductor region 141 is provided around the p-type semiconductor region 141 constituting the multiplying portion 14 in a plan view. However, it is different from the above embodiment. This p-type semiconductor region 142 corresponds to a specific example of the "fourth semiconductor region" of the present disclosure.

The p-type semiconductor region 142 functions as a guard ring. By providing the p-type semiconductor region 142 around the p-type semiconductor region 141 constituting the multiplying portion 14, the edge electric field is relaxed. Further, the avalanche multiplying region 12X is selectively formed in the p-type semiconductor region 141 inside the p-type semiconductor region 142.

As described above, in this modification, since the guard ring structure is provided along the side surface of the multiplying portion 14, it is possible to reduce unintended breakdown in addition to the effect of the above-described embodiment. ..

(2-3. Modification 3)
FIG. 10 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1C) according to the third modification of the present disclosure. The photodetector 1C is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The photodetector 1C of this modification is different from the above embodiment in that the n-type contact electrode 15 and the p-type contact electrode 16 are provided on the light receiving portion 13 and the multiplying portion 14, respectively.

The n-type contact electrode 15 and the p-type contact electrode 16 of this modification are formed on the semiconductor layer constituting the light receiving portion 13 and the multiplying portion 14 as an epitaxial layer formed by, for example, an epitaxial crystal growth method. be.

As described above, in this modification, the n-type contact electrode 15 and the p-type contact electrode 16 made of, for example, an epitaxial layer are provided on the light receiving portion 13 and the multiplying portion 14, respectively. As a result, as in the above embodiment, the surface 13S1 of the light receiving portion 13 and the surface 14S1 of the multiplying portion 14, in other words, the n-type contact electrode 15 and the n-type contact electrode 15 in the semiconductor layer constituting the light receiving portion 13 and the multiplying portion 14. Compared with the case where the p-type contact electrode 16 is provided, the edge withstand voltage is improved. Therefore, in addition to the effects of the above-described embodiment, it is possible to reduce unintended breakdown.

(2-4. Modification 4)
FIG. 11 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1D) according to the modified example 4 of the present disclosure. The photodetector 1D is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The photodetector 1D of this modification is different from the above-described embodiment in that the photomultiplier tube 14 is provided on the light receiving section 13.

The multiplying portion 14 of this modification is, for example, formed as an epitaxial layer formed by the epitaxial crystal growth method on the surface 13S1 of the light receiving portion 13, that is, on the semiconductor layer constituting the light receiving portion 13. ..

As described above, in this modification, the multiplying portion 14 is provided on the light receiving portion 13. As a result, the n-type contact electrode 15 provided in the light receiving unit 13 and the multiplying unit 14 are compared with the case where the multiplying unit 14 is provided in the vicinity of the surface 13S1 in the light receiving unit 13 as in the above embodiment. Since the distance from the p-type contact electrode 16 provided in the above is large, the edge electric field is relaxed. Therefore, in addition to the effects of the above-described embodiment, it is possible to reduce unintended breakdown.

(2-5. Modification 5)
FIG. 12 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1E) according to the modified example 5 of the present disclosure. The photodetector 1E is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The side surface 14S3 of the multiplying portion 14 may be an inclined surface. Specifically, the side surface 14S3 of the multiplying portion 14 may be inclined so that the angle formed by the surface surface 14S1 and the side surface 14S3 is an acute angle.

(2-6. Modification 6)
FIG. 13 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1F) according to the modified example 6 of the present disclosure. The photodetector 1F is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The size of the avalanche multiplying region 12X formed at the junction between the n-type semiconductor region 131 constituting the multiplying portion 14 and the light receiving portion 13 and the p-type semiconductor region 141 constituting the multiplying portion 14 is limited. It's not a thing.

In the above embodiment, the light receiving portion 13 and the multiplying portion 14 are made of a low bandgap semiconductor germanium (Ge) or a compound semiconductor of silicon (Si) and germanium (Ge) (for example, silicon germanium (SiGe)). I tried to form it. Therefore, it is possible to reduce the tunnel current by reducing the volume of the photomultiplier tube 14 having a high electric field as in the photodetector 1F of this modification.

Further, as shown in FIG. 14, when the multiplying portion 14 is provided on the surface 13S1 of the light receiving portion 13 in combination with the above-mentioned modification 4, it is possible to reduce an unintended breakdown.

(2-7. Modification 7)
FIG. 15 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1G) according to the modified example 7 of the present disclosure. The photodetector 1G is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The photodetector 1G of the present modification is different from the above-described embodiment in that the buffer layer 19 is provided between the semiconductor substrate 11 and the light receiving unit 13.

The buffer layer 19 is for alleviating the lattice mismatch at the interface between the semiconductor substrate 11 and the light receiving unit 13. The buffer layer 19 is, for example, a lattice constant of a silicon substrate constituting the semiconductor substrate 11 and a compound semiconductor of germanium (Ge) or silicon (Si) and germanium (Ge) constituting the light receiving portion 13 (for example, silicon germanium (for example)). It can be formed by a semiconductor having a lattice constant between the lattice constant of SiGe)). Specifically, for example, the buffer layer 19 is formed of, for example, a silicon germanium (SiGe) layer in which the concentration ratio of a single or a plurality of silicon (Si) and germanium (Ge) is changed. This makes it possible to alleviate the lattice mismatch between silicon (Si) and germanium (Ge). The buffer layer 19 can be formed by, for example, an epitaxial crystal growth method.

As described above, in this modification, the buffer layer 19 made of a semiconductor having a lattice constant between the respective lattice constants is provided between the semiconductor substrate 11 and the light receiving portion 13, so that the semiconductor substrate 11 and the light receiving portion 13 are provided with the buffer layer 19. It is possible to reduce the generation of dark current at the interface with the unit 13.

(2-8. Modification 8)
FIG. 16 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1H) according to the modified example 8 of the present disclosure. The photodetector 1H is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. In the photodetector 1H of this modification, the wiring (for example, wiring 181A) of a plurality of wiring layers 181, 182 provided in the interlayer insulating layer 183 is oriented in the XY plane direction so as to face the light receiving element 12. It is different from the above-described embodiment in that it is formed in an extended manner. This wiring 181A corresponds to a specific example of the "light reflecting unit" of the present disclosure.

As described above, in this modification, the light reflecting unit is located at a position facing the light receiving element 12 by using a part of the wiring (for example, wiring 181A) of the plurality of wiring layers 181, 182 constituting the multilayer wiring layer 18. Was set up. As a result, the light that is not absorbed by the light receiving unit 13 and is transmitted through the multilayer wiring layer 18 is reflected by the wiring 181A and re-enters the light receiving unit 13. Therefore, in addition to the effects of the above-described embodiment, the sensitivity can be further improved.

(2-9. Modification 9)
FIG. 17 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1I) according to the modified example 9 of the present disclosure. The photodetector 1I is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. The photodetector 1I of this modification is different from the above-described embodiment in that the concave-convex structure is provided on the second surface 11S2 of the semiconductor substrate 11.

As described above, in this modification, since the concave-convex structure is provided on the second surface 11S2 of the semiconductor substrate 11 which is the light incident surface, the light incident on the light receiving unit 13 is diffusely reflected and the amount of light incident on the light receiving unit 13. Is homogenized in a two-dimensional plane. Therefore, in addition to the effects of the above-described embodiment, the sensitivity can be further improved.

(2-10. Modification 10)
FIG. 18 schematically shows an example of the cross-sectional configuration of the photodetector (photodetector 1J) according to the modified example 10 of the present disclosure. The photodetector 1J is applied to a distance image sensor (distance image device 1000), an image sensor, or the like that measures a distance by the ToF method, for example, as in the above embodiment. In the optical detection device 1J of this modification, the semiconductor substrate 11 is used as a support substrate (growth substrate), and germanium (Ge) or silicon (Si) or silicon (Si) or silicon (Si) is used on the entire surface of the first surface 11S1 of the semiconductor substrate 11 by, for example, an epitaxial crystal growth method. ) And germanium (Ge) to form a semiconductor layer 41 made of a compound semiconductor (for example, silicon germanium (SiGe)), and between adjacent unit pixels P, instead of the pixel separation unit 17 in the above embodiment, The point that the p-well 411 is provided is different from the above-described embodiment.

As described above, in this modification, a semiconductor layer 41 made of, for example, germanium (Ge) or silicon germanium (SiGe) is formed on the entire surface of the first surface 11S1 of the semiconductor substrate 11, and is located between adjacent unit pixels P. A p-well 411 was provided, and this was used as a separation unit for electrically separating adjacent unit pixels P. As a result, the area of the light receiving portion 13 can be expanded as compared with the case where the pixel separating portion 17 composed of the light shielding film 17A and the insulating film 17B is provided as in the above embodiment. Therefore, in addition to the effects of the above-described embodiment, it is possible to improve the sensitivity.

As shown in FIG. 19, the pixel separation unit 17 provided between the adjacent unit pixels P of the semiconductor substrate 11 may be omitted. As a result, the area of the light receiving unit 13 can be expanded and the sensitivity can be improved.

<3. Application example>
FIG. 20 shows an example of a schematic configuration of a distance imager 1000 as an electronic device provided with a photodetector (for example, a photodetector 1) according to the above-described embodiment and modifications 1 to 10. This distance imager 1000 corresponds to a specific example of the "distance measuring device" of the present disclosure.

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.

The range image device 1000 projects light from the light source device 1100 toward the irradiation target object 2000 and receives light (modulated light or pulsed light) reflected on the surface of the irradiation target object 2000 to reach the irradiation target object 2000. It is possible to acquire a distance image according to the distance of.

The optical system 1200 is configured to have one or a plurality of lenses, guides the image light (incident light) from the irradiation target 2000 to the light detection device 1, and receives the light receiving surface (sensor unit) of the light detection device 1. To form an image.

The image processing circuit 1300 performs image processing for constructing a distance image based on the distance signal supplied from the light detection device 1, and the distance image (image data) obtained by the image processing is supplied to the monitor 1400. It is displayed or supplied to the memory 1500 and stored (recorded).

In the distance imager 1000 configured in this way, by applying the above-mentioned light detection device (for example, the light detection device 1), the irradiation target object 2000 is based only on the light receiving signal from the highly stable unit pixel P. It is possible to calculate the distance to and generate a highly accurate distance image. That is, the distance imager 1000 can acquire a more accurate distance image.

<4. Application example>
(Example of application to mobile objects)
The technique according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure is any kind of movement such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a ship, a robot, a construction machine, and an agricultural machine (tractor). It may be realized as a device mounted on the body.

FIG. 21 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technique according to the present disclosure can be applied.

The vehicle control system 12000 includes a plurality of electronic control units connected via the communication network 12001. In the example shown in FIG. 21, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside information detection unit 12030, an in-vehicle information detection unit 12040, and an integrated control unit 12050. Further, as a functional configuration of the integrated control unit 12050, a microcomputer 12051, an audio image output unit 12052, and an in-vehicle network I / F (interface) 12053 are shown.

The drive system control unit 12010 controls the operation of the device related to the drive system of the vehicle according to various programs. For example, the drive system control unit 12010 has a driving force generator for generating a driving force of a vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, and a steering angle of the vehicle. It functions as a control device such as a steering mechanism for adjusting and a braking device for generating braking force of the vehicle.

The body system control unit 12020 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 12020 functions as a keyless entry system, a smart key system, a power window device, or a control device for various lamps such as headlamps, back lamps, brake lamps, turn signals or fog lamps. In this case, the body system control unit 12020 may be input with radio waves transmitted from a portable device that substitutes for the key or signals of various switches. The body system control unit 12020 receives inputs of these radio waves or signals and controls a vehicle door lock device, a power window device, a lamp, and the like.

The vehicle outside information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, the image pickup unit 12031 is connected to the vehicle outside information detection unit 12030. The vehicle outside information detection unit 12030 causes the image pickup unit 12031 to capture an image of the outside of the vehicle and receives the captured image. The out-of-vehicle information detection unit 12030 may perform object detection processing or distance detection processing such as a person, a vehicle, an obstacle, a sign, or a character on the road surface based on the received image.

The image pickup unit 12031 is an optical sensor that receives light and outputs an electric signal according to the amount of the light received. The image pickup unit 12031 can output an electric signal as an image or can output it as distance measurement information. Further, the light received by the image pickup unit 12031 may be visible light or invisible light such as infrared light.

The in-vehicle information detection unit 12040 detects information in the vehicle. For example, a driver state detection unit 12041 that detects a driver's state is connected to the vehicle interior information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that images the driver, and the in-vehicle information detection unit 12040 determines the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041. It may be calculated, or it may be determined whether or not the driver has fallen asleep.

The microcomputer 12051 calculates the control target value of the driving force generator, the steering mechanism, or the braking device based on the information inside and outside the vehicle acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040, and the drive system control unit. A control command can be output to 12010. For example, the microcomputer 12051 realizes ADAS (Advanced Driver Assistance System) functions including vehicle collision avoidance or impact mitigation, follow-up driving based on inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane deviation warning, and the like. It is possible to perform cooperative control for the purpose of.

Further, the microcomputer 12051 controls the driving force generating device, the steering mechanism, the braking device, and the like based on the information around the vehicle acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040. It is possible to perform coordinated control for the purpose of automatic driving that runs autonomously without depending on the operation.

Further, 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 vehicle outside information detection unit 12030. For example, the microcomputer 12051 controls the headlamps according to the position of the preceding vehicle or the oncoming vehicle detected by the outside information detection unit 12030, and performs cooperative control for the purpose of anti-glare such as switching the high beam to the low beam. It can be carried out.

The audio-image output unit 12052 transmits an output signal of at least one of audio and an image to an output device capable of visually or audibly notifying information to the passenger or the outside of the vehicle. In the example of FIG. 21, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices. The display unit 12062 may include, for example, at least one of an onboard display and a head-up display.

FIG. 22 is a diagram showing an example of the installation position of the image pickup unit 12031.

In FIG. 22, as the image pickup unit 12031, the image pickup unit 12101, 12102, 12103, 12104, 12105 is provided.

The image pickup units 12101, 12102, 12103, 12104, 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumpers, back doors, and the upper part of the windshield in the vehicle interior of the vehicle 12100. The image pickup unit 12101 provided on the front nose and the image pickup section 12105 provided on the upper part of the windshield in the vehicle interior mainly acquire an image in front of the vehicle 12100. The image pickup units 12102 and 12103 provided in the side mirror mainly acquire images of the side of the vehicle 12100. The image pickup unit 12104 provided in the rear bumper or the back door mainly acquires an image of the rear of the vehicle 12100. The image pickup unit 12105 provided on the upper part of the windshield in the vehicle interior is mainly used for detecting a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

Note that FIG. 22 shows an example of the photographing range of the imaging units 12101 to 12104. The imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, the imaging ranges 12112 and 12113 indicate the imaging range of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and the imaging range 12114 indicates the imaging range. The imaging range of the imaging unit 12104 provided on the rear bumper or the back door is shown. For example, by superimposing the image data captured by the imaging units 12101 to 12104, a bird's-eye view image of the vehicle 12100 can be obtained.

At least one of the image pickup units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image pickup units 12101 to 12104 may be a stereo camera including a plurality of image pickup elements, or may be an image pickup element having pixels for phase difference detection.

For example, the microcomputer 12051 has a distance to each three-dimensional object within the image pickup range 12111 to 12114 based on the distance information obtained from the image pickup unit 12101 to 12104, and a temporal change of this distance (relative speed with respect to the vehicle 12100). By obtaining can. Further, the microcomputer 12051 can set an inter-vehicle distance to be secured in advance in front of the preceding vehicle, and can perform automatic brake control (including follow-up stop control), automatic acceleration control (including follow-up start control), and the like. In this way, it is possible to perform coordinated control for the purpose of automatic driving or the like that autonomously travels without relying on the driver's operation.

For example, the microcomputer 12051 converts three-dimensional object data related to a three-dimensional object into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, electric poles, and other three-dimensional objects based on the distance information obtained from the image pickup units 12101 to 12104. It can be classified and extracted and used for automatic avoidance of obstacles. 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. Then, the microcomputer 12051 determines the collision risk indicating the risk of collision with each obstacle, and when the collision risk is equal to or higher than the set value and there is a possibility of collision, the microcomputer 12051 via the audio speaker 12061 or the display unit 12062. By outputting an alarm to the driver and performing forced deceleration and avoidance steering via the drive system control unit 12010, driving support for collision avoidance can be provided.

At least one of the image pickup 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 or not a pedestrian is present in the captured image of the imaging unit 12101 to 12104. Such recognition of a pedestrian is, for example, a procedure for extracting feature points in an image captured by an image pickup unit 12101 to 12104 as an infrared camera, and a pattern matching process for a series of feature points showing the outline of an object to determine whether or not the pedestrian is a pedestrian. It is done by the procedure to determine. When the microcomputer 12051 determines that a pedestrian is present in the captured image of the image pickup unit 12101 to 12104 and recognizes the pedestrian, the audio image output unit 12052 determines the square contour line for emphasizing the recognized pedestrian. The display unit 12062 is controlled so as to superimpose and display. Further, the audio image output unit 12052 may control the display unit 12062 so as to display an icon or the like indicating a pedestrian at a desired position.

Although the embodiments and modifications 1 to 10 and the application examples and application examples have been described above, the contents of the present disclosure are not limited to the above-described embodiments and the like, and various modifications are possible. For example, in the above-described embodiment and the like, an example in which holes are used as signal charges is shown, but electrons may be used as signal charges.

Further, in the above-described embodiment and the like, an example in which a negative potential is applied to the cathode is shown, but if a reverse bias is applied between the anode and the cathode, an avalanche multiplication occurs, respectively. The potential of is not limited.

Further, the effect described in the above-described embodiment or the like is an example, and may be another effect, or may further include another effect.

The present disclosure may have the following configuration. According to the present technology having the following configuration, the light receiving portion formed by being embedded in the first surface side of the semiconductor substrate having the first surface and the second surface facing each other is substantially the same as the first surface of the semiconductor substrate. The multiplying portion provided near the surface of the light receiving portion forming the surface is formed by using a semiconductor having a narrower bandgap than the semiconductor substrate. As a result, the lattice mismatch at the interface between the light receiving portion and the multiplying portion is alleviated, and the generation of dark current can be reduced.
(1)
A semiconductor substrate having a first surface and a second surface facing each other and having a pixel array portion in which a plurality of pixels are arranged in an array.
Each pixel is embedded and formed on the first surface side of the semiconductor substrate to generate carriers according to the amount of light received by photoelectric conversion, and a light receiving portion made of a semiconductor having a narrower bandgap than the semiconductor substrate.
It is provided near the surface of the light receiving portion that forms substantially the same surface as the first surface of the semiconductor substrate, multipliers the carriers generated in the light receiving portion, and has a narrower bandgap than the semiconductor substrate. A photodetector provided with a photomultiplier tube made of the semiconductor.
(2)
The photodetector according to (1), wherein the multiplying portion is provided inside the light receiving portion or on the light receiving portion.
(3)
The light receiving portion is formed of a first semiconductor region having a first conductive type, and is formed of a first semiconductor region.
The photomultiplier tube is formed by a second semiconductor region having a second conductive type, and is formed by a second semiconductor region.
The photodetector according to (1) or (2) above, wherein an avalanche multiplying region is formed at an interface between the first semiconductor region and the second semiconductor region.
(4)
The photodetector according to (3), wherein the light receiving unit further has a first conductive type third semiconductor region having a higher impurity concentration than the first semiconductor region in the vicinity of the semiconductor substrate.
(5)
The photodetection according to (4) above, wherein the third semiconductor region has different impurity concentrations or impurities in the side surface portion of the light receiving portion and the bottom portion of the semiconductor substrate facing the second surface. Device.
(6)
The light receiving portion has an impurity concentration gradient in which the impurity concentration decreases continuously or stepwise from the second surface side of the semiconductor substrate toward the first surface side. The photodetector according to any one of 5).
(7)
Any of the above (3) to (6), which is provided along the side surface of the multiplying portion formed inside the light receiving portion and further has a guard ring for relaxing the edge electric field of the multiplying portion. The photodetector according to one.
(8)
The guard ring has the same conductive type as the second semiconductor region forming the multiplying portion, and is formed by a fourth semiconductor region having a lower impurity concentration than the second semiconductor region (7). The photodetector according to.
(9)
Further, it has a first electrode electrically connected to the light receiving portion and a second electrode electrically connected to the multiplying portion.
The first electrode is electrically connected to the light receiving portion via a first contact electrode having the first conductive type provided near the surface of the light receiving portion.
The second electrode is electrically connected to the multiplying portion via a second contact electrode having the second conductive type provided near the surface of the multiplying portion (3) to the above. The photodetector according to any one of (8).
(10)
The first contact electrode is provided inside the light receiving portion or on the light receiving portion.
The photodetector according to (9), wherein the second contact electrode is provided inside the multiplying portion or on the multiplying portion.
(11)
The photodetector according to (9) or (10), wherein the first contact electrode is continuously or intermittently provided around the multiplying portion in a plan view.
(12)
The photodetector according to any one of (1) to (11) above, wherein the multiplying portion has a polygonal shape or a circular shape in a plan view.
(13)
The photodetector according to any one of (1) to (12), wherein the side surface of the multiplying portion is inclined.
(14)
Further having a buffer layer made of a semiconductor having a lattice constant between the semiconductor substrate and the light receiving portion is between the lattice constant of the semiconductor constituting the semiconductor substrate and the lattice constant of the semiconductor constituting the light receiving portion. , The photodetector according to any one of (1) to (13).
(15)
The photodetector according to any one of (1) to (4) above, wherein the semiconductor substrate further has a separating portion for partitioning each of the plurality of pixels.
(16)
The photodetector according to (15), wherein the separated portion is composed of a conductive film having a light-shielding property and an insulating film provided between the conductive film and the semiconductor substrate.
(17)
The photodetector according to (15) above, wherein the separation portion is formed by a conductive type semiconductor region different from the light receiving portion.
(18)
The photodetector according to any one of (1) to (17) above, wherein the semiconductor is germanium or silicon germanium.
(19)
The photodetector according to any one of (1) to (18) above, wherein the semiconductor substrate is a silicon substrate.
(20)
It includes an optical system, a light detection device, and a signal processing circuit that calculates the distance from the output signal of the light detection device to the object to be measured.
The photodetector is
A semiconductor substrate having a first surface and a second surface facing each other and having a pixel array portion in which a plurality of pixels are arranged in an array.
Each pixel is embedded and formed on the first surface side of the semiconductor substrate to generate carriers according to the amount of light received by photoelectric conversion, and a light receiving portion made of a semiconductor having a narrower bandgap than the semiconductor substrate.
It is provided near the surface of the light receiving portion that forms substantially the same surface as the first surface of the semiconductor substrate, multipliers the carriers generated in the light receiving portion, and has a narrower bandgap than the semiconductor substrate. A distance measuring device having a photomultiplier tube made of the semiconductor.

1,1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J ... Photodetector, 10 ... Sensor substrate, 11,21 ... Semiconductor substrate, 12 ... Light receiving element, 12X ... Avalanche multiplying region, 13 ... light receiving part, 14 ... multiplying part, 15 ... n-type contact electrode, 16 ... p-type contact electrode, 17 ... pixel separation part, 17A ... light-shielding film, 17B ... insulating film, 18, 22 ... multilayer wiring layer, 19 ... Buffer layer, 20 ... Logic substrate, 31 ... Microlens, 32 ... Light-shielding part, 41 ... Semiconductor layer, 100A ... Pixel array part, 1000 ... Distance imager.

Claims (20)

A semiconductor substrate having a first surface and a second surface facing each other and having a pixel array portion in which a plurality of pixels are arranged in an array.
Each pixel is embedded and formed on the first surface side of the semiconductor substrate to generate carriers according to the amount of light received by photoelectric conversion, and a light receiving portion made of a semiconductor having a narrower bandgap than the semiconductor substrate.
It is provided near the surface of the light receiving portion that forms substantially the same surface as the first surface of the semiconductor substrate, multipliers the carriers generated in the light receiving portion, and has a narrower bandgap than the semiconductor substrate. A photodetector provided with a photomultiplier tube made of the semiconductor. The photodetector according to claim 1, wherein the multiplying portion is provided inside the light receiving portion or on the light receiving portion. The light receiving portion is formed of a first semiconductor region having a first conductive type, and is formed of a first semiconductor region.
The photomultiplier tube is formed by a second semiconductor region having a second conductive type, and is formed by a second semiconductor region.
The photodetector according to claim 1, wherein an avalanche multiplying region is formed at an interface between the first semiconductor region and the second semiconductor region. The photodetector according to claim 3, further comprising the first conductive type third semiconductor region having a higher impurity concentration than the first semiconductor region in the vicinity of the semiconductor substrate. The photodetector according to claim 4, wherein the third semiconductor region has different impurity concentrations or impurities in the side surface portion of the light receiving portion and the bottom portion of the semiconductor substrate facing the second surface. .. The first aspect of the present invention, wherein the light receiving portion has an impurity concentration gradient in which the impurity concentration decreases continuously or stepwise from the second surface side of the semiconductor substrate toward the first surface side. Photodetector. The photodetector according to claim 3, further comprising a guard ring provided along the side surface of the multiplying portion formed inside the light receiving portion and relaxing the edge electric field of the multiplying portion. According to claim 7, the guard ring has the same conductive type as the second semiconductor region forming the multiplying portion, and is formed by a fourth semiconductor region having a lower impurity concentration than the second semiconductor region. The photodetector described. Further, it has a first electrode electrically connected to the light receiving portion and a second electrode electrically connected to the multiplying portion.
The first electrode is electrically connected to the light receiving portion via a first contact electrode having the first conductive type provided near the surface of the light receiving portion.
The third aspect of the present invention, wherein the second electrode is electrically connected to the multiplying portion via a second contact electrode having the second conductive type provided near the surface of the multiplying portion. Photodetector. The first contact electrode is provided inside the light receiving portion or on the light receiving portion.
The photodetector according to claim 9, wherein the second contact electrode is provided inside the multiplying portion or on the multiplying portion. The photodetector according to claim 9, wherein the first contact electrode is continuously or intermittently provided around the multiplying portion in a plan view. The photodetector according to claim 1, wherein the multiplying portion has a polygonal shape or a circular shape in a plan view. The photodetector according to claim 1, wherein the side surface of the multiplying portion is inclined. Further having a buffer layer made of a semiconductor having a lattice constant between the semiconductor substrate and the light receiving portion is between the lattice constant of the semiconductor constituting the semiconductor substrate and the lattice constant of the semiconductor constituting the light receiving portion. , The photodetector according to claim 1. The photodetector according to claim 1, wherein the semiconductor substrate further has a separating portion for partitioning each of the plurality of pixels. The photodetector according to claim 15, wherein the separation portion is composed of a conductive film having a light-shielding property and an insulating film provided between the conductive film and the semiconductor substrate. The photodetector according to claim 15, wherein the separated portion is formed of a conductive type semiconductor region different from the light receiving portion. The photodetector according to claim 1, wherein the semiconductor is germanium or silicon germanium. The photodetector according to claim 1, wherein the semiconductor substrate is a silicon substrate. It includes an optical system, a light detection device, and a signal processing circuit that calculates the distance from the output signal of the light detection device to the object to be measured.
The photodetector is
A semiconductor substrate having a first surface and a second surface facing each other and having a pixel array portion in which a plurality of pixels are arranged in an array.
Each pixel is embedded and formed on the first surface side of the semiconductor substrate to generate carriers according to the amount of light received by photoelectric conversion, and a light receiving portion made of a semiconductor having a narrower bandgap than the semiconductor substrate.
It is provided near the surface of the light receiving portion that forms substantially the same surface as the first surface of the semiconductor substrate, multipliers the carriers generated in the light receiving portion, and has a narrower bandgap than the semiconductor substrate. A distance measuring device having a photomultiplier tube made of the semiconductor.

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