Distance measuring device

Abstract

[Problem] To provide a ranging device with which it is possible to improve quantum efficiency and resolution. [Solution] The ranging device according to the present disclosure comprises: a semiconductor layer having a first surface and a second surface on the opposite side from the first surface; a lens provided on the second surface side; first and second charge accumulation parts provided in the semiconductor layer on the first surface side; a photoelectric conversion unit that is in contact with the semiconductor layer on the first surface side and that is made of a different material to the semiconductor layer; first and second voltage application units that apply a voltage to the part of the semiconductor layer between the first and second charge accumulation parts and the photoelectric conversion unit; and a waveguide part that extends in the semiconductor layer from the second surface to the photoelectric conversion unit and that is made of a different material to the semiconductor layer.

Description

[Technical Field]

[0001] The present disclosure relates to a distance measuring device. [Background technology]

[0002] Distance measuring devices using the indirect Time of Flight (iToF) method have been developed. Indirect ToF distance measuring devices indirectly calculate the distance from the device to an object based on the phase difference between the emitted light and the reflected light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-013909 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional distance measuring devices using the indirect ToF method have photodiodes embedded in a silicon substrate, which makes it impossible to achieve sufficient quantum efficiency Qe (sensitivity). Furthermore, distance measuring devices using silicon substrates with high infrared transmittance require thicker silicon substrates to increase quantum efficiency. However, thicker silicon substrates make it difficult to electrically or optically isolate adjacent pixels, which leads to problems such as a degradation of the signal-to-noise ratio (SNR) and reduced resolution.

[0005] Therefore, the present disclosure has been made in consideration of such problems, and provides a distance measuring device that can improve quantum efficiency and resolution. [Means for solving the problem]

[0006] A distance measuring device according to one aspect of the present disclosure includes a semiconductor layer having a first surface and a second surface opposite the first surface, a lens provided on the second surface side, first and second charge accumulation units provided within the semiconductor layer on the first surface side, a photoelectric conversion unit in contact with the semiconductor layer on the first surface side and made of a material different from the semiconductor layer, first and second voltage application units that apply a voltage to the semiconductor layer between the first and second charge accumulation units and the photoelectric conversion unit, and a waveguide extending within the semiconductor layer from the second surface to the photoelectric conversion unit and made of a material different from the semiconductor layer.

[0007] The area of the end face of the waveguide on the first surface side may be smaller than the area of the end face of the waveguide on the second surface side.

[0008] The waveguide section may have an area at the end face on the second surface side equal to or greater than the opening that passes incident light from the lens to the semiconductor layer, and an area at the end face on the first surface side equal to or less than the area of the photoelectric conversion section, and the side surface between the first surface and the second surface may be inclined from the perpendicular direction to the first surface or the second surface.

[0009] The refractive index of the waveguide may be higher than the refractive index of the semiconductor layer.

[0010] The refractive index of the waveguide may be lower than the refractive index of the lens.

[0011] The waveguide may further include a metal layer provided on a side surface of the waveguide.

[0012] The semiconductor layer may be made of silicon, the photoelectric conversion section may be made of germanium, InGaAs, CIGS (Copper Indium Gallium Di Selenide), or Qdot (Quantum Dot), and the waveguide section may be made of a resin material.

[0013] The light-emitting device may further include a mixed layer provided between the photoelectric conversion section and the semiconductor layer, the mixed layer being a mixture of the material of the photoelectric conversion section and the material of the semiconductor layer.

[0014] The waveguide may further include an additional waveguide provided on the second surface side, wherein the area of a first end face of the waveguide on the first surface side is larger than the area of a second end face of the waveguide on the second surface side, and the area of a third end face of the additional waveguide facing the second end face of the waveguide may be smaller than the area of a fourth end face of the additional waveguide located on the opposite side to the third end face.

[0015] The first voltage application unit is a first gate electrode provided on the first surface between the first charge accumulation unit and the photoelectric conversion unit and insulated from the semiconductor layer, and the second voltage application unit is a second gate electrode provided on the first surface between the second charge accumulation unit and the photoelectric conversion unit and insulated from the semiconductor layer, and may further include a second wiring provided on the first surface side and connected to the first voltage application unit, and a third wiring provided on the first surface side and connected to the second voltage application unit.

[0016] The first and second voltage application sections may be provided on the first surface of the semiconductor layer via an insulating film.

[0017] The first and second voltage application units may be embedded into the semiconductor layer from the first surface of the semiconductor layer.

[0018] The first voltage application section may be adjacent to the first charge accumulation section on the first surface and may be a first impurity layer having a different conductivity type than the first charge accumulation section, and the second voltage application section may be adjacent to the second charge accumulation section on the first surface and may be a second impurity layer having a different conductivity type than the second charge accumulation section, and may further include a second wiring provided on the first surface side and connected to the first voltage application section, and a third wiring provided on the first surface side and connected to the second voltage application section.

[0019] The photoelectric conversion portion may be smaller than the opening that passes incident light from the lens to the semiconductor layer when viewed from above the second surface of the semiconductor layer.

[0020] The photoelectric conversion element may further include a metal layer made of a conductive and light-reflecting material, covering the periphery of the photoelectric conversion element except for the contact area between the photoelectric conversion element and the semiconductor layer. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a distance measuring device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the schematic configuration of a light receiving element of the distance measuring device according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing an example of a circuit configuration of a pixel. [Figure 4] FIG. 4 is a plan view showing an example of the arrangement of the pixel circuits shown in FIG. 3. [Figure 5] FIG. 2 is a cross-sectional view showing an example of the configuration of a pixel according to the first embodiment. [Figure 6] FIG. 3 is a timing chart showing an example of the operation of the distance measuring device according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing an example of the configuration of a pixel according to a second embodiment. [Figure 8] FIG. 10 is a cross-sectional view showing an example of the configuration of a pixel according to a third embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing an example of the configuration of a pixel according to a fourth embodiment. [Figure 10] FIG. 11 is a cross-sectional view showing an example of the configuration of a pixel according to a fifth embodiment. [Figure 11] FIG. 13 is a cross-sectional view showing an example of the configuration of a pixel according to a sixth embodiment. [Figure 12] FIG. 13 is a cross-sectional view showing an example of the configuration of a pixel according to the seventh embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a configuration example of a light receiving element according to a seventh embodiment. [Figure 14] FIG. 19 is a cross-sectional view showing an example of the configuration of a pixel according to the eighth embodiment. [Figure 15] FIG. 13 is a plan view showing an example of the configuration of a light receiving element according to an eighth embodiment. [Figure 16] FIG. 13 is a cross-sectional view showing an example of the configuration of a light-receiving element according to a ninth embodiment. [Figure 17] FIG. 23 is a cross-sectional view showing an example of the configuration of a pixel according to a tenth embodiment. [Figure 18] FIG. 23 is a cross-sectional view showing an example of the configuration of a pixel according to the eleventh embodiment. [Figure 19] FIG. 1 is a plan view showing an example of a pixel layout according to the present disclosure. [Figure 20]FIG. 10 is a plan view showing another example of a pixel layout according to the present disclosure. [Figure 21] FIG. 1 is a block diagram showing an example configuration of a smartphone as an electronic device to which the present technology is applied. [Figure 22] 1 is a block diagram showing a schematic configuration example of a vehicle control system that is an example of a mobile object control system to which the technology according to the present disclosure can be applied. [Figure 23] FIG. 3 is a diagram showing an example of an installation position of an imaging unit. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, specific embodiments to which the present technology is applied will be described in detail with reference to the drawings. The drawings are schematic or conceptual, and the proportions of each part are not necessarily the same as those in reality. In the specification and drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0023] (First embodiment) 1 is a block diagram showing an example of the configuration of a distance measuring device according to a first embodiment. The distance measuring device 100 is an indirect ToF (hereinafter also referred to as iToF) distance measuring device, and is used, for example, in an in-vehicle system that is mounted on a vehicle and measures the distance to an object outside the vehicle. The distance measuring device 100 may also be used, for example, in a system for identifying an individual, such as face authentication.

[0024] The distance measuring device 100 includes a light receiving element 1, a light emitting element 2, a modulator 3, and a PLL (Phase Locked Loop) 4. The PLL 4 generates a pulse signal. The modulator 3 modulates the pulse signal from the PLL 4 to generate a control signal. The frequency of the control signal may be, for example, 5 MHz to 20 MHz. The light emitting element 2 emits light in accordance with the control signal from the modulator. The light emitting element 2 has a light emitting diode that emits infrared light with a wavelength in the range of 780 nm to 1000 nm as a light source, and generates irradiated light in synchronization with a rectangular wave or sine wave control signal. The light generated by the light emitting element 2 may be, for example, short wave infrared light (SWIR (Short Wave Infrared Radiometer)). The irradiated light emitted from the light emitting element 2 is reflected by an object M and received by the light receiving element 1.

[0025] The reflected light received by the light receiving element 1 is delayed from the timing at which the light emitting element 2 emits light according to the distance to the object M. A phase difference occurs between the emitted light and the reflected light due to the delay time of the reflected light relative to the emitted light. In the iToF method, the distance measuring device 100 calculates the phase difference between the emitted light and the reflected light, and determines the distance (depth information) from the distance measuring device 100 to the object M based on this phase difference.

[0026] 2 is a block diagram showing a schematic configuration example of a light receiving element of the distance measuring device according to Embodiment 1. The light receiving element 1 is an element used in the distance measuring device 100 using the iToFF method shown in FIG.

[0027] The light receiving element 1 receives light (reflected light) that is emitted by the light emitting element 2 acting as a light source, hits an object, and is reflected back, and outputs a depth image that represents distance information to the object as a depth value.

[0028] The light receiving element 1 has a pixel array section 21 provided on a semiconductor substrate (not shown) and a peripheral circuit section provided on the same semiconductor substrate. The peripheral circuit section is composed of, for example, a vertical drive section 22, a column processing section 23, a horizontal drive section 24, a system control section 25, a signal processing section 26, and a data storage section 27. All or part of the peripheral circuit section may be provided on the same semiconductor substrate as the light receiving element 1, or may be provided on a substrate separate from the light receiving element 1.

[0029] The pixel array section 21 has a plurality of pixels 10 arranged two-dimensionally in a matrix of rows and columns. The pixels 10 generate charges according to the amount of light received and output signals according to the charges. That is, the pixels 10 perform photoelectric conversion on the incident light and output signals according to the resulting charges. Details of the pixels 10 will be described later. Note that the row direction is the horizontal direction in FIG. 2, and the column direction is the vertical direction.

[0030] In the pixel array unit 21, pixel drive lines 28 are wired in the row direction for each pixel row in the matrix-like pixel arrangement, and two vertical signal lines 29 are wired in the column direction for each pixel column. For example, the pixel drive lines 28 transmit drive signals for driving the pixels 10 when reading out signals. Note that although FIG. 2 shows the pixel drive line 28 as a single line, the number of pixel drive lines 28 is not limited to one. One end of the pixel drive line 28 is connected to an output terminal of the vertical drive unit 22 corresponding to each row.

[0031] The vertical drive unit 22 is composed of a shift register, an address decoder, etc., and drives each pixel 10 of the pixel array unit 21 simultaneously for all pixels or in row units, etc. In other words, the vertical drive unit 22, together with the system control unit 25 that controls the vertical drive unit 22, constitutes a drive unit that controls the operation of each pixel 10 of the pixel array unit 21.

[0032] The detection signals output from each pixel 10 in a pixel row in response to drive control by the vertical drive unit 22 are input to the column processing unit 23 through vertical signal lines 29. The column processing unit 23 performs predetermined signal processing on the detection signals output from each pixel 10 through the vertical signal lines 29, and temporarily stores the processed detection signals. Specifically, the column processing unit 23 performs noise removal processing, AD (Analog-to-Digital) conversion processing, and the like as signal processing.

[0033] The horizontal driving unit 24 is configured with a shift register, an address decoder, etc., and sequentially selects unit circuits corresponding to pixel columns in the column processing unit 23. Through selective scanning by the horizontal driving unit 24, detection signals that have been signal-processed for each unit circuit in the column processing unit 23 are sequentially output.

[0034] The system control unit 25 is composed of a timing generator that generates various timing signals, and controls the driving of the vertical driving unit 22, column processing unit 23, horizontal driving unit 24, etc. based on the various timing signals generated by the timing generator.

[0035] The signal processing unit 26 has an arithmetic processing function and performs various signal processing such as arithmetic processing based on the detection signal output from the column processing unit 23. The data storage unit 27 temporarily stores data necessary for signal processing in the signal processing unit 26.

[0036] The light receiving element 1 configured as described above includes distance information to an object as a depth value in a pixel value, and outputs this pixel value as a depth image. The light receiving element 1 can be installed, for example, in an in-vehicle system that is installed in a vehicle and measures the distance to an object outside the vehicle.

[0037] 3 is a diagram showing an example of the circuit configuration of the pixel 10. The pixel 10 includes a photodiode PD, transfer transistors TRG1 and TRG2, floating diffusion regions FD1 and FD2, additional capacitances FDL1 and FDL2, switching transistors FDG1 and FDG2, amplification transistors AMP1 and AMP2, reset transistors RST1 and RST2, selection transistors SEL1 and SEL2, and a charge discharging transistor OFG.

[0038] The photodiode PD is a photoelectric conversion element that generates an electric charge in response to received light.

[0039] The transfer transistors TRG1, TRG2, switching transistors FDG1, FDG2, amplification transistors AMP1, AMP2, selection transistors SEL1, SEL2, reset transistors RST1, RST2, and charge discharging transistor OFG are configured, for example, by N-type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0040] The transfer transistor TRG1 becomes conductive when a transfer signal applied to the gate electrode TRG1g becomes active (for example, high level), and transfers the charge accumulated in the photodiode PD to the floating diffusion region FD1. The transfer transistor TRG2 becomes conductive when a transfer signal applied to the gate electrode TRG2g becomes active, and transfers the charge accumulated in the photodiode PD to the floating diffusion region FD2.

[0041] The floating diffusion regions FD1 and FD2 are charge storage portions that can store the charges transferred from the photodiode PD.

[0042] When a switching signal FDG1g is activated, the switching transistor FDG1 is turned on, connecting the additional capacitance FDL1 to the floating diffusion region FD1. When a switching signal FDG2g is activated, the switching transistor FDG2 is turned on, connecting the additional capacitance FDL2 to the floating diffusion region FD2. The additional capacitances FDL1 and FDL2 may be formed of capacitive elements such as MoM (Metal-on-Metal), MIM (Metal-Insulator-Metal), or MOS capacitors. In the iToF, the switching transistors FDG1 and FDG2 are turned on when accumulating charge due to incident light and are electrically connected to the floating diffusion regions FD1 and FD2, respectively. This allows the pixel 10 to suppress saturation of signal charge in the floating diffusion regions FD1 and FD2 and accumulate charge.

[0043] When the reset drive signal RSTg is activated, the reset transistor RST1 is turned on and resets the potential of the floating diffusion region FD1. When the reset drive signal RSTg is activated, the reset transistor RST2 is turned on and resets the potential of the floating diffusion region FD2. When the reset transistors RST1 and RST2 are activated, the switching transistors FDG1 and FDG2 are also activated at the same time, and the additional capacitances FDL1 and FDL2 are also reset.

[0044] For example, in an iToF, when accumulating charges generated by incident light, the vertical drive unit 22 turns on the switching transistors FDG1 and FDG2 to connect the floating diffusion region FD1 to the additional capacitance FDL1 and also connect the floating diffusion region FD2 to the additional capacitance FDL2, thereby enabling a large amount of charges to be accumulated.

[0045] On the other hand, to increase the quantum efficiency, the vertical drive unit 22 may turn off the switching transistors FDG1 and FDG2 to disconnect the additional capacitances FDL1 and FDL2 from the floating diffusion regions FD1 and FD2, respectively. In this way, by switching the switching transistors FDG1 and FDG2, the dynamic range of the light receiving element 1 can be increased.

[0046] The charge drain transistor OFG is turned on when the drain signal OFG1g is activated, and drains the charge accumulated in the photodiode PD. The charge drain transistor OFG is used when the charge in the photodiode PD overflows due to strong incident light.

[0047] The source electrode of the amplifier transistor AMP1 is connected to a vertical signal line 29A via a selection transistor SEL1. This connects the amplifier transistor AMP1 to a constant current source (not shown) to form a source follower circuit. The source electrode of the amplifier transistor AMP2 is connected to a vertical signal line 29B via a selection transistor SEL2. This connects the amplifier transistor AMP2 to a constant current source (not shown) to form a source follower circuit.

[0048] The selection transistor SEL1 is connected between the source electrode of the amplification transistor AMP1 and the vertical signal line 29A. When the selection signal SEL1g is activated, the selection transistor SEL1 is turned on and outputs the detection signal VSL1 output from the amplification transistor AMP1 to the vertical signal line 29A.

[0049] The selection transistor SEL2 is connected between the source electrode of the amplification transistor AMP2 and the vertical signal line 29B. When the selection signal SEL2g is activated, the selection transistor SEL2 is turned on and outputs the detection signal VSL2 output from the amplification transistor AMP2 to the vertical signal line 29B.

[0050] The transfer transistors TRG1 and TRG2, the switching transistors FDG1 and FDG2, the amplification transistors AMP1 and AMP2, the selection transistors SEL1 and SEL2, and the charge discharging transistor OFG of the pixel 10 are controlled by a vertical drive unit 22.

[0051] As described above, when charges generated by incident light are stored in the iToF, the additional capacitances FDL1 and FDL2 are connected to the floating diffusion regions FD1 and FD2, respectively. Therefore, the switching transistors FDG1 and FDG2 may be omitted in the iToF pixel 10.

[0052] Next, the operation of the pixel 10 will be briefly described.

[0053] First, before light reception begins, a reset operation is performed on all pixels to reset the charges in the pixels 10. That is, the charge drain transistor OFG, reset transistors RST1 and RST2, and switching transistors FDG1 and FDG2 are turned on, and the charges stored in the photodiode PD, floating diffusion regions FD1 and FD2, and additional capacitances FDL1 and FDL2 are drained.

[0054] After the accumulated charge is discharged, light reception begins.

[0055] During the light-receiving period, the transfer transistors TRG1 and TRG2 are alternately driven. For example, during the first period, the transfer transistor TRG1 is in a conductive state (hereinafter referred to as "on"), and the transfer transistor TRG2 is in a non-conductive state (hereinafter referred to as "off"). At this time, the charge generated in the photodiode PD is transferred to the floating diffusion region FD1 and the additional capacitance FDL1. During the second period following the first period, the transfer transistor TRG1 is turned off, and the transfer transistor TRG2 is turned on. During the second period, the charge generated in the photodiode PD is transferred to the floating diffusion region FD2 and the additional capacitance FDL2. As a result, the charge generated in the photodiode PD is distributed and accumulated in the floating diffusion regions FD1 and FD2.

[0056] The first and second periods are alternately repeated periodically in synchronization with the light emitted from the light-emitting element 2. This allows the floating diffusion regions FD1, FD2 and the additional capacitances FDL1, FDL2 to store charges according to the phase difference between the light emitted from the light-emitting element 2 and the reflected light received by the light-receiving element 1. The relationship between the phase difference and the charges stored in the floating diffusion regions FD1, FD2 and the additional capacitances FDL1, FDL2 will be described later.

[0057] Then, when the light reception period ends, each pixel 10 in the pixel array unit 21 is selected in sequence. In the selected pixel 10, the selection transistors SEL1 and SEL2 are turned on. As a result, the charges accumulated in the floating diffusion region FD1 and the additional capacitance FDL1 are output as a detection signal VSL1 to the column processing unit 23 via the vertical signal line 29A. The charges accumulated in the floating diffusion region FD2 and the additional capacitance FDL2 are output as a detection signal VSL2 to the column processing unit 23 via the vertical signal line 29B.

[0058] When one light receiving operation is completed in this manner, the next light receiving operation is performed, starting with a reset operation.

[0059] The reflected light received by pixel 10 is delayed from the time of illumination by the light source depending on the distance to the object. The delay time depending on the distance to the object causes a phase difference between the illuminated light and the reflected light, which changes the distribution ratio of the charges accumulated in additional capacitances FDL1 and FDL2 (or floating diffusion regions FD1 and FD2). Thus, by detecting the potentials of floating diffusion regions FD1 and FD2, the phase difference between the illuminated light and the reflected light can be calculated, and the distance to the object can be determined based on this phase difference.

[0060] Fig. 4 is a plan view showing an example of the arrangement of the pixel circuits shown in Fig. 3. The horizontal direction in Fig. 4 corresponds to the row direction (horizontal direction) in Fig. 2, and the vertical direction corresponds to the column direction (vertical direction) in Fig. 2.

[0061] As shown in FIG. 4, an N+ type impurity layer 52 is provided in an N type semiconductor layer 51. A photodiode PD is provided in the impurity layer 52. When viewed from above the surface of the semiconductor layer 51, the impurity layer 52 and the photodiode PD have a substantially rectangular outer shape, and the photodiode PD is provided inside the impurity layer 52. The size of the planar layout of the photodiode PD is not particularly limited. Because the waveguide 55 guides most of the incident light, the size of the planar layout of the photodiode PD only needs to be substantially equal to or larger than the end face of the waveguide 55 on the surface F1 side. This allows the photodiode PD to sufficiently receive the incident light guided by the waveguide 55, thereby improving quantum efficiency.

[0062] Outside the impurity layer 52, along a predetermined one of the four sides of the rectangular pixel 10, the transfer transistor TRG1, switching transistor FDG1, reset transistor RST1, amplifier transistor AMP1, and select transistor SEL1 are linearly arranged. Along another of the four sides of the rectangular pixel 10, the transfer transistor TRG2, switching transistor FDG2, reset transistor RST2, amplifier transistor AMP2, and select transistor SEL2 are linearly arranged. Furthermore, the charge drain transistor OFG is arranged on a side of the pixel 10 other than the two sides on which the transfer transistors TRG1, TRG2, etc. are provided. For example, the charge drain transistor OFG is arranged on a side opposite the side on which the transfer transistors TRG1, FDG1, RST1, AMP1, and SEL1 are provided. The pixel circuit arrangement shown in FIG. 4 is not limited to this example, and other arrangements may be used.

[0063] Fig. 5 is a cross-sectional view showing an example of the configuration of a pixel 10 according to the first embodiment. Although Fig. 5 shows one pixel 10, a plurality of pixels 10 are arranged two-dimensionally in parallel in the pixel array section 21.

[0064] The pixel 10 includes a semiconductor layer 51, an on-chip lens 47, an anti-reflection film 43, a light-shielding film 45, an inter-pixel isolation portion 61, an impurity layer 52, a waveguide portion 55, floating diffusion regions FD1 and FD2, a photodiode PD, transfer transistors TRG1 and TRG2, vias V1 to V4, Vbias, wirings M1 to M4, Mbias, and additional capacitances FDL1 and FDL2.

[0065] The semiconductor layer 51 is made of, for example, silicon and has a thickness of, for example, 1 μm to 6 μm. The semiconductor layer 51 is, for example, an N-type semiconductor layer. The semiconductor layer 51 has a front surface F1 as a first surface and a back surface F2 as a second surface opposite to the front surface F1. A multilayer wiring structure including wirings M1 to M4 and Mbias is provided on the front surface F1 side. An on-chip lens 47 for receiving light is provided on the back surface F2 side. Therefore, the light receiving element 1 according to the present disclosure is a back-illuminated element, and receives light on the back surface F2 opposite to the front surface F1 on which the wirings M1 to M4 and Mbias are provided. The back surface F2 of the semiconductor layer 51 is the light incident surface.

[0066] An anti-reflection film 43 is provided on the rear surface F2 of the semiconductor layer 51. The anti-reflection film 43 may have a laminated structure in which a fixed charge film and an oxide film are stacked. For example, the anti-reflection film 43 may be a high-dielectric-constant (High-k) insulating film formed by atomic layer deposition (ALD). More specifically, the anti-reflection film 43 may be a metal oxide film such as hafnium oxide (HfO), aluminum oxide (AlO), titanium oxide (TiO), tantalum oxide (TaO), or STO (Strontium Titan Oxide).

[0067] A light-shielding film 45 is provided in an area other than the anti-reflection film 43 on the rear surface F2 of the semiconductor layer 51. The light-shielding film 45 is provided adjacent to the periphery of the anti-reflection film 43 and prevents incident light from entering from areas other than the anti-reflection film 43. In other words, the light-shielding film 45 defines an opening OP that allows incident light to pass from the on-chip lens 47 to the semiconductor layer 51. The light-shielding film 45 is made of a light-shielding material and may be made of a metal material such as tungsten (W), aluminum (Al), or copper (Cu).

[0068] The inter-pixel isolation portions 61 are provided at the boundaries between adjacent pixels 10 in the semiconductor layer 51, and separate the adjacent pixels 10. The inter-pixel isolation portions 61 prevent incident light from leaking to adjacent pixels (i.e., crosstalk). The inter-pixel isolation portions 61 are also made of a light-shielding material, and may be made of a metal material such as tungsten (W), aluminum (Al), or copper (Cu). Although not shown, the bottom and side surfaces of the inter-pixel isolation portions 61 may be coated with a light-reflecting material. This increases the amount of light incident on the photodiode PD, improving the quantum efficiency of the pixel 10.

[0069] A planarization film 46 is provided on the anti-reflection film 43 and the light-shielding film 45. The planarization film 46 is made of, for example, an insulating film such as silicon oxide (SiO), silicon nitride (SiN), or silicon oxynitride (SiON), or an organic material such as resin.

[0070] An on-chip lens 47 is provided on the planarization film 46 for each pixel 10. The on-chip lens 47 is provided on the back surface F2 of the semiconductor layer 51, and is made of a resin material such as a styrene-based resin, an acrylic-based resin, a styrene-acrylic copolymer resin, or a siloxane-based resin. Light collected by the on-chip lens 47 is incident on the photodiode PD via the antireflection film 43 and the semiconductor layer 51.

[0071] Meanwhile, a photodiode PD is provided on the front surface F1 side of the semiconductor layer 51 as an example of a photoelectric conversion unit. The photodiode PD is provided on the front surface F1 of the semiconductor layer 51 so as to be in contact with the semiconductor layer 51 and is made of a material different from that of the semiconductor layer 51. The photodiode PD is made of a material with a higher quantum efficiency (photoelectric conversion efficiency) than silicon, such as germanium, InGaAs, CIGS (Copper Indium Gallium Di Selenide), or Qdot (Quantum Dot). The photodiode PD generates charges according to the amount of light it receives. Furthermore, the photodiode PD protrudes somewhat from the front surface F1 toward the back surface F2 into the semiconductor layer 51 or the impurity layer 52. This shortens the path from the photodiode PD to the floating diffusion regions FD1 and FD2 via the transfer transistors TRG1 and TRG2, improving the charge transfer efficiency and transfer speed.

[0072] The photodiode PD is connected to a wiring Mbias through a via Vbias serving as a first wiring. The wiring Mbias is provided on the front surface F1 side and is electrically connected to the photodiode PD in order to apply a predetermined bias voltage to the photodiode PD. For example, by applying a positive voltage (e.g., about +0.5 V) to the wiring Mbias, charges (e.g., electrons) photoelectrically converted by the photodiode PD are more likely to be taken into the impurity layer 52.

[0073] The impurity layer 52 is provided on the surface F1 side in the semiconductor layer 51 and is in contact with the photodiode PD. The impurity layer 52 is, for example, an N-type impurity layer having a higher impurity concentration than the semiconductor layer 51, and captures charges photoelectrically converted by the photodiode PD.

[0074] Floating diffusion regions FD1 and FD2, which are examples of first and second charge accumulation portions, are provided on both sides of the impurity layer 52. The floating diffusion regions FD1 and FD2 are provided in the semiconductor layer 51 on the front surface F1 side, and temporarily hold or accumulate the charges transferred from the photodiode PD. The floating diffusion regions FD1 and FD2 are, for example, N-type impurity layers, and contain a higher concentration of impurities than the semiconductor layer 51.

[0075] As an example of a first voltage application unit, a gate electrode TRG1g of the transfer transistor TRG1 is provided on the surface F1 between the floating diffusion region FD1 and the photodiode PD or the impurity layer 52. The gate electrode TRG1g is provided on the surface F1 via a gate insulating film and is electrically insulated from the semiconductor layer 51. The gate electrode TRG1g can apply a voltage to the semiconductor layer 51 between the floating diffusion region FD1 and the photodiode PD or the impurity layer 52 to bring the transfer transistor TRG1 into a conductive state or a non-conductive state. The gate electrode TRG1g is made of a conductive material such as a metal or polysilicon doped with impurities that act as acceptors or donors.

[0076] As an example of a second voltage application unit, a gate electrode TRG2g of the transfer transistor TRG2 is provided on the surface F1 between the floating diffusion region FD2 and the photodiode PD or the impurity layer 52. The gate electrode TRG2g is provided on the surface F1 via a gate insulating film and is electrically insulated from the semiconductor layer 51. The gate electrode TRG2g applies a voltage to the semiconductor layer 51 between the floating diffusion region FD2 and the photodiode PD or the impurity layer 52, thereby turning the transfer transistor TRG2 into a conductive state or a non-conductive state. The gate electrode TRG2g is made of a conductive material such as a metal or doped polysilicon.

[0077] The gate electrode TRG1g, the impurity layer 52, and the floating diffusion region FD1 constitute a transfer transistor TRG1, which can transfer charges from the impurity layer 52 to the floating diffusion region FD1 by a gate voltage applied to the gate electrode TRG1g.

[0078] The gate electrode TRG2g, the impurity layer 52, and the floating diffusion region FD2 constitute a transfer transistor TRG2, which can transfer charges from the impurity layer 52 to the floating diffusion region FD2 by a gate voltage applied to the gate electrode TRG2g.

[0079] The charges transferred to the floating diffusion regions FD1 and FD2 are stored in the floating diffusion region FD1 and the additional capacitance FDL1 in FIG. 3 or in the floating diffusion region FD2 and the additional capacitance FDL2 in FIG.

[0080] The waveguide 55 extends from the back surface F2 of the semiconductor layer 51 toward the photodiode PD on the front surface F1 side, gradually tapering. The area of the end face E1 of the waveguide 55 on the front surface F1 side is smaller than the area of the end face E2 of the waveguide 55 on the back surface F2 side. The waveguide 55 is provided up to the vicinity of the surface of the impurity layer 52, but does not reach the photodiode PD. In other words, the impurity layer 52 exists between the waveguide 55 and the photodiode PD for charge transfer. The waveguide 55 is made of a different material from the semiconductor layer 51. Like the on-chip lens 47, the waveguide 55 is made of a resin material such as a styrene-based resin, an acrylic-based resin, a styrene-acrylic copolymer-based resin, or a siloxane-based resin. The waveguide 55 may be made of a low refractive index material such as SiO2, MgF, or SiOC, and a high refractive index material such as a-Si, PolySi, SiN, Ta2O5, Al2O3, TiO2, HfO2, or Nb2O. 25 etc. are also acceptable.

[0081] The waveguide 55 reflects at least a part of the incident light at the interface with the semiconductor layer 51, and guides the incident light to the photodiode PD.

[0082] The waveguide 55 has an area equal to or greater than the opening OP at the end face E2 on the back surface F2 side of the semiconductor layer 51, and an area equal to or less than the photodiode PD at the end face E1 on the front surface F1 side. The area of the end face E1 of the waveguide 55 is smaller than the area of the end face E2. The side faces of the waveguide 55 are inclined from the perpendicular direction to the front surface F1, the back surface F2, and the end faces E1 and E2. That is, the waveguide 55 is formed so as to gradually become thinner from the back surface F2 to the front surface F1, and the side faces between the front surfaces F1 and F2 have a tapered shape. This allows the waveguide 55 to guide incident light from the relatively large opening OP to the smaller photodiode PD.

[0083] The waveguide 55 guides the incident light to the photodiode PD, thereby increasing the quantum efficiency of the photodiode PD.

[0084] Furthermore, by guiding the incident light, the photodiode PD can receive a large amount of incident light even if the layout area on the surface F1 of the photodiode PD is reduced. Therefore, by providing the waveguide 55, the photodiode PD can maintain high quantum efficiency and quantum efficiency even if the layout area is reduced. When the layout area of the photodiode PD is reduced, the contact area between the photodiode PD and the semiconductor layer 51 also becomes smaller, and therefore dark current can also be suppressed. In other words, the pixel 10 according to the third embodiment can suppress dark current while maintaining the quantum efficiency of the photodiode PD, thereby achieving both high sensitivity and high resolution.

[0085] The refractive index of the waveguide 55 is preferably higher than the refractive index of the semiconductor layer 51. In this case, incident light in the waveguide 55 can be totally reflected at the interface between the waveguide 55 and the semiconductor layer 51. Preferably, the taper angle θt of the side surface of the waveguide 55 is smaller than the critical angle of the interface between the waveguide 55 and the semiconductor layer 51. This makes it easier for light incident perpendicularly to the back surface F2 to be totally reflected at the interface between the waveguide 55 and the semiconductor layer 51. By totally reflecting the incident light at the interface between the waveguide 55 and the semiconductor layer 51, the waveguide 55 can guide more incident light to the photodiode PD. As a result, the pixel 10 can further improve the quantum efficiency of the photodiode PD.

[0086] When the antireflection film 43 is not provided, it is preferable that the refractive index of the waveguide 55 is lower than the refractive indexes of the on-chip lens 47 and the planarization film 46. This allows incident light to be incident on the waveguide 55 without being reflected at the interface between the on-chip lens 47 or the planarization film 46 and the waveguide 55.

[0087] The gate electrode TRG1g is electrically connected to the wiring M41 serving as the second wiring through vias V11, V21, V31, and V41 and wirings M11, M21, and M31. That is, the wiring M41 is provided on the front surface F1 side and connected to the gate electrode TRG1g. The gate electrode TRG2g is electrically connected to the wiring M42 serving as the third wiring through vias V12, V22, V32, and V42 and wirings M12, M22, and M32. That is, the wiring M42 is provided on the front surface F1 side and connected to the gate electrode TRG2g. The vertical drive unit 22 of FIG. 2 is connected to the wirings M41 and M42 and controls the potentials of the gate electrodes TRG1g and TRG2g through the wirings M41 and M42. This allows the vertical drive unit 22 to drive the transfer transistors TRG1 and TRG2. The wirings M11 to M42, Mbias, vias V11 to V42, and Vbias are made of a conductive metal such as copper. In FIG. 5, the wirings M11 to M42 have a four-layer structure, but the number of wiring layers is not limited, and may be more or less than four.

[0088] The wirings M11, M12, and Mbias are configured in the same wiring layer, and the wirings M21 and M22 are configured in the same wiring layer. The wirings M31 and M32 are configured in the same wiring layer, and the wirings M41 and M42 are configured in the same wiring layer. The wirings M11 and M12 are electrically connected to the gate electrodes TRG1g and TRG2g of the transfer transistors TRG1 and TRG2, respectively, via vias V11 and V12.

[0089] The additional capacitances FDL1 and FDL2 may be, for example, MoM, MIM, or MOS capacitors formed of wiring in the same layer as the wirings M21 and M22 or the wirings M31 and M32. Although not shown here, the additional capacitances FDL1 and FDL2 are electrically connected to the floating diffusion regions FD1 and FD2, respectively, and can store charges together with the floating diffusion regions FD1 and FD2. Furthermore, the additional capacitances FDL1 and FDL2 overlap with the photodiode PD in a plan view from the front surface F1. This allows the layout area of the pixel 10 to be reduced. Of course, the additional capacitances FDL1 and FDL2 may be formed in a conductive layer different from that of the wirings M21 and M22 and the wirings M31 and M32.

[0090] The interlayer insulating film 62 is provided on the surface F1 of the semiconductor layer 51, and covers the wirings M11 to M42, Mbias, vias V11 to V42, Vbias, etc. The interlayer insulating film 62 is made of, for example, an insulating film such as a silicon oxide film.

[0091] Next, the operation of the distance measuring device 100 will be described.

[0092] 6 is a timing chart showing an example of the operation of the distance measuring device according to the first embodiment. The horizontal axis represents time, and the vertical axis represents the signal level (intensity) of the irradiated light, the signal level (intensity) of the reflected light, and the gate signal S TRG1 , S TRG2 , and the amount of charge Q stored in the floating diffusion regions FD1, FD2 or the additional capacitances FDL1, FLD2 FD1 , Q FD2 The gate signal S TRG1 , S TRG2are signals applied to the gate electrodes TRG1g and TRG2g shown in FIG. 3 or FIG. 5, respectively.

[0093] First, it is assumed that the light receiving element 1 is in a reset state. The light emitting element 2 emits irradiating light. The frequency of the irradiating light is Fmod. The irradiating light is reflected by the object M and received by the light receiving element 1. The frequency of the reflected light is the same as that of the irradiating light, and remains Fmod. Meanwhile, the time Δt it takes for the irradiating light to be emitted, reflected by the object M, and returned as reflected light is the delay time (ToF) of the reflected light relative to the irradiating light. If the delay time Δt is known, the distance from the distance measuring device 100 to the object M can be calculated based on the speed of light c. However, since a phase difference occurs between the irradiating light and the reflected light depending on the delay time Δt (t1 to t2), in iToF, the distance (depth information) D from the distance measuring device 100 to the object M is calculated using the phase difference α between the irradiating light and the reflected light.

[0094] The distance D is expressed by Equation 1. D=(c×Δt) / 2=(c×α) / (4π×Fmod) (Equation 1) If the phase difference α is known, the distance D can be calculated using Equation 1.

[0095] The phase difference α is expressed by the following equation (2). α=arctan((Q 90 -Q 270 ) / (Q0-Q 180 )) (Formula 2)Q θ (θ=0, 90, 180, 270) is the gate signal S TRG1 , S TRG2 The difference in the amount of charge (potential difference) accumulated in the floating diffusion regions FD1 and FD2 or the additional capacitances FDL1 and FDL2 when the phase of the gate signal S TRG1 , S TRG2 The phase difference α is calculated using four pieces of image data obtained when the phase of the image is shifted by a predetermined value (for example, 0 degrees, 90 degrees, 180 degrees, and 270 degrees). The phase difference α is then used to calculate the distance D. This calculation may be performed by the signal processing unit 26 in FIG. 2.

[0096] Referring to Figure 6, θ The calculation of is explained below.

[0097] The gate electrodes TRG1g and TRG2g of the transfer transistors TRG1 and TRG2 are supplied with a gate signal S TRG1 , S TRG2 is applied. Gate signal S TRG1 , S TRG2 is a pulse signal with the same frequency Fmod as the irradiated light. The gate signal S TRG1 and gate signal S TRG2 are opposite phase signals shifted by 180 degrees from each other, and are set to be shifted by a predetermined phase θ (0 degrees, 90 degrees, 180 degrees, or 270 degrees) from the irradiated light. For example, in FIG. 6, the gate signal S TRG1 The phase of the gate signal S is set to be shifted by 90 degrees (θ=90) from the phase of the irradiated light. TRG2 is the gate signal S TRG1 Since it is an inverse phase signal of the gate signal S TRG2 The phase of the gate signal S TRG1 The phases of both are shifted.

[0098] Gate signal S TRG1 , S TRG2 3 and 5 are mutually opposite phase signals, the transfer transistors TRG1 and TRG2 in FIG. 3 and FIG. 5 are alternately turned on. For example, from t0 to t3, the gate signal S TRG1 is at a high level, the transfer transistor TRG1 is in a conductive state. TRG2 is at a low level, the transfer transistor TRG2 is in a non-conductive state. At this time, the charge qa generated in the photodiode PD is transferred to the floating diffusion region FD1 and the additional capacitance FDL1 via the transfer transistor TRG1. On the other hand, the charge qa is not transferred to the floating diffusion region FD2 and the additional capacitance FDL2. The amount of charge in the floating diffusion region FD1 and the additional capacitance FDL1 is Q FD1 Then, the charge Q FD1changes (decreases) by the amount of charge qa. On the other hand, the charge is not transferred to the floating diffusion region FD2 and the additional capacitance FDL2. Therefore, the charge amount of the floating diffusion region FD2 and the additional capacitance FDL2 is FD2 Then, the charge Q FD2 does not change.

[0099] Next, between t3 and t4, the gate signal S TRG2 becomes high level, and the transfer transistor TRG2 becomes conductive. On the other hand, the gate signal S TRG1 becomes low level, and the transfer transistor TRG1 becomes non-conductive. At this time, the charge qb generated in the photodiode PD is transferred to the floating diffusion region FD2 and the additional capacitance FDL2 via the transfer transistor TRG2. On the other hand, the charge qb is not transferred to the floating diffusion region FD1 and the additional capacitance FDL1. Therefore, the charge amount Q FD2 changes (decreases) by the amount of charge qb. On the other hand, the charge is not transferred to the floating diffusion region FD1 and the additional capacitance FDL1. Therefore, the charge amount Q FD1 does not change.

[0100] The operation of the light receiving element 1 from t4 to t5 and t6 to t7 is the same as the operation of the light receiving element 1 from t0 to t3. Moreover, the operation of the light receiving element 1 from t5 to t6 and t7 to t8 is the same as the operation of the light receiving element 1 from t3 to t4. In this way, the transfer transistors TRG1 and TRG2 alternate between a conductive state and a non-conductive state cyclically. As a result, the charge qa generated in the photodiode PD is gradually accumulated (integrated) in the floating diffusion region FD1 and the additional capacitance FDL1, and the charge qb generated in the photodiode PD is gradually accumulated (integrated) in the floating diffusion region FD2 and the additional capacitance FDL2. By dividing the charges qa and qb generated in the photodiode PD based on the frequency Fmod of the irradiated light and the reflected light, the charge amount difference Q according to the phase difference α of the reflected light relative to the irradiated light is 90 The charge difference Q 90 becomes sufficiently large, the light receiving element 1 outputs the potentials of the floating diffusion regions FD1 and FD2 via the vertical signal lines 29A and 29B in FIG.

[0101] The above light receiving process is performed for each of θ=0, 90, 180, and 270, and the charge differences Q0 and Q 90 , Q 180 , Q 270 This detects the gate signal S TRG1 , S TRG2 The four image data obtained when the phase of 90 , Q 180 , Q 270 The signal processing unit 26 converts these four image data (Q0, Q 90 , Q 180 , Q 270 ) to calculate the phase difference α from Equation 2. Furthermore, the signal processing unit 26 calculates the distance D from Equation 1 using the phase difference α.

[0102] In this way, the distance measuring device 100 according to the present disclosure obtains the distance D (depth information) using the iToF method.

[0103] As described above, the light receiving element 1 according to this embodiment has a back-illuminated structure in which the wiring structure is provided on the front surface F1 of the semiconductor layer 51 and the on-chip lens 47 is provided on the back surface F2. Therefore, incident light is not blocked by the wirings M11 to M42, Mbias, etc., but reaches the photodiode PD without being significantly attenuated via the highly transmittant on-chip lens 47 and the semiconductor layer 51. This increases the amount of light photoelectrically converted in the semiconductor layer 51, thereby improving the quantum efficiency (Qe), i.e., the sensitivity of the pixel 10.

[0104] Furthermore, according to this embodiment, the waveguide 55 is provided from the back surface F2 of the semiconductor layer 51 toward the photodiode PD on the front surface F1 side. The waveguide 55 reflects at least a portion of incident light at the interface with the semiconductor layer 51 and guides the incident light to the photodiode PD. This can improve the quantum efficiency (sensitivity) of the light-receiving element 1 according to this embodiment. Since the waveguide 55 reflects incident light at the interface with the semiconductor layer 51, it is preferable that the refractive index of the waveguide 55 is higher than the refractive index of the semiconductor layer 51. This can further improve the sensitivity of the light-receiving element 1.

[0105] Furthermore, according to this embodiment, the photodiode PD is not formed from an impurity diffusion layer in the semiconductor layer 51 (for example, a silicon substrate), but is formed from a material different from the semiconductor layer 51 that is in contact with the back surface F2 of the semiconductor layer 51. By using a material (for example, germanium, InGaAs, CIGS, or Qdot) that has a higher photoelectric conversion efficiency than silicon as the photodiode PD, the quantum efficiency (sensitivity) of the light receiving element 1 can be further improved.

[0106] Furthermore, since the photodiode PD is provided separately from the semiconductor layer 51, there is no need to thicken the semiconductor layer 51 in order to improve quantum efficiency. Because the semiconductor layer 51 can be made thin, there is no need to form the inter-pixel isolation portion 61 deep, making it easier to form the inter-pixel isolation portion 61. Furthermore, even if the inter-pixel isolation portion 61 is relatively shallow, it is possible to efficiently suppress leakage of incident light to adjacent pixels and effectively suppress crosstalk. This allows for an improvement in SNR and resolution.

[0107] Furthermore, when the semiconductor layer 51 is made thinner, the thickness of the waveguide 55 is also reduced, and the path of the incident light within the waveguide 55 is shortened. This reduces the amount of light leaking from the waveguide 55, allowing the waveguide 55 to guide even more incident light to the photodiode PD. As a result, the quantum efficiency of the light-receiving element 1 can be further improved.

[0108] (Second embodiment) FIG. 7 is a cross-sectional view showing an example of the configuration of a pixel 10 according to the second embodiment. The light-receiving element 1 according to the second embodiment further includes a metal layer 56 provided on a side surface of the waveguide 55. The metal layer 56 may be made of any light-reflective metal material, such as tungsten (W), aluminum (Al), or copper (Cu). Even if the refractive index of the waveguide 55 is equal to or lower than that of the semiconductor layer 51, the metal layer 56 reflects incident light within the waveguide 55, allowing the waveguide 55 to guide the incident light to the photodiode PD. Thus, the provision of the metal layer 56 can increase the quantum efficiency of the light-receiving element 1 even if the refractive index of the waveguide 55 is low. Other configurations of the second embodiment may be similar to those of the first embodiment. As a result, the second embodiment can also achieve the effects of the first embodiment.

[0109] (Third embodiment) 8 is a cross-sectional view showing an example of the configuration of a pixel 10 according to the third embodiment. According to the third embodiment, the gate electrodes TGR1g and TGR2g are embedded in the semiconductor layer 51 from the surface F1, forming a vertical gate structure. This allows the transfer transistors TRG1 and TRG2 to be turned on even at a low gate voltage, further increasing the charge transfer speed.

[0110] Furthermore, since the gate electrodes TGR1g and TGR2g are provided between the impurity layer 52 or the photodiode PD and the floating diffusion regions FD1 and FD2, it is possible to prevent incident light from directly entering the floating diffusion regions FD1 and FD2. This makes it possible to reduce PLS (Parasitic Light Sensitivity). The other configurations of the third embodiment may be the same as the corresponding configurations of the first embodiment. As a result, the third embodiment can also obtain the effects of the first embodiment.

[0111] (Fourth embodiment) FIG. 9 is a cross-sectional view showing a configuration example of a pixel 10 according to the fourth embodiment. The pixel 10 according to the fourth embodiment further includes a mixed layer 66 provided between the photodiode PD and the semiconductor layer 51, the mixed layer 66 being a mixture of the material of the photodiode PD and the material of the semiconductor layer 51. For example, if the semiconductor layer 51 is made of silicon and the photodiode PD is made of germanium, the mixed layer 66 is a SiGe layer. Thus, even if the mixed layer 66 is provided between the photodiode PD and the semiconductor layer 51, the effects of the present disclosure are not lost. According to the fourth embodiment, when a SiGe layer is provided as the mixed layer 66, the band gap between the photodiode PD and the semiconductor layer 51 can be continuously changed by controlling the addition ratio of germanium (Ge). Other configurations of the fourth embodiment may be similar to those of the first embodiment. As a result, the fourth embodiment can also achieve the effects of the first embodiment.

[0112] (Fifth embodiment) 10 is a cross-sectional view showing an example of the configuration of a pixel 10 according to the fifth embodiment. In the pixel 10 according to the fifth embodiment, the upper part of the photodiode PD is buried in the impurity layer 52 from the surface F1 of the semiconductor layer 51. Since the upper part of the photodiode PD is buried in the impurity layer 52, charge can be easily taken from the photodiode PD into the impurity layer 52. This further increases the charge transfer speed.

[0113] (Sixth embodiment) 11 is a cross-sectional view showing an example of the configuration of a pixel 10 according to the sixth embodiment. The pixel 10 according to the sixth embodiment further includes an additional semiconductor layer 151 and an additional waveguide 155 provided between the on-chip lens 47 or the planarization film 46 and the back surface F2 of the semiconductor layer 51. An anti-reflection film 143 is provided between the waveguide 155 and the waveguide 55. A light-shielding film 145 is provided between the semiconductor layer 151 and the semiconductor layer 51.

[0114] The semiconductor layer 151 and the waveguide 155 may be made of the same material as the semiconductor layer 51 and the waveguide 55. The antireflection film 143 and the light-shielding film 145 may be made of the same material as the antireflection film 43 and the light-shielding film 45, respectively.

[0115] The semiconductor layer 151 has a surface F3 facing the back surface F2 of the semiconductor layer 51 and a surface F opposite to the surface F3. The antireflection film 143 and the light-shielding film 145 are provided between the back surface F2 of the semiconductor layer 51 and the surface F3 of the semiconductor layer 151. The antireflection film 43 and the light-shielding film 45 are provided on the surface F4 of the semiconductor layer 151.

[0116] The waveguide 155 has an end face E4 on the face F4 side that is approximately the same size as or larger than the opening OP, and an end face E3 on the face F3 side that is approximately the same size as or slightly smaller than the end face E2 on the back face F2 side of the waveguide 55. The area of the end face E3 of the waveguide 155 is smaller than the area of the end face E4 of the waveguide 155. Therefore, the waveguide 155 extends from the face F4 of the semiconductor layer 151 toward the face F3 side, gradually tapering. The side faces of the waveguide 155 are inclined from the direction perpendicular to the faces F3, F4, and the end faces E3 and E4. That is, the side faces of the waveguide 155 between the end faces E4 and E3 have a tapered shape. The waveguide 155 reflects at least a portion of incident light at its side face, i.e., at the interface with the semiconductor layer 151, and guides the incident light to the waveguide 55. This allows the waveguide 155 to guide incident light from the relatively large opening OP to a smaller end face on the rear surface F2 side of the waveguide 55. This allows the waveguide 155 to guide the incident light that has passed through the opening OP to the waveguide 55 without causing much leakage.

[0117] On the other hand, the waveguide 55 extends so as to become gradually thicker from the back surface F2 of the semiconductor layer 51 toward the photodiode PD on the front surface F1 side. The area of the end face E1 of the waveguide 55 on the front surface F1 side is larger than the area of the end face E2 of the waveguide 55 on the back surface F2 side. The waveguide 55 is provided up to the vicinity of the surface of the impurity layer 52, but does not reach the photodiode PD.

[0118] The waveguide 55 reflects at least a part of the incident light at the interface with the semiconductor layer 51, and guides the incident light to the photodiode PD.

[0119] Waveguide 55 has an area at end face E2 equal to or greater than end face E3 of waveguide 155, and an area at front face F1 that is approximately equal to or smaller than photodiode PD. Waveguide 55 is formed so as to gradually become wider from back face F2 to front face F1, and has a tapered shape on the side face between front face F1 and back face F2. This allows waveguide 55 to sufficiently irradiate photodiode PD with incident light from the relatively small end face.

[0120] As described above, the waveguides 55 and 155 are configured in an hourglass shape. By enlarging the opening OP of the waveguide 155, a large amount of incident light can be guided into the pixel 10. The waveguide 55 guides the incident light guided by the waveguide 155 into an internal region surrounded by the metal film 145 and the inter-pixel separator 61. The metal film 145 is made of a metal material such as tungsten (W), aluminum (Al), or copper (Cu). The incident light is repeatedly reflected until it is photoelectrically converted within the internal region surrounded by the metal film 145 and the inter-pixel separator 61. Here, by reducing the opening area of the waveguide 55 at the end face E2, the probability that incident light introduced into the internal region will exit the pixel 10 from the end face E2 without undergoing photoelectric conversion can be reduced. Therefore, the incident light can be confined within the internal region while maintaining the opening OP of the waveguide 155 large. That is, by forming the waveguides 55 and 155 into an hourglass shape with a narrowed main section, it is possible to take in a large amount of incident light and perform sufficient photoelectric conversion. As a result, it is possible to increase the quantum efficiency. The other configurations of the sixth embodiment may be the same as the corresponding configurations of the first embodiment.

[0121] Seventh embodiment FIG. 12 is a cross-sectional view showing an example of the configuration of a light receiving element 1 according to the seventh embodiment. FIG. 13 is a schematic diagram showing an example of the configuration of a light receiving element 1 according to the seventh embodiment. The light receiving element 1 according to the seventh embodiment includes a semiconductor chip C1 for pixels 10 and a semiconductor chip C2 for other peripheral circuits 20. The semiconductor chip C1 has, for example, a pixel array in which a plurality of pixels 10 are arranged. The semiconductor chip C2 may be, for example, a controller for the pixels 10 and has a CMOS (Complementary Metal Oxide Semiconductor) logic circuit 13 and the like provided on a semiconductor substrate. The semiconductor chips C1 and C2 have a stacked structure, and their wiring is directly bonded (Cu-Cu bonded) to function as a single device (module). In this way, the light receiving element 1 may be a module in which a plurality of semiconductor chips are stacked. This allows the layout area of the light receiving element 1 to be reduced.

[0122] (Eighth embodiment) FIG. 14 is a cross-sectional view showing an example of the configuration of a light receiving element 1 according to the eighth embodiment. FIG. 15 is a plan view showing an example of the configuration of a light receiving element 1 according to the eighth embodiment. The light receiving element 1 according to the eighth embodiment has pixels 10 and 11 arranged adjacent to each other. The pixel 10 is a pixel according to the present disclosure, for example, a pixel using germanium as a photodiode PD and detecting short-wave infrared light (SWIR). The pixel 11 is a pixel detecting near-infrared light (NIR (Near Intra Red)) in a photodiode PD provided in a semiconductor layer 51 (for example, a silicon substrate). In this way, by arranging the pixels 10 and 11 that detect different light sources alternately in parallel, the light receiving element 1 can detect both SWIR and NIR. In other words, the range of wavelengths detected by the light receiving element 1 can be widened. Note that although two pixels 10 and 11 are arranged in FIG. 15, three or more of each may be arranged.

[0123] (Ninth embodiment) FIG. 16 is a cross-sectional view showing a configuration example of a light-receiving element 1 according to the ninth embodiment. The light-receiving element 1 according to the ninth embodiment includes, as an example of a first voltage application unit, a first impurity layer TAP1 adjacent to the floating diffusion region FD1 on the surface F1 and having an opposite conductivity type to the floating diffusion region FD1. The light-receiving element 1 also includes, as an example of a second voltage application unit, a second impurity layer TAP2 adjacent to the floating diffusion region FD2 on the surface F1 and having an opposite conductivity type to the floating diffusion region FD2. For example, if the floating diffusion regions FD1 and FD2 are concentrated N+-type impurity layers, the first and second impurity layers TAP1 and TAP2 are concentrated P+-type impurity layers. In this case, a wiring M41 provided on the surface F1 side is electrically connected to the first impurity layer TAP1. A wiring M42 provided on the surface F1 side is electrically connected to the second impurity layer TAP2.

[0124] The vertical drive unit 22 alternately switches the voltage of the wirings M41 and M42, thereby periodically switching the direction of the current flowing between the first impurity layer TAP1 and the second impurity layer TAP2. This allows the charge generated in the photodiode PD to be periodically distributed alternately to the floating diffusion regions FD1 and FD2. As a result, the distance measuring device 100 can perform Q-detection in the iToF system, as in the above embodiment. θ (θ=0, 90, 180, 270) can be detected and the distance D can be calculated.

[0125] (Tenth embodiment) FIG. 17 is a cross-sectional view showing an example configuration of a pixel 10 according to a tenth embodiment. A wiring Mbias and a via Vbias are connected to the photodiode PD. A bias voltage is applied to the photodiode PD via the wiring Mbias and the via Vbias. As a result, charges photoelectrically converted in the photodiode PD are easily captured by the impurity layer 52 and quickly transferred to the floating diffusion regions FD1 and FD2 via the transfer transistors TRG1 and TRG2. In other words, this embodiment can increase the transfer speed of charges from the photodiode PD to the floating diffusion regions FD1 and FD2.

[0126] (Eleventh embodiment) 18 is a cross-sectional view showing an example of the configuration of a pixel 10 according to the eleventh embodiment. According to the eleventh embodiment, the photodiode PD has an area smaller than the opening OP and the impurity layer 52 when viewed from above the back surface F2 of the semiconductor layer 51. This reduces the contact area between the photodiode PD and the semiconductor layer 51, thereby reducing the dark current.

[0127] The pixel 10 according to the eleventh embodiment further includes a metal layer 65. The metal layer 65 is made of a conductive and light-reflective metal material, such as tungsten (W), aluminum (Al), or copper (Cu). The metal layer 65 covers the periphery of the photodiode PD except for the contact portion between the photodiode PD and the semiconductor layer 51. That is, the metal layer 65 covers the bottom surface and four side surfaces of the photodiode PD except for the top surface, and has a rectangular container-like shape. The metal layer 65 is also provided between the photodiode PD and the via Vbias or the wiring Mbias, and functions as an electrode that electrically connects the photodiode PD and the wiring Mbias.

[0128] The metal layer 65 reflects light incident on the photodiode PD within the photodiode PD, making the optical path within the photodiode PD as long as possible. This increases the quantum efficiency of the photodiode PD. That is, the metal layer 65 has a light confinement effect within the photodiode PD, and can increase the quantum efficiency (sensitivity). In this case, even if the area of the planar layout of the photodiode PD is small, a sufficiently high quantum efficiency can be obtained.

[0129] The metal layer 65 also functions as an electrode for the photodiode PD. Therefore, the bias voltage from the wiring Mbias is applied to the photodiode PD from the entire bottom and side surfaces of the photodiode PD via the metal layer 65. This allows the charge of the photodiode PD to be more easily taken into the impurity layer 52, further increasing the charge transfer speed.

[0130] Other configurations of the second embodiment may be similar to the corresponding configurations of the first embodiment. Therefore, the second embodiment further includes the configurations of the first embodiment.

[0131] Two or more of the first to eleventh embodiments may be combined with each other. For example, the metal layer 56 of the second embodiment may be applied to any of the third to eleventh embodiments. The metal layer 56 may be provided in either or both of the waveguides 55 and 155 in FIG. 11. Furthermore, for example, the first and second impurity layers 52 of the ninth embodiment may be applied to any of the first to eighth, tenth, and eleventh embodiments.

[0132] Next, a specific example of a planar layout of the pixel 10 according to the present disclosure will be described.

[0133] Fig. 19 is a plan view showing an example of the layout of a pixel 10 according to the present disclosure. In Fig. 19, one photodiode PD is provided in the center of the impurity layer 52. A via Vbias is provided in the center of the photodiode PD.

[0134] FIG. 20 is a plan view showing another example of the layout of pixel 10 according to the present disclosure. In FIG. 20, a plurality of photodiodes PD are provided in a divided manner in the center of impurity layer 52. A via Vbias is provided in the center of each photodiode PD. Therefore, the same number of vias Vbias as the number of photodiodes PD are provided. In FIG. 20, the photodiode PD is divided into four, but it may be divided into three or less, or five or more.

[0135] The width of the slits between the photodiodes PD is preferably narrower than the wavelength of the irradiated light, which is expected to produce a resonance effect and promote photoelectric conversion by optimizing the slit width for the wavelength.

[0136] <Example of electronic device configuration> The distance measuring device 100 can be applied to distance measuring devices, and also to various electronic devices such as imaging devices with distance measuring functions, such as digital still cameras and digital video cameras, and smartphones with distance measuring functions.

[0137] FIG. 21 is a block diagram showing an example configuration of a smartphone as an electronic device to which the present technology is applied.

[0138] 21, the smartphone 601 is configured by connecting a ranging module 602, an imaging device 603, a display 604, a speaker 605, a microphone 606, a communication module 607, a sensor unit 608, a touch panel 609, and a control unit 610 via a bus 611. In addition, the control unit 610 has functions as an application processing unit 621 and an operation system processing unit 622 by the CPU executing a program.

[0139] The ranging device 100 may be applied to the ranging module 602. For example, the ranging module 602 is disposed on the front surface of a smartphone 601, and by performing ranging on the user of the smartphone 601, the ranging module 602 can output depth values of the surface shapes of the user's face, hands, fingers, etc. as ranging results.

[0140] The imaging device 603 is arranged on the front side of the smartphone 601, and captures an image of the user of the smartphone 601 by capturing an image of the user as a subject. Although not shown, the smartphone 601 may also have a configuration in which an imaging device 603 is arranged on the back side.

[0141] The display 604 displays an operation screen for performing processing by the application processing unit 621 and the operation system processing unit 622, images captured by the imaging device 603, etc. The speaker 605 and the microphone 606 output the voice of the other party and pick up the voice of the user when making a call using the smartphone 601, for example.

[0142] The communication module 607 performs network communication via communication networks such as the Internet, public telephone network, wide area communication networks for wireless mobile devices such as so-called 4G lines and 5G lines, WAN (Wide Area Network) and LAN (Local Area Network), and short-range wireless communication such as Bluetooth (registered trademark) and NFC (Near Field Communication). The sensor unit 608 senses speed, acceleration, proximity, etc., and the touch panel 609 acquires touch operations by the user on the operation screen displayed on the display 604.

[0143] The application processing unit 621 performs processing for providing various services via the smartphone 601. For example, the application processing unit 621 can perform processing for creating a computer graphics face that virtually reproduces the user's facial expression based on the depth value supplied from the distance measurement module 602, and displaying the face on the display 604. Furthermore, the application processing unit 621 can perform processing for creating, for example, three-dimensional shape data of any three-dimensional object based on the depth value supplied from the distance measurement module 602.

[0144] The operation system processing unit 622 performs processing for realizing the basic functions and operations of the smartphone 601. For example, the operation system processing unit 622 can perform processing for authenticating the user's face and unlocking the smartphone 601 based on the depth value supplied from the distance measurement module 602. The operation system processing unit 622 can also perform processing for recognizing the user's gestures based on the depth value supplied from the distance measurement module 602 and inputting various operations in accordance with the gestures.

[0145] In the smartphone 601 configured in this manner, by applying the above-mentioned distance measuring device 100 as the distance measuring module 602, it is possible to perform processes such as measuring and displaying the distance to a specified object, and creating and displaying three-dimensional shape data of the specified object.

[0146] <Application to a moving object> The technology according to the present disclosure (the present technology) 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 moving body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0147] FIG. 22 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.

[0148] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 22, 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.

[0149] 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, a braking device for generating a braking force of the vehicle, etc.

[0150] 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 may 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.

[0151] 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 includes the distance measuring device 100, and may perform object detection processing or distance detection processing for a person, a vehicle, an obstacle, a sign, or text on a road surface, etc., based on the received images.

[0152] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according 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.

[0153] 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.

[0154] 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 drivetrain 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, or vehicle lane departure warning.

[0155] 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.

[0156] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information about the outside of 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 for the purpose of preventing glare, such as switching from high beams to low beams.

[0157] 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 information to vehicle occupants or the outside of the vehicle. In the example of Fig. 22, 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 on-board display and a head-up display.

[0158] FIG. 23 is a diagram showing an example of the installation position of the imaging unit 12031.

[0159] In FIG. 23, a vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as the imaging unit 12031.

[0160] 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 at the front nose and the imaging unit 12105 provided at 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 at the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The forward images acquired by the imaging units 12101 and 12105 are mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0161] 23 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, a bird's-eye view image of the vehicle 12100 viewed from above can be obtained.

[0162] At least one of the imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera made up of multiple imaging elements, or may be an imaging element having pixels for phase difference detection.

[0163] For example, 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) based on the distance information obtained from the imaging units 12101 to 12104, 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 (for example, 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 automatic driving, which runs autonomously without relying on driver operation.

[0164] 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 the collision risk, which indicates the degree of 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 drivetrain control unit 12010.

[0165] 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 or not a pedestrian is present in the images captured by the image capturing units 12101 to 12104. The pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104, which are infrared cameras, and then performing pattern matching on a series of feature points that indicate the outline of an object to determine whether or not 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.

[0166] The present technology is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present technology. (1) a semiconductor layer having a first surface and a second surface opposite the first surface; a lens provided on the second surface side; first and second charge accumulation units provided in the semiconductor layer on the first surface side; a photoelectric conversion section in contact with the semiconductor layer on the first surface side and made of a material different from that of the semiconductor layer; first and second voltage application units that apply a voltage to the semiconductor layer between the first and second charge accumulation units and the photoelectric conversion unit; a waveguide section extending from the second surface to the photoelectric conversion section within the semiconductor layer and made of a material different from that of the semiconductor layer; (2) The distance measuring device according to (1), wherein the area of the end face of the waveguide on the first surface side is smaller than the area of the end face of the waveguide on the second surface side. (3) The waveguide section has an area at the end face on the second surface side equal to or greater than the opening that passes incident light from the lens to the semiconductor layer, and an area at the end face on the first surface side equal to or less than the photoelectric conversion section, and the side surface between the first surface and the second surface is inclined from the direction perpendicular to the first surface or the second surface. (4) The distance measuring device according to any one of (1) to (3), wherein the refractive index of the waveguide is higher than the refractive index of the semiconductor layer. (5) The distance measuring device according to claim 4, wherein the refractive index of the waveguide is lower than the refractive index of the lens. A metal provided on the side of the waveguide layer The distance measuring device according to any one of (1) to (5), further comprising: (7) The semiconductor layer is made of silicon, The photoelectric conversion section uses germanium, InGaAs, CIGS, or Qdot, The distance measuring device according to any one of (1) to (6), wherein the waveguide section is made of a resin material. (8) A distance measuring device described in any one of (1) to (7), further comprising a mixed layer provided between the photoelectric conversion unit and the semiconductor layer, in which the material of the photoelectric conversion unit and the material of the semiconductor layer are mixed. (9) Further, an additional waveguide is provided on the second surface side of the waveguide, an area of a first end face of the waveguide on the first surface side is larger than an area of a second end face of the waveguide on the second surface side; (10) The distance measuring device according to (1), wherein an area of a third end face of the additional waveguide that faces the second end face of the waveguide is smaller than an area of a fourth end face of the additional waveguide that is located on the opposite side from the third end face. the first voltage application unit is a first gate electrode provided on the first surface between the first charge accumulation unit and the photoelectric conversion unit and insulated from the semiconductor layer; the second voltage application unit is a second gate electrode provided on the first surface between the second charge accumulation unit and the photoelectric conversion unit and insulated from the semiconductor layer, a second wiring provided on the first surface side and connected to the first voltage application unit; The distance measuring device according to any one of (1) to (9), further comprising a third wiring provided on the first surface side and connected to the second voltage application unit. (11) The distance measuring device according to (10), wherein the first and second voltage application units are provided on the first surface of the semiconductor layer via an insulating film. (12) The distance measuring device according to (10), wherein the first and second voltage application units are embedded into the semiconductor layer from the first surface of the semiconductor layer. (13) the first voltage application section is a first impurity layer adjacent to the first charge accumulation section on the first surface and having a conductivity type different from that of the first charge accumulation section, the second voltage application section is a second impurity layer adjacent to the second charge accumulation section on the first surface and having a different conductivity type from the second charge accumulation section, a second wiring provided on the first surface side and connected to the first voltage application unit; The distance measuring device according to any one of (1) to (9), further comprising a third wiring provided on the first surface side and connected to the second voltage application unit. (14) A distance measuring device described in any one of (1) to (13), wherein the photoelectric conversion unit, when viewed from above the second surface of the semiconductor layer, is smaller than an opening that passes incident light from the lens to the semiconductor layer. (15) A distance measuring device described in any one of (1) to (14), further comprising a metal layer made of a conductive and light-reflecting material and covering the periphery of the photoelectric conversion unit except for the contact area between the photoelectric conversion unit and the semiconductor layer.

[0167] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, the effects described in this specification are merely examples and are not intended to be limiting, and other effects may also be obtained. [Explanation of symbols]

[0168] 100 Range finding device, 1 Light receiving element, 10 Pixel, PD Photodiode, TRG1, TRG2 Transfer transistor, FD1, FD2 Floating diffusion region, FDL1, FDL2 Additional capacitance, 51 Semiconductor layer, 47 On-chip lens, 43 Anti-reflection film, 45 Light shielding film, 61 Inter-pixel isolation section, 52 Impurity layer, V1 to V4, Vbias via, M1 to M4, Mbias wiring, 65 Metal layer, 55 Waveguide section

Claims

1. a semiconductor layer having a first surface and a second surface opposite the first surface; a lens provided on the second surface side; first and second charge accumulation units provided in the semiconductor layer on the first surface side; a photoelectric conversion portion in contact with the semiconductor layer on the first surface side and made of a material different from that of the semiconductor layer; first and second voltage application units that apply a voltage to the semiconductor layer between the first and second charge accumulation units and the photoelectric conversion unit; a waveguide portion extending from the second surface to the photoelectric conversion portion within the semiconductor layer and made of a material different from that of the semiconductor layer, A distance measuring device, wherein the refractive index of the waveguide is higher than the refractive index of the semiconductor layer and lower than the refractive index of the lens.

2. The distance measuring device according to claim 1 , wherein an area of the end face of the waveguide on the first surface side is smaller than an area of the end face of the waveguide on the second surface side.

3. 2. The distance measuring device of claim 1, wherein the waveguide section has an area at its end face on the second surface side equal to or greater than an opening that passes incident light from the lens to the semiconductor layer, and an area at its end face on the first surface side equal to or less than an area of the photoelectric conversion section, and a side surface between the first surface and the second surface is inclined from a direction perpendicular to the first surface or the second surface.

4. The distance measuring device according to claim 1 , further comprising a metal layer provided on a side surface of the waveguide portion.

5. The semiconductor layer is made of silicon, 2. The distance measuring device according to claim 1, wherein the photoelectric conversion section is made of germanium, InGaAs, copper indium gallium diselenide (CIGS), or quantum dot (Qdot), and the waveguide section is made of a resin material.

6. The distance measuring device according to claim 1 , further comprising a mixed layer provided between the photoelectric conversion section and the semiconductor layer, the mixed layer being a mixture of a material of the photoelectric conversion section and a material of the semiconductor layer.

7. Further, an additional waveguide is provided on the second surface side of the waveguide, an area of a first end face of the waveguide on the first surface side is larger than an area of a second end face of the waveguide on the second surface side; 2. The distance measuring device according to claim 1, wherein an area of a third end face of the additional waveguide that faces the second end face of the waveguide is smaller than an area of a fourth end face of the additional waveguide that is located on the opposite side from the third end face.

8. the first voltage application unit is a first gate electrode provided on the first surface between the first charge accumulation unit and the photoelectric conversion unit and insulated from the semiconductor layer; the second voltage application unit is a second gate electrode provided on the first surface between the second charge accumulation unit and the photoelectric conversion unit and insulated from the semiconductor layer, a second wiring provided on the first surface side and connected to the first voltage application unit; The distance measuring device according to claim 1 , further comprising a third wiring provided on the first surface side and connected to the second voltage application unit.

9. The distance measuring device according to claim 8 , wherein the first and second voltage application sections are provided on the first surface of the semiconductor layer via an insulating film.

10. 9. The distance measuring device according to claim 8, wherein the first and second voltage application sections are embedded into the semiconductor layer from the first surface of the semiconductor layer.

11. the first voltage application section is a first impurity layer adjacent to the first charge accumulation section on the first surface and having a conductivity type different from that of the first charge accumulation section, the second voltage application section is a second impurity layer adjacent to the second charge accumulation section on the first surface and having a conductivity type different from that of the second charge accumulation section, a second wiring provided on the first surface side and connected to the first voltage application unit; The distance measuring device according to claim 1 , further comprising a third wiring provided on the first surface side and connected to the second voltage application unit.

12. The distance measuring device according to claim 1 , wherein the photoelectric conversion portion is smaller than an opening that passes incident light from the lens to the semiconductor layer when viewed from above the second surface of the semiconductor layer.

13. 2. The distance measuring device according to claim 1, further comprising a metal layer made of a conductive and light-reflecting material, covering the periphery of the photoelectric conversion unit except for a contact portion between the photoelectric conversion unit and the semiconductor layer.

14. a semiconductor layer having a first surface and a second surface opposite the first surface; a lens provided on the second surface side; first and second charge accumulation units provided in the semiconductor layer on the first surface side; a photoelectric conversion portion in contact with the semiconductor layer on the first surface side and made of a material different from that of the semiconductor layer; first and second voltage application units that apply a voltage to the semiconductor layer between the first and second charge accumulation units and the photoelectric conversion unit; a waveguide portion extending from the second surface to the photoelectric conversion portion within the semiconductor layer and made of a material different from that of the semiconductor layer; an additional waveguide portion provided on the waveguide portion on the second surface side, an area of a first end face of the waveguide on the first surface side is larger than an area of a second end face of the waveguide on the second surface side; a third end face of the additional waveguide that faces the second end face of the waveguide has an area smaller than an area of a fourth end face of the additional waveguide that is located on the opposite side from the third end face.

Images