Light detection device, imaging device, and electronic apparatus

Abstract

The present disclosure pertains to a light detection device, an imaging device, and an electronic apparatus, which are capable of adjusting differences in threshold voltage between pixel transistors without any variations. According to the present invention, materials for the gate electrode of an amplification transistor and the gate electrode of a selection transistor are selected according to the work functions of the respective materials such that the threshold voltage of the amplification transistor is higher than the threshold voltage of the selection transistor. As a result, the impurity concentrations of the channel regions of the amplification transistor and the selection transistor can be set to about 1017cm-3 or less, and variations in the threshold voltages can be reduced. The present disclosure is applicable to an imaging device.

Description

Photodetector, imaging device, and electronic device

[0001] The present disclosure relates to a photodetector, an imaging device, and an electronic device, and more particularly to a photodetector, an imaging device, and an electronic device that are capable of adjusting the difference in threshold voltage between pixel transistors without variation.

[0002] Among solid-state imaging devices, complementary metal oxide semiconductor (CMOS) image sensors (CIS) generally use a source follower circuit for signal readout.

[0003] The source follower circuit uses pixel transistors, including an amplifier transistor, a select transistor, and a reset transistor. Each pixel transistor has its own required operating range depending on the pixel's operating conditions, and each has a different threshold voltage, which must be adjusted. Conventionally, this threshold voltage adjustment has been performed by implanting impurities into the channel region directly below the gate electrode.

[0004] For example, when the pixel transistor is an NMOS, it is known that the threshold voltage can be lowered by adding n-type impurities (phosphorus or arsenic), and conversely, the threshold voltage can be raised by adding p-type impurities (boron). Therefore, using lithography and ion implantation, the threshold voltage was changed and adjusted by implanting impurities of different elements or different concentrations into the channel region of each pixel transistor.

[0005] However, it is generally known that a high impurity concentration in the channel region of a transistor increases the variation in threshold voltage. That is, the number of atoms implanted in the channel region follows a random distribution, so the impurity concentration in the channel region will vary in principle. This variation is known to be proportional to the square root of the impurity concentration, and it is expected that the variation can be reduced by reducing the impurity concentration (see Non-Patent Document 1).

[0006] Therefore, a technique has been proposed in which the atomic weight of the impurity and the channel area are adjusted to suppress the generation of interstitial silicon and reduce the variation in threshold voltage (see Patent Document 1).

[0007] Toshiro Hiramoto, Kiyoshi Takeuchi, Akio Nishida, "Characteristic Variation Due to Scaling of MOS Transistors", IEICE Vol.92, No.6 2009

[0008] JP 2011-82461 A

[0009] However, in the technique described in Patent Document 1, since impurities are used in the channel portion, there is a risk that the influence of variations in threshold voltage due to impurity concentration cannot be completely suppressed.

[0010] The present disclosure has been made in consideration of such circumstances, and in particular, reduces variations in threshold voltage by adjusting the threshold voltage using the work function of the gate electrode without implanting impurities into the channel portion of the pixel transistor.

[0011] According to one aspect of the present disclosure, there is provided a photodetector, an imaging device, and an electronic device, which include a photoelectric conversion unit that performs photoelectric conversion on incident light in accordance with the amount of light and generates charges on a pixel-by-pixel basis, and a plurality of transistors that generate pixel signals on a pixel-by-pixel basis based on the charges, wherein the gate electrode of at least one of the plurality of transistors has a work function different from that of the gate electrodes of the other transistors, and the photodetector, imaging device, and electronic device include the photodetector.

[0012] In one aspect of the present disclosure, a photoelectric conversion unit photoelectrically converts incident light according to the amount of light, generating charges per pixel, and a plurality of transistors generate pixel signals per pixel based on the charges, and at least one of the gate electrodes of the plurality of transistors has a work function different from that of the gate electrodes of the other transistors.

[0013] 16 is a diagram explaining that variations in threshold voltage occur due to implantation of impurities into a channel region. FIG. 17 is a diagram explaining an overview of the present disclosure. FIG. 18 is a diagram explaining a configuration example of a photodetector according to the present disclosure. FIG. 19 is a diagram explaining a circuit configuration of a pixel according to the present disclosure. FIG. 19 is a diagram explaining a physical configuration example of a first embodiment of a pixel according to the present disclosure. FIG. 19 is a diagram explaining a method for forming the amplifier transistor and the selection transistor of FIG. 5. FIG. 19 is a diagram explaining a configuration example of a second embodiment of a pixel according to the present disclosure. FIG. 20 is a diagram explaining a first method for forming the amplifier transistor and the selection transistor of FIG. 7. FIG. 21 is a diagram explaining a second method for forming the amplifier transistor and the selection transistor of FIG. 7. FIG. 21 is a diagram explaining a physical configuration example of a third embodiment of a pixel according to the present disclosure. FIG. 22 is a diagram explaining a physical configuration example of a fourth embodiment of a pixel according to the present disclosure. FIG. 23 is a diagram explaining a physical configuration example of a fifth embodiment of a pixel according to the present disclosure. FIG. 24 is a diagram explaining an effect other than suppression of variations in threshold voltage of pixels according to the present disclosure. FIG. 25 is a diagram explaining an effect other than suppression of variations in threshold voltage of pixels according to the present disclosure. FIG. 26 is a diagram explaining an application example of a photodetector according to the present disclosure. FIG. 27 is a diagram explaining an example of the sensor pixel and readout circuit of FIG. 16. Fig. 1 is a block diagram showing an example of the configuration of an imaging device as an electronic device to which the light detection device of the present disclosure is applied. Fig. 2 is a diagram explaining an example of use of a light detection device to which the technology of the present disclosure is applied. Fig. 3 is a diagram showing an example of the schematic configuration of an endoscopic surgery system. Fig. 4 is a block diagram showing an example of the functional configuration of a camera head and a CCU. Fig. 5 is a block diagram showing an example of the schematic configuration of a vehicle control system. Fig. 6 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit.

[0014] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0015] Hereinafter, embodiments of the present technology will be described in the following order.

[0016] 1. Overview of the present disclosure 2. First embodiment 3. Second embodiment 4. Third embodiment 5. Fourth embodiment 6. Fifth embodiment 7. Effects of a single-layer substrate type photodetector 8. Effects of a multilayer substrate type photodetector 9. Application examples 10. Application examples to electronic devices 11. Use examples of solid-state imaging devices 12. Application examples to endoscopic surgery systems 13. Application examples to moving bodies

[0017] <<1. Overview of the Present Disclosure>> The present disclosure, in particular, reduces variations in threshold voltage by adjusting the work function of a gate electrode without implanting impurities into a channel portion of a pixel transistor. Therefore, first, an overview of the present disclosure will be described.

[0018] A CMOS (Complementary Metal Oxide Semiconductor) image sensor (CIS) generally includes a photodiode PD, a floating diffusion FD, and pixel transistors (including a transfer transistor TRG, a reset transistor RST, an amplification transistor AMP, and a selection transistor SEL).

[0019] At this time, the amplifying transistor and the selecting transistor are connected in series to form a source follower circuit, for example, as shown in the upper part of FIG.

[0020] FIG. 1 is a cross-sectional view showing a state in which an amplifying transistor 21 is formed on the left side of the drawing and a selecting transistor 22 is formed on the right side of the drawing.

[0021] More specifically, n+ regions 34-1 to 34-3 are formed at predetermined intervals in this order from the left in the drawing on the upper part of the silicon substrate 33. A gate electrode (AMP) 31 for the amplifier transistor is formed on the silicon substrate 33 so as to straddle the n+ regions 34-1 and 34-2, and another gate electrode (AMP) 31 for the amplifier transistor is formed so as to straddle the n+ regions 34-2 and 34-3.

[0022] That is, with the configuration shown in the upper part of FIG. 1, the gate electrode 31 functions as the gate electrode of the amplifier transistor 21, and the n+ regions 34-1 and 34-2 function as the source and drain of the amplifier transistor 21.

[0023] Furthermore, the gate electrode 32 functions as the gate electrode of the selection transistor 22 , and the n+ regions 34 - 2 and 34 - 3 function as the source and drain of the selection transistor 22 .

[0024] The amplifier transistor 21 and the selection transistor 22 are electrically connected in series via an n+ region 34-2.

[0025] The amplification transistor 21 and the selection transistor 22 of the CIS having such a configuration must be set to different threshold voltages.

[0026] More specifically, the threshold voltage of the amplification transistor 21 needs to be set higher than the threshold voltage of the selection transistor 22 .

[0027] Therefore, in order to adjust the threshold voltages of the amplifier transistor 21 and the select transistor 22, for example, when the gate electrode 31 of the amplifier transistor 21 and the gate electrode 32 of the select transistor 22 are made of n-type polysilicon (n-poly Si) as shown in FIG. 1, n-type impurities such as phosphorus or arsenic are ion-implanted (Ch. II) into the channel region 35-2 of the select transistor 22, thereby adjusting the threshold voltage of the select transistor 22 to be lower than the threshold voltage of the amplifier transistor 21.

[0028] Furthermore, although not shown, the threshold voltage of the amplifier transistor 21 may be adjusted to be higher than the threshold voltage of the select transistor 22 by ion-implanting p-type impurities such as boron into the channel region 35-1 of the amplifier transistor 21.

[0029] However, it is generally known that a high impurity concentration in the channel region increases the variation in threshold voltage. That is, the number of atoms implanted into the channel region follows a random distribution, so the impurity concentration in the channel region will, in principle, vary. It is known that this variation is proportional to the square root of the impurity concentration, and it is expected that the variation will be reduced by reducing the impurity concentration.

[0030] The lower part of FIG. 1 is a graph showing the relationship between the reciprocal of the square root of the area of ​​the channel region (1 / √LW) and the variation in threshold voltage (σ_Vt) for each ion implantation amount.

[0031] From top to bottom in the figure, the relationship between the reciprocal of the square root of the area of ​​the channel region (1 / √LW) and the variation voltage σ_Vt is shown when the ion implantation dose is the second implantation dose (Ch.II High dose), the first implantation dose (<second implantation dose) (Ch.II Low dose), and 0 (non-doped).

[0032] It is known that the voltage σ_Vt is proportional to the reciprocal of the square root of the area of ​​the channel region (1 / √LW), but Fig. 1 shows that the slope increases with the ion implantation dose. In particular, Fig. 1 shows that the slope increases when the ion implantation dose changes from a first implantation dose (Ch. II Low dose) to a second implantation dose (Ch. II High dose) that is greater than the first implantation dose.

[0033] That is, when an attempt is made to adjust the threshold voltage by implanting ions into the channel region, the threshold voltage varies more as the amount of ions implanted increases.

[0034] Therefore, in the present disclosure, the threshold voltage is adjusted not by ion implantation into the channel region, but by utilizing the work function that differs for each gate electrode material.

[0035] That is, as shown in the upper part of Figure 2, n+ regions 74-1 to 74-3 formed on a silicon substrate 73 form the source-drain of the amplification transistor 61 and the selection transistor 62, and a gate electrode 71 of the amplification transistor 61 and a gate electrode 72 of the selection transistor 62 are formed so as to straddle each of them.

[0036] Here, the gate electrode 71 of the amplification transistor 61 and the gate electrode 72 of the selection transistor 62 are made of materials WF_A and WF_B, respectively, with different work functions, selected so that the threshold voltage of the amplification transistor 61 is higher than the threshold voltage of the selection transistor 62.

[0037] The materials WF_A and WF_B of the gate electrodes of the amplification transistor 61 and the selection transistor 62 may be selected so that the work functions of both are such that the threshold voltage of the amplification transistor 61 is higher than the threshold voltage of the selection transistor 62, and may be any of n-type or p-type polysilicon, a simple metal, an alloy, a metal nitride, and a metal silicide.

[0038] By applying the materials WF_A and WF_B selected in accordance with the work function to the gate electrode 71 of the amplifier transistor 61 and the gate electrode 72 of the select transistor 62, respectively, as shown in FIG. 2, the channel regions of the amplifier transistor 61 and the select transistor 62 have impurity concentrations of approximately the same 10 17 cm -3 Since it is possible to make the concentration of impurities to about 1000 volts or less, it is possible to reduce the variation in threshold voltage caused by the impurity concentration.

[0039] 2. First Embodiment Configuration of Photodetector Fig. 3 is a diagram showing an example of the configuration of a photodetector according to the present disclosure. The photodetector 81 in Fig. 3 includes a pixel region (so-called imaging region) 83 in which pixels 93, each including a plurality of photoelectric conversion elements, are regularly arranged two-dimensionally on a semiconductor substrate 82, for example, a silicon substrate, and a peripheral circuit section.

[0040] Each pixel 93 is composed of a photoelectric conversion element, such as a photodiode, and multiple pixel transistors (so-called MOS transistors). The multiple pixel transistors are composed of, for example, four transistors: a transfer transistor, a reset transistor, an amplification transistor, and a selection transistor. The pixel 93 may also have a shared pixel structure. This shared pixel structure is composed of multiple photodiodes, a floating diffusion region shared by multiple transfer transistors, and one other pixel transistor each sharing the floating diffusion region.

[0041] The peripheral circuit section is made up of a vertical drive circuit 84 , a column signal processing circuit 85 , a horizontal drive circuit 86 , an output circuit 87 , and a control circuit 88 .

[0042] The control circuit 88 receives an input clock and data instructing the operation mode and the like, and outputs data such as internal information of the photodetector device 81. That is, the control circuit 88 generates clock signals and control signals that serve as references for the operations of the vertical drive circuit 84, column signal processing circuit 85, horizontal drive circuit 86, etc., based on a vertical synchronization signal, a horizontal synchronization signal, and a master clock. The control circuit 88 then inputs these signals to the vertical drive circuit 84, column signal processing circuit 85, horizontal drive circuit 86, etc.

[0043] The vertical drive circuit 84 is configured, for example, by a shift register, selects pixel drive wirings 92, supplies pulses for driving pixels to the selected pixel drive wirings, and drives the pixels row by row. That is, the vertical drive circuit 84 selects and scans each pixel 93 in the pixel region 83 row by row in the vertical direction, and supplies pixel signals based on signal charges generated in accordance with the amount of light received in, for example, photodiodes serving as photoelectric conversion elements in each pixel 93 to the column signal processing circuit 85 via vertical signal lines 89.

[0044] The column signal processing circuits 85 are arranged, for example, for each column of pixels 93, and perform signal processing such as noise removal for each pixel column on signals output from one row of pixels 93. That is, the column signal processing circuits 85 perform signal processing such as CDS (Correlated Double Sampling) for removing fixed pattern noise specific to the pixels 93, signal amplification, AD conversion, etc. A horizontal selection switch (not shown) is provided at the output stage of the column signal processing circuit 85 and connected between the output stage and the horizontal signal line 90.

[0045] The horizontal drive circuit 86 is, for example, composed of a shift register, and by sequentially outputting horizontal scanning pulses, selects each of the column signal processing circuits 85 in turn and causes each of the column signal processing circuits 85 to output a pixel signal to the horizontal signal line 90.

[0046] The output circuit 87 processes and outputs signals sequentially supplied from each of the column signal processing circuits 85 via a horizontal signal line 90. For example, the output circuit 87 may perform only buffering, or may perform black level adjustment, column variation correction, various digital signal processing, etc. The input / output terminal 91 exchanges signals with the outside.

[0047] <Example of Circuit Configuration of Photodetector> Next, an example of the circuit configuration of the pixel 93 that constitutes the photodetector 81 will be described with reference to Fig. 4. Fig. 4 is a circuit diagram illustrating an example of the circuit configuration of the pixel 93 of the present disclosure.

[0048] The pixel 93 in Figure 4 includes a photoelectric conversion unit (PD) 121, a transfer transistor (TRG) 122, a charge holding unit (FD) 123, a reset transistor (RST) 124, a power supply (VDD) 125 that supplies power to the pixel 93, an amplification transistor (AMP) 131, and a selection transistor (SEL) 132.

[0049] The anode of the photoelectric conversion unit 121 is grounded, and the cathode is connected to the source of the transfer transistor 122. The drain of the transfer transistor 122 is connected to the source of the reset transistor 124 and the gate of the amplification transistor 131. The other end of the charge holding unit 123 is grounded. The drain of the reset transistor 124 is connected to a power supply 125. The drain of the amplification transistor 131 is connected to the power supply 125, and the source is connected to the drain of the selection transistor 132. The source of the selection transistor 132 is connected to a signal line VSL.

[0050] The photoelectric conversion unit 121 performs photoelectric conversion of incident light and can be configured by a photodiode formed on a semiconductor substrate. The photoelectric conversion unit 121 performs photoelectric conversion of incident light during an exposure period and stores charges generated by the photoelectric conversion.

[0051] The charge holding portion 123 holds the charge generated by the photoelectric conversion portion 121. The charge holding portion 123 can be configured by a floating diffusion region (FD), which is a semiconductor region formed on a semiconductor substrate.

[0052] The transfer transistor 122 transfers electric charges. The transfer transistor 122 transfers electric charges generated by photoelectric conversion in the photoelectric conversion unit 121 to the charge holding unit 123. The transfer transistor 122 transfers electric charges by establishing electrical continuity between the photoelectric conversion unit 121 and the charge holding unit 123. A control signal for the transfer transistor 122 is transmitted by a signal line TRG.

[0053] The reset transistor 124 resets the charge holding portion 123. This reset can be performed by establishing electrical continuity between the charge holding portion 123 and a power supply 125 to drain the charge from the charge holding portion 123. A control signal for the reset transistor 124 is transmitted via a signal line RST.

[0054] The amplifier transistor 131 amplifies the voltage of the charge holding section 123. The gate of the amplifier transistor 131 is connected to the charge holding section 123. Therefore, an image signal having a voltage corresponding to the charge held in the charge holding section 123 is generated at the source of the amplifier transistor 131. Furthermore, by making the selection transistor 132 conductive, this image signal can be output to a signal line VSL. A control signal for the selection transistor 132 is transmitted by a signal line SEL.

[0055] <First Physical Configuration Example of Amplification Transistor and Selection Transistor> Next, with reference to FIG. 5, a first physical configuration example of the amplification transistor and the selection transistor according to the first embodiment of the present disclosure will be described.

[0056] FIG. 5 is a diagram illustrating an example of the physical configuration of the amplification transistor 131 and the selection transistor 132 enclosed by the dotted line in the pixel 93 described with reference to FIG.

[0057] In addition, the amplification transistor 131, the selection transistor 132, the gate electrode 141 of the amplification transistor 131, the gate electrode 142 of the selection transistor 132, the silicon substrate 143, and the n+ regions 144-1 to 144-3 in the left part of Figure 5 correspond to the amplification transistor 61, the selection transistor 62, the gate electrode 71 of the amplification transistor 61, the gate electrode 72 of the selection transistor 62, the silicon substrate 73, and the n+ regions 74-1 to 74-3 in Figure 2, respectively.

[0058] That is, the gate electrode 141 of the amplification transistor 131 and the gate electrode 142 of the selection transistor 132 are made of materials WF_A and WF_B, respectively, having different work functions, selected so that the threshold voltage of the amplification transistor 131 is higher than the threshold voltage of the selection transistor 132.

[0059] The materials WF_A and WF_B of the gate electrodes 141 and 142 of the amplifier transistor 131 and the select transistor 132 are selected so that the threshold voltage of the amplifier transistor 131 is higher than the threshold voltage of the select transistor 132 .

[0060] The materials WF_A and WF_B may be, for example, p-type polysilicon (p-poly) and n-type polysilicon (p-poly), respectively, as shown in the right part of FIG.

[0061] The amplifier transistor 131A and select transistor 132A on the right side of FIG. 5 are composed of a gate electrode 141A of the amplifier transistor 131A, a gate electrode 142A of the select transistor 132A, a silicon substrate 143A, and n+ regions 144A-1 to 144A-3.

[0062] 5 correspond to the amplifier transistor 131 and select transistor 132 in the left part of Fig. 5. That is, the gate electrode 141A of the amplifier transistor 131A, the gate electrode 142A of the select transistor 132A, the silicon substrate 143A, and the n+ regions 144A-1 to 144A-3 correspond to the gate electrode 141 of the amplifier transistor 131, the gate electrode 142 of the select transistor 132, the silicon substrate 143, and the n+ regions 144-1 to 144-3 in the left part of Fig. 5, respectively.

[0063] The right part of FIG. 5 shows an example in which the materials WF_A and WF_B of the gate electrode 141A of the amplification transistor 131A and the gate electrode 142A of the selection transistor 132A are p-type polysilicon (p-poly) and n-type polysilicon (n-poly), respectively.

[0064] That is, the materials WF_A and WF_B of the gate electrode 141A of the amplifier transistor 131A and the gate electrode 142A of the select transistor 132A are selected as p-type polysilicon (p-poly) and n-type polysilicon (n-poly) according to their work functions so that the threshold voltage of the amplifier transistor 131A is higher than the threshold voltage of the select transistor 132A. As a result, the channel regions of the amplifier transistor 131A and the select transistor 132A have approximately the same impurity concentration of 10, as shown by the dotted oval. 17 cm -3Since the concentration can be made to be about 0.1 to 1.0 V or less, it is possible to reduce the variation in threshold voltage caused by the impurity concentration.

[0065] <Method of Forming the Respective Gate Electrodes of the Amplification Transistor and the Selection Transistor in the Right Part of Fig. 5> Next, with reference to Fig. 6, a method of forming the gate electrode 141A of the amplification transistor 131A and the gate electrode 142A of the selection transistor 132A in the right part of Fig. 5 will be described. Note that it is assumed that n+ 143A-1 to 143A-3 have been formed in advance on the silicon substrate 143A, and this is omitted from Fig. 6. Also, Fig. 6 shows cross sections of the first, second, third, and fourth steps, in that order from left to right.

[0066] In the first step, a uniform polysilicon film 151 is deposited on the silicon substrate 143A via a gate oxide film, and then, with the region on the side of the select transistor 132A (not shown in the figure) (right side) masked with resist 151R by photolithography, an area wider than the position of the gate electrode of the amplification transistor 131A is opened, and a p-type dopant made of boron B is injected to form a p-type dopant portion 141A'.

[0067] In the second step, after the resist 151R is removed, the region on the amplification transistor 131A side (left side in the figure) (not shown) is masked with resist 151L by photolithography, and an area wider than the position of the gate electrode 142A of the selection transistor 132A is opened, and an n-type dopant consisting of phosphorus P is injected to form an n-type dopant portion 142A'.

[0068] In the third step, photolithography dry etching is used to process the p-type dopant portion 141A' of the amplification transistor 131A into the shape of the gate electrode 141A, and the n-type dopant portion 142' of the selection transistor 132A into the shape of the gate electrode 142A.

[0069] In the fourth step, the p-type dopant impurity in the p-type dopant portion 141A′ and the n-type dopant impurity in the n-type dopant portion 142A′ are diffused and activated by heat treatment, thereby forming the gate electrode 141A made of a p-type polysilicon electrode of the amplification transistor 131A and the gate electrode 142A made of an n-type polysilicon electrode of the selection transistor 132A.

[0070] By this formation method, gate electrodes 142A, 142A are formed from p-type polysilicon (p-poly) and n-type polysilicon (n-poly), respectively, according to the work functions, so that the threshold voltage of the amplification transistor 131A is higher than the threshold voltage of the selection transistor 132A.

[0071] As a result, by selecting the materials of the gate electrodes 141A and 142A of the amplification transistor 131A and the selection transistor 132A according to the work function, the impurity concentrations in the channel regions can be made to be approximately the same 10 17 cm -3 Since the threshold voltage can be adjusted in a state where the impurity concentration is about 0.1 V or less, it is possible to reduce variations in the threshold voltage caused by the impurity concentration.

[0072] Although the above description has been given of an example in which the difference in threshold voltage between the amplifier transistor 131 and the selection transistor 132 is adjusted, the present invention may also be used to adjust the threshold voltage between other transistors in the pixel transistors.

[0073] That is, in order to adjust the magnitude relationship of the threshold voltages generated among the pixel transistors, namely, the transfer transistor (TRG) 122, the reset transistor (RST) 124, the amplification transistor (AMP) 131, and the selection transistor (SEL) 132, the material of the gate electrode may be selected according to the work function.

[0074] <<3. Second Embodiment>> In the above, an example has been described in which the gate electrode 141A of the amplification transistor 131A and the gate electrode 142A of the selection transistor 132A are formed from p-type polysilicon (p-poly) and n-type polysilicon (n-poly) according to their work functions, respectively, so that the threshold voltage of the amplification transistor 131A is higher than the threshold voltage of the selection transistor 132A.

[0075] However, the gate electrodes of the amplification transistor and the selection transistor may be made of a material other than p-type polysilicon (p-poly) and n-type polysilicon (n-poly), and may be made of, for example, a metal called a work function metal.

[0076] FIG. 7 shows an example in which a metal called a work function metal is used as the gate electrodes of the amplification transistor and the selection transistor.

[0077] The amplifier transistor 131B and the select transistor 132B in FIG. 7 are composed of gate electrodes 141B and 142B, a silicon substrate 143B, and n+ regions 144B-1 to 144B-3.

[0078] Furthermore, the n+ regions 144B-1 and 144B-2 function as the source and drain of the amplification transistor 131B, and the n+ regions 144B-2 and 144B-3 function as the source and drain of the selection transistor 132B.

[0079] That is, in FIG. 7, the gate electrode 141B and n+ regions 144B-1 and 144B-2 form the amplification transistor 131B, and the gate electrode 142B and n+ regions 144B-2 and 144B-3 form the selection transistor 132B.

[0080] 7 correspond to the amplifier transistor 131 and select transistor 132 in the left part of Fig. 5. That is, the gate electrode 141B of the amplifier transistor 131B, the gate electrode 142B of the select transistor 132B, the silicon substrate 143B, and the n+ regions 144B-1 to 144B-3 correspond to the gate electrode 141 of the amplifier transistor 131, the gate electrode 142 of the select transistor 132, the silicon substrate 143, and the n+ regions 144-1 to 144-3 in the left part of Fig. 5, respectively.

[0081] FIG. 7 shows an example in which the materials WF_A and WF_B of the gate electrode 141B of the amplifier transistor 131B and the gate electrode 142B of the select transistor 132B are work function metals.

[0082] That is, for the materials WF_A and WF_B of the gate electrode 141B of the amplification transistor 131B and the gate electrode 142B of the selection transistor 132B, metal materials called work function metals are selected according to their respective work functions so that the threshold voltage of the amplification transistor 131B is higher than the threshold voltage of the selection transistor 132B.

[0083] Examples of metal materials include La, Hf, Ta, Zr, Cd, In, Ag, Al, Nb, V, Zn, Sn, Cr, W, Ru, Ti, Os, Rh, Re, Ir, and Pt.

[0084] Here, the case where La, Hf, Ru, and W are used as examples will be described.

[0085] The metal material of the gate electrodes 141B and 142B may be not only a simple metal made of a work function metal but also an alloy made of a plurality of metals, such as an alloy of TiAl.

[0086] In this way, by selecting the materials of the gate electrodes 141B and 142B of the amplification transistor 131B and the selection transistor 132B according to the work function, the impurity concentrations in the channel regions can be made to be approximately the same 1017 cm -3 Since the threshold voltage can be adjusted in a state where the impurity concentration is about 0.1 V or less, it is possible to reduce variations in the threshold voltage caused by the impurity concentration.

[0087] <Method for forming the gate electrodes of the amplification transistor and the selection transistor in Figure 7 (gate-first process)> Next, with reference to Figure 8, we will explain a first formation method when adopting the gate-first process, among the methods for forming the gate electrode 141B of the amplification transistor 131B and the gate electrode 142B of the selection transistor 132B in Figure 7.

[0088] In FIG. 8, the states of the first, second, third, and fourth steps are displayed as cross sections in order from the upper left to the right, and then the state of the fifth step is displayed as a cross section at the bottom left.

[0089] In the first step, a uniform first metal film 141B' is deposited on the silicon substrate 143B via a gate oxide film. The metal material deposited at this time may be the work function metal used for the gate electrode 141B of the amplifier transistor 131B or the work function metal used for the gate electrode 142B of the select transistor 132B. In this example, however, the metal film 141B' made of the work function metal used for the gate electrode 141B of the amplifier transistor 131B is deposited.

[0090] In the second process, a region of the first metal film 141B' that is wider than the gate electrode 142B is opened at the position of the gate electrode 142B of the select transistor 132B by photolithography, thereby converting the first metal film 141B' into the first metal film 141B''.

[0091] In the third step, a second metal film 142B' used for the gate electrode 142B of the select transistor 132B is deposited.

[0092] In a fourth step, the second metal film 142B′ is polished by a technique such as CMP (Chemical Mechanical Polishing) to be flattened so that the first metal film 141B″ and the second metal film 142B″ are exposed.

[0093] In a fifth step, photolithography and dry etching are used to process and form the gate electrodes 141B and 142B from the first metal film 141B'' and the second metal film 142B''.

[0094] By using such a forming method, it is possible to form the gate electrode 141B of the amplification transistor 131B and the gate electrode 142B of the selection transistor 132B using different metal materials.

[0095] As a result, gate electrodes 142B, 142B made of work function metals having different work functions are formed so that the threshold voltage of the amplification transistor 131B is higher than the threshold voltage of the selection transistor 132B.

[0096] As a result, in the amplification transistor 131B and the selection transistor 132B formed by the first formation method, the impurity concentration of the channel region can be set to approximately the same 10 by selecting the work function metal that is the material of the gate electrodes 141B and 142B according to the work function. 17 cm -3 Since the threshold voltage can be adjusted in a state where the impurity concentration is about 0.1 V or less, it is possible to reduce variations in the threshold voltage caused by the impurity concentration.

[0097] <Method for forming the gate electrodes of the amplification transistor and the selection transistor in Figure 7 (gate-last process)> Above, with reference to Figure 8, we have explained the first method for forming the gate electrodes 141B, 142B when using the gate-first process, but other formation methods may also be used, for example, the gate-last process.

[0098] Next, a second method for forming the gate electrode 141B of the amplifier transistor 131B and the gate electrode 142B of the select transistor 132B in FIG. 7, which employs a gate-last process, will be described with reference to FIG.

[0099] In FIG. 9, the states of the first, second, third, and fourth steps are displayed as cross sections from the upper left to the right, and then the states of the fifth and sixth steps are displayed as cross sections from the lower left to the right.

[0100] In the first step, a uniform polysilicon film is deposited on the silicon substrate 143B via a gate oxide film. After this, photolithography and dry etching are used to process and form dummy gate electrodes 161-1 and 161-2 made of the polysilicon film. Then, the peripheries of the dummy gate electrodes 161-1 and 161-2 are filled with an insulating film 162.

[0101] In the second step, the dummy gate electrodes 161-1 and 161-2 made of polysilicon films are removed, and gate electrode frames 161'-1 and 161'-2 are formed in the insulating film 162.

[0102] In the third step, a first metal film 141B'' made of a work function metal used for the gate electrode 141B of the amplifier transistor 131B is deposited on the insulating film 162 so that the gate electrode frames 161'-1 and 161'-2 are embedded therein.

[0103] In the fourth step, photolithography is used to open an area of ​​the first metal film 141B' that is wider than the position of the gate electrode 142 of the select transistor 132, and a portion of the first metal film 141B'' is removed to form the first metal film 141B''', and the gate electrode frame 161'-2 is formed again.

[0104] In a fifth step, a second metal film 142B''' used for the gate electrode 142B of the select transistor 132B is deposited on the first metal film 141B''' and the gate electrode frame 161'-2.

[0105] In the sixth step, the second metal film 142B''' is polished by a technique such as CMP (Chemical Mechanical Polishing) to be planarized while exposing the first metal film 141B''' and the second metal film 142B''', and the gate electrodes 141B and 142B are processed and formed.

[0106] By using such a forming method, it is possible to form the gate electrode 141B of the amplification transistor 131B and the gate electrode 142B of the selection transistor 132B using different metal materials.

[0107] As a result, gate electrodes 142B, 142B made of functional metals with different work functions are formed so that the threshold voltage of the amplification transistor 131B is higher than the threshold voltage of the selection transistor 132B.

[0108] As a result, in the amplification transistor 131B and the selection transistor 132B formed by the second formation method, the impurity concentration in the channel region can be set to approximately the same 10 by selecting the work function metal that is the material of the gate electrodes 141B and 142B according to the work function. 17 cm -3 Since the threshold voltage can be adjusted in a state where the impurity concentration is about 0.1 V or less, it is possible to reduce variations in the threshold voltage caused by the impurity concentration.

[0109] <<4. Third Embodiment>> In the above, an example has been described in which the amplifier transistor 131A is configured with a single metal called a work function metal, each of which has a work function such that the threshold voltage of the amplifier transistor 131A is higher than the threshold voltage of the select transistor 132A. However, the amplifier transistor 131A may be configured with a stacked film of multiple types of metals and metal compounds.

[0110] FIG. 10 shows an example in which a metal called work function metal is used in multiple layers as the gate electrodes of the amplification transistor and the selection transistor.

[0111] The amplifying transistor 131C and the selecting transistor 132C in FIG. 10 are each composed of gate electrodes 141C, 142C, a silicon substrate 143C, and n+ regions 144C-1 to 144C-3.

[0112] Furthermore, the n+ regions 144C-1 and 144C-2 function as the source and drain of the amplification transistor 131C, and the n+ regions 144C-2 and 144C-3 function as the source and drain of the selection transistor 132C.

[0113] That is, in FIG. 11, the gate electrode 141C and n+ regions 144C-1 and 144C-2 form an amplifying transistor 131C, and the gate electrode 142C and n+ regions 144C-2 and 144C-3 form a selecting transistor 132C.

[0114] 5. An amplifier transistor 131C and a selection transistor 132C in FIG. 10 have configurations corresponding to the amplifier transistor 131 and the selection transistor 132 in the left part of FIG.

[0115] That is, the gate electrode 141C of the amplification transistor 131C, the gate electrode 142C of the selection transistor 132C, the silicon substrate 143C, and the n+ regions 144C-1 to 144C-3 correspond to the gate electrode 141 of the amplification transistor 131, the gate electrode 142 of the selection transistor 132, the silicon substrate 143, and the n+ regions 144-1 to 144-3 on the left side of Figure 5, respectively.

[0116] In FIG. 10, the material of the gate electrode 141C of the amplifier transistor 131C and the gate electrode 142C of the select transistor 132C is a laminated film of multiple metals according to the work function, so that the threshold voltage of the amplifier transistor 131C is higher than the threshold voltage of the select transistor 132C.

[0117] More specifically, the gate electrode 141C of the amplifier transistor 131C is made of a laminated film in which a metal film 141Ca made of W and a metal film 141Cb made of TiN are laminated.

[0118] The gate electrode 142C of the selection transistor 132C is made of a laminated film in which a metal film 142Ca made of W, a metal film 142Cb made of TiAl, and a metal film 142Cc made of TiN are laminated.

[0119] That is, in the example of Figure 10, due to the effect of the metal film 142Cb made of TiAl sandwiched between the metal film 142Ca made of W and the metal film 142Cc made of TiN in the gate electrode 142C of the selection transistor 132C, the work function of the gate electrode 142C is made lower than the work function of the gate electrode 141A of the amplification transistor 131A.

[0120] As described above, even when the gate electrodes 141C and 142C, such as the amplifier transistor 131C and the select transistor 132C, are made of a laminated film of a plurality of metals according to the work function, the impurity concentration of the channel region is set to approximately the same 10 17 cm -3 Since the threshold voltage can be adjusted in a state where the impurity concentration is about 0.1 V or less, it is possible to reduce variations in the threshold voltage caused by the impurity concentration.

[0121] Although the above has described an example in which the gate electrode is formed from a laminated film of multiple metals according to the work function, the metals may include, in addition to simple metals, alloys, and metal silicides and metal nitrides described later, and the gate electrode may be formed from a laminated film in which at least one of these is laminated. Furthermore, the gate electrode may be formed from a laminated film in which a non-metallic component including alloys, metal silicides, and metal nitrides is laminated, and n-type polysilicon or p-type polysilicon is laminated.

[0122] <<5. Fourth Embodiment>> In the above, an example has been described in which the gate electrode is made of a stack of multiple metals called work function metals, each having a different work function, so that the threshold voltage of the amplification transistor 131 is higher than the threshold voltage of the selection transistor 132. However, the gate electrode may be made of a metal silicide or a metal nitride.

[0123] FIG. 11 shows an example in which metal silicide is used as the gate electrodes of the amplifier transistor and the select transistor.

[0124] The amplifier transistor 131D and the select transistor 132D in FIG. 11 are each composed of gate electrodes 141D and 142D, a silicon substrate 143D, and n+ regions 144D-1 to 144D-3.

[0125] Furthermore, the n+ regions 144D-1 and 144D-2 function as the source and drain of the amplification transistor 131D, and the n+ regions 144D-2 and 144D-3 function as the source and drain of the selection transistor 132D.

[0126] That is, in FIG. 11, the gate electrode 141D and n+ regions 144D-1 and 144D-2 form an amplification transistor 131D, and the gate electrode 142D and n+ regions 144D-2 and 144D-3 form a selection transistor 132D.

[0127] 5. An amplifier transistor 131D and a selection transistor 132D in FIG. 11 have configurations corresponding to the amplifier transistor 131 and the selection transistor 132 in the left part of FIG.

[0128] That is, the gate electrode 141D of the amplification transistor 131D, the gate electrode 142D of the selection transistor 132D, the silicon substrate 143D, and the n+ regions 144D-1 to 144D-3 correspond to the gate electrode 141 of the amplification transistor 131, the gate electrode 142 of the selection transistor 132, the silicon substrate 143, and the n+ regions 144-1 to 144-3 on the left side of Figure 5, respectively.

[0129] In FIG. 11, the metal silicide material of each of the gate electrode 141D of the amplification transistor 131D and the gate electrode 142D of the selection transistor 132D is selected according to the work function so that the threshold voltage of the amplification transistor 131D is higher than the threshold voltage of the selection transistor 132D.

[0130] More specifically, in FIG. 11, the gate electrode 141D of the amplifier transistor 131D is made of a metal silicide such as Ni3Si.

[0131] Furthermore, the gate electrode 142D of the selection transistor 132D is made of a metal silicide such as NiSi2.

[0132] Other metal silicides such as WSi2, MoSi, CoSi2, TiSi2, and TaSi2 may also be used for the gate electrodes 141D and 142D.

[0133] Furthermore, the gate electrodes 141D and 142D may be made of not only a metal silicide but also a metal nitride, and for example, TiN or TaN may be used as the metal nitride.

[0134] As described above, even when the gate electrodes 141D and 142D of the amplifier transistor 131D and the select transistor 132D are made of a metal silicide or a metal nitride according to the work function, the impurity concentration of the channel region is set to approximately the same 10 17 cm -3 Since the threshold voltage can be adjusted in a state where the impurity concentration is about 0.1 V or less, it is possible to reduce variations in the threshold voltage caused by the impurity concentration.

[0135] <<6. Fifth Embodiment>> In the above, the description has been given on the assumption that the gate electrode 141 of the amplification transistor 131 and the gate electrode 142 of the selection transistor 132 have a planar gate structure as shown second from the left in FIG. 12 , but other structures may also be used.

[0136] In FIG. 12, different structural examples are shown in order from the second from the left to the right in relation to the W cross section of the gate electrode 141 of the amplification transistor 131 shown at the leftmost part.

[0137] The gate structure of the gate electrode 141 may be, for example, a FinFET structure (fin transistor structure) shown in the center of Fig. 12. In the FinFET structure, silicon 143' of a silicon substrate 143 is buried in a gate electrode 141' as shown in Fig. 12.

[0138] The gate structure of the gate electrode 141 may be, for example, an SOI (Silicon on Insulator) FinFET structure, which is one of the FinFET structures shown in the second from the right in Fig. 12. In the SOI FinFET structure, silicon 143'' of a silicon substrate 143 is buried in the gate electrode 141'', and an insulating film 165 is formed directly below the gate electrode 141''.

[0139] Furthermore, the gate structure of the gate electrode 141 may be, for example, a gate all around (GAA) structure shown in the rightmost part of Fig. 12. In the GAA (Gate All Around) structure, silicon 143'''-1 and 143'''-2 of the silicon substrate 143 are inserted into and surrounded by the gate electrode 141'''.

[0140] In particular, as the width of the channel region becomes smaller, it becomes difficult to control the threshold voltage using impurities, so it is effective to control the threshold voltage using gate electrodes in a FinFET structure (including SOI FinFET structure) or GAA structure, which do not use impurities but only work function.

[0141] <<7. Effects of a Single-Layer Substrate-Type Photodetector>> Next, the effects of the structure of a single-layer substrate-type photodetector when the technology of the present disclosure is applied will be described. For example, as shown in FIG. 13 , in the case of a so-called single-layer substrate-type photodetector in which the photoelectric conversion unit (PD) 121 and the region ZY in which other pixel transistors are formed are provided on the same layer, a comparison will be made between adjusting the threshold voltage by impurity implantation and adjusting the threshold voltage by the work function.

[0142] When adjusting the threshold voltage by impurity implantation, even if the channel region is designed to be formed in the region ZX surrounded by the dashed line as shown in the left part of Figure 13, a phenomenon known as misalignment that occurs in the manufacturing process may result in the channel region being formed shifted to the region ZX' surrounded by the dotted line.

[0143] In such a case, in the area where region ZX' overlaps with the photoelectric conversion unit 121 consisting of a photodiode (PD), there is a risk that impurities may also be mixed into the photoelectric conversion unit 121, which may result in an impurity injection region ZD being created in the photoelectric conversion unit 121 and reduce pixel sensitivity.

[0144] However, in the present disclosure, since no impurities are injected into the channel region in the first place, even if the channel region is formed in region ZX', as shown in the right part of Figure 13, impurities will not be mixed into the photoelectric conversion unit 121, and it is possible to prevent a situation that would lead to a decrease in pixel sensitivity.

[0145] <<8. Effects in a laminated substrate type photodetector>> <In the case of a laminated substrate type photodetector in which a layer in which pixel transistors are formed and a layer in which photoelectric conversion elements are formed are separated> Next, the effects in a laminated substrate type photodetector when the technology of the present disclosure is applied will be described. For example, consider the case of a laminated substrate type photodetector in which the photoelectric conversion unit 121 and a layer in which other pixel transistors are formed are stacked, and adjustment using the work function.

[0146] For example, as shown in FIG. 14, in a configuration in which a photoelectric conversion unit (PD) 121 is formed on the first layer Ph1, and an amplification transistor 131X and a selection transistor 132X are formed on the second layer Ph2, the gate electrodes 141X and 142X can both be made of a metal, such as a work function metal.

[0147] In this case, too, there is no need to inject impurities into the channel region, so that the impurities do not get mixed into the photoelectric conversion section (PD) 121, and the influence of contamination by impurities can be prevented.

[0148] In addition, in Figure 14, in the first layer Ph1, a photoelectric conversion section 121 and an n+ region 181 are formed in a silicon substrate 182, and a gate electrode 122a of a transfer transistor 122 is formed on the silicon substrate 182 so as to straddle the photoelectric conversion section 121 and the n+ region 181.

[0149] In addition, in the second layer Ph2, a silicon substrate 143X is formed, and n+ regions 144X-11 to 144X-13 are formed on the upper part, a gate electrode 141X is formed so as to straddle the n+ regions 144X-11 and 144X-12, and a gate electrode 142X is formed so as to straddle the n+ regions 144X-12 and 144X-13.

[0150] That is, the gate electrode 141X and the n+ regions 144X-11 and 144X-12 constitute the amplification transistor 131X, and the gate electrode 142X and the n+ regions 144X-12 and 144X-13 constitute the selection transistor 132X.

[0151] The n+ regions 144X-11 to 144X-13 are each connected to a contact 171. The n+ region 144X-11 is electrically connected, via the contact 171, to a through contact 171a that is connected to an n+ region 181 of the first layer Ph1.

[0152] With this configuration, a pixel signal is transferred from the photoelectric conversion unit 121 on the first layer Ph1 via the transfer transistor 122, the n+ region 181, the through contact 171a, and the contact 171 to the gate electrode 141X of the amplification transistor 131X.

[0153] <In the case of a laminated substrate type photodetector in which the layer in which the pixel transistors are formed and the layer in which the photoelectric conversion elements are formed are separated> Furthermore, for example, in the case of a laminated substrate type photodetector in which the pixel transistors are also formed in the layer in which the photoelectric conversion unit 121 is formed, consider the case in which the threshold voltage is adjusted using the work function as in the present disclosure.

[0154] For example, as shown in Figure 15, in a configuration in which a photoelectric conversion unit (PD) 121 and an amplification transistor 131Y are formed on the first layer Ph1, and a selection transistor 132Y is formed on the second layer Ph2, the gate electrode 142Y can be made of, for example, a metal such as a work function metal, but the gate electrode 141Y needs to be made of polysilicon or the like.

[0155] In this case, the photoelectric conversion unit 121 is formed in the same layer as the amplification transistor 131Y in the first layer Ph11, but here too, there is no need to inject impurities into the channel region, so it is possible to prevent impurities from being mixed into the photoelectric conversion unit (PD) 121.

[0156] The same applies to the selection transistor 132Y of the second layer Ph12, and the photoelectric conversion unit (PD) 121 is also free from impurities.

[0157] As a result, the photodetector device of FIG. 15 can also be prevented from being affected by contamination due to impurities.

[0158] 15 , in the first layer Ph11, the photoelectric conversion unit 121 and n+ regions 181 and 191 are formed in a silicon substrate 182, and the gate electrode 122a of the transfer transistor 122 is formed on the silicon substrate 182 so as to straddle the photoelectric conversion unit 121 and the n+ region 191. In addition, the gate electrode 141Y of the amplifier transistor 131Y is formed on the silicon substrate 182 so as to straddle the n+ regions 181 and 191.

[0159] That is, the gate electrode 141Y and the n+ regions 181 and 191 form an amplifying transistor 131Y.

[0160] Furthermore, in the second story Ph2, a silicon substrate 143Y is formed, and n+ regions 144Y-12 and 144Y-13 are formed on the upper part thereof, and a gate electrode 142Y is formed so as to straddle the n+ regions 144Y-12 and 144Y-13.

[0161] That is, the gate electrode 142Y and the n+ regions 144Y-12 and 144X-13 form the select transistor 132Y.

[0162] The n+ regions 144Y-12 and 144Y-13 are each connected to a contact 171. The n+ region 144Y-12 is electrically connected, via the contact 171, to a through contact 171a that is connected to an n+ region 181 of the first layer Ph11.

[0163] With this configuration, a pixel signal is transferred from the photoelectric conversion unit 121 of the first layer Ph11 to the gate electrode 144Y of the selection transistor 132Y via the transfer transistor 122, the n+ region 191, the gate electrode 141Y of the amplification transistor 131Y, the n+ region 181, the through contact 171a, and the contact 171.

[0164] As described above, according to the present disclosure, in any of the configurations, it is possible to adjust the difference in threshold voltage between pixel transistors without variation.

[0165] <<9. Application Examples>> Although the configuration of a photodetector consisting of two substrates, a first layer and a second layer, has been described above, the present invention may also be applied to a photodetector consisting of three substrates. A photodetector consisting of three substrates will be described below.

[0166] 16 shows an example of a schematic configuration of a photodetector 301 including three substrates according to an application example of the present disclosure. The photodetector 301 includes three substrates (a first substrate 3310, a second substrate 320, and a third substrate 330). The photodetector 301 has a three-dimensional structure formed by bonding together the three substrates (the first substrate 310, the second substrate 320, and the third substrate 330). The first substrate 310, the second substrate 320, and the third substrate 330 are stacked in this order.

[0167] The first substrate 310 has a plurality of sensor pixels 312 that perform photoelectric conversion on a semiconductor substrate 311. The semiconductor substrate 311 corresponds to a specific example of a "first semiconductor substrate" in the present disclosure. The plurality of sensor pixels 312 are arranged in a matrix within a pixel region 313 on the first substrate 310.

[0168] The second substrate 320 has, on a semiconductor substrate 321, one readout circuit 322 for every four sensor pixels 312. The readout circuits 322 output pixel signals based on the charges output from the sensor pixels 312. The semiconductor substrate 321 corresponds to a specific example of a "second semiconductor substrate" in the present disclosure. The second substrate 320 has a plurality of pixel drive lines 323 extending in the row direction and a plurality of vertical signal lines 324 extending in the column direction.

[0169] The third substrate 330 includes a logic circuit 332 that processes pixel signals on a semiconductor substrate 331. The semiconductor substrate 331 corresponds to a specific example of a "third semiconductor substrate" in the present disclosure. The logic circuit 332 includes, for example, a vertical drive circuit 333, a column signal processing circuit 334, a horizontal drive circuit 335, and a system control circuit 336. The logic circuit 332 (specifically, the horizontal drive circuit 335) outputs an output voltage Vout for each sensor pixel 312 to the outside. In the logic circuit 332, for example, a low-resistance region made of silicide formed using a salicide (self-aligned silicide) process such as CoSi2 or NiSi may be formed on the surface of an impurity diffusion region in contact with the source electrode and the drain electrode.

[0170] The vertical drive circuit 333, for example, sequentially selects a plurality of sensor pixels 312 row by row. The column signal processing circuit 334, for example, performs correlated double sampling (CDS) processing on pixel signals output from each sensor pixel 312 in the row selected by the vertical drive circuit 333. By performing CDS processing, for example, the column signal processing circuit 334 extracts signal levels of the pixel signals and holds pixel data corresponding to the amount of light received by each sensor pixel 312.

[0171] The horizontal drive circuit 335 sequentially outputs, for example, the pixel data held in the column signal processing circuit 334 to the outside. The system control circuit 336 controls the driving of each block (the vertical drive circuit 333, the column signal processing circuit 334, and the horizontal drive circuit 335) in the logic circuit 332, for example.

[0172] Fig. 17 shows an example of a sensor pixel 312 and a readout circuit 322. Below, a case will be described in which four sensor pixels 312 share one readout circuit 322, as shown in Fig. 17. Here, "shared" means that the outputs of the four sensor pixels 312 are input to a common readout circuit 322.

[0173] The sensor pixels 312 have common components. In Fig. 17, in order to distinguish the components of the sensor pixels 312 from one another, an identification number (1, 2, 3, 4) is added to the end of the reference numeral of the component of each sensor pixel 312. Hereinafter, when it is necessary to distinguish the components of each sensor pixel 312 from one another, an identification number is added to the end of the reference numeral of the component of each sensor pixel 312. However, when it is not necessary to distinguish the components of each sensor pixel 312 from one another, the identification number at the end of the reference numeral of the component of each sensor pixel 312 is omitted.

[0174] Each sensor pixel 312 has, for example, a photodiode PD, a transfer transistor TR electrically connected to the photodiode PD, and a floating diffusion FD that temporarily holds the charge output from the photodiode PD via the transfer transistor TR.

[0175] The photodiode PD corresponds to a specific example of a "photoelectric conversion element" in the present disclosure. The photodiode PD performs photoelectric conversion to generate an electric charge according to the amount of light received. The cathode of the photodiode PD is electrically connected to the source of the transfer transistor TR, and the anode of the photodiode PD is electrically connected to a reference potential line (e.g., ground).

[0176] The drain of the transfer transistor TR is electrically connected to the floating diffusion FD, and the gate of the transfer transistor TR is electrically connected to the pixel drive line 323. The transfer transistor TR is, for example, a CMOS (Complementary Metal Oxide Semiconductor) transistor.

[0177] The floating diffusions FD of the sensor pixels 312 that share one readout circuit 322 are electrically connected to each other and to the input terminal of the common readout circuit 322. The readout circuit 322 includes, for example, a reset transistor RST, a selection transistor SEL, and an amplification transistor AMP. Note that the selection transistor SEL may be omitted if necessary.

[0178] The source of the reset transistor RST (the input terminal of the readout circuit 322) is electrically connected to the floating diffusion FD, the drain of the reset transistor RST is electrically connected to the power supply line VDD and the drain of the amplifier transistor AMP, and the gate of the reset transistor RST is electrically connected to the pixel drive line 323 (see FIG. 16).

[0179] The source of the amplification transistor AMP is electrically connected to the drain of the selection transistor SEL, the gate of the amplification transistor AMP is electrically connected to the source of the reset transistor RST, the source of the selection transistor SEL (the output terminal of the readout circuit 322) is electrically connected to the vertical signal line 324, and the gate of the selection transistor SEL is electrically connected to the pixel drive line 323 (see FIG. 16 ).

[0180] When the transfer transistor TR is turned on, it transfers the charge of the photodiode PD to the floating diffusion FD. The gate (transfer gate TG) of the transfer transistor TR extends from the surface of the semiconductor substrate 311 through the well layer to a depth reaching the photodiode PD.

[0181] The reset transistor RST resets the potential of the floating diffusion FD to a predetermined potential. When the reset transistor RST is turned on, the potential of the floating diffusion FD is reset to the potential of the power supply line VDD.

[0182] The selection transistor SEL controls the output timing of the pixel signal from the readout circuit 322. The amplification transistor AMP generates, as the pixel signal, a signal with a voltage corresponding to the level of the charge held in the floating diffusion FD.

[0183] The amplifier transistor AMP forms a source-follower amplifier and outputs a pixel signal having a voltage corresponding to the level of the charge generated in the photodiode PD. When the select transistor SEL is turned on, the amplifier transistor AMP amplifies the potential of the floating diffusion FD and outputs a voltage corresponding to the potential to the column signal processing circuit 334 via the vertical signal line 324. The reset transistor RST, the amplifier transistor AMP, and the select transistor SEL are, for example, CMOS transistors.

[0184] <<10. Application Examples to Electronic Devices>> The photodetector device 81 in FIG. 3 described above can be applied to various electronic devices, such as imaging devices such as digital still cameras and digital video cameras, mobile phones with imaging functions, and other devices with imaging functions.

[0185] FIG. 18 is a block diagram showing an example of the configuration of an imaging device as an electronic device to which the present technology is applied.

[0186] The imaging device 1001 shown in Figure 18 is configured with an optical system 1002, a shutter device 1003, a solid-state imaging element 1004, a drive circuit 1005, a signal processing circuit 1006, a monitor 1007, and a memory 1008, and is capable of capturing still images and moving images.

[0187] The optical system 1002 is configured with one or more lenses, and guides light from a subject (incident light) to the solid-state image sensor 1004 to form an image on the light-receiving surface of the solid-state image sensor 1004 .

[0188] The shutter device 1003 is disposed between the optical system 1002 and the solid-state image sensor 1004 , and controls the light irradiation period and light blocking period for the solid-state image sensor 1004 under the control of the drive circuit 1005 .

[0189] The solid-state imaging element 1004 is configured as a package including the above-mentioned solid-state imaging element. The solid-state imaging element 1004 accumulates signal charges for a certain period of time in response to light that is imaged on the light-receiving surface via the optical system 1002 and the shutter device 1003. The signal charges accumulated in the solid-state imaging element 1004 are transferred in accordance with a drive signal (timing signal) supplied from a drive circuit 1005.

[0190] The drive circuit 1005 outputs drive signals that control the transfer operation of the solid-state image sensor 1004 and the shutter operation of the shutter device 1003 , thereby driving the solid-state image sensor 1004 and the shutter device 1003 .

[0191] The signal processing circuit 1006 performs various signal processing on the signal charges output from the solid-state imaging device 1004. The image (image data) obtained by the signal processing performed by the signal processing circuit 1006 is supplied to a monitor 1007 for display, or supplied to a memory 1008 for storage (recording).

[0192] Even in the imaging device 1001 configured in this manner, by applying the photodetector device 81 of Figure 3 instead of the above-mentioned solid-state imaging element 1004, it is possible to adjust the difference in threshold voltage between pixel transistors without any variation.

[0193] <<11. Usage Example of Solid-State Imaging Device>> FIG. 19 is a diagram showing a usage example of the above-described photodetector device 81. In FIG.

[0194] The above-described light detection device 81 can be used in various cases for sensing light such as visible light, infrared light, ultraviolet light, and X-rays, for example, as follows.

[0195] ・Devices for taking images for viewing purposes, such as digital cameras and mobile devices with camera functions. ・Devices for traffic purposes, such as in-vehicle sensors that take images of the front, rear, surroundings, and interior of a car for safe driving such as automatic stopping, and for recognizing the driver's state, surveillance cameras that monitor moving vehicles and roads, and distance measuring sensors that measure distances between vehicles. ・Devices for home appliances such as TVs, refrigerators, and air conditioners that take images of user gestures and operate the device according to those gestures. ・Devices for medical and healthcare purposes, such as endoscopes and devices that take images of blood vessels by receiving infrared light. ・Devices for security purposes, such as surveillance cameras for crime prevention and cameras for person authentication. ・Devices for beauty purposes, such as skin measuring devices that take images of the skin and microscopes that take images of the scalp. ・Devices for sports purposes, such as action cameras and wearable cameras for sports, etc. ・Devices for agricultural purposes, such as cameras to monitor the condition of fields and crops.

[0196] 12. Application Example to Endoscopic Surgery System 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 applied to an endoscopic surgery system.

[0197] FIG. 20 is a diagram showing an example of a schematic configuration of an endoscopic surgery system to which the technology according to the present disclosure (the present technology) can be applied.

[0198] 20 shows an operator (doctor) 11131 performing surgery on a patient 11132 on a patient bed 11133 using an endoscopic surgery system 11000. As shown in the figure, the endoscopic surgery system 11000 is composed of an endoscope 11100, other surgical tools 11110 such as an insufflation tube 11111 and an energy treatment tool 11112, a support arm device 11120 that supports the endoscope 11100, and a cart 11200 on which various devices for endoscopic surgery are mounted.

[0199] The endoscope 11100 is composed of a lens barrel 11101, a region of a predetermined length from the tip of which is inserted into a body cavity of a patient 11132, and a camera head 11102 connected to the base end of the lens barrel 11101. In the example shown, the endoscope 11100 is configured as a so-called rigid scope having a rigid lens barrel 11101, but the endoscope 11100 may also be configured as a so-called flexible scope having a flexible lens barrel.

[0200] An opening into which an objective lens is fitted is provided at the tip of the lens barrel 11101. A light source device 11203 is connected to the endoscope 11100, and light generated by the light source device 11203 is guided to the tip of the lens barrel by a light guide extending inside the lens barrel 11101, and is irradiated via the objective lens toward an object to be observed inside the body cavity of the patient 11132. The endoscope 11100 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0201] An optical system and an image sensor are provided inside the camera head 11102, and light reflected from the object of observation (observation light) is collected onto the image sensor by the optical system. The observation light is photoelectrically converted by the image sensor to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. The image signal is sent to a camera control unit (CCU) 11201 as RAW data.

[0202] The CCU 11201 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and comprehensively controls the operations of the endoscope 11100 and the display device 11202. Furthermore, the CCU 11201 receives an image signal from the camera head 11102 and performs various types of image processing on the image signal, such as development processing (demosaic processing), to display an image based on the image signal.

[0203] Under the control of the CCU 11201, the display device 11202 displays an image based on an image signal that has been subjected to image processing by the CCU 11201.

[0204] The light source device 11203 is composed of a light source such as an LED (light emitting diode), and supplies irradiation light to the endoscope 11100 when photographing the surgical site, etc.

[0205] The input device 11204 is an input interface for the endoscopic surgery system 11000. A user can input various information and instructions to the endoscopic surgery system 11000 via the input device 11204. For example, the user inputs an instruction to change the imaging conditions (type of irradiation light, magnification, focal length, etc.) of the endoscope 11100.

[0206] The treatment tool control device 11205 controls the driving of the energy treatment tool 11112 for cauterizing tissue, incising, sealing blood vessels, etc. The insufflation device 11206 inflates the body cavity of the patient 11132 through the insufflation tube 11111 in order to ensure a clear field of view for the endoscope 11100 and a working space for the surgeon. The recorder 11207 is a device capable of recording various types of information related to the surgery. The printer 11208 is a device capable of printing various types of information related to the surgery in various formats such as text, images, or graphs.

[0207] The light source device 11203, which supplies illumination light to the endoscope 11100 when photographing the surgical site, can be configured from a white light source, such as an LED, a laser light source, or a combination of these. When the white light source is configured from a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, allowing the light source device 11203 to adjust the white balance of the captured image. In this case, it is also possible to time-share images corresponding to each RGB by irradiating the object of observation with laser light from each RGB laser light source and controlling the drive of the image sensor of the camera head 11102 in synchronization with the irradiation timing. According to this method, color images can be obtained without providing a color filter to the image sensor.

[0208] Furthermore, the light source device 11203 may be controlled to change the intensity of light it outputs at predetermined time intervals. By controlling the driving of the image sensor of the camera head 11102 in synchronization with the timing of the change in light intensity to acquire images in a time-division manner and combining the images, it is possible to generate an image with a high dynamic range that is free from so-called blocked-up shadows and blown-out highlights.

[0209] The light source device 11203 may also be configured to supply light in a predetermined wavelength band corresponding to special light observation. Special light observation, for example, utilizes the wavelength dependence of light absorption in body tissues to irradiate light with a narrower band than the light irradiated during normal observation (i.e., white light), thereby capturing high-contrast images of specific tissues, such as blood vessels on the surface of mucous membranes, known as narrow-band imaging. Alternatively, special light observation may involve fluorescence observation, in which images are obtained using fluorescence generated by irradiating excitation light. Fluorescence observation may involve irradiating excitation light onto body tissues and observing the fluorescence from the tissue (autofluorescence observation), or by locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the tissue with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 11203 may be configured to supply narrow-band light and / or excitation light corresponding to such special light observation.

[0210] FIG. 21 is a block diagram showing an example of the functional configuration of the camera head 11102 and the CCU 11201 shown in FIG.

[0211] The camera head 11102 has a lens unit 11401, an imaging unit 11402, a drive unit 11403, a communication unit 11404, and a camera head control unit 11405. The CCU 11201 has a communication unit 11411, an image processing unit 11412, and a control unit 11413. The camera head 11102 and the CCU 11201 are connected to each other via a transmission cable 11400 so that they can communicate with each other.

[0212] The lens unit 11401 is an optical system provided at the connection portion with the lens barrel 11101. Observation light taken in from the tip of the lens barrel 11101 is guided to the camera head 11102 and enters the lens unit 11401. The lens unit 11401 is composed of a combination of multiple lenses including a zoom lens and a focus lens.

[0213] The imaging unit 11402 may include one imaging element (a so-called single-chip type) or multiple imaging elements (a so-called multi-chip type). When the imaging unit 11402 is configured as a multi-chip type, for example, each imaging element may generate an image signal corresponding to each of RGB, and a color image may be obtained by combining these signals. Alternatively, the imaging unit 11402 may be configured to have a pair of imaging elements for acquiring image signals for the right eye and the left eye corresponding to a 3D (dimensional) display. The 3D display allows the surgeon 11131 to more accurately grasp the depth of the biological tissue at the surgical site. Note that when the imaging unit 11402 is configured as a multi-chip type, multiple lens units 11401 may be provided corresponding to each imaging element.

[0214] Furthermore, the imaging unit 11402 does not necessarily have to be provided in the camera head 11102. For example, the imaging unit 11402 may be provided inside the lens barrel 11101, immediately after the objective lens.

[0215] The driving unit 11403 is configured by an actuator, and moves the zoom lens and focus lens of the lens unit 11401 by a predetermined distance along the optical axis under the control of the camera head control unit 11405. This allows the magnification and focus of the image captured by the imaging unit 11402 to be adjusted appropriately.

[0216] The communication unit 11404 is configured by a communication device for transmitting and receiving various types of information to and from the CCU 11201. The communication unit 11404 transmits the image signal obtained from the imaging unit 11402 to the CCU 11201 via the transmission cable 11400 as RAW data.

[0217] Furthermore, the communication unit 11404 receives a control signal for controlling the driving of the camera head 11102 from the CCU 11201 and supplies the control signal to the camera head control unit 11405. The control signal includes information on the imaging conditions, such as information specifying the frame rate of the captured image, information specifying the exposure value at the time of imaging, and / or information specifying the magnification and focus of the captured image.

[0218] The image capturing conditions such as the frame rate, exposure value, magnification, and focus may be appropriately specified by the user, or may be automatically set by the control unit 11413 of the CCU 11201 based on the acquired image signal. In the latter case, the endoscope 11100 is equipped with a so-called AE (Auto Exposure) function, AF (Auto Focus) function, and AWB (Auto White Balance) function.

[0219] The camera head control unit 11405 controls the driving of the camera head 11102 based on a control signal received from the CCU 11201 via the communication unit 11404 .

[0220] The communication unit 11411 is configured by a communication device for transmitting and receiving various information to and from the camera head 11102. The communication unit 11411 receives an image signal transmitted from the camera head 11102 via the transmission cable 11400.

[0221] Furthermore, the communication unit 11411 transmits to the camera head 11102 a control signal for controlling the driving of the camera head 11102. The image signal and the control signal can be transmitted by electrical communication, optical communication, or the like.

[0222] The image processing unit 11412 performs various image processing operations on the image signal, which is RAW data transmitted from the camera head 11102 .

[0223] The control unit 11413 performs various controls related to the imaging of the surgical site, etc. by the endoscope 11100 and the display of the captured image obtained by imaging the surgical site, etc. For example, the control unit 11413 generates a control signal for controlling the driving of the camera head 11102.

[0224] Furthermore, the control unit 11413 displays the captured image showing the surgical site, etc., on the display device 11202 based on the image signal subjected to image processing by the image processing unit 11412. At this time, the control unit 11413 may recognize various objects in the captured image using various image recognition technologies. For example, the control unit 11413 can recognize surgical tools such as forceps, specific biological parts, bleeding, mist generated when using the energy treatment tool 11112, etc., by detecting the shape and color of the edges of objects included in the captured image. When displaying the captured image on the display device 11202, the control unit 11413 may use the recognition results to superimpose various surgical support information on the image of the surgical site. By superimposing the surgical support information and presenting it to the surgeon 11131, the burden on the surgeon 11131 can be reduced and the surgeon 11131 can proceed with the surgery reliably.

[0225] The transmission cable 11400 connecting the camera head 11102 and the CCU 11201 is an electrical signal cable for electrical signal communication, an optical fiber for optical communication, or a composite cable of these.

[0226] In the illustrated example, communication is performed wired using a transmission cable 11400, but communication between the camera head 11102 and the CCU 11201 may also be performed wirelessly.

[0227] The foregoing has described an example of an endoscopic surgery system to which the technology according to the present disclosure can be applied. The technology according to the present disclosure can be applied to, for example, the endoscope 11100 or the camera head 11102 (the imaging unit 11402) among the above-described configurations. Specifically, for example, the photodetector 81 in FIG. 3 can be applied to the imaging unit 11402. Applying the technology according to the present disclosure to the imaging unit 11402 makes it possible to adjust the difference in threshold voltage between pixel transistors without variation.

[0228] Although an endoscopic surgery system has been described as an example here, the technology according to the present disclosure may also be applied to other systems, such as a microsurgery system.

[0229] <<13. Application Examples to Mobile Bodies>> 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 mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0230] 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.

[0231] 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.

[0232] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0233] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0234] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0235] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0236] 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.

[0237] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0238] 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.

[0239] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0240] 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, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0241] FIG. 23 is a diagram showing an example of the installation position of the imaging unit 12031.

[0242] In FIG. 23, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0243] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0244] 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, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0245] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0246] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation.

[0247] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0248] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0249] The foregoing has described an example of a vehicle control system to which the technology according to the present disclosure can be applied. The technology according to the present disclosure can be applied to, for example, the image capture unit 12031 among the above-described configurations. Specifically, for example, the photodetector 81 in FIG. 3 can be applied to the image capture unit 12031. By applying the technology according to the present disclosure to the image capture unit 12031, it becomes possible to adjust the difference in threshold voltage between pixel transistors without variation.

[0250] Furthermore, each step described in the above flowchart can be executed by one device, or can be shared and executed by a plurality of devices.

[0251] Furthermore, when one step includes multiple processes, the multiple processes included in that one step can be executed by one device or can be shared and executed by multiple devices.

[0252] The present disclosure may also be configured as follows. <1> A photodetector including: a photoelectric conversion unit that photoelectrically converts incident light in accordance with the amount of light and generates charges per pixel; and a plurality of transistors that generate pixel signals per pixel based on the charges, wherein at least one gate electrode of the plurality of transistors has a work function different from that of the other transistors. <2> The plurality of transistors include: a transfer transistor that transfers the charges; an amplifier transistor that amplifies the pixel signal based on the charges; a reset transistor that resets the charges; and a select transistor that selects the pixel. <3> The photodetector according to <2>, wherein the gate electrodes of the transfer transistor, the amplifier transistor, the select transistor, and the reset transistor are made of at least one of n-type polysilicon, p-type polysilicon, a metal, an alloy, a metal nitride, and a metal silicide, or a laminate film thereof. <4> The photodetector according to <2>, wherein the work function of the gate electrode of the amplifier transistor is different from that of the select transistor. <5> The photodetector according to <4>, wherein the work function of the gate electrode of the amplifying transistor is greater than the work function of the gate electrode of the selection transistor. <6> The photodetector according to <5>, wherein the gate electrode of the amplifying transistor is made of p-type polysilicon, and the gate electrode of the selection transistor is made of n-type polysilicon. <7> The photodetector according to <4>, wherein the gate electrode of the amplifying transistor and the gate electrode of the selection transistor are made of different metals. <8> The photodetector according to <4>, wherein the impurity concentrations of the channel region of the amplifying transistor and the channel region of the selection transistor are approximately equal. <9> The impurity concentrations of the channel region of the amplifying transistor and the channel region of the selection transistor are both 1×10 17 cm -3The photodetector according to <8>, wherein: <10> At least one of the plurality of transistors is a fin transistor. <11> The photodetector according to any of <1> to <9>, wherein at least one of the plurality of transistors is a gate-all-around transistor. <12> The photodetector according to <1>, wherein a first substrate and a second substrate are stacked, the photoelectric conversion unit is formed on the first substrate, and the plurality of transistors are formed on the second substrate. <13> The photodetector according to <2>, wherein a first substrate and a second substrate are stacked, the photoelectric conversion unit is formed on the first substrate, and the selection transistor and the amplification transistor are formed on the second substrate. <14> The photodetector according to <1>, wherein a first substrate and a second substrate are stacked, the photoelectric conversion unit and at least one of the plurality of transistors are formed on the first substrate, and the plurality of transistors other than the transistor formed on the first substrate are formed on the second substrate. <15> The photodetector according to <2>, wherein a first substrate and a second substrate are stacked, a photoelectric conversion unit and the amplifying transistor are formed on the first substrate, and the selection transistor is formed on the second substrate. <16> An imaging device having a photodetector including: a photoelectric conversion unit that performs photoelectric conversion of incident light in accordance with the amount of light and generates charges per pixel; and a plurality of transistors that generate pixel signals per pixel based on the charges, wherein a gate electrode of at least one of the plurality of transistors has a work function different from that of the other transistors. <17> An electronic device having a photodetector including: a photoelectric conversion unit that performs photoelectric conversion of incident light in accordance with the amount of light and generates charges per pixel; and a plurality of transistors that generate pixel signals per pixel based on the charges, wherein a gate electrode of at least one of the plurality of transistors has a work function different from that of the other transistors.

[0253] 81 imaging element, 93, 312 pixel, 121 photoelectric conversion section, 122 transfer transistor, 123 charge holding section, 131, 131A to 131D amplification transistor, 132, 132A to 132D selection transistor, 141, 141A to 141D, 142, 142A to 142D gate electrode, 144, 144-1 to 144-3, 144A to 144D n+ region

Claims

1. A photodetection device comprising: a photoelectric conversion unit that performs photoelectric conversion on incident light according to the amount of light and generates charges per pixel; and a plurality of transistors that generate pixel signals per pixel based on the charges, wherein the gate electrode of at least one of the plurality of transistors has a work function different from that of the other transistors.

2. The photodetection device according to claim 1, wherein the plurality of transistors include a transfer transistor that transfers the charge, an amplification transistor that amplifies the pixel signal based on the charge, a reset transistor that resets the charge, and a selection transistor that selects the pixel.

3. The photodetector according to claim 2, wherein the gate electrodes of the transfer transistor, the amplifying transistor, the selection transistor and the reset transistor are made of at least one of n-type polysilicon, p-type polysilicon, a metal, an alloy, a metal nitride and a metal silicide, or a laminate film thereof.

4. The photodetector according to claim 2, wherein the gate electrode of the amplifying transistor and the gate electrode of the selection transistor have different work functions.

5. The photodetector according to claim 4, wherein the work function of the gate electrode of the amplifying transistor is greater than the work function of the gate electrode of the selection transistor.

6. The photodetector according to claim 5, wherein the gate electrode of the amplifying transistor is made of p-type polysilicon, and the gate electrode of the selection transistor is made of n-type polysilicon.

7. The photodetector according to claim 4, wherein the gate electrode of the amplifying transistor and the gate electrode of the selection transistor are made of different metals.

8. The photodetector according to claim 4, wherein the impurity concentration of the channel region of the amplifying transistor and the channel region of the selection transistor are approximately equal.

9. The impurity concentration of the channel region of the amplification transistor and the channel region of the selection transistor is 1×10 17 cm -3 The light detection device according to claim 8 , wherein:

10. The photodetector device according to claim 1, wherein at least one of the plurality of transistors is a fin-type transistor.

11. The photodetector according to claim 1, wherein at least one of the plurality of transistors is a gate-all-around type transistor.

12. The photodetector according to claim 1, wherein a first substrate and a second substrate are laminated, the photoelectric conversion section is formed on the first substrate, and the plurality of transistors are formed on the second substrate.

13. The photodetector according to claim 2, wherein a first substrate and a second substrate are laminated, the photoelectric conversion section is formed on the first substrate, and the selection transistor and the amplification transistor are formed on the second substrate.

14. The photodetector according to claim 1, wherein a first substrate and a second substrate are laminated, a photoelectric conversion unit and at least one of the plurality of transistors are formed on the first substrate, and the plurality of transistors other than the transistor formed on the first substrate are formed on the second substrate.

15. The photodetector according to claim 2, wherein a first substrate and a second substrate are laminated, a photoelectric conversion section and the amplifying transistor are formed on the first substrate, and the selection transistor is formed on the second substrate.

16. An imaging device having a photodetector comprising: a photoelectric conversion unit that photoelectrically converts incident light according to the amount of light and generates charges per pixel; and a plurality of transistors that generate pixel signals per pixel based on the charges, wherein the gate electrode of at least one of the plurality of transistors has a work function different from that of the gate electrodes of the other transistors.

17. An electronic device having a photodetector comprising: a photoelectric conversion unit that photoelectrically converts incident light according to the amount of light and generates charges per pixel; and a plurality of transistors that generate pixel signals per pixel based on the charges, wherein the gate electrode of at least one of the plurality of transistors has a work function different from that of the gate electrodes of the other transistors.

Images