Pixel unit, image sensor chip and imaging system with dual charge storage structure

Abstract

The present application provides a pixel unit with a dual charge storage structure, an image sensor chip with a dual charge storage structure, and an imaging system, wherein the pixel unit includes: a substrate; a photodiode; a first voltage signal output module, which outputs a voltage signal when receiving a control signal; a second voltage signal output module, which outputs a voltage signal when receiving a control signal; wherein the control signal sent to the first switch is set to have the same phase as the modulated light, and the control signal sent to the second switch is set to be complementary to the phase sent to the modulated light, and after receiving the reflected light, the voltage signals output by the first voltage signal output module and the second voltage signal output module at different phases are obtained, and the flight time of the modulated light is calculated. The present application can improve the reaction speed of the pixel unit, and can measure different distances with relatively high measurement accuracy.

Description

Technical Field

[0001] The present application relates to the field of image processing, and in particular to a pixel unit with a dual charge storage structure, an image sensor chip with a dual charge storage structure, and an imaging system. Background Art

[0002] Compared with CCD image sensors, CMOS image sensors have the advantages of low power consumption, low cost and high integration. Moreover, since their manufacturing process is compatible with standard CMOS technology, CMOS image sensors have developed rapidly and have now become a research hotspot.

[0003] See also Figure 1 The traditional 4T-PPD is mainly composed of a clamped photodiode PPD, a transmission tube TG, a floating diffusion area FD, a source follower SF, a gate tube SEL and a reset tube RST. The brief working principle of the 4T-PPD pixel is as follows:

[0004] First, during the reset period of the pixel unit, the reset tube RST and the transmission tube TG are turned on at the same time, so that the electrons inside the N buried layer are depleted. At this time, the N buried layer will be in an empty well state, and the floating diffusion area FD will also be at a high potential. At this time, the potential of the floating diffusion node is output to the bus as the first signal of the correlated double sampling CDS through the source follower SF and the gate tube SEL. Secondly, after the exposure time is completed, the transmission tube TG is turned on for the second time, so that the charges accumulated under the suspended inversion layer of the clamped photodiode PPD are transferred to the N-type floating diffusion area (FD), and remain on the floating diffusion area FD after the transmission tube TG is turned off, forming a voltage VFD. The voltage VFD outputs the voltage through the source follower (SF), and is controlled by the gate tube (SEL) as the second signal of the correlated double sampling (CDS) and transferred to the bus. Finally, the input signals of the two correlated double sampling (CDS) are subtracted by the subsequent circuit to obtain the analog value representing the corresponding light signal, which is converted into a digital quantity by the subsequent ADC, and the required image is obtained after processing.

[0005] use Figure 1 The traditional 4T-PPD pixel unit with a single floating diffusion (FD) shown in the figure is used for ranging, but has the problems of slow response speed and can only measure long distances. At the same time, a high-speed photodetector and a high-precision timing circuit are also required for measurement, otherwise it is difficult to obtain high-precision depth information. In some high-precision security detection and industrial control fields, fast and high-precision ranging methods are very necessary, so it cannot meet the requirements of high-precision industries such as security detection and industrial control. Summary of the invention

[0006] The present application provides a pixel unit with a dual charge storage structure, an image sensor chip with a dual charge storage structure, an imaging system, a method for forming a pixel unit with a dual charge storage structure, a depth information calculation method, and a method for measuring image depth by an imaging system, which can solve the problems of using a traditional 4-transistor active pixel sensor when measuring image depth information, such as slow response speed, only being able to measure long distances, and being unable to meet the requirements of high-precision industries such as safety detection and industrial control.

[0007] According to a first aspect of the present application, the present application provides a pixel unit with a dual charge storage structure, the pixel unit comprising: a substrate; a photodiode, which is arranged in the substrate and is used to accumulate charge in response to reflected light incident on the photodiode; a first voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and comprises a first switch, the control end of the first switch receives a control signal, the input end of the first switch is connected to the photodiode, and the output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and a second voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and comprises a second switch, the control end of the second switch receives the control signal, the input end of the second switch is connected to the photodiode The output end of the second switch outputs a second voltage signal when the control end of the second switch receives a control signal; wherein, the control signal sent to the first switch is set to have the same phase as the modulated light, and the control signal sent to the second switch is set to have a complementary phase to the control signal sent to the first switch, and the modulated light is emitted to the object to be measured. When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal module is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal module is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; according to the formula: , the flight time of the modulated light is calculated, where It is the time that the level of the modulated light is high in one cycle.

[0008] Preferably, when the two-tap four-phase method is used for measurement, after the photodiode of the pixel unit receives the reflected light again, the voltage output by the first voltage signal module is obtained as the first voltage signal PS2 output by the first voltage signal output module when the phase of the reflected light is 90°, and the voltage output by the second voltage signal module is obtained as the second voltage signal PS3 output by the second voltage signal output module when the phase of the reflected light of the modulated light is 270°; according to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0009] Preferably, the photodiode is arranged at the center of the substrate, the first switch of the first voltage signal output module is a first transfer transistor, the first transfer transistor is arranged in the substrate and on one side of the photodiode, the first transfer transistor is coupled to the photodiode to output the charge accumulated in the photodiode as a voltage signal, the second switch of the second voltage signal output module is a second transfer transistor, the second transfer transistor is arranged in the substrate and symmetrically arranged on the other side of the photodiode, the second transfer transistor is coupled to the photodiode to output the charge accumulated in the photodiode as a voltage signal; the first voltage signal output module also includes: a first floating diffusion region, which is arranged in the substrate and on the side of the first transfer transistor away from the photodiode, wherein the first transfer transistor transfers the charge accumulated in the photodiode to the first floating diffusion region for storage; a first reset transistor, which is arranged in the substrate and coupled to the photodiode, for outputting the charge accumulated in the photodiode to the first floating diffusion region for storage; A floating diffusion region is used to reset the charge stored in the first floating diffusion region; a first source follower transistor, whose control end is connected to the first floating diffusion region, and whose input end is connected to the first reset transistor; and a first selection transistor, whose input end is connected to the output end of the first source follower transistor, and the output end of the first selection transistor outputs a voltage signal; the second voltage signal output module also includes: a second floating diffusion region, which is arranged in the substrate and arranged on the side of the second transfer transistor away from the photodiode, wherein the second transfer transistor transfers the charge of the photodiode to the second floating diffusion region for storage; a second reset transistor, which is arranged on the substrate to couple the photodiode and is used to reset the charge stored in the second floating diffusion region; a second source follower transistor, whose control end is connected to the second floating diffusion region, and whose input end is connected to the second reset transistor; and a second selection transistor, whose input end is connected to the output end of the second source follower transistor, and the output end of the second selection transistor outputs a voltage signal.

[0010] Preferably, the pixel unit further comprises a deep trench isolation structure, which is used to isolate active areas of adjacent pixel units and is arranged in the substrate around the periphery of the pixel unit.

[0011] Preferably, the pixel unit further comprises a light shielding plate, which is used to block light from irradiating onto areas other than the photodiode and shield electrical interference, and is disposed on the upper surfaces of the first voltage signal output module and the second voltage signal output module.

[0012] Preferably, the pixel unit further includes a microlens, which is used to focus light and irradiate it onto the photosensitive area of ​​the photodiode, and is arranged on the upper surface of the pixel unit.

[0013] According to a second aspect of the present application, the present application provides an image sensor chip with a dual charge storage structure, the image sensor chip comprising: a pixel array, which comprises a plurality of pixel units as claimed in claim 1, or, comprising: a substrate; a plurality of photodiodes, the photodiodes are arranged in the substrate, and are used to accumulate charges in response to reflected light incident on the photodiodes, a first voltage signal output module, which is used to convert the charges accumulated in the photodiodes into a voltage signal, which comprises a first switch, the control end of the first switch receives a control signal, the input end of the first switch is connected to the photodiode, and the output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and a second voltage signal output module, which is used to convert the charges accumulated in the photodiodes into a voltage signal, which comprises a second switch, the control end of the second switch receives the control signal, and the output end of the second switch outputs a first voltage signal. The input end is connected to the photodiode, and the output end of the second switch outputs a second voltage signal when receiving a control signal at the control end of the second switch, wherein the photodiodes form an array, and the photodiodes share a first voltage signal output module and a second voltage signal output module; a pixel driving unit, which is used to output a control signal to control the operation of the pixel units in the pixel array, and is connected to the pixel array; a readout unit, which is used to read and output the voltage signal output by the pixel units in the pixel array, and is connected to the pixel array; a control unit, which is connected to and controls the pixel array, the pixel driving unit and the readout unit; wherein the system turns on the modulated light emission source to send modulated light, and the control unit controls the control signal sent by the pixel driving unit to the first switch to have the same phase as the modulated light, and the control signal sent to the second switch is complementary to the phase of the control signal sent to the first switch, and the length of time after each emission is modulated is When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal module is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal module is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; according to the formula: , the flight time of the modulated light is calculated, where It is the time that the level of the modulated light is high in one cycle.

[0014] Preferably, when the two-tap four-phase method is used for measurement, after the photodiode of the pixel unit receives the reflected light again, the voltage output by the first voltage signal module is obtained as the first voltage signal PS2 output by the first voltage signal output module when the phase of the reflected light is 90°, and the voltage output by the second voltage signal module is obtained as the second voltage signal PS3 output by the second voltage signal output module when the phase of the reflected light of the modulated light is 270°; according to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0015] Preferably, the photodiode is arranged at the center of the substrate, the first switch of the first voltage signal output module is a first transfer transistor, the first transfer transistor is arranged in the substrate and on one side of the photodiode, the first transfer transistor is coupled to the photodiode to output the charge accumulated in the photodiode as a voltage signal, the second switch of the second voltage signal output module is a second transfer transistor, the second transfer transistor is arranged in the substrate and symmetrically arranged on the other side of the photodiode, the second transfer transistor is coupled to the photodiode to output the charge accumulated in the photodiode as a voltage signal; the first voltage signal output module also includes: a first floating diffusion region, which is arranged in the substrate and on the side of the first transfer transistor away from the photodiode, wherein the first transfer transistor transfers the charge accumulated in the photodiode to the first floating diffusion region for storage; a first reset transistor, which is arranged in the substrate and coupled to the photodiode, for outputting the charge accumulated in the photodiode to the first floating diffusion region for storage; A floating diffusion region is used to reset the charge stored in the first floating diffusion region; a first source follower transistor, whose control end is connected to the first floating diffusion region, and whose input end is connected to the first reset transistor; and a first selection transistor, whose input end is connected to the output end of the first source follower transistor, and the output end of the first selection transistor outputs a voltage signal; the second voltage signal output module also includes: a second floating diffusion region, which is arranged in the substrate and arranged on the side of the second transfer transistor away from the photodiode, wherein the second transfer transistor transfers the charge of the photodiode to the second floating diffusion region for storage; a second reset transistor, which is arranged on the substrate to couple the photodiode and is used to reset the charge stored in the second floating diffusion region; a second source follower transistor, whose control end is connected to the second floating diffusion region, and whose input end is connected to the second reset transistor; and a second selection transistor, whose input end is connected to the output end of the second source follower transistor, and the output end of the second selection transistor outputs a voltage signal.

[0016] Preferably, the pixel unit further comprises a deep trench isolation structure, which is used to isolate active areas of adjacent pixel units and is arranged in the substrate around the periphery of the pixel unit.

[0017] Preferably, the pixel unit further comprises a light shielding plate, which is used to block light from irradiating onto areas other than the photodiode and shield electrical interference, and is disposed on the upper surfaces of the first voltage signal output module and the second voltage signal output module.

[0018] Preferably, the pixel unit further includes a microlens, which is used to focus light and irradiate it onto the photosensitive area of ​​the photodiode, and is arranged on the upper surface of the pixel unit.

[0019] According to a third aspect of the present application, the present application provides an imaging system, which includes the image sensor chip and the laser emitter as described above.

[0020] According to a fourth aspect of the present application, the present application provides a method for forming a pixel unit with a dual charge storage structure, a method for forming a pixel unit, the method comprising: providing a substrate; providing a photodiode, which is provided in the substrate and is used to accumulate charge in response to reflected light incident on the photodiode; providing a first voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and which comprises a first switch, a control end of the first switch receives a control signal, an input end of the first switch is connected to the photodiode, and an output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and providing a second voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and which comprises a second switch, a control end of the second switch receives the control signal, The input end of the second switch is connected to the photodiode, and the output end of the second switch outputs a second voltage signal when the control end of the second switch receives a control signal; wherein, the control signal sent to the first switch is set to have the same phase as the modulated light, and the control signal sent to the second switch is set to be complementary to the phase of the control signal sent to the first switch, and the modulated light is emitted. When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected back by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal module is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal module is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; according to the formula: , the flight time of the modulated light is calculated, where It is the time that the level of the modulated light is high in one cycle.

[0021] Preferably, when the two-tap four-phase method is used for measurement, after the photodiode of the pixel unit receives the reflected light again, the voltage output by the first voltage signal module is obtained as the first voltage signal PS2 output by the first voltage signal output module when the phase of the reflected light is 90°, and the voltage output by the second voltage signal module is obtained as the second voltage signal PS3 output by the second voltage signal output module when the phase of the reflected light of the modulated light is 270°; according to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0022] According to a fifth aspect of the present application, the present application provides a depth information measurement method, a depth information measurement method, the method comprising: setting a pixel array, which comprises a plurality of pixel units as claimed in claim 1, or comprising: a substrate; a plurality of photodiodes, the photodiodes are arranged in the substrate, and are used to accumulate charges in response to reflected light incident on the photodiodes, a first voltage signal output module, which is used to convert the charges accumulated in the photodiodes into a voltage signal, which comprises a first switch, the control end of the first switch receives a control signal, the input end of the first switch is connected to the photodiode, and the output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and a second voltage signal output module, which is used to convert the charges accumulated in the photodiode into a voltage signal, which comprises a second switch, the control end of the second switch receives the control signal, the input end of the second switch A photodiode is connected, and the output end of the second switch outputs a second voltage signal when the control end of the second switch receives a control signal, wherein the photodiodes form an array, and the photodiodes share a first voltage signal output module and a second voltage signal output module; a pixel driving unit is set, which is used to output a control signal to control the operation of the pixel units in the pixel array, and the pixel array is connected; a readout unit is set, which is used to read and output the voltage signal output by the pixel units in the pixel array, and the pixel array is connected; a control unit is set, which is connected to and controls the pixel array, the pixel driving unit and the readout unit; wherein the system turns on the modulated light emission source to send modulated light, and the control unit controls the pixel driving unit to send the control signal to the first switch to have the same phase as the modulated light, and the control signal sent to the second switch is complementary to the phase of the control signal sent to the first switch, and the length of time after each emission is modulated is The control unit controls the pixel driving unit to output a control signal of the first switch of the first voltage signal output module that is the same as the phase of the laser pulse, and controls the pixel driving unit to output a control signal of the second switch of the second voltage signal output module that is complementary to the phase of the laser pulse. When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal module is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal module is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; according to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0023] Preferably, when the two-tap four-phase method is used for measurement, after the photodiode of the pixel unit receives the reflected light again, the voltage output by the first voltage signal module is obtained as the first voltage signal PS2 output by the first voltage signal output module when the phase of the reflected light is 90°, and the voltage output by the second voltage signal module is obtained as the second voltage signal PS3 output by the second voltage signal output module when the phase of the reflected light of the modulated light is 270°; according to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0024] According to the fifth aspect of the present application, the present application provides a method for measuring image depth by an imaging system, including: configuring command parameters of the imaging system; starting the imaging system; measuring the image depth information of the object to be measured according to the depth information measurement method as described above according to the configured command parameters; measuring the image grayscale information of the object to be measured according to the configured command parameters; obtaining the measured image depth value and image grayscale value, and performing calculations.

[0025] The beneficial effect of the present application is that: the present application sets a first voltage signal output module and a second voltage signal output module in a pixel unit structure, and the first voltage signal output module and the second voltage signal output module can convert the charge accumulated by the photodiode in response to the reflected light into a voltage signal after receiving the control signal, and then by setting the phase relationship between the first switch of the first voltage signal output module and the second switch of the second voltage signal output module and the modulated light, after receiving the reflected light, the voltage signals output by the first voltage signal output module and the second voltage signal output module at different phases are obtained, and the flight time of the modulated light can be calculated, so that the reaction speed of the pixel unit can be improved, and different distances can be measured with relatively high measurement accuracy, which meets the requirements of high-precision industries such as safety detection and industrial control, making the product more widely applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of a conventional 4-transistor active pixel sensor;

[0027] Figure 2 is a schematic structural diagram of a pixel unit with a dual charge storage structure in the first embodiment of the present application;

[0028] Figure 3 is a schematic structural diagram of a pixel unit with a dual charge storage structure in the second embodiment of the present application;

[0029] Figure 4 yes Figure 3 Schematic diagram of equivalent circuit;

[0030] Figure 5 is a schematic top view of the structure of a pixel unit in the second embodiment of the present application;

[0031] Figure 6 is another structural schematic diagram of a pixel unit in the second embodiment of the present application;

[0032] Figure 7 is a schematic diagram of an image sensor chip with a dual charge storage structure in a third embodiment of the present application;

[0033] Figure 8 It is a flowchart of the depth information calculation method shown in the seventh embodiment of the present application.

[0034] Explanation of the accompanying drawings: substrate 203 photodiode PPD first voltage signal output module 201 first transfer transistor TG1 first floating diffusion region FD1 first reset transistor RST1 first source follower transistor SF1 first selection transistor SEL1 second voltage signal output module 202 second transfer transistor TG2 second floating diffusion region FD2 second reset transistor RST2 second source follower transistor SF2 second selection transistor SEL2 first N-type ion region 301 second N-type ion region 302 third N-type ion region 303 fourth N-type ion region 304 N-type buried layer 305 deep trench isolation structure 306 light shielding plate 307 microlens 308 pixel array 401 pixel driving unit 402 readout unit 403 control unit 404. DETAILED DESCRIPTION

[0035] The present application is further described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0036] The idea of ​​the present application is to improve the accuracy of measuring image depth information by providing a pixel unit structure capable of measuring ambient light and reflected light of the measured object on the structure of the traditional 4T-APS, thereby expanding the scope of application of the product.

[0037] Embodiment 1:

[0038] See also Figure 2 The pixel unit with a double charge storage structure includes: a substrate 203, a photodiode PPD, a first voltage signal output module 201 and a second voltage signal output module 202.

[0039] A photodiode PPD, which is arranged in the substrate 203, and is used to accumulate charges in response to reflected light incident on the photodiode PPD; a first voltage signal output module 201, which is used to convert the charges accumulated in the photodiode PPD into a voltage signal, and includes a first switch, the control end of the first switch receives a control signal, the input end of the first switch is connected to the photodiode PPD, and the output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; a second voltage signal output module 202, which is used to convert the charges accumulated in the photodiode PPD into a voltage signal, and includes a second switch, the control end of the second switch receives a control signal, the input end of the second switch is connected to the photodiode PPD, and the output end of the second switch outputs a second voltage signal when the control end of the second switch receives the control signal.

[0040] The substrate 203 is used to form a device structure or a chip circuit. The substrate 203 may be a semiconductor substrate, and the semiconductor substrate includes a silicon substrate 203, a silicon germanium substrate 203, a silicon carbide substrate 203, a silicon on insulator (SOI) substrate 203, a germanium on insulator (GOI) substrate 203, a glass substrate 203, or a III-V compound substrate 203 (such as silicon nitride or gallium arsenide, etc.). The substrate 203 may also be a bulk substrate, that is, a silicon substrate 203, a silicon germanium substrate 203, or a silicon carbide substrate 203. In other embodiments, the substrate 203 may also be a silicon on insulator substrate 203 or a germanium on insulator substrate 203. In other embodiments, the substrate 203 may also include a semiconductor substrate and an epitaxial layer formed on the surface of the semiconductor substrate by an epitaxial process.

[0041] In this embodiment, the substrate 203 includes: a P-type single crystal silicon substrate 203 (p-type substrate) and a P-type epitaxial layer (p-epitaxial layer).

[0042] The photodiode PPD is disposed in the substrate 203 and is formed by an ion implantation process. Furthermore, by controlling the energy and concentration of the ion implantation, the depth and implantation range of the ion implantation can be controlled, thereby controlling the depth and thickness of the photodiode PPD.

[0043] In this embodiment, the photodiode PPD is a pinned photodiode (PPD). The photodiode PPD is doped with N-type ions, including phosphorus ions, arsenic ions, or antimony ions. In addition, the photodiode PPD has an additional thin P+ layer compared to the surface layer of a traditional photodiode. The top P+ layer isolates the N buried layer of the charge collection layer from the top surface of Si / SiO2, covering up the traps that are the main cause of the dark current. This makes the clamped photodiode PPD have a smaller dark current than the traditional photodiode on the one hand, and on the other hand, it can form a fully depleted accumulation area, overcoming the problem of output image lag.

[0044] The photodiode PPD is arranged at the center position of the substrate 203, the first switch of the first voltage signal output module 201 is the first transfer transistor TG1, the first transfer transistor TG1 is arranged in the substrate 203 and on one side of the photodiode PPD, the first transfer transistor TG1 is coupled with the photodiode PPD to output the charge accumulated in the photodiode PPD as a voltage signal, the second switch of the second voltage signal output module 202 is the second transfer transistor TG2, the second transfer transistor TG2 is arranged in the substrate 203 and symmetrically on the other side of the photodiode PPD, the second transfer transistor TG2 is coupled with the photodiode PPD to output the charge accumulated in the photodiode PPD as a voltage signal.

[0045] Combine the following Figure 2 The working principle of this embodiment is described.

[0046] Among them, when the two-tap two-phase method is used for measurement, only one integration is required. Specifically, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module 202 when the phase of the reflected light is 180°; according to the formula: , the flight time of the modulated light is calculated, where To modulate light in one cycle The time when the internal level is high.

[0047] According to the formula: , calculate the image depth information of the object to be measured .

[0048] Further, when the two-tap four-phase method is used for measurement, two integrations are required, specifically, in the first integration stage, after the photodiode PPD of the pixel unit receives the reflected light reflected back by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; in the second integration stage, after the pixel unit receives the reflected light again, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS2 when the phase of the reflected light is 90°, and the voltage output by the second voltage signal output module 202 is obtained as the second voltage signal PS3 when the phase of the reflected light of the modulated light is 270°;

[0049] According to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0050] According to the formula: , calculate the image depth information of the object to be measured .

[0051] Embodiment 2:

[0052] See also Figure 3 and Figure 4 The pixel unit with a double charge storage structure includes: a substrate 203, a photodiode PPD, a first voltage signal output module 201 and a second voltage signal output module 202.

[0053] The substrate 203 is used to form a device structure or a chip circuit. The substrate 203 can be a semiconductor substrate, and the semiconductor substrate includes a silicon substrate, a silicon germanium substrate, a silicon carbide substrate, a silicon on insulator (SOI) substrate, a germanium on insulator (GOI) substrate, a glass substrate or a III-V compound substrate (such as silicon nitride or gallium arsenide, etc.). The substrate 203 can also be a bulk substrate, that is, a silicon substrate, a silicon germanium substrate or a silicon carbide substrate. In other embodiments, the substrate 203 can also be a silicon on insulator substrate or a germanium on insulator substrate. In other embodiments, the substrate 203 can also include a semiconductor substrate and an epitaxial layer formed on the surface of the semiconductor substrate by an epitaxial process. In this embodiment, the substrate 203 includes: a P-type single crystal silicon substrate (p-type substrate) and a P-type epitaxial layer (p-epitaxial layer).

[0054] The photodiode PPD is arranged in the substrate 203. The photodiode PPD is formed by an ion implantation process. Moreover, by controlling the energy and concentration of the ion implantation, the depth and implantation range of the ion implantation can be controlled, thereby controlling the depth and thickness of the photodiode PPD. In this embodiment, the photodiode PPD is a pinned photodiode (PPD). The photodiode PPD is doped with N-type ions, and the N-type ions include phosphorus ions, arsenic ions or antimony ions. In addition, the photodiode PPD has an additional thin P+ layer compared to the surface layer of a traditional photodiode. The top P+ layer isolates the N buried layer of the charge collection layer from the top surface of Si / SiO2, covering up the traps that are the main cause of the dark current, so that the clamped photodiode has a smaller dark current than the traditional photodiode on the one hand, and can form a fully depleted accumulation area on the other hand, overcoming the problem of output image lag.

[0055] Please continue reading Figure 3 and Figure 4 The first voltage signal output module 201 includes: a first transmission transistor TG1, a first floating diffusion region FD1, a first reset transistor RST1, a first source follower transistor SF1 and a first selection transistor SEL1.

[0056] A first transfer transistor TG1, which is arranged in the substrate 203 and on one side of the photodiode PPD, and the first transfer transistor TG1 is coupled to the photodiode PPD to output the charge accumulated in the photodiode PPD as a voltage signal; a first floating diffusion region FD1, which is arranged in the substrate 203 and on a side of the first transfer transistor TG1 away from the photodiode PPD, wherein the first transfer transistor TG1 transfers the charge accumulated in the photodiode PPD to the first floating diffusion region FD1 for storage; a first reset transistor RST1, which is arranged in the substrate 203 and coupled to the photodiode PPD, and is used to reset the charge stored in the first floating diffusion region FD1; a first source follower transistor SF1, whose control end is connected to the first floating diffusion region FD1, and whose input end is connected to the first reset transistor RST1; and a first selection transistor SEL1, whose input end is connected to the output end of the first source follower transistor SF1, and the output end of the first selection transistor SEL1 outputs a voltage signal.

[0057] In this embodiment, the first transmission transistor TG1 , the first reset transistor RST1 , the first source follower transistor SF1 , and the first selection transistor SEL1 are all MOS transistors.

[0058] The second voltage signal output module 202 includes: a second transmission transistor TG2, a second floating diffusion region FD2, a second reset transistor RST2, a second source follower transistor SF2 and a second selection transistor SEL2.

[0059] The second transfer transistor TG2 is arranged in the substrate 203 and is symmetrically arranged on the other side of the photodiode PPD with the first transfer transistor TG1, and the second transfer transistor TG2 is coupled with the photodiode PPD to output the charge accumulated by the photodiode PPD as a voltage signal; the second floating diffusion area FD2 is arranged in the substrate 203 and is arranged on the side of the second transfer transistor TG2 away from the photodiode PPD, wherein the second transfer transistor TG2 transfers the second voltage signal of the photodiode PPD to the second floating diffusion area FD2 for storage; the second reset transistor RST2 is arranged on the substrate 203 and coupled with the photodiode PPD, and is used to reset the charge stored in the second floating diffusion area FD2; the second source follower transistor SF2, whose control end is connected to the second floating diffusion area FD2, and whose input end is connected to the second reset transistor RST2; the second selection transistor SEL2, whose input end is connected to the output end of the second source follower transistor SF2, and the output end of the second selection transistor SEL2 outputs a voltage signal.

[0060] In this embodiment, the second transmission transistor TG2 , the second reset transistor RST2 , the second source follower transistor SF2 , and the second selection transistor SEL2 are all MOS transistors.

[0061] See also Figure 5 , Figure 5 2 is a top view of the structure of the pixel unit. The photodiode PPD is square and is arranged at the center of the substrate 203. The first transfer transistor TG1 is arranged on one side of the photodiode PPD, the first floating diffusion area FD1, the first reset transistor RST1, the first source follower transistor SF1 and the first selection transistor SEL1 are arranged on the side of the first transfer transistor TG1 away from the photodiode PPD, the second transfer transistor TG2 is symmetrical to the first transfer transistor TG1 and is arranged on the other side of the photodiode PPD, the second floating diffusion area FD2, the second reset transistor RST2, the second source follower transistor SF2 and the second selection transistor SEL2 are symmetrical to the first floating diffusion area FD1 and are arranged on the side of the second transfer transistor TG2 away from the photodiode PPD.

[0062] Please refer again Figure 3 and Figure 4 , Figure 42 is a cross-sectional schematic diagram of a pixel unit. The substrate 203 includes: a P-type single crystal silicon substrate and a P-type epitaxial layer. The photodiode PPD is a pinned photodiode (PPD). The photodiode PPD is disposed in the substrate 203. The photodiode PPD is formed by an ion implantation process to form a P-type epitaxial layer, an N-type buried layer 305, and a PNP structure of the P-type epitaxial layer. That is, in the direction of the Z axis, the P-type epitaxial layer is formed in the P-type single crystal silicon substrate, the N-type buried layer 305 is formed at the center of the P-type epitaxial layer, and the P+ type ion layer is formed in the N-type buried layer 305.

[0063] The first N-type ion region 301, the second N-type ion region 302, the third N-type ion region 303 and the fourth N-type ion region 304 are all formed in the P-type epitaxial layer, the first N-type ion region 301 and the second N-type ion region 302 are formed on one side of the N-type buried layer 305, and the third N-type ion region 303 and the fourth N-type ion region 304 are formed on the other side of the N-type buried layer 305. The first N-type ion region 301, the second N-type ion region 302, the third N-type ion region 303 and the fourth N-type ion region 304 are all doped with N+ type ions. The first N-type ion region 301 serves as the first floating diffusion region FD1, and the third N-type ion region 303 serves as the second floating diffusion region FD2.

[0064] The gate of the first transfer transistor TG1 is formed on one side of the P+ type ion layer, and the gate of the first reset transistor is formed between the first N type ion region 301 and the second N type ion region 302. The gate of the first source follower transistor SF1 is connected to the first floating diffusion region FD1, the drain of the first source follower transistor SF1 is connected to the second N type ion region 302 and the bias voltage, and the source of the first source follower transistor SF1 is connected to the source of the first selection transistor SEL1. The drain output voltage signal.

[0065] The gate of the second transfer transistor TG2 is formed on the other side of the P+ type ion layer, and the gate of the second reset transistor is formed between the third N type ion region 303 and the fourth N type ion region 304. The gate of the second source follower transistor SF2 is connected to the second floating diffusion region FD2, the drain of the second source follower transistor SF2 is connected to the second N type ion region 302 and the bias voltage, and the source of the second source follower transistor SF2 is connected to the source of the second selection transistor SEL2. The drain of the second selection transistor SEL2 outputs a voltage signal.

[0066] For further information, please refer to Figure 4 and Figure 6, the pixel unit also includes a deep trench isolation structure 306, which is used to isolate the active areas of adjacent pixel units, and is arranged in the substrate 203 around the periphery of the pixel unit. Specifically, the deep trench isolation structure 306 is formed in the P-type epitaxial layer, wherein one deep trench isolation structure 306 is formed on the side of the second N-type ion region 302 away from the N-type buried layer 305, and the other deep trench isolation structure 306 is formed on the side of the fourth N-type ion region 304 away from the N-type buried layer 305. The function of the deep trench isolation structure 306 (DTI) in the pixel is to isolate the active areas between pixels, which can suppress the photons injected from adjacent pixels, suppress the generation of dark current, and reduce crosstalk between pixels.

[0067] For further information, please refer to Figure 4 and Figure 6 , the pixel unit also includes a light shielding plate 307, which is used to block light from irradiating to areas other than the photodiode PPD and shield electrical interference, and is arranged on the upper surface of the first voltage signal output module 201 and the second voltage signal output module 202. In this embodiment, because the pixel unit contains a clamped photodiode PPD and several active circuits, the clamped photodiode PPD is used as a part for receiving light irradiation to obtain optical information, but other active circuits such as the first voltage signal output module 201 and the second voltage signal output module 202 do not need light irradiation. If other active circuits are illuminated, it will also cause changes in the parameters and performance of active transistors, and even cause circuit failure. Therefore, after completing all processes on the layout, the present invention covers all active transistor areas with a layer of light shielding plate 307. It not only has the function of shielding and reflecting light, but also has the function of shielding and preventing electrical interference after grounding. The material of the light shielding plate 307 in this embodiment is metal.

[0068] For further information, please refer to Figure 4 and Figure 6 The pixel unit also includes a microlens 308, which is used to focus light onto the photosensitive area of ​​the photodiode, and is disposed on the upper surface of the pixel unit. In this embodiment, in order to further improve the fill factor FF (ratio of the cross-sectional area of ​​the photosensitive area to the pixel area), the light-gathering effect of the microlens 308 is utilized to focus the light blocked by the surrounding area onto the photosensitive area of ​​the photodiode PPD.

[0069] Combine the following Figures 3 to 6 The working principle of this embodiment is described below.

[0070] First, by turning on the first transfer transistor TG1, the first reset transistor RST1, the second transfer transistor TG2 and the second reset transistor RST2, the first floating diffusion area FD1, the second floating diffusion area FD2 and the clamping photodiode PPD are reset to discharge the residual charge in the clamping photodiode PPD so that it meets the condition of complete depletion, and no photogenerated charge is generated when no modulated light signal is incident on the PPD.

[0071] Then the first transfer transistor TG1 , the first reset transistor RST1 , the second transfer transistor TG2 , and the second reset transistor RST2 are turned off, and the clamp photodiode PPD starts to accumulate charges.

[0072] The control signal sent to the first transfer transistor TG1 is set to have the same phase as the modulated light, and the control signal sent to the second transfer transistor TG2 is set to have a complementary phase to the control signal sent to the first transfer transistor TG1.

[0073] Modulated light is emitted, and the first transfer transistor TG1 and the second transfer transistor TG2 are turned on by the phase relationship between the pulse signal of the modulated light and the control signal applied to the first transfer transistor TG1 and the second transfer transistor TG2, and the charge accumulated in the photodiode PPD is transferred to the first floating diffusion area FD1 and the second floating diffusion area FD2, and after the first transfer transistor TG1 and the second transfer transistor TG2 are turned off, the voltage value is read out by turning on the first selection transistor SEL1 and the first selection transistor SEL2.

[0074] Among them, when the two-tap two-phase method is used for measurement, only one integration is required. Specifically, after the pixel unit receives the reflected light reflected back by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module 202 when the phase of the reflected light is 180°;

[0075] According to the formula: , the flight time of the modulated light is calculated, where To modulate light in one cycle The time when the internal level is high.

[0076] According to the formula: , calculate the image depth information of the object to be measured .

[0077] Further, when the two-tap four-phase method is used for measurement, two integrations are required, specifically, in the first integration stage, after the photodiode PPD of the pixel unit receives the reflected light reflected back by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; in the second integration stage, after the pixel unit receives the reflected light again, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS2 when the phase of the reflected light is 90°, and the voltage output by the second voltage signal output module 202 is obtained as the second voltage signal PS3 when the phase of the reflected light of the modulated light is 270°;

[0078] According to the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0079] According to the formula: , calculate the image depth information of the object to be measured .

[0080] Embodiment three:

[0081] See also Figure 7 The image sensor chip with a dual charge storage structure includes: a pixel array 401, a pixel driving unit 402, a readout unit 403 and a control unit 404.

[0082] A pixel array 401 is used to output a voltage signal; a pixel driving unit 402 is used to output a control signal to control the operation of the pixel units in the pixel array 401, and is connected to the pixel array 401; a readout unit 403 is used to read and output the voltage signal output by the pixel units in the pixel array 401, and is connected to the pixel array 401; a control unit 404 is connected to and controls the pixel array 401, the pixel driving unit 402, and the readout unit 403.

[0083] In this embodiment, the pixel array 401 may be composed of 160 120, 240x160, 320 240 or 640 Of course, the pixel array 401 can also be composed of pixel units of other specifications, and the specific specifications are set according to the actual needs of the user, so there is no limitation.

[0084] The pixel array 401 can be constructed in two ways:

[0085] The first type is a pixel array 401 , which includes a plurality of the above-mentioned pixel units. The pixel unit includes: a substrate 203 , a photodiode PPD, a first voltage signal output module 201 and a second voltage signal output module 202 .

[0086] The substrate 203 is used to form a device structure or a chip circuit. The substrate 203 can be a semiconductor substrate, and the semiconductor substrate includes a silicon substrate, a silicon germanium substrate, a silicon carbide substrate, a silicon on insulator (SOI) substrate, a germanium on insulator (GOI) substrate, a glass substrate or a III-V compound substrate (such as silicon nitride or gallium arsenide, etc.). The substrate 203 can also be a bulk substrate, that is, a silicon substrate, a silicon germanium substrate or a silicon carbide substrate. In other embodiments, the substrate 203 can also be a silicon on insulator substrate or a germanium on insulator substrate. In other embodiments, the substrate 203 can also include a semiconductor substrate and an epitaxial layer formed on the surface of the semiconductor substrate by an epitaxial process. In this embodiment, the substrate 203 includes: a P-type single crystal silicon substrate (p-type substrate) and a P-type epitaxial layer (p-epitaxial layer).

[0087] The photodiode PPD is arranged in the substrate 203. The photodiode PPD is formed by an ion implantation process. Moreover, by controlling the energy and concentration of the ion implantation, the depth and implantation range of the ion implantation can be controlled, thereby controlling the depth and thickness of the photodiode PPD. In this embodiment, the photodiode PPD is a pinned photodiode (PPD). The photodiode PPD is doped with N-type ions, and the N-type ions include phosphorus ions, arsenic ions or antimony ions. In addition, the photodiode PPD has an additional thin P+ layer compared to the surface layer of a traditional photodiode. The top P+ layer isolates the N buried layer of the charge collection layer from the top surface of Si / SiO2, covering up the traps that are the main cause of the dark current, so that the clamped photodiode has a smaller dark current than the traditional photodiode on the one hand, and can form a fully depleted accumulation area on the other hand, overcoming the problem of output image lag.

[0088] Please continue reading Figure 3 and Figure 4 The first voltage signal output module 201 includes: a first transmission transistor TG1, a first floating diffusion region FD1, a first reset transistor RST1, a first source follower transistor SF1 and a first selection transistor SEL1.

[0089] A first transfer transistor TG1, which is arranged in the substrate 203 and on one side of the photodiode PPD, and the first transfer transistor TG1 is coupled to the photodiode PPD to output the charge accumulated in the photodiode PPD as a voltage signal; a first floating diffusion region FD1, which is arranged in the substrate 203 and on a side of the first transfer transistor TG1 away from the photodiode PPD, wherein the first transfer transistor TG1 transfers the charge accumulated in the photodiode PPD to the first floating diffusion region FD1 for storage; a first reset transistor RST1, which is arranged in the substrate 203 and coupled to the photodiode PPD, and is used to reset the charge stored in the first floating diffusion region FD1; a first source follower transistor SF1, whose control end is connected to the first floating diffusion region FD1, and whose input end is connected to the first reset transistor RST1; and a first selection transistor SEL1, whose input end is connected to the output end of the first source follower transistor SF1, and the output end of the first selection transistor SEL1 outputs a voltage signal.

[0090] In this embodiment, the first transmission transistor TG1 , the first reset transistor RST1 , the first source follower transistor SF1 , and the first selection transistor SEL1 are all MOS transistors.

[0091] The second voltage signal output module 202 includes: a second transmission transistor TG2, a second floating diffusion region FD2, a second reset transistor RST2, a second source follower transistor SF2 and a second selection transistor SEL2.

[0092] The second transfer transistor TG2 is arranged in the substrate 203 and is symmetrical to the first transfer transistor TG1 and is arranged on the other side of the photodiode PPD. The second transfer transistor TG2 is coupled with the photodiode PPD to output the charge accumulated by the photodiode PPD as a voltage signal; the second floating diffusion area FD2 is arranged in the substrate 203 and is arranged on the side of the second transfer transistor TG2 away from the photodiode PPD, wherein the second transfer transistor TG2 transfers the charge of the photodiode PPD to the second floating diffusion area FD2 for storage; the second reset transistor RST2 is arranged on the substrate 203 and coupled to the photodiode PPD to reset the charge stored in the second floating diffusion area FD2; the second source follower transistor SF2, whose control end is connected to the second floating diffusion area FD2, and whose input end is connected to the second reset transistor RST2; the second selection transistor SEL2, whose input end is connected to the output end of the second source follower transistor SF2, and the output end of the second selection transistor SEL2 outputs a voltage signal.

[0093] In this embodiment, the second transmission transistor TG2 , the second reset transistor RST2 , the second source follower transistor SF2 , and the second selection transistor SEL2 are all MOS transistors.

[0094] See also Figure 5 , Figure 5 2 is a top view of the structure of the pixel unit. The photodiode PPD is square and is arranged at the center of the substrate 203. The first transfer transistor TG1 is arranged on one side of the photodiode PPD, the first floating diffusion area FD1, the first reset transistor RST1, the first source follower transistor SF1 and the first selection transistor SEL1 are arranged on the side of the first transfer transistor TG1 away from the photodiode PPD, the second transfer transistor TG2 is symmetrical to the first transfer transistor TG1 and is arranged on the other side of the photodiode PPD, the second floating diffusion area FD2, the second reset transistor RST2, the second source follower transistor SF2 and the second selection transistor SEL2 are symmetrical to the first floating diffusion area FD1 and are arranged on the side of the second transfer transistor TG2 away from the photodiode PPD.

[0095] Please refer again Figure 3 and Figure 4 , Figure 4 2 is a cross-sectional schematic diagram of a pixel unit. The substrate 203 includes: a P-type single crystal silicon substrate and a P-type epitaxial layer. The photodiode PPD is a pinned photodiode (PPD). The photodiode PPD is disposed in the substrate 203. The photodiode PPD is formed by an ion implantation process to form a P-type epitaxial layer, an N-type buried layer 305, and a PNP structure of the P-type epitaxial layer. That is, in the direction of the Z axis, the P-type epitaxial layer is formed in the P-type single crystal silicon substrate, the N-type buried layer 305 is formed at the center of the P-type epitaxial layer, and the P+ type ion layer is formed in the N-type buried layer 305.

[0096] The first N-type ion region 301, the second N-type ion region 302, the third N-type ion region 303 and the fourth N-type ion region 304 are all formed in the P-type epitaxial layer, the first N-type ion region 301 and the second N-type ion region 302 are formed on one side of the N-type buried layer 305, and the third N-type ion region 303 and the fourth N-type ion region 304 are formed on the other side of the N-type buried layer 305. The first N-type ion region 301, the second N-type ion region 302, the third N-type ion region 303 and the fourth N-type ion region 304 are all doped with N+ type ions. The first N-type ion region 301 serves as the first floating diffusion region FD1, and the third N-type ion region 303 serves as the second floating diffusion region FD2.

[0097] The gate of the first transfer transistor TG1 is formed on one side of the P+ type ion layer, and the gate of the first reset transistor is formed between the first N type ion region 301 and the second N type ion region 302. The gate of the first source follower transistor SF1 is connected to the first floating diffusion region FD1, the drain of the first source follower transistor SF1 is connected to the second N type ion region 302 and the bias voltage, and the source of the first source follower transistor SF1 is connected to the source of the first selection transistor SEL1. The drain output voltage signal.

[0098] The gate of the second transfer transistor TG2 is formed on the other side of the P+ type ion layer, and the gate of the second reset transistor is formed between the third N type ion region 303 and the fourth N type ion region 304. The gate of the second source follower transistor SF2 is connected to the second floating diffusion region FD2, the drain of the second source follower transistor SF2 is connected to the second N type ion region 302 and the bias voltage, and the source of the second source follower transistor SF2 is connected to the source of the second selection transistor SEL2. The drain of the second selection transistor SEL2 outputs a voltage signal.

[0099] For further information, please refer to Figure 4 and Figure 6 , the pixel unit also includes a deep trench isolation structure 306, which is used to isolate the active areas of adjacent pixel units, and is arranged in the substrate 203 around the periphery of the pixel unit. Specifically, the deep trench isolation structure 306 is formed in the P-type epitaxial layer, wherein one deep trench isolation structure 306 is formed on the side of the second N-type ion region 302 away from the N-type buried layer 305, and the other deep trench isolation structure 306 is formed on the side of the fourth N-type ion region 304 away from the N-type buried layer 305. The function of the deep trench isolation structure 306 (DTI) in the pixel is to isolate the active areas between pixels, which can suppress the photons injected from adjacent pixels, suppress the generation of dark current, and reduce crosstalk between pixels.

[0100] For further information, please refer to Figure 4 and Figure 6, the pixel unit also includes a light shielding plate 307, which is used to block light from irradiating to areas other than the photodiode PPD and shield electrical interference, and is arranged on the upper surface of the first voltage signal output module 201 and the second voltage signal output module 202. In this embodiment, because the pixel unit contains a clamped photodiode and several active circuits, the clamped photodiode is used as a part for receiving light irradiation to obtain optical information, but other active circuits such as the first voltage signal output module 201 and the second voltage signal output module 202 do not need light irradiation. If other active circuits are illuminated, it will also cause changes in the parameters and performance of active transistors, and even cause circuit failure. Therefore, after completing all processes on the layout, the present invention covers all active transistor areas with a layer of light shielding plate 307. It not only has the function of shielding and reflecting light, but also has the function of shielding and preventing electrical interference after grounding. The material of the light shielding plate 307 in this embodiment is metal.

[0101] For further information, please refer to Figure 4 and Figure 6 The pixel unit also includes a microlens 308, which is used to focus light and irradiate it onto the photosensitive area of ​​the photodiode PPD, and is disposed on the upper surface of the pixel unit. In this embodiment, in order to further improve the fill factor FF (ratio of the cross-sectional area of ​​the photosensitive area to the pixel area), the light-gathering effect of the microlens 308 is utilized to focus the light blocked by the surrounding area onto the photosensitive area of ​​the photodiode PPD.

[0102] The second type is that the pixel unit includes: a substrate 203 , a plurality of photodiodes PPD, a first voltage signal output module 201 and a second voltage signal output module 202 .

[0103] A plurality of photodiodes PPD are provided in a substrate 203, and are used for accumulating charges in response to reflected light incident on the photodiode PPD. A first voltage signal output module 201 is used for converting the charges accumulated in the photodiode PPD into a voltage signal, and includes a first switch, a control end of the first switch receives a control signal, an input end of the first switch is connected to the photodiode PPD, and an output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; a second voltage signal output module 202 is used for converting the charges accumulated in the photodiode PPD into a voltage signal, and includes a second switch, a control end of the second switch receives a control signal, an input end of the second switch is connected to the photodiode PPD, and an output end of the second switch outputs a second voltage signal when the control end of the second switch receives the control signal, wherein the photodiodes PPD form an array, and the photodiodes PPD share the first voltage signal output module 201 and the second voltage signal output module 202.

[0104] The structures of the first voltage signal output module 201 and the second voltage signal output module 202 are the same as those of the first voltage signal output module 201 and the second voltage signal output module 202 described above, so they will not be described again. Please refer to the above contents for details.

[0105] In addition, on the pixel array 401 of the image sensor chip, red, green and blue primary color filters need to be added to each pixel unit.

[0106] Combine the following Figures 3 to 7 The working principle of this embodiment is described below.

[0107] First, the control unit 404 controls the pixel driving unit 402 to output a control signal to turn on the first transfer transistor TG1, the first reset transistor RST1, the second transfer transistor TG2 and the second reset transistor RST2 of the pixel unit, reset the first floating diffusion area FD1, the second floating diffusion area FD2 and the clamped photodiode, and discharge the residual charge in the clamped photodiode so that it meets the condition of complete exhaustion, and no photogenerated charge is generated when no modulated light signal is incident on the PPD.

[0108] Then, the control unit 404 controls the pixel driving unit 402 to output a control signal to disconnect the first transfer transistor TG1 , the first reset transistor RST1 , the second transfer transistor TG2 , and the second reset transistor RST2 , and the clamp photodiode PPD starts to accumulate charges.

[0109] The control signal sent to the first switch is set to have the same phase as the modulated light, and the control signal sent to the second switch is set to have a complementary phase to the control signal sent to the first switch.

[0110] Turn on the modulated light emission source to emit modulated light, turn on the first transfer transistor TG1 and the second transfer transistor TG2 through the phase relationship between the pulse signal of the modulated light and the control signal applied to the first transfer transistor TG1 and the second transfer transistor TG2, transfer the charges accumulated in the photodiode PPD to the first floating diffusion area FD1 and the second floating diffusion area FD2, and after the first transfer transistor TG1 and the second transfer transistor TG2 are turned off, turn on the first selection transistor SEL1 and read the voltage value of the first selection transistor SEL1.

[0111] Among them, when the two-tap two-phase method is used for measurement, only one integration is required. Specifically, after the photodiode PPD of the pixel unit receives the reflected light reflected back by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module 202 when the phase of the reflected light is 180°;

[0112] According to the formula: , the flight time of the modulated light is calculated, where To modulate light in one cycle The time when the internal level is high.

[0113] According to the formula: , calculate the image depth information of the object to be measured .

[0114] Furthermore, when the two-tap four-phase method is used for measurement, two integrations are required. Specifically, in the first integration stage, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module 202 when the phase of the reflected light is 180°; in the second integration stage, after the pixel unit receives the reflected light again, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS2 when the phase of the reflected light is 90°, and the voltage output by the second voltage signal output module 202 is obtained as the second voltage signal PS3 when the phase of the reflected light of the modulated light is 270°.

[0115] The readout unit 403 transmits the readout voltage signals PS0, PS1, PS2, and PS3 to the CPU / FPGA through the parallel port.

[0116] The calculation unit of CPU / FPGA is based on the formula: , the flight time of the modulated light is calculated, where To modulate the light round trip time, is the period of the modulated optical signal.

[0117] The CPU / FPGA computing unit is then based on the formula: , calculate the image depth information of the object to be measured .

[0118] Embodiment 4:

[0119] The present application proposes an imaging system, which includes the image sensor chip and the laser emitter as described above.

[0120] The imaging system of this embodiment can be applied to the fields of 3D imaging and gesture recognition.

[0121] Embodiment five:

[0122] The present application proposes a method for forming a pixel unit with a dual charge storage structure, the method comprising:

[0123] Provide a substrate 203;

[0124] A photodiode PPD is provided in the substrate 203 and is used to accumulate charges in response to reflected light incident on the photodiode PPD;

[0125] A first voltage signal output module 201 is provided, which is used to convert the charge accumulated in the photodiode PPD into a voltage signal, and comprises a first switch, wherein the control end of the first switch receives a control signal, the input end of the first switch is connected to the photodiode PPD, and the output end of the first switch outputs the voltage signal when the control end of the first switch receives the control signal; and

[0126] A second voltage signal output module 202 is provided, which is used to convert the charge accumulated in the photodiode PPD into a voltage signal, and includes a second switch, a control end of the second switch receives a control signal, an input end of the second switch is connected to the photodiode PPD, and an output end of the second switch outputs the voltage signal when the control end of the second switch receives the control signal;

[0127] Wherein, the control signal sent to the first switch is set to have the same phase as the modulated light, and the control signal sent to the second switch is set to be complementary to the phase of the control signal sent to the first switch, and the modulated light is emitted. When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module 202 when the phase of the reflected light is 180°;

[0128] According to the formula: , the flight time of the modulated light is calculated, where It is the time during which the modulated light level is high in one cycle.

[0129] When the two-tap four-phase method is used for measurement, after the photodiode PPD of the pixel unit receives the reflected light again, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS2 output by the first voltage signal output module 201 when the phase of the reflected light is 90°, and the voltage output by the second voltage signal output module 202 is obtained as the second voltage signal PS3 output by the second voltage signal output module 202 when the phase of the reflected light of the modulated light is 270°;

[0130] According to the formula: , the flight time of the modulated light is calculated, where is the round trip time of the modulated light, is the period of the modulated optical signal.

[0131] Embodiment six:

[0132] A depth information calculation method, the method comprising:

[0133] A pixel array 401 is provided, which includes the pixel units described above, or includes: a substrate 203;

[0134] a plurality of photodiodes PPD, the photodiodes PPD being disposed in the substrate 203 and being used to accumulate charges in response to reflected light incident on the photodiodes PPD,

[0135] A first voltage signal output module 201, which is used to convert the charge accumulated in the photodiode PPD into a voltage signal, and includes a first switch, a control end of the first switch receives a control signal, an input end of the first switch is connected to the photodiode PPD, and an output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and

[0136] The second voltage signal output module 202 is used to convert the charge accumulated in the photodiode PPD into a voltage signal, and includes a second switch, a control end of the second switch receives a control signal, an input end of the second switch is connected to the photodiode PPD, and an output end of the second switch outputs a second voltage signal when the control end of the second switch receives the control signal.

[0137] The photodiodes PPD form an array, and the photodiodes PPD share a first voltage signal output module 201 and a second voltage signal output module 202;

[0138] A pixel driving unit 402 is provided, which is used to output a control signal to control the operation of the pixel units in the pixel array 401, and is connected to the pixel array 401;

[0139] A readout unit 403 is provided, which is used to read and output a voltage signal output by a pixel unit in the pixel array 401, and is connected to the pixel array 401;

[0140] A control unit 404 is provided, which is connected to and controls the pixel array 401, the pixel driving unit 402 and the readout unit 403;

[0141] The system turns on the modulated light emission source to emit modulated light, the control unit 404 controls the pixel driving unit 402 to send a control signal to the first switch that is in the same phase as the modulated light, and the control signal sent to the second switch is complementary to the control signal sent to the first switch, and the length of time for each emission to be modulated is The control unit 404 controls the pixel driving unit 402 to output a control signal of the first switch of the first voltage signal output module 201 that is the same as the phase of the laser pulse, and controls the pixel driving unit 402 to output a control signal of the second switch of the second voltage signal output module 202 that is complementary to the phase of the laser pulse. When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS0 output by the first voltage signal output module 201 when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal output module 202 is obtained as the second voltage signal PS1 output by the second voltage signal output module 202 when the phase of the reflected light is 180°;

[0142] According to the formula: , the flight time of the modulated light is calculated, where is the round trip time of the modulated light, is the period of the modulated optical signal.

[0143] When the two-tap four-phase method is used for measurement, after the photodiode PPD of the pixel unit receives the reflected light again, the voltage output by the first voltage signal output module 201 is obtained as the first voltage signal PS2 output by the first voltage signal output module 201 when the phase of the reflected light is 90°, and the voltage output by the second voltage signal output module 202 is obtained as the second voltage signal PS3 output by the second voltage signal output module 202 when the phase of the reflected light of the modulated light is 270°;

[0144] According to the formula: , the flight time of the modulated light is calculated, where is the round trip time of the modulated light, is the period of the modulated optical signal.

[0145] Embodiment seven:

[0146] See also Figure 8 , the present application proposes a method for measuring image depth by an imaging system, comprising:

[0147] Step S701: configuring command parameters of the imaging system.

[0148] Before step S701, the method further includes the following steps: when the imaging system enters the initial state, it enters the reset state, during which all signals of the digital module are reset.

[0149] If it works under default conditions, you can skip all configurations and end initialization directly. If you need to change the configuration, you need to write the corresponding value into the register stack through the serial peripheral interface. After the configuration is completed, the initialization ends.

[0150] Step S702: Start the imaging system.

[0151] In step S702, it includes: after entering the idle state, using the serial peripheral interface to start the imaging system to enter the measurement state by inputting the corresponding command value. The measurement state consists of a depth mode and a grayscale mode, and the depth mode and grayscale mode working times are set by configuring the registers of the depth mode and grayscale mode working times.

[0152] Step S703: measuring the image depth information of the object to be measured according to the depth information measuring method described in the sixth embodiment according to the configured command parameters.

[0153] For the specific depth information measurement method, please refer to the description of the sixth embodiment, which will not be described here.

[0154] After step S703, that is, when the depth working times are satisfied, the operation will be automatically switched to the grayscale mode.

[0155] Step S704: measuring the image grayscale of the object to be measured according to the configured command parameters.

[0156] After the grayscale mode in step S704 ends, it is determined whether to perform continuous image acquisition or stop working according to the detection bit preset in the register.

[0157] Step S705: Obtain the measured image depth value and image grayscale value, and perform calculations.

[0158] After step S705, the method further includes step S706: collecting the temperature of the image sensor, and reading the image depth value and the image grayscale value through the parallel port to the CPU / FPGA outside the chip for calculation.

[0159] The pixel unit in this embodiment refers to the pixel unit described in the above second and third embodiments, and will not be described again.

[0160] The beneficial effect of the present application is that: the present application sets a first voltage signal output module and a second voltage signal output module in a pixel unit structure, and the first voltage signal output module and the second voltage signal output module can convert the charge accumulated by the photodiode in response to the reflected light into a voltage signal after receiving the control signal, and then by setting the phase relationship between the first switch of the first voltage signal output module and the second switch of the second voltage signal output module and the modulated light, after receiving the reflected light, the voltage signals output by the first voltage signal output module and the second voltage signal output module at different phases are obtained, and the flight time of the modulated light can be calculated, so that the reaction speed of the pixel unit can be improved, and different distances can be measured with relatively high measurement accuracy, which meets the requirements of high-precision industries such as safety detection and industrial control, making the product more widely applicable.

[0161] Those skilled in the art will appreciate that all or part of the steps of the various methods in the above-mentioned implementations may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which may include: a read-only memory, a random access memory, a disk or an optical disk, etc.

[0162] The above contents are further detailed descriptions of the present application in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the inventive concept of the present application.

Claims

1. A pixel unit having a dual charge storage structure, characterized in that: The pixel unit comprises: substrate; a photodiode disposed within the substrate and configured to accumulate charge in response to reflected light incident on the photodiode; A first voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and comprises a first switch, wherein a control end of the first switch receives a control signal, an input end of the first switch is connected to the photodiode, and an output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and A second voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and comprises a second switch, wherein a control end of the second switch receives a control signal, an input end of the second switch is connected to the photodiode, and an output end of the second switch outputs a second voltage signal when the control end of the second switch receives the control signal; Wherein, the control signal sent to the first switch is set to have the same phase as the modulated light, and the control signal sent to the second switch is set to be complementary to the phase of the control signal sent to the first switch, and the modulated light is emitted to the object to be measured. When the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal module is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal module is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; According to the formula: , the flight time of the modulated light is calculated, where is the time during which the level of the modulated light is high in one cycle; The photodiode is arranged at the center of the substrate, the first switch of the first voltage signal output module is a first transmission transistor, the first transmission transistor is arranged in the substrate and arranged on one side of the photodiode, the first transmission transistor is coupled with the photodiode to output the charge accumulated by the photodiode as a voltage signal, the second switch of the second voltage signal output module is a second transmission transistor, the second transmission transistor is arranged in the substrate and symmetrically arranged on the other side of the photodiode of the first transmission transistor, the second transmission transistor is coupled with the photodiode to output the charge accumulated by the photodiode as a voltage signal; The first voltage signal output module also includes: A first floating diffusion region is disposed in the substrate and on a side of the first transfer transistor away from the photodiode, wherein the first transfer transistor transfers the charge accumulated in the photodiode to the first floating diffusion region for storage; A first reset transistor, which is arranged in the substrate and coupled to the photodiode, and is used to reset the charge stored in the first floating diffusion region; a first source follower transistor, a control terminal of which is connected to the first floating diffusion region, and an input terminal of which is connected to the first reset transistor; and A first gating transistor, an input end of which is connected to the output end of the first source follower transistor, and an output end of the first gating transistor outputs the voltage signal; The second voltage signal output module further includes: A second floating diffusion region is disposed in the substrate and on a side of the second transfer transistor away from the photodiode, wherein the second transfer transistor transfers the charge of the photodiode to the second floating diffusion region for storage; A second reset transistor, which is arranged on the substrate and coupled to the photodiode, and is used to reset the charge stored in the second floating diffusion region; a second source follower transistor, a control terminal of which is connected to the second floating diffusion region, and an input terminal of which is connected to the second reset transistor; and a second gating transistor, an input end of which is connected to the output end of the second source follower transistor, and an output end of the second gating transistor outputs the voltage signal; The pixel unit further comprises a deep trench isolation structure, which is used to isolate active areas of adjacent pixel units and is arranged in the substrate around the periphery of the pixel unit; The pixel unit further includes a light shielding plate, which is used to block light from irradiating onto areas other than the photodiode and shield electrical interference, and is disposed on the upper surfaces of the first voltage signal output module and the second voltage signal output module.

2. The pixel unit according to claim 1, characterized in that: When the two-tap four-phase method is used for measurement, after the photodiode of the pixel unit receives the reflected light again, the voltage output by the first voltage signal module is obtained as the first voltage signal PS2 output by the first voltage signal output module when the phase of the reflected light is 90°, and the voltage output by the second voltage signal module is obtained as the second voltage signal PS3 output by the second voltage signal output module when the phase of the reflected light of the modulated light is 270°; According to the formula: , the flight time of the modulated light is calculated, where is the round trip time of the modulated light, is the period of the modulated optical signal.

3. The pixel unit according to claim 1, characterized in that: The pixel unit also includes a microlens, which is used to gather light and irradiate it onto the photosensitive area of ​​the photodiode, and is arranged on the upper surface of the pixel unit.

4. An image sensor chip with a dual charge storage structure, characterized in that: The image sensor chip comprises: A pixel array comprising a plurality of pixel units according to claim 1, or comprising: substrate; a plurality of photodiodes disposed within the substrate and configured to accumulate charge in response to reflected light incident on the photodiodes, A first voltage signal output module, which is used to convert the charge accumulated in the photodiode into a voltage signal, and comprises a first switch, wherein a control end of the first switch receives a control signal, an input end of the first switch is connected to the photodiode, and an output end of the first switch outputs a first voltage signal when the control end of the first switch receives the control signal; and The second voltage signal output module is used to convert the charge accumulated in the photodiode into a voltage signal, and comprises a second switch, wherein the control end of the second switch receives a control signal, the input end of the second switch is connected to the photodiode, and the output end of the second switch outputs a second voltage signal when the control end of the second switch receives the control signal. Wherein, the photodiodes form an array, and the photodiodes share a first voltage signal output module and a second voltage signal output module; A pixel driving unit, which is used to output a control signal to control the operation of the pixel units in the pixel array, and is connected to the pixel array; A readout unit, which is used to read and output a voltage signal output by a pixel unit in the pixel array, and is connected to the pixel array; A control unit connected to and controlling the pixel array, the pixel driving unit and the readout unit; Wherein, the modulated light emission source is turned on to send modulated light, the control unit controls the control signal sent by the pixel driving unit to the first switch to have the same phase as the modulated light, and the control signal sent to the second switch is complementary to the control signal sent to the first switch in phase, and when the two-tap two-phase method is used for measurement, after the pixel unit receives the reflected light reflected by the object to be measured after receiving the modulated light, the voltage output by the first voltage signal module is obtained as the first voltage signal PS0 output by the first voltage signal output module when the phase of the reflected light is 0°, and the voltage signal output by the second voltage signal module is obtained as the second voltage signal PS1 output by the second voltage signal output module when the phase of the reflected light is 180°; According to the formula: , the flight time of the modulated light is calculated, where is the time during which the level of the modulated light is high in one cycle; The photodiode is arranged at the center of the substrate, the first switch of the first voltage signal output module is a first transmission transistor, the first transmission transistor is arranged in the substrate and arranged on one side of the photodiode, the first transmission transistor is coupled with the photodiode to output the charge accumulated by the photodiode as a voltage signal, the second switch of the second voltage signal output module is a second transmission transistor, the second transmission transistor is arranged in the substrate and symmetrically arranged on the other side of the photodiode of the first transmission transistor, the second transmission transistor is coupled with the photodiode to output the charge accumulated by the photodiode as a voltage signal; The first voltage signal output module also includes: A first floating diffusion region is disposed in the substrate and on a side of the first transfer transistor away from the photodiode, wherein the first transfer transistor transfers the charge accumulated in the photodiode to the first floating diffusion region for storage; A first reset transistor, which is arranged in the substrate and coupled to the photodiode, and is used to reset the charge stored in the first floating diffusion region; a first source follower transistor, a control terminal of which is connected to the first floating diffusion region, and an input terminal of which is connected to the first reset transistor; and A first gating transistor, an input end of which is connected to the output end of the first source follower transistor, and an output end of the first gating transistor outputs the voltage signal; The second voltage signal output module further includes: A second floating diffusion region is disposed in the substrate and on a side of the second transfer transistor away from the photodiode, wherein the second transfer transistor transfers the charge of the photodiode to the second floating diffusion region for storage; A second reset transistor, which is arranged on the substrate and coupled to the photodiode, and is used to reset the charge stored in the second floating diffusion region; a second source follower transistor, a control terminal of which is connected to the second floating diffusion region, and an input terminal of which is connected to the second reset transistor; and A second gating transistor, an input end of which is connected to the output end of the second source follower transistor, and an output end of the second gating transistor outputs the voltage signal; The pixel unit further comprises a deep trench isolation structure, which is used to isolate active areas of adjacent pixel units and is arranged in the substrate around the periphery of the pixel unit; The pixel unit further includes a light shielding plate, which is used to block light from irradiating onto areas other than the photodiode and shield electrical interference, and is disposed on the upper surfaces of the first voltage signal output module and the second voltage signal output module.

5. The image sensor chip according to claim 4, characterized in that: When the two-tap four-phase method is used for measurement, after the photodiode of the pixel unit receives the reflected light again, the voltage output by the first voltage signal module is obtained as the first voltage signal PS2 output by the first voltage signal output module when the phase of the reflected light is 90°, and the voltage output by the second voltage signal module is obtained as the second voltage signal PS3 output by the second voltage signal output module when the phase of the reflected light of the modulated light is 270°; According to the formula: , the flight time of the modulated light is calculated, where is the round trip time of the modulated light, is the period of the modulated optical signal.

6. The image sensor chip according to claim 5, characterized in that: The pixel unit also includes a microlens, which is used to gather light and irradiate it onto the photosensitive area of ​​the photodiode, and is arranged on the upper surface of the pixel unit.

7. An imaging system, characterized in that: It comprises the image sensor chip as described in any one of claims 4 to 6 and a laser emitter.

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