A photoelectrically tunable vertical charge transfer device, array, and method

Abstract

This invention discloses a photoelectrically tunable vertical charge transfer device, array, and method. The vertical charge transfer device unit includes five composite dielectric gate MOSFETs, four of which are used to collect read signals (i.e., read transistors). These four read transistors are arranged in a square structure, with a shared composite dielectric gate MOSFET (write transistor) placed in the center. The structure of the composite dielectric gate MOSFET consists of a bottom insulating dielectric layer, a floating gate, a top insulating dielectric layer, and a control gate sequentially disposed above a substrate. The five composite dielectric gate MOSFETs share the floating gate and the control gate. This invention overcomes the limitation of existing silicon-based image sensors that can only respond in the visible light band. By selecting photodiodes with different response bands as information sources to modulate the write transistor in the circuit structure, multi-spectral imaging functionality can be achieved.

Description

Technical Field

[0001] This invention relates to an integrated sensing, storage, and computing device, which is a novel vertical charge transfer device based on a composite dielectric gate structure that is photosensitive, storage, and computing integrated into one device, belonging to the field of sensing, storage, and computing devices. Background Technology

[0002] Traditional image processing systems mostly employ a structure where the photosensitive unit and processing unit are separate. First, the image sensor, composed of the photosensitive unit, converts optical signals into electrical signals, which are then sent to the processing unit for signal processing and other operations. The mainstream image sensors include CCD and CIS (CMOS Image Sensor). With the continuous improvement of CMOS manufacturing processes, CIS has begun to replace CCD in more and more fields, occupying a dominant market position. However, CCD has extremely complex control timing and voltage requirements, slow operating speed, and is difficult to integrate; CIS has a complex structure, low fill factor, and small full-well charge.

[0003] Today, with the continuous improvement of image frame rates and resolutions, higher demands are placed on the computing power of systems. Therefore, many researchers have begun to attempt to integrate data preprocessing into the photosensitive unit, forming a structure that combines the photosensitive unit and the processing unit, thereby reducing the processing pressure on subsequent systems and improving the overall performance of the system. Summary of the Invention

[0004] Currently, the image sensor industry lacks device-level designs based on integrated sensing, storage, and computing. This invention aims to organically integrate photosensitive, storage, and computation functions to provide an opto-tunable vertical charge transfer device and array based on a composite dielectric gate structure. Another objective of this invention is to provide a method for operating the aforementioned device and array.

[0005] The technical solution adopted by the device of the present invention is as follows:

[0006] A photoelectrically tunable vertical charge transfer device includes five composite dielectric gate MOSFETs, four of which are used to collect read signals (i.e., read transistors). These four read transistors are arranged in a square structure, with a shared composite dielectric gate MOSFET for writing (i.e., write transistor) placed in the center. The structure of the composite dielectric gate MOSFET is that a bottom insulating dielectric layer, a floating gate, a top insulating dielectric layer, and a control gate are sequentially arranged above a substrate. The five composite dielectric gate MOSFETs share the floating gate and the control gate.

[0007] This invention provides an operating method for the above-mentioned vertical charge transfer device, the operating method for optical modulation comprising the following steps:

[0008] (1) Weight writing: The weight is written by adjusting the number of read tubes that are turned on in the unit structure;

[0009] (2) Reset of photoelectrons: Applying pressure makes the control gates of the four read tubes and the substrate in a zero bias state, eliminating the depletion region in the substrate below the bottom insulating dielectric layer, and completing the reset of photoelectrons;

[0010] (3) Generation of photoelectrons: When visible light from the outside is incident on the substrate, electron-hole pairs are generated;

[0011] (4) Collection of photoelectrons: Applying pressure causes the control gates of the four readout tubes to be in a forward biased state with the substrate, forming a depletion region in the substrate below the bottom insulating dielectric layer. The photogenerated electron-hole pairs generated in the previous step are separated under the action of the electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0012] (5) Signal reading: Based on the previous step, connect the drain of the four reading tubes to a forward bias signal to read the output current of the device.

[0013] Furthermore, the present invention provides an operation method for the above-mentioned vertical charge transfer device, the operation method for optical modulation comprising the following steps:

[0014] (1) Weight writing: The weight is written by adjusting the number of read tubes that are turned on in the unit structure;

[0015] (2) Reset: Applying pressure makes the control gate and substrate of all composite dielectric gate MOSFET devices in a zero bias state, eliminating the depletion region in the substrate below the bottom insulating dielectric layer, and completing the reset of the optoelectronics;

[0016] (3) Signal collection: The light signal is converted into a current signal by the photosensitive element and passed into the active region of the write tube. At the same time, the voltage is applied so that the control gates of the other four read tubes are in a forward biased state with the substrate, forming a depletion region in the substrate below the bottom insulating dielectric layer. The potential change of the write tube is mapped to the depletion region of the other four read tubes to form an electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0017] (4) Signal reading: Based on the previous step, connect the drain of the four reading transistors to a forward bias signal to read the output current of the device.

[0018] The present invention also provides an opto-tunable vertical charge transfer device array, wherein the vertical charge transfer device units are arranged in an array using a NOR architecture: for an N-row M-column array, there are 4N word lines WL signals, which are respectively connected to the gates of four read transistors in the N vertical charge transfer devices; there are M source lines SL signals, which are respectively connected to the sources of four read transistors in the same column of the M vertical charge transfer devices; there are M bit lines BL signals, which are respectively connected to the drains of four read transistors in the same column of the M vertical charge transfer devices; and N×M write control signals CS, which realize the control of the array working area.

[0019] Furthermore, the present invention provides an operation method for the above-mentioned array, the operation method for optical modulation comprising the following steps:

[0020] (1) Weight writing: Adjust the signal applied on the word line WL to control the number of read tubes that are turned on, and complete the weight writing;

[0021] (2) Reset of photoelectronics: Adjust the signal applied on word line WL to make the gate and substrate in a zero bias state, thereby eliminating the depletion region in the substrate below the bottom insulating dielectric layer and completing the reset of photoelectronics;

[0022] (3) Generation of photoelectrons: An external light source is incident on the substrate, generating electron-hole pairs;

[0023] (4) Photoelectron collection: Adjust the signal applied to the word line WL to make the gate and the substrate in a forward bias state, forming a depletion region in the substrate below the bottom insulating dielectric layer. The photogenerated electron-hole pairs generated in the previous step are separated under the action of the electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0024] (5) Signal readout: Based on the previous step, the source line SL is grounded and the bit line BL is connected to the positive bias signal to read the output current of the device array.

[0025] Furthermore, the present invention provides an operation method for the above-described array, wherein the operation method for electrical modulation includes the following steps:

[0026] (1) Weight writing: Adjust the signal applied on the word line WL to control the number of read tubes that are turned on, and complete the weight writing;

[0027] (2) Reset: Adjust the signal applied on the word line WL to make the gate and substrate in a zero bias state, thereby eliminating the depletion region in the substrate below the bottom insulating dielectric layer and completing the reset;

[0028] (3) Signal collection: The light signal is converted into a current signal by the photosensitive element and passed into the active region of the write tube. The signal applied on the control signal CS is adjusted to turn on the write tube. At the same time, the signal applied on the word line WL is adjusted to make the gate of the four read tubes and the substrate in a forward bias state, forming a depletion region in the substrate below the bottom insulating dielectric layer. The potential change of the write tube is mapped to the depletion region of the other four read tubes to form an electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0029] (4) Signal readout: Based on the previous step, the source line SL is grounded and the bit line BL is connected to the positive bias signal to read the output current of the device array.

[0030] The device of this invention overcomes the limitation of existing silicon-based image sensors that can only respond in the visible light band. By selecting photodiodes with different response bands as photosensitive elements and information sources in the circuit structure to modulate the write tube, multi-spectral imaging can be achieved. Furthermore, by controlling different voltage application methods of multiple composite dielectric gate MOSFET devices within a single repeating unit structure, different weighting methods can be implemented. Weighted calculations of data are completed during signal readout, reducing the amount of data at the source and effectively lowering the computational power requirements and power consumption of subsequent image processing. Attached Figure Description

[0031] Figure 1 This is a device structure diagram of the present invention;

[0032] Figure 2 This is the AA' cross-sectional view of the composite dielectric gate MOSFET device in the present invention;

[0033] Figure 3 This is the equivalent circuit diagram of the device of the present invention in actual use;

[0034] Figure 4 This is a diagram of the array structure of the present invention. Detailed Implementation

[0035] This invention provides a photoelectrically tunable vertical charge transfer device, the structure of which is as follows: Figure 1 As shown, the basic composite dielectric gate MOSFET device is a prerequisite for functional realization. In the figure, C represents the charge accumulation region and T represents the transistor region. The composite dielectric gate MOSFET device has a bottom insulating dielectric layer, a floating gate, a top insulating dielectric layer, and a control gate sequentially arranged above the substrate. Its AA' cross-sectional structure is shown in the figure. Figure 2As shown, regions C and T are connected via a floating gate and a control gate. When electron-hole pairs are generated in region C, the potential mapped onto the floating gate adjusts the transistor threshold in region T. Four basic composite dielectric gate MOSFETs are arranged in a square structure (for reading signals, hereinafter referred to as "read transistors"), with a shared composite dielectric gate MOSFET for writing (hereinafter referred to as "write transistors") placed in the middle. These five devices share the floating gate and the control gate.

[0036] The equivalent circuit of the photoelectric tunable vertical charge transfer device is as follows: Figure 3 As shown, WL represents the word line, SL represents the source line, BL represents the bit line, and CS represents the write transistor gate control signal. The five composite dielectric gate MOSFETs corresponding to CS and WL1-4 all operate in the linear region. The currents of the four devices on the right are I... D1 I D2 I D3 and I D4 Assume the original threshold voltage of the composite dielectric gate MOSFET device is V. TH0 The stored photoelectric signal is V p Then its final threshold voltage is V TH =V TH0 +V p The signal applied to the control gate is V. WL The signal applied to the drain is V. B The signal at the source is V S Therefore, we can conclude that:

[0037] I D =K·(V WL -V TH )·(V B -V S (1)

[0038] Where K is the transconductance coefficient of the composite dielectric gate MOSFET device. Therefore, this device can perform weighted multiplication and addition operations on optical signals of different wavelengths using four read transistors and one write transistor.

[0039] Based on this Figure 4 An N x M device array architecture is presented, consisting of 4N word lines (WL signals) connected to the gates of the four read transistors of N opto-tunable vertical charge transfer devices; M source lines (SL signals) connected to the sources of the read transistors in the same column of the M opto-tunable vertical charge transfer devices; M bit lines (BL signals) connected to the drains of the read transistors in the same column of the M opto-tunable vertical charge transfer devices; and N × M write gate control signals (CS signals) for controlling the array's working area.

[0040] Example 1

[0041] This embodiment presents a visible light weighted calculation method based on the aforementioned vertical charge transfer device. The specific optical modulation scheme is as follows:

[0042] (1) Weight writing: by adjusting Figure 3 The number of four read tubes activated in the structure completes the writing of the corresponding weight. Specifically, the device's WL is connected to 5V, the substrate to -3V, SL to 0V, and BL to 3V to indicate that the device is activated.

[0043] (2) Reset of photoelectrons: WL and substrate are simultaneously connected to -3V to eliminate the depletion region in the substrate below the bottom insulating dielectric layer of the read tube, thus completing the reset of photoelectrons;

[0044] (3) Generation of photoelectrons: When visible light from the outside is incident on the substrate, electron-hole pairs are generated;

[0045] (4) Photoelectron collection: WL is connected to 0V, and the substrate is connected to -3V. A depletion region is formed in the substrate below the bottom insulating dielectric layer of the four read tubes. The photogenerated electron-hole pairs generated in the previous step are separated under the action of the electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0046] (5) Signal reading: Based on the previous step, connect SL to 0V, WL to 5V, and BL to 0.2V to read the output current of the device.

[0047] Therefore, the device completes the multiplication calculation of the optical signal during the readout.

[0048] Example 2

[0049] This embodiment presents a method for infrared light weighting calculation based on the aforementioned vertical charge transfer device. The difference from Embodiment 1 is that... Figure 3 The photodiode used is a photodiode that responds to the infrared light band. Its specific electrical modulation scheme is as follows:

[0050] (1) Weight writing: by adjusting Figure 3 The number of read tubes activated in the structure completes the writing of the corresponding weight. Specifically, WL of the device is connected to 5V, the substrate is connected to -3V, SL is connected to 0V, and BL is connected to 3V to indicate that the device is activated.

[0051] (2) Reset: WL and substrate are simultaneously connected to -3V to eliminate the depletion region in the substrate below the bottom insulating dielectric layer of the composite dielectric gate MOSFET device and complete the reset.

[0052] (3) Signal collection: The infrared light signal is converted into a current signal by the photodiode corresponding to the corresponding band and passed into the active region of the write tube. CS is connected to 5V to turn on the write tube; WL is connected to 0V and the substrate is connected to -3V. A depletion region is formed in the substrate below the bottom insulating dielectric layer of the read tube. The potential change of the write tube is mapped to the depletion region of the other four read tubes to form an electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0053] (4) Signal reading: Based on the previous step, connect SL to 0V, WL to 5V, and BL to 0.2V to read the output current of the device.

[0054] Therefore, the device completes the multiplication calculation of the optical signal during the readout.

[0055] Example 3

[0056] This embodiment presents a visible light weighted calculation method based on the above-mentioned device array. Figure 3 and Figure 4 The photodiode used is a photodiode that responds to the visible light band. Assume... Figure 4 The array size is 4×4, i.e., N=4, M=4. Let M be the denoted number of each photoelectric tunable vertical charge transfer device in the array. i，j Where i represents the row and j represents the column, the numbering starts from the top left corner, i.e., the device numbered in the top left corner is M. 1，1 The device mentioned in the lower right corner is M. 4，4 Let M be the name of each composite dielectric gate MOSFET in each photoelectric tunable vertical charge transfer device. i，j <p, q>, where i and j are the positions of photoelectric tunable vertical charge transfer devices in the array, and p and q are the positions of composite dielectric gate MOSFET devices, numbered starting from the top left corner, i.e., the device in the top left corner is numbered M. i，j <1,1>, the device mentioned in the lower right corner is M. i，j <2,2>. Assume the original threshold voltage of each composite dielectric gate MOSFET is V. THO The threshold voltage shift caused by photoelectrons is V. opt ,Right now:

[0057]

[0058] Assume the signal needs to be weighted by different weights w within the range of 0 to 4. i，j The weighted calculation, the result x i，j for:

[0059]

[0060] Implementing this calculation in a conventional approach requires acquiring image signals. Then, NM multiplication and addition operations are performed. If the scheme described in this invention is adopted, these operations can be omitted, and the energy savings are considerable when the array size is large. The specific scheme for optical modulation is as follows:

[0061] (1) Weight writing: by adjusting the structure of a single repeating unit ( Figure 3 The number of read tubes turned on in the structure completes the writing of the corresponding weight. Specifically, the device's WL is connected to 5V, the substrate to -3V, SL to 0V, and BL to 3V to indicate that the device is turned on.

[0062] (2) Reset of photoelectrons: WL and substrate are simultaneously connected to -3V to eliminate the depletion region in the substrate below the bottom insulating dielectric layer of the read tube, thus completing the reset of photoelectrons;

[0063] (3) Generation of photoelectrons: When visible light from the outside is incident on the substrate, electron-hole pairs are generated;

[0064] (4) Collection of photoelectrons: WL is connected to 0V and the substrate is connected to -3V. A depletion region is formed in the substrate below the bottom insulating dielectric layer of the read tube. The photogenerated electron-hole pairs generated in the previous step are separated under the action of the electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0065] (5) Signal reading: Based on the previous step, connect SL to 0V, WL to 5V, and BL to 0.2V to read the output current of the array device.

[0066] Therefore, the array completes the weighted calculation during the readout, saving NM multiplication and addition operations.

[0067] Example 4

[0068] This embodiment presents a method for infrared light weighted calculation based on the above-described array. The difference from Embodiment 3 is that... Figure 3 and Figure 4 The photodiode used is a photodiode that responds to the infrared light band. Its specific electrical modulation scheme is as follows:

[0069] (1) Weight writing: The corresponding weight is written by adjusting the number of read tubes turned on in a single repeating unit structure. Specifically, the device's WL is connected to 5V, the substrate is connected to -3V, SL is connected to 0V, and BL is connected to 3V to indicate that the device is turned on.

[0070] (2) Reset: WL and substrate are simultaneously connected to -3V to eliminate the depletion region in the substrate below the bottom insulating dielectric layer of the composite dielectric gate MOSFET device and complete the reset.

[0071] (3) Signal collection: The infrared light signal is converted into a current signal by the photodiode corresponding to the corresponding band and passed into the active region of the write tube. CS is connected to 5V to turn on the write tube; WL is connected to 0V and the substrate is connected to -3V. A depletion region is formed in the substrate below the bottom insulating dielectric layer of the read tube. The potential change of the write tube is mapped to the depletion region of the read tube to form an electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate.

[0072] (4) Signal reading: Based on the previous step, connect SL to 0V, WL to 5V, and BL to 0.2V to read the output current of the device array.

[0073] Therefore, the array completes the weighted calculation during the readout, saving NM multiplication and addition operations.

Claims

1. A photoelectrically tunable vertical charge transfer device, characterized in that, This vertical charge transfer device unit includes five composite dielectric gate MOSFETs, four of which are used to collect read signals (i.e., read transistors). These four read transistors are arranged in a square structure, with a shared composite dielectric gate MOSFET (i.e., write transistor) placed in the middle. The structure of the composite dielectric gate MOSFET is that a bottom insulating dielectric layer, a floating gate, a top insulating dielectric layer, and a control gate are sequentially arranged above the substrate. The five composite dielectric gate MOSFETs share the floating gate and the control gate. The operation method of the vertical charge transfer device unit for optical modulation includes the following steps: (1) Weight writing: The weight is written by adjusting the number of read tubes that are turned on in the unit structure; (2) Reset of photoelectrons: Applying pressure makes the control gates of the four readout tubes and the substrate in a zero bias state, eliminating the depletion region in the substrate below the bottom insulating dielectric layer, and completing the reset of photoelectrons; (3) Generation of photoelectrons: When visible light from the outside is incident on the substrate, electron-hole pairs are generated; (4) Collection of photoelectrons: Applying pressure causes the control gates of the four readout tubes to be in a forward biased state with the substrate, forming a depletion region in the substrate below the bottom insulating dielectric layer. The photogenerated electron-hole pairs generated in the previous step are separated under the action of the electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate. (5) Signal reading: Based on the previous step, connect the drain of the four reading transistors to a forward bias signal to read the output current of the device; The operation method of the vertical charge transfer type device unit for electrical modulation includes the following steps: (1) Weight writing: The weight is written by adjusting the number of read tubes that are turned on in the unit structure; (2) Reset: Applying pressure makes the control gate and substrate of all composite dielectric gate MOSFET devices in a zero bias state, eliminating the depletion region in the substrate below the bottom insulating dielectric layer, and completing the reset of the optoelectronics; (3) Signal collection: The light signal is converted into a current signal by the photosensitive element and passed into the active region of the write tube. At the same time, the voltage is applied so that the control gates of the other four read tubes are in a forward bias state with the substrate, forming a depletion region in the substrate below the bottom insulating dielectric layer. The potential change of the write tube is mapped to the depletion region of the other four read tubes to form an electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate. (4) Signal reading: Based on the previous step, connect the drain of the four reading tubes to a forward bias signal to read the output current of the device.

2. The photoelectrically tunable vertical charge transfer device array as described in claim 1, characterized in that, The vertical charge transfer device units are arrayed using a NOR architecture. For an N x M array, there are 4N word lines (WL) connected to the gates of four read transistors in the N vertical charge transfer devices; M source lines (SL) connected to the sources of four read transistors in the same column of the M vertical charge transfer devices; M bit lines (BL) connected to the drains of four read transistors in the same column of the M vertical charge transfer devices; and N × M write control signals (CS) to control the array's working area.

3. The operation method of the photoelectric tunable vertical charge transfer device array as described in claim 2, characterized in that, The operation method for optical modulation includes the following steps: (1) Weight writing: Adjust the signal applied on the word line WL to control the number of read tubes that are turned on, and complete the weight writing; (2) Reset of photoelectrons: Adjust the signal applied on the word line WL to make the gate and the substrate in a zero bias state, thereby eliminating the depletion region in the substrate below the bottom insulating dielectric layer and completing the reset of photoelectrons; (3) Generation of photoelectrons: An external light source is incident on the substrate, generating electron-hole pairs; (4) Photoelectron collection: Adjust the signal applied to the word line WL to make the gate and the substrate in a forward bias state, forming a depletion region in the substrate below the bottom insulating dielectric layer. The photogenerated electron-hole pairs generated in the previous step are separated under the action of the electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate. (5) Signal readout: Based on the previous step, the source line SL is grounded and the bit line BL is connected to the positive bias signal to read the output current of the device array.

4. The operation method of the photoelectric tunable vertical charge transfer device array according to claim 2, characterized in that, The operating method for electrical modulation includes the following steps: (1) Weight writing: Adjust the signal applied on the word line WL to control the number of read tubes that are turned on, and complete the weight writing; (2) Reset: Adjust the signal applied on the word line WL to make the gate and substrate in a zero bias state, thereby eliminating the depletion region in the substrate below the bottom insulating dielectric layer and completing the reset; (3) Signal collection: The light signal is converted into a current signal by the photosensitive element and passed into the active region of the write tube. The signal applied on the control signal CS is adjusted to turn on the write tube. At the same time, the signal applied on the word line WL is adjusted to make the gate of the four read tubes and the substrate in a forward bias state, forming a depletion region in the substrate below the bottom insulating dielectric layer. The potential change of the write tube is mapped to the depletion region of the other four read tubes to form an electric field. Electrons are swept into the depletion region in the substrate below the bottom insulating dielectric layer, and holes are swept out of the substrate. (4) Signal reading: Based on the previous step, the source line SL is grounded and the bit line BL is connected to the positive bias signal to read the output current of the device array.

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