CN212182327U - Photoelectric sensor, random-readable active pixel circuit, image sensor, and camera device - Google Patents

Abstract

The utility model provides a photoelectric sensor, an active pixel circuit that can be read randomly, an image sensor and a camera device. The photoelectric sensor includes a doped area, a substrate, a doped source area, a doped drain area and two isolation areas; the doped area is arranged on the bottom surface of the substrate to form a photodiode with the substrate; and the doped area is formed with a photodiode The cathode is used to connect the positive voltage to make the photodiode work in the reverse biased region; the doped source region and the doped drain region are arranged at intervals on the top of the substrate to form a field effect transistor with the substrate; the top of the doped source region A source electrode is formed on the surface, and a drain electrode is formed on the top surface of the doped drain region; the two isolation regions are respectively located on opposite sides of the substrate, and extend from the doped source region and the doped drain region to the doped region from top to bottom respectively; The top surface of the substrate is sequentially formed with a gate insulating layer and a gate which are arranged between the doped source region and the doped drain region from bottom to top; Response range mode or high gain mode.

Description

Photoelectric Sensors, Randomly Readable Active Pixel Circuits, Image Sensors and Cameras device

technical field

The utility model relates to the field of electronic technology, in particular to a photoelectric sensor, an active pixel circuit that can be read randomly, an image sensor and a camera device.

Background technique

Phototransistor is a commonly used integrated photoelectric sensor, which includes photoelectric sensor and photocurrent amplification. The traditional phototransistor is prepared by bipolar process and Front Side Illumination (FSI), because the incident light needs to pass through the passivation layer, the interconnect insulation layer and the metal wiring layer to reach the photosensitive area and be absorbed. During this process, the light will be lost due to reflection by insulating media or metals, or refracted through multiple layers of insulating media to change the optical path. These factors will reduce the quantum efficiency.

Besides, as shown in FIG. 1 and FIG. 2 , the traditional phototransistor can be either NPN type or PNP type. When the phototransistor is applied, the collector c1 of the phototransistor is connected to a fixed positive potential VDD, the emitter is grounded, and the base b1 is suspended for light-sensing. When the light L is irradiated on the base, a photocurrent is generated between the base b1 and the collector c1, and is amplified by the phototransistor to generate a current gain. However, compared with CMOS devices, traditional phototransistors are larger in size and incompatible with CMOS technology, so they cannot be used in high-resolution image sensors.

Utility model content

Based on this, in order to solve the problems that the phototransistor has low quantum efficiency, large volume, and cannot be used in image sensors, the present invention provides a photoelectric sensor, a random-read active pixel circuit, an image sensor and a camera device.

According to the first aspect of the embodiments of the present invention, the present invention provides a photoelectric sensor, which includes a doped region, a substrate, a doped source region, a doped drain region and two isolation regions;

The doped region is arranged on the bottom surface of the substrate to form a photodiode with the substrate; and the doped region is formed with a cathode of the photodiode, and the cathode is used to connect a positive voltage to make the photodiode work in a reverse biased region ;

The doped source region and the doped drain region are arranged at intervals on the top of the substrate to form a field effect transistor with the substrate; a source electrode is formed on the top surface of the doped source region, and the doped drain region A drain is formed on the top surface of the region;

The two isolation regions are located on opposite sides of the substrate, respectively, and extend from the doped source region and the doped drain region to the doped region from top to bottom, so as to isolate adjacent pixels or adjacent sensors;

The top surface of the substrate is sequentially formed with a gate insulating layer and a gate disposed between the doped source region and the doped drain region from bottom to top; the gate is used to connect a voltage to select the operation of the field effect transistor Status is in wide dynamic range mode or high gain mode.

Compared with the prior art, the photoelectric sensor of the present invention has at least the following beneficial technical effects:

The utility model forms a doped source region, a doped drain region, a gate insulating layer and a gate on the top surface of a substrate, and forms a doped region and a cathode on the bottom surface of the substrate to form a common substrate. Back-illuminated integrated photosensors of photodiodes and field effect transistors. Therefore, the advantages of the back-illuminated type and the above structure can be used to solve the technical problems that the phototransistor in the related art has low quantum efficiency, large volume, and cannot be applied to image sensors. It can also be combined with the preparation of back-illuminated CMOS image sensors. process compatible and can be fabricated into small-sized devices for use in image sensors. In addition, in subsequent applications, photosensitive devices required for the integration of multiple photosensors may be applied, such as image sensors or cameras or display devices, but not limited thereto. In this way, a plurality of photoelectric sensors are generally arranged in an array, so there must be a situation where the photoelectric sensors are arranged adjacently, and a certain amount of crosstalk will be generated between the adjacent photoelectric sensors. Therefore, by arranging the two isolation regions, adjacent pixels or adjacent sensors can be isolated to avoid crosstalk between adjacent pixels or adjacent sensors.

Optionally, the cathode is formed by an electrode layer plated on the bottom surface of the doped region. The arrangement here is beneficial to reduce the volume of the entire photoelectric sensor and increase the photosensitive area of the photodiode to a certain extent.

Optionally, the electrode layer is a transparent electrode layer. By setting it here, it is beneficial to reduce the loss when the photodiode absorbs the incident light.

Optionally, the substrate is a P-type substrate, and the doped region, the doped source region and the doped drain region are all N-type heavily doped regions; or, the substrate is an N-type substrate, The doped regions, the doped source regions and the doped drain regions are all P-type heavily doped regions.

Optionally, the substrate is a lightly doped silicon wafer substrate or a silicon epitaxial layer substrate.

According to the second aspect of the embodiments of the present utility model, the present utility model provides an active pixel circuit that can be read randomly, which is characterized in that it includes a gate tube and the above-mentioned photoelectric sensor; The source of the photoelectric sensor is electrically connected, and the source of the strobe tube is used as the output end of the circuit; in the photoelectric sensor, the cathode and the drain are connected in series.

Compared with the prior art, the randomly readable active pixel circuit comprising the aforementioned photoelectric sensor of the present invention can at least produce the following beneficial technical effects:

On the one hand, the dynamic range of the random read active pixel circuit according to the embodiment of the present invention can be as high as 160dB, which is much higher than that of the traditional random read logarithmic active pixel circuit, and can produce a random readout even under very weak light intensity. Therefore, when performing photodetection, it is not necessary to integrate the photogenerated charge and reset the photodiode, which is beneficial to simplify the timing of the device and realize the random readability of the device.

On the other hand, compared with the traditional random read logarithmic active pixel circuit and the back-illuminated active pixel circuit of the 4T-APS structure, the random read active pixel circuit of the embodiment of the present invention only uses two transistors. The functions of photodetection, amplification and readout can be realized, the pixel size can be reduced, and the spatial resolution can be improved. At the same time, it has the characteristics of high gain and wide dynamic response range.

According to a third aspect of the embodiments of the present invention, the present invention provides an image sensor, the image sensor comprising the above-mentioned randomly readable active pixel circuit.

According to a fourth aspect of the embodiments of the present invention, the present invention provides a camera device including the above-mentioned image sensor.

For image sensors and camera devices, since they both include the randomly readable active pixel circuit of the present invention, they also have at least the beneficial technical effects produced by the randomly readable active pixel circuit, which will not be repeated here. .

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not limiting of the invention.

Description of drawings

1 is a schematic structural diagram of a traditional phototransistor;

Fig. 2 is the equivalent circuit diagram of the traditional phototransistor;

3 is a schematic structural diagram of a photoelectric sensor according to an exemplary embodiment of the present invention;

4 is an equivalent circuit diagram of a photoelectric sensor according to an exemplary embodiment of the present invention;

5 is a schematic diagram of a curve of the output current of a photoelectric sensor according to an exemplary embodiment of the present invention changing with the light intensity of incident light;

FIG. 6 is a schematic diagram showing the relationship between the gain and the gate voltage of a photoelectric sensor under different light intensities according to an exemplary embodiment of the present invention;

FIG. 7 is a schematic diagram of a simulation effect of the optical gain of a photoelectric sensor working in an off-state region according to an exemplary embodiment of the present invention;

8 is a schematic diagram of the circuit structure of a conventional random read logarithmic active pixel circuit;

9 is a schematic diagram of a circuit structure of a conventional back-illuminated active pixel circuit;

FIG. 10 is a schematic diagram of a circuit structure of a randomly readable active pixel circuit according to an exemplary embodiment of the present invention;

FIG. 11 is an equivalent circuit diagram of the randomly readable active pixel circuit shown in FIG. 10 .

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. Where the following description refers to the drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present invention, as recited in the appended claims.

The terms used in the present invention are for the purpose of describing particular embodiments only, and are not intended to limit the present invention. As used in this specification and the appended claims, the singular forms "a," "the," and "the" are intended to include plural forms as well, unless the context clearly dictates otherwise. It will also be understood that, as used herein, the term "and/or" is meant to include any and all possible combinations of one or more of the associated listed items.

In order to at least solve the technical problems that the phototransistor in the related art has low quantum efficiency, large volume, and cannot be applied to an image sensor, the utility model provides a photoelectric sensor, which is formed by forming a dopant on the top surface of a substrate. A source region, a doped drain region, a gate insulating layer and a gate, and a doped region and a cathode are formed on the bottom surface of the substrate to form a common substrate photodiode and a back-illuminated integrated photosensor of field effect transistors. Therefore, the advantages of the back-illuminated type and the above structure can be used to solve the technical problems that the phototransistor in the related art has low quantum efficiency, large volume, and cannot be applied to image sensors. It can also be combined with the preparation of back-illuminated CMOS image sensors. process compatible and can be fabricated into small-sized devices for use in image sensors. Below, the photoelectric sensor provided by the present utility model will be described:

As shown in FIG. 3 and FIG. 4 , the photosensor provided in the embodiment of the present invention includes a doped region 31 , a substrate 32 , a doped source region 33 , a doped drain region 34 and two isolation regions ( 35 and 36 ). The doped region 31 is disposed on the bottom surface of the substrate 32 to form a photodiode with the substrate 32; and the doped region 31 is formed with a cathode PD of the photodiode, and the cathode PD is used to connect a positive voltage to make the photoelectric Diodes work in reverse bias. The doped source region 33 and the doped drain region 34 are arranged at intervals on the top of the substrate 32 to form a field effect transistor with the substrate 32; a source S is formed on the top surface of the doped source region 33 , a drain D is formed on the top surface of the doped drain region 34 . The two isolation regions (35 and 36) are respectively located on opposite sides of the substrate 32, and extend from the doped source region 33 and the doped drain region 34 to the doped region 31 from top to bottom, respectively, for isolating the phases. adjacent pixels or adjacent sensors. The top surface of the substrate 32 is sequentially formed with a gate insulating layer 37 and a gate G disposed between the doped source region 33 and the doped drain region 34 from bottom to top; the gate G is used to connect the voltage to The working state of the field effect transistor is in a wide dynamic response range mode or a high gain mode.

Therefore, the doped region 31 and the substrate 32 on the back of the photoelectric sensor according to the embodiment of the present invention together form a photodiode for detecting incident light and converting visible light into photocharges; at the same time, the doping source region 33 on the front of the photoelectric sensor forms a photodiode. The doped drain region 34 and the substrate 32 together form a field effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET) for amplifying the photocurrent generated by the photodiode. Among them, the doped source region 33 , the doped drain region 34 and the substrate 32 on the front side of the photoelectric sensor respectively constitute the source region, the drain region and the channel region of the field effect transistor, and the gate insulating layer 37 and the gate electrode on the top surface of the substrate 32 G are the gate insulating layer 37 and the gate of the FET respectively; at the same time, the source S formed on the top surface of the doped source region 33 and the drain D formed on the top surface of the doped drain region 34 are the source of the FET respectively electrode and drain electrode. In addition, in subsequent applications, photosensitive devices required for the integration of multiple photosensors may be applied, such as image sensors or cameras or display devices, but not limited thereto. In this way, a plurality of photoelectric sensors are generally arranged in an array, so there must be a situation where the photoelectric sensors are arranged adjacently, and a certain amount of crosstalk will be generated between the adjacent photoelectric sensors. Therefore, by arranging the two isolation regions (35 and 36), adjacent pixels or adjacent sensors can be isolated to avoid crosstalk between adjacent pixels or adjacent sensors.

In the above, the isolation region can be prepared by deep trench isolation technology or capacitor deep trench isolation technology, but is not limited thereto.

In the above, the substrate 32 may be a lightly doped P-type substrate or a lightly doped N-type substrate. Based on this, in the embodiment in which the substrate 32 is a P-type substrate, the doped region 31 , the doped source region 33 and the doped drain region 34 are all N-type heavily doped regions; the substrate 32 is an N-type heavily doped region. In the embodiment of the type substrate, the doped region 31 , the doped source region 33 and the doped drain region 34 are all P-type heavily doped regions.

Hereinafter, the working principle of the photoelectric sensor according to the embodiment of the present invention will be described by taking the substrate 32 as a lightly doped P-type silicon substrate as an example:

In order to make the photoelectric sensor work, a constant positive voltage is connected to the cathode to make the photodiode work in the reverse biased region.

When the photoelectric sensor is in the working state, when the incident light enters the photodiode, it is converted into photo-generated electron-hole pairs by the photodiode. Under the action of the built-in electric field of the photodiode, the holes in the photo-generated electron-hole pair are swept into the substrate 32, so that the potential of the substrate 32 is increased, and the substrate 32 is forward biased to the field effect transistor. , thereby adjusting the operating threshold voltage of the field effect transistor. When the field effect transistor works in the off-state region, the inversion layer channel is not formed. At this time, the doped source region 33-substrate 32-doped drain region 34 of the field effect transistor can be equivalent to a (N+)P( N+) bipolar transistor (Bipolar Junction Transistor, BJT); wherein, the drain D of the field effect transistor can be regarded as the collector of the BJT, the substrate 32 can be regarded as the base of the BJT, and the source S can be seen as As the emitter of the BJT; the photo-generated current generated by the photodiode can be regarded as the forward hole current flowing into the base of the BJT. At this time, the BJT working in the amplification region amplifies the forward hole current to obtain the output current I _DS :

In formula (1), β is the magnification of the BJT collector current to the base current, I _PD is the photo-generated current of the photodiode, _IS is the reverse saturation current of the photodiode, k is the Boltzmann constant, and T is Absolute temperature, q is the charge constant, η is the internal quantum efficiency, R is the reflection loss of the device to the incident light, α is the absorption coefficient of the substrate material to the light, d is the depth of the edge of the P-type region in the depletion region of the photodiode, A is The area of the photodiode, P _in is the incident light power, h is Planck's constant, v is the incident light frequency, _DE , _NE , _LE are the minority carrier diffusion coefficient, impurity doping concentration, and minority carrier diffusion coefficient of the source region, respectively, DB, _NB , and _LB are respectively the minority carrier diffusion coefficient, doping concentration, and minority carrier diffusion length in the substrate region, and _L is the channel length between the source region and the drain region. V _BS is the substrate voltage, which varies with the intensity of the incident light on the photodiode:

When the gate voltage is increased to make the field effect transistor work in the sub-threshold region, as the potential of the substrate 32 increases, the operating threshold voltage of the field effect transistor decreases and the output current increases. At this time, the output current is the same as the incident light. A strong relationship is:

In formula (3), μ _N is the field effect mobility of the field effect transistor, C _ox is the capacitance of the gate insulating layer 37 , W and L are the channel width and length of the field effect transistor, respectively, V _GS is the gate voltage, γ is the bulk effect coefficient, Φ _fp is the potential difference between the Fermi level and the intrinsic Fermi level, n is the inverse slope of the subthreshold current, and its relationship with the subthreshold swing S is:

Therefore, as shown in FIGS. 5 to 7 , in FIG. 5 , the vertical axis represents the drain current (Drain Current) of the photoelectric sensor provided by the embodiment of the present invention, and the horizontal axis represents the photoelectric sensor provided by the embodiment of the present invention. Gate Voltage of the sensor; in FIG. 6 , the vertical axis represents the gain G _PH of the photoelectric sensor provided by the embodiment of the present invention, and the horizontal and vertical axes represent the gate voltage V _GS of the photoelectric sensor provided by the embodiment of the present invention; In FIG. 7 , the vertical axis represents the gain G _PH of the photoelectric sensor provided by the embodiment of the present invention, and the horizontal and vertical axes represent the gate voltage V _GS of the photoelectric sensor provided by the embodiment of the present invention. The photoelectric sensor provided by the embodiment of the present invention can realize that when the photoelectric sensor works in the off-state region, its output current has a linear relationship with the light intensity (Light Intensity) of the incident light, and has a dynamic range of 160dB, which is higher than the traditional one. CMOS photoelectric sensor, at this time the photoelectric sensor is in the working state of the wide dynamic response range mode. When the photoelectric sensor works in the sub-threshold region, its output current tends to have a linear relationship with the light intensity of the incident light, and the optical gain can be as high as 10 ⁶ -10 ⁷ . At this time, the photoelectric sensor is in the working state of high gain mode. Among them, the working area of the photoelectric sensor can be adjusted by adjusting the magnitude of the gate voltage to select a wide dynamic response range mode or a high gain mode.

In one embodiment, the substrate 32 may be a lightly doped silicon wafer substrate or a silicon epitaxial layer substrate.

In one embodiment, in order to further reduce the volume of the entire photoelectric sensor and increase the photosensitive area of the photodiode to a certain extent, the cathode PD is formed by an electrode layer plated on the bottom surface of the doped region 31 . Based on this, in order to reduce the loss when the photodiode absorbs incident light, in one embodiment, the electrode layer is a transparent electrode layer.

It should be noted that various technical features in the above embodiments can be combined arbitrarily, as long as there is no conflict or contradiction between the combinations of features, but due to space limitations, they are not described one by one.

Based on the foregoing embodiments of the photoelectric sensor, the embodiment of the present invention also provides an active pixel circuit that can be read randomly, so as to at least solve the following problems of the traditional active pixel circuit:

(1) As shown in Fig. 8, for a conventional random read logarithmic active pixel circuit with a wide dynamic response range, it includes three field effect transistors and one conventional photodiode. The three field effect transistors are a reset transistor Trst, a source follower Tsf and a strobe transistor Tsel, respectively. The traditional random read logarithmic active pixel circuit has a random readout type, and its output signal changes logarithmically with the change of light intensity, so it has a wide dynamic response range, generally reaching more than 100dB. In addition, the traditional random read logarithmic active pixel circuit does not need to be reset, so the pixel fill factor is large, and the operation is fast and simple. At the same time, each pixel in the traditional random reading logarithmic active pixel circuit works independently, and the photoelectric conversion process does not require time integration of the photo-generated charge, so it can be read randomly in space and time. Random readability allows important signals to be read and processed independently, making the sensor smarter, while temporal random readability allows signals to be read and processed more quickly, so space and time can be Random read performance enables faster reads of valid signals. However, the device connection method inside the pixel of the traditional random read logarithmic active pixel circuit causes the output signal to decrease with the increase of the light intensity, so that the back-end signal readout and processing circuit needs to be redesigned. Moreover, it is precisely because the output of the traditional random read logarithmic active pixel circuit has a logarithmic relationship with the input, so the sensitivity of the sensor is relatively low under low light intensity. The three-transistor design also makes it difficult to reduce pixel size, so spatial resolution is limited.

(2) As shown in FIG. 9, for the traditional back-illuminated active pixel circuit, it is a structure of an active pixel circuit (4T-APS) including four transistors, including a pinned photodiode 91 (Pinned Photodiode, PPD). ), the transmission transistor Tx, the reset switch field effect transistor Trst, the source follower Tsf, and the strobe transistor Tsel. Among them, the incident light irradiates the PPD from the back. Compared with the Front Side Illumination (FSI) structure, this back-illuminated structure has a larger photosensitive area and a fill factor (Fill Factor), thereby improving quantum efficiency and sensitivity. However, the structure of this 4T-APS circuit is complex, and the sequence operation of reset-integration-reading needs to be performed on the pixels, which does not have random readability. In addition, it is necessary to make trade-offs on the indicators of high sensitivity and wide dynamic response range. .

It can be seen from the above that at least the technical problems solved by the random read active pixel circuit in the embodiment of the present invention are: the signal isolation and processing circuit at the back end of the traditional random read logarithmic active pixel circuit in the related art need to be redesigned, and the weak The sensitivity under light intensity is low, the pixel size is difficult to reduce due to the use of three transistors, and the spatial resolution is limited, and the back-illuminated active pixel circuit structure of the 4T-APS structure is complex, does not have random readability, and is not compatible Technical issues with high sensitivity and wide dynamic response range.

In view of the above technical problems, as shown in FIG. 10 and FIG. 11 , the randomly readable active pixel circuit provided by the embodiment of the present invention includes a gate transistor T _SEL and the photosensor in any of the above embodiments. The drain of the strobe tube _TSEL is electrically connected to the source S of the photoelectric sensor, the source electrode of the strobe tube _TSEL is used as a circuit output terminal, and the gate of the strobe tube _TSEL is used to connect a positive voltage to The circuit is turned on or connected to a negative voltage to disconnect the circuit; in the photoelectric sensor, the cathode and the drain are connected in series.

It can be known from the embodiment of the photoelectric sensor that when the field effect transistor in the photoelectric sensor works in the off-state region, its output current has a linear relationship with the incident light intensity, and the dynamic range can reach more than 160dB. When the field effect transistor in the photoelectric sensor works in the sub-threshold region, the output current and the incident light intensity tend to have a linear relationship, and the optical gain can reach 10 ⁶ -10 ⁷ . Therefore, the purpose of selecting the working mode of the photoelectric sensor can be achieved by adjusting the gate voltage of the field effect transistor of the photoelectric sensor. Based on this, in the embodiment of the present invention, the randomly readable active pixel circuit made by applying the photoelectric sensor of the foregoing embodiment can at least produce the following beneficial technical effects:

On the one hand, the dynamic range of the random read active pixel circuit according to the embodiment of the present invention can also be as high as 160 dB, which is much higher than that of the traditional random read logarithmic active pixel circuit, and can generate even under very weak light intensity. Distinguishable output signal, therefore, during photodetection, it is not necessary to integrate the photogenerated charge and reset the photodiode, which is beneficial to simplify the device timing and realize the random readability of the device.

On the other hand, compared with the traditional random read logarithmic active pixel circuit and the back-illuminated active pixel circuit of the 4T-APS structure, the random read active pixel circuit of the embodiment of the present invention only uses two transistors. The functions of photodetection, amplification and readout can be realized, the pixel size can be reduced, and the spatial resolution can be improved. At the same time, it has the characteristics of high gain and wide dynamic response range.

It can be seen from the above that the operating modes of the random read active pixel circuit according to the embodiment of the present invention include a wide dynamic response range mode and a high gain mode. When the circuit is in the wide dynamic response range mode, the cathode of the photoelectric sensor is connected to the voltage that makes the photoelectric sensor work in the reverse saturation region, and the gate is connected to the voltage that makes the field effect transistor work in the off-state region; when When light enters the back of the substrate 32 of the photoelectric sensor, a photocurrent is generated in the photodiode, and the output current at the output end of the circuit has a linear relationship with the light intensity of the light. When the circuit is in high gain mode, the cathode of the photoelectric sensor is connected to the voltage that makes the photoelectric sensor work in the reverse saturation region, and the gate is connected to the voltage that makes the field effect transistor work in the sub-threshold region; When entering the backside of the substrate 32 of the photoelectric sensor, a photocurrent is generated in the photodiode, and the output current at the output end of the circuit tends to have a linear relationship with the light intensity of the light.

The following describes how to realize the selection of the working mode of the active pixel circuit that can be read randomly according to the embodiment of the present invention:

(1) Wide dynamic response range mode

The driving process for realizing the circuit in the wide dynamic response range mode includes:

applying a voltage to the cathode of the photosensor so that the photodiode operates in the reverse saturation region;

Adjust the voltage added to the gate of the photoelectric sensor to make the field effect transistor work in the off-state region;

When light enters the back of the substrate 32 of the photoelectric sensor, a photocurrent is generated in the photodiode; the output current at the output end of the circuit has a linear relationship with the light intensity of the light, and the circuit operates in a wide Dynamic response range mode.

(2) High gain mode

The driving process for realizing that the circuit is in high gain mode includes:

applying a voltage to the cathode of the photosensor so that the photodiode operates in the reverse saturation region;

Adjust the voltage added to the gate of the photoelectric sensor, so that the field effect transistor works in the sub-threshold region;

When light enters the back of the substrate 32 of the photoelectric sensor, a photocurrent is generated in the photodiode, and the output current at the output end of the circuit tends to have a linear relationship with the light intensity of the light. The operating mode of the circuit is as follows: High gain mode. The tending to linear relationship can be understood as an approximate linear relationship.

It should be noted that when the active pixel circuit can be randomly read in any of the above operating modes, it is in a conducting state. At this time, the gate of the strobe transistor T _SEL is connected to a positive voltage, so that the strobe transistor T as a switch is connected to a positive voltage. The _SEL is turned on, thereby turning on the circuit. When the random active pixel circuit needs to be disconnected, a negative voltage can be connected to the gate of the gate transistor T _SEL , so that the gate transistor T _SEL as a switch is turned off, thereby disconnecting the circuit.

In one embodiment, the gate transistor _TSEL is a field effect transistor.

Corresponding to the foregoing embodiments in which the active pixel circuit can be randomly read, the present invention also provides an image sensor. The image sensor includes the aforementioned randomly readable active pixel circuit. In addition to the active pixel circuit that can be read randomly, the image sensor also includes other structures necessary for the image sensor in the related art, which will not be described in detail here.

Corresponding to the foregoing embodiments of the image sensor, the present invention further provides a camera device. The camera device includes the aforementioned image sensor. In addition to the image sensor, the camera device also includes other structures necessary for cameras in the related art, such as a lens and a display screen, which will not be described in detail here.

The present invention is not limited to the above-mentioned embodiments, if various changes or deformations of the present invention do not depart from the spirit and scope of the present invention, if these changes and deformations belong to the claims of the present invention and the equivalent technical scope, Then the present invention also intends to include these changes and deformations.

Claims (10)

1. A photoelectric sensor is characterized by comprising a doped region, a substrate, a doped source region, a doped drain region and two isolation regions;

the doped region is arranged on the bottom surface of the substrate to form a photodiode with the substrate; the doped region is provided with a cathode of the photodiode, and the cathode is used for connecting a positive voltage to enable the photodiode to work in a reverse bias region;

the doped source region and the doped drain region are arranged at the top of the substrate at intervals so as to form a field effect transistor with the substrate; a source electrode is formed on the top surface of the doped source region, and a drain electrode is formed on the top surface of the doped drain region;

the two isolation regions are respectively positioned at two opposite sides of the substrate and respectively extend from the doped source region and the doped drain region to the doped region from top to bottom so as to isolate adjacent pixels or adjacent sensors;

a gate insulating layer and a gate electrode which are arranged between the doped source region and the doped drain region are sequentially formed on the top surface of the substrate from bottom to top; the grid is used for switching in voltage to select the working state of the field effect transistor to be in a wide dynamic response range mode or a high gain mode.

2. The photosensor of claim 1, wherein the cathode is formed from an electrode layer plated on a bottom surface of the doped region.

3. The photosensor of claim 2, wherein the electrode layer is a transparent electrode layer.

4. The photosensor of claim 1, wherein the substrate is a P-type substrate, and the doped region, the doped source region, and the doped drain region are all heavily N-doped regions; or the substrate is an N-type substrate, and the doped region, the doped source region and the doped drain region are all P-type heavily doped regions.

5. The photosensor of claim 1, wherein the substrate is a lightly doped silicon wafer substrate or a silicon epitaxial layer substrate.

6. A randomly readable active pixel circuit comprising a gate tube and a photosensor according to any one of claims 1 to 5; the drain electrode of the gate tube is electrically connected with the source electrode of the photoelectric sensor, the source electrode of the gate tube is used as the output end of the circuit, and the grid electrode of the gate tube is used for accessing positive voltage to enable the circuit to be conducted or accessing negative voltage to enable the circuit to be disconnected; in the photoelectric sensor, a cathode is connected with a drain in series.

7. The randomly readable active pixel circuit of claim 6, wherein the mode of operation of the circuit comprises a wide dynamic response range mode; when the circuit is in a wide dynamic response range mode, the cathode of the photoelectric sensor is connected with the voltage which enables the photoelectric sensor to work in a reverse saturation region, and the grid of the photoelectric sensor is connected with the voltage which enables the field effect transistor to work in an off-state region; when light rays are emitted into the back surface of the substrate of the photoelectric sensor, photocurrent is generated in the photodiode, and the output current of the circuit output end and the light intensity of the light rays are in a linear relation.

8. The randomly readable active pixel circuit of claim 7, wherein the operating modes of the circuit further comprise a high gain mode; when the circuit is in a high gain mode, the cathode of the photoelectric sensor is connected with the voltage which enables the photoelectric sensor to work in a reverse saturation region, and the grid of the photoelectric sensor is connected with the voltage which enables the field effect transistor to work in a sub-threshold region; when light rays are emitted to the back surface of the substrate of the photoelectric sensor, photocurrent is generated in the photodiode, and the output current of the circuit output end and the light intensity of the light rays tend to have a linear relation.

9. An image sensor comprising the randomly readable active pixel circuit of any one of claims 6 to 8.

10. A camera device comprising the image sensor of claim 9.

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