CN212182327U - Photoelectric sensor, random-readable active pixel circuit, image sensor, and camera device - Google Patents
Photoelectric sensor, random-readable active pixel circuit, image sensor, and camera device Download PDFInfo
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Abstract
The utility model provides an photoelectric sensor, can read active pixel circuit, image sensor and camera device at random. The photoelectric sensor comprises 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 together with the substrate; forming a source electrode on the top surface of the doped source region, and forming a drain electrode 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; 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 gate 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.
Description
Technical Field
The utility model relates to the field of electronic technology, especially, relate to photoelectric sensor, can read active pixel circuit, image sensor and camera device at random.
Background
A photo-transistor is a commonly used integrated photo-sensor that includes both a photo-sensor and a photo-current amplifier. The conventional phototriode is prepared by a bipolar process and is of a Front Side Illumination (FSI) type, and incident light can reach a photosensitive region through a passivation layer, an interconnection insulating layer and a metal wiring layer and is absorbed. In this process, light is reflected by the insulating medium or metal to cause loss, or is refracted through the multiple layers of insulating media to change the optical path, which causes the quantum efficiency to decrease.
In addition, as shown in fig. 1 and 2, the conventional photo transistor may be of NPN type or PNP type. When the phototriode is applied, the collector c1 of the phototriode is connected with a fixed positive potential VDD, the emitter is grounded, and the base b1 is suspended for light sensing. When light L is irradiated on the base electrode, photocurrent is generated between the base electrode b1 and the collector electrode c1, and the photocurrent is amplified by the phototriode to generate current gain. However, compared with a CMOS device, the conventional phototriode has a large volume and is incompatible with a CMOS process, and thus cannot be applied to a high-resolution image sensor.
SUMMERY OF THE UTILITY MODEL
Based on this, for solving the problem that the phototriode quantum efficiency is lower, the volume is great, and can't be applied to in the image sensor, the utility model provides a photoelectric sensor, can read active pixel circuit, image sensor and camera device at random.
According to a first aspect of embodiments of the present invention, the present invention provides a photoelectric sensor, 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.
Compared with the prior art, the utility model discloses photoelectric sensor has produced following beneficial technological effect at least:
the utility model discloses a top surface at a substrate forms doping source region, doping drain region, grid insulating layer and grid, and the bottom surface of substrate forms doping region and negative pole, forms the photodiode of common substrate and field effect transistor's integrated photoelectric sensor of formula of backlighting. Therefore, by utilizing the advantages of the back-illuminated type and the structure, the technical problems that the phototriode in the related technology is low in quantum efficiency, large in size and incapable of being applied to the image sensor can be solved, and the phototriode is compatible with the preparation process of the back-illuminated CMOS image sensor and can be prepared into a small-size device for the image sensor. In addition, since in subsequent applications, a plurality of photosensors may be applied to integrate a required photosensitive device, such as, but not limited to, an image sensor or a camera or a display device. As such, the plurality of photosensors are generally arranged in an array, and thus there is a certain crosstalk between adjacent photosensors in the case where the photosensors are disposed adjacently. Therefore, by arranging the two isolation regions, adjacent pixels or adjacent sensors can be isolated, and crosstalk between the adjacent pixels or adjacent sensors is avoided.
Optionally, the cathode is formed by an electrode layer plated on the bottom surface of the doped region. Through the arrangement, the size of the whole photoelectric sensor is reduced, and the light sensing area of the photodiode is increased to a certain extent.
Optionally, the electrode layer is a transparent electrode layer. By providing here, it is advantageous to reduce the loss of the photodiode when absorbing 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, and the doped region, the doped source region and the doped drain region 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 a second aspect of the embodiments of the present invention, the present invention provides a randomly readable active pixel circuit, which includes a gate tube and the above-mentioned photoelectric sensor; the drain electrode of the gate tube is electrically connected with the source electrode of the photoelectric sensor, and the source electrode of the gate tube is used as the output end of the circuit; in the photoelectric sensor, a cathode is connected with a drain in series.
Compared with the prior art, the utility model discloses but contain aforementioned photoelectric sensor's random reading active pixel circuit can produce following beneficial technological effect at least:
on the one hand, the utility model discloses but the dynamic range of random reading active pixel circuit can be up to 160dB, is far higher than the active pixel circuit of tradition random reading logarithm, even also can produce distinguishable output signal under very weak light intensity, consequently, when carrying out photoelectric detection, need not to carry out the integral to photoproduction electric charge and photodiode operation that resets, is favorable to simplifying the device chronogenesis, but realizes the random reading nature of device.
On the other hand, the utility model discloses but random reading active pixel circuit compares in the back of the body formula active pixel circuit of traditional random reading logarithm active pixel circuit and 4T-APS structure, only with two transistors alright realize photoelectric detection, enlarge and the function of reading out, can reduce the pixel size, improve spatial resolution. Meanwhile, the method has the characteristics of high gain and wide dynamic response range.
According to the third aspect of the embodiment of the present invention, the present invention provides an image sensor, which includes the above-mentioned random-readable active pixel circuit.
According to a fourth aspect of the embodiments, the present invention provides a camera device, which includes the above image sensor.
To image sensor and camera device, because it all contains the utility model discloses a but random access active pixel circuit, it also possesses at least consequently but the beneficial technological effect that random access active pixel circuit produced, does not give unnecessary details here.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
Drawings
Fig. 1 is a schematic structural view of a conventional phototransistor;
fig. 2 is an equivalent circuit diagram of a conventional phototransistor;
fig. 3 is a schematic diagram of a photosensor according to an exemplary embodiment of the present invention;
fig. 4 is an equivalent circuit diagram of a photosensor according to an exemplary embodiment of the present invention;
fig. 5 is a graph illustrating output current of a photosensor according to an exemplary embodiment of the present invention as a function of intensity of incident light;
fig. 6 is a graph illustrating a variation of gain versus gate voltage for different light intensities for a photosensor according to an exemplary embodiment of the present invention;
fig. 7 is a schematic diagram illustrating the simulation effect of optical gain when a photosensor operates in an off-state region according to an exemplary embodiment of the present invention;
FIG. 8 is a circuit diagram of a conventional random read logarithmic active pixel circuit;
fig. 9 is a schematic circuit diagram of a conventional back-illuminated active pixel circuit;
fig. 10 is a schematic circuit diagram illustrating a random-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 Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used in this disclosure is intended to encompass any and all possible combinations of one or more of the associated listed items.
For solving the technical problem that the phototriode quantum efficiency among the correlation technique is lower at least, the volume is great, and can't be applied to image sensor, the utility model provides a photoelectric sensor forms doping source region, doping drain region, grid insulating layer and grid through the top surface at a substrate, and the bottom surface of substrate forms doping region and negative pole, forms the photodiode of common substrate and field effect transistor's integrated photoelectric sensor of formula of shining back. Therefore, by utilizing the advantages of the back-illuminated type and the structure, the technical problems that the phototriode in the related technology is low in quantum efficiency, large in size and incapable of being applied to the image sensor can be solved, and the phototriode is compatible with the preparation process of the back-illuminated CMOS image sensor and can be prepared into a small-size device for the image sensor. The following explains the photoelectric sensor provided by the present invention:
as shown in fig. 3 and 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 arranged 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 for switching in a positive voltage to operate the photodiode in a reverse bias region. The doped source region 33 and the doped drain region 34 are arranged on the top of the substrate 32 at intervals so as 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, and 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 two opposite sides of the substrate 32 and respectively extend from the doped source region 33 and the doped drain region 34 to the doped region 31 from top to bottom for isolating adjacent pixels or adjacent sensors. A gate insulating layer 37 and a gate electrode G arranged between the doped source region 33 and the doped drain region 34 are sequentially formed on the top surface of the substrate 32 from bottom to top; the gate G is used for switching in a voltage to make the operation state of the field effect transistor 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 photosensor of the embodiment of the present invention form a photodiode together, which is used for detecting incident light and converting visible light into photocharge; meanwhile, the doped source region 33, the doped drain region 34 and the substrate 32 on the front surface of the photosensor jointly form a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) for amplifying the photocurrent generated by the photodiode. The doped source region 33, the doped drain region 34 and the substrate 32 on the front surface of the photoelectric sensor respectively form a source region, a drain region and a channel region of the field effect transistor, and the gate insulating layer 37 and the gate G on the top surface of the substrate 32 respectively form a gate insulating layer 37 and a gate of the field effect transistor; meanwhile, 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 respectively a source electrode and a drain electrode of the field effect transistor. In addition, since in subsequent applications, a plurality of photosensors may be applied to integrate a required photosensitive device, such as, but not limited to, an image sensor or a camera or a display device. As such, the plurality of photosensors are generally arranged in an array, and thus there is a certain crosstalk between adjacent photosensors in the case where the photosensors are disposed adjacently. Therefore, by providing the two isolation regions (35 and 36), adjacent pixels or adjacent sensors can be isolated from each other, and crosstalk between adjacent pixels or adjacent sensors can be prevented.
In the above, the isolation region may be prepared by a deep trench isolation technique or a capacitive deep trench isolation technique, 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 that 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; in the embodiment where the substrate 32 is an N-type substrate, the doped region 31, the doped source region 33, and the doped drain region 34 are all P-type heavily doped regions.
The working principle of the photoelectric sensor according to the embodiment of the present invention is described below by taking the substrate 32 as a lightly doped P-type silicon substrate as an example:
in order to make the photoelectric sensor in working state, a constant positive voltage is connected to the cathode, so that the photodiode works in a reverse bias region.
When the photoelectric sensor is in a working state, incident light is transmitted into the photodiode and then is converted into photo-generated electron-hole pairs by the photodiode. Under the action of the built-in electric field of the photodiode, the photo-generated electron-hole pairs are swept into the substrate 32, so that the potential of the substrate 32 is increased, and the substrate 32 is subjected to forward bias action on the field effect transistor, so that the working threshold voltage of the field effect transistor is adjusted. When the field effect Transistor works in an off-state region, an inversion layer channel is not formed, and at this time, the doped source region 33, the substrate 32 and the doped drain region 34 of the field effect Transistor can be equivalent to a Bipolar Junction Transistor (BJT) with (N +) P (N +); whereinThe 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 regarded as the emitter of the BJT; the photo-generated current generated by the photodiode can be regarded as a 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 IDS:
In formula (1), β is the amplification factor of BJT collector current to base current, IPDIs the photo-generated current of a photodiode, ISIs the reverse saturation current of the photodiode, k is the Boltzmann constant, T is the absolute temperature, q is the charge constant, η is the internal quantum efficiency, R is the reflection loss of the device to incident light, α is the absorption coefficient of the substrate material to light, d is the depth of the edge of the P-type region of the depletion region of the photodiode, A is the area of the photodiode, P is the area of the photodiodeinIs the incident light power, h is the Planck constant, v is the incident light frequency, DE、NE、LERespectively the source region minority carrier diffusion coefficient, impurity doping concentration, minority carrier diffusion coefficient, DB、NB、LBThe diffusion coefficient, the doping concentration and the diffusion length of the minority carrier of the substrate area are respectively, and L is the length of a channel between a source area and a drain area. VBSSubstrate 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, the work threshold voltage of the field effect transistor is reduced and the output current is increased along with the increase of the electric potential of the substrate 32, and the relationship between the output current and the light intensity of the incident light is as follows:
in the formula (3), μNIs the field-effect mobility of a field-effect transistor, CoxFor the gate insulator 37 capacitance, W and L are the channel width and length, respectively, of the FETGSIs the gate voltage, gamma is the bulk coefficient, phifpIs the potential difference between the fermi level and the intrinsic fermi level, n is the inverse slope of the sub-threshold current, which is related to the sub-threshold swing S by:
thus, as shown in fig. 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 Gate Voltage (Gate Voltage) of the photoelectric sensor provided by the embodiment of the present invention; in fig. 6, the vertical axis represents the gain G of the photoelectric sensor provided by the embodiment of the present inventionPHThe horizontal and vertical directions of the invention represent the grid voltage V of the photoelectric sensor provided by the embodiment of the utility modelGS(ii) a In fig. 7, the vertical axis represents the gain G of the photoelectric sensor provided by the embodiment of the present inventionPHThe horizontal and vertical directions of the invention represent the grid voltage V of the photoelectric sensor provided by the embodiment of the utility modelGS. Through the embodiment of the utility model provides a photoelectric sensor can realize that photoelectric sensor work is when the off-state is regional, and its output current is linear relation with the Light Intensity (Light Intensity) of incident Light to 160 dB's dynamic range has, is higher than traditional CMOS photoelectric sensor, and photoelectric sensor is in the operating condition of wide dynamic response range mode this moment. When the photoelectric sensor works in a subthreshold region, the output current and the light intensity of incident light tend to be in a linear relation, and the optical gain can be as high as 106-107At this time, the photosensor is in the operating state of the high gain mode. The working area of the photoelectric sensor can be adjusted by adjusting the size of the grid voltage so as to select a wide dynamic response range mode or a high gain mode.
In an embodiment, the substrate 32 may be a lightly doped silicon wafer substrate or a silicon epitaxial layer substrate.
In one embodiment, to further reduce the volume of the entire photosensor and to increase the photosensitive area of the photodiode to some 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 of the photodiode when absorbing the incident light, in an embodiment, the electrode layer is a transparent electrode layer.
It should be noted that various technical features in the above embodiments can be arbitrarily combined, as long as there is no conflict or contradiction between the combinations of the features, but the combination is limited by space and is not described one by one.
Based on aforementioned photosensor's embodiment, the embodiment of the utility model provides a but also provide a random reading active pixel circuit to solve traditional active pixel circuit's following problem at least:
one, as shown in fig. 8, for a conventional random read log 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 respectively a reset transistor Trst, a source follower Tsf and a gate tube Tsel. The traditional random reading logarithmic active pixel circuit has a random reading type, and the output signal of the traditional random reading logarithmic active pixel circuit is logarithmically changed along with the change of light intensity, so that the traditional random reading logarithmic active pixel circuit has a wide dynamic response range which can generally reach more than 100 dB. In addition, the traditional random reading logarithmic active pixel circuit does not need to be reset, so that the pixel filling factor is large, and the operation is fast and simple. Meanwhile, each pixel in the traditional random reading logarithmic active pixel circuit works independently and does not need to perform time integration on photo-generated charges in the photoelectric conversion process, so that random reading can be performed in space and time, the random reading performance in space allows important signals to be read and processed independently, the sensor is more intelligent, and the random reading performance in time enables the signals to be read out and processed more quickly, so that the random reading performance in space and time enables the reading speed of effective signals to be higher. However, the conventional random access logarithmic active pixel circuit has a device connection manner inside the pixel such that the output signal is reduced with the increase of the illumination intensity, and the signal reading and processing circuit at the back end needs to be redesigned. Moreover, the sensitivity of the sensor is low under weak light intensity because the output and the input of the traditional random reading logarithmic active pixel circuit are in logarithmic relation. The design using three transistors also makes it difficult to reduce the pixel size, and therefore the spatial resolution is limited.
As shown in fig. 9, the conventional back-illuminated active pixel circuit has a structure of an active pixel circuit (4T-APS) including four transistors, including a Pinned Photodiode 91 (PPD), a transmission transistor Tx, a reset switching field effect transistor Trst, a source follower Tsf, and a gate transistor Tsel. Wherein the incident light illuminates the PPD from the back. This backside illuminated structure has a larger photosensitive area and Fill Factor (Fill Factor) compared to the Front Side Illumination (FSI) structure, thus improving quantum efficiency and sensitivity. However, such a 4T-APS circuit has a complicated structure, requires a time-series operation of reset-integration-read for a pixel, does not have random readability, and additionally, requires a trade-off in obtaining indices of high sensitivity and a wide dynamic response range.
In view of the above, the embodiment of the present invention provides a technical problem that can be solved at least by a random-reading active pixel circuit: in the related technology, a signal independent and processing circuit at the rear end of a traditional random reading logarithmic active pixel circuit needs to be redesigned, the sensitivity is low under weak light intensity, the pixel size is difficult to reduce and the spatial resolution is limited due to the adoption of three transistors, and the back-illuminated active pixel circuit with the 4T-APS structure has the technical problems of complex structure, no random reading property, and incompatibility with high sensitivity and wide dynamic response range.
To solve the above technical problem, as shown in fig. 10 and 11, an embodiment of the present invention provides a random-readable active pixel circuit including a gate transistor TSELAnd a photosensor as in any of the embodiments above. The gate pipe TSELIs electrically connected with the source S of the photoelectric sensor, and a gate tube TSELAs a circuit output terminal, a gate tube TSELThe grid of the switch is used for switching in a positive voltage to enable the circuit to be switched on or switching in a negative voltage to enable the circuit to be switched off; in the photoelectric sensor, a cathode is connected with a drain in series.
It can be known from the embodiments of the photo sensor that when the field effect transistor in the photo sensor operates in the off-state region, the output current and the incident light intensity are in a linear relationship, and the dynamic range can reach over 160 dB. When the field effect transistor in the photoelectric sensor works in a subthreshold region, the output current and the incident light intensity tend to be in a linear relation, and the optical gain can reach 106～107. Therefore, the purpose of selecting the working mode of the photoelectric sensor can be achieved by adjusting the grid voltage of the field effect transistor of the photoelectric sensor. Based on this, the embodiment of the present invention, in which the photosensor of the foregoing embodiment is applied, can produce at least the following beneficial technical effects:
on the one hand, the utility model discloses but the dynamic range of random reading active pixel circuit also can be up to 160dB, is far higher than the active pixel circuit of tradition random reading logarithm, even also can produce distinguishable output signal under very weak light intensity, consequently, when carrying out photoelectric detection, need not to carry out the integral to photoproduction electric charge and photodiode operation that resets, is favorable to simplifying the device chronogenesis, but realizes the random reading nature of device.
On the other hand, the utility model discloses but random reading active pixel circuit compares in the back of the body formula active pixel circuit of traditional random reading logarithm active pixel circuit and 4T-APS structure, only with two transistors alright realize photoelectric detection, enlarge and the function of reading out, can reduce the pixel size, improve spatial resolution. Meanwhile, the method has the characteristics of high gain and wide dynamic response range.
In view of the above, the working modes of the random-readable active pixel circuit according to the embodiments of the present invention include a wide dynamic response range mode and a high gain 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 to the back surface of the substrate 32 of the photoelectric sensor, photocurrent is generated in the photoelectric diode, and the output current of the circuit output end and the light intensity of the light rays are in a linear relation. 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 32 of the photoelectric sensor, photocurrent is generated in the photoelectric diode, and the output current of the circuit output end and the light intensity of the light rays tend to have a linear relation.
The following describes how to implement the selection of the operation mode of the random-readable active pixel circuit according to the embodiments of the present invention:
wide dynamic response range mode
The driving process for realizing the circuit in the wide dynamic response range mode comprises the following steps:
applying a voltage to a cathode of the photosensor to operate the photodiode in a reverse saturation region;
adjusting a voltage applied to a gate of the photosensor to operate the field effect transistor in an off-state region;
when light is incident on the back of the substrate 32 of the photosensor, a photocurrent is generated in the photodiode; the output current of the circuit output end and the light intensity of the light ray are in a linear relation, and the working mode of the circuit is a wide dynamic response range mode.
(II) high gain mode
The driving process for realizing the circuit in the high gain mode comprises the following steps:
applying a voltage to a cathode of the photosensor to operate the photodiode in a reverse saturation region;
adjusting a voltage applied to a gate of the photosensor to operate the field effect transistor in a sub-threshold region;
when light rays are emitted to the back surface of the substrate 32 of the photoelectric sensor, photocurrent is generated in the photoelectric diode, the output current of the output end of the circuit and the light intensity of the light rays tend to be in a linear relation, and the working mode of the circuit is a high-gain mode. The tendency to linear relationship therein can be understood as approximating a linear relationship.
It should be noted that, when the random-readable active pixel circuit is in any of the above operating modes, it is in a conducting state, and at this time, the gate tube T is in a conducting stateSELThe grid of the switch is connected with a positive voltage to enable the gate tube T as a switchSELAnd conducting to further conduct the circuit. When the random active pixel circuit needs to be disconnected, the gate tube T can be usedSELThe grid of the switch is connected with a negative voltage to enable the gate tube T as a switchSELOpen, thereby opening the circuit.
In one embodiment, the gate tube TSELIs a field effect transistor.
Corresponding to the embodiment of the aforesaid readable active pixel circuit at random, the utility model also provides an image sensor. The image sensor includes the aforementioned randomly readable active pixel circuit. Besides the randomly readable active pixel circuit, the image sensor also includes other structures necessary for the image sensor in the related art, which are not described herein in detail.
Corresponding to the embodiment of the aforementioned image sensor, the utility model also provides a camera device. The camera device comprises the image sensor. Besides the image sensor, the camera device also includes other structures necessary for the camera in the related art, such as a lens and a display screen, which are not described in detail herein.
The present invention is not limited to the above embodiment, and if various modifications or variations of the present invention do not depart from the spirit and scope of the present invention, they are intended to be covered if they fall within the scope of the claims and the equivalent technology of the present invention.
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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| CN202020379084.5U CN212182327U (en) | 2020-03-23 | 2020-03-23 | Photoelectric sensor, random-readable active pixel circuit, image sensor, and camera device |
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| CN202020379084.5U CN212182327U (en) | 2020-03-23 | 2020-03-23 | Photoelectric sensor, random-readable active pixel circuit, image sensor, and camera device |
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