CN112802861A - Composite dielectric grid transverse collection photosensitive detection unit, detector and working method of detector - Google Patents
Composite dielectric grid transverse collection photosensitive detection unit, detector and working method of detector Download PDFInfo
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Abstract
The invention relates to a composite dielectric gate transverse collection photosensitive detection unit, a photosensitive detector and a working method thereof, wherein the photosensitive detection unit comprises a composite dielectric gate MOS capacitor and a composite dielectric gate transistor which are formed on the front surface of the same substrate, and further comprises a buried gate MOS capacitor, the buried gate MOS capacitor is positioned on the back surface of a P-type semiconductor substrate and is opposite to the central position of the composite dielectric gate MOS capacitor above, and the composite dielectric gate MOS capacitor and the composite dielectric gate transistor are separated by a shallow groove isolation region in the P-type semiconductor substrate. The photosensitive detector comprises an array formed by arranging a plurality of detection units, drain terminals of composite dielectric gate transistors in each row are connected to form bit lines, source terminals of the composite dielectric gate transistors in each row are connected to form a common source, control gates in each row are connected to form word lines, buried gates in each row are connected to form buried gate lines, and a substrate is shared; the photosensitive detection units are separated by shallow trench isolation regions and deep trench isolation regions. The working process sequentially comprises the collection of photoelectrons, the reading and amplification of the photoelectrons and the resetting of the photoelectrons. The invention has high photoelectric charge collection efficiency.
Description
Technical Field
The invention relates to a composite dielectric grid transverse collection photosensitive detection unit, also relates to a composite dielectric grid transverse collection photosensitive detector, further relates to a working method of the composite dielectric grid transverse collection photosensitive detector, and belongs to the technical field of photosensitive detectors.
Background
The imaging detector has great application in various fields such as military, civil use and the like. The main imaging detectors currently under development are CCD and CMOS-APS. The CCD is early and relatively mature in technology, and the basic structure of the CCD is that a row of MOS capacitors are connected in series, and the generation and the change of a potential well on the surface of a semiconductor are controlled through a voltage pulse time sequence on the capacitors, so that the storage, the transfer and the reading of photo-generated charge signals are realized. Also due to this signal transfer characteristic, the charge transfer speed is very limited, and therefore the imaging speed is not high. In addition, because the capacitors are connected in series, the transmission of signals in the whole row is influenced by the problem of one capacitor, so that the process requirement is extremely high, and the yield and the cost are not ideal.
Each pixel of the CMOS-APS is composed of a diode and a transistor, each pixel is independent, charges do not need to be moved in series in the whole signal transmission process, the performance of other pixels is not affected when a certain pixel has a problem, the defect of the CCD in the aspect is overcome, and the process requirement is not strict. The COMS allows data to be read out from the whole arrangement, parts or even cells by a simple X-Y addressing technique due to single-point signaling, thereby increasing the addressing speed and achieving faster signaling. However, CMOS-APS each pixel consists of a plurality of transistors and a photodiode (including amplifiers and a/D conversion circuitry), so that the photosensitive area of each pixel occupies only a small surface area of the pixel itself, and the sensitivity, dynamic range and resolution are relatively small.
Although the chinese patent publication CN 102938409a discloses a novel two-transistor photosensitive detector, when the two-transistor photosensitive detector is used in the case of back-side incidence, the photo-charges are mainly generated near the back of the pixel and need to be collected on the surface of the front of the pixel, because the ratio of the pixel thickness (over 2 um) to the pixel size (submicron) is large, the depth of the depletion region under the exposure voltage is difficult to reach 2um, so the photo-charges need to pass through a long non-depletion region to be stored, and the photo-charges are easily matched in the process, which results in the reduction of the collection efficiency of the photo-charges.
Disclosure of Invention
The invention mainly aims to solve the problems in the prior art, and the composite dielectric gate transverse collection photosensitive detection unit provided by the invention can realize the improvement of the collection efficiency of the small-pixel back-illuminated light charges by transversely collecting the light charges.
In order to solve the technical problems, the invention provides a composite dielectric gate lateral collection photosensitive detection unit, which comprises a composite dielectric gate MOS capacitor and a composite dielectric gate transistor which are formed on the front surface of the same P-type semiconductor substrate, and further comprises a buried gate MOS capacitor, wherein the buried gate MOS capacitor is positioned on the back surface of the P-type semiconductor substrate and is opposite to the central position of the composite dielectric gate MOS capacitor above, and the composite dielectric gate MOS capacitor and the composite dielectric gate transistor are separated in the P-type semiconductor substrate through a shallow slot isolation region.
Further, the composite dielectric gate MOS capacitor and the composite dielectric gate transistor are both configured as follows: and a bottom dielectric layer, a floating gate, a top dielectric layer and a control gate are sequentially arranged above the P-type semiconductor substrate, wherein the floating gate and the control gate are shared by the composite dielectric gate MOS capacitor and the composite dielectric gate transistor.
Furthermore, the composite dielectric gate transistor is also provided with a source electrode and a drain electrode in the P-type semiconductor substrate; the buried gate MOS capacitor comprises a cylindrical deep groove which extends upwards from the back of a P-type semiconductor substrate to the inside of the substrate, a buried gate and an insulating medium buried layer are arranged in the cylindrical deep groove, the buried gate extends upwards from the bottom interface of the P-type semiconductor substrate along the central line of the cylindrical deep groove, and the insulating medium buried layer wraps the periphery of the buried gate with uniform thickness to isolate the buried gate from the P-type semiconductor substrate.
Furthermore, the composite dielectric gate MOS capacitor realizes the photosensitive function of the detector, the composite dielectric gate transistor realizes the reading function of the detector, and the buried gate MOS capacitor realizes the auxiliary collection function of the detector.
Furthermore, the bottom dielectric layer, the top dielectric layer and the insulating dielectric buried layer are all made of wide bandgap materials.
Further, the bottom dielectric layer and the insulating dielectric buried layer are made of silicon oxide or silicon oxynitride; the top dielectric layer is made of silicon oxide-silicon nitride-silicon oxide, silicon oxide-aluminum oxide-silicon oxide, silicon oxide or aluminum oxide.
Furthermore, the floating gate is made of polysilicon; the control grid and the buried grid are made of polysilicon, metal or transparent conductive electrodes.
The invention has the beneficial effects that: 1. because the composite dielectric gate MOS capacitor and the composite dielectric gate transistor share the floating gate, photoelectrons collected by the composite dielectric gate MOS capacitor in the exposure process can be read by the composite dielectric gate transistor through a charge coupling effect.
2. The photosensitive detection unit can realize collection and response of photoelectrons, and the mechanism is as follows: and applying zero or positive voltage on the control gate, applying negative voltage on the P-type semiconductor substrate, applying a voltage between the voltage of the control gate and the voltage of the substrate on the buried gate, and forming depletion layers in the depth of the P-type semiconductor substrate. When light is incident into the depletion layer, photons are absorbed by the semiconductor to generate photoelectrons; photoelectrons move to the interface between the insulating medium buried layer of the buried gate MOS capacitor and the P-type semiconductor substrate under the driving of the buried gate-substrate voltage difference, and further move to the interface between the composite medium gate MOS capacitor and the bottom medium layer under the driving of the control gate-buried gate voltage difference; photoelectrons collected at the interface change the potential at the interface, and further influence the potential of a floating gate, namely a charge coupling layer; and the floating gate potential when the composite dielectric gate transistor is started is a fixed value, and in order to keep the constant potential, when reading, in order to start the composite dielectric gate transistor, the voltage on the control gate is inevitably higher than the initial threshold voltage of the composite dielectric gate transistor, and the drift amount of the threshold voltage is generated. So far, the measurement of the drift amount of the threshold voltage before and after exposure can determine the number of photoelectrons collected at the interface of the composite dielectric gate MOS capacitor and the bottom dielectric layer.
3. The photoelectric charge is transversely collected to the interface of the buried gate and the substrate through the buried gate structure on the back of the pixel, is transported to the front of the pixel along the interface and is collected by the MOS capacitor of the composite dielectric gate on the front of the pixel, and the reading function of the detection unit is realized by the MOS transistor of the composite dielectric gate, so that the high photoelectric charge collection efficiency is realized.
Another object of the present invention is to provide a composite dielectric gate lateral collection photosensitive detector, in which each photosensitive detection unit can achieve high photoelectric charge collection efficiency by laterally collecting photoelectric charges, in order to solve the problems in the prior art.
In order to solve the technical problems, the technical scheme of the invention is to provide a composite dielectric gate transverse collection photosensitive detector based on photosensitive detection units, wherein a plurality of photosensitive detection units are arranged to form a detection array, drain terminals of composite dielectric gate transistors of each row of photosensitive detection units in the detection array are connected to form a bit line i, wherein i is any positive integer, and the maximum value of i is the row number of the detection array; the source ends of the composite dielectric gate transistors of all the photosensitive detection units are connected to form a common source; the control gates of the photosensitive detection units in each row are respectively connected to form a word line j, wherein j is any positive integer, and the maximum value of j is the number of rows of the detection array; the buried gates of each row of photosensitive detection units are connected to form a buried gate line k, wherein k is any positive integer, and the maximum value of k is the row number of the detection array; the P-type semiconductor substrates of all the photosensitive detection units are shared; the photosensitive detection units are separated by shallow trench isolation regions on the front side of the substrate and deep trench isolation regions on the back side of the substrate.
The invention has the beneficial effects that: the composite dielectric gate transverse collection photosensitive detector transversely collects the photoelectric charges to the interface of the buried gate substrate through the buried gate structure on the back of the pixel, conveys the photoelectric charges to the front of the pixel along the interface and is collected by the composite dielectric gate MOS capacitor on the front of the pixel, and realizes the reading function of the detector through the composite dielectric gate transistor, thereby realizing high photoelectric charge collection efficiency, and the specific advantages are as follows: 1. the photoelectron collection efficiency is high: when the detector structure collects photoelectrons, the electrons do not need to pass through a long-distance non-depletion region, but are collected by the buried gate MOS capacitor on the side surface and then are transported to the composite dielectric gate MOS capacitor on the front surface of the device, so that the probability of compounding the photoelectrons is reduced, and the proportion of successfully collecting the photoelectrons generated in the P-type semiconductor substrate is increased.
2. The quantum efficiency is high: because the detector structure is suitable for P type substrates (2 um-10 um, depending on the processing capacity of the buried gate MOS capacitor) with various thicknesses, the P type substrate can keep larger thickness. Therefore, a larger proportion of light incident to the detection device is absorbed by the P-type substrate to generate photoelectrons, and the quantum efficiency of the red light wave band can be effectively increased.
Still another object of the present invention is to provide a method for laterally collecting photocharges by using a composite dielectric gate, which is capable of laterally collecting photocharges, thereby achieving high photocharge collection efficiency.
In order to solve the technical problems, the technical scheme of the invention is to provide a working method of a composite dielectric gate transverse collection photosensitive detector, which sequentially comprises the following steps of collecting photoelectrons: applying zero or positive voltage on the control gate, applying negative voltage on the substrate, applying voltage between the control gate voltage and the substrate voltage on the buried gate, collecting photoelectrons formed in a depletion region of the P-type semiconductor substrate to an interface between the P-type semiconductor substrate and an insulating medium buried layer in a deep groove of the buried gate MOS capacitor, and further transporting the photoelectrons to an interface between the substrate and a bottom dielectric layer of the composite medium gate MOS capacitor along the interface;
optoelectronic readout and amplification: grounding the source electrode of the composite dielectric gate transistor, keeping the negative voltage applied in the exposure process of the substrate unchanged, connecting the drain electrode of the composite dielectric gate transistor with a positive voltage, and applying a slope voltage to the control gate to scan the threshold value; directly measuring two values of threshold voltage before and after exposure, comparing the two values, and determining the magnitude of an optical signal;
resetting of the photoelectrons: negative bias is applied to the control grid and the buried grid, the substrate and the source electrode of the composite dielectric grid transistor are grounded, and photoelectrons originally accumulated at the interface of the substrate of the composite dielectric grid MOS capacitor and the bottom dielectric layer and the interface of the substrate in the cylindrical deep groove of the buried grid MOS capacitor and the insulating dielectric buried layer are drained away under the action of an electric field after a certain time.
The method comprises the steps of applying positive voltage of 0V-1V to a selected control gate, applying negative voltage of-5V-3V to the substrate, and applying voltage of 0V-3V to a buried gate; in the second step, the drain electrode is connected with a proper positive voltage of 0.1-0.5V, and a proper ramp voltage of 1-5V is applied to the selected control grid electrode; in the third step, the negative bias voltage applied to the selected control grid is-3V to-1V.
The beneficial effects obtained by the present invention are as above, and are not described in detail.
Drawings
FIG. 1 is a plan layout of a composite dielectric gate lateral collection photosensitive detection cell of the present invention;
FIG. 2 is a structural diagram of the composite dielectric gate transistor perpendicular to the channel direction, i.e., the gate width direction (X-X'), in accordance with the present invention;
FIG. 3 is a structural diagram of the composite dielectric gate MOS capacitor in parallel with the channel direction, i.e. the gate length direction (Y1-Y1');
FIG. 4 is a structural view of a composite dielectric gate transistor according to the present invention, which is parallel to the channel direction, i.e., the gate length direction (Y2-Y2');
FIG. 5 is a schematic diagram of the interconnection method of the array of the composite dielectric grid lateral collection photosensitive detector of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.
As shown in fig. 1 to 4, the composite dielectric gate lateral collection photosensitive detection unit of the present invention includes a composite dielectric gate MOS capacitor and a composite dielectric gate transistor formed on the front surface of the same P-type semiconductor substrate, and further includes a buried gate MOS capacitor, the buried gate MOS capacitor is located on the back surface of the P-type semiconductor substrate and faces the center of the composite dielectric gate MOS capacitor above, and the composite dielectric gate MOS capacitor and the composite dielectric gate transistor are separated by a shallow trench isolation region in the P-type semiconductor substrate.
The composite dielectric gate MOS capacitor realizes the photosensitive function of the detector, the composite dielectric gate transistor realizes the reading function of the detector, and the buried gate MOS capacitor realizes the auxiliary collection function of the detector. The structures of the composite dielectric gate MOS capacitor and the composite dielectric gate transistor are as follows: a bottom dielectric layer, a floating gate, a top dielectric layer and a control gate are sequentially arranged above a P-type semiconductor substrate, wherein the floating gate and the control gate are shared by a composite dielectric gate MOS capacitor and a composite dielectric gate transistor.
The composite dielectric gate transistor is also provided with a source electrode and a drain electrode in the P-type semiconductor substrate; the buried gate MOS capacitor comprises a cylindrical deep groove which extends upwards from the back surface of the P-type semiconductor substrate to the inside of the substrate, a buried gate and an insulating medium buried layer are arranged in the cylindrical deep groove, the buried gate extends upwards from the bottom interface of the P-type semiconductor substrate along the central line of the cylindrical deep groove, and the insulating medium buried layer wraps the periphery of the buried gate with uniform thickness to isolate the buried gate from the P-type semiconductor substrate.
The bottom dielectric layer, the top dielectric layer and the insulating dielectric buried layer are all made of wide bandgap materials. The bottom dielectric layer and the insulating dielectric buried layer are made of silicon oxide or silicon oxynitride; the top dielectric layer is made of silicon oxide-silicon nitride-silicon oxide, silicon oxide-aluminum oxide-silicon oxide, silicon oxide or aluminum oxide.
The floating gate, namely the charge coupling layer, is made of polysilicon; the control grid and the buried grid are made of polysilicon, metal or transparent conductive electrodes.
The photosensitive detection unit can realize collection and response of photoelectrons, and the mechanism is as follows: and applying zero or positive voltage on the control gate, applying negative voltage on the P-type semiconductor substrate, applying a voltage between the voltage of the control gate and the voltage of the substrate on the buried gate, and forming depletion layers in the depth of the P-type semiconductor substrate. When light is incident into the depletion layer, photons are absorbed by the semiconductor to generate photoelectrons; photoelectrons move to the interface between the insulating medium buried layer of the buried gate MOS capacitor and the P-type semiconductor substrate under the driving of the buried gate-substrate voltage difference, and further move to the interface between the composite medium gate MOS capacitor and the bottom medium layer under the driving of the control gate-buried gate voltage difference; photoelectrons collected at the interface change the potential at the interface, thereby influencing the potential of the floating gate; and the floating gate potential when the composite dielectric gate transistor is started is a fixed value, and in order to keep the constant potential, when reading, in order to start the composite dielectric gate transistor, the voltage on the control gate is inevitably higher than the initial threshold voltage of the composite dielectric gate transistor, and the drift amount of the threshold voltage is generated. So far, the measurement of the drift amount of the threshold voltage before and after exposure can determine the number of photoelectrons collected at the interface of the composite dielectric gate MOS capacitor and the bottom dielectric layer.
The photoelectric charge is transversely collected to the interface of the buried gate and the substrate through the buried gate structure on the back of the pixel, is transported to the front of the pixel along the interface and is collected by the MOS capacitor of the composite dielectric gate on the front of the pixel, and the reading function of the detection unit is realized by the MOS transistor of the composite dielectric gate, so that the high photoelectric charge collection efficiency is realized.
As shown in FIG. 5, the present invention is based on a composite dielectric grid of photosensitive detection units for laterally collecting photosensitive detectors, and a plurality of photosensitive detection units are arranged to form a detection array, wherein a dotted square frame shows a repeating unit. In the detection array, drain terminals of composite dielectric gate transistors of each row of photosensitive detection units are connected to form a bit line i, wherein i is any positive integer, and the maximum value of i is the row number of the detection array; the source ends of the composite dielectric gate transistors of all the photosensitive detection units are connected to form a common source; the control gates of the photosensitive detection units in each row are respectively connected to form a word line j, wherein j is any positive integer, and the maximum value of j is the number of rows of the detection array; the buried gates of each row of photosensitive detection units are connected to form a buried gate line k, wherein k is any positive integer, and the maximum value of k is the row number of the detection array; the P-type semiconductor substrates of all the photosensitive detection units are shared; the photosensitive detection units are separated by shallow trench isolation regions on the front side of the substrate and deep trench isolation regions on the back side of the substrate.
The detection array mainly comprises three processes of exposure, reading and resetting when working.
During exposure, the substrate is negatively biased (e.g., -5V to-3V), the bit lines and common source are grounded, a positive voltage (e.g., 0V to 1V) is applied to each row of word lines, and a voltage (e.g., -3V to 0V) between the word line voltage and the substrate voltage is applied to each row of buried gate lines.
During reading, according to the position (row and column number) of the pixel to be read in the array, a proper ramp voltage (such as 1V-3V) is applied to the word line of the row at the end of exposure to scan the threshold, the substrate and the buried gate keep the previous voltage unchanged, the common source is grounded, and the bit line of the pixel to be read is connected with a proper positive voltage.
During reset, a negative voltage (such as-3V to-1V) is applied to each row of word lines and buried gate lines, and the substrate and all bit lines and common source are grounded.
The composite dielectric gate transverse collection photosensitive detector transversely collects photocharges to an interface of a buried gate substrate through a buried gate structure on the back of a pixel, conveys the photocharges to the front of the pixel along the interface and is collected by a composite dielectric gate MOS capacitor on the front of the pixel, and the reading function of the detector is realized by a composite dielectric gate transistor, so that the high collection efficiency of the photocharges is realized, and the composite dielectric gate transverse collection photosensitive detector has the following specific advantages:
1. the photoelectron collection efficiency is high: when the detector structure collects photoelectrons, the electrons do not need to pass through a long-distance non-depletion region, but are collected by the buried gate MOS capacitor on the side surface and then are transported to the composite dielectric gate MOS capacitor on the front surface of the device, so that the probability of compounding the photoelectrons is reduced, and the proportion of successfully collecting the photoelectrons generated in the P-type semiconductor substrate is increased.
2. The quantum efficiency is high: the detector structure is suitable for P-type substrates (2 um-10 um, depending on the buried gate MOS capacitance processing capacity) with various thicknesses, so that the P-type substrate can keep larger thickness. Therefore, a larger proportion of light incident to the detection device is absorbed by the P-type substrate to generate photoelectrons, and the quantum efficiency of the red light wave band can be effectively increased.
The working method of the composite dielectric grid transverse collection photosensitive detector sequentially comprises the following steps:
collecting photoelectrons: applying zero or positive voltage on the control gate, applying negative voltage on the substrate, applying voltage between the control gate voltage and the substrate voltage on the buried gate, collecting photoelectrons formed in a depletion region of the P-type semiconductor substrate to an interface between the P-type semiconductor substrate and an insulating medium buried layer in a deep groove of the buried gate MOS capacitor, and further transporting the photoelectrons to an interface between the substrate and a bottom dielectric layer of the composite medium gate MOS capacitor along the interface;
optoelectronic readout and amplification: because the composite dielectric gate MOS capacitor and the composite dielectric gate transistor share the floating gate, photoelectrons collected by the composite dielectric gate MOS capacitor in the exposure process can be read by the composite dielectric gate transistor through a charge coupling effect; grounding the source electrode of the composite dielectric gate transistor, keeping the negative voltage applied in the exposure process of the substrate unchanged, connecting the drain electrode of the composite dielectric gate transistor with a positive voltage, and applying a slope voltage to the control gate to scan the threshold value; directly measuring two values of threshold voltage before and after exposure, comparing the two values, and determining the magnitude of an optical signal;
resetting of the photoelectrons: negative bias is applied to the control grid and the buried grid, the substrate and the source electrode of the composite dielectric grid transistor are grounded, and photoelectrons originally accumulated at the interface of the substrate of the composite dielectric grid MOS capacitor and the bottom dielectric layer and the interface of the substrate in the cylindrical deep groove of the buried grid MOS capacitor and the insulating dielectric buried layer are drained away under the action of an electric field after a certain time.
The method comprises the steps of applying positive voltage to a selected control gate to be 0V-1V, applying negative voltage on a substrate to be-5V-3V, and applying voltage on a buried gate to be 0V-3V; in the second step, the drain electrode is connected with a proper positive voltage of 0.1-0.5V, and a proper ramp voltage of 1-5V is applied to the selected control grid electrode; in the third step, the negative bias voltage applied to the selected control grid is-3V to-1V.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (10)
1. A composite dielectric gate lateral collection photosensitive detection unit comprises a composite dielectric gate MOS capacitor and a composite dielectric gate transistor which are formed on the front surface of the same P-type semiconductor substrate, and is characterized in that: the composite dielectric gate MOS capacitor is positioned on the back surface of the P-type semiconductor substrate and is opposite to the central position of the composite dielectric gate MOS capacitor above the P-type semiconductor substrate, and the composite dielectric gate MOS capacitor and the composite dielectric gate transistor are separated in the P-type semiconductor substrate through a shallow slot isolation region.
2. The composite dielectric gate lateral collection photodetection unit according to claim 1, characterized in that: the composite dielectric gate MOS capacitor and the composite dielectric gate transistor have the following structures: and a bottom dielectric layer, a floating gate, a top dielectric layer and a control gate are sequentially arranged above the P-type semiconductor substrate, wherein the floating gate and the control gate are shared by the composite dielectric gate MOS capacitor and the composite dielectric gate transistor.
3. The composite dielectric gate lateral collection photodetection unit according to claim 2, characterized in that: the composite dielectric gate transistor is also provided with a source electrode and a drain electrode in the P-type semiconductor substrate; the buried gate MOS capacitor comprises a cylindrical deep groove which extends upwards from the back of a P-type semiconductor substrate to the inside of the substrate, a buried gate and an insulating medium buried layer are arranged in the cylindrical deep groove, the buried gate extends upwards from the bottom interface of the P-type semiconductor substrate along the central line of the cylindrical deep groove, and the insulating medium buried layer wraps the periphery of the buried gate with uniform thickness to isolate the buried gate from the P-type semiconductor substrate.
4. The composite dielectric gate lateral collection photodetection unit according to claim 1, characterized in that: the composite dielectric gate MOS capacitor realizes the photosensitive function of the detector, the composite dielectric gate transistor realizes the reading function of the detector, and the buried gate MOS capacitor realizes the auxiliary collection function of the detector.
5. The composite dielectric gate lateral collection photodetection unit according to claim 2, characterized in that: the bottom dielectric layer, the top dielectric layer and the insulating dielectric buried layer are all made of wide bandgap materials.
6. The composite dielectric gate lateral collection photodetection unit according to claim 5, characterized in that: the bottom dielectric layer and the insulating dielectric buried layer are made of silicon oxide or silicon oxynitride; the top dielectric layer is made of silicon oxide-silicon nitride-silicon oxide, silicon oxide-aluminum oxide-silicon oxide, silicon oxide or aluminum oxide.
7. The composite dielectric gate lateral collection photodetection unit according to claim 3, characterized in that: the floating gate is made of polycrystalline silicon; the control grid and the buried grid are made of polysilicon, metal or transparent conductive electrodes.
8. A composite dielectric grid lateral collection photosensitive detector based on the photosensitive detection unit of claim 3, wherein: the photosensitive detection units are arranged to form a detection array, in the detection array, drain terminals of composite dielectric gate transistors of each row of photosensitive detection units are connected to form a bit line i, wherein i is any positive integer, and the maximum value of i is the row number of the detection array; the source ends of the composite dielectric gate transistors of all the photosensitive detection units are connected to form a common source; the control gates of the photosensitive detection units in each row are respectively connected to form a word line j, wherein j is any positive integer, and the maximum value of j is the number of rows of the detection array; the buried gates of each row of photosensitive detection units are connected to form a buried gate line k, wherein k is any positive integer, and the maximum value of k is the row number of the detection array; the P-type semiconductor substrates of all the photosensitive detection units are shared; the photosensitive detection units are separated by shallow trench isolation regions on the front side of the substrate and deep trench isolation regions on the back side of the substrate.
9. A method for operating a composite dielectric grid lateral collection photosensitive detector as claimed in claim 8, comprising the steps of: collecting photoelectrons: applying zero or positive voltage on the control gate, applying negative voltage on the substrate, applying voltage between the control gate voltage and the substrate voltage on the buried gate, collecting photoelectrons formed in a depletion region of the P-type semiconductor substrate to an interface between the P-type semiconductor substrate and an insulating medium buried layer in a deep groove of the buried gate MOS capacitor, and further transporting the photoelectrons to an interface between the substrate and a bottom dielectric layer of the composite medium gate MOS capacitor along the interface;
optoelectronic readout and amplification: grounding the source electrode of the composite dielectric gate transistor, keeping the negative voltage applied in the exposure process of the substrate unchanged, connecting the drain electrode of the composite dielectric gate transistor with a positive voltage, and applying a slope voltage to the control gate to scan the threshold value; directly measuring two values of threshold voltage before and after exposure, comparing the two values, and determining the magnitude of an optical signal;
resetting of the photoelectrons: negative bias is applied to the control grid and the buried grid, the substrate and the source electrode of the composite dielectric grid transistor are grounded, and photoelectrons originally accumulated at the interface of the substrate of the composite dielectric grid MOS capacitor and the bottom dielectric layer and the interface of the substrate in the cylindrical deep groove of the buried grid MOS capacitor and the insulating dielectric buried layer are drained away under the action of an electric field after a certain time.
10. The method of claim 9, wherein the composite dielectric grid lateral collection photosensitive detector comprises: the method comprises the steps that positive voltage is applied to a selected control gate to be 0V-1V, negative voltage is applied to a substrate to be-5V-3V, and voltage applied to a buried gate is 0V-3V; in the second step, the drain electrode is connected with a proper positive voltage of 0.1-0.5V, and a proper ramp voltage of 1-5V is applied to the selected control grid electrode; in the third step, the negative bias voltage applied to the selected control grid is-3V to-1V.
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