Electron bombardment photodetector unit and array with charge collection function

Abstract

The present invention discloses an electron bombardment photodetector unit and array with a charge collection function. The detector unit includes an incident region and a charge collection region. The front of the charge collection region is formed by injection into a central injection region, a first annular injection region, and a second annular injection region. The outer edge of the first annular injection region is connected to the inner edge of the second annular injection region, and an annular isolation region is formed between the central injection region and the first annular injection region. In the present invention, by improving the detector unit structure, a funnel-shaped charge collection electric field is formed within the detector unit, effectively improving the collection efficiency of the electron bombardment photodetector, thereby reducing the area of ​​the charge collection end, thereby reducing the node capacitance, and improving the charge conversion gain and signal processing bandwidth capability. It can also eliminate signal crosstalk caused by electron diffusion, and has excellent performance of high charge collection efficiency, high conversion gain, high bandwidth, and low crosstalk.

Description

Technical Field

[0001] The present invention belongs to the field of photoelectric detectors, and in particular relates to an electron bombardment photoelectric detector unit and an array with a charge collection function. Background Art

[0002] Electron-bombardment low-light-level imaging devices use photoelectrons generated by a photocathode to form an image directly on a photodetector after being accelerated by a high-voltage electric field. These devices offer advantages such as high sensitivity, fast response, compact size, and light weight, and have been widely used in fields such as low-light-level night vision, high-energy physics, and space observation. The spacing between the photocathode and the photodetector in electron-bombardment low-light-level imaging devices is typically around 0.5 mm to 1 mm. Photons incident on the photocathode generate photoelectrons that are accelerated by the high-voltage electric field and bombard the photodetector. Because the photoelectrons generated by the photocathode have a nearly Gaussian distribution, a 20 nm photoelectron beam accelerated through the 0.5 mm to 1 mm spacing can have a diffusion diameter of more than ten microns when it impacts the photodetector. In existing electron-bombardment photodetector structures, to ensure good spatial resolution, the N+ well collection region must cover the photoelectron diffusion diameter as much as possible to minimize the collection of secondary electrons by adjacent N+ wells. This introduces large junction capacitance, reduces charge conversion gain, and reduces the bandwidth capability of signal processing. Summary of the Invention

[0003] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide an electron bombardment photodetector unit and array with a charge collection function.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] An electron bombardment photodetector unit with a charge collection function comprises an incident area and a charge collection area arranged on the incident area, wherein the back side of the incident area forms an electron bombardment incident surface; the front side of the charge collection area is formed by injection into a central injection area, a first annular injection area, and a second annular injection area, wherein the first annular injection area is arranged inside the second annular injection area, and the outer edge of the first annular injection area is connected to the inner edge of the second annular injection area, and the central injection area is arranged inside the first annular injection area, and an annular isolation area is formed between the central injection area and the first annular injection area; the incident area is connected to a first electrode, the central injection area is connected to a second electrode, the second annular injection area is connected to a third electrode, and the first annular injection area is connected to a fourth electrode.

[0006] Furthermore, the incident region and the second annular injection region are both P+ regions, the charge collection region is an N- region, the central injection region is an N+ region, and the first annular injection region is a P region.

[0007] Furthermore, the potential of the second electrode is higher than the potential of the fourth electrode, the potential of the fourth electrode is higher than the potential of the first electrode, and the potential of the first electrode is higher than the potential of the third electrode, thereby forming a completely depleted region in the charge collection region except for the PiN junction region below the central injection region, and the PiN junction region below the central injection region is not completely depleted, forming a funnel-shaped non-completely depleted region.

[0008] Furthermore, the fourth electrode is located on one end of the first annular injection region away from the second annular injection region, so that the fourth electrode, the third electrode, the second annular injection region and the first annular injection region form a gradually varying resistance voltage divider structure.

[0009] Furthermore, the shape and size of the inner edge of the second annular injection region are the same as the shape and size of the outer edge of the first annular injection region, so that the second annular injection region and the first annular injection region are connected as a whole; or

[0010] The shape of the inner edge of the second annular injection area is the same as the shape of the outer edge of the first annular injection area, and the size of the inner edge of the second annular injection area is smaller than the size of the outer edge of the first annular injection area, so that the second annular injection area and the first annular injection area are connected as a whole by overlapping.

[0011] Furthermore, the central injection region is circular, and the first annular injection region and the isolation region are both annular; or

[0012] The central injection region is square, and the first annular injection region and the isolation region are both square annular; or

[0013] The central injection region is in the shape of a regular N-gon, and the first annular injection region and the isolation region are both in the shape of a regular N-gon ring; wherein N is an integer greater than or equal to 5.

[0014] Furthermore, the depth of the second annular injection region is greater than the depth of the central injection region and the depth of the first annular injection region.

[0015] Furthermore, the incident region is formed by a substrate, and the charge collection region is formed by an epitaxial layer.

[0016] Furthermore, the charge collection region is formed by thinning the single crystal substrate, and the incident region is formed by injection on the back side of the single crystal substrate.

[0017] An electron bombardment photodetector array with a charge collection function comprises a plurality of detection units arranged in a two-dimensional array form, wherein the detection units are electron bombardment photodetector units with a charge collection function.

[0018] In the present invention, by improving the detector unit structure, a funnel-shaped charge collection electric field is formed inside the detector unit, which effectively improves the collection efficiency of the electron bombardment photodetector, thereby reducing the area of ​​the charge collection end, thereby reducing the node capacitance, and improving the charge conversion gain and signal processing bandwidth capabilities; and can form an electron potential barrier at the edge of the detector unit to prevent secondary electrons from diffusing to adjacent detector units, eliminating signal crosstalk caused by electron diffusion; it can be used for electron bombardment low-light-level imaging, and can obtain excellent performance of high charge collection efficiency, high conversion gain, high bandwidth and low crosstalk. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 It is a structural diagram of an electron bombardment type photodetector unit in the prior art.

[0021] Figure 2 FIG. 1 is a structural diagram of an electron bombardment photodetector unit with charge collection function according to an embodiment of the present invention.

[0022] Figure 3 This is a top view of the detector unit when the central injection area is circular.

[0023] Figure 4 This is a top view of the detector unit when the central injection area is square.

[0024] Figure 5 This is a top view of the detector unit when the central injection region is a regular hexagon.

[0025] Figure 6 Schematic diagram of the structure of the fully depleted region and the non-fully depleted region.

[0026] Figure 7 Schematic diagram of the distribution of the funnel-shaped electric field formed inside the detector unit.

[0027] Figure 8 Schematic diagram of the structure of an electron bombardment photodetector array with charge collection function according to an embodiment of the present invention.

[0028] The accompanying drawings in this specification are numeraled as follows:

[0029] Detection unit-100; incident region-110; electron bombardment incident surface-111; charge channel region-120; central injection region-130; first annular injection region-140; second annular injection region-150; isolation region-160; completely depleted region-170; non-completely depleted region-171; first electrode-181; second electrode-182; third electrode-183; fourth electrode-184; potential of the first electrode-191; potential of the second electrode-192; potential of the third electrode-193; potential of the fourth electrode-194; electron bombardment type photodetector unit-900; first P+ region-910; P-epitaxial layer-920; N+ well region-930; depletion layer-940; second P+ region-950; secondary electrons-960. DETAILED DESCRIPTION

[0030] The following describes the implementation of the present invention through specific examples. The illustrations provided in the following embodiments are only used to schematically illustrate the basic concept of the present invention. The following embodiments and features in the embodiments may be combined with each other unless there is any conflict.

[0031] See also Figure 1 The electron bombardment type photodetector unit 900 in the prior art includes a first P+ region 910, a P- epitaxial layer 920, an N+ well region 930 and a second P+ region 950. A depletion layer 940 is formed around the N+ well region 930. The N+ well region 930 forms an N+ well collection region ( Figure 1 Figure 1 shows two electron-bombarded photodetector units 900 separated by a dotted line. When accelerated high-energy electrons bombard the electron-bombarded photodetector unit 900, they pass through the first P+ region 910 into the P-epitaxial layer 920, where they collide with atoms within the silicon body, generating a large number of secondary electrons 960. After a large number of secondary electrons 960 diffuse to the depletion layer 940, they are accelerated by the electric field and collected in the N+ well region 930. The collected electrons are then converted and output by the readout circuit. To ensure that the electron-bombarded imaging device has good spatial resolution, the area of ​​the N+ well collection region (i.e., the N+ well region 930) needs to cover the photoelectron diffusion diameter as much as possible to reduce the collection of secondary electrons 960 by the adjacent N+ well region 930. However, increasing the area of ​​the N+ well region 930 will introduce a large junction capacitance, which, on the one hand, reduces the charge conversion gain, and on the other hand, reduces the bandwidth capability of the signal processing. In addition, in the prior art, in order to achieve isolation between the electron-bombarded photodetector units 900, the depletion layer 940 cannot fully cover the P-region (i.e., the P-epitaxial layer 920). Therefore, the secondary electrons 960 at the edge of the electron-bombarded photodetector unit 900 will diffuse to the adjacent area, increasing the signal crosstalk between the electron-bombarded photodetector units 900.

[0032] The accompanying drawings in this specification are numeraled as follows:

[0033] See also Figure 2 , Figure 2 The figure is a schematic structural diagram of an embodiment of an electron bombardment photodetector unit with a charge collection function according to the present invention. The electron bombardment photodetector unit and array with a charge collection function according to this embodiment include an incident region 110 and a charge channel region 120 disposed on the incident region 110. In this embodiment, the incident region 110 is a P+ region, and the charge channel region 120 is an N- region. The incident region 110 can be formed by a substrate, and the charge channel region 120 can be formed by an epitaxial layer. Of course, the charge channel region 120 can also be formed by thinning a single crystal substrate, and then forming the incident region 110 by implantation on the back side of the single crystal substrate.

[0034] The back side of the incident area 110 forms an electron bombardment incident surface 111, and the front side of the charge channel area 120 is formed by injection into a central injection area 130, a first annular injection area 140, and a second annular injection area 150. The first annular injection area 140 and the second annular injection area 150 are both annular surrounding structures, and the depth of the second annular injection area 150 is greater than the depth of the central injection area 130 and the depth of the first annular injection area 140. It should be noted that the front and back sides are only for the convenience of describing the device structure according to the drawings, and do not represent the front and back sides of the device when it is actually used. In this embodiment, the central injection area 130 is an N+ area, the first annular injection area 140 is a P area, and the second annular injection area 150 is a P+ area. The first annular injection area 140 is arranged inside the second annular injection area 150, and the outer edge of the first annular injection area 140 is connected to the inner edge of the second annular injection area 150. The central injection area 130 is arranged inside the first annular injection area 140, and an annular isolation area 160 is formed between the central injection area 130 and the first annular injection area 140.

[0035] The shape of the outer edge of the second annular injection area 150 is generally consistent with the shape of the outer edge of the detector unit, and the shape and size of the inner edge of the second annular injection area 150 are generally the same as the shape and size of the outer edge of the first annular injection area 140, so that the second annular injection area 150 and the first annular injection area 140 are connected as a whole. Of course, the inner edge of the second annular injection area 150 can also only have the same shape as the outer edge of the first annular injection area 140, and the size of the inner edge of the second annular injection area 150 can be smaller than the size of the outer edge of the first annular injection area 140, so that the second annular injection area 150 and the first annular injection area 140 are connected as a whole by overlapping.

[0036] See also Figure 3In this embodiment, the detector unit is square, so the outer edge of the second annular injection area 150 is also square; the central injection area 130 is circular, and the first annular injection area 140 and the isolation area 160 are both annular. Of course, the central injection area 130 and the first annular injection area 140 can also be of other shapes. Figure 4 , the central injection region 130 can also be square, in which case the first annular injection region 140 and the isolation region 160 are both square ring-shaped. Of course, the central injection region 130 can also be other regular polygons such as regular pentagons and regular hexagons, in which case the first annular injection region 140 and the isolation region 160 are both corresponding regular polygon rings. For example, see Figure 5 When the central injection region 130 is a regular hexagon, the first annular injection region 140 and the isolation region 160 are both regular hexagonal rings.

[0037] The incident region 110 is connected to a first electrode 181, the central injection region 130 is connected to a second electrode 182, the second annular injection region 150 is connected to a third electrode 183, and the first annular injection region 140 is connected to a fourth electrode 184. The fourth electrode 184 is located on an end of the first annular injection region 140 away from the second annular injection region 150 (i.e., close to the central injection region 130) to facilitate the formation of a voltage drop between the third electrode 183 and the fourth electrode 184, thereby forming a gradually varying resistance voltage divider structure with the fourth electrode 184, the third electrode 183, the second annular injection region 150, and the first annular injection region 140.

[0038] During operation, the potential 192 of the second electrode is higher than the potential 194 of the fourth electrode, the potential 194 of the fourth electrode is higher than the potential 191 of the first electrode, and the potential 191 of the first electrode is higher than the potential 193 of the third electrode, thereby forming a completely depleted region 170 in the charge collection region except for the PiN junction region below the central injection region 130 (the isolation region 160 forms a completely depleted region 170), and the PiN junction region below the central injection region 130 is not completely depleted, forming a funnel-shaped non-completely depleted region 171.

[0039] The working principle of this embodiment is as follows:

[0040] See also Figure 6 and Figure 7Based on existing theories, when a potential difference is formed between two points, electrons will move in the direction of higher potential. By applying a negative voltage to the first electrode 181, the second electrode 182, the third electrode 183 and the fourth electrode 184, wherein the potential 192 of the second electrode is higher than the potential 194 of the fourth electrode, the potential 194 of the fourth electrode is higher than the potential 191 of the first electrode, and the potential 191 of the first electrode is higher than the potential 193 of the third electrode, except for the incomplete depletion of the PiN junction in the bottom area of ​​the central injection area 130, the other parts of the charge channel area 120 are completely depleted, and a potential and electric field channel for the electron charge can be formed from the incident area 110 and the second annular injection area 150 to the collection end (i.e., the central injection area 130). It should be noted that Figure 7 The voltage units are negative, although, Figure 7 The absolute value of the voltage at the upper point is greater than the absolute value of the voltage at the lower point, but Figure 7 The electric potential of the point in the upper center is lower than that of the point in the lower center.

[0041] When the detector unit is operating, the absolute value of the negative voltage in the incident region 110 connected to the first electrode 181 and the second annular injection region 150 connected to the third electrode 183 is higher than the internal voltage of the charge channel region 120, thereby forming an electric field extending from the center of the charge channel region 120 to both sides. A gradually varying surface resistive voltage divider structure is formed between the first annular injection region 140 connected to the fourth electrode 184 and the second annular injection region 150 connected to the third electrode 183. This interacts with the voltage of the central injection region 130 to form an electric field extending from the central injection region 130 to the lateral periphery. The interaction between these divided electric fields creates a funnel-shaped electric field distribution within the electron-bombarded photodetector unit. Because electrons migrate against the electric field, the secondary electrons generated by the bombardment drift toward the center of the funnel and are ultimately collected by the central injection region 130. This funnel-shaped charge collection electric field reduces the area of ​​the central injection region 130 at the charge collection end, lowering junction capacitance, thereby improving charge conversion gain and increasing the bandwidth capability of signal processing. The aforementioned second annular injection region 150, charge channel region 120 and incident region 110 form an N-channel JFET structure below the second annular injection region 150. When the fully depleted region 170 pinches off the channel, an electron potential barrier is formed to prevent secondary electrons from diffusing to adjacent detector units, thereby effectively reducing signal crosstalk between detector units.

[0042] In this embodiment, by improving the detector unit device structure and coordinating the interaction of the voltages of each electrode, a funnel-shaped charge collection electric field is formed inside the device, effectively improving the collection efficiency of the electron bombardment photodetector. The electron collection efficiency is increased from approximately 60% in the prior art to close to 100%, making it possible to use a small-area charge collection terminal, thereby reducing node capacitance and improving charge conversion gain and signal processing bandwidth capabilities. In addition, this embodiment forms an electron potential barrier at the edge of the detector unit, preventing secondary electrons from diffusing to adjacent detector units, eliminating signal crosstalk caused by electron diffusion. It can be used for electron bombardment-type low-light-level imaging, and can achieve excellent performance of high charge collection efficiency, high conversion gain, high bandwidth, and low crosstalk.

[0043] See also Figure 8 , Figure 8 The structure diagram of an embodiment of an electron bombardment photodetector array with charge collection function of the present invention is shown in FIG. This embodiment includes a plurality of detection units 100 arranged in a two-dimensional array. The detection units 100 are electron bombardment photodetector units with charge collection function as described in any of the above embodiments.

[0044] The above embodiments merely represent preferred embodiments of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An electron bombardment photodetector unit with charge collection function, characterized in that: The invention comprises an incident area and a charge collection area arranged on the incident area, wherein the back side of the incident area forms an electron bombardment incident surface; the front side of the charge collection area is formed by injection into a central injection area, a first annular injection area, and a second annular injection area, wherein the first annular injection area is arranged inside the second annular injection area, and the outer edge of the first annular injection area is connected to the inner edge of the second annular injection area, and the central injection area is arranged inside the first annular injection area, and an annular isolation area is formed between the central injection area and the first annular injection area; the incident area is connected to a first electrode, the central injection area is connected to a second electrode, the second annular injection area is connected to a third electrode, and the first annular injection area is connected to a fourth electrode; The incident area and the second annular injection area are both P+ areas, the charge collection area is an N- area, the central injection area is an N+ area, and the first annular injection area is a P area; The potential of the second electrode is higher than the potential of the fourth electrode, the potential of the fourth electrode is higher than the potential of the first electrode, and the potential of the first electrode is higher than the potential of the third electrode, so that the area in the charge collection area except the PiN junction area below the central injection area forms a completely depleted area, and the PiN junction area below the central injection area is not completely depleted, forming a funnel-shaped non-completely depleted area.

2. The electron bombardment photodetector unit with charge collection function according to claim 1, wherein: The fourth electrode is located on one end of the first annular injection region away from the second annular injection region, so that the fourth electrode, the third electrode, the second annular injection region and the first annular injection region form a gradually changing resistance voltage dividing structure.

3. The electron bombardment photodetector unit with charge collection function according to claim 1, wherein: The shape and size of the inner edge of the second annular injection region are the same as the shape and size of the outer edge of the first annular injection region, so that the second annular injection region and the first annular injection region are connected as a whole; or The shape of the inner edge of the second annular injection area is the same as the shape of the outer edge of the first annular injection area, and the size of the inner edge of the second annular injection area is smaller than the size of the outer edge of the first annular injection area, so that the second annular injection area and the first annular injection area are connected as a whole by overlapping.

4. The electron bombardment photodetector unit with charge collection function according to claim 1, wherein: The central injection region is circular, and the first annular injection region and the isolation region are both annular; or The central injection region is square, and the first annular injection region and the isolation region are both square annular; or The central injection region is in the shape of a regular N-gon, and the first annular injection region and the isolation region are both in the shape of a regular N-gon ring; wherein N is an integer greater than or equal to 5.

5. The electron bombardment photodetector unit with charge collection function according to claim 1, wherein: The depth of the second annular injection region is greater than the depth of the central injection region and the depth of the first annular injection region.

6. The electron bombardment photodetector unit with charge collection function according to any one of claims 1 to 5, characterized in that: The incident region is formed by a substrate, and the charge collection region is formed by an epitaxial layer.

7. The electron bombardment photodetector unit with charge collection function according to any one of claims 1 to 5, characterized in that: The charge collection region is formed by thinning a single crystal substrate, and the incident region is formed by implantation on the back side of the single crystal substrate.

8. An electron bombardment photodetector array with charge collection function, characterized in that: The invention comprises a plurality of detection units arranged in a two-dimensional array, wherein the detection units are electron bombardment photodetector units with charge collection function as claimed in any one of claims 1 to 7.

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