Through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate

Abstract

The invention provides a through-type three-dimensional quasi-hemispherical electrode detector based on an SOI substrate, and the detector comprises a cubic substrate, the center of the upper surface of the substrate is a central electrode; an anode aluminum electrode contact layer covers the upper surface of the central anode; an upper surface SiO2 layer covers the part, which is not covered with the anode aluminum electrode contact layer, of the upper surface of the substrate; the SOI substrate heavily doped layer is arranged at the bottom of the base body, and the substrate is arranged at the lower part of the SOI substrate heavily doped layer; a middle SiO2 layer is arranged between the SOI substrate heavily doped layer and the substrate; grooves between the four side faces of the base bodies and the adjacent base bodies form groove walls. The heavily doped layer of the SOI substrate and the groove wall form a cathode; a cathode aluminum electrode contact layer covers the surface of the groove between the adjacent substrates; and the bottom surface SiO2 layer covers the bottom surface of the substrate. The problem that a low electric field region and a zero electric field region exist in an unetched region in the prior art is solved, meanwhile, the charge collection performance is improved, and the effective size of the detector is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon detectors and relates to a through-type three-dimensional quasi-hemispherical electrode detector based on an SOI substrate. Background Art

[0002] Silicon detectors are widely used in aerospace, medical, industrial flaw detection, safety detection, nuclear radiation monitoring, and research and development of large scientific facilities due to their excellent performance and mature preparation process. The basic principle is to use particles or other radiation to generate electron-hole pairs in the silicon matrix. The generated electron-hole pairs drift under the action of an external electric field to stimulate electrical signals. Internationally, the preparation technology of silicon semiconductor detectors is already quite mature. The preparation process mainly includes ion implantation, chemical vapor deposition (CVD), physical vapor deposition (PVD), magnetron sputtering, electron beam evaporation and photolithography. In terms of subsequent processes, foreign countries have also formed relatively mature process flows, such as chemical cleaning, annealing and packaging. These processes can make silicon semiconductor detectors have better stability and reliability. In China, the preparation technology of silicon semiconductor detectors is also developing continuously, but there is still a slight gap compared with the international level. First, the domestic preparation technology still needs to further improve the accuracy and repeatability. Secondly, there are still large technical bottlenecks in technologies such as CVD and PVD in China.

[0003] Compared with two-dimensional planar detectors, three-dimensional detectors have obvious advantages in information acquisition, spatial positioning, depth perception, visualization and analysis capabilities, and automation efficiency, which makes it widely used and promoted in many fields. First, in terms of charge collection performance, the study of charge collection performance has important performance in high-energy particle detection, X-ray detection, low-light imaging, etc. The quality of charge collection performance also determines the efficiency and accuracy of detection; secondly, the unetched area of ​​the traditional three-dimensional groove electrode detector will have a low electric field area or a zero electric field area, which reduces the effective volume of the detector. Avoiding the dead zone inside the detector has also become one of the focuses of studying three-dimensional groove detectors.

[0004] Therefore, there is an urgent need for a simple and effective three-dimensional detector to improve the charge collection performance and increase the effective volume of the detector. Summary of the invention

[0005] In order to achieve the above-mentioned objectives, the present invention provides a through-type three-dimensional quasi-hemispherical electrode detector based on an SOI substrate, which solves the problem of low electric field regions and zero electric field regions existing in the unetched areas in the prior art, while improving the charge collection performance and increasing the effective volume of the detector.

[0006] The technical solution adopted by the present invention is:

[0007] A through-type three-dimensional quasi-hemispherical electrode detector based on an SOI substrate comprises: a substrate, which is in the shape of a cube, and the center of the upper surface of the substrate is a central electrode; the upper surface of the central anode is covered with an anode aluminum electrode contact layer; the upper surface of the substrate not covered with the anode aluminum electrode contact layer is covered with an upper surface SiO2 layer; an SOI substrate heavily doped layer is arranged at the bottom of the substrate, and a substrate is arranged at the lower part of the SOI substrate heavily doped layer; an intermediate SiO2 layer is arranged between the SOI substrate heavily doped layer and the substrate; grooves between the four side surfaces of the substrate and adjacent substrates constitute groove walls; the SOI substrate heavily doped layer and the groove walls constitute a cathode; the groove surface between adjacent substrates is covered with a cathode aluminum electrode contact layer; and the bottom surface of the substrate is covered with a bottom surface SiO2 layer.

[0008] Furthermore, the length and width of the substrate are both 80-100 um, and the height is both 40-50 um; the groove spacing between adjacent substrates is 10-20 um.

[0009] Furthermore, the matrix doping type is N-type light doping, and the matrix doping concentration is 4×10 11 -1×10 12 / cm 3 .

[0010] Furthermore, the central anode is circular.

[0011] Furthermore, the central anode doping type is N-type heavy doping, the doping depth is 0.5-1um, and the central anode doping concentration is 4×10 18 -1×10 19 / cm 3 .

[0012] Furthermore, the trench wall doping type is P-type heavy doping, and the doping depth is 0.5-1um.

[0013] Furthermore, the doping concentration of the trench wall is 4×10 18 -1×10 19 / cm 3 .

[0014] Furthermore, the doping type of the heavily doped layer of the SOI substrate is P-type heavily doped.

[0015] Furthermore, the doping concentration of the heavily doped layer of the SOI substrate is 4×10 18 -1×10 19 / cm 3 .

[0016] Furthermore, the electrode spacing between each groove wall and the central anode is equal, which is 40-50 um.

[0017] Beneficial effects of the present invention:

[0018] 1. The electric field distribution of the detector of the present invention is quasi-hemispherical, and its electric field distribution is more uniform and not affected by angles, and can further reduce the readout capacitance and full depletion voltage.

[0019] 2. The traditional three-dimensional groove electrode cannot be fully etched, which results in the existence of a dead zone in the unetched part. This results in a reduction in the effective volume of the detector and a reduction in the charge collection efficiency. Compared with the traditional three-dimensional groove electrode detector, the unit structure design of the quasi-hemispherical electrode of the present invention theoretically avoids the existence of a dead zone, thereby improving the charge collection rate of the new detector unit. There is almost no zero electric field zone inside the detector of the present invention.

[0020] 3. Since the electrode distance between the cathode and the anode of the present invention is small, the detector full depletion voltage is greatly reduced. In the absence of irradiation, the detector depletion voltage is only 2.4V, and the leakage current is reduced at the same time, so the energy consumption is lower and the radiation resistance is stronger.

[0021] 4. Since there is a 10-20um groove spacing between each cuboid unit, it has a good isolation effect on the detector unit and reduces the interference between the detector units. Therefore, the detector units are effectively isolated, thereby reducing the crosstalk effect between the detector units.

[0022] 5. The detector of the present invention achieves the electrical performance of a spherical detector, and does not involve a complicated process flow, and only requires processes such as etching grooves and ion implantation to form electrodes. Compared with a spherical detector, the detector of the present invention has a simpler process and is easier to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is the overall structural diagram of the detector of the present invention.

[0025] Figure 2 It is a top view of the detector of the present invention.

[0026] Figure 3 It is a left side view of the detector of the present invention.

[0027] Figure 4 It is a cross-sectional view of the detector of the present invention along the X-axis.

[0028] Figure 5 is the electron concentration of the detector of the present invention along the Z axis.

[0029] Figure 6 yes Figure 5 A partial enlarged view of .

[0030] Figure 7 It is a leakage current curve diagram of the detector of the present invention.

[0031] Figure 8 It is the leakage current curve of the traditional three-dimensional detector.

[0032] Fig. 9 It is an electric field simulation diagram of the cross section of the detector of the present invention along the X-axis at a voltage of 2.4V.

[0033] Fig.10 It is a potential simulation diagram of the cross section of the detector of the present invention along the X-axis at a voltage of 2.4V.

[0034] Fig.11 It is a simulation diagram of the electron concentration of the cross section of the detector of the present invention along the X-axis at a voltage of 2.4V.

[0035] Fig.12 It is the potential distribution diagram of the detector unit of the present invention.

[0036] Fig.13 This is the electric field distribution diagram of the traditional columnar electrode three-dimensional detector.

[0037] In the figure, 1. anode aluminum electrode contact layer, 2. central anode, 3. upper surface SiO2 layer, 4. substrate, 5. groove wall, 6. cathode aluminum electrode contact layer, 7. middle SiO2 layer, 8. bottom SiO2 layer, 9. SOI substrate heavily doped layer, 10. substrate. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 1-Figure 4 The detector structure of the present invention is a 3×3 array. The detector contains 9 rectangular units with a length and width of 80-100um and a height of 40-50um. The groove spacing between the rectangular units is 10-20um. Each rectangular unit includes a substrate 4, which is lightly doped with N type and has a doping concentration of 4×10 11 -1×10 12 / cm 3; Too high a doping concentration of the matrix will result in: increasing the conductivity of the device, generating leakage current, and reducing the insulation performance of the device; too high a doping concentration will increase the carrier lifetime and diffusion length, causing the response speed of the device to decrease, thereby affecting the cutoff frequency of the device. Too high a doping concentration will reduce the carrier collection efficiency, reduce the sensitivity and detection performance of the device. Too low a doping concentration will result in: reducing the conductivity of silicon, resulting in a decrease in the conductivity of the device, affecting the performance stability of the device; limiting the carrier lifetime and diffusion length, causing the device response speed to decrease, affecting the frequency response characteristics of the device; reducing the carrier collection efficiency, reducing the signal sensitivity and detection performance of the device.

[0040] The center of the upper surface of the substrate 4 is the central electrode 2, which is doped with N-type heavy doping, with a diameter of 10um, a depth of 0.5-1um, and a doping concentration of 4×10 18 -1×10 19 / cm 3 The heavy doping concentration is obtained by dividing the ion implantation concentration by the implantation depth. If the doping concentration is too low, the silicon crystal obtained will not have the performance as good as a conductor, while too high a doping concentration will make it difficult to recover the silicon crystal and require cumbersome operations such as cooling. A higher doping concentration will make it difficult to remove the photoresist and the process will be more difficult. Therefore, if the doping concentration is too low, it will not play the role of an electrode, and if the doping concentration is too high, the subsequent process will become cumbersome.

[0041] The upper surface of the central anode 2 is covered with an anode aluminum electrode contact layer 1, and the thickness of the anode aluminum electrode contact layer 1 is 1 μm; the upper surface of the substrate 4 not covered with the anode aluminum electrode contact layer 1 is covered with an upper surface SiO2 layer 3 to prevent the substrate 4 from being oxidized in the air; facing the silicon detector, the four sides of each detector unit and the grooves between the rectangular units together form a groove wall 5, and the doping type of the groove wall 5 is P-type heavy doping, the depth is 0.5-1 μm, and the doping concentration is 4×10 18 -1×10 19 / cm 3 ; If the doping of the trench wall is too high, the following problems may occur: excessive doping will cause the electric field distribution between the trench wall and the bottom to change, increase the counter-effect, and reduce the electron collection efficiency; excessive doping will increase the carrier concentration near the trench wall, prolong the charge diffusion time, and affect the time resolution of the detector; excessive doping affects energy deposition and resolution, and reduces the energy resolution of the detector. If the doping of the trench wall is too low, it will lead to: the electric field near the trench wall is weak, reducing the collection efficiency of carriers in the trench and affecting the sensitivity of the detector; too low doping reduces the amplification factor and reduces the gain performance of the device; too low doping will also increase the charge diffusion time and affect the time resolution.

[0042] The groove surface between the rectangular parallelepiped units is covered with a cathode aluminum electrode contact layer 6 , and the thickness of the cathode aluminum electrode contact layer 6 is 1 μm; the bottom surface of the entire detector is covered with a bottom surface SiO2 layer 8 .

[0043] In each rectangular unit, a SOI substrate heavily doped layer 9 is arranged at a distance of 40.5-51 um from the top of the detector, and an intermediate SiO2 layer 7 is arranged between the SOI substrate heavily doped layer 9 and the substrate 10; the doping concentration of the SOI substrate heavily doped layer 9 is 4×10 18 -1×10 19 / cm 3 , excessive doping will cause changes in the electric field distribution, increase the counter-attack effect, and reduce the electron collection efficiency; excessive doping will increase the carrier concentration, prolong the charge diffusion time, and affect the time resolution of the detector; excessive doping affects energy deposition and resolution, and reduces the energy resolution of the detector. If the doping is too low, it will lead to: the electric field in the vicinity is weak, reducing the carrier collection efficiency in the groove and affecting the sensitivity of the detector; too low doping reduces the amplification factor and reduces the gain performance of the device; too low doping will also increase the charge diffusion time and affect the time resolution. The doping type is P-type heavy doping, which together with the groove wall 5 constitutes the cathode of the detector. Therefore, the groove wall 5 surrounds the central anode 2, and the electrode spacing between each groove wall 5 and the central anode 2 is equal. The spacing between the central anode 2 and the groove wall 5 is 40-50um. Therefore, the potential gradient of the detector after pressurization is quasi-hemispherical, such as Fig.12 shown.

[0044] Figure 5 is the electron concentration of the detector of the present invention along the Z axis. The external bias voltage is 1.0V-2.5V. By changing the external bias voltage of the detector, it can be seen that the electron concentration of the silicon detector of the present invention decreases as the external bias voltage increases.

[0045] Figure 6 yes Figure 5 A local enlarged view. It can be seen that when the sensitive area of ​​the detector of the present invention reaches the fully depleted state, its electron concentration no longer changes with the increase of the applied bias voltage, and the depletion voltage is 2.4V, which has reached a relatively small order of magnitude; the fully depleted voltage refers to the minimum reverse bias required to achieve complete depletion of the volume between the anode and cathode. After applying a reverse bias to the detector, the depletion region will expand with the increase of the applied voltage until it reaches a fully depleted state. And compared to the traditional three-dimensional groove electrode detector, the detector of the present invention has a point-shaped central anode, and therefore has a lower capacitance.

[0046] Figure 7 It is a leakage current curve diagram of the detector of the present invention. Figure 8 is the leakage current curve of the traditional three-dimensional detector, and its horizontal axis is the absolute value of the applied bias voltage. It can be seen that the leakage current of the traditional detector is 10 -8At the order of 10 -9 Therefore, under the same bias voltage, the leakage current of the detector of the present invention is small, and the low leakage current directly reduces the power consumption of the detector in the working state, so that the power consumption of the detector of the present invention is lower.

[0047] Fig. 9 This is an electric field simulation diagram of the cross section of the detector along the X axis at a voltage of 2.4 V. It can be seen that the detector forms an obvious electron drift channel at a low voltage of 2.4 V, and most areas of the detector are high electric field areas, that is, the electric field strength is higher than 300 V / m. When the voltage reaches the full depletion voltage of 2.4 V, the internal electric field reaches all parts of the detector, and the zero electric field area almost disappears. Fig.13 The traditional columnar electrode three-dimensional detector has a saddle-shaped low electric field or zero electric field area, that is, a dead zone, formed inside the detector. The zero electric field area almost does not exist inside the detector of the present invention.

[0048] Fig.10 It is a potential simulation diagram of the cross section of the detector of the present invention along the X-axis at a voltage of 2.4V. It can be seen that the potential distribution of the detector of the present invention at a bias voltage of 2.4V is very uniform and symmetrical, and the gradient distribution is obvious. The uniform potential gradient is conducive to charge collection. In order to ensure that free electrons drift to the anode and are collected by the anode, the detector is reverse biased, so the potential of the central anode 2 is the highest.

[0049] Fig.11 This is a simulation diagram of the electron concentration of the detector along the X-axis at a voltage of 2.4V. It can be seen that when the bias voltage is applied to about 2.4V, the electron concentration in the depletion region almost does not change, forming a clear electron movement trend track, which is consistent with the above Fig. 9 The carrier orbits formed by the electric field distribution correspond to each other.

[0050] The invention points of the present invention:

[0051] 1. The detector area of ​​the present invention achieves full penetration, that is, a heavily doped layer is formed from the top to the bottom of the detector unit, achieving full penetration of the entire groove wall 5 height, and achieving full penetration from the central anode 2 to the cathode area.

[0052] 2. The detector of the present invention adopts a rectangular parallelepiped detector unit. In each unit, the distance between the central anode 2 and the groove wall 5 is equal, achieving the electrical performance of a spherical detector.

[0053] 3. The present invention combines SOI technology and does not involve complicated process flow, but only requires processes such as etching grooves and ion implantation to form electrodes.

[0054] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate, comprising: The substrate (4) is characterized in that the substrate (4) is in the shape of a cube, the center of the upper surface of the substrate (4) is a central electrode (2); the upper surface of the central anode (2) is covered with an anode aluminum electrode contact layer (1); the upper surface of the substrate (4) not covered with the anode aluminum electrode contact layer (1) is covered with an upper surface SiO2 layer (3); an SOI substrate heavily doped layer (9) is arranged at the bottom of the substrate (4), and a substrate (10) is arranged at the bottom of the SOI substrate heavily doped layer (9); an intermediate SiO2 layer (7) is arranged between the SOI substrate heavily doped layer (9) and the substrate (10); the grooves between the four side surfaces of the substrate (4) and the adjacent substrates (4) constitute groove walls (5); the SOI substrate heavily doped layer (9) and the groove walls (5) constitute cathodes; the groove surfaces between the adjacent substrates (4) are covered with cathode aluminum electrode contact layers (6); and the bottom surface of the substrate (10) is covered with a bottom surface SiO2 layer (8).

2. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 1, characterized in that: The length and width of the substrate (4) are both 80-100 um, and the height is both 40-50 um; the groove spacing between adjacent substrates (4) is 10-20 um.

3. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 2, characterized in that: The doping type of the substrate (4) is N-type light doping, and the doping concentration of the substrate (4) is 4×10 11 -1×10 12 / cm 3 .

4. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 1, characterized in that: The central anode (2) is circular.

5. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 4, characterized in that: The doping type of the central anode (2) is N-type heavy doping, the doping depth is 0.5-1um, and the doping concentration of the central anode (2) is 4×10 18 -1×10 19 / cm 3 .

6. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 1, characterized in that: The doping type of the groove wall (5) is P-type heavy doping, and the doping depth is 0.5-1 um.

7. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 6, characterized in that: The doping concentration of the trench wall (5) is 4×10 18 -1×10 19 / cm 3 .

8. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 1, characterized in that: The doping type of the SOI substrate heavily doped layer (9) is P-type heavily doped.

9. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to claim 8, characterized in that: The doping concentration of the SOI substrate heavily doped layer (9) is 4×10 18 -1×10 19 / cm 3 .

10. The through-type three-dimensional quasi-hemispherical electrode detector based on SOI substrate according to any one of claims 1 to 9, characterized in that: The electrode spacing between each groove wall (5) and the central anode (2) is equal, which is 40-50 um.

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