A spiral ring electrode silicon array detector

Abstract

The present invention discloses a spiral ring electrode silicon array detector, which relates to the technical field of radiation detection. The area of its spiral ring electrode is much smaller than that of the traditional full-surface electrode, with smaller leakage current and capacitance, low noise and high energy resolution. According to the existing process, the pixels can be made at the micro-nano level, and the position resolution is very high. The detector can flexibly set the biasing method. The design of the spiral ring enables the electrode to have sufficient space to be used as a readout electrode or apply a bias voltage. The specific solution is as follows: It includes a cylindrical substrate. On the top surface of the substrate, there is a cathode composed of a doped spiral ring electrode and a central electrode. The central electrode is located in the center of the spiral ring electrode, and the spiral ring electrode surrounds the central electrode. The number of spiral rings of the spiral ring electrode is K, where K is a positive integer. The bottom surface of the substrate is an anode formed by doping. There is an electrode contact layer on the top surface electrode of the substrate, and SiO2 is covered where there is no electrode contact layer. There is an electrode contact layer on the full-surface electrode of the bottom surface of the substrate.

Description

Technical Field

[0001] The present invention relates to the field of radiation detection technology, and more specifically, to a spiral ring electrode silicon array detector. Background Art

[0002] Detectors are mainly used in high-energy physics, astrophysics, etc. Silicon detectors have high detection sensitivity, fast response speed, strong radiation resistance, and are easy to integrate. They have important application value in high-energy particle detection and X-ray detection.

[0003] Silicon detectors work under reverse bias. When external particles are incident on the sensitive area inside the detector, electron-hole pairs are generated under the action of the applied voltage. The positive electrode collects the electrons that drift to the positive electrode, while the holes move toward the negative electrode and are collected by the negative electrode, and then output an electrical signal reflecting the particle information to the external circuit.

[0004] The pixel detector is made up of an orderly array of pixel units. Its basic principle is the same as that of many other types of detectors, which is a PN junction or a PIN junction. Each pixel detector unit consists of a sensitive area that plays a sensing role and an external electron readout part. When a charged particle is incident into the sensitive area, an electron-hole pair will be generated, which will drift toward the positive and negative poles under the action of an external electric field. After being collected by the two poles, the feedback current signal is processed by an external integrated circuit to obtain information about the energy, position, and movement trajectory of the incident particle.

[0005] Compared with other types of detectors, the manufacturing technology of pixel detectors has gradually matured and the manufacturing process is easier than other complex structure detectors (such as silicon drift chamber detectors, three-dimensional columnar detectors, etc.). It also has a relatively low cost and still maintains relatively outstanding performance at work, which makes pixel detectors more widely used. After selecting the appropriate depletion layer thickness, the output current that can be obtained is larger, the sensitivity is higher, the frequency response characteristics are better, and the position resolution is also higher.

[0006] A sensitive factor in silicon detectors is the size of the capacitor, because the capacitor will directly affect the noise and crosstalk when the detector is working. The anode and cathode of the entire plane of the traditional pixel silicon detector are covered by metal electrodes. Although the triangular and square arrays make the electrode arrangement very orderly, the effective electrode area of ​​this detector will be very large, and the large electrode area will cause the detector to have a larger capacitance. Too large a capacitance is not good for the detector. The larger the capacitance, the more leakage current and more noise, which ultimately reduces the energy resolution of the detector. Therefore, one of the main research directions for improving the performance of silicon detectors is to reduce the capacitance. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a spiral ring electrode silicon array detector. Compared with the traditional pixel detector, the area of ​​the spiral ring electrode is much smaller than the traditional whole-surface electrode area, the leakage current and capacitance are smaller, the noise is small and the energy resolution is high; according to the existing process, the pixels can be achieved at the micro-nano level and the position resolution is very high; the detector can flexibly set the pressurization method, and the design of the spiral ring allows the electrode to have enough space to serve as a readout electrode or apply a bias voltage.

[0008] The above technical objectives of the present invention are achieved through the following technical solutions:

[0009] A spiral ring electrode silicon array detector comprises a columnar substrate, wherein a cathode formed by a spiral ring electrode formed by doping and a central electrode is provided on the top surface of the substrate, the central electrode is located in the middle of the spiral ring electrode, the spiral ring electrode surrounds the central electrode, the number of spiral rings of the spiral ring electrode is K, K is a positive integer, and the bottom surface of the substrate is an anode formed by doping; an electrode contact layer is provided on the electrode on the top surface of the substrate, SiO2 is covered in the area without the electrode contact layer, and the electrode contact layer is provided on the entire electrode on the bottom surface of the substrate.

[0010] In the above scheme, when the K value is smaller, the area required for the entire spiral electrode is smaller, but a higher voltage is required and the depletion effect is worse; therefore, the K value needs to be selected according to different situations.

[0011] As a preferred solution, the spiral electrode is in the shape of a circular spiral ring, a square spiral ring or a regular polygonal spiral ring; the columnar substrate is in the shape of a cylinder, a square column or a regular polygonal column.

[0012] In the above preferred embodiments, the shape of the spiral electrode and the columnar substrate can be combined arbitrarily to achieve the purpose of detection.

[0013] As a preferred solution, the spiral ring electrode is a circular spiral ring, and the columnar substrate is a circular column.

[0014] In the above preferred embodiment, the cylindrical substrate is designed as a circular column, which can make the electric field distribution in the detector unit more uniform; when a square column is used while a circular spiral ring electrode silicon is used, the spiral ring electrode is far away from the four corners of the cylindrical substrate, which easily generates a low electric field area, or requires a higher voltage, and the effect is relatively poor. When a circular column is used while a square spiral ring electrode silicon is used, the electric field distribution uniformity is poor, similar to the above case.

[0015] As a preferred solution, the spiral ring electrode is a square spiral ring, and the columnar substrate is a square column.

[0016] As a preferred solution, the spiral ring electrode is a regular n-sided polygon, n≥6, and the columnar substrate is a regular m-sided column, m≥n.

[0017] In the above preferred solution, the positive n-sided type, the larger the n value, the closer to a circle, the better the electric field uniformity effect, but the difficulty of array arrangement and placement is high. There are dead angles in the arrangement and placement of cylindrical substrates.

[0018] As a preferred solution, the cathode is doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 The anode is doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 The N-type doping depth is 1μm; the matrix is ​​doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 N-type doping.

[0019] In summary, the present invention has the following beneficial effects:

[0020] (1) Compared with traditional pixel detectors, the area of ​​its spiral ring electrode is much smaller than that of the traditional whole surface electrode, with smaller leakage current and capacitance, low noise and high energy resolution.

[0021] (2) The detector can be designed as a square, without dead corners, and can be easily arranged in an array. It can also be designed as a circular design, so that the electric field distribution in the detector unit is more uniform. The electric field of the hexagonal design unit is closest to circularity, and an array arrangement without dead zones can also be achieved.

[0022] (3) According to the existing technology, pixels can be achieved at the micro-nano level with very high position resolution.

[0023] (4) The detector can flexibly set the pressurization method, and the design of the spiral ring allows the electrode to have enough space to serve as a readout electrode or apply a bias voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

[0025] Figure 2 It is a schematic diagram of the overall top view structure of the present invention;

[0026] Figure 3 It is a schematic diagram of the side view structure of the detector of the present invention;

[0027] Figure 4 This is a schematic diagram of the top view structure of a 2x2 detector array of the present invention;

[0028] Figure 5 It is a schematic diagram of the top view structure of the conventional pixel silicon detector triangle array of the present invention;

[0029] Figure 6 It is a schematic diagram of the top view structure of the conventional square array of pixel silicon detectors of the present invention;

[0030] Figure 7 It is the potential schematic diagram and curve diagram of the present invention;

[0031] Figure 8 It is the electric field schematic diagram and curve diagram of the present invention;

[0032] Fig. 9 It is the electron concentration schematic diagram and curve diagram of the present invention;

[0033] In the figure:

[0034] 1. Semiconductor substrate; 2. Central square spiral ring electrode; 3. Center electrode; 4. Detector anode; 5. Electrode contact layer; 6. Silicon dioxide layer. DETAILED DESCRIPTION

[0035] This specification and claims do not distinguish components by name, but by functional differences. As mentioned in the specification and claims, "including" is an open term and should be interpreted as "including but not limited to". "Substantially" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect.

[0036] The directional terms such as up, down, left, right, etc. in this specification and claims are combined with the drawings for further explanation to make the present application more convenient to understand, and do not limit the present application. In different scenarios, up, down, left, right, inside and outside are all relative.

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0038] A spiral ring electrode silicon array detector comprises a columnar substrate, wherein a cathode formed by a spiral ring electrode formed by doping and a central electrode is provided on the top surface of the substrate, the central electrode is located in the middle of the spiral ring electrode, the spiral ring electrode surrounds the central electrode, the number of spiral rings of the spiral ring electrode is K, K is a positive integer, and the bottom surface of the substrate is an anode formed by doping; an electrode contact layer is provided on the electrode on the top surface of the substrate, SiO2 is covered in the area without the electrode contact layer, and the electrode contact layer is provided on the entire electrode on the bottom surface of the substrate.

[0039] In the above embodiment, when the K value is smaller, the area required for the entire spiral electrode is smaller, but a higher voltage is required and the depletion effect is worse; therefore, the K value needs to be selected according to different situations.

[0040] As a preferred embodiment, the spiral electrode is in the shape of a circular spiral ring, a square spiral ring or a regular polygonal spiral ring; the columnar substrate is in the shape of a cylinder, a square column or a regular polygonal column.

[0041] In the above preferred embodiments, the shape of the spiral electrode and the columnar substrate can be arbitrarily combined to achieve the purpose of detection.

[0042] As a preferred embodiment, the spiral ring electrode is a circular spiral ring, and the columnar substrate is a circular column.

[0043] In the above preferred embodiment, the columnar substrate is designed as a circular column, which can make the electric field distribution in the detector unit more uniform; when a square column is used while a circular spiral ring electrode silicon is used, the spiral ring electrode is far away from the four corners of the columnar substrate, which easily produces a low electric field area, or requires a higher voltage, and the effect is relatively poor. When a circular column is used while a square spiral ring electrode silicon is used, the electric field distribution uniformity is poor, similar to the above case.

[0044] As a preferred embodiment, the spiral ring electrode is a square spiral ring, and the columnar substrate is a square column.

[0045] As a preferred embodiment, the spiral ring electrode is a regular n-sided polygon, n≥6, and the columnar substrate is a regular m-sided column, m≥n.

[0046] In the above preferred embodiment, the positive n-sided type, the larger the n value, the closer to a circle, the better the electric field uniformity effect, but the difficulty of array arrangement and placement is high. There are dead angles in the arrangement and placement of cylindrical substrates.

[0047] As a preferred embodiment, the cathode is doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 The anode is doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 The N-type doping depth is 1μm; the matrix is ​​doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 N-type doping.

[0048] Principle: The spiral ring electrode silicon array detector forms an M*N array detector by sharing the bottom anode electrode, where M and N are both positive integers.

[0049] The spiral ring electrode silicon array detector is a PIN junction: P-type semiconductor-intrinsic layer-N-type semiconductor, wherein the resistivity of heavily doped P / N-type semiconductor silicon is different from that of lightly doped P / N-type semiconductor silicon. Doping is performed on the top layer of the semiconductor substrate to form a square spiral ring electrode (2) and a central electrode 3. Then, the square spiral ring electrode 2 and the central electrode 3 are heavily doped with P-type silicon to form a cathode, the bottom anode electrode is heavily doped with N-type silicon, and the semiconductor substrate 1 is lightly doped with N-type silicon.

[0050] The semiconductor material of the semiconductor substrate 1 is a combination of one or more of Si, Ge, HgI2, GaAs, TiBr, CdTe, CdZnTe, CdSe, GaP, HgS, PbI2 and AlSb.

[0051] The electrode contact layer of the spiral ring electrode silicon array detector is an aluminum electrode contact layer, and the thickness of the electrode contact layer is 1 micron; the spiral ring electrode silicon array detector is not provided with an electrode contact layer, and an insulating layer is provided on the surface of the detector, the material of which is silicon dioxide, and the thickness of the silicon dioxide layer is 1 micron; the height of the spiral ring electrode silicon array detector is 100 to 500 microns; the width of the central electrode of the detector cathode is 15 microns, and the central electrode is symmetrically arranged about the axis of the central square spiral ring electrode.

[0052] Take a square detector unit as an example:

[0053] The general model of the detector is as follows Figure 1 As shown, there is a 80μm*80μm*300μm cubic column semiconductor substrate, the top layer is a cathode composed of a square spiral ring electrode and a central electrode, and the cathode is doped with a concentration of 1×10 19 / cm 3 The P-type heavy doping has a doping depth of 1 μm, the central electrode is located in the middle of the square spiral ring electrode, the square spiral ring electrode surrounds the central electrode, and the number of spiral rings of the square spiral ring electrode is K, where K is a positive integer, such as Figure 2 The top view of the detector is shown; the substrate is N-type lightly doped with a doping concentration of 8×10 11 / cm 3 The entire bottom layer is used as the anode of the detector, and the anode is doped with a concentration of 1×10 19 / cm 3 The N-type heavy doping has a doping depth of 1 μm; the top surface of the novel square spiral ring electrode silicon detector is provided with an electrode contact layer, the top surface without the electrode contact layer is covered with SiO2, and the entire bottom surface is provided with an electrode contact layer, such as Figure 3 shown.

[0054] The anode and cathode of the traditional pixel silicon detector are covered by metal electrodes, and the array of triangular and square electrodes is very orderly arranged, such as Figure 4 , 5 As shown, the effective electrode area of ​​the detector is large, and the large electrode area leads to a large capacitance of the detector. The spiral ring electrode silicon array position detector adopts a square spiral ring electrode design, and the electrode area is small, only about 40% of the top surface area.

[0055] The expression for the detector depletion voltage is:

[0056]

[0057] Spiral ring electrode silicon array detector where q is the charge carried by each electron q = 1.6×10 -19 C, N eff The effective doping concentration of silicon substrate N-type light doping is 8×10 11 / cm 3 , d is the thickness of the silicon substrate d = 300 μm, ε0 is the vacuum dielectric constant ε0 = 8.854 × 10 -12 F / m, ε Si is the relative dielectric constant ε of silicon Si =11.9, and V is obtained by the depletion voltage equation fd =54.7V.

[0058] This can be proved by deriving the relevant parameter formula of silicon detector:

[0059] 1. The smaller the electrode area, the smaller the detector capacitance;

[0060] 2. The detector has a small leakage current, which will make the detector perform better;

[0061] 3. The smaller the detector capacitance, the smaller the noise will be and the higher the sensitivity of the detector will be.

[0062] The junction capacitance of Si-PIN detector can be calculated as follows:

[0063]

[0064] D is the depletion layer thickness of the detector (for N-type silicon ρ n is the resistivity of N-type silicon (ψ·cm), V is the applied bias voltage (V bias ), S is the electrode area of ​​the detector (cm 2 ). The depletion layer thickness D affects the junction capacitance. The thicker the depletion layer, the smaller the junction capacitance. The smaller the electrode area S, the smaller the junction capacitance.

[0065] The relationship between bias voltage and depletion layer thickness is as follows:

[0066]

[0067] Where ε is the dielectric constant, ρ is the resistivity, and μ is the majority carrier mobility. The depletion layer thickness D of the Si-PIN detector changes with the bias voltage V bias As the bias voltage V bias And changes.

[0068] So when the detector is completely depleted, the bias voltage V bias The increase will not make the depletion layer thickness D larger, so after complete depletion, the detector junction capacitance C d The size is related to the electrode area.

[0069] Detector junction capacitance C d Proportional to the electrode area.

[0070] Effective parallel noise ENC par It can be expressed as:

[0071]

[0072] Among them I leak is the leakage current of the detector, t peak is the peak response time of the output signal. It can be seen that the effective parallel noise is proportional to the leakage current, so a smaller leakage current will make the detector perform better.

[0073] Effective series noise ENC series It can be expressed as:

[0074]

[0075] Among them C t is the total input capacitance of the detector, t peak is the peak response time of the output signal. It can also be seen that the relationship between capacitance and noise, when the capacitance of the detector is small, the noise will be smaller and the sensitivity of the detector will be higher.

[0076] Figure 7 .8.9 is a simulation diagram of the spiral ring electrode silicon array position detector. Figure 7 It can be seen that the potential distribution of the detector from bottom to top is very uniform; Figure 8 This is the electric field intensity distribution diagram. The electric field of the detector is evenly distributed and the electric field is relatively high, greater than 1000V, and there is no weak electric field. Fig. 9 It can be seen that the concentration in the depletion region at 55 V is almost a straight line, and the entire detector depletion region has been depleted.

[0077] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A spiral ring electrode silicon array detector, characterized in that: It comprises a columnar substrate, a cathode formed by a spiral ring electrode formed by doping and a central electrode is arranged on the top surface of the substrate, the central electrode is located in the middle of the spiral ring electrode, the spiral ring electrode surrounds the central electrode, the number of spiral rings of the spiral ring electrode is K, K is a positive integer, and the bottom surface of the substrate is an anode formed by doping; an electrode contact layer is arranged on the electrode on the top surface of the substrate, SiO2 is covered in the area without the electrode contact layer, and an electrode contact layer is arranged on the entire electrode on the bottom surface of the substrate; The spiral ring electrode is in the shape of a circular spiral ring, a square spiral ring or a regular polygonal spiral ring; the columnar substrate is in the shape of a cylinder, a square column or a regular polygonal column; The cathode is doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 The anode is doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 The N-type doping depth is 1 μm; the matrix is ​​doped with a concentration of 1×10 19 / cm 3 —1×10 21 / cm 3 N-type doping.

2. The spiral ring electrode silicon array detector according to claim 1, characterized in that: The spiral ring electrode is a circular spiral ring, and the columnar substrate is a circular column.

3. The spiral ring electrode silicon array detector according to claim 1, characterized in that: The spiral ring electrode is in the shape of a square spiral ring, and the columnar base is in the shape of a square column.

4. The spiral ring electrode silicon array detector according to claim 1, characterized in that: The spiral ring electrode is a regular n-sided polygon, n≥6, and the columnar substrate is a regular m-sided column, m≥n.

Images