CN115084288A - Spiral silicon drift detector and design method - Google Patents

Spiral silicon drift detector and design method Download PDF

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CN115084288A
CN115084288A CN202210728334.5A CN202210728334A CN115084288A CN 115084288 A CN115084288 A CN 115084288A CN 202210728334 A CN202210728334 A CN 202210728334A CN 115084288 A CN115084288 A CN 115084288A
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ring
cathode
spiral
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孙佳雄
李正
李晓丹
蔡新毅
谭泽文
李鑫卿
王洪斐
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Ludong University
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Abstract

The invention discloses a spiral silicon drift detector, which comprises a base body, wherein the front surface and the back surface of the base body are in the same regular hexagon and are aligned in parallel, the center of the front surface of the base body is an anode for collecting electrons, a spiral ring cathode spirally extending outwards along a hexagonal track is wound outside the anode, and the spiral ring cathode is positioned in a boundary ring at the edge part of the base body; the reverse side of the substrate is a reverse cathode. The invention also discloses a design method of the spiral silicon drift detector. The detector of the invention adopts a hexagonal matrix and a spiral ring cathode, and bias voltage is applied on the hexagonal matrix and the spiral ring cathode to form a uniform voltage gradient, so that the electron distribution of an electron drift channel in a silicon substrate is ensured to be uniform, and the detection performance is favorably improved.

Description

Spiral silicon drift detector and design method
Technical Field
The invention relates to the technical field of semiconductor detectors, in particular to a spiral silicon drift detector and a design method thereof.
Background
The silicon drift detector is a semiconductor detector for detecting energy beams, is based on the particularity of the structure of the silicon material and the superior electrical characteristics, and has important application in the aspects of modern medicine, nuclear technology, high-resolution X-ray spectrum and the like along with the improvement of scientific technology and the continuous and perfect process.
Under the working state of reverse bias voltage, the silicon drift detector generates electron-hole pairs around the drift path, can convert the energy of the energy beam into an electric signal which can be output, and after the electric signal is subjected to signal analysis, the signal reflects the characteristics of the energy beam, thereby achieving the purpose of detection.
The spiral silicon drift detector is a main product of an SDD family, the working principle of the spiral silicon drift detector can be regarded as a PN junction, and due to the geometrical structural characteristics of the spiral silicon drift detector, ion implantation is used as a rectifying junction and a voltage divider, and a potential gradient (or a drift field) is required to be created for the drift of carriers generated by incident particles to a collecting anode.
Compared with other types of detectors, the spiral silicon drift detector is simpler in process manufacturing, a planar process is applied, only heavy doping is carried out on the surface of a silicon substrate, doping is carried out in an ion implantation mode, a P pole and an N pole are formed through different doping concentrations, and the process cost is relatively low due to the simple process manufacturing. When the silicon substrate is in work, proper reverse bias voltage is applied to the central anode to enable the whole silicon substrate to reach a depletion state, so that an electron distribution similar to an electron channel is formed in the silicon substrate, the channel is very obvious, and the silicon substrate has good performance in work sensitivity, frequency response speed, collection efficiency and position resolution. The spiral silicon drift detector in the present stage is very wide in practical application due to low cost and excellent working performance.
The Chinese patent document with publication number CN 110350044A discloses a square spiral silicon drift detector and a preparation method thereof, which comprises a substrate with a round n + collecting anode, a square spiral cathode and a front protection ring on the front surface, wherein the square spiral cathode is distributed around the n + collecting anode, the width of the square spiral cathode is gradually widened from inside to outside, and the front protection ring is distributed around the spiral cathode; the back side of the substrate is provided with a back side electrode, an incident window and a back side protection ring, the incident window and the back side electrode are tightly connected and are both positioned in the back side protection ring, and the polarity of the back side electrode is a cathode. The scheme solves the problem that a detector array structure formed by circular spiral silicon drift detectors is not compact, and the difference of the distances from the anode to the points on the spiral cathode ring of the same level is large, so that the uniformity of electron distribution of electron drift channels in a silicon substrate is poor, and the detection performance is influenced.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a spiral silicon drift detector and a design method thereof, which are used for solving the problem of poor electron distribution uniformity of an electron drift channel in the prior art.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a spiral silicon drift detector comprises a base body with the front surface and the back surface being in the same regular hexagon and aligned in parallel, wherein the center of the front surface of the base body is an anode for collecting electrons, a spiral ring cathode which extends spirally outwards along a hexagonal track is wound outside the anode, and the spiral ring cathode is positioned in a boundary ring at the edge part of the base body; the reverse side of the substrate is a reverse cathode.
Furthermore, gaps between the spiral ring rings of adjacent ring stages of the spiral ring cathode are in an arithmetic progression in the radial direction, and the width of the spiral ring cathode is gradually increased along an outward extending spiral track, so that after bias voltage is applied, the voltage is automatically divided to form uniform voltage gradient, and an electron drift channel formed in the matrix tends to a plane.
Further, the cathode structure comprises a hexagonal cathode ring positioned between an anode and a spiral ring cathode, wherein the anode is in a regular hexagon shape, and the hexagonal cathode ring is similar to the anode in a concentric mode.
Further, the anode, the spiral ring cathode and the hexagonal cathode ring are aligned towards corresponding angles in six directions, and the starting point of the spiral ring cathode is located at the position of the angle.
Further, the surfaces of the anode, the hexagonal cathode rings and the cathode on the back side are covered with aluminum electrode contact layers, and the area among the spiral ring cathode rings on the front side of the substrate is covered with a SiO2 film.
Further, the size of the matrix is 3000 microns multiplied by 300 microns, the radius of the circumscribed circle of the anode is 60 microns, the radius of the circumscribed circle of the hexagonal cathode ring is 70 microns, the ring width is 20 microns, the distance from the starting point of the spiral ring cathode to the center of the front surface of the matrix is 100 microns, the number of ring-level turns of the spiral ring cathode is 21 turns, the tolerance of the inter-ring gap is 10 microns, the radius of the circumscribed circle of the reverse cathode is 3000 microns, the inner diameter of the boundary ring is 2940 microns, and the ring width is 60 microns;
the doping concentration of the matrix is 4 multiplied by 10 11 /cm 3 And the doping depth is 1 mu m, and the doping concentration of the anode is 1 multiplied by 10 19 /cm 3 N-type heavy doping with doping depth of 1 μm, wherein the doping concentration of the spiral ring cathode, the reverse cathode and the boundary ring is 1 × 10 19 /cm 3 And the doping depth is 1 mu m.
The invention also discloses a design method of the spiral silicon drift detector, which comprises the following steps:
s1, determining the voltage V of the outermost ring stage of the spiral ring cathode in the applied bias voltage value out Voltage V of innermost ring stage E1 And inter-ring gap g, thickness d of the base body, innermost ring radius r 1 Radius R of outermost ring, dielectric constant ε, resistivity ρ s The current I;
s2, calculating the angle of any point on the spiral ring cathode relative to the starting point: phi is a I ＝4ρ s α I, wherein α is a constant coefficient of 6;
s3, the calculation formula of the intermediate process is as follows:
Figure BDA0003711642790000031
where x is σ 2 r 2ε -1，x 1 ＝σ 2 r 1 2ε -1，n＝0,1,2,3…，
Figure BDA0003711642790000033
r is angle of following spiral ring
Figure BDA0003711642790000034
The radius that continuously extends outwards is provided,
Figure BDA0003711642790000035
for a continuously increasing arc in the helical rotation, r 1 Is the radius of the innermost ring;
s4, calculating the equation of the intermediate process according to the equations in S2 and S3
Figure BDA0003711642790000036
S5, calculating the spiral following ring angle according to the formula in S4
Figure BDA0003711642790000037
Radius extending continuously outward
Figure BDA0003711642790000038
S6, obtaining the width of the spiral ring cathode according to the formula in S4
Figure BDA0003711642790000039
And the inter-ring gap p (r) of two adjacent rings ω (r) + g;
s7, calculating depletion voltage
Figure BDA00037116427900000310
Wherein N is eff Effective doping concentration of silicon matrix N-type light doping, q is charge amount of each electron q is 1.6 multiplied by 10 -19 C，ε 0 Is a vacuum dielectric constant ε 0 ＝8.854×10 -12 F/m，ε Si Is the relative dielectric constant ε of silicon Si ＝11.9。
Further, the voltage V out 110V, voltage V E1 10V, the tolerance g of the gap between the rings is 10 μm, the thickness d of the substrate is 300 μm, and the radius r 1 100 μm, radius R of the outermost ring 2500 μm, resistivity ρ s 2000(ψ · cm), dielectric constant ∈ 1, and current I ═ 0.05 mA.
The spiral structure adopted by the scheme has the function of automatic voltage division, after different bias voltages are added on the innermost side and the outermost side of the spiral ring, an even voltage gradient can be automatically formed, so that automatic voltage division is achieved, the anode for collecting electrons is made in the center of the front side of the detector, the spiral ring on the front side is the cathode, and the whole surface of the back side is made into the cathode.
Drawings
FIG. 1 is a schematic, front-side perspective view of a detector in accordance with an embodiment of the invention.
FIG. 2 is a schematic, reverse side-up perspective view of a detector in accordance with an embodiment of the invention.
FIG. 3 is an enlarged view of a portion of a detector in a top-view front view in accordance with an embodiment of the invention.
Figure 4 is an X-axis cross-sectional view of a detector in an embodiment of the invention.
FIG. 5 is a diagram illustrating the simulation of the electric field of the detector at a voltage of-35V for the outermost ring of the front spiral ring cathode and-33V for the back cathode in one embodiment of the present invention.
FIG. 6 is a diagram showing potential simulation of the detector at voltages of-35V for the outermost ring of the front spiral ring cathode and-33V for the back cathode in one embodiment of the present invention.
FIG. 7 is a simulated electron concentration plot of the detector at-35V for the outermost ring of the front spiral ring cathode and-33V for the back cathode in one embodiment of the present invention.
In the figure: 1. an anode; 2. a hexagonal cathode ring; 3. s i O 2 A film; 4. a spiral ring cathode; 5. starting point of spiral ring cathode;6. a boundary ring; 7. the end of the spiral ring cathode; 8. an aluminum electrode contact layer covering the anode; 9. an aluminum electrode contact layer covered on the hexagonal cathode ring; 10. and the aluminum electrode contact layer is covered on the reverse cathode.
Detailed Description
Technical solutions in the embodiments of the present disclosure will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only some embodiments of the present disclosure, not all embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed in the present application without making any creative effort, shall fall within the scope of the protection of the present disclosure.
The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present disclosure unless specifically stated otherwise.
Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
The present invention will be described in further detail with reference to the following embodiments and the accompanying drawings.
A spiral silicon drift detector is shown in figures 1-4, and comprises a base body with front and back surfaces in the shape of the same regular hexagon and aligned in parallel, wherein the center of the front surface of the base body is an anode 1 for collecting electrons, a spiral ring cathode 4 which is spirally outward and extends along a hexagonal track is surrounded on the outside of the anode 1, the spiral ring cathode 4 is positioned in a boundary ring 6 at the edge part of the base body, and the tail end 7 of the spiral ring cathode 4 at the outermost ring stage is at a certain distance from the boundary ring 6; the reverse side of the substrate is a reverse side cathode.
The spiral structure adopted by the cathode has an automatic voltage division function, and after different bias voltages are applied to the innermost and outermost sides of the spiral ring, an even voltage gradient can be automatically formed, so that automatic voltage division is achieved, the center of the front surface of the detector is made into an anode 1 for collecting electrons, and the whole back surface of the detector is made into a cathode.
Because the negative electrode on the back surface is a whole-surface electrode, the capacitance needs to be reduced in order to reduce leakage current and noise, and therefore the anode 1 is designed in the center and has a small area, so that the capacitance is reduced, and the energy resolution of the detector is ensured. Meanwhile, the whole cathode is convenient to pressurize, so that the optimal voltage value is convenient to test, and the electronic drift channel is more straight; besides, the structure is simpler in manufacturing process, the process steps can be greatly reduced, the manufacturing is simpler, and the electronic integration is more convenient. The boundary ring 6 is a guard ring which protects the voltage at the outermost ring electrode from breakdown.
Compared with a quadrilateral silicon drift detector, the scheme adopts the hexagonal base body and the spiral ring cathode 4, the distribution of the spiral ring cathode 4 is closer to a circle, the distance between the anode 1 and the cathode is more uniform and the symmetry is better, and a uniform voltage gradient can be formed by applying bias voltage on the spiral ring cathode, so that the uniform distribution of electrons of an electron drift channel in a silicon substrate is ensured, a better electron drift channel is obtained, and the detection performance is favorably improved. Simultaneously, compare in circular shape base member, this scheme adopts the hexagon, and it is when as array unit, can closely arrange, and no space can realize surveying no dead zone between the unit.
As a preferred embodiment, the gaps between the spiral ring cathodes 4 of adjacent ring stages of the spiral ring cathodes 4 are in an arithmetic progression in the radial direction, and the widths of the spiral ring cathodes 4 gradually increase along the spiral tracks extending outwards, so that after bias voltage is applied, automatic voltage division is performed to form a uniform voltage gradient, an electron drift channel formed in the matrix tends to be a plane, and an optimal electron drift channel can be obtained.
The helical ring gap is the distance between the outer boundary of a certain ring of the helical ring cathode 4 and the inner boundary of an adjacent ring outside, so the pitch p (r) between the rings is the sum of the width w (r) of the current ring and the helical ring gap. The cathode structure can effectively and controllably adjust the width w (r) of the spiral ring cathode 4 and the pitch P (r) between the rings, thereby achieving better surface electric field distribution and straightening a drift channel. And in the design, the surface electric field can be effectively adjusted according to the actual situation to realize the optimal carrier drift electric field, so that the function optimization of the detector is realized. When particles are injected from the incident surface of the detector, an electric field distribution parallel to the surface is formed between the front surface and the back surface, so that an optimal electron drift channel can be obtained.
The cathode structure also comprises a hexagonal cathode ring 2 positioned between the anode 1 and the spiral ring cathode 4, wherein the anode 1 is in a regular hexagon shape, and the hexagonal cathode ring 2 is similar to the anode 1 in a concentric manner, namely, the distance between each side of the hexagonal cathode ring 2 and each side of the anode 1 is equal.
The hexagonal cathode ring 2 plays a buffering role, for example, when the outermost ring of the spiral ring cathode 4 is at-35V and the reverse surface is at-33V, the pressurization is at-2V, a voltage between the anode 1(0V) and the first ring of the spiral ring cathode 4 (the voltage of the innermost ring of the spiral ring cathode 4 is at-6V) is automatically adjusted, and meanwhile, the electric field distribution is more uniform, so that a better electronic channel is obtained.
In order to achieve the optimal cathode arrangement density and uniformity, the anode 1, the spiral ring cathode 4 and the hexagonal cathode ring 2 are aligned towards corresponding angles in six directions, and the starting point 5 of the spiral ring cathode 4 is positioned at the position of the angle.
As shown in fig. 4, the front electrode of the detector contacts with the anode 1 in a hexagonal shapeThe cathode ring 2, the innermost initial position of the spiral ring cathode 4, the outermost end position of the spiral ring cathode 4 and the boundary ring 6 are defined, the whole reverse side is defined by electrode contact, and the positions with the electrode contact are all covered by an aluminum film with the thickness of 1 mu m. The front surface without electrode contact was covered with S to a depth of 0.5. mu.m i O 2 The membrane 3 is used for preventing the silicon substrate from being oxidized, and the inter-ring area of the spiral ring cathode 4 on the front surface of the substrate is covered with S i O 2 And (3) a membrane. In fig. 4, an aluminum electrode contact layer 8 covered on the anode 1 and an aluminum electrode contact layer 9 covered on the hexagonal cathode ring 2 correspond to the front electrode of the detector; the aluminum electrode contact layer 10 covered by the negative cathode corresponds to the negative electrode of the detector.
As a specific example, a size of 3000 μm × 3000 μm × 300 μm, a radius of a circumscribed circle of the anode 1 is 60 μm, a radius of a circumscribed circle of the hexagonal cathode ring 2 is 70 μm and a ring width is 20 μm, a distance from a starting point 5 of the spiral ring cathode 4 to a center of the front surface of the substrate is 100 μm, a number of ring steps of the spiral ring cathode 4 is 21, a tolerance of an inter-ring gap is 10 μm, a radius of a circumscribed circle of the back surface cathode is 3000 μm, and an inner diameter of the boundary ring 6 is 2940 μm and a ring width is 60 μm.
The doping concentration of the matrix is 4 multiplied by 10 11 /cm 3 And the doping depth is 1 mu m, and the doping concentration of the anode 1 is 1 multiplied by 10 19 /cm 3 N-type heavy doping with doping depth of 1 μm, wherein the spiral ring cathode 4, the reverse cathode, and the boundary ring 6 have doping concentration of 1 × 10 19 /cm 3 And the doping depth is 1 mu m.
When the detector is designed, the optimal surface potential distribution of electrons is calculated by using theory, the surface electric field and the gap tolerance between rings are given, and the specific structure size and the internal structure of the detector are designed. The design method comprises the following steps:
s1, determining the voltage V of the outermost ring stage of the spiral ring cathode in the applied bias voltage value out Voltage V of innermost ring stage E1 Resistivity rho s And other given quantities: tolerance g of the inter-ring gap, thickness d of the substrate, innermost ring radius r 1 The radius R of the outermost ring,dielectric constant epsilon, current I;
s2, calculating the angle of any point on the spiral ring cathode relative to the starting point: phi is a I ＝4ρ s Alpha I, alpha is a constant coefficient of 6;
s3, the calculation formula of the intermediate process is as follows:
Figure BDA0003711642790000071
where x is σ 2 r 2ε -1，x 1 ＝σ 2 r 1 2ε -1，n＝0，1，2，3…，
Figure BDA0003711642790000072
r is angle of following spiral ring
Figure BDA0003711642790000073
The radius that continuously extends outwards is provided,
Figure BDA0003711642790000074
for a continuously increasing arc in the helical rotation, r 1 Is the radius of the innermost ring;
s4, calculating the formula of the intermediate process according to the formulas in S2 and S3
Figure BDA0003711642790000075
The derivation is carried out by surface potential:
Figure BDA0003711642790000076
solving sigma to obtain the formula;
s5, calculating the spiral following ring angle according to the formula in S4
Figure BDA0003711642790000077
Radius extending continuously outward
Figure BDA0003711642790000078
r increases with increasing helical loop extension;
s6, obtaining the width of the spiral ring cathode according to the formula in S4
Figure BDA0003711642790000079
And the inter-ring gap p (r) ═ ω (r) + g of two adjacent rings, as shown in fig. 3;
s7, calculating depletion voltage
Figure BDA0003711642790000081
Wherein N is eff Effective doping concentration of silicon matrix N-type light doping, q is charge amount of each electron q is 1.6 multiplied by 10 -19 C，ε 0 Is a vacuum dielectric constant ε 0 ＝8.854×10 -12 F/m，ε Si Is the relative dielectric constant ε of silicon Si ＝11.9。
The given parameters of the formula of the steps can be changed according to the actual situation. As said voltage V out 110V, voltage V E1 10V, the tolerance g of the gap between the rings is 10 μm, the thickness d of the substrate is 300 μm, and the radius r 1 100 μm, the radius R of the outermost ring 2500 μm, the dielectric constant ∈ 1, and the current I0.05 mA.
The surface electric field can be effectively adjusted according to the actual situation in the design so as to realize the optimal carrier drift electric field, thereby realizing the optimization of the function of the detector. By combining the data of the above embodiments, a detector of a specific product can be designed, and a simulation test is performed on the detector, when a bias voltage is applied, the voltage of the outermost ring stage of the spiral ring cathode is-35V, the voltage of the innermost ring stage is-6V, and the voltage of the reverse side cathode is-33V, and the test results are shown in fig. 5-7, it can be seen that the electric field distribution is uniform, the potential distribution is in a gradient which tends to be smooth and the like, and the electron concentration in the electron drift channel is consistent. The obtained electron drift channel approaches to a plane and approaches to the theoretical optimal electron drift channel form.
Compared with a concentric ring detector which does not have the automatic voltage division function, different bias voltages need to be applied to each concentric ring of the concentric ring detector when pressurization is needed to ensure that the rings change according to a certain voltage gradient, and obviously, the detector is simpler to operate when in use. The manufacturing process technology of the three-dimensional detector has certain difficulties, the effect of an etching area is poor during etching, the doping positions of different levels are different, the process is very complicated, and a silicon substrate can generate an area with a small electric field or an area with a zero electric field; according to the scheme, the wafer defects can be eliminated by using a zone melting method in the gettering oxidation process link, a double-sided photoetching alignment mark manufacturing process is used in the photoetching mark manufacturing link, a set of mark point mask plates are added before photoetching to align the position of a detector, double-sided process single-sided photoetching is used in the ion implantation process link, the front side and the back side are completed separately during manufacturing, and the back side glue homogenizing is dried and protected during front side process.
The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles and embodiments of the present invention are explained herein by using specific examples, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention; meanwhile, for a person skilled in the art, according to the embodiments of the present invention, there may be variations in the specific implementation manners and application ranges, and in summary, the content of the present description should not be construed as a limitation to the present invention.

Claims (8)

1. A spiral silicon drift detector, characterized by: the anode is externally wound with a spiral ring cathode which is spirally outward and extends along a hexagonal track, and the spiral ring cathode is positioned in a boundary ring at the edge part of the substrate; the reverse side of the substrate is a reverse cathode.
2. A spiral silicon drift detector according to claim 1, wherein: the gaps between the spiral ring rings of adjacent ring stages of the spiral ring cathode are in an equal difference array in the radial direction, and the width of the spiral ring cathode is gradually increased along an outward extending spiral track, so that after bias voltage is applied, automatic voltage division is performed to form uniform voltage gradient, and an electronic drift channel formed in the matrix tends to be a plane.
3. A spiral silicon drift detector according to claim 2, wherein: the cathode structure also comprises a hexagonal cathode ring positioned between the anode and the spiral ring cathode, wherein the anode is in a regular hexagon shape, and the hexagonal cathode ring is similar to the anode in a concentric mode.
4. A spiral silicon drift detector according to claim 3, wherein: the anode, the spiral ring cathode and the hexagonal cathode ring are aligned towards corresponding angles in six directions, and the starting point of the spiral ring cathode is located at the position of the angle.
5. A spiral silicon drift detector according to any of claims 1 to 4, wherein: the surfaces of the anode, the hexagonal cathode ring and the reverse cathode are covered with aluminum electrode contact layers, and the area among the spiral ring cathode rings on the front surface of the substrate is covered with S i O 2 And (3) a membrane.
6. The spiral silicon drift detector of claim 5, wherein: the size of the matrix is 3000 micrometers multiplied by 300 micrometers, the radius of the circumscribed circle of the anode is 60 micrometers, the radius of the circumscribed circle of the hexagonal cathode ring is 70 micrometers, the ring width is 20 micrometers, the distance from the starting point of the spiral ring cathode to the center of the front surface of the matrix is 100 micrometers, the number of ring-level turns of the spiral ring cathode is 21 circles, the tolerance of the inter-ring gap is 10 micrometers, the radius of the circumscribed circle of the cathode on the back surface is 3000 micrometers, and the inner diameter of the boundary ring is 2940 micrometers, and the ring width is 60 micrometers;
the doping concentration of the matrix is 4 multiplied by 10 11 /cm 3 And the doping depth is 1 mu m, and the doping concentration of the anode is 1 multiplied by 10 19 /cm 3 N-type heavy doping with doping depth of 1 μm, wherein the doping concentration of the spiral ring cathode, the reverse cathode and the boundary ring is 1 × 10 19 /cm 3 And the doping depth is 1 mu m.
7. The design method of the spiral silicon drift detector as claimed in any one of claims 1 to 6, comprising the steps of:
s1, determining the voltage V of the outermost ring stage of the spiral ring cathode in the applied bias voltage value out Voltage V of innermost ring stage E1 And inter-ring gap g, thickness d of the base body, innermost ring radius r 1 Radius R of the outermost ring, dielectric constant epsilon and current I;
s2, calculating the angle of any point on the spiral ring cathode relative to the starting point: phi is a I ＝4ρ s α I, wherein α is a constant coefficient of 6;
s3, the calculation formula of the intermediate process is as follows:
Figure FDA0003711642780000021
where x is σ 2 r 2ε -1，x 1 ＝σ 2 r 1 2ε -1，n＝0,1,2,3…，
Figure FDA0003711642780000022
r is angle of following spiral ring
Figure FDA0003711642780000029
The radius that continuously extends outward is the radius that,
Figure FDA0003711642780000023
for a continuously increasing arc in the helical rotation, r 1 Is the radius of the innermost ring;
s4, calculating the equation of the intermediate process according to the equations in S2 and S3
Figure FDA0003711642780000024
S5, calculating the spiral following ring angle according to the formula in S4
Figure FDA0003711642780000025
Radius extending continuously outward
Figure FDA0003711642780000026
S6, obtaining the width of the spiral ring cathode according to the formula in S4
Figure FDA0003711642780000027
And an inter-ring gap p (r) ═ ω (r) + g between two adjacent rings;
s7, calculating depletion voltage
Figure FDA0003711642780000028
Wherein N is eff Effective doping concentration of silicon matrix N-type light doping, q is charge amount of each electron q is 1.6 multiplied by 10 -19 C，ε 0 Is a vacuum dielectric constant ε 0 ＝8.854×10 -12 F/m，ε Si Is the relative dielectric constant ε of silicon Si ＝11.9。
8. The design method according to claim 7, wherein: the voltage V out 110V, voltage V E1 10V, the tolerance g of the gap between the rings is 10 μm, the thickness d of the substrate is 300 μm, and the radius r 1 100 μm, radius R of the outermost ring 2500 μm, resistivity ρ s 2000(ψ · cm), a dielectric constant ∈ 1, and a current I ═ 0.05 mA.
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