CN218471961U - Hexagon spiral silicon drift detector - Google Patents

Abstract

The utility model discloses a hexagonal spiral silicon drift detector, including the positive and negative two sides for the same regular hexagon and parallel alignment's base member, the positive center of base member is the positive pole of collecting electron, and this positive pole outer loop is around having the spiral ring negative pole that the spiral outwards, extend along the hexagon orbit, the clearance in the radial direction of spiral ring inter-annular clearance of the adjacent ring level of spiral ring negative pole =10 mu m, the ring level number of turns of spiral ring negative pole is 21 circles, and spiral ring negative pole is located the border ring; the reverse side of the substrate is provided with a cathode. The utility model discloses a detector adopts hexagonal base member and spiral ring negative pole, and its positive pole is even to the distance between the negative pole, when as array unit, can closely arrange, and no space can be realized surveying no blind spot between the unit, is favorable to improving the detection performance.

Description

Hexagon spiral silicon drift detector

Technical Field

The utility model relates to a semiconductor detector technical field specifically is a hexagon spiral silicon drift detector.

Background

The silicon drift detector is a semiconductor detector for detecting energy beams, is based on the particularity of the structure of a silicon material and excellent electrical characteristics, and has important application in various aspects such as modern medicine, nuclear technology, high-resolution X-ray spectrum and the like along with the improvement of scientific technology and the continuous improvement of the 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 Silicon Drift Detector (SDD) is a core part in an X-ray fluorescence spectrometer, the performance of the SDD directly influences the working efficiency of the system, and the good detector has good energy resolution and high counting characteristic.

Chinese patent publication No. CN 209016068U, "a silicon drift detector based on a control surface electric field", includes a front surface electrode, a cylindrical n-type silicon body, and a rear surface electrode connected in sequence; the front surface electrode comprises a first p + type circular spiral cathode ring, wherein a closed cathode circular starting point ring, an inner closed cathode protection ring and an n + type circular anode are sequentially nested in the front surface electrode; a first closed cathode circular end ring and a first outer closed cathode protection ring are sequentially sleeved outside the last ring of the first p + type circular spiral cathode ring; the widths of the closed cathode circular starting ring, the inner closed cathode protection ring, the first closed cathode circular end ring, the first outer closed cathode protection ring and the first p + type circular spiral cathode ring are equal; the rear surface electrode comprises a second p + type circular spiral cathode ring embedded with a circular cathode connected with a first ring of the second p + type circular spiral cathode ring, and a second closed cathode circular end ring and a second outer closed cathode protection ring are sequentially sleeved outside the last ring of the second p + type circular spiral cathode ring.

Although the technical scheme disclosed by the patent document has a progressive significance in overcoming the problems of excessive leakage current, overlarge dead zone, poor drift electric field and the like, the electrode shapes and structures on the two sides are complex, and the process manufacturing difficulty is increased; and the array formed by the array is large in arrangement gap, and dead zones exist in detection.

Disclosure of Invention

To the weak point among the above-mentioned prior art, the utility model provides a hexagon spiral silicon drift detector for solve the problem that the electrode shape structure among the prior art is complicated, the array clearance is arranged is big.

In order to realize the purpose, the utility model discloses a technical scheme:

a hexagonal spiral silicon drift detector comprises a base body with the front face and the back face being in the same regular hexagon and aligned in parallel, wherein the center of the front face of the base body is an anode for collecting electrons, a spiral ring cathode which spirals outwards and extends along a hexagonal track is wound outside the anode, the tolerance of a gap between adjacent spiral ring stages of the spiral ring cathode in the radial direction is =10 mu m, the number of the ring stages of the spiral ring cathode is 21, and the spiral ring cathode is positioned in a boundary ring; and the reverse side of the substrate is provided with a cathode.

Further, the width of the spiral ring cathode increases uniformly along an outwardly extending spiral trajectory.

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, the hexagonal cathode ring is concentric with the anode, and the ring level width of the hexagonal cathode ring is 10 μm.

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 whole surface of the reverse side of the substrate is a reverse cathode, and the surface of the reverse cathode is covered with an aluminum electrode contact layer.

Furthermore, the surfaces of the anode and the hexagonal cathode rings are covered with aluminum electrode contact layers, and the area between the spiral ring cathode rings on the front surface of the matrix is covered with S _i O ₂ And (3) a membrane.

Further, the size of the matrix is 3000 μm × 3000 μm × 300 μm, the radius of the circumscribed circle of the anode is 60 μm, the radius of the circumscribed circle of the hexagonal cathode ring is 70 μm and the ring width is 20 μm, the distance from the starting point of the spiral ring cathode to the center of the front surface of the matrix is 100 μm, the radius of the circumscribed circle of the back surface cathode is 3000 μm, and the inner diameter of the boundary ring is 2940 μm and the ring width is 60 μm; the doping concentration of the matrix is 4 x 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.

Further, the thickness d =300 μm of the matrix, and the innermost ring radius r of the spiral ring cathode ₁ =100um, radius of outermost ring R =2500um, resistivity ρ _s =2000 (ψ · cm), and dielectric constant ∈ =1.

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 cathode is made on the whole surface of the back side, so that the process manufacturing difficulty is favorably reduced. Meanwhile, compared with a quadrilateral silicon drift detector, the hexagonal silicon drift detector has the advantages that the distribution of the spiral ring cathode is closer to a circle, the distance from the anode to the cathode is more uniform, and the symmetry is better; compared with a circular base body, the array unit can be closely arranged when being used as an array unit, no gap exists between the units, and no dead zone can be realized in detection.

Drawings

Fig. 1 is a schematic front-up perspective view of a detector according to an embodiment of the present invention.

Fig. 2 is a schematic perspective view of a detector according to an embodiment of the present invention with its reverse side facing upward.

Fig. 3 is a partial enlarged view of a detector in a front plan view according to an embodiment of the present invention.

Fig. 4 is an X-axis cross-sectional view of a detector in an embodiment of the invention.

Fig. 5 is an electric field simulation diagram of the detector under the voltages of-35V at the outermost ring of the positive spiral ring cathode and-33V at the negative cathode in one embodiment of the present invention.

Fig. 6 is a diagram showing potential simulation of the detector under voltages of-35V at the outermost ring of the front spiral ring cathode and-33V at the back cathode according to an embodiment of the present invention.

Fig. 7 is a simulation diagram of electron concentration of the detector under voltages of-35V at the outermost ring of the front spiral ring cathode and-33V at the back cathode according to an embodiment of the present invention.

In the figure: 1. an anode; 2. a hexagonal cathode ring; 3. s. the _i O ₂ A film; 4. a helical 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 cathode on the back side.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure.

A hexagonal spiral silicon drift detector, as shown in fig. 1 to 4, which includes a base body with front and back surfaces being 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, the anode 1 is surrounded with a spiral ring cathode 4 which spirals outwards and extends along a hexagonal track, the spiral ring cathode 4 is located in a boundary ring 6 at the edge of the base body, and the end 7 of the spiral ring cathode 4 located at the outermost ring level is spaced from the boundary ring 6 by a certain distance; the reverse side of the substrate is a reverse cathode.

The spiral structure adopted by the cathode 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 1 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 back side is made into the 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 an electronic drift channel is flatter; 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.

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 are uniformly increased along the outward extending spiral track, 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 a plane, and an optimal electron drift channel can be obtained.

The inter-ring gap of the spiral ring is the distance between the outer boundary of a certain ring of the spiral ring cathode 4 and the inner boundary of an adjacent ring at the outer side, and then the inter-ring pitch P (r) is the sum of the width w (r) of the current ring and the inter-ring gap of the spiral ring. 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, so that better surface electric field distribution can be achieved, and a drift channel can be straightened. 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 driven into the detector from the incident surface, 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 concentric with the anode 1 and similar to the anode 1, 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 role in buffering, and by pressurizing the hexagonal cathode ring, a voltage between the anode 1 and the first ring of the spiral ring cathode 4 is automatically adjusted, so that the electric field distribution is more uniform, and a better electron 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 electrode contact on the front side of the detector is defined by the anode 1, the hexagonal 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, the electrode contact is defined on the whole surface of the back side, and the part with the electrode contact is covered by an aluminum film with the thickness of 1 μm. 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 N type light doping with the doping depth of 1 mu m, wherein 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, and 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 ρ _s And other given quantities: tolerance g of inter-ring gap, thickness d of base body, innermost ring radius r ₁ Radius R of the outermost ring, dielectric constant epsilon and current I;

s2, calculating the rotating angle of any point on the spiral ring cathode relative to the starting point: phi is a unit of _I ＝4ρ _s Alpha I, alpha is constant coefficient 6;

s3, calculating an intermediate process formula as follows:

wherein x = σ ² r ^2ε -1，x ₁ ＝σ ² r ₁ ^2ε -1，n＝0,1,2,3…，

r is angle of following spiral ring

The radius that continuously extends outwards is provided,

for successive increasing radians in the helical rotation, r ₁ Is the radius of the innermost ring;

s4, calculating an intermediate process formula according to the formulas in the S2 and the S3

The derivation is carried out by surface potential:

solving sigma to obtain the formula;

s5, calculating the angle of the spiral following ring according to the formula in the S4

Radius extending continuously outward

r increases with increasing helical loop extension;

s6, obtaining the width of the spiral ring cathode according to the formula in the S4

And an inter-ring gap p (r) = ω (r) + g of two adjacent rings, as shown in fig. 3;

s7, calculating depletion voltage

Wherein N is _eff Is silicon substrate N-type lightly dopedHetero concentration, q being the amount of charge per electron q =1.6 × 10 ^-19 C，ε ₀ Is a dielectric constant ε of vacuum 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 actual conditions. As said voltage V _out =110V, voltage V _E1 =10V, tolerance of gap between rings g =10 μm, thickness of base d =300 μm, radius r ₁ =100 μm, radius R of the outermost ring =2500 μm, dielectric constant ∈ =1, current I =0.05mA.

The surface electric field can be effectively adjusted according to actual conditions in the design to realize the optimal carrier drift electric field, so that the function of the detector is optimized. 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 to 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.

The utility model discloses a hexagon spiral silicon drift detector possesses automatic partial pressure function, compares in concentric ring detector because of not possessing this kind of automatic partial pressure function, changes according to certain voltage gradient in order to guarantee between ring and the ring when needing the pressurization, and every concentric ring that needs give concentric ring detector is different in addition to the bias voltage, and it is simpler to operate when obviously the detector of present case is used. 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 above embodiments are only applicable to help understand 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 contents of the present specification should not be construed as limitations of the present invention.

Claims (8)

1. A hexagonal spiral silicon drift detector, characterized by: the cathode comprises a base body with the front face and the back face being in the same regular hexagon and aligned in parallel, wherein the center of the front face of the base body is an anode for collecting electrons, a spiral ring cathode which spirals outwards and extends along a hexagonal track is wound outside the anode, the tolerance of the gap between adjacent spiral ring stages of the spiral ring cathode in the radial direction is =10 mu m, the number of the ring stages of the spiral ring cathode is 21, and the spiral ring cathode is positioned in a boundary ring; and the reverse side of the substrate is provided with a cathode.

2. The hexagonal spiral silicon drift detector of claim 1, wherein: the width of the spiral ring cathode increases uniformly along an outwardly extending spiral track.

3. The hexagonal-helical silicon drift detector of claim 2, wherein: and the hexagonal cathode ring is positioned between the anode and the spiral ring cathode, the anode is in a regular hexagon shape, the hexagonal cathode ring is concentric with the anode, and the ring level width of the hexagonal cathode ring is 10 mu m.

4. The hexagonal spiral silicon drift detector of 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. The hexagonal-spiral silicon drift detector of any one of claims 1 to 4, wherein: the whole surface of the reverse side of the substrate is a reverse side cathode, and the surface of the reverse side cathode is covered with an aluminum electrode contact layer.

6. The hexagonal-helical silicon drift detector of claim 5, wherein: the surfaces of the anode and the hexagonal cathode rings are covered with aluminum electrode contact layers, and the area between the spiral ring cathode rings on the front surface of the matrix is covered with S _i O ₂ And (3) a membrane.

7. The hexagonal spiral silicon drift detector of claim 6, wherein: 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 radius of the circumscribed circle of the back surface cathode is 3000 microns, and 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 x 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, and 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.

8. The hexagonal-helical silicon drift detector of claim 7, wherein: the thickness d =300 μm of the matrix, and the innermost ring radius r of the spiral ring cathode ₁ =100um, radius of outermost ring R =2500um, resistivity ρ _s =2000 (ψ · cm), mediumElectrical constant ∈ =1.

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