A block silicon drift detector with an elliptical voltage dividing resistor

Abstract

The utility model discloses a kind of block type silicon drift detectors with oval voltage division resistor, it is related to silicon detector technical field, including matrix, the center of matrix top surface is provided with circular anode, several mutually spaced concentric circular cathodes are provided around anode, floating electrode is provided between two adjacent cathodes, resistance ring is provided on floating electrode, resistance chain is provided in resistance ring, and resistance chain is oval arc first position connection, and the resistance of each resistance chain is equal. The utility model adopts oval voltage division resistor chain, electric field distribution is more uniform, can reduce readout capacitor and full depletion voltage, while solve the disadvantage that the leakage current of helical silicon drift detector is too large, effectively suppress edge field distortion, and oval voltage division resistor chain has longer distance between cathode ring, can increase resistance chain length and width, so that the design has stronger universality in actual production manufacturing process.

Description

Technical Field

[0001] This utility model relates to the field of silicon detector technology, and in particular to a block-type silicon drift detector with an elliptical voltage divider resistor. Background Technology

[0002] The silicon drift detector (SDD) is a high-resolution X-ray and charged particle detector. Due to its unique structure and performance advantages, as well as mature fabrication technology, it is widely used in materials analysis, synchrotron radiation, and astronomical observation. Its core principle is to use a transverse electric field to cause electron-hole pairs generated by ionization to drift directionally to a small-area collecting anode at the center under the influence of an applied electric field, thereby achieving high energy resolution and high count rate.

[0003] The development of silicon drift detectors can be traced back to the 1980s, first proposed by Emilio Gatti and Pavel Rehak of the Italian Institute of Nuclear Physics. This innovative design revolutionized the charge collection method of traditional semiconductor detectors by introducing a lateral drift electric field. During its technological development, traditional concentric ring silicon drift detectors faced several key challenges: the nonlinear distribution of the potential gradient between the ring electrodes led to an inhomogeneous drift electric field and unstable charge collection efficiency; the peripheral circuitry was complex (requiring multiple high-voltage biases), making the design of signal readout electronics difficult; electric field distortion at the device edges caused significant leakage current; high-precision concentric ring electrode fabrication was required (alignment error must be <1μm); surface passivation processes were highly complex; and system integration was challenging.

[0004] Concentric ring silicon drift detectors with resistor chains offer significant advantages over traditional detectors in terms of collection efficiency, resolution, integration, and automation. Firstly, their integrated resistor network enables precise control of the electric field distribution, resulting in better uniformity of the drift electric field and significantly improving charge collection efficiency and energy resolution. Secondly, the resistor chain structure effectively suppresses edge electric field distortion. Furthermore, by optimizing resistor temperature drift characteristics and employing a three-dimensional integration process, this detector maintains stable performance over a wide temperature range while supporting high count rates >1MHz. This overcomes the efficiency loss problem of three-dimensional detectors at low energy levels. Regarding process complexity, the resistor chain SDD uses a planar manufacturing process, which is easier to mass-produce compared to the three-dimensional structure of three-dimensional detectors. It also avoids the stringent high-precision photolithography requirements of spiral ring structures and eliminates the need for complex external high-voltage modules, exhibiting stronger reliability in harsh environments such as synchrotron radiation and space exploration. However, the design of traditional resistor chain voltage divider SDDs is complex, and the resistor chain process is difficult to implement. Therefore, designing a simple and easily implemented inter-ring resistor chain has become a key focus for resistor chain voltage divider silicon drift detectors.

[0005] Therefore, there is an urgent need for a simple and effective resistive chain silicon drift detector to make the electric field distribution more uniform, improve charge collection performance, and better adapt to current manufacturing processes. Utility Model Content

[0006] The present invention aims to provide a block-type silicon drift detector with elliptical voltage divider resistors to solve the problem that the design of traditional SDDs with resistor chains is relatively complex and the resistor chain process is difficult to implement.

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] A block-type silicon drift detector with elliptical voltage divider resistors includes a substrate, an anode, a cathode, and resistor rings. The substrate is circular, with a circular anode at the center of its top surface. Several concentric annular cathodes are arranged around the anode, and a floating electrode is positioned between adjacent cathodes. A resistor ring is mounted on the floating electrode, and a resistor chain connecting two adjacent cathode rings is disposed within each resistor ring. The resistor chain consists of elliptical arcs connected end-to-end, and each resistor chain has the same resistance. The entire bottom of the substrate is configured as cathodes. An aluminum layer is attached to the end of the outermost resistor chain and the bottom of the substrate for applying pressure. An aluminum layer is attached to the surfaces of the anode and cathodes for conductivity. The portion of the substrate outside the resistor chains is filled with a silicon dioxide insulating layer.

[0009] Furthermore, the substrate has a doping concentration of 1×10⁻⁶. 12 / cm 3 Lightly doped with N-type.

[0010] Furthermore, the anode has a doping concentration of 1×10⁻⁶. 19 / cm 3 It is heavily N-type doped with a doping depth of 1 μm.

[0011] Furthermore, both the cathode ring and the floating electrode are 1×10⁻⁶. 19 / cm 3 It is heavily p-type doped with a doping depth of 1 μm.

[0012] Furthermore, the parameters of each link of the resistor chain are as follows:

[0013] Defined algebra: the width of the resistor chain is w, the width of the resistor ring is G, the distance of the resistor chain from the two adjacent cathodes is k, the ratio of the width of the innermost resistor chain to the width of the outermost resistor chain is ε, and the maximum radius of the detector is r. N ;

[0014] The minor axis of the elliptical arc of the resistor chain is:

[0015]

[0016] The major axis of the elliptical arc of the resistor chain is:

[0017]

[0018] Where N represents the ordinal number of the resistance ring, m N The number of arcs in the resistor chain is represented by θ, which represents the central angle.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] 1. This utility model uses an elliptical voltage divider resistor chain, which has a more uniform electric field distribution and further reduces the readout capacitance and total depletion voltage.

[0021] 2. This utility model solves the problem of excessive leakage current in spiral silicon drift detectors.

[0022] 3. The elliptical voltage divider resistor chain has a longer distance between the cathode rings, which increases both the length and width of the resistor chain, making this design more universal in actual production and manufacturing processes.

[0023] 4. The elliptical resistor chain structure effectively suppresses edge electric field distortion. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of an elliptical voltage divider block silicon drift detector.

[0025] Figure 2 This is a top view of an elliptical voltage divider block silicon drift detector;

[0026] Figure 3 yes Figure 2 A magnified view of a medium-elliptical resistor chain;

[0027] Figure 4 This is a cross-sectional view of an elliptical voltage divider block silicon drift detector from the collecting anode to the boundary;

[0028] Figure 5 It shows the inner ring structure of the resistor chain, and labels the data represented by the letters in the formula;

[0029] Figure 6 It is a simulation diagram of the electric field of the detector under the voltage of 50V on the outermost ring of the front and 70V on the back.

[0030] Figure 7 It is a simulation diagram of the potential of the detector under the voltage of 50V on the outermost ring of the front and 70V on the back.

[0031] Figure 8It is a simulation diagram of the electron concentration of the detector under the voltage of 50V on the outermost ring of the front side and 70V on the back side.

[0032] The reference numerals in the accompanying drawings include:

[0033] 1. Anode; 2. Aluminum layer; 3. Resistance ring; 4. Resistance chain; 5. Cathode; 6. Floating electrode; 7. Substrate; 8. Bottom surface. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this utility model are used to explain the present utility model, but are not intended to limit the present utility model.

[0035] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures closely related to the solution according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0036] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, or component, but does not exclude the presence or addition of one or more other features, elements, or components.

[0037] In the following description, embodiments of the present invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts.

[0038] Example 1

[0039] refer to Figures 1 to 5 A block-type silicon drift detector with elliptical voltage divider resistors includes a substrate 7, an anode 1, a cathode 5, and a resistor ring 3. The substrate 7 is a cylinder with a diameter of 5 mm and a height of 300 μm. The cylindrical substrate 7 allows for a more uniform potential and electric field distribution inside the detector. The substrate 7 is lightly doped with N-type doping at a doping concentration of 1 × 10¹² / cm³.

[0040] A circular anode 1 is set at the center of the top surface of the substrate 7. The anode 1 is an N-type heavily doped anode with a doping concentration of 1×10¹⁹ / cm³ and a doping depth of 1μm.

[0041] A number of concentric annular cathodes 5 are arranged around the anode 1, and a floating electrode 6 is arranged between two adjacent cathodes 5. Both the cathode rings 5 ​​and the floating electrode 6 are P-type heavily doped with 1×10¹⁹ / cm³, and the doping depth is 1μm.

[0042] A resistor ring 3 is provided on the floating electrode 6. Within the resistor ring 3, a resistor chain 4 connects two adjacent cathode rings 5. The resistor chains 4 are connected end-to-end in an elliptical arc, and each resistor chain 4 has the same resistance value to achieve self-dividing voltage. The bottom of the substrate 7 is entirely configured as cathodes 5. An aluminum layer 2 is attached to the end of the outermost resistor chain 4 and the bottom of the substrate 7 for pressurization. An aluminum layer 2 is attached to the surfaces of the anode 1 and cathode 5 for conductivity. The top portion of the substrate 7, excluding the resistor chains 4, is filled with a silicon dioxide insulating layer.

[0043] The detector is pressurized only at the end of the outermost resistor chain 4 and at the cathode 5 on the bottom surface 8 of the detector to control and obtain a suitable drift channel.

[0044] The derivation of the four parameters of the resistor chain for a block-type silicon drift detector with elliptical voltage divider resistors is as follows:

[0045] Taking a 1 / 6 circle as an example, the derivation formula for each resistor ring 3 is as follows, with the letters in the formula for reference. Figure 6 The width wmin of the innermost resistor chain 4 is specified to be 5μm, the width G of the resistor ring 3 is 60μm, the distance k of the resistor chain 4 from the two adjacent cathode rings 5 ​​is 10μm, the ratio ε of the width of the innermost resistor chain 4 to the width of the outermost resistor chain 4 is 0.2, and the maximum radius rN of the detector is 2500μm.

[0046] This allows us to determine the minor axis of the single arc of the first elliptical resistor chain 4 and the width of the outermost resistor chain 4:

[0047]

[0048] The minor and major axes of a single arc in the outermost elliptical resistor chain:

[0049]

[0050] Since the resistance value is the same in each loop of the resistor chain, we can obtain:

[0051]

[0052] Substituting the expression for the ellipse circumference l1, we get:

[0053]

[0054] Therefore, the short axis a1 of the innermost resistance chain can be obtained:

[0055]

[0056] Number of arcs in the first loop of the resistor chain:

[0057]

[0058] At this point, the innermost resistance chain is completely obtained. Next, an iterative method is used to calculate the data for the subsequent resistance chains, with the number of arcs *m* decreasing by 0.5 for each chain. The first iteration calculation for the second resistance chain:

[0059]

[0060]

[0061] When the iteration reaches an error limit of less than 0.1%, the accurate value is considered to have been found. The iteration method for subsequent ring numbers is the same as the above process, and will not be elaborated further here.

[0062] Experimental Example 1

[0063] This invention presents a three-dimensional model of a novel detector, using a 10-turn cathode ring and a 10-turn resistor chain as an example. The detector was simulated using semiconductor device simulation software (Sentaurus TCAD), and the experimental results are referenced. Figures 6 to 8 .

[0064] Figures 6 to 8 These are all results with the outermost ring having its depletion voltage doubled, and you can clearly see... Figure 6 It has excellent drift channels, indicating that the charge can be efficiently collected to the central anode. Figure 7 The potential distribution diagram clearly shows a high potential region at the center of the detector, proving that the central anode has a high potential, which can achieve better collection results. Figure 8 The diagram shows the electron concentration. It is clear that the electron concentration is very high at the central anode, and a clear high electron concentration channel appears inside the detector, which further proves that the detector has a very good collection effect.

[0065] Simulation results show that the drift channel of the block-type silicon drift detector with elliptical voltage divider resistors is more obvious and the electric field distribution is more uniform.

[0066] The beneficial effects of this invention are:

[0067] Block-type silicon drift detectors with elliptical voltage divider resistors eliminate the drawback of traditional concentric ring silicon drift detectors that require sequential voltage application.

[0068] The voltage divider of the elliptical resistor chain makes the drift electric field more uniform and the collection efficiency higher.

[0069] The elliptical resistor chain structure effectively suppresses edge electric field distortion.

[0070] The elliptical voltage divider resistors have a longer distance between the cathode rings, which increases both the length and width of the resistor chain, making this design more universally applicable in actual manufacturing processes.

[0071] This invention, through reasonable experimental calculations, yielded an innermost resistive chain width of five micrometers, which better suits laboratory fabrication and reduces manufacturing difficulty. The detector thickness of three hundred micrometers is consistent with current mainstream wafer thickness, further reducing fabrication complexity. Simultaneously, a clear drift channel was obtained, and the high-potential region of the central collecting anode can reach 0.5V, exhibiting strong collection performance. The electron concentration diagram is shown in a 1*10⁻⁶ area. 12 The channels obtained per cubic centimeter are more obvious at this concentration, and the electron concentration distribution is clearer.

[0072] In this invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0073] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. For those skilled in the art, various modifications and variations can be made to the embodiments of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

[0074] The scope of protection claimed in this application shall be determined by the content of its claims, and the specific embodiments described in the specification may be used to interpret the content of the claims.

Claims

1. A block-type silicon drift detector with elliptical voltage divider resistors, characterized in that, The device includes a substrate (7), an anode (1), a cathode (5), and a resistor ring (3). The substrate (7) is circular, and a circular anode (1) is disposed at the center of the top surface of the substrate (7). Several concentric annular cathodes (5) are disposed around the anode (1). A floating electrode (6) is disposed between two adjacent cathodes (5). A resistor ring (3) is disposed on the floating electrode (6). A resistor chain (4) connecting two adjacent cathode (5) rings is disposed inside the resistor ring (3). The resistor chain (4) is connected end to end in an arc, and the arc is an elliptical arc. The resistance value of each resistor chain (4) is equal. The bottom of the substrate (7) is entirely set as a cathode (5). The end of the outermost resistor chain (4) and the bottom of the substrate (7) are both attached with an aluminum layer (2) for pressurization. The surfaces of the anode (1) and cathode (5) are attached with an aluminum layer (2) for conductivity. The part of the top of the substrate (7) other than the resistor chain (4) is filled with a silicon dioxide insulating layer.

2. A block-type silicon drift detector with elliptical voltage divider resistors according to claim 1, characterized in that, The parameters of each resistor chain (4) are as follows: The following algebraic rules apply: the width of the resistor chain (4) is w, the width of the resistor ring (3) is G, the distance of the resistor chain (4) from the two adjacent cathodes (5) is k, the ratio of the width of the innermost resistor chain (4) to the width of the outermost resistor chain (4) is ε, and the maximum radius of the detector is rN. The minor axis of the elliptical arc of the resistor chain (4) is: The major axis of the elliptical arc of the resistor chain (4) is: Where N represents the ordinal number of the resistor ring (3), mN represents the number of arcs of the resistor chain (4), and θ represents the central angle.

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