Hit-resistive chain silicon drift detector

Abstract

The application discloses a through-resistance chain type silicon drift detector, which comprises a base, a circular anode, a floating cathode concentric ring and a through-resistance chain formed by doping at the center of the upper surface of the base; the through-resistance chain surrounds the circular anode, and the floating cathode concentric ring surrounds the through-resistance chain; the lower surface of the base is a bottom cathode, and an aluminum electrode contact layer of the bottom cathode covers the bottom cathode; one end of the through-resistance chain is covered with an aluminum electrode contact layer at the rear end of the through-resistance chain, the other end of the through-resistance chain is covered with an aluminum electrode contact layer at the front end of the through-resistance chain, and the circular anode is covered with an aluminum electrode contact layer; the part of the detector which is not covered with the aluminum electrode contact layer is covered with a silicon dioxide insulation layer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon detectors, and particularly relates to a method for a punch-through resistance chain type silicon drift detector. BACKGROUND

[0002] Silicon drift detectors (SDD) are very suitable for use in high-rate and high-energy resolution environments. Due to their small readout anode, even large pixel sizes of a few millimeters can keep the overall capacitance at the level of a few hundred fF, thus enabling low serial noise, which in turn allows for short energy filter shaping times and facilitates the increase of the measurement rate.

[0003] Generally, SDDs are used for x-ray measurements. For example, SDDs play a key role in photo-k-meson atomic x-ray spectroscopy, exploiting their excellent ability to extract the shift (epsilon) and width (Gamma) of atomic levels caused by KN strong interactions. These observable values are fundamental quantities for understanding the non-perturbative quantum chromodynamics of the strange region, with implications from particle and nuclear physics to astrophysics. In addition, in the framework of the Tritium Research with Sterile-Active Neutrino Mixing (TRISTAN) project, the first prototype detector based on silicon drift detector technology has been developed and tested. Based on the different energy deposition distributions of heavy charged particles and photons, the detector will be used for high-precision electron energy spectroscopy. In contrast to the application of x-rays, the energy loss in the insensitive region of the entrance window and the effects of backscattering on the surface of the detector play a major role in the detection of electrons.

[0004] Traditional SDDs have two electrode structures, concentric ring and spiral, the concentric ring SDD is simple to design and manufacture, and has excellent electrical properties, but cannot independently divide the voltage, and needs to be biased with appropriate voltage for each ring. In order to simultaneously achieve independent voltage division and excellent electrical properties of the concentric ring SDD, there are various structure designs such as spiral SDD, which can independently divide the voltage, but is more complex to design and manufacture, and due to its traditional voltage application method, the potential distribution is not as uniform as that of the concentric ring SDD.

[0005] Therefore, there is an urgent need for a simple and effective silicon drift detector to achieve independent voltage division of each concentric ring in the detector structure and simplify the manufacturing process. SUMMARY

[0006] The application aims to provide a punch-through resistance chain type silicon drift detector to solve the problems of complicated voltage application and voltage division of traditional silicon drift detectors, and the inability of traditional concentric ring silicon detectors to effectively separate the bias cathode and ohmic voltage division resistance chain, and the manufacturing method is simpler.

[0007] The technical scheme adopted by the present application is that the through-resistance chain type silicon drift detector comprises a base, a center circular anode, a floating cathode concentric ring and a through-resistance chain are formed by doping on the upper surface center of the base; the through-resistance chain surrounds the circular anode, and the floating cathode concentric ring surrounds the through-resistance chain; the lower surface of the base is a bottom cathode, and the bottom cathode is covered by a bottom cathode aluminum electrode contact layer below; one end of the through-resistance chain is covered by a through-resistance chain rear end aluminum electrode contact layer, and the other end is covered by a through-resistance chain front end aluminum electrode contact layer, and the circular anode is covered by an anode aluminum electrode contact layer; the part of the detector which is not covered by the aluminum electrode contact layer is covered by a silicon dioxide insulation layer.

[0008] Further, the base is a 200-500 micron thick cylindrical semiconductor, and the base is N type lightly doped.

[0009] Further, the doping concentration of the base is 1x10 11 / cm 3 -1x10 13 / cm 3 .

[0010] Further, the circular anode is N type heavily doped, and the doping depth is 1-5 microns.

[0011] Further, the doping concentration of the circular anode is 1x10 18 / cm 3 -1x10 23 / cm 3 .

[0012] Further, the through-resistance chain and the floating cathode concentric ring are both P type heavily doped, and the doping depth is 1-5 microns.

[0013] Further, the doping concentration of the through-resistance chain and the floating cathode concentric ring is both 1x10 18 / cm 3 -1x10 23 / cm 3 .

[0014] Further, the sum of the ring width w and the ring distance g of the floating cathode concentric ring is a constant value G, and G is 80-120 microns.

[0015] Further, the distance between the innermost floating cathode concentric ring and the circular anode is 100-200 microns.

[0016] The beneficial effects of the present application are:

[0017] 1. The current generated by the silicon drift detector of the present application after bias voltage is applied only covers a small area of the SDD, effectively separating the bias cathode and the ohmic voltage dividing resistance chain.

[0018] 2, The silicon drift detector of the present application not only has excellent electrical performance, but also can realize independent voltage division of each concentric ring in the detector structure.

[0019] 3, Compared with the structure of the existing silicon drift detector, including concentric ring structure and spiral ring structure, the design and manufacture of the silicon drift detector of the present application is simpler.

[0020] 4, The silicon drift detector of the present application is designed as a circle, and there will be more uniform electric potential and electric field distribution in the detector.

[0021] 5, The central readout anode of the silicon drift detector of the present application is very small, so that the detector has very small capacitance and realizes low noise. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1 is a schematic diagram of the top layer doping of the detector substrate.

[0024] Figure 2 is a schematic diagram of the aluminum electrode contact layer and the silicon dioxide protective layer on the upper surface of the detector.

[0025] Figure 3 is a sectional view of the punch-through resistance chain.

[0026] Figure 4 is a sectional view of the floating cathode concentric ring.

[0027] Figure 5 is a schematic diagram of the three-dimensional modeling of the detector.

[0028] Figure 6 is a two-dimensional sectional view of the top layer doping of the 5-turn cathode concentric ring detector substrate.

[0029] Figure 7 is a two-dimensional simulation diagram of the potential of the Z-axis section of the detector.

[0030] Figure 8 is a comparison curve diagram of the potential at different positions on the surface of the detector.

[0031] Figure 9 is a two-dimensional diagram of the electric field intensity of the Z-axis section of the detector.

[0032] Figure 10 is a two-dimensional diagram of the electron concentration at two different sections under different bias voltages.

[0033] Figure 11 is the surface potential curve of two different sections under different bias.

[0034] Figure 12 is a traditional spiral ring silicon drift detector.

[0035] Figure 13 is a traditional concentric ring silicon drift detector.

[0036] In the figure, 1. the breakdown resistance chain, 2. the floating cathode concentric ring, 3. the circular anode, 4. the substrate, 5. the breakdown resistance chain rear end aluminum electrode contact layer, 6. the breakdown resistance chain front end aluminum electrode contact layer, 7. the anode aluminum electrode contact layer, 8. the silicon dioxide insulation layer, 9. the bottom cathode, 10. the bottom cathode aluminum electrode contact layer. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0038] Referring to Figures 1-4 , the breakdown resistance chain type silicon drift detector comprises a substrate 4, a circular anode 3 formed by doping on the top layer of the substrate 4, a floating cathode concentric ring 2 and a breakdown resistance chain 1, the circular anode 3 is located at the center of the top layer of the substrate 4, a circle of the breakdown resistance chain 1 is around the circular anode 3, and multiple circles of the floating cathode concentric ring 2 are around the breakdown resistance chain 1; the bottom layer of the semiconductor substrate 4 is a bottom cathode 9;

[0039] The breakdown resistance chain rear end aluminum electrode contact layer 5 is arranged at the rear end above the breakdown resistance chain 1, and a voltage V out The breakdown resistance chain front end aluminum electrode contact layer 6 is arranged at the front end above the breakdown resistance chain 1, and a voltage V1 is applied. anode The anode aluminum electrode contact layer 7 is arranged above the circular anode 3, and a voltage V b is applied.

[0040] The substrate 4 is a 200-500 micron thick cylindrical semiconductor, the substrate 4 is N-type lightly doped, and the doping concentration is 1×10 11 / cm 3 -1×10 13 / cm 3between 1*10 18 / cm 3 and 1*10 23 / cm 3 ; the punch-through resistance chain 1 and the floating cathode concentric ring 2 have the same doping, and the doping concentration is 1*10 18 / cm 3 and 1*10 23 / cm 3 ; the heavy doping concentration is obtained by dividing the ion implantation concentration by the implantation depth, and if the doping concentration is too low, the silicon crystal does not have good performance like a conductor, and if the doping concentration is too high, the silicon crystal is not good for recovery and needs to be cooled down and other cumbersome operations, and a larger doping concentration makes it difficult to remove the photoresist, and the process is more difficult.

[0041] The sum of the ring width w and the ring spacing g of the floating cathode concentric ring 2 is set as a constant value G, G is 80-120 microns, for example, G is 100 microns, the ring width w is 80 microns, and the ring spacing g is 20 microns. At the same time, a suitable distance of 100-200 microns is designed between the innermost floating cathode concentric ring 2 and the circular anode 3 to ensure that the probe is easy to press after being manufactured.

[0042] The probe is pressurized only at the bottom cathode 9 and the front end aluminum electrode contact layer 6 of the punch-through resistance chain and the rear end aluminum electrode contact layer 5 of the punch-through resistance chain, and a suitable drift channel is controlled.

[0043] Figure 5 A three-dimensional model of the probe is obtained by taking five floating cathode concentric rings 2 as an example, and then the electrical properties of the probe, including the electrostatic potential, the electric field and the full depletion voltage, are simulated.

[0044] Figure 6 The upper surface of the probe is doped, the center is the circular anode 3, and the outer circle of the circular anode 3 is the punch-through resistance chain 1 and the floating cathode concentric ring 2.

[0045] Figure 7 The potential two-dimensional simulation diagram obtained by making a Z-axis section of the surface of the probe, the silicon probe designed in the application is circular, and it can be seen that the potential distribution inside the probe is uniform, and the probe can provide good performance in the working state. The potential electric field gradient changes slightly at the punch-through resistance chain 1 compared with the drift ring. The Figure 8 .

[0046] Figure 8For the potential contrast curve diagram of different positions on the surface of the detector, c is the position of the breakdown resistance chain 1, and a and b are the positions of the different floating cathode concentric rings 2, it can be seen that the total potential gradient at the breakdown resistance chain 1 is greater than that at the floating cathode concentric ring 2 and is smoother, the potential at the floating cathode concentric ring 2 changes in an equal gradient, and the potential at the breakdown resistance chain 1 changes uniformly, and does not affect the performance of the detector.

[0047] Figure 9 For the electric field intensity two-dimensional diagram of the Z-axis section of the surface of the detector, it can be seen that the PN junction is formed at the contact position of the floating cathode concentric ring 2 and the substrate 4, a high electric field region is generated, and the other regions are constant electric fields, which can provide stable power for the drift.

[0048] Figure 10 For the potential two-dimensional diagram of two different sections under each bias, a continuous and uniform potential distribution is formed in the detector, the potential gradient gradually forms with the increase of the bias voltage, and the potential gradient changes slightly at the breakdown resistance chain 1.

[0049] Figure 11 For the electron concentration two-dimensional diagram of two different sections under each bias, it can be seen that the detector is gradually depleted and an obvious electron drift track is formed with the increase of the bias voltage. From the upper and lower surfaces of the detector to the middle part, the electron concentration gradually increases, and the middle region has a higher electron concentration than other regions. This region is called an electron drift track. The electrons outside this region first drift to this region under the action of the electric field, and then drift to the anode under the action of the constant electric field in this region. An optimal electron drift track is formed between 60V and 70V, and the electron drift channel gradually deviates when the bias voltage is too large from 70V to 100V.

[0050] Figure 12 For the traditional spiral ring silicon drift detector, the cathode spiral ring provides a transverse drift electric field and also acts as a voltage dividing resistance chain, Figure 13 For the traditional concentric ring silicon drift detector, the concentric ring provides a transverse drift electric field, and a spiral resistance chain is wrapped around the concentric ring to divide the voltage. The interference current generated in the above resistance chain region covers a large area.

[0051] Compared with the existing spiral ring silicon drift detector and concentric ring silicon drift detector, the detector of the present application only needs to apply different voltages to the bottom cathode 9 and the aluminum electrode contact layer 6 at the front end of the breakdown resistance chain and the aluminum electrode contact layer 5 at the rear end of the breakdown resistance chain to form a change gradient. Not only does it have excellent electrical performance, but it can also realize self-voltage division. The existing concentric ring silicon drift detector needs to apply appropriate bias voltage to each ring. The voltage application method of the present application is simple, and the voltage application method is simplified.

[0052] The existing spiral ring silicon drift detector manufacturing process is complex, and the spiral ring electrode is both a voltage division resistor chain and a drift ring for providing a transverse electric field, and the interference current flowing through the spiral ring electrode covers almost the entire SDD surface, the present application effectively separates the bias cathode, i.e. the floating cathode concentric ring 2, and the ohmic breakdown resistance chain 1, the breakdown resistance chain 1 is independent of the floating cathode concentric ring 2, the interference current generated by the breakdown resistance chain 1 only covers a small area of the SDD, i.e. the area of the breakdown resistance chain 1, which is much smaller than the interference current generated by the existing spiral ring silicon drift detector, so that the performance of the silicon detector is more excellent.

[0053] The application point of the present application is:

[0054] 1. The present application effectively separates the bias cathode, i.e. the floating cathode concentric ring 2, and the ohmic breakdown resistance chain 1, and the breakdown resistance chain 1 is independent of the floating cathode concentric ring 2.

[0055] 2. The detector of the present application is only pressurized at the bottom cathode 9 and the front end aluminum electrode contact layer 6 of the breakdown resistance chain and the rear end aluminum electrode contact layer 5 of the breakdown resistance chain to form a variable gradient.

[0056] 3. The present application realizes self-voltage division of the silicon detector through the breakdown resistance chain 1.

[0057] 4. The present application simplifies the pressurization mode while maintaining the performance of the original silicon drift detector.

[0058] Each embodiment in the specification is described in a related manner, and the same and similar parts between each embodiment can be referred to each other, and each embodiment mainly explains the difference from other embodiments. Especially, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0059] The above only describes the preferred embodiments of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application is included in the protection scope of the present application.

Claims

1. A through- resistance chain silicon drift detector comprising a substrate (4), characterized in that, The center of the upper surface of the substrate (4) is formed into a circular anode (3), a floating cathode concentric ring (2) and a breakdown resistance chain (1) by doping; the breakdown resistance chain (1) surrounds the circular anode (3), and the floating cathode concentric ring (2) surrounds the breakdown resistance chain (1); the lower surface of the substrate (4) is a bottom cathode (9), and the bottom cathode (9) is covered by a bottom cathode aluminum electrode contact layer (10) below; one end of the breakdown resistance chain (1) is covered by a breakdown resistance chain rear end aluminum electrode contact layer (5) above, and the other end is covered by a breakdown resistance chain front end aluminum electrode contact layer (6); the circular anode (3) is covered by an anode aluminum electrode contact layer (7) above; the part of the probe that is not covered by the aluminum electrode contact layer is covered by a silicon dioxide insulation layer (8); the breakdown resistance chain (1) and the floating cathode concentric ring (2) are both P-type heavily doped, and the doping depth is 1-5 microns; the doping concentration of the breakdown resistance chain (1) and the floating cathode concentric ring (2) is both 1×10 18 / cm 3 -1×10 23 / cm 3 .

2. The through-connection resistive chain silicon drift detector according to claim 1, characterized in that The base (4) is a 200-500 micron thick cylindrical semiconductor, and the base (4) is N-type lightly doped.

3. The through-connection resistive chain silicon drift detector according to claim 2, characterized in that The doping concentration of the base (4) is 1 x 1018 / cm3 11 / cm3 3 1 x 1018 / cm3 13 / cm3 3 .

4. The through-connection resistive chain silicon drift detector according to claim 1, characterized in that The circular anode (3) is N-type heavily doped, and the doping depth is 1-5 microns.

5. The through-connection resistive chain silicon drift detector according to claim 4, characterized in that The doping concentration of the circular anode (3) is 1 x 10 18 / cm 3 -1 x 10 23 / cm 3 .

6. The through-connection resistive chain silicon drift detector according to claim 1, characterized in that The sum of the ring width w and the ring distance g of the floating cathode concentric ring (2) is a constant value G, and G is 80-120 microns.

7. The through-connection resistive chain silicon drift detector according to claim 1, characterized in that The distance between the innermost floating cathode concentric ring (2) and the circular anode (3) is 100-200 microns.

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