Annealing device of cadmium telluride series semiconductor crystal and cadmium telluride series semiconductor crystal

Abstract

The utility model provides a cadmium telluride series semiconductor crystal annealing device and a cadmium telluride series semiconductor crystal. The annealing device comprises: a crucible having a first zone and a second zone, the first zone being used for accommodating cadmium-containing chloride and / or indium-containing chloride, and the second zone being used for accommodating cadmium telluride series semiconductor crystals; the heating furnace comprises a furnace body and a heating device, the furnace body is used for containing the crucible, and the heating device is used for heating the crucible, so that the chloride containing cadmium and / or the chloride containing indium are / is molten into an annealing agent in a molten state; and the position adjusting device is connected with the heating furnace and is used for adjusting the position of the crucible accommodated in the furnace body, so that the cadmium telluride series semiconductor crystals are soaked in the annealing agent in the molten state, and the annealing agent in the molten state is used for annealing the cadmium telluride series semiconductor crystals. The annealing device can be used for preparing crystals with very good performance.

Description

Technical Field

[0001] The present application relates to a cadmium telluride series semiconductor crystal, and in particular, to an annealing device for a cadmium telluride series semiconductor crystal and a cadmium telluride series semiconductor crystal. Background Art

[0002] Cadmium telluride series semiconductor crystals have become the most ideal material for building room temperature nuclear radiation detectors due to their high average atomic number, large bandgap, high resistivity, and excellent carrier migration performance. 1-x Zn x Te, CZT) crystals are considered to be one of the most promising room temperature nuclear radiation semiconductor detector materials to date. However, this type of material has a high melting point, low thermal conductivity, strong ionic bond characteristics, and low stacking fault energy. It is easy to form secondary phases such as inclusion phases and precipitation phases, as well as structural defects such as dislocations and twins. In addition, the segregation of doping components such as Zn and vacancies caused by the high vapor pressure of Cd elements can also cause uneven crystal composition. These defects can capture or scatter carriers, affecting electrical properties such as carrier lifetime and mobility, thereby having a serious adverse effect on the device's X-ray and γ-ray detection performance.

[0003] Therefore, it is necessary to adopt necessary processing technology to improve the performance of the grown crystals, usually at high temperature (300-1240°C), introducing a high-concentration, low-saturated vapor pressure, non-corrosive annealing medium into a sealed container to reduce or even eliminate the various defects caused by growth.

[0004] At present, the mainstream method for annealing modification of cadmium telluride series semiconductor crystals is the gas phase method. The annealing atmosphere used includes inert gases (Ar, He, H2, D2, etc.), and the annealing agents include Cd metal source, Cd / Zn metal alloy, Te source, etc., among which Cd metal source is the most commonly used annealing agent.

[0005] CN102168313A provides a Cd 1-x Zn x The two-step vapor phase annealing method for Te crystals uses non-metallic Te and metal alloy Cd / Zn as annealing sources in sequence, achieving the effect of improving the resistivity of the crystal and the energy resolution of the detector, eliminating the inclusion phase and improving the carrier transport performance. However, its annealing time is as long as 2400h, which greatly reduces production efficiency and increases production energy consumption.

[0006] CN106192014A discloses a mobile cyclic annealing modification method for CdZnTe crystals, using metal Cd as an annealing agent, to solve the technical problem that the existing annealing method for CdZnTe crystals has poor effect in eliminating small inclusion phases below 10 μm. It does not mention changes in properties such as carrier-mobility lifetime product and resistivity.

[0007] CN114737256A discloses a Cd 1-x Zn x The method of annealing Te crystals in a Cd saturated vapor atmosphere improves the uniformity of the crystal by eliminating Cd vacancies. The annealing process is to make CZT more suitable as a substrate for growing HgCdTe materials, but it does not mention the use of CZT for radiation detection.

[0008] US8268663B2 discloses a method for treating Cd in a hydrogen or deuterium atmosphere and a Te vapor atmosphere. 1-x Zn x The method of annealing Te wafers increases the carrier mobility-lifetime product (μτ) by 2 to 5 times. However, the resistivity of the wafer decreases by 2 to 5 times after annealing, which is unfavorable for the application of CZT materials in radiation detection.

[0009] JP6004601B2 discloses a method for annealing II-VI semiconductor materials in an open annealing container under inert gas conditions to remove precipitate phase and inclusion phase impurities, which can effectively remove secondary phase defects, but does not mention the improvement of semiconductor material performance.

[0010] Another type of liquid phase annealing is less used. CN115161773A discloses a method for liquid phase annealing using an annealing agent containing the Cd element, wherein an aqueous solution of cadmium chloride (or cadmium nitrate, cadmium acetate, cadmium sulfate, cadmium sulfide) is used as the annealing agent, the annealing container is a stainless steel shell, a polytetrafluoroethylene lined container, the wafer is completely immersed in the solution, the container is sealed and placed in a muffle furnace for annealing, the annealing temperature is 80°C, the time is 20 to 30 hours, and the Cd 1-x Zn x The resistivity of Te wafer is 2.35×10 7 Ωcm increased to 1.11×10 9 Ωcm. The annealing agent contains water and the annealing temperature is low, resulting in poor annealing effect, and the resistivity still has room for improvement.

[0011] CN1186484C discloses a gas phase-liquid phase annealing method. A metal liquid with an atomic percentage of Cd:Zn = 100:1 is used as a liquid phase annealing medium and a gas phase annealing source. 1-x Zn x Te wafers are annealed. This makes the wafer composition more uniform and the resistivity increases from 5.74×10 8 Ωcm increased to 1.29×10 11However, under high temperature conditions, Cd metal is unstable and easy to sublimate, which leads to a significant increase in the vapor pressure in the crucible, making the operation more dangerous, and annealing takes a long time, which can easily damage the surface of the chip, consumes a lot of energy, and has low efficiency.

[0012] The existing annealing and modification methods for cadmium telluride series semiconductor crystals have problems such as long annealing time, easy damage to the crystal surface, insufficient improvement in crystal performance, inability to balance resistivity and carrier mobility-lifetime product, high energy consumption, and low efficiency, which results in the crystals' detector-level applications still being limited. Utility Model Content

[0013] In order to solve the above-mentioned existing technical problems, the first aspect of the present application provides an annealing device for a cadmium telluride series semiconductor crystal, comprising:

[0014] A crucible having a first region and a second region, wherein the first region is used to accommodate a chloride containing cadmium and / or a chloride containing indium, and the second region is used to accommodate a cadmium telluride series semiconductor crystal;

[0015] A heating furnace, comprising a furnace body for accommodating the crucible and a heating device, wherein the heating device is used to heat the crucible so that the cadmium-containing chloride and / or the indium-containing chloride is melted into a molten annealing agent;

[0016] A position adjustment device is connected to the heating furnace and is used to adjust the position of the crucible contained in the furnace body so as to immerse the cadmium telluride series semiconductor crystal in the molten annealing agent, thereby annealing the cadmium telluride series semiconductor crystal using the molten annealing agent.

[0017] In some embodiments of the present application, the position adjustment device includes:

[0018] A rotating shaft connected to the furnace body; and

[0019] A motor is connected to the rotating shaft. Under the action of the motor, the rotating shaft can rotate the furnace body, thereby driving the crucible to rotate, so as to immerse the cadmium telluride series semiconductor crystals in the molten annealing agent, thereby annealing the cadmium telluride series semiconductor crystals using the molten annealing agent.

[0020] In some embodiments of the present application, the position of the crucible includes a first position and a second position, wherein, in the first position, the second zone is located above the first zone, and the cadmium telluride series semiconductor crystal is separated from the molten annealing agent, and in the second position, the second zone is located below the first zone, and the cadmium telluride series semiconductor crystal is immersed in the molten annealing agent.

[0021] In some embodiments of the present application, a rotation angle of the crucible when rotating from the first position to the second position or from the second position to the first position is 120° to 180°.

[0022] In some embodiments of the present application, the annealing device further includes a fixture, wherein the fixture has a groove, and the groove is used to fix the cadmium telluride series semiconductor crystal;

[0023] The second area of ​​the crucible is provided with a slot for fixing the clamp.

[0024] In some embodiments of the present application, the clamp has one or more columns of groove groups, and each column of groove groups is provided with a plurality of the grooves.

[0025] In some embodiments of the present application, the crucible includes a crucible cap and a crucible body, the crucible cap includes a crucible mouth and a connecting portion for connecting with the crucible body; the connecting portion can extend into the crucible body and be connected with the inner wall of the crucible body by high-temperature sintering;

[0026] After the connecting portion and the crucible body are sintered, a first protrusion is formed at the end of the sintered portion, and a second protrusion is further provided on the inner wall of the crucible body. The first protrusion and the second protrusion constitute a slot for fixing the clamp.

[0027] In some embodiments of the present application, the furnace body includes a first temperature zone and a second temperature zone, and the heating device includes a first heating element arranged corresponding to the first temperature zone and a second heating element arranged corresponding to the second temperature zone; wherein the first heating element in the first temperature zone is used to heat the first zone, and the second heating element in the second temperature zone is used to heat the second zone.

[0028] In some embodiments of the present application, the first heating element and the second heating element can be controlled individually.

[0029] The second aspect of the present application provides a cadmium telluride series semiconductor crystal, which is produced by any of the above-mentioned annealing devices.

[0030] The present application uses cadmium-containing chloride and / or indium-containing chloride to prepare a molten annealing agent for annealing, which can achieve Cd vacancy compensation and In element doping of cadmium telluride series semiconductor crystals during annealing, thereby significantly improving the uniformity of crystal quality, resistivity and carrier transport characteristics, and can reduce annealing time, avoid damage to the crystal surface, improve efficiency and reduce energy consumption. The annealing device provided by the present application is simple, and when used in conjunction with the annealing method provided by the present application, a crystal with very good performance can be obtained.

[0031] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following is a detailed description of the implementation methods of the present application in conjunction with the accompanying drawings. Here, the accompanying drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application.

[0033] Figure 1 This is a flow chart of an annealing process for a cadmium telluride series semiconductor crystal provided in one embodiment of the present application;

[0034] Figure 2 is a flow chart of an annealing process for a cadmium telluride series semiconductor crystal provided in another embodiment of the present application;

[0035] Figure 3 is a cross-sectional view of an annealing device provided in one embodiment of the present application;

[0036] Figure 4 is a cross-sectional view of a crucible provided in one embodiment of the present application;

[0037] Figure 5 is a cross-sectional view of a crucible provided in another embodiment of the present application. DETAILED DESCRIPTION

[0038] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present application. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0039] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0040] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is lower in level than the second feature.

[0042] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0043] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0044] Figure 1 A method for annealing a cadmium telluride series semiconductor crystal provided in an embodiment of the present application is shown, comprising the following steps S11 and S12.

[0045] S11: preparing a molten annealing agent based on a chloride containing cadmium and / or a chloride containing indium.

[0046] Step S11 prepares cadmium-containing chloride and / or indium-containing chloride into annealing agent in a molten state. Relative to the metal Cd single substance in the prior art, the present application adopts cadmium-containing chloride and / or indium-containing chloride as annealing source, which is not easy to be oxidized, and can avoid the risk of oxidation of metal single substance, thereby preventing the adverse effect of oxygen on the performance of cadmium telluride semiconductor crystal. Moreover, under normal circumstances, chlorine element will not be doped into the crystal. Even if it is doped into the crystal for uncontrollable reasons, its trace doping is also beneficial to the resistivity improvement of cadmium telluride semiconductor crystal, ensuring the improvement of crystal performance. Moreover, the state of chloride containing cadmium or indium is more stable and not easy to sublimate, avoiding the risk of crucible bursting caused by excessive saturated vapor pressure caused by sublimation of metal Cd single substance at high temperature, thereby improving the safety of the annealing process.

[0047] In addition, the Cd element can compensate for the Cd vacancy defects caused by the crystal growth process, thereby increasing the crystal resistivity. The addition of the In element can effectively compensate for the uneven crystal composition caused by the segregation of the Zn element in the cadmium telluride series semiconductor crystals. At the same time, the In element can replace a small amount of Cd elements and Cd vacancies to form In doping, and the In element can form a Te-In chemical bond with the Te element in the cadmium telluride series semiconductor crystals, which not only consumes the Te inclusion phase, but also can greatly improve the crystal resistivity, carrier concentration and carrier mobility lifetime product, thereby improving the detector's responsiveness and response speed.

[0048] Moreover, in the molten state, the Cd and In elements themselves have high energy, and are more likely to interact with the cadmium telluride series semiconductor crystals, thereby deeply diffusing in the crystals, improving the annealing heat treatment efficiency, and overcoming the problems of long time, high energy consumption, and low efficiency caused by insufficient contact between the annealing agent and the crystal in gas phase annealing. Moreover, the liquid metal element in the prior art is easy to damage (etch) the crystal surface, while the chloride in the molten state will not damage the crystal surface, and is safer to use.

[0049] Optionally, the chloride containing cadmium may be CdCl2, and the chloride containing indium may be InCl2, to avoid introducing more impurities. Further optionally, the chloride containing cadmium and / or the chloride containing indium is a powder mixture of CdCl2 and InCl2. At this time, step S11 may be: preparing a molten annealing agent based on the powder mixture of CdCl2 and InCl2.

[0050] During the crystal growth process, because the Cd vapor pressure inside the crucible is too high, it is very difficult to dope the In element. In the present application, during the annealing of the CdCl2 and InCl2 mixed melt, CdCl2 does not form a large saturated vapor pressure, making it relatively easy to dope the In element.

[0051] Moreover, metal Cd has a very high vapor pressure at high temperatures, which can easily cause the crucible to explode, which is very dangerous. Using CdCl2 as an annealing agent can avoid this problem. In addition, InCl2 has a low melting point of about 262°C. After mixing with CdCl2 (melting point of about 568°C), the melting point of the mixture can be reduced to less than 500°C, which also has the effect of reducing the annealing temperature.

[0052] Optionally, in the powder mixture of CdCl2 and InCl2, the atomic ratio of CdCl2 and InCl2 is 100:(1-5). At this ratio, Cd vacancy compensation and In element doping can be achieved simultaneously, significantly improving the uniformity of crystal quality, resistivity and carrier transport properties. In some specific embodiments, the atomic ratio of CdCl2 and InCl2 may be 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5 or 100:5.

[0053] Optionally, step S11 specifically includes: heating the powder mixture of CdCl2 and InCl2 to a first temperature, and then maintaining the temperature at the first temperature and for a first time to melt the powder mixture of CdCl2 and InCl2 into a mixed melt of CdCl2 and InCl2.

[0054] Wherein, the first temperature may not exceed 500°C, and further optionally, the first temperature is 400-500°C. The melting point of the powder mixture of CdCl2 and InCl2 is about 500°C. To avoid overheating and sublimation of the melt, the temperature should not exceed 500°C. The above-mentioned first temperature can ensure that CdCl2 and InCl2 melt, and will not cause CdCl2 and InCl2 to sublime. In some specific embodiments, the first temperature may be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C.

[0055] The first duration may be greater than 1 hour, and further optionally, the first duration is 5 to 10 hours. During this time, CdCl2 and InCl2 can be completely melted without wasting time. In some specific embodiments, the first duration may be 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours or 10 hours.

[0056] Optionally, the heating rate of heating the powder mixture of CdCl2 and InCl2 to the first temperature is 50-70°C / h. A faster heating rate can make the powder mixture of CdCl2 and InCl2 melt quickly. In some specific embodiments, the heating rate may be 50°C / h, 52°C / h, 54°C / h, 56°C / h, 58°C / h, 60°C / h, 62°C / h, 64°C / h, 66°C / h, 68°C / h or 70°C / h.

[0057] After the above operations, the powder mixture of CdCl2 and InCl2 can be fully melted into a uniform melt.

[0058] S12: Annealing the cadmium telluride series semiconductor crystal using an annealing agent in a molten state.

[0059] Optionally, in step S12, the cadmium telluride series semiconductor crystal is first heated, and then immersed in the molten annealing agent prepared in step S11, thereby completing annealing. Preferably, the cadmium telluride series semiconductor crystal is completely immersed in the molten annealing agent.

[0060] The cadmium telluride series semiconductor crystal is first heated up to prevent the crystal from suddenly contacting the high-temperature molten annealing agent, which would cause the crystal to crack due to the sudden temperature change. At the same time, the atoms inside the cadmium telluride series semiconductor crystal are also placed in a relatively active state, so that they can react better with Cd and / or In elements.

[0061] Specifically, step S12 may include: heating the cadmium telluride series semiconductor crystal to a second temperature; wherein the second temperature is greater than or equal to the first temperature; and

[0062] The heated cadmium telluride series semiconductor crystal is immersed in a mixed melt of CdCl2 and InCl2, and then kept warm at a second temperature and for a second time.

[0063] The second temperature is the temperature at which the crystal reacts with the Cd and / or In element. If the second temperature is lower than the first temperature, the mixed melt of CdCl2 and InCl2 will solidify and cannot be annealed. Optionally, the second temperature is 500-600°C. In some specific embodiments, the second temperature may be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C.

[0064] Optionally, the second time is greater than 5 hours, and the crystal can fully react with the Cd and / or In element. Further optionally, the second time is 20 to 40 hours. In some specific embodiments, the second time may be 20 hours, 22 hours, 22 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours or 40 hours.

[0065] Optionally, the heating rate of heating the cadmium telluride series semiconductor crystal to the second temperature is 50-70°C / h. A faster heating rate can heat the cadmium telluride series semiconductor crystal quickly. In some specific embodiments, the heating rate may be 50°C / h, 52°C / h, 54°C / h, 56°C / h, 58°C / h, 60°C / h, 62°C / h, 64°C / h, 66°C / h, 68°C / h or 70°C / h.

[0066] Optionally, the cadmium telluride series semiconductor crystal is a cadmium telluride series semiconductor crystal grown by the Bridgman method, such as CdTe, Cd 1-x Zn x Te (0<x<1) or materials modified by doping with lanthanide rare earth, first group elements, second group elements, third group elements, and seventh group elements. Optionally, the cadmium telluride series semiconductor crystals reacted with the mixed melt of CdCl2 and InCl2 are wafers and / or crystal bars. The cadmium telluride series semiconductor crystals can be cut into blank wafers or crystal bars, and then the blank wafers or crystal bars are ground, polished, cleaned, and dried with nitrogen to obtain wafers or crystal bars.

[0067] Step S12: a mixture of CdCl2 and InCl2 powders and a cadmium telluride semiconductor crystal (such as Cd 1-x Zn xThe cadmium telluride series semiconductor crystals are heated to the corresponding temperature, and then immersed in a mixed melt of CdCl2 and InCl2. The cadmium telluride series semiconductor crystals can fully contact with the annealing agent. The Cd and In elements in the melt at high temperature have higher energy and are more likely to achieve deep diffusion inside the crystal, so that the Cd vacancies inside the crystal are fully compensated. The In element diffuses from the crystal surface to the inside until the solubility in the crystal reaches saturation, replacing a small amount of Cd elements and Cd vacancies to form In doping, and can form partial In-Te chemical bonds with the Te element, which not only consumes the Te inclusion phase, but also can well improve the carrier concentration and electron mobility of the crystal, thereby preparing a detector-level single crystal wafer / crystal bar that meets the requirements of high-energy radiation detection.

[0068] Optionally, the method further comprises separating the cadmium telluride series semiconductor crystal from the mixed melt of CdCl2 and InCl2, and cooling the cadmium telluride series semiconductor crystal to room temperature.

[0069] Optionally, the cadmium telluride semiconductor crystal is first cooled from the second temperature to the third temperature at a rate of 25-35°C / h, and then cooled to room temperature at a rate of 45-55°C / h. The cooling rate is slow at first and then fast, which helps to prevent the rapid temperature drop from causing the internal state of the crystal to be unstable.

[0070] In some specific embodiments, the initial cooling rate (i.e., the rate from the second temperature to the third temperature) may be 25°C / h, 27°C / h, 29°C / h, 31°C / h, 33°C / h, or 35°C / h. In some specific embodiments, the subsequent cooling rate (i.e., the rate from the third temperature to room temperature) may be 45°C / h, 47°C / h, 49°C / h, 51°C / h, 53°C / h, or 55°C / h.

[0071] Optionally, the third temperature is 150-300° C. Within the above temperature range, the crystal state is stable and can be quickly cooled to room temperature. In some specific embodiments, the third temperature can be 150° C., 170° C., 190° C., 200° C., 220° C., 240° C., 260° C., 280° C. or 300° C.

[0072] After cooling, the entire annealing process is completed.

[0073] Figure 2 A method for annealing a cadmium telluride series semiconductor crystal provided by another embodiment of the present application is shown. Figure 2 The annealing method shown is performed in a crucible, and includes the following S21 to S25.

[0074] S21: placing cadmium-containing chloride and / or indium-containing chloride and cadmium telluride series semiconductor crystals into a crucible, and removing oxygen attached to the surfaces of the crucible and the cadmium telluride series semiconductor crystals.

[0075] The oxygen on the crucible and the surface of the cadmium telluride series semiconductor crystal will react during the annealing process, thereby affecting the quality of the final crystal. Optionally, the oxygen attached to the surface of the crucible and the cadmium telluride series semiconductor crystal can be removed by vacuuming and backfilling with an inert atmosphere. In some specific embodiments, the crucible can be vacuumed to 10 -2 Pa, fill the crucible with inert gas (such as high-purity Ar gas), and then evacuate the inert gas. After repeating this process several times (such as 3 times), the atmosphere in the crucible is cleaned, thereby removing oxygen.

[0076] Optionally, when in use, the crucible is first soaked in an aqueous solution of hydrofluoric acid for about 10 minutes to remove impurities such as metal ions, and then ultrasonically cleaned with organic solvents (such as acetone, anhydrous ethanol) (each cleaning takes about 15 minutes) to remove organic impurities, and finally rinsed with deionized water several times (for example, 3 to 5 times) and dried (for example, dried in a clean oven at about 200°C).

[0077] S22: Pump the crucible pressure to 10 -2 Pa~10 -6 After pa, seal the crucible.

[0078] That is, the crucible is evacuated to perform a subsequent annealing step.

[0079] S23: while the crucible is maintained at the first position, preparing an annealing agent in a molten state based on a chloride containing cadmium and / or a chloride containing indium.

[0080] That is, the aforementioned step S11 is performed in a state where the crucible is maintained at the first position.

[0081] In the first position, the cadmium telluride semiconductor crystal is separated from the cadmium-containing chloride and / or the indium-containing chloride or the molten annealing agent. That is, at this time, although they are in the same crucible, the cadmium telluride semiconductor crystal and the cadmium-containing chloride and / or the indium-containing chloride (or the molten annealing agent) are separated and not in contact.

[0082] Specifically, the preparation of the annealing agent in a molten state based on the chloride containing cadmium and / or the chloride containing indium is as described in the aforementioned step S11, which will not be described in detail here.

[0083] S24: rotating the crucible from the first position to the second position, and annealing the cadmium telluride series semiconductor crystal using a molten annealing agent while the crucible is maintained at the second position.

[0084] That is, the aforementioned step S12 is performed while the crucible is maintained at the second position.

[0085] Wherein, at the second position, the cadmium telluride series semiconductor crystal is immersed in a molten annealing agent, thereby achieving annealing of the cadmium telluride series semiconductor crystal.

[0086] Specifically, the annealing agent in a molten state is used to anneal the cadmium telluride series semiconductor crystal, as in the aforementioned step S12, which will not be described in detail herein.

[0087] S25: rotating the crucible from the second position to the first position, thereby separating the cadmium telluride series semiconductor crystal from the mixed melt of CdCl2 and InCl2, and cooling the cadmium telluride series semiconductor crystal to room temperature.

[0088] In step S25, the cadmium telluride series semiconductor crystals are separated from the mixed melt of CdCl2 and InCl2 by rotating the crucible, and then the cadmium telluride series semiconductor crystals are cooled to room temperature, thus completing the entire annealing process. The specific cooling method is as described above and will not be repeated here.

[0089] The above-mentioned annealing method provided by the present application makes the Cd vacancies caused by growth in the cadmium telluride series semiconductor crystals compensated, and realizes the doping of the In element. At the same time, the In element and the Te element form a Te-In chemical bond, which not only consumes the Te inclusion phase, but also can increase the carrier concentration and electron mobility of the crystal, thereby improving the responsiveness and response speed of the detector including it, making the crystal more sensitive to gamma rays, and more suitable for photon counting detectors with high requirements for time response capability. Moreover, the present application controls the annealing temperature to be less than or equal to 600°C, and the entire heat treatment process takes less than 70 hours, which effectively solves the energy consumption and time consumption problems of annealing of cadmium telluride series semiconductor crystals.

[0090] The present application further provides an annealing device for cadmium telluride series semiconductor crystals, including a crucible, a heating furnace and a position adjustment device. Figure 2 The crucible of the annealing method is shown.

[0091] Figure 3 An annealing device 1000 provided in an embodiment of the present application is shown, comprising a crucible 100, a heating furnace 200, a position adjustment device 300 and a base 400. The crucible 100 may be a quartz crucible.

[0092] Figure 4 Shows Figure 3The specific structure of the crucible 100 is shown in FIG. 1 . The crucible 100 is bottle-shaped and includes a crucible cap 110, a crucible body 120 and a fixture 130. The crucible body 120 includes a first area 121 and a second area 122. The first area 121 is used to accommodate the aforementioned cadmium-containing chloride and / or indium-containing chloride, and the second area 122 is used to accommodate the aforementioned cadmium telluride series semiconductor crystals. The crucible cap 110 includes a crucible mouth 1101 and a connecting portion 1102 for connecting to the crucible body 120. When not in use, the crucible cap 110 and the crucible body 120 are separated. When in use (i.e., after the cadmium-containing chloride and / or indium-containing chloride and the cadmium telluride series semiconductor crystal are respectively placed in the first area 121 and the second area 122), the connecting portion 1102 of the crucible cap 110 can extend into the crucible body 120 (the upper part of the crucible body 120) and can be connected to the inner wall of the crucible body 120 through high-temperature sintering. Figure 4 What is shown is the effect after sintering.

[0093] Figure 4 In the embodiment shown, the chloride containing cadmium and / or the chloride containing indium B is placed in the first area 121. The second area 122 is provided with a slot for fixing the fixture 130. Figure 4 In the illustrated embodiment, after the connection portion 1102 of the crucible cap 110 and the crucible body 120 are sintered, a first protrusion 1231 is formed at the end of the sintered portion, and a second protrusion 1232 is further provided on the inner wall of the crucible body 120. The first protrusion 1231 and the second protrusion 1232 constitute a slot for fixing the clamp 130, and the clamp 130 can be confined in the slot. The second protrusion 1232 can be arranged in a circle around the inner wall of the second area 122, or can be distributed in a plurality of forms on the inner wall of the second area 122 at intervals. Under the action of the clamp 130, the cadmium telluride series semiconductor crystal A can be fixed in the second area 122. In this way, when the crucible 100 is in Figure 3 The position shown in (in this application, Figure 3 The position shown may also be referred to as the first position, where the first region 121 is at the bottom and the second region 122 is at the top), and the cadmium telluride series semiconductor crystal A and the cadmium-containing chloride and / or indium-containing chloride B are separated.

[0094] When in use, the fixture 130 with the cadmium telluride series semiconductor crystal A fixed thereon is first placed into the crucible body 120, and then the connecting portion 1102 of the crucible cap 110 is extended into the upper portion of the crucible body 120, and then the connecting portion 1102 and the crucible body 120 are subjected to high temperature sintering to be combined together. The first protrusion 1231 and the second protrusion 1232 formed at the sintering portion constitute a slot, and the fixture 130 is confined in the slot to confine the cadmium telluride series semiconductor crystal A in the second area 122. In order to prevent the cadmium telluride series semiconductor crystal A from being adversely affected during high temperature sintering, the cadmium telluride series semiconductor crystal A may not be placed in the slots of the fixture 130 close to the crucible cap 110 (i.e., the several rows of slots at the top of the fixture 130, such as one or two rows of slots).

[0095] Figure 4 In the illustrated embodiment, the clamp 130 has only a single row of groove sets. Figure 5 A crucible 100' provided in another embodiment of the present application is shown. Figure 4 The difference of the embodiment shown is that the fixture 130' of the second zone 122' has two rows of groove groups. Each row of groove groups can be provided with a plurality of grooves, and are evenly arranged along the longitudinal direction of the row, and each groove can define a cadmium telluride series semiconductor crystal A (such as a cadmium telluride series semiconductor wafer). In other embodiments of the present application, the number of rows of grooves and the number of each row can be set as needed. Although Figure 3 The crucible 100 is used in the figure, but the crucible 100' or other crucibles meeting the requirements may also be used.

[0096] like Figure 3 As shown, the heating furnace 200 includes a furnace body 210 for accommodating the crucible 100 or 100' and a heating device 220. The heating device 220 is used to heat the crucible 100 or 100' so that the cadmium-containing chloride and / or indium-containing chloride B melts into a molten annealing agent.

[0097] like Figure 3 As shown, the furnace body 210 includes a first temperature zone 211 and a second temperature zone 212, and the heating device 220 includes a first heating element 211A corresponding to the first temperature zone 211 and a second heating element 212A corresponding to the second temperature zone 212. When the crucible 100 or the crucible 100' is accommodated in the furnace body, the first heating element 211A in the first temperature zone 211 is used to heat the first zone 121 or the first zone 121', and the second heating element 212A in the second temperature zone 212 is used to heat the second zone 122 or the second zone 122'. The first heating element 211A and the second heating element 212A can be controlled separately, so that the first temperature zone 211 and the second temperature zone 212 can be controlled separately.

[0098] The position adjustment device 300 is connected to the heating furnace 200 and is used to adjust the position of the crucible 100 or the crucible 100' contained in the furnace body 210 to immerse the cadmium telluride series semiconductor crystal A in the molten annealing agent, thereby annealing the cadmium telluride series semiconductor crystal A using the molten annealing agent.

[0099] Figure 3 In the illustrated embodiment, the position adjustment device 300 includes a rotating shaft 310 and a motor 320. The rotating shaft 310 is connected to the furnace body 210, and the motor 320 is connected to the rotating shaft 310. Under the action of the motor 320, the rotating shaft 310 can rotate the furnace body 210, thereby driving the crucible 100 or the crucible 100' to rotate, so as to immerse the cadmium telluride series semiconductor crystal A in the molten annealing agent, thereby annealing the cadmium telluride series semiconductor crystal using the molten annealing agent. Two groups of rotating shafts 310 can be provided, respectively clamping the opposite sides of the furnace body 210, and driving the furnace body 210 to rotate through the rotation of the rotating shafts 310. The setting position of the rotating shaft 310 is preferably in the middle part of the axial direction of the furnace body 210, so as to drive the furnace body 210 to rotate evenly and improve stability.

[0100] Figure 3 In the embodiment shown, there is a pair of motors 320, which are respectively located on both sides of the heating furnace 200. In other embodiments of the present application, the number of motors 320 can be increased or decreased as needed. Figure 3 In the illustrated embodiment, the rotating shaft 310 and the motor 320 are connected to the base 400 . In other embodiments of the present application, the base 400 may be omitted or replaced by other components.

[0101] exist Figure 3 In the illustrated embodiment, the position of the crucible 100 includes a first position and a second position. In the first position, the second region 122 is located above the first region 121, and the cadmium telluride series semiconductor crystal A is separated from the molten annealing agent. In the second position, the second region 122 is located below the first region 121, and the cadmium telluride series semiconductor crystal A is immersed in the molten annealing agent.

[0102] by Figure 4 Taking the crucible 100 shown in FIG. as an example, in combination with the aforementioned Figure 2 When the cadmium telluride series semiconductor crystal A is fixed in the second region 122 and the cadmium-containing chloride and / or indium-containing chloride B is placed in the first region 121, the crucible 100 is in a state as follows: Figure 3 The first position shown, at this time is Figure 2 Step S21 is shown.

[0103] After completing step S21, step S22 is then performed, and then the crucible 100 is kept at Figure 3In the state of the first position shown, step S23 is performed to obtain the annealing agent in a molten state.

[0104] Then, step S24 is performed to remove the crucible 100 from Figure 3 The first position shown is rotated to the second position. In this embodiment, the second position may be a position where the second zone 122 is at the bottom and the first zone 121 is at the top, that is, the angle of rotation of the crucible 100 is 180°. In the second position, the molten annealing agent can flow from the first zone 121 into the second zone 122, so that the cadmium telluride series semiconductor crystal A is immersed in the molten annealing agent, thereby achieving annealing of the cadmium telluride series semiconductor crystal A.

[0105] After completing step S24, step S25 is then performed to rotate the crucible 100 from the second position to the first position again, and the molten annealing agent flows from the second area 122 into the first area 121, thereby separating the cadmium telluride series semiconductor crystal A from the molten annealing agent.

[0106] In the present application, the rotation angle of the crucible 100 from the first position to the second position or from the second position to the first position may be 120° to 180°, for example, 120°, 130°, 140°, 150°, 160°, 170° or 180°.

[0107] Optionally, the crucible 100 rotates from the first position to the second position or from the second position to the first position at a rotation speed of 1 to 5° / min, so that the molten annealing agent is slowly separated from the crystal (wafer or crystal bar), and the surface tension of the liquid is used to slowly separate the annealing agent from the crystal, and no annealing agent remains on the surface of the crystal. In some specific embodiments, the rotation speed may be 1° / min, 1.5° / min, 2° / min, 2.5° / min, 3° / min, 3.5° / min, 4° / min, 4.5° / min or 5° / min.

[0108] After completing step S25, the crucible 100 can be scratched with a glass cutter, and the crucible 100 can be carefully knocked open along the scratch to take out the crystal. In one embodiment of the present application, the crystal obtained by the above method was observed and found that the entire annealing process did not cause damage to the crystal surface. However, the prior art uses metal Cd annealing, which is very easy to etch the crystal surface, causing damage to the crystal surface. The present application avoids the problem of surface damage by using a melt as an annealing agent.

[0109] After being taken out from the crucible, the crystals can be ultrasonically cleaned with deionized water, ethanol, and deionized water in sequence (for example, each cleaning time is about 10 minutes), dried (for example, blown dry with nitrogen), and stored.

[0110] The annealing device provided in the present application is simple and can be used in conjunction with the annealing method provided in the present application to produce crystals with very good performance.

[0111] A specific application example of the embodiment of the present application is described below.

[0112] Cd grown by the Bridgman method 1-x Zn x Te (0 < x < 1) crystals are cut in a directional manner to obtain wafers, which are ground, polished, cleaned, dried with nitrogen and then wait for heat treatment. The quartz crucible used for heat treatment is first soaked in an aqueous solution of hydrofluoric acid for 10 minutes to remove impurities such as metal ions, then ultrasonically cleaned with acetone and anhydrous ethanol for 15 minutes each to remove organic impurities, and finally rinsed with deionized water for 3 to 5 times and dried in a clean oven at 200°C.

[0113] Insert the wafer into the groove of the quartz fixture to fix it. First, put a mixture of CdCl2 and InCl2 powders in the first area (bottom of the crucible), where the atomic ratio of CdCl2 and InCl2 is 100:1, and mix them evenly at the bottom of the crucible; then put the quartz fixture with the wafer on the second protrusion of the crucible steadily; connect the crucible cap to the crucible body through high-temperature sintering, so that the fixture is fixed between the first protrusion and the second protrusion formed at the sintering part. Evacuate the inside of the crucible to 10 -2 Pa, fill the crucible with high-purity Ar gas, and then pump out the Ar gas, repeat 3 times, clean the atmosphere in the crucible, remove the oxygen attached to the crucible and the surface of the wafer, and finally pump the pressure in the crucible to ≤10 -4 Pa, high temperature sintering to seal the crucible mouth.

[0114] Place the sealed crucible vertically into the heating furnace for heat treatment. Place the annealing agent in the first temperature zone and the chip in the second temperature zone. Slowly raise the second temperature zone to 500-600°C at a rate of 50-70°C / h, and at the same time raise the first temperature zone to 400-500°C, and keep it at this temperature for 5-10 hours, so that the CdCl2 and InCl2 mixture is fully melted into a uniform melt. Turn on the rotary motor and rotate the heating furnace 120-180° along the axis until the chip is immersed in the melt. Then continue to keep the temperature zone where the chip is located at 500-600°C for 20-40 hours for annealing.

[0115] After annealing is completed, the annealing furnace is rotated counterclockwise at a speed of 1 to 5° / min back to the initial position to slowly separate the molten medium from the wafer until the separation is complete. After annealing, the first temperature zone where the wafer is located is first cooled to 200°C at a rate of 30°C / h, and then cooled to room temperature at a rate of 50°C / h, and the second temperature zone is naturally cooled to room temperature.

[0116] Use a glass knife to cut the quartz crucible and take out the wafer. It is observed that the heat treatment process does not cause damage to the wafer surface. The wafer is ultrasonically cleaned with deionized water, ethanol, and deionized water for 10 minutes each, and then dried with nitrogen for storage.

[0117] The test results show that the resistivity of the crystal ranges from 6.53 to 8.71×10 7 Ωcm increased to 5.27~7.11×10 10 Ωcm, achieving a three-order-of-magnitude improvement; the electrical properties of the chip were then tested, and the carrier mobility-lifetime product (μτ) of the crystal was found to be ~10 -4 cm 2 / V increased to ~10 -3 cm 2 / V level. It proves that the defect density and performance of cadmium telluride series semiconductor crystals are significantly improved after melt annealing.

[0118] The present application further provides a cadmium telluride series semiconductor crystal produced by the above annealing method or annealing device. The crystal is doped with In element. Optionally, the crystal also includes Te-In chemical bonds.

[0119] Optionally, the resistivity of the crystal is ≥5×10 10 Ω·cm, carrier mobility lifetime product ≥ 1×10 -3 cm 2 / V. Compared with the existing technology, the resistivity of the crystal has been improved by 3 orders of magnitude, and the carrier mobility lifetime product has increased from ~10 -4 cm 2 / V increased to ~10 -3 cm 2 / V level.

[0120] Optionally, the crystal includes CdTe, Cd 1-x Zn xTe (0<x<1) or materials modified by lanthanide rare earth, first group elements, second group elements, third group elements, and seventh group elements. Lanthanide rare earth elements may include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). First group elements may include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), copper (Cu), silver (Ag), and gold (Au). Second group elements may include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), zinc (Zn), cadmium (Cd), mercury (Hg), and Uub. The third group elements may include boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Ta). The seventh group elements may include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

[0121] The crystal provided in this application has uniform quality, and its resistivity and carrier transport properties can meet the requirements of photon counting detectors.

[0122] The above description is only an example embodiment of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An annealing device for cadmium telluride series semiconductor crystals, characterized in that: include: A crucible having a first region and a second region, wherein the first region is used to accommodate a chloride containing cadmium and / or a chloride containing indium, and the second region is used to accommodate a cadmium telluride series semiconductor crystal; A heating furnace, comprising a furnace body for accommodating the crucible and a heating device, wherein the heating device is used to heat the crucible so that the cadmium-containing chloride and / or the indium-containing chloride is melted into a molten annealing agent; A position adjustment device is connected to the heating furnace and is used to adjust the position of the crucible contained in the furnace body so as to immerse the cadmium telluride series semiconductor crystal in the molten annealing agent, thereby annealing the cadmium telluride series semiconductor crystal using the molten annealing agent.

2. The annealing device according to claim 1, characterized in that: The position adjustment device comprises: A rotating shaft connected to the furnace body; and A motor is connected to the rotating shaft. Under the action of the motor, the rotating shaft can rotate the furnace body, thereby driving the crucible to rotate, so as to immerse the cadmium telluride series semiconductor crystals in the molten annealing agent, thereby annealing the cadmium telluride series semiconductor crystals using the molten annealing agent.

3. The annealing device according to claim 1, characterized in that: The position of the crucible includes a first position and a second position, wherein, in the first position, the second zone is located above the first zone, and the cadmium telluride series semiconductor crystal is separated from the molten annealing agent, and in the second position, the second zone is located below the first zone, and the cadmium telluride series semiconductor crystal is immersed in the molten annealing agent.

4. The annealing device according to claim 3, characterized in that: The crucible rotates from the first position to the second position or from the second position to the first position at a rotation angle of 120° to 180°.

5. The annealing device according to claim 1, characterized in that: The annealing device further comprises a fixture, wherein the fixture has a groove, and the groove is used to fix the cadmium telluride series semiconductor crystal; The second area of ​​the crucible is provided with a slot for fixing the clamp.

6. The annealing device according to claim 5, characterized in that: The clamp has one or more rows of groove groups, and each row of groove groups is provided with a plurality of the grooves.

7. The annealing device according to claim 5, characterized in that: The crucible comprises a crucible cap and a crucible body, wherein the crucible cap comprises a crucible mouth and a connecting portion for connecting with the crucible body; the connecting portion can extend into the crucible body and be connected with the inner wall of the crucible body by high-temperature sintering; After the connecting portion and the crucible body are sintered, a first protrusion is formed at the end of the sintered portion, and a second protrusion is further provided on the inner wall of the crucible body. The first protrusion and the second protrusion constitute a slot for fixing the clamp.

8. The annealing device according to claim 1, characterized in that: The furnace body includes a first temperature zone and a second temperature zone, and the heating device includes a first heating element arranged corresponding to the first temperature zone and a second heating element arranged corresponding to the second temperature zone; wherein the first heating element in the first temperature zone is used to heat the first zone, and the second heating element in the second temperature zone is used to heat the second zone.

9. The annealing device according to claim 8, characterized in that: The first heating element and the second heating element can be controlled individually.

10. A cadmium telluride series semiconductor crystal, characterized in that: It is produced by the annealing device described in any one of claims 1 to 9.

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