Method for producing compound semiconductor polycrystal

Abstract

The application discloses a preparation method of a compound semiconductor polycrystal material, and belongs to the technical field of semiconductor material manufacturing.The method is based on a synthesis furnace for high-pressure synthesis of a compound semiconductor by an in-situ injection method, and the key point is that a forming die is additionally arranged in a furnace cavity of the synthesis furnace, and the forming die is connected with a matched lifting driving mechanism through a lifting rod.The specific preparation steps comprise the following steps: preparing the forming die with a forming cavity with an open end; suspending the forming die above a crucible through the lifting rod penetrating through a furnace top cover and aligning the open end of the forming cavity downward to the crucible; utilizing the in-situ injection method to high-pressure synthesize a compound melt; lowering the forming die into the compound melt in the crucible; filling the compound melt into the forming cavity from the lower open end; and gradually cooling and solidifying the melt to form the polycrystal material matched with the forming cavity.The method realizes rapid preparation of high-purity compound semiconductor polycrystal material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor material manufacturing, and relates to preparation of polycrystalline material for VGF growth of compound semiconductor single crystal, in particular to a method for preparing polycrystalline material of compound semiconductor in various shapes and specifications by means of a forming die after in-situ injection synthesis. BACKGROUND

[0002] There are many compound semiconductor materials with excellent performance in group III-V and group II-VI elements. For example, indium phosphide is an excellent semiconductor material and is widely used in many high-tech fields. However, indium phosphide needs to be synthesized at high pressure, and before preparing indium phosphide single crystal, indium and phosphorus meeting certain purity requirements must be synthesized into compound indium phosphide polycrystal, on the basis of which indium phosphide single crystal can be further prepared. Rapid and effective synthesis of indium phosphide polycrystal is an important way to reduce production cost and improve production efficiency, and is also a prerequisite for preparing high-quality indium phosphide single crystal. The main methods for synthesizing indium phosphide polycrystal at present are horizontal synthesis method and injection synthesis method. The polycrystalline material after synthesis is mainly grown in a VGF high-pressure furnace to obtain compound semiconductor materials with excellent electrical properties. The horizontal synthesis method is generally a three-temperature-zone horizontal synthesis, and the synthesis time is about 3-5 days. The synthesized polycrystalline material is prone to indium enrichment, and the quartz tube is seriously contaminated, resulting in poor product quality. The injection synthesis method has high speed, purity and efficiency. The compound polycrystalline material synthesized by the above two methods needs to be cut and cleaned before being put into the VGF high-pressure furnace for growth. In the whole preparation process, contamination and refractory oxide are easily produced, and the probability of impurities entering the material is high, which will cause impurity compensation and reduce the electrical quality of the wafer. Moreover, during the single crystal growth process, the introduction of impurities easily causes twinning at the solid-liquid interface, resulting in a decrease in single crystal rate. Therefore, how to take advantage of the in-situ injection synthesis method to quickly form polycrystalline material in various shapes and specifications after in-situ injection synthesis is a problem to be solved by the present application. SUMMARY

[0003] In order to realize the rapid preparation of high-purity compound semiconductor polycrystalline material in various shapes and specifications, the present application adopts the in-situ injection method to directly form polycrystalline material of different diameters in-situ by a die after high-pressure synthesis of the melt, which greatly improves the production efficiency and the utilization rate of polycrystalline material, and ensures the purity of the polycrystalline material and the single crystal.

[0004] The technical scheme of the present application is: a preparation method of compound semiconductor polycrystalline material, which is based on a synthesis furnace for high-pressure synthesis of compound semiconductor by in-situ injection method, and the key lies in that a forming die is additionally arranged in the furnace cavity of the synthesis furnace, and the forming die is connected with a matching lifting driving mechanism through a lifting rod. The specific preparation steps include: A. Preparation of molding mold: According to the crucible size and the requirements for the shape and specifications of the polycrystalline material, fire an alumina ceramic block with a molding cavity, or select an alumina ceramic block and open a molding cavity with an opening at the bottom of the molding cavity; B. Install the molding mold: Install a lifting rod at the top center of the molding mold. The lifting rod passes through the furnace top cover and connects to the matching lifting drive mechanism, so that the molding mold is suspended above the crucible, with the opening of the molding cavity facing downward and aligned with the crucible. C. Polycrystalline material synthesis: Place the pure metal to be synthesized into a crucible, add a covering agent, add another element to be injected into the source furnace, close the furnace top cover, and evacuate; then fill with a certain pressure of high-purity protective gas to ensure that the furnace pressure is higher than the dissociation pressure of the molten material; heat the crucible to melt the pure metal; after the molten material in the crucible stabilizes, lower the source furnace and insert the gas guide pipe into the molten material in the crucible to heat the source furnace. The volatile elements in the source furnace are liquefied or volatilized by the heat and continuously injected into the molten material in liquid or gaseous form to react with the molten material and synthesize the compound molten material. D. Polycrystalline material forming: When the compound melt to be synthesized reaches the set ratio, the source furnace is lifted and rotated away from the crucible. After the temperature of the compound melt stabilizes, the forming mold is lowered into the compound melt in the crucible. The compound melt is filled into the forming cavity from the lower opening. The melt gradually cools down and solidifies to form a polycrystalline material that matches the forming cavity. F. Demolding: After the temperature inside the furnace drops to room temperature, open the furnace top cover and remove the prepared semiconductor polycrystalline material from the molding cavity.

[0005] Furthermore, the gradual cooling and solidification process in step F is as follows: cooling at 65℃ / h for three hours, at 120℃ / h for three hours, and at 300℃ / h for one hour, then turning off the heating program and cooling to room temperature. Within the solidification temperature range of the compound melt, a slow cooling rate is used to allow sufficient time for the solute to be expelled to the solid-liquid interface. Using this cooling gradient can yield polycrystalline materials with uniform surface and internal composition, free from indium and phosphorus precipitation, and without inclusions such as pores.

[0006] Furthermore, in step D, the forming mold is spirally lowered into the molten compound in the crucible using a matching lifting drive mechanism. The rotation speed is 5-20 r / min, and it stops after reaching the bottom of the crucible. The rotation of the mold in the melt provides a certain stirring effect, making the temperature and composition distribution of the melt more uniform, and making it easier to obtain a homogeneous polycrystalline material through solidification. The preferred rotation speed is 10 r / min.

[0007] Furthermore, to facilitate demolding and manufacturing, the draft angle of the molding cavity of the molding die prepared in step A is 0.3-0.8 degrees.

[0008] Furthermore, the draft angle of the molding cavity is preferably 0.5 degrees.

[0009] Furthermore, depending on the crucible size and actual requirements, the molding die prepared in step A has 4-8 molding cavities distributed on it.

[0010] Furthermore, the cross-sectional shape of the molding cavity is generally circular or square. In order to facilitate molding and demolding, the transition surfaces of the square-section cavity are treated with arc transition.

[0011] Furthermore, depending on the furnace body specifications, in order to facilitate molding and demolding, the diameter of the circular cavity or the side length of the square cavity is 2-6 inches.

[0012] Furthermore, in order to maintain the stability of the molding die's movement, the supporting lifting drive mechanism includes a motor positioned on the furnace top cover and a lead screw and nut assembly connected to the motor, with the other end of the lifting rod positioned on the lead screw or nut.

[0013] Furthermore, the supporting lifting drive mechanism is a screw jack positioned on the furnace top cover, and the screw jack's lead screw is connected to the lifting rod.

[0014] The beneficial effects of this invention are as follows: 1. This invention fully utilizes the advantages of the in-situ injection synthesis method, employing high-pressure injection to synthesize compound semiconductor melts, and then preparing polycrystalline compound semiconductor materials for VGF method growth through cooling and solidification. This presents a significant technical advantage in the rapid preparation of high-purity compound semiconductor polycrystalline materials. Using the preparation method of this invention, polycrystalline materials for GaAs, GaP, AlP, InSb, ZnTe, CdZnTe, CdMnTe, etc., grown using the VGF / VB method can be prepared. 2. By adding a liftable forming mold within the high-pressure furnace cavity, polycrystalline materials of various shapes and specifications can be produced, greatly improving the utilization rate of polycrystalline materials. This avoids the introduction of impurities during the cutting, cleaning, and etching processes of polycrystalline materials, improves the purity of the compound melt during single crystal preparation, reduces the probability of twin nucleation caused by impurities, and improves the electrical performance of the wafer. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the synthesis furnace structure with the molding die of the present invention in the embodiment; Figure 2 This is a schematic diagram of the installation structure of the molding die in the furnace cavity in the embodiment; Figure 3 This is a schematic diagram of the molding cavity structure as seen from the bottom of the molding die in the embodiment; Figure 4 This is a schematic diagram of the structure when the compound melt is filled into the molding cavity in the embodiment; In the attached diagram, 1 represents the furnace frame, 10 represents the support plate, 11 represents the column, 12 represents the connecting pipe, 13 represents the source furnace, 14 represents the gas guide pipe, 2 represents the lifting rod, 3 represents the crucible, 4 represents the forming mold, 41 represents the forming cavity, 5 represents the screw lift, 6 represents the base, 7 represents the furnace cavity, 8 represents the furnace top cover, and 9 represents the melt. Detailed Implementation

[0016] In existing technologies, high-pressure synthesis furnaces used for in-situ injection synthesis of compound semiconductors typically consist of an electrical control system, a pressure control system, a vacuum system, a cooling circulation system, a volatile element injection system, and a furnace body. The furnace body includes a base, a furnace cavity, and a furnace top cover. The crucible is mounted on the base. For in-situ injection high-pressure synthesis furnaces, the volatile element injection system includes a source furnace for melting volatile elements, a gas guide pipe for injecting the volatile elements from the source furnace into the crucible, and a system for driving the source furnace to rise, fall, and rotate. This type of high-pressure furnace allows the source furnace to be lowered after the raw materials are melted, enabling the molten elements to be injected into the crucible through the gas guide pipe to synthesize with the raw materials. Once the set ratio is achieved, the source furnace is lifted from the crucible and rotated away from the crucible. This method minimizes material contamination, offers fast injection synthesis time, and is highly efficient and produces high-purity results. Such high-pressure furnaces are disclosed in patent documents with publication numbers CN 104451858 A, 105543949 A, and 105568363 A. In order to improve production efficiency and the purity of polycrystalline materials, the present invention preferably uses a high-pressure synthesis furnace based on the injection method for synthesizing compound semiconductors. A forming mold 4 and a lifting rod 2 positioned on the forming mold 4 are added inside the furnace cavity 7. The lifting rod 2 passes through the furnace top cover 8 and is connected to a matching lifting drive mechanism. The forming mold 4 is set above the crucible 3 containing the synthesis melt 9 and has forming cavities 41 with their lower openings aligned with the crucible 3.

[0017] For a specific embodiment, please refer to the accompanying drawings. This method is based on the high-pressure in-situ synthesis multifunctional crystal growth system disclosed in CN 104451858 A. When this high-pressure in-situ synthesis multifunctional crystal growth system is used for high-pressure in-situ synthesis of polycrystalline materials, the seed crystal rod, the first weight sensor, and the matching lifting mechanism are not required. The molding device of this invention is modified accordingly. The remaining configuration and structure remain unchanged, and the original seed crystal rod lifting mechanism is used. Only the seed crystal rod is replaced with a lifting rod 2, and the molding mold 4 is installed on the lifting rod 2. Specifically, a column 11 is fixed on the support plate 10 of the furnace frame 1, and a screw jack 5 is fixed on the column 11. One end of the connecting pipe 12 is fixedly connected to the support plate 10, and the other end is fixedly connected to the furnace top cover 8 and communicates with the furnace cavity 7. The screw of the screw jack 5 is connected to the lifting rod 2, and the other end of the lifting rod 2 enters the furnace cavity 7 through the connecting pipe 12 and connects with the molding mold 4. The crucible 3 is placed on the base 6. The molding mold 4 is sized to match the crucible 3 and is suspended above the crucible 3 containing the synthetic melt 9 by a lifting rod 2. The lifting rod 2 is installed at the center of the top, and the opening of the molding cavity 41 is aligned with the crucible. The draft angle of the molding cavity 41 is 0.5 degrees, there are 4 of them, the cross-sectional shape is square, and the transition surfaces are rounded. The molding mold 4 is made of alumina ceramic.

[0018] In practice, taking the preparation of indium phosphide polycrystalline material as an example, the specific steps are as follows: A. Preparation of molding mold 4: Select an alumina ceramic block according to the size of crucible 3, and symmetrically open four cubes with a draft angle of 0.5 degrees on the ceramic block to form a cavity 41. The bottom of the molding cavity 41 is open, with a side length of 3.5cm, and the transition surfaces are rounded.

[0019] B. Install the molding mold 4: Fix the screw jack 5 on the column 11 on the support plate 10. The furnace top cover 8 is lifted by the lifting mechanism of the furnace top cover 8. Install the lifting rod 2 at the top center of the molding mold 4 and put it into the furnace cavity 7. The lifting rod 2 passes through the connecting pipe 12 and is connected to the screw of the screw jack 5, so that the molding mold 4 is suspended above the crucible 3 and the opening of the molding cavity 41 faces downward and is aligned with the crucible 3.

[0020] C. Polycrystalline material synthesis: High-purity indium is placed in crucible 3, along with dopant and boron oxide. Phosphorus to be injected is added into source furnace 13. The furnace top cover 8 is closed, and a vacuum is drawn to 5 Pa. Then, high-purity argon gas is introduced to 3.0 MPa. Crucible 3 is heated to 50 K above the melting point of indium phosphide. Crucible 3 is rotated while being heated to melt the indium. After the melt in crucible 3 is stable, source furnace 13 is lowered, and gas pipe 14 is inserted into the melt in crucible 3. Source furnace 13 is heated, and the phosphorus in source furnace 13 is liquefied or volatilized by the heat. It is continuously injected into the melt in liquid or gaseous form to react with the melt and synthesize indium phosphide melt.

[0021] D. Polycrystalline Material Forming: When the indium phosphide melt to be synthesized reaches the set ratio, the source furnace 13 is lifted, the gas pipe 14 is pulled out from the indium phosphide melt, and the source furnace 13 is rotated away from the crucible 3. After the crucible 3 stops rotating and the temperature of the indium phosphide melt stabilizes, the forming mold 4 is lowered into the indium phosphide melt in the crucible 3 at a speed of 10 r / min and then stopped. The indium phosphide melt is filled into the forming cavity 41 from the lower opening and gradually cooled at a rate of 65℃ / h for three hours, 120℃ / h for three hours, 300℃ / h for one hour, and then the heating program is turned off and cooled to room temperature. The indium phosphide melt solidifies to form a polycrystalline material that matches the forming cavity 41.

[0022] F. Demolding: After the temperature inside the furnace drops to room temperature, open the furnace top cover 8 and take out the prepared semiconductor polycrystalline material from the molding cavity 41.

[0023] The carrier concentration of the prepared undoped indium phosphide polycrystalline material is (2-6) × 10¹⁵ cm⁻³; the mobility is ≥ 3500 cm²V⁻¹S⁻¹. This invention is applicable to the preparation of binary and multi-component compound semiconductor polycrystalline materials of different diameters, such as GaAs, GaP, AlP, InSb, ZnTe, CdZnTe, CdMnTe, and other III-V and II-VI group compound polycrystalline materials; the implantation synthesis process can be carried out under negative pressure, normal pressure, or high pressure atmosphere.

Claims

1. A method for preparing polycrystalline compound semiconductors, the method being based on a high-pressure synthesis furnace for in-situ implantation of compound semiconductors, characterized in that: A molding die (4) is added inside the furnace cavity (7) of the synthesis furnace. The molding die (4) is connected to the matching lifting drive mechanism through the lifting rod (2). The specific preparation steps include: A. Prepare molding mold (4): According to the size of crucible (3) and the requirements for the shape and specifications of polycrystalline material, fire an alumina ceramic block with molding cavity (41) or select an alumina ceramic block and open molding cavity (41), with the lower end of molding cavity (41) open; B. Install the molding mold (4): Install the lifting rod (2) at the top center of the molding mold (4). The lifting rod (2) passes through the furnace top cover (8) and connects to the matching lifting drive mechanism, so that the molding mold (4) is suspended above the crucible (3) and the opening of the molding cavity (41) faces downward and is aligned with the crucible (3). C. Polycrystalline material synthesis: Place the pure metal to be synthesized into a crucible (3), add a covering agent, add another element to be injected into the source furnace (13), close the furnace top cover (8), and evacuate; then fill with a certain pressure of high-purity protective gas to ensure that the furnace pressure is higher than the dissociation pressure of the molten material; heat the crucible (3) to melt the pure metal; after the molten material in the crucible (3) is stable, lower the source furnace (13) and insert the gas guide pipe (14) into the molten material in the crucible (3), heat the source furnace (13), and the volatile elements in the source furnace (13) are liquefied or volatilized by heating, and continuously injected into the molten material in liquid or gas form to react with the molten material and synthesize the compound molten material; D. Polycrystalline material forming: When the compound melt to be synthesized reaches the set ratio, the source furnace (13) is lifted and rotated away from the crucible (3). After the temperature of the compound melt stabilizes, the forming mold (4) is lowered into the compound melt in the crucible (3). The compound melt is filled into the forming cavity (41) from the lower opening. The melt gradually cools down and solidifies to form a polycrystalline material that matches the forming cavity (41). E. Demolding: After the temperature inside the furnace drops to room temperature, open the furnace top cover (8) and take out the prepared semiconductor polycrystalline material from the molding cavity (41); The gradual cooling and solidification process in step D is as follows: cooling at 65℃ / h for three hours, at 120℃ / h for three hours, at 300℃ / h for one hour, then turning off the heating program and cooling to room temperature; In step D, the forming mold (4) is spirally lifted by a matching lifting drive mechanism. When it descends into the compound melt in the crucible (3), the rotation speed is 5-20 r / min, and it stops after descending to the bottom of the crucible (3).

2. The method for preparing a compound semiconductor polycrystalline material according to claim 1, characterized in that: The draft angle of the molding cavity (41) of the molding mold (4) prepared in step A is 0.3-0.8 degrees.

3. The method for preparing a compound semiconductor polycrystalline material according to claim 2, characterized in that: The draft angle of the forming cavity (41) is 0.5 degrees.

4. A method for preparing a compound semiconductor polycrystalline material according to any one of claims 1-3, characterized in that: The molding die (4) prepared in step A has 4-8 molding cavities (41) distributed on it.

5. The method for preparing a compound semiconductor polycrystalline material according to claim 4, characterized in that: The cross-sectional shape of the molding cavity (41) is circular or square, and the transition surfaces of the square cavity are treated with arc transition.

6. The method for preparing a compound semiconductor polycrystalline material according to claim 5, characterized in that: The diameter of the circular cavity or the side length of the square cavity is 2-6 inches.

7. The method for preparing a compound semiconductor polycrystalline material according to claim 5, characterized in that: The supporting lifting drive mechanism includes a motor positioned on the furnace top cover (8) and a lead screw and nut assembly connected to the motor, with the other end of the lifting rod (2) positioned on the lead screw or nut.

8. The method for preparing a compound semiconductor polycrystalline material according to claim 7, characterized in that: The supporting lifting drive mechanism is a screw jack (5) positioned on the furnace top cover (8), and the screw of the screw jack (5) is connected to the lifting rod (2).

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