Apparatus and method for manufacturing indium phosphide crystals by vertical temperature gradient solidification

Abstract

Provided are an apparatus and a method for manufacturing indium phosphide crystals by vertical temperature gradient solidification. The apparatus includes a furnace body, a crucible, a centrifugal motor, and an injection system. During synthesis, the crucible is rotated to bring the melt in the crucible into close contact with the side wall of the crucible under the action of centrifugal force, and bubbles are injected into a position close to the side wall of the crucible of the metal melt. After the synthesis is completed, the vertical temperature gradient is controlled to end single crystal growth.

Description

Technical Field

[0001] The present invention relates to the manufacture of semiconductor materials, and more particularly to an apparatus and method for manufacturing indium phosphide crystals by vertical temperature gradient solidification.

Background Art

[0002] InP (indium phosphide) is an important compound semiconductor material following silicon (Si), germanium (Ge), and gallium arsenide (GaAs), and is one of the optimal materials for manufacturing high-frequency and high-speed devices. InP-based microelectronic devices have characteristics such as high frequency, low noise, high efficiency, and radiation resistance, and are widely applied in fields such as 5G networks, space solar cells, terahertz communication, millimeter-wave communication, and sounding. The faster the InP synthesis, the less external contamination, and the easier it is to manufacture high-performance InP crystals.

[0003] The main synthesis methods of InP are the solute synthesis diffusion method (SSD), the horizontal Bridgman method (HB) / horizontal temperature gradient solidification method (HGF), and the injection synthesis method. Among them, the injection synthesis method is the method with the highest efficiency and can realize polycrystalline industrialization at low cost and high quality. For example, Chinese patents with application numbers 202010487276.2, 202110618242.7, 201911155615.0, 202110145424.7, etc. disclose technical solutions for synthesizing compound semiconductor materials using a gas injection device. After heating and vaporizing the volatile source material, the vaporized elements are injected through an injection tube into a stationary or slowly rotating melt to complete the synthesis.

[0004] In the melt, initially, it is pure indium, and as phosphorus atoms enter the indium melt, an indium-phosphorus melt is formed. When the temperature drops to the crystallization temperature (below the melting point of indium phosphide) and the phosphorus component reaches or exceeds 50% atomic percentage, the solidified melt turns into indium phosphide, and excess phosphorus overflows. When the phosphorus component is less than 50% atomic percentage, the melt solidifies into indium phosphide and indium.

[0005] The synthesis time of indium phosphide mainly depends on the rate at which the melt absorbs phosphorus element. At a constant temperature, the greater the difference between the saturated phosphorus concentration in the melt and the phosphorus concentration in the melt, the faster the rate at which the melt absorbs phosphorus element.

[0006] At the initial stage when phosphorus enters the melt, the phosphorus concentration in the melt is low, and the rate at which the melt absorbs phosphorus element is fast. As the synthesis progresses, the phosphorus concentration in the melt increases, the ability of the melt to absorb phosphorus deteriorates, and the rate at which the melt absorbs phosphorus slows down.

Summary of the Invention

Problems to be Solved by the Invention

[0007] In response to the problems existing in the prior art, the present invention proposes a method for accelerating the synthesis rate and realizing in-situ growth of single crystals.

Means for Solving the Problems

[0008] To achieve this purpose, the present invention adopts the following technical solutions.

[0009] An apparatus for producing indium phosphide crystals by vertical temperature gradient solidification, including a furnace body, a crucible placed on a support holder, a seed crystal groove provided at the bottom of the crucible, a multi-stage heater on the outer periphery of the crucible, a motor, a support rod connecting the support holder and the motor, an injection system, and a thermocouple. Importantly, it is as follows. The motor is a centrifugal motor, the apparatus further includes a cutoff lid covering the central opening of the crucible, the injection system includes an injection can, a laterally provided injection pipe, a transport pipe connecting the injection can and the injection pipe, and an auxiliary heating system provided on the outer periphery of the injection can. The transport pipe penetrates the cutoff lid, and the injection pipe is provided inside the crucible. The top of the injection system is connected to a separable moving rod, and the moving rod is connected to a driving device. There are limiting devices that fit with each other at the bottom of the injection system and the top of the cutoff lid.

[0010] Furthermore, the outlet of the injection tube is close to the side wall of the crucible.

[0011] Based on the above device, the present invention is a method for manufacturing indium phosphide crystals by vertical temperature gradient solidification, comprising: Step 1: placing a seed crystal in the seed crystal tank of the crucible, putting metallic indium and boron oxide into the crucible, putting red phosphorus into the injection can, and assembling the device; Step 2: filling the furnace body with a pressure of 4.0 - 8.0 MPa for protection; Step 3: heating the crucible to 500 - 600 °C by a multi-stage heater to melt boron oxide and metallic indium, driving a separable moving rod by a driving device, placing the injection system on the shielding lid, fitting the limiting device, and separating the separable moving rod from the injection system; Step 4: starting a centrifugal motor with a rotation speed of 500 - 5000 revolutions per minute to rotate the support rod and the crucible; Step 5: heating the crucible 30 - 200 °C higher than the melting point of indium phosphide by a multi-stage heater, starting the auxiliary heating system, heating the injection can to 600 - 900 °C, sublimating the red phosphorus in the injection can, discharging the gas from the injection tube into the metal melt, and performing centrifugal injection synthesis; After the synthesis, adjusting the power of each stage heater of the multi-stage heater, setting the temperatures of thermocouple E, thermocouple A, and thermocouple D to 500 - 800 °C, solidifying the synthesized indium phosphide into a cylindrical solid, and turning boron oxide into a liquid; Step 6: gradually reducing the rotation speed of the centrifugal motor until it stops, and allowing all the boron oxide to flow to the bottom of the crucible; Inserting thermocouple B and thermocouple C, adjusting the power of each stage heater of the multi-stage heater, setting thermocouple E 20 - 50 °C lower than the melting point of indium phosphide, setting thermocouple A and thermocouple D 50 - 200 °C higher than the melting point of indium phosphide, remelting the cylindrical solid indium phosphide into a liquid and flowing it to the bottom of the crucible, pulling up the injection system; Step 7: establishing a temperature gradient of 5 - 50 cm / °C for the indium phosphide melt in the crucible, with the direction close to the seed crystal being the low-temperature direction; Adjust the power of each stage heater of the multi-stage heater to achieve indium phosphide single crystal growth. After the growth is completed, cool the system to room temperature and take out the single crystal in step 8. Further provided is a method for manufacturing indium phosphide crystals by vertical temperature gradient solidification.

[0012] During polycrystalline synthesis, the density of indium in the melt (7.3 g / m 3 ) is larger than that of the combined phosphorus atoms and indium atoms (the density of indium phosphide is approximately 4.787 g / cm 3 and can be calculated approximately), and the density of boron oxide as a coating agent (1.8 g / m 3 ) is the lowest. The centrifugal force can change the change in the spatial distribution concentration in the indium phosphide melt. In the crucible, pure indium is on the outermost periphery, the combined phosphorus atoms and indium atoms move together, and the inside and the innermost part of pure indium are boron oxide. The outlet of the injection tube is at the edge of the crucible. In the melt around the injection region, pure indium that has not combined with phosphorus atoms is distributed, and the phosphorus content is always the lowest among all the melts and can absorb phosphorus at high speed.

[0013] After the synthesis is completed, stop the rotation of the crucible, bring the melt into contact with the seed crystal, and conduct crystal growth.

Advantages of the Invention

[0014] Beneficial effects: Under the action of the centrifugal force, the indium atoms with a heavy density move in the direction of the edge of the crucible, and the phosphorus atoms with a light density move towards the center of the crucible, increasing the indium atoms on the side wall of the crucible. Since the concentration of phosphorus atoms around the injection region is low, the synthesis speed is fast, accelerating the overall synthesis process. By combining centrifugal high-speed synthesis and crystal growth, the temperature gradient in the vertical direction during single crystal growth can be accurately controlled, further improving the efficiency of crystal growth after injection synthesis.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Embodiments for Carrying Out the Invention

[0016] For an apparatus for manufacturing indium phosphide crystals by vertical temperature gradient solidification, refer to FIG. 1.

[0017] The apparatus includes a furnace body, a crucible 1 placed on a support holder 2 provided in the furnace body, a seed crystal bath 1-2 provided at the bottom of the crucible 1, a multi-stage heater 3 on the outer periphery of the crucible 1, a centrifugal motor 7, a support rod 6 connecting the support holder 2 and the centrifugal motor 7, an injection system 10, and a thermocouple.

[0018] The apparatus further includes a shut-off lid 1-1 covering the central opening of the crucible 1. The injection system 10 includes an injection can 10-1, a laterally provided injection pipe 10-3, a transport pipe 10-2 connecting the injection can 10-1 and the injection pipe 10-3, and an auxiliary heating system 8 provided on the outer periphery of the injection can 10-1. The transport pipe 10-2 penetrates the shut-off lid 1-1, and the injection pipe 10-3 is provided inside the crucible 1.

[0019] The top of the injection system 10 is connected to a separable moving rod 15, and the moving rod 15 is connected to a driving device 17.

[0020] There are limiting devices that fit together at the bottom of the injection system 10 and the top of the shut-off lid 1-1.

[0021] In the present invention, the injection system 10 rotates synchronously with the crucible 1 and remains relatively stationary, avoiding the injection pipe 10-3 from stirring the melt inside the crucible 1.

[0022] The injection system 10 may be separately provided with a drive system that rotates synchronously with the crucible 1, and the shut-off lid 1-1 of the injection system 10 may be restricted.

[0023] In the present invention, a limiting device having a configuration in which a groove 14-2 is provided at the top of the shut-off lid 1-1 and a bump 14-1 is provided at a position corresponding to the bottom of the injection can 10-1 is used.

[0024] By fitting the groove and the bump, the injection system 10 is restricted by the shut-off lid 1-1. The shut-off lid 1-1 is firmly connected to the crucible 1 (by welding or the like), and the injection system 10 and the crucible 1 can rotate synchronously.

[0025] Due to centrifugal force, the pure indium in the crucible 1 is distributed on the side wall of the crucible 1. The outlet of the injection tube 10-3 is close to the side wall of the crucible 1, and the vicinity of the outlet, that is, the periphery of the injection region, is always in an indium-rich state. In this embodiment, the distance between the outlet of the injection tube 10-3 and the side wall of the crucible 1 is 1-5 mm.

[0026] In order to lift the injection system 10 from the melt after the synthesis is completed, in this embodiment, the injection tube 10-3 is provided horizontally or forms an angle of 1-5° downward with the horizontal direction at both ends. During the synthesis, when it is provided horizontally, if all the phosphorus vaporizes, the melt will enter the injection tube 10-3 and solidify in the injection tube 10-3 after cooling, resulting in waste of raw materials and the injection tube 10-3 cannot be reused. In this embodiment, both ends of the injection tube 10-3 form an angle of 1-5° downward with the horizontal direction. As shown in FIG. 6, when the injection system 10 is lifted from the melt, a small amount of melt inside the injection tube 10-3 flows out, and the above problem does not occur.

[0027] Based on the apparatus for producing indium phosphide crystals by the above vertical temperature gradient solidification, the present invention further proposes an embodiment of a method for producing indium phosphide crystals by vertical temperature gradient solidification including the following steps.

[0028] Step 1: Put the metal materials required for the synthesis into the crucible and put the non-metal volatile materials required for the synthesis into the injection device.

[0029] Step 1: Place the seed crystal 19 into the seed crystal tank 1-2 of the crucible 1, put the metallic indium 16 and boron oxide 5 into the crucible 1, put the red phosphorus 9 into the injection can 10-1. The cover plate on the upper part of the injection can 10-1 is separable. After putting the red phosphorus 9, weld it. Insert the injection tube 10-3 into the center of the cutoff lid 1-1, weld the injection tube 10-3 to the transport tube 10-2. After the welding bead is cooled, weld the upper edge of the crucible 1 to the cutoff lid 1-1 to assemble the device.

[0030] Place the crucible 1 into the crucible support holder 2, provide an auxiliary heating system 8 outside the injection can 10-1, connect a movable rod 15 separable from the injection system 10. The connection method may use a manipulator. Seal the furnace body.

[0031] Step 2: As shown in FIG. 1, fill the furnace body with an inert gas of 4.0 - 8.0 MPa to achieve a pressure protection effect.

[0032] Step 3: Separate the thermocouple B18-2 and the thermocouple C18-3. When the crucible 1 is placed and rotated, it will cause cutoff and damage. The multi-stage heater 3 heats the crucible 1 to 500 - 600 °C to melt the boron oxide 5 and the metallic indium 16. The drive device 17 drives the separable movable rod 15, places the injection system 10 on the cutoff lid 1-1, and the limiting device fits, that is, the bump 14-1 of the injection can 10-1 is embedded in the corresponding groove 14-2 at the top of the cutoff lid 1-1.

[0033] Leave the manipulator, and the separable movable rod 15 separates from the injection system 10.

[0034] At this time, in order to prevent phosphorus loss in the injection system 10 before injection synthesis, the heating temperature of the crucible 1 is low.

[0035] Step 4: Start the centrifugal motor 7 with a rotational speed of 500 - 5000 revolutions per minute to rotate the crucible 1 of the support rod 6. The separable moving rod 15 is separated from the injection system 10, and the thermocouple B18-2 and the thermocouple C18-3 are separated. Therefore, the rotation of the crucible 1 is not affected by external influences.

[0036] The molten indium metal is distributed on the inner wall of the crucible 1 and separated from the seed crystal 19, and the boron oxide 5 is distributed on the inner surface of the molten indium metal.

[0037] Step 5: The multi-stage heater 3 heats the crucible 1 to 30 - 200 °C higher than the melting point of indium phosphide. As shown in Figure 2, start the auxiliary heating system 8, heat the injection can 10-1 to 600 - 900 °C, sublime the red phosphorus 9 in the injection can 10-1, and the injection pipe 10-3 discharges the bubbles 11 and enters the molten metal 4 for centrifugal injection synthesis.

[0038] Gradually increase the power of the auxiliary heating system 8 to ensure that the injection pipe 10-3 stably discharges the bubbles 11. In order to ensure that the injection system 10 is not separated from the shielding lid 1-1, reinject the inert gas to increase the gas pressure inside the furnace body and outside the crucible 1, so that the external pressure of the crucible 1 can be made higher than the internal pressure.

[0039] Step 6: After the synthesis is completed, that is, after all the phosphorus has been gasified and injected, adjust the power of each stage heater of the multi-stage heater 3, set the temperatures of the thermocouple E18-5, the thermocouple A18-1, and the thermocouple D18-4 to 500 - 800 °C, solidify the synthesized indium phosphide into a cylindrical solid, make the boron oxide 5 liquid, and gradually reduce the rotational speed of the centrifugal motor 7 until it stops. The boron oxide 5 all flows to the bottom of the crucible 1. Refer to Figure 3.

[0040] The reason for lowering the temperature inside the crucible 1 to solidify the indium phosphide is that after the synthesis is completed, the temperature of the melt is high. At this time, if the rotation of the centrifugal motor 7 stops, the high-temperature melt will flow to the bottom of the crucible 1 and the seed crystal 19 will melt.

[0041] Step 7: As shown in FIG. 4, insert the thermocouples B18-2 and C18-3, adjust the power of each stage heater of the multi-stage heater 3, make the thermocouple E18-5 20 - 50 °C lower than the melting point of indium phosphide, and make the thermocouples A18-1 and D18-4 50 - 200 °C higher than the melting point of indium phosphide. The cylindrical solid indium phosphide remelts into a liquid and flows to the bottom of the crucible 1. Connect the separable moving rod 15 and the injection system 10, and lift the injection system 10 to separate it from the liquid level in the crucible 1.

[0042] The indium phosphide melt in the crucible 1 establishes a temperature gradient of 5 - 50 cm / °C, and the direction close to the seed crystal 19 is the low-temperature direction.

[0043] The bottom temperature of the seed crystal 19 is lower than the melting point of indium phosphide, and the melt of the synthesized indium phosphide is higher than the melting point. Finally, a part of the seed crystal 19 melts to establish an equilibrium state between the seed crystal 19 and the indium phosphide melt.

[0044] Step 8: As shown in FIG. 5, adjust the power of each stage heater of the multi-stage heater 3 to achieve the growth of indium phosphide single crystals. After the growth is completed, cool the system to room temperature, remove the crucible 1 from the crucible support holder 2, open the weld bead using a hydrogen-oxygen flame, remove and crush the crucible 1, then hold the injection system 10 and the shut-off lid 1-1 for next use, and take out the single crystal.

[0045] In step 6 of the above steps, the injection system (10) may solidify in the indium phosphide solid and damage the injection tube (10-3). Therefore, it is improved as follows.

[0046] Step 6: After the synthesis is completed, adjust the power of each stage heater of the multi-stage heater 3, raise the thermocouple E18-5 by 20 - 50 °C above the melting point of indium phosphide, raise the thermocouple A18-1 and the thermocouple D18-4 by 50 - 200 °C above the melting point of indium phosphide, and gradually reduce the rotational speed of the centrifugal motor 7 until it stops. The boron oxide 5 and the melt will all slowly flow to the bottom of the crucible 1.

[0047] The reduction rate of the rotational speed of the centrifugal motor 7 per minute is 10 - 100 revolutions. As shown in Figure 4, when the rotational speed of the centrifugal motor 7 drops to 0, connect the separable moving rod 15 to the injection system 10 and pull up the injection system 10 to separate it from the liquid level in the crucible 1.

[0048] Step 7: Insert the thermocouple B18-2 and the thermocouple C18-3, adjust the power of each stage heater of the multi-stage heater 3, and establish a temperature gradient of 5 - 50 cm / °C for the indium phosphide melt in the crucible 1. The direction close to the seed crystal 19 is the low-temperature direction.

[0049] There are two important points in the present invention. 1. In the synthesis stage of indium phosphide, the crucible rotates, the melt is separated by using centrifugal force, and gaseous phosphorus is injected into the side of the crucible. 2. In the single crystal growth stage, a temperature gradient in the vertical direction is established.

[0050] Also by experiments, using the apparatus and method proposed by the present invention, in the synthesis stage of indium phosphide, the synthesis rate increased by 20 - 30% compared with the conventional injection method, accelerating the production process of single crystals. To accelerate the synthesis rate and reduce melt contamination, the carrier concentration of indium phosphide is ≤ 2×10 15 cm -3 and the mobility is > 4500 cm 2 ·V -1 ·s -1 . When using the same raw materials, the carrier concentration of the conventionally synthesized polycrystals is > 5×10 15 cm -3 and the mobility is about 3000 - 4000 cm 2 ·V -1 ·s -1 .

Explanation of Symbols

[0051] 1: Crucible 1-1: Shut-off lid 2: Support holder 3: Multi-stage heater 4: Metal melt 5: Boron oxide 6: Support rod 7: Centrifugal motor 8: Auxiliary heating system 9: Red phosphorus 10: Injection system 10-1: Injection can 10-2: Transport pipe 10-3: Injection pipe 11: Bubble 14-1: Bump 14-2: Groove 15: Separable moving rod 16: Indium 17: Driving device 18-1, 18-2, 18-3, 18-4, 18-5: Thermocouple 19: Seed crystal 20: Indium phosphide single crystal.

Claims

1. An apparatus for producing indium phosphide crystals by vertical temperature gradient solidification, comprising a furnace body, a crucible (1) placed on a support holder (2), a seed crystal tank (1-2) provided at the bottom of the crucible (1), a multi-stage heater (3) on the outer periphery of the crucible (1), a motor, a support rod (6) connecting the support holder (2) and the motor, an injection system (10), and a thermocouple, wherein the motor is a centrifugal motor (7), the apparatus further comprises a cutoff lid (1-1) covering the central opening of the crucible (1), the injection system (10) comprises an injection can (10-1), a laterally provided injection pipe (10-3), a transport pipe (10-2) connecting the injection can (10-1) and the injection pipe (10-3), and an auxiliary heating system (8) provided on the outer periphery of the injection can (10-1), the transport pipe (10-2) penetrates the cutoff lid (1-1), and the injection pipe (10-3) is provided inside the crucible (1), the top of the injection system (10) is connected to a separable moving rod (15), and the moving rod (15) is connected to a driving device (17), characterized in that there are limiting devices fitting with each other at the bottom of the injection system (10) and the top of the cutoff lid (1-1), for an apparatus for producing indium phosphide crystals by vertical temperature gradient solidification.

2. The apparatus according to claim 1, characterized in that the outlet of the injection pipe (10-3) is close to the side wall of the crucible (1).

3. The apparatus according to claim 1, characterized in that 2-8 injection pipes (10-3) are uniformly provided, and are provided horizontally or at an angle of 1-5° with the horizontal direction.

4. As the limiting devices fitting with each other at the bottom of the injection system (10) and the top of the cutoff lid (1-1), a groove (14-2) is provided at the top of the cutoff lid (1-1), and a bump (14-1) is provided at a position corresponding to the bottom of the injection can (10-1), for the apparatus according to claim 1.

5. A method for producing indium phosphide crystals by vertical temperature gradient solidification, performed by the apparatus for producing indium phosphide crystals by vertical temperature gradient solidification according to any one of claims 1-4, comprising: Step 1 of putting a seed crystal (19) into the seed crystal tank (1-2) of the crucible (1), putting metallic indium (16) and boron oxide (5) into the crucible (1), putting red phosphorus (9) into the injection can (10-1), and assembling the apparatus; Step 2 of filling the furnace body with a pressure of 4.0-8.0 MPa for protection; The multi-stage heater (3) heats the crucible (1) to 500 - 600 °C to melt boron oxide (5) and metallic indium (16), the driving device (17) drives the separable moving rod (15), places the injection system (10) on the shielding lid (1-1), the limiting device fits, and the separable moving rod (15) separates from the injection system (10) in step 3; Start the centrifugal motor (7) with a rotation speed of 500 - 5000 revolutions per minute, and rotate the support rod (6) and the crucible (1) in step 4; The multi-stage heater (3) heats the crucible (1) 30 - 200 °C higher than the melting point of indium phosphide; Start the auxiliary heating system (8), heat the injection can (10-1) to 600 - 900 °C, sublime the red phosphorus (9) in the injection can (10-1), the injection pipe (10-3) discharges the gas into the metal melt (4) for centrifugal injection synthesis in step 5; After the synthesis is completed, adjust the power of each stage heater of the multi-stage heater (3), and set the temperatures of the thermocouple E (18-5), thermocouple A (18-1) and thermocouple D (18-4) to 500 - 800 °C, solidify the synthesized indium phosphide into a cylindrical solid, and turn boron oxide (5) into a liquid; Gradually reduce the rotation speed of the centrifugal motor (7) until it stops, so that boron oxide (5) all flows to the bottom of the crucible (1) in step 6; Insert the thermocouple B (18-2) and thermocouple C (18-3), adjust the power of each stage heater of the multi-stage heater (3), make the thermocouple E (18-5) 20 - 50 °C lower than the melting point of indium phosphide, make the thermocouple A (18-1) and thermocouple D (18-4) 50 - 200 °C higher than the melting point of indium phosphide, remelt the cylindrical solid indium phosphide into a liquid and let it flow to the bottom of the crucible (1), and pull up the injection system (10); Establish a temperature gradient of 5 - 50 cm / °C for the indium phosphide melt in the crucible (1), with the direction close to the seed crystal (19) being the low-temperature direction in step 7; Adjust the power of each stage heater of the multi-stage heater (3) to achieve indium phosphide single crystal growth. After the growth is completed, cool the system to room temperature and take out the single crystal in step 8. A method for manufacturing indium phosphide crystals by vertical temperature gradient solidification, characterized by including the above steps.

6. In step 6, after the synthesis is completed, adjust the power of each stage heater of the multi-stage heater (3), raise the thermocouple E (18-5) to 20-50 °C higher than the melting point of indium phosphide, raise the thermocouple A (18-1) and the thermocouple D (18-4) to 50-200 °C higher than the melting point of indium phosphide, gradually reduce the rotational speed of the centrifugal motor (7) until it stops, and let the boron oxide (5) and the melt slowly flow to the bottom of the crucible (1). After the centrifugal motor (7) stops, pull up the injection system (10). In step 7, insert the thermocouple B (18-2) and the thermocouple C (18-3), adjust the power of each stage heater of the multi-stage heater (3), and the indium phosphide melt in the crucible (1) establishes a temperature gradient of 5-50 cm / °C, and the direction close to the seed crystal 19 is the low-temperature direction. The method according to claim 5, characterized in that.

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