In-situ detection device and method for growth state in liquid phase epitaxial growth of thin film process

Abstract

The application discloses an in-situ detection device and method for a growth state in a liquid phase epitaxial growth thin film process, and belongs to the field of liquid phase epitaxial thin film growth. The in-situ detection device comprises a rotating motor, a conductive slip ring, a ceramic rod, a heating pipe, a furnace body, a furnace shell, a noble metal rod, a support frame and a voltage measurement unit. The application monitors the mutation of a growth voltage signal from "empty connection" to "signal" in the process of substrate descending, obtains a contact surface of the substrate contacting a liquid surface as a coordinate zero point, and realizes calibration of the substrate contacting the liquid surface by forming a loop with the substrate, a liquid phase epitaxial growth solution and a crucible bottom. The conductive slip ring arranged on the ceramic rod stably leads out a growth voltage signal in a high-speed rotating state, so that complex solution convection, temperature fluctuation and interface behavior are mapped into an "voltage-time" characteristic curve which is easy to interpret.

Description

Technical Field

[0001] This invention belongs to the field of liquid phase epitaxial thin film growth, and specifically relates to an in-situ detection device and method for the growth state during liquid phase epitaxial thin film growth. Background Technology

[0002] Liquid phase epitaxy (LPE) is one of the important methods for preparing high-quality functional oxide thin films, especially in the fields of YIG ferromagnetic garnet magneto-optical thin films, III-V group material epitaxy, and high-temperature superconducting material epitaxy, playing an irreplaceable role. It has advantages such as high growth rate, low defect density, simultaneous doping with multiple elements, and the ability to grow large-size thin films. Traditional LPE processes typically use platinum or platinum alloy crucibles. A melt containing the main component oxide and flux is prepared in a certain proportion and placed in the crucible. The furnace is heated to maintain a certain temperature distribution and temperature gradient within the high-temperature furnace. After all the raw materials have melted, the crucible temperature is lowered to bring the solution to a supersaturated state. Then, a preheated single-crystal substrate is slowly immersed in the melt, and thin film epitaxial growth is achieved under controlled conditions of temperature, growth time, and substrate rotation speed. In actual production, the LPE process is highly dependent on experience for parameters such as temperature, time, and formulation. A mature LPE film growth process usually requires dozens or even hundreds of trials to explore growth parameters such as formulation, temperature, and rotation speed, resulting in immeasurable time, material, and labor costs.

[0003] In contrast, existing technologies offer limited guidance for LPE growth. Typically, they rely solely on thermocouples positioned within the furnace to monitor localized temperature changes, visually assessing the crucible's liquid level and substrate position through an observation window on the furnace top, and then characterizing the film thickness, surface morphology, structure, and magneto-optical properties using optical microscopy, X-ray diffraction, and vibrating sample magnetometers after growth. Process formulations and temperature parameters are then adjusted "afterwards" based on multiple rounds of repeated experiments. Clearly, this process optimization model, dominated by indirect observation, operational experience, and post-production characterization, has significant shortcomings: Firstly, relying solely on visual observation of the substrate's position in the solution through the top observation window introduces considerable error, making it impossible to accurately determine and control the substrate's position, thus introducing significant uncertainty into film growth. Secondly, crucial information such as the convection state and temperature distribution within the melt cannot be measured in real-time during growth, leaving the LPE growth process largely a "black box." Thirdly, improving film performance often depends on multi-furnace experiments and trial-and-error processes involving large quantities of substrates and raw materials, resulting in long optimization cycles, high costs, and difficulties in ensuring repeatability and stability between different batches. The fundamental reasons are as follows: the high temperature and highly corrosive molten environment makes it difficult for conventional sensors and probes to work stably for a long time, and there is a lack of online testing methods that can directly contact the molten metal; the traditional LPE furnace design does not reserve structural interfaces and electrode / insulation systems for multi-physics field detection and electrical measurement, making equipment modification difficult; the industry's long-standing process inertia of "temperature program + formulation experience + post-process characterization" lacks an in-situ characterization and closed-loop control system based on real-time data and physical models, and the process has long remained at a crude level of "only looking at temperature, not physical properties".

[0004] In summary, given the practical needs of LPE film growth and the limitations of existing technologies, there is an urgent need for a device that can operate stably in a high-temperature molten environment and can measure the substrate position and film growth state in situ during film growth. Summary of the Invention

[0005] The purpose of this invention is to address the technical challenge of lacking in-situ observation methods for substrate position and growth state during existing liquid-phase epitaxial thin film growth processes by providing a device and method for in-situ detection of growth state during epitaxial thin film growth. This invention's device can achieve real-time monitoring of substrate position and in-situ detection of thin film growth state through real-time measurement of growth electromotive force in a high-temperature solution environment.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An in-situ detection device for growth state during liquid phase epitaxial thin film growth includes a rotary motor 101, a conductive slip ring 102, a ceramic rod 103, a heating tube 104, a furnace body 105, a furnace shell 106, a precious metal rod 108, a support frame 112, and a voltage measurement unit.

[0008] The furnace body 105 is equipped with a rotary motor 101 at the top. The rotary motor 101 is connected to a precious metal support for mounting the substrate via a ceramic rod 103 and a precious metal rod 108. A conductive slip ring 102 is sleeved on the side of the ceramic rod 103 near the rotary motor 101.

[0009] A support frame 112 is provided at the bottom of the furnace body 105 to support a precious metal crucible containing a liquid phase epitaxial growth solution; a heating tube located inside the furnace shell is used to heat the liquid phase epitaxial growth solution.

[0010] One end of the voltage measurement unit is connected to the substrate surface via a conductive slip ring through a wire, and the other end is connected to the bottom of the noble metal crucible through a wire, for measuring the growth voltage signal.

[0011] Furthermore, the heating element is a multi-segment heating element.

[0012] Furthermore, the ceramic rod and the precious metal rod are connected by precious metal pins, threads, or snap fasteners.

[0013] Furthermore, the voltage measurement unit may be a voltmeter, a high internal resistance potentiometer, a nanovoltmeter, etc.

[0014] Furthermore, the conductive slip ring includes a high-temperature resistant insulating component 305, a rotating end 301, a stationary end 302, a conductive ring channel 303, and an elastic conductive contact 304. The high-temperature resistant insulating component is sleeved on the ceramic rod, the rotating end is located outside the high-temperature resistant insulating component, the stationary end is located outside the rotating end and is fixedly connected to the top of the furnace body, the elastic conductive contact is a protrusion set on the stationary end, and the conductive ring channel is a groove formed on the rotating end, serving as a rotating ring channel for the elastic conductive contact when the rotating end rotates.

[0015] Furthermore, the wires connected to the substrate surface are connected to the rotating end of the conductive slip ring, and the wires connected to the voltage measurement unit are connected to the stationary end of the conductive slip ring. When the rotating end rotates with the ceramic rod, the stationary end remains stationary, and the elastic conductive contacts are continuously pressed into the conductive ring channel, thereby forming a stable conductive path while the ceramic rod is continuously rotating, realizing the continuous transmission of the growth voltage signal from the rotating measurement end to the stationary measurement end.

[0016] Furthermore, the wires from the substrate to the conductive slip ring, the wires from the conductive slip ring to the voltage measurement unit, and the wires from the voltage measurement unit to the bottom of the precious metal crucible are all fitted with corundum tubes and shielded.

[0017] Preferably, the high-temperature resistant insulating component is made of Teflon.

[0018] A method for in-situ detection of growth state during liquid phase epitaxial thin film growth includes the following steps:

[0019] Step 1. Assemble the rotary motor, conductive slip ring, ceramic rod, heating tube, furnace body, furnace shell, and support frame according to the above device. Heat the furnace body and, after the raw material in the precious metal crucible melts, connect a precious metal stirrer to the ceramic rod to stir and obtain a uniform liquid phase epitaxial growth solution.

[0020] Step 2. Remove the precious metal stirrer, install the precious metal rod, connect the wires, and control the precious metal support carrying the substrate to descend using a rotary motor. Stop descending at the preheating position for preheating treatment. After preheating treatment, continue to descend the substrate. During the descent, observe the voltage signal measured by the voltage measurement unit in real time. When the voltage signal changes from no signal to a signal, it is determined that the substrate is in contact with the solution. Use the contact liquid surface as the coordinate zero point and control the substrate to continue descending until it reaches the preset position.

[0021] Step 3. Control the substrate to rotate at different speeds and in different directions, and record the voltage signals at different speeds and in different directions; analyze the growth state during the liquid phase epitaxial growth of the thin film based on the voltage signals.

[0022] Furthermore, step 3 involves analyzing the growth state during the liquid phase epitaxial film growth process based on the voltage signal using one of the following methods:

[0023] Method 1: Obtain the growth state based on the stability and vibration amplitude of the voltage signal curve; obtain the optimal growth state by adjusting the temperature, rotation speed, or substrate position.

[0024] Method 2: Obtain the growth state based on the root mean square of each voltage value on the voltage signal curve; obtain the optimal growth state by adjusting the temperature, rotation speed, or substrate position.

[0025] Furthermore, in step 3, when analyzing the growth state during the liquid phase epitaxial growth of the thin film based on the voltage signal, if the vibration amplitude of the voltage signal curve exceeds the preset amplitude threshold, or if the root mean square of each voltage value of the voltage signal curve is greater than the preset root mean square threshold, the detection is stopped, and the temperature, rotation speed, or substrate position is adjusted before re-detection.

[0026] Preferably, the more stable the voltage signal curve and the smaller the vibration amplitude, the better the growth status; the smaller the root mean square of each voltage value of the voltage signal curve, the better the growth status.

[0027] Furthermore, the sampling frequency of the voltage measurement unit is set to 10 Hz, and the collected signal is filtered to serve as the final growth voltage signal.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention provides an in-situ detection device for the growth state during liquid phase epitaxial thin film growth. By forming a circuit with the substrate, liquid phase epitaxial solution, and the bottom of the crucible, the device monitors the abrupt change in the growth voltage signal from "no connection" to "signal present" during the substrate's descent. This allows for the determination of the substrate's contact surface with the liquid, which serves as the zero point of the coordinate system, thus calibrating the substrate's contact surface and achieving precise positioning of the liquid phase epitaxial thin film growth location. Compared to existing methods that rely on experience to determine the liquid level and substrate position, this invention transforms the indirect estimation of the substrate position into a direct measurement driven by an electrical signal, significantly reducing substrate positioning errors and providing a reliable foundation for obtaining repeatable growth initiation conditions.

[0030] 2. This invention provides an in-situ detection device and method for the growth state during liquid-phase epitaxial thin film growth. By using a conductive slip ring mounted on a ceramic rod to stably extract the growth voltage signal under high-speed rotation, the complex solution convection, temperature fluctuations, and interfacial behavior are mapped into an easily interpretable voltage-time characteristic curve. Stable, controllable, and high-quality thin film growth corresponds to a laminar flow state with small fluctuations and large periods, and a stable temperature distribution with small fluctuations. Its voltage curve exhibits a smooth, wavy line with low amplitude and long periods. However, if there are formulation errors, convection instability, or deterioration of the growth state due to temperature fluctuations, significant disturbances will occur on the voltage curve. Based on this, this invention provides early warning through abnormal electrical signals before the thin film "grows badly," achieving in-situ detection of the growth state—something that traditional processes relying solely on post-process characterization cannot achieve.

[0031] 3. This invention provides an in-situ detection device and method for the growth state during liquid phase epitaxial thin film growth. The operator can observe changes in the voltage curve while adjusting the furnace temperature program, substrate rotation speed, and immersion depth. If unwanted oscillations are detected in the voltage signal, the growth parameters can be modified immediately, enabling the approximation of a suitable process window within a single furnace or even a few furnace experiments. Compared to the traditional empirical trial-and-error approach of "testing parameters in dozens or hundreds of furnaces," this invention significantly shortens the process development cycle, reduces substrate and raw material consumption, lowers time and economic costs, and significantly improves the consistency of thickness and performance between different batches of thin films.

[0032] 4. The present invention provides an in-situ detection device and method for growth state during liquid phase epitaxial thin film growth. The device has a simple structure, requires little modification to existing epitaxial furnaces, is applicable to a wide range of systems, and is easy to promote and apply in YIG and other oxide production lines, demonstrating significant innovation and engineering application value. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the liquid phase epitaxial furnace in the in-situ monitoring device for the growth state during the liquid phase epitaxial thin film growth process;

[0034] Figure 2 This is a schematic diagram of voltage signal measurement in an in-situ detection device for the growth state of liquid phase epitaxial thin films.

[0035] Figure 3 This is a schematic diagram of the conductive slip ring in the in-situ monitoring device for the growth state during liquid phase epitaxial thin film growth.

[0036] Figure 4 The voltage curves before and after the substrate in Example 1 comes into contact with the solution.

[0037] Figure 5 The voltage signal curve measured when the substrate was not rotated during growth in Example 2;

[0038] Figure 6 The voltage signal curve obtained by measuring the substrate of Example 2 during reverse growth at 20 r / min;

[0039] Figure 7 The voltage signal curve measured when the substrate of Example 3 was grown in reverse at 30 r / min is shown.

[0040] Figure 8 The voltage signal curve was measured when the substrate of Example 3 was grown in a forward rotation at 30 r / min.

[0041] Figure 9 The voltage signal curve obtained during the variable speed rotation process in Example 4 is shown.

[0042] Reference numerals: 101-Rotating motor, 102-Conductive slip ring, 103-Ceramic rod, 104-Heating tube, 105-Furnace body, 106-Furnace shell, 107-Precious metal pin, 108-Precious metal rod, 109-Substrate, 110-Precious metal crucible, 111-Liquid phase epitaxial growth solution, 112-Support frame, 201-Voltmeter, 301-Rotating end, 302-Stationary end, 303-Conductive ring, 304-Elastic conductive contact, 305-High temperature resistant insulating component, 307-Conductive slip ring input end, 308-Conductive slip ring output end. Detailed Implementation

[0043] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0044] The embodiment provides an in-situ detection device for the growth state during liquid phase epitaxial thin film growth, wherein the structure of the liquid phase epitaxial furnace is as follows: Figure 1 As shown in the diagram, the voltage signal measurement schematic is as follows: Figure 2 As shown; the detection device includes a rotary motor 101, a conductive slip ring 102, a ceramic rod 103, a heating tube 104, a furnace body 105, a furnace shell 106, a precious metal pin 107, a precious metal rod 108, a support frame 112, and a voltmeter 201.

[0045] The furnace body 105 is equipped with a rotary motor 101 at the top. The rotary motor 101 is connected to a precious metal support for mounting the substrate 109 via a ceramic rod 103 and a precious metal rod 108. The ceramic rod 103 and the precious metal rod 108 are connected by a precious metal pin 107. A conductive slip ring 102 is sleeved on the side of the ceramic rod 103 near the rotary motor 101.

[0046] A support frame 112 is provided at the bottom of the furnace body 105 to support the precious metal crucible 110 containing the liquid phase epitaxial growth solution 111; the heating tube located inside the furnace shell is used to heat the liquid phase epitaxial growth solution and is located on the outside of the precious metal crucible, the precious metal rod, and part of the ceramic rod.

[0047] One end of the voltmeter 201 is connected to the surface of the substrate 109 via a noble metal wire and a conductive slip ring as the positive electrode, and the other end is connected to the bottom of the noble metal crucible via a noble metal wire as the negative electrode. It is used to collect the growth voltage signal between the grown crystal film and the growth solution.

[0048] Furthermore, the heating element is a multi-segment heating element to achieve segmented temperature control.

[0049] Furthermore, the structural schematic diagram of the conductive slip ring is as follows: Figure 3 As shown, it includes a high-temperature resistant insulating component 305, a rotating end 301, a stationary end 302, a conductive ring 303, and an elastic conductive contact 304. The high-temperature resistant insulating component is sleeved on the ceramic rod 103, the rotating end is in close contact with the high-temperature resistant insulating component, the stationary end is located outside the rotating end and is fixedly connected to the top of the furnace body, the elastic conductive contact is a protrusion set on the stationary end, and the conductive ring is a groove formed on the rotating end, which serves as the rotating ring of the elastic conductive contact when the rotating end rotates.

[0050] Furthermore, a noble metal wire connected to the substrate surface is connected to the rotating end of the conductive slip ring as the input end 307, and a noble metal wire connected to the voltmeter is connected to the stationary end of the conductive slip ring as the output end 308. When the rotating end rotates with the ceramic rod, the stationary end remains stationary, and the elastic conductive contact continuously presses against the conductive ring channel, thus forming a stable conductive path during continuous rotation of the ceramic rod, enabling continuous transmission of the growth voltage signal from the rotating measuring end (input) to the stationary measuring end (output). Since the rotating end of the conductive slip ring is connected to the rotating substrate, and the stationary end is connected to the voltmeter, the wire connected to the voltmeter will not rotate with the ceramic rod when it rotates at high speed, thus achieving stable signal transmission.

[0051] Preferably, the wires from the substrate to the conductive slip ring, the wires from the conductive slip ring to the voltmeter, and the wires from the voltmeter to the bottom of the precious metal crucible are all insulated with corundum tubes and supplemented with shielding layers to reduce leakage current, thermal noise and external electromagnetic interference, thereby realizing in-situ measurement and stable extraction of growth voltage signals under high-temperature rotation conditions.

[0052] Preferably, the high-temperature resistant insulating component is made of Teflon, with an inner diameter of 15mm, an outer diameter of 30mm, and a height of 50mm.

[0053] A method for in-situ detection of growth state during liquid phase epitaxial thin film growth includes the following steps:

[0054] Step 1. Assemble the rotary motor, conductive slip ring, ceramic rod, heating tube, furnace body, furnace shell, support frame, and voltmeter according to the above device, and perform LPE film growth operation. Heat the furnace body and wait for all the raw materials in the precious metal crucible to melt. Connect the ceramic rod to the precious metal stirrer through the pin, and then lower the precious metal stirrer into the molten solution. Rotate and stir for 6-12 hours to obtain a uniform liquid phase epitaxial growth solution.

[0055] Step 2. Remove the precious metal stirrer, install the precious metal rod, connect the wires, and control the precious metal support with the substrate to descend using a rotary motor. Descend to a position 10-20 mm above the liquid surface and preheat for 30 minutes. Then continue to descend the substrate. During the descent, observe the voltage signal measured by the voltmeter in real time. When the voltage signal changes from no signal to a signal, it is determined that the substrate is in contact with the solution. The contact liquid surface between the substrate and the solution is obtained. Using this contact liquid surface as the zero point of the coordinate system, control the substrate to continue descending until it reaches the preset position.

[0056] Step 3. Control the substrate to rotate forward or backward at different speeds, and record the voltage signals at different speeds and rotation directions; analyze the growth state during the liquid phase epitaxial growth of the thin film based on the voltage signals.

[0057] Furthermore, for a stable, controllable, and high-quality growth state, the solution convection should be a laminar flow with small fluctuations and a relatively large period, the temperature distribution should be a stable value with small fluctuations and a relatively large period, and the corresponding voltage curve should be a wavy line with stable signal value, low vibration amplitude, and large period. That is, the root mean square of the measured voltage signal should be as small as possible. Based on this, the growth state of the LPE film can be judged. If the growth state is not good, it can be adjusted by changing the temperature, rotation speed, and substrate position to achieve growth optimization.

[0058] Preferably, during the substrate descent process, once the substrate contacts the solution, the voltmeter will switch from no connection to signal connection. At this time, the substrate is in contact with the liquid surface, and the substrate is the zero point of the coordinate system relative to the solution, thus obtaining a precise zero point of the coordinate system, thereby enabling precise control of the substrate position.

[0059] Preferably, in order to obtain a more accurate and sensitive voltage signal, the sampling frequency of the voltmeter is set to 10 Hz, and the acquired growth voltage signal is filtered and used as the final voltage signal.

[0060] Taking liquid phase epitaxial growth of YIG thin films as an example, this invention introduces how to precisely control the substrate position and detect the film growth state in situ during the LP thin film growth process.

[0061] Example 1

[0062] Platinum wire was used as the conductor, with the positive electrode connected to the surface of the platinum substrate and the negative electrode connected to the bottom of the platinum crucible. The growth voltage signal was recorded throughout the growth process using a voltmeter. The prepared raw material was placed in the platinum crucible and placed in an epitaxial furnace. After the furnace was heated until the raw material was fully melted, a platinum stirrer was installed and lowered into the solution. The mixture was stirred at a speed of 70 r / min and a forward and reverse cycle of 2000 s for 6 hours.

[0063] After stirring, remove the platinum stirrer and replace it with a platinum support with the substrate mounted. Then, rapidly lower the platinum support at a speed of 30 mm / min to a position 10-20 mm above the solution and preheat for half an hour. Next, slowly lower the platinum support at a speed of 1 mm / min, observing the voltmeter reading in real time. Figure 4 As shown in the diagram, when the voltage signal curve suddenly exhibits a step change, it indicates that the substrate has come into contact with the solution. At this point, the descent of the support is immediately stopped, and the distance the motor has descended at this moment is recorded as 650 mm. This point is the zero point of substrate-solution contact, thus achieving the calibration of the substrate contact liquid surface. The support is then lowered by another 5 mm to 655 mm, thereby achieving precise positioning of the liquid phase epitaxial film growth position.

[0064] Example 2

[0065] Platinum wire was used as the conductor, with the positive electrode connected to the surface of the platinum substrate and the negative electrode connected to the bottom of the platinum crucible. The growth voltage signal was recorded throughout the growth process using a voltmeter. The prepared raw material was placed in the platinum crucible and placed in an epitaxial furnace. After the furnace was heated until the raw material was fully melted, a platinum stirrer was installed and lowered into the solution. The mixture was stirred at a speed of 80 r / min and a forward and reverse cycle of 2000 s for 8 hours.

[0066] After stirring, remove the platinum stirrer and replace it with a platinum support with the substrate mounted on it. Then, rapidly lower the platinum support at a speed of 25 mm / min to a position 10-20 mm above the solution for preheating for half an hour. Next, slowly lower the support at a speed of 1 mm / min, observing the voltmeter reading in real time. When the voltage signal curve suddenly shows a step change, it indicates that the substrate has made contact with the solution. At this point, immediately stop lowering the support and record the distance the motor has descended at 650 mm. This point is the zero point of substrate-solution contact, thus calibrating the substrate contact surface. Continue lowering the support by 5 mm to 655 mm to begin thin film epitaxial growth.

[0067] The substrate is not rotated and is simply placed statically in the solution; the voltage signal curve measured under these conditions is as follows. Figure 5 As shown in the figure, the voltage signal fluctuation amplitude is large at this point, reaching approximately 200 microvolts, with a period of about 20 seconds. The temperature gradient of the entire solution temperature field shows an increasing trend, indicating unfavorable conditions for film growth. Subsequently, growth was performed by reversing the rotation at 20 r / min, and the measured voltage signal curve is shown in the figure. Figure 6 As shown, the amplitude of the voltage curve is significantly suppressed, the period becomes more regular, and the voltage signal changes less within the same time range. This indicates that the temperature gradient change in the entire temperature field is reduced, and the temperature field becomes more stable. Clearly, rotation effectively improves the temperature field and flow of the solution, optimizing the film growth conditions.

[0068] Example 3

[0069] Platinum wire was used as the conductor, with the positive electrode connected to the surface of the platinum substrate and the negative electrode connected to the bottom of the platinum crucible. The growth voltage signal was recorded throughout the growth process using a voltmeter. The prepared raw material was placed in the platinum crucible and placed in an epitaxial furnace. After the furnace was heated until the raw material was fully melted, a platinum stirrer was installed and lowered into the solution. The mixture was stirred at 80 r / min with a forward and reverse rotation cycle of 2000 s for 10 hours.

[0070] After stirring, remove the platinum stirrer and replace it with a platinum support with the substrate mounted on it. Then, rapidly lower the platinum support at 35 mm / min to a position 10-20 mm above the solution for preheating for half an hour. Next, slowly lower the support at 1 mm / min, observing the voltmeter reading in real time. When the voltage signal curve suddenly shows a step change, it indicates that the substrate has made contact with the solution. At this point, immediately stop lowering the support and record the distance the motor has descended at 650 mm. This point is the zero point of substrate-solution contact, thus calibrating the substrate contact surface. Continue lowering the support by 8 mm to 658 mm to begin thin film epitaxial growth.

[0071] Thin film growth was performed at 30 r / min for 3 min with reverse rotation, and the measured voltage signal curve is shown below. Figure 7 As shown; thin film growth was performed at 30 r / min forward for 3 min, and the measured voltage signal curve is shown below. Figure 8 As shown in the figure, the voltage value of the reverse voltage curve is significantly lower than that of the forward voltage curve, and the oscillation amplitude is also slightly lower. Within the same time range, the voltage change value of the reverse curve is also significantly lower than that of the forward curve. This indicates that under this solution system and temperature field setting, reverse rotation is more conducive to stabilizing solution convection and maintaining a stable temperature gradient. Therefore, in actual growth, reverse rotation should be given priority.

[0072] Example 4

[0073] Platinum wire was used as the conductor, with the positive electrode connected to the surface of the platinum substrate and the negative electrode connected to the bottom of the platinum crucible. The growth voltage signal was recorded throughout the growth process using a voltmeter. The prepared raw material was placed in the platinum crucible and placed in an epitaxial furnace. After the furnace was heated until the raw material was fully melted, a platinum stirrer was installed and lowered into the solution. The mixture was stirred at a speed of 70 r / min and a forward and reverse cycle of 2000 s for 6 hours.

[0074] After stirring, remove the platinum stirrer and replace it with a platinum support with the substrate mounted on it. Then, rapidly lower the platinum support at a speed of 40 mm / min to a position 10-20 mm above the solution for preheating for half an hour. Next, slowly lower the support at a speed of 1 mm / min, observing the voltmeter reading in real time. When the voltage signal curve suddenly shows a step change, it indicates that the substrate has made contact with the solution. At this point, immediately stop lowering the support and record the distance the motor has descended at 650 mm. This point is the zero point of substrate-solution contact, thus calibrating the substrate contact surface. Continue lowering the support by 10 mm to 660 mm to begin thin film epitaxial growth.

[0075] A variable-speed rotation program is set with a rotation cycle of 60 r / min forward for 5 min – stop for 5 min – 60 r / min reverse for 5 min – stop for 5 min – 60 r / min for 6 seconds, and a rotation cycle of forward and reverse for 5 min – stop for 5 min – 100 r / min forward for 5 min – stop for 5 min – 100 r / min reverse for 5 min – stop for 5 min – 100 r / min for 6 seconds, and a rotation cycle of forward and reverse for 5 min – stop. The voltage signal curve measured throughout the entire process is shown in the figure. Figure 9 As shown in the figure, rotation can effectively suppress voltage signal fluctuations and greatly reduce the solution temperature gradient, thereby maintaining the stability of the entire flow field and temperature field. The root mean square (RMS) of the voltage signals measured under different rotation conditions is shown in Table 1. Table 1 shows that both forward and reverse rotation have a better stabilizing effect on the voltage signal. However, under the current solution system and temperature field settings, the RMS of the voltage signal is smallest at 100 rpm reverse rotation. At this speed, the voltage signal is within a stable value range with relatively small oscillations. This indicates that the flow field and temperature field of the epitaxial film growth are in a stable and controllable equilibrium state, resulting in higher uniformity and lower surface defect density of the epitaxial film. Therefore, based on this invention, the changes in the flow field and temperature field during liquid-phase epitaxial film growth can be visualized in situ. Suitable growth parameters can be quickly located under different growth systems and environments, thereby greatly accelerating the process exploration and better optimizing film quality.

[0076] Table 1. Root mean square values ​​of voltage signal curves measured under different rotation conditions.

[0077]

Claims

1. An in-situ detection device for the growth state during liquid phase epitaxial thin film growth, characterized in that, It includes a rotary motor (101), a conductive slip ring (102), a ceramic rod (103), a heating tube (104), a furnace body (105), a furnace shell (106), a precious metal rod (108), a support frame (112), and a voltage measurement unit; The furnace body is equipped with a rotary motor at the top, which is connected to a precious metal support for mounting the substrate via a ceramic rod and a precious metal rod; a conductive slip ring is sleeved on the side of the ceramic rod closest to the rotary motor. A support frame is installed at the bottom of the furnace body to support the precious metal crucible containing the liquid phase epitaxial growth solution; heating tubes located inside the furnace shell are used to heat the liquid phase epitaxial growth solution; One end of the voltage measurement unit is connected to the substrate surface via a conductive slip ring through a wire, and the other end is connected to the bottom of the noble metal crucible through a wire, for measuring the growth voltage signal.

2. The in-situ detection device for growth state during liquid phase epitaxial thin film growth according to claim 1, characterized in that, The heating element is a multi-segment heating element.

3. The in-situ detection device for growth state during liquid phase epitaxial thin film growth according to claim 1, characterized in that, The ceramic rod and the precious metal rod are connected by precious metal pins, threads, or snap fasteners.

4. The in-situ detection device for growth state during liquid phase epitaxial thin film growth according to claim 1, characterized in that, The voltage measurement unit is a voltmeter, a high internal resistance potentiometer, or a nanovoltmeter.

5. The in-situ detection device for growth state during liquid phase epitaxial thin film growth according to claim 1, characterized in that, The conductive slip ring includes a high-temperature resistant insulating component (305), a rotating end (301), a stationary end (302), a conductive ring channel (303), and an elastic conductive contact (304). The high-temperature resistant insulating component is sleeved on the ceramic rod. The rotating end is located outside the high-temperature resistant insulating component. The stationary end is located outside the rotating end and is fixedly connected to the top of the furnace body. The elastic conductive contact is a protrusion set on the stationary end. The conductive ring channel is a groove formed on the rotating end and serves as a rotating ring channel for the elastic conductive contact when the rotating end rotates.

6. The in-situ detection device for growth state during liquid phase epitaxial thin film growth according to claim 1, characterized in that, The wires connected to the substrate surface are connected to the rotating end of the conductive slip ring, and the wires connected to the voltage measurement unit are connected to the stationary end of the conductive slip ring.

7. The in-situ detection device for growth state during liquid phase epitaxial thin film growth according to claim 5, characterized in that, The high-temperature resistant insulating component is made of Teflon.

8. A method for in-situ detection of the growth state during liquid phase epitaxial thin film growth, characterized in that, Includes the following steps: Step 1. Assemble the rotary motor, conductive slip ring, ceramic rod, heating tube, furnace body, furnace shell and support frame in the device according to any one of claims 1-7. Heat the furnace body. After the raw material in the precious metal crucible melts, connect a precious metal stirrer to the ceramic rod and stir to obtain a uniform liquid phase epitaxial growth solution. Step 2. Remove the precious metal stirrer, install the precious metal rod, connect the wires, and control the precious metal support carrying the substrate to descend using a rotary motor. Stop when it reaches the preheating position for preheating. After preheating, continue to descend the substrate. During the descent, observe the voltage signal measured by the voltage measurement unit in real time. When the voltage signal changes from no signal to a signal, it is determined that the substrate is in contact with the solution. The contact liquid surface is used as the zero point of the coordinate system to control the substrate to continue descending until it reaches the preset position. Step 3. Control the substrate to rotate at different speeds and in different directions, and record the voltage signals at different speeds and in different directions; analyze the growth state during the liquid phase epitaxial growth of the thin film based on the voltage signals.

9. The method for in-situ detection of growth state during liquid phase epitaxial thin film growth according to claim 8, characterized in that, Step 3: Analyze the growth state during the liquid phase epitaxial film growth process based on the voltage signal using one of the following methods: Method 1: Obtain the growth state based on the stability and vibration amplitude of the voltage signal curve; obtain the optimal growth state by adjusting the temperature, rotation speed, or substrate position. Method 2: Obtain the growth state based on the root mean square of each voltage value on the voltage signal curve; obtain the optimal growth state by adjusting the temperature, rotation speed, or substrate position.

10. The method for in-situ detection of growth state during liquid phase epitaxial thin film growth according to claim 8, characterized in that, Step 3: When analyzing the growth state of the liquid phase epitaxial thin film based on the voltage signal, if the vibration amplitude of the voltage signal curve exceeds the preset amplitude threshold, or if the root mean square of each voltage value of the voltage signal curve is greater than the preset root mean square threshold, stop the detection, adjust the temperature, rotation speed, or substrate position, and re-detect.

Images