Crystal pulling furnace and method for efficiently adjusting oxygen concentration in crystal pulling furnace

Abstract

The invention provides a crystal pulling furnace and a method for efficiently adjusting oxygen concentration in the crystal pulling furnace, and the crystal pulling furnace comprises a main furnace chamber, an auxiliary furnace chamber, a crystal pulling head, a crucible, a vacuum system and a protective gas filling system; the silicon carbide rod heating assembly is fixedly arranged on the side wall of the main furnace chamber. The method comprises the steps that after a material is placed in a crucible and a cabin door of a main furnace chamber is closed, a vacuum system is controlled to work to conduct vacuum treatment on air in the main furnace chamber and an auxiliary furnace chamber; after vacuum treatment is completed, shielding gas is filled into the main furnace chamber and the auxiliary furnace chamber through a shielding gas filling system; the silicon carbide rod heating assembly is controlled to work in the shielding gas passing process. According to the crystal pulling furnace and the method for efficiently adjusting the oxygen concentration in the crystal pulling furnace, the oxygen concentration in the crystal pulling furnace can be efficiently adjusted.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal pulling technology, and in particular to a crystal pulling furnace and a method for efficiently adjusting the oxygen concentration in the crystal pulling furnace. Background Art

[0002] The manufacturing of chips starts with single crystal silicon; an important process for the production of single crystal silicon is crystal pulling; crystal pulling generally uses a crystal pulling furnace. A crystal pulling furnace is a device that heats and melts polycrystalline silicon and other materials in an inert gas environment and then uses the direct pulling method to grow single crystals; its working process mainly includes: batching, melting, crystal pulling, and finishing steps; during the crystal pulling process, effective control of oxygen content can ensure the quality of the crystal. How to achieve efficient regulation of the oxygen concentration in the crystal pulling furnace is a technical problem that needs to be solved urgently. Summary of the invention

[0003] One of the purposes of the present invention is to provide a crystal pulling furnace and a method for efficiently adjusting the oxygen concentration in the crystal pulling furnace, so as to achieve efficient adjustment of the oxygen concentration in the crystal pulling furnace.

[0004] A crystal pulling furnace provided in an embodiment of the present invention comprises: a main furnace chamber, an auxiliary furnace chamber, a crystal pulling head, a crucible, a vacuum system and a protective gas charging system; and further comprises:

[0005] The silicon carbide rod heating assembly is fixedly arranged on the side wall of the main furnace chamber.

[0006] Preferably, the silicon carbide rod heating assemblies are provided in plurality and are evenly distributed around the periphery of the crucible.

[0007] Preferably, the protective gas filling system includes: a gas storage device and a pressurized conveying device; wherein the gas storage device is used to store the protective gas, and the pressurized conveying device is used to pressurize the protective gas and input it into the first air inlet at the upper end of the attached furnace chamber.

[0008] Preferably, the vacuum system includes: a vacuum pump group, a vacuum chamber and a three-way electric control valve; wherein, one air inlet end of the three-way electric control valve is connected to a second air inlet port arranged at the lower end of the main furnace chamber, the other air inlet end is connected to a third air inlet port arranged at the upper end of the auxiliary furnace chamber, and the air outlet end is connected to the vacuum chamber; the vacuum pump group is connected to the vacuum chamber.

[0009] Preferably, the silicon carbide rod heating assembly comprises: a fixed structure and a main body; wherein one end of the fixed structure is fixedly connected to the side wall of the main furnace chamber, and the other end is fixedly connected to the main body;

[0010] An accommodating cavity is arranged inside the main body, and a blanking box is inserted at the bottom; a plurality of vents are opened on the upper end surface and the side surface; and connecting seats for silicon carbide rods are arranged at both ends of the accommodating cavity.

[0011] Preferably, the fixed structure is configured as a retractable structure.

[0012] Preferably, a plurality of air distribution plates are evenly distributed in the auxiliary furnace chamber below the first air inlet and the third air inlet; a through hole for allowing the crystal pulling head to pass through is provided in the middle of the air distribution plate.

[0013] Preferably, the crystal pulling furnace further includes: a purification and recovery module, which is connected to the vacuum chamber and is used for purifying and recovering the protective gas.

[0014] Preferably, the purification recovery module includes: a filtration unit, a deoxygenation unit, a drying unit and a denitrification unit which are arranged in sequence; wherein the filtration unit removes particulate impurities in the recovered gas; the deoxygenation unit is used to remove oxygen in the recovered gas by a catalytic oxidation process; the drying unit is used to remove water vapor in the recovered gas; and the denitrification unit is used to remove nitrogen in the recovered gas.

[0015] The present invention also provides a method for efficiently adjusting the oxygen concentration in a crystal pulling furnace, which is applied to any of the above-mentioned crystal pulling furnaces; comprising:

[0016] After placing the material into the crucible and closing the hatch of the main furnace chamber, the vacuum system is controlled to perform vacuum treatment on the air in the main furnace chamber and the auxiliary furnace chamber;

[0017] When the vacuum treatment is completed, the protective gas is filled into the main furnace chamber and the auxiliary furnace chamber through the protective gas filling system;

[0018] The operation of the silicon carbide rod heating assembly is controlled during the passage of the shielding gas.

[0019] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 Schematic diagram of a crystal pulling furnace according to an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of a silicon carbide rod heating assembly in an embodiment of the present invention;

[0024] Figure 3 Schematic diagram of the main body of the silicon carbide rod heating assembly in an embodiment of the present invention;

[0025] Figure 4 A method for efficiently adjusting the oxygen concentration in a crystal pulling furnace in an embodiment of the present invention;

[0026] Figure 5 is a schematic diagram of a main body of another silicon carbide rod heating assembly in an embodiment of the present invention;

[0027] Figure 6 It is a schematic diagram of the main body of another silicon carbide rod heating assembly in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0029] The embodiment of the present invention provides a crystal pulling furnace, such as Figures 1 to 3 As shown, it includes: a main furnace chamber 1, an auxiliary furnace chamber 2, a crystal pulling head 3, a crucible 4, a vacuum system 5 and a protective gas charging system 6; and also includes:

[0030] The silicon carbide rod heating assembly 7 is fixedly arranged on the side wall of the main furnace chamber 1 .

[0031] The silicon carbide rod heating assembly 7 is arranged in multiple pieces and evenly arranged on the periphery of the crucible 4. The silicon carbide rod is used in the furnace, which can react with oxygen to form silicon dioxide and carbon oxides, and these products will be discharged with the air flow, thereby reducing the concentration of oxygen;

[0032] Among them, the protective gas filling system 6 includes: a gas storage device and a pressurized conveying device; wherein, the gas storage device is used to store the protective gas, and the pressurized conveying device is used to pressurize the protective gas and input it into the first air inlet at the upper end of the auxiliary furnace chamber 2. A high-purity atmosphere is used in the crystal pulling process. Before starting the crystal pulling, the furnace body is first replaced with a high-purity inert gas such as argon to discharge the oxygen in the original air and create a low-oxygen environment; that is, the crystal pulling action is protected by charging the protective gas through the protective gas charging system 6; the protective gas includes: argon, etc.; by increasing the flow rate of the protective gas (such as an inert gas), the discharge rate of the oxygen-carrying molecules can be increased and the oxygen partial pressure can be reduced. The temperature of the growth chamber is precisely controlled so that the oxidation rate of the silicon melt surface matches the oxygen discharge rate to maintain a low-oxygen environment. Improve the structure of the furnace body and the heating system to reduce the penetration and accumulation of oxygen;

[0033] Among them, the vacuum system 5 includes: a vacuum pump group 53, a vacuum chamber 52 and a three-way electric control valve 51; among them, one air inlet end of the three-way electric control valve 51 is connected to the second air inlet arranged at the lower end of the main furnace chamber 1, the other air inlet end is connected to the third air inlet arranged at the upper end of the auxiliary furnace chamber 2, and the air outlet end is connected to the vacuum chamber 52; the vacuum pump group 53 is connected to the vacuum chamber 52.

[0034] The silicon carbide rod heating assembly 7 includes: a fixed structure 71 and a main body 72; wherein one end of the fixed structure 71 is fixedly connected to the side wall of the main furnace chamber 1, and the other end is fixedly connected to the main body 72;

[0035] The main body 72 is provided with a receiving cavity inside, and a blanking box 721 is inserted at the bottom; multiple ventilation holes are provided on the upper end surface and the side surface; and connecting seats 722 for silicon carbide rods 723 are provided at both ends of the receiving cavity. The connecting seats enable the silicon carbide rods to be connected to the circuit to achieve heating to a certain temperature; and then react with trace amounts of oxygen during the crystal pulling process;

[0036] The fixed structure 71 is configured as a retractable structure. The configuration of the retractable structure enables the silicon carbide heating assembly to be retracted to the inner wall side of the crystal pulling furnace when filling, and to be extended to the crucible 4 when entering the crystal pulling after filling, so as to facilitate operation and take into account the removal of trace oxygen at a close distance.

[0037] Among them, a plurality of air distribution plates are evenly arranged below the first air inlet and the third air inlet in the auxiliary furnace chamber 2; a through hole is provided in the middle of the air distribution plate for allowing the crystal pulling head 3 to pass through. The function of the air distribution plate is to evenly distribute the airflow, especially the airflow of the protective gas during the crystal pulling process.

[0038] Corresponding to the crystal pulling furnace in this embodiment, the present invention also provides a method for efficiently adjusting the oxygen concentration in the crystal pulling furnace, such as Figure 4 As shown, including:

[0039] Step 1: After placing the material into the crucible and closing the hatch of the main furnace chamber, control the vacuum system to vacuum the air in the main furnace chamber and the auxiliary furnace chamber;

[0040] Step 2: After the vacuum treatment is completed, the protective gas is filled into the main furnace chamber and the auxiliary furnace chamber through the protective gas filling system;

[0041] Step 3: Control the operation of the silicon carbide rod heating assembly during the passage of the shielding gas.

[0042] During vacuum treatment, the vacuum chamber is connected to the vacuum pump, and the three-way electric control valve simultaneously opens the connection between the second air inlet and the third air inlet and the vacuum chamber; vacuum exhaust is performed simultaneously from the upper part of the auxiliary furnace chamber and the lower part of the main furnace chamber, thereby improving the exhaust efficiency; the monitoring of the vacuum treatment can be achieved through a vacuum pressure gauge configured in the vacuum chamber; when the detection value of the vacuum pressure gauge drops to a pre-configured condition, it can be considered that the vacuum treatment is completed; after the vacuum treatment is completed, protective gas (argon) is filled into the space through the protective gas; since the fluidity of the protective gas needs to be maintained to ensure the increase in the discharge rate of the oxygen molecules carried and the reduction of oxygen The partial pressure can control the third air inlet of the three-way control valve to be connected with the vacuum chamber after a certain amount of protective gas is filled, so as to connect the vacuum chamber with the outside world to form an exhaust circuit; in the early stage of the protective gas filling, the third air inlet of the three-way control valve is controlled to be connected with the vacuum chamber, and the vacuum chamber is not connected with the outside world, and the pressure is detected by the air pressure detection unit arranged in the vacuum chamber; when the pressure reaches the preset pressure value, the vacuum chamber is controlled to be connected with the outside world; then the protective gas is continuously filled and the waste gas is discharged; when the vacuum chamber is connected with the outside world, the silicon carbide rod heating component is controlled to work to remove the trace oxygen in the space; and it continues to work during the crystal pulling process.

[0043] In one embodiment, a crystal pulling furnace comprises: a main furnace chamber, an auxiliary furnace chamber, a crystal pulling head, a crucible, a vacuum system, a protective gas charging system, a silicon carbide rod heating assembly and a purification recovery module; and further comprises:

[0044] The silicon carbide rod heating assembly is fixedly arranged on the side wall of the main furnace chamber; the purification recovery module is connected to the vacuum chamber and is used for purifying and recovering the protective gas.

[0045] The purification recovery module includes: a filter unit, a deoxygenation unit, a drying unit and a denitrification unit configured in sequence; wherein the filter unit removes particulate impurities in the recovered gas; the deoxygenation unit is used to remove oxygen in the recovered gas by a catalytic oxidation process; the drying unit is used to remove water vapor in the recovered gas; and the denitrification unit is used to remove nitrogen in the recovered gas. The filter unit can use an activated carbon filter unit to adsorb particulate impurities in the recovered gas; the deoxygenation unit uses a catalytic oxidation process to react the trace oxygen contained in the argon gas with the loaded MnO to generate MnO2, so that the oxygen content in the argon gas is less than 1ppm, and this process is called the oxygen absorption process. In order to achieve continuous operation, the filling container of the deoxygenation unit is set to at least two. When one of them is working, the other is regenerated by hydrogenation to restore its activity. This process is called the regeneration process. The drying unit can be configured as a dryer with a water-absorbing molecular sieve or other adsorbent material that preferentially adsorbs water. The denitrification unit uses a zirconium-aluminum alloy powder, which can adsorb other residual impurities in argon gas, including nitrogen, oxygen and water, at a high temperature of more than 250°C, preferably 250-800°C. Through this unit, the impurity content in argon gas is controlled within the allowable range. The protective gas is recovered, purified and reused through the recovery and purification module, reducing the loss of argon gas.

[0046] Corresponding to the crystal pulling furnace in this embodiment, the present invention also provides a method for efficiently adjusting the oxygen concentration in the crystal pulling furnace, comprising: after placing the material in the crucible and closing the hatch of the main furnace chamber, controlling the vacuum system to perform vacuum treatment on the air in the main furnace chamber and the auxiliary furnace chamber; when the vacuum treatment is completed, charging the main furnace chamber and the auxiliary furnace chamber with protective gas through the protective gas charging system; controlling the silicon carbide rod heating assembly to work during the passage of the protective gas; in the early stage of charging the protective gas, controlling the third air inlet of the three-way control valve to be connected with the vacuum chamber, the vacuum chamber is sealed, and the pressure is detected by the air pressure detection unit arranged in the vacuum chamber; when the pressure reaches a preset pressure value, controlling the vacuum chamber to be connected with the purification and recovery module; then continuously charging the protective gas, discharging the exhaust gas to the purification and recovery module, and charging the auxiliary furnace chamber and the main furnace chamber through the protective gas charging system after being processed by the purification and recovery module; when the vacuum chamber is connected to the external purification and recovery module, controlling the silicon carbide rod heating assembly to work to remove the trace oxygen in the space; and continuously working during the crystal pulling process.

[0047] Since silicon carbide rods are used to remove trace oxygen in the furnace, the removal effect gradually decreases with the increase of use time. How to reasonably configure the use of each silicon carbide rod can take into account both cost and removal effect; Figure 5 and Figure 6In one embodiment, a bristle brush 81 is provided on one side of the silicon carbide rod 723, and the two ends of the bristle brush 81 are respectively provided on a telescopic mechanism 82, and the telescopic mechanism 82 is operated to realize the contact between the bristle brush 81 and the silicon carbide rod 723; and the other end of the telescopic mechanism 82 is arranged on a rotating mechanism 83, and the rotating mechanism 83 drives the bristle brush 81 to rotate around the silicon carbide rod 723; to remove the surface layer after long-term use and improve the reaction effect; in order to avoid motion interference, the silicon carbide rod heating assembly 7 is provided with two symmetrically arranged fixed structures 71, and a rotating mechanism The middle part is fixedly connected to one end of a fixed structure 71; a method for efficiently adjusting the oxygen concentration in a crystal pulling furnace corresponding to this embodiment also includes: after the crystal pulling is completed or the material discharge is completed, the image of the silicon carbide rod is collected by an image acquisition module configured in the furnace; the state parameters of the filter unit of the purification recovery module are monitored by a state monitoring module; the collected image and state parameters are comprehensively analyzed to determine whether to start the rotating mechanism and the telescopic mechanism; when it is determined to be started, the telescopic mechanism is controlled to move the bristle brush close to the surface of the silicon carbide rod, and the rotating mechanism is rotated to perform surface treatment of the silicon carbide rod;

[0048] When controlling the contraction of the telescopic mechanism, it is necessary to analyze the corresponding contraction amount according to the situation to ensure accurate control, comprehensively judge the timing and the needs of precise control, and comprehensively analyze the collected images and state parameters. The specific analysis steps are as follows: recognize the image according to the pre-configured image recognition library to determine the sequence parameters of the corresponding configuration of the image; extract the features of the state parameters to obtain the feature parameters; arrange the sequence parameters and feature parameters in order to form an analysis set; match the analysis set with the standard set corresponding to each analysis result in the pre-configured analysis library, and extract the analysis results corresponding to the matched standard set; the analysis results include: whether it is triggered and the corresponding estimated value when triggered; through the estimated value, query the pre-configured estimated value and action difference correspondence table to determine the action difference; then combine the action value of the telescopic mechanism action last time to obtain the action value of the telescopic mechanism this time; among them, the image recognition library is configured in advance by professionals, based on the actual use of silicon carbide rods The images of each stage are used as standard images and corresponding sequence parameters are configured for them; the image recognition library essentially recognizes the image by matching the image collected by the current image acquisition module with the standard image in the library, and calling the sequence parameters configured corresponding to the matched standard image; the state parameters include: the gas flow rate and gas flow rate entering the purification and recovery module, the gas flow rate and gas flow rate flowing out of the filtration unit, the weight detection data of the filtered material of the filtration unit, etc.; the extracted feature parameters include: the parameters representing the gas flow rate entering the purification and recovery module, the parameters representing the gas flow rate entering the purification and recovery module, the parameters representing the gas flow rate flowing out of the filtration unit, the parameters representing the gas flow rate flowing out of the filtration unit, the parameters representing the weight detection data of the filtered material of the filtration unit, etc.; the analysis library is also analyzed and configured by professionals in advance, and the analysis results in the library are correspondingly associated with the standard set; the corresponding analysis results are called by matching the analysis set with the standard set.

[0049] Since the image device library and analysis library used in the above analysis are built in advance, the details in the actual application process are not well grasped and there are slight deviations. Therefore, it is necessary to analyze the actual situation and make subtle corrections to ensure the accuracy of the control of the telescopic mechanism. The specific correction steps are as follows: obtain the working condition data of the telescopic mechanism action time of the previous preset number of times and the interval time between two adjacent times of this action time; analyze the working condition data and build a correction analysis set; according to the correction analysis set, retrieve the corresponding correction value from the pre-configured correction library, and correct the action value according to the correction value; Among them, the working condition data includes: silicon carbide the first frame image after the surface treatment of the rod, the time and working mode of each process of the crystal pulling furnace when the crystal pulling furnace completes each crystal pulling task, the working time and working mode of the protective gas filling system of the crystal pulling furnace when the crystal pulling furnace completes each crystal pulling task, the working time and working mode of the vacuum system of the crystal pulling furnace when the crystal pulling furnace completes each crystal pulling task, the total duration corresponding to the working condition data, etc.; the steps of constructing the revised analysis set are as follows: identify the image according to the pre-configured image recognition library, and determine the sequence parameters of the corresponding configuration of the image; perform feature extraction on the working condition data to obtain the working condition parameters; arrange the sequence parameters and the working condition parameters in order to form a revised analysis set.

[0050] In addition, in order to facilitate the movement of the telescopic mechanism, the extension direction of the telescopic mechanism forms an angle of 30 to 60 degrees with the radius direction of the silicon carbide rod, and the diameter of the rotating mechanism is smaller than the diameter of the silicon carbide rod. The silicon carbide rod can be removed from an oblique direction, and the thickness of the removed rod can be controlled more easily.

[0051] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A crystal pulling furnace, comprising: The main furnace chamber, the auxiliary furnace chamber, the crystal pulling head, the crucible, the vacuum system and the protective gas charging system are characterized in that they also include: The silicon carbide rod heating assembly is fixedly arranged on the side wall of the main furnace chamber.

2. The crystal pulling furnace according to claim 1, characterized in that: The silicon carbide rod heating components are arranged in plurality and are evenly distributed on the periphery of the crucible.

3. The crystal pulling furnace according to claim 1, characterized in that: The protective gas filling system includes: a gas storage device and a pressurized conveying device; wherein the gas storage device is used to store the protective gas, and the pressurized conveying device is used to pressurize the protective gas and input it into the first air inlet at the upper end of the auxiliary furnace chamber.

4. The crystal pulling furnace according to claim 1, characterized in that: The vacuum system includes: a vacuum pump group, a vacuum chamber and a three-way electric control valve; wherein, one air inlet end of the three-way electric control valve is connected to the second air inlet port arranged at the lower end of the main furnace chamber, the other air inlet end is connected to the third air inlet port arranged at the upper end of the auxiliary furnace chamber, and the air outlet end is connected to the vacuum chamber; the vacuum pump group is connected to the vacuum chamber.

5. The crystal pulling furnace according to claim 1, characterized in that: The silicon carbide rod heating assembly comprises: a fixed structure and a main body; wherein one end of the fixed structure is fixedly connected to the side wall of the main furnace chamber, and the other end is fixedly connected to the main body; An accommodating cavity is arranged inside the main body, and a blanking box is inserted at the bottom; a plurality of vents are opened on the upper end surface and the side surface; and connecting seats for silicon carbide rods are arranged at both ends of the accommodating cavity.

6. The crystal pulling furnace according to claim 5, characterized in that: The fixed structure is configured as a retractable structure.

7. The crystal pulling furnace according to claim 5, characterized in that: A plurality of air distribution plates are evenly arranged in the auxiliary furnace chamber below the first air inlet and the third air inlet; a through hole for allowing a crystal pulling head to pass through is provided in the middle of the air distribution plate.

8. The crystal pulling furnace according to claim 5, characterized in that: Also includes: The purification and recovery module is connected to the vacuum chamber and is used for purifying and recovering the protective gas.

9. The crystal pulling furnace according to claim 8, characterized in that: The purification recovery module includes: a filtration unit, a deoxygenation unit, a drying unit and a denitrification unit which are arranged in sequence; wherein the filtration unit removes particulate impurities in the recovered gas; the deoxygenation unit is used to remove oxygen in the recovered gas by a catalytic oxidation process; the drying unit is used to remove water vapor in the recovered gas; and the denitrification unit is used to remove nitrogen in the recovered gas.

10. A method for efficiently adjusting the oxygen concentration in a crystal pulling furnace, applied to the crystal pulling furnace according to any one of claims 1 to 9; characterized in that: include: After placing the material into the crucible and closing the hatch of the main furnace chamber, the vacuum system is controlled to perform vacuum treatment on the air in the main furnace chamber and the auxiliary furnace chamber; When the vacuum treatment is completed, the protective gas is filled into the main furnace chamber and the auxiliary furnace chamber through the protective gas filling system; The operation of the silicon carbide rod heating assembly is controlled during the passage of the shielding gas.

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