TW202221175A - Method for detection liquid level and preparation method of single crystal - Google Patents

Abstract

The present application provides a method for detecting liquid level and a preparation method of single crystal. The method for detecting liquid level is to detect liquid level of a melt within a crystal-pulling apparatus, and comprises the following steps: disposing a detector above the liquid surface of the melt, obtaining data of a first distance between the detector and the liquid surface of the melt, and obtaining the liquid level data between the melt surface and the reflector based on the first distance data to obtain a distance of the melt gap. Accordingly, the detector does not contact the melt surface and does not cause contamination during the crystal growth. The detector is able to detect the liquid level of the melt in different areas because it can be disposed with various height. Advantages of the method of the present application include the boarder scope of detection, high flexibility, real-time detection, enhancement of quality of the single crystal, non-use of target materials and reduction of cost.

Description

Liquid level measurement method and single crystal pulling method

The present invention relates to the technical field of crystal preparation, in particular to a liquid level measurement method and a single crystal pulling method.

The manufacturing methods of single crystal silicon mainly include zone melting method and Czochralski method. In the prior art, the Czochralski method (CZ method, also known as Czochralski method) is usually used to prepare single crystal silicon. The CZ method is to store the polysilicon raw material in a quartz crucible set in the hearth of the crystal pulling furnace, heat and melt it by a graphite heater, and then put a rod-shaped seed (commonly called seed crystal) with a diameter of only 10 millimeters (mm) with a The polycrystalline silicon melt is in contact with the liquid surface. At the appropriate temperature required by the process, the silicon atoms in the melt will form regular crystals at the solid-liquid interface along the silicon atomic arrangement of the seed crystal, and become a single crystal. Rotate the seed crystal while While pulling, the silicon atoms in the melt will continue to crystallize on the single crystal formed earlier, and continue its regular atomic arrangement structure, and the crucible seed crystal will be lifted at the same time to produce a single crystal silicon rod with the target diameter and quality.

During the preparation of silicon single crystals, when large-sized silicon single crystals are prepared by the Czochralski method using a crystal pulling furnace, the melt in the crucible will gradually be consumed as the crystal length continues to increase. 1 , the crystal pulling furnace includes a crucible 10 , a guide tube 30 , a magnet system 50 , a heater 60 , graphite 70 and a graphite felt 80 . was pulled out. In order to ensure the stability of the crystal growth interface, the position of the crucible 10 must be continuously raised, so that the position of the solid-liquid interface during the crystal growth process is always fixed at the same position, that is, it is necessary to ensure that the liquid level 21 of the melt reaches the guide tube of the guide tube 30 The distance of the bottom 31 remains unchanged, which is beneficial to efficiently and stably control the temperature distribution of the thermal field. Accordingly, the distance from the liquid level 21 of the melt to the bottom 31 of the guide cylinder is defined as a melt gap (Melt Gap) 40 . Precisely controlling the melt gap 40 in the crystal growth process is a key factor to control the crystal quality and ensure the repeatability of the process. Usually, feedback adjustment is used to control the liquid level 21 of the melt (hereinafter referred to as the liquid level) to the bottom 31 of the guide tube The detection of the liquid level position is the core signal input for feedback adjustment, which is the key to accurately control the distance from the liquid level 21 of the melt to the bottom 31 of the guide tube. Therefore, the measurement of the liquid level position is used in the process of silicon single crystal preparation. crucial in.

At present, the widely used liquid level detection methods are: quartz pin method and reflection method.

The quartz pin method is to fix a high-purity quartz pin at the bottom of the guide tube, raise the crucible to make the liquid surface contact the quartz pin before crystal growth, and adjust the crucible position to reach the set liquid level with the liquid surface contacting the quartz pin as the starting point. However, in this method, the feedback information of the liquid surface position cannot be obtained immediately during the crystal growth process, and the temperature distribution of the thermal field cannot be accurately controlled, thus the quality of the silicon single crystal during the crystal growth process cannot be guaranteed.

The reflection method is to fix a target point at the bottom of the guide tube, and capture the reflection of the target point on the liquid surface through a charge-coupled device (CCD) camera to obtain the liquid surface distance. surface information. However, the target material selected by this method needs to meet the characteristics of high contrast of high-purity quartz and graphite materials at high temperature at the same time, and this method has high requirements on the thermal field structure and liquid surface distance, and cannot be used beyond a certain range.

Therefore, in the process of preparing crystals from the melt, especially in the process of preparing large-sized semiconductor silicon single crystals, a liquid level measurement method that can obtain liquid level information in real time and does not use target materials is developed, thereby improving the performance of single crystals. Quality and cost reduction have become urgent problems to be solved in the field of melt preparation of crystals.

The purpose of the present invention is to provide a liquid level measurement method and a single crystal pulling method, so as to solve the problem that the liquid level position information cannot be obtained in real time in the existing liquid level measurement method, the target material needs to be selected, the contrast requirement of the target material is high, and the cost is high. The problem.

In order to solve the above-mentioned technical problems, the present invention provides a liquid level measurement method for detecting liquid level information of a melt in a crystal pulling device. The crystal pulling device includes a furnace body, a crucible, a guide tube and a detector. The crucible is arranged in the furnace body and is used for accommodating the melt, the guide tube is arranged in the furnace body and is located above the crucible, and the flow guide tube is connected to the melt level of the melt. There is a melting gap therebetween, and the liquid level measurement method includes the following steps: configuring a detector to be disposed above the melt liquid level of the melt; using the detector to obtain the melt liquid level to the information of the first distance of the detector; and, based on the information of the first distance, obtain the information of the melt level from the melt level to the guide cylinder to obtain the distance of the melt gap.

In one embodiment, before the step of obtaining the melt level information from the melt level to the guide tube based on the information of the first distance to obtain the distance from the melt gap, the liquid level is The measuring method further includes: determining a second distance from the guide tube to the detector, wherein the second distance is smaller than the first distance.

In one embodiment, the step of obtaining the melt level information from the melt level to the guide tube based on the information of the first distance, and obtaining the distance of the melt gap includes: M=L-h Wherein, M represents the distance of the fusion gap, L represents the first distance, and h represents the second distance.

In one embodiment, a crystal is pulled out from the center of the melt level, and the distance between the detector and the central axis of the crystal is between 150 and 400 millimeters (mm).

In one embodiment, the detector obtains the information of the first distance through a return signal of an electromagnetic wave, or the detector is a laser radar.

In one embodiment, the accuracy of the distance detected by the detector is within 0.1 mm.

In one embodiment, a viewing window is opened on the top of the furnace body, and the detector is configured to be disposed at the viewing window.

In order to solve the above technical problems, the present invention also provides a method for pulling a single crystal, and the method for pulling a single crystal includes the following steps: using the liquid level measurement method as described above to obtain the melt level information of the melt; and, according to The melt level information adjusts the position of the crucible.

In one embodiment, the crystal pulling apparatus includes a controller, and the step of adjusting the position of the crucible according to the melt level information includes: the controller receives the melt level information fed back by the detector, and adjusts the position of the crucible. the location of the crucible.

In one embodiment, the step of adjusting the position of the crucible according to the melt level information further includes: presetting standard liquid level information of the controller; Compare the level information with the standard level information; if the melt level information is less than the standard level information, execute the crucible lowering command; if the melt level information is greater than the standard level information, execute all The command for the crucible to rise; if the melt level information is equal to the standard level information, the command is not executed.

The liquid level measurement method provided by the present invention is used to detect the liquid level information of the melt in the crystal pulling equipment. The crystal pulling equipment includes a furnace body, a crucible, a guide tube and a detector, and the crucible is arranged in the furnace body. It is used for accommodating the melt, the guide tube is arranged in the furnace body and is located above the crucible, and there is a melting gap between the guide tube and the melt level of the melt, so The liquid level measurement method includes the following steps: configuring a detector to be disposed above the melt level of the melt; using the detector to obtain a first distance from the melt level to the detector information; and, based on the information of the first distance, obtain the information of the melt level from the melt level to the guide cylinder, and obtain the distance of the melt gap. In this way, the detector and the melt level are in a non-contact form, which will not bring pollution during the crystal growth process. Different heights can be set, the melt level is not limited, the range of melt level that can be measured is large, and the melt level information can be obtained in real time, improving the quality of single crystals, avoiding the use of target materials, and reducing costs.

In order to make the objects, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be noted that the drawings are in a very simplified form and are not drawn to scale, and are only used to facilitate and clearly assist the purpose of illustrating the embodiments of the present invention; each block in the block diagrams and/or flowcharts herein , and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented in special purpose hardware-based systems that perform the specified functions or actions, or in combinations of special purpose hardware and computer program instructions. For those skilled in the art, it is conventionally known that implementation in hardware, implementation in software, and implementation in a combination of software and hardware are all equivalent. Furthermore, the structures shown in the drawings are often part of the actual structure. In particular, each diagram needs to show different emphases, and sometimes different proportions are used.

As used in this specification, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

Embodiments of the present invention provide a liquid level measurement method and a single crystal pulling method. The liquid level measurement method is used to detect liquid level information of a melt in a crystal pulling device, and the crystal pulling device includes a furnace body, a crucible, and a flow guide. A cylinder and a detector, the crucible is arranged in the furnace body and is used for accommodating the melt, the guide tube is arranged in the furnace body and is located above the crucible, and the guide tube is connected with the There is a melting gap between the melt liquid levels of the melt, and the liquid level measurement method includes the following steps: configuring a detector to be arranged above the melt liquid level of the melt; using the detector to acquire the information of the first distance from the melt level to the detector; and, based on the information of the first distance, obtain the melt level information from the melt level to the guide tube, and obtain the information of the melt gap. distance. In this way, the detector and the melt level are in a non-contact form, which will not bring pollution during the crystal growth process. Different heights can be set, the melt level is not limited, the range of the melt level that can be measured is large, the melt level information can be obtained in real time, the quality of the single crystal can be improved, the use of target materials is avoided, and there is no need to heat the core. Additional structures can be added to the field area to reduce costs. Further, the distance accuracy detected by the detector is not greater than 0.1 mm, which meets the requirements of crystal growth for the melt level, and improves the reliability and sensitivity of the detector for detecting melt level information.

2 is a flowchart of a liquid level measurement method according to an embodiment of the present invention; FIG. 3 is a schematic diagram of a crystal pulling apparatus according to an embodiment of the present invention; and FIG. 4 is a flowchart of a single crystal pulling method according to an embodiment of the present invention.

Please refer to FIG. 2 to FIG. 3 , the liquid level measurement method is used to detect the liquid level information of the melt 200 in the crystal pulling equipment, for example, the melt level information when detecting the silicon melt in the crystal pulling equipment to prepare a silicon single crystal .

Please refer to FIG. 3 , the crystal pulling equipment is used for preparing crystals from the melt, which includes: a furnace body 400 , a crucible 500 , a guide tube 300 and a detector 100 . The crucible 500 is disposed in the furnace body 400 for accommodating the melt 200 . The guide tube 300 is disposed in the furnace body 400 and above the crucible 500 . For the structures of the crucible 500 and the flow guiding cylinder 300, as well as the positional relationship and connection relationship with the furnace body 400, reference may be made to the prior art. There is a melt gap between the guide cylinder and the melt level of the melt. It should be understood that the melt level information represents the information of the melt gap, that is, the information from the melt level 210 to the guide cylinder 300 , specifically the distance from the melt level 210 to the bottom of the guide cylinder 300 .

The liquid level measurement method includes the following steps:

S1 : The detector 100 is configured to be disposed above the melt level 210 of the melt 200 . The detector 100 is used to send a signal to the melt level 210 and receive a feedback signal from the melt level 210. Specifically, the detector 100 can instantly send a signal to the melt level 210. transmit signal. Preferably, the detector 100 is, for example, a detector of electromagnetic wave signals, such as a radar detector or a radar level gauge. More preferably, the detector is a laser radar, and the laser radar is a radar system that emits a laser beam to detect the position, velocity and other characteristic quantities of the target. Its working principle is to transmit a detection signal (laser beam) to the melt level 210, and then compare the received signal (target echo) reflected from the melt level 210 with the transmitted signal, and then perform appropriate processing. , obtain the first distance L. In a preferred embodiment, the upper part is, for example, a direction perpendicular to the melt level 210 and a direction away from the melt level 210 when the crystal is prepared from the melt. In other embodiments, the position of the detector 100 can be set according to the actual situation, and is not limited to being perpendicular to the melt level 210 , as long as the feedback signal of the melt level 210 can be detected. In this way, the detector 100 is arranged above the melt level 210 , so that the detection flexibility is high, the melt level 210 can be detected comprehensively, and the position of the detector 100 from the melt level 210 is not limited. The detector 100 and the melt level 210 are non-contact detection, which will not bring pollution during the crystal growth process, which improves the reliability of detecting the melt level information. The detector 100 is preferably disposed outside the furnace cavity 410 of the furnace body 400 , so that the detector 100 is prevented from being affected by the atmosphere in the furnace cavity 410 and the detection accuracy is improved. More preferably, a window 600 is opened on the top of the furnace body 400 , and the detector 100 is configured to be disposed at the window 600 . The viewing window 600 enables the detector 100 to be located outside the furnace cavity 410 , and can detect the melt level in the furnace cavity 410 . The viewing window 600 is preferably customized according to the shape and structure of the detector 100 , the viewing window 600 is located on the top of the furnace body 400 , and the distance from the central axis A can be based on the distance from the detector 100 to the center. The distance of the axis A is set adaptively to facilitate the installation of the detector 100 . In the process of crystal growth, a crystal is pulled out from the center of the liquid surface of the melt, and the formed crystal has a cylindrical shape with a certain diameter, and the cylindrical structure crystal has a central axis A. In order to further ensure the The melt level information detected by the detector 100 is not affected by the change of the crystal and the melt level around the crystal during crystal growth. The distance between the detector 100 and the central axis A of the crystal (not shown) is greater than the the diameter of the crystal. Preferably, the distance between the detector 100 and the central axis A of the crystal is between 150 and 400 mm. For example, the distance of the detector 100 from the central axis A of the crystal may be 170 mm.

S2: Use the detector 100 to acquire information about the first distance from the melt level 210 to the detector 100 . Specifically, the detector 100 sends a signal to the melt level 210, the melt level 210 returns the signal to the detector 100, the detector 100 receives the returned signal, and then obtains the melt level 210 to detect The information of the first distance of the detector 100 is obtained, so as to obtain the first distance L from the melt level 210 to the detector 100, so that the detector 100 can obtain the first distance L in real time, so as to prepare for obtaining the real-time melt level information. Work. Preferably, the detector 100 uses an electromagnetic wave signal, and the detector 100 receives the return signal of the electromagnetic wave to obtain the information of the first distance. For example, the detector 100 is a radar detector, so that the detector 100 can have the characteristics of fast response speed of electromagnetic waves, and no medium propagation is required. In other embodiments, the detector 100 may obtain other detection devices for the distance from the melt level 210 to the detector 100 , such as an ultrasonic detector. Preferably, the accuracy of the distance detected by the detector is within 0.1 mm, and the obtained accuracy of the first distance L is also within 0.1 mm, so as to meet the requirements of crystal growth for the liquid level of the melt and improve detection. The sensitivity of the detector 100 to detect melt level information.

S3: Acquire the information of the melt level from the melt level 210 to the guide tube 300 based on the information of the first distance, and obtain the distance M of the melt gap. Through the detector 100, the information of the first distance can be obtained in real time, so that the information of the melt level can be obtained in real time, and the distance M of the melt gap can be obtained. Controlling the temperature distribution of the thermal field improves the quality of the single crystal. In addition, the liquid level detection method of this embodiment is different from the reflection method, in that the position of the melt liquid level can be obtained without using the target material, which reduces the important procedure of selecting the target material, and saves the production cost and labor. At the same time, this embodiment has no additional process requirements for the thermal field structure, and does not need to add other structures in the core thermal field region, thereby reducing the process cost.

In a preferred embodiment, before step S3 obtains the melt level information from the melt level 210 to the guide tube 300 based on the information of the first distance, and obtains the distance M of the melt gap, The liquid level measurement method further includes, as shown in FIG. 3 , preferably disposing the detector 100 directly above the melt level 210 , that is, the detector 100 is essentially connected to the melt liquid. The surface 210 is vertical, or parallel to the pulled crystal (crystal rod), so that one detector 100 can be used to obtain the melt level information without the need for another detector 100 to coordinate measurement. Further, a second distance h from the guide tube 300 to the detector 100 is determined. The second distance h is preferably a distance preset in the design of the crystal pulling equipment, and obtaining the second distance h is a preparatory work for obtaining the melt level information. Since the melt level 210 is below the guide tube 300, the second distance h needs to be smaller than the first distance L from the melt level 210 to the detector 100, so the second distance h is smaller than the first distance h A distance L. In addition, the detector 100 can set the upper and lower limits of the melt level, and if the melt level exceeds the upper and lower limits, an alarm signal will be issued to further ensure the accuracy of the melt level.

Further, the step S3 obtains the melt level information from the melt level 210 to the guide tube 300 based on the information of the first distance, and the step of obtaining the distance of the melt gap includes: M=L-h Wherein, M represents the distance of the melt gap, L represents the first distance, and h represents the second distance, and the real-time melt level information is obtained through the above logic operation.

Based on the same inventive concept, as shown in FIG. 4 , this embodiment also provides a method for pulling a single crystal, and the method for pulling a single crystal includes the following steps: S1: Obtain the melt level information of the melt 200 by using the liquid level measurement method described above; and, S2: Adjust the position of the crucible 500 according to the melt level information. Preferably, after the detector 100 acquires the melt level information of the melt 200, the position of the crucible 500 needs to be adjusted so that the distance from the melt 200 to the guide tube 300 is kept at a predetermined level. The distance is set so that the melt level 210 is always in one position. Preferably, the crystal pulling apparatus further includes a controller (not shown), the controller receives the melt level information fed back by the detector 100 and adjusts the position of the crucible 500 . The controller is connected with the detector 100 in a signal connection, and the information of the melt level can be sent to the controller in real time. Specifically, the controller compares the received melt level information with the previously preset standard liquid level information (the standard liquid level information can represent a preset distance), if the melt level information is less than the standard liquid level If the melt level information is greater than the standard liquid level information, execute the crucible 500 rising command to make the crucible 500 rise; if the melt level information is equal to the standard liquid level information, no command is executed to ensure that the crucible 500 is in a stationary state, so that the position of the crucible 500 can be adjusted in real time.

The single crystal pulling method has the beneficial effects brought by the liquid level measurement method, which will not be repeated here. For the structures and principles of other components of the crystal pulling equipment involved in the single crystal pulling method, reference may be made to the prior art, and no detailed description is required here.

Based on the same inventive concept, this embodiment also provides a storage medium, where a computer program is stored on the storage medium, and when the computer program is executed, the liquid level measurement method as described above can be implemented. The storage medium may be a tangible device capable of holding and storing for use by the instruction execution device, such as, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable storage device described above. combination. The computer programs used to perform the operations of the present embodiments may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or any other program in one or more programming languages. Combining source or object code written in programming languages including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as the "C" language or similar programming languages. The computer program may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote run on a computer or server. The storage medium has the beneficial effects brought about by the liquid level measurement method, which will not be repeated here.

To sum up, in the liquid level measurement method and the single crystal pulling method provided by the present invention, the liquid level measurement method is used to detect the liquid level information of the melt in the crystal pulling equipment, and the crystal pulling equipment includes a furnace body , a crucible, a guide tube and a detector, the crucible is set in the furnace body and used to accommodate the melt, the guide tube is set in the furnace body and located above the crucible, the guide tube There is a melt gap between the flow cylinder and the melt level of the melt, and the liquid level measurement method includes the following steps: configuring a detector to be arranged above the melt level of the melt; using the The detector obtains information of a first distance from the melt level to the detector; and, based on the information of the first distance, obtains the melt level information from the melt level to the diversion cylinder, and obtains The distance of the fusion gap. In this way, the detector and the melt level are in a non-contact form, which will not bring pollution during the crystal growth process. Different heights can be set, the melt level is not limited, the range of melt level that can be measured is large, and the melt level information can be obtained in real time, improving the quality of single crystals, avoiding the use of target materials, and reducing costs.

The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention. Any changes and modifications made by those with ordinary knowledge in the art according to the above disclosure fall into the protection claimed in the patent scope of the appended application. scope.

10: Crucible 20: Melt 21: Level of the melt 30: guide tube 31: Bottom of the guide tube 40: Melting gap 50: Magnet System 60: Heater 70: Graphite 80: graphite felt 90: single crystal 100: Detector 200: Melt 210: Melt level 300: guide tube 400: Furnace body 410: Furnace cavity 500: Crucible 600: Windows M: distance of fusion gap L: first distance h: second distance A: Center axis

Fig. 1 is the schematic diagram of a crystal pulling furnace;

2 is a flowchart of a liquid level measurement method according to an embodiment of the present invention;

3 is a schematic diagram of a crystal pulling apparatus according to an embodiment of the present invention;

FIG. 4 is a flowchart of a method for pulling a single crystal according to an embodiment of the present invention.

S1, S2, S3: Steps

Claims (10)

A liquid level measurement method, comprising: for detecting liquid level information of a melt in a crystal pulling device, the crystal pulling device includes a furnace body, a crucible, a guide tube and a detector, and the crucible is arranged in the furnace body It is used for accommodating the melt, the guide tube is arranged in the furnace body and is located above the crucible, and there is a melting gap between the guide tube and the melt level of the melt, so The liquid level measurement method includes the following steps: configuring the detector to be positioned above the melt level of the melt; Using the detector to obtain information on a first distance from the melt level to the detector; and, Based on the information of the first distance, the information of the melt level from the melt level to the guide cylinder is acquired, and the distance of the melt gap is obtained. The liquid level measurement method according to claim 1, characterized in that, in the information based on the first distance, the information on the melt level from the melt level to the guide cylinder is obtained, and the melt level information is obtained. Before the step of clearance distance, the liquid level measurement method further comprises: The detector is arranged just above the liquid level of the melt, and a second distance from the guide tube to the detector is determined, wherein the second distance is smaller than the first distance. The liquid level measurement method according to claim 2, wherein the information based on the first distance obtains the melt level information from the melt level to the guide cylinder, and obtains the distance from the melt gap The steps include: M=L-h Wherein, M represents the distance of the fusion gap, L represents the first distance, and h represents the second distance. The liquid level measurement method according to claim 1, wherein a crystal is pulled out from the center of the liquid surface of the melt, and the distance between the detector and the central axis of the crystal is 150-400 millimeters (mm )between. The liquid level measurement method according to claim 1, wherein the detector obtains the information of the first distance through a return signal of an electromagnetic wave, or the detector is a laser radar. According to the liquid level measurement method of item 1 of the patent application scope, the accuracy of the distance detected by the detector is within 0.1 mm. The liquid level measurement method of claim 1, wherein a viewing window is opened on the top of the furnace body, and the detector is configured to be disposed at the viewing window. A method for pulling a single crystal, comprising the following steps: Obtain the melt level information of the melt by using the liquid level measurement method described in any one of the claims 1 to 7; and, The position of the crucible is adjusted according to the melt level information. The method for pulling a single crystal according to claim 8, wherein the crystal pulling device includes a controller, and the step of adjusting the position of the crucible according to the melt level information includes: The controller receives the melt level information fed back by the detector, and adjusts the position of the crucible. The method for pulling a single crystal according to claim 9, wherein the step of adjusting the position of the crucible according to the melt level information further comprises: Presetting the standard liquid level information of the controller; comparing the melt level information received by the controller with the standard level information; If the melt liquid level information is less than the standard liquid level information, execute the command to lower the crucible; If the melt level information is greater than the standard level information, execute the crucible rising command; If the melt level information is equal to the standard level information, the command is not executed.

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