TW202225645A - Liquid level detector for crystal growth and crystal growth apparatus - Google Patents

Abstract

A liquid level detector for crystal growth and a crystal growth apparatus are disclosed. The liquid level detector comprise a furnace, a draft tube, a camera and a graphic processor. The furnace is positioned with a crucible in which melted mass is received. The draft tube is above the melted mass. A dowel pin is positioned at an end of the draft tube. At least a portion of the dowel pin is filled with opaque material. The camera is used for obtaining an image of the dowel pin and its reflection on a liquid level of the melted mass. The graphic processor calculates a distance between the dowel pin and the liquid level of the melted mass based on the image of the dowel pin and its reflection on the liquid level of the melted mass. The distance between the dowel pin and the liquid level of the melted mass can be calculated accurately in an easy, convenient and low-cost way because the at least a portion of the dowel pin is filled with opaque material and the clear image of the dowel pin positioned at the end of the draft tube and its reflection on the liquid level of the melted mass is obtained by the camera.

Description

A liquid level detection device for crystal growth and crystal growth device

The present invention relates to the technical field of crystal growth, in particular to a liquid level detection device and a crystal growth device for crystal growth.

With the rapid development of the integrated circuit (IC) industry, component manufacturers have put forward more stringent requirements for IC-grade silicon single crystal materials, and large-diameter single crystal silicon is a necessary substrate material for preparing components. The Czochralski method (CZ method) is the most important method for growing a single crystal from a melt in the prior art. Seed crystals are placed on the surface of the melt to pull the melt, and under controlled conditions, the seeds and the melt are continuously rearranged on the interface of atoms or molecules, and the crystals are grown by gradually solidifying with the cooling.

During the crystal growth process, it is necessary to measure the distance between the liquid level of the melt and the guide cylinder, and it is difficult to accurately measure the distance by the existing technical means.

Therefore, it is necessary to propose a new crystal growth apparatus to solve the above problems.

A series of concepts in simplified form have been introduced in the Summary section, which are described in further detail in the Detailed Description section. The Summary of the Invention section of the present invention is not intended to attempt to limit the key features and essential technical features of the claimed technical solution, nor is it intended to attempt to determine the protection scope of the claimed technical solution.

The invention provides a liquid level detection device for crystal growth, comprising: a furnace body, wherein a crucible is arranged in the furnace body, and the crucible contains melt; The bottom of the flow cylinder is provided with a positioning pin, and at least a part of the positioning pin is filled with opaque material; a camera is used to obtain an image of the positioning pin and the reflection of the positioning pin on the melt liquid surface; an image processor, based on the positioning The image of the reflection of the pin and the alignment pin on the melt level calculates the distance between the alignment pin and the melt level.

Further, the positioning pins are made of opaque material.

Further, the positioning pin includes a housing portion and a filling portion.

Further, the housing portion includes a high temperature resistant material.

Further, the housing portion includes quartz.

Further, the shell portion includes high-transparency quartz with a low impurity content.

Further, the filling portion includes an opaque material.

Further, the filled portion includes graphite or silicon.

Further, an observation window may be provided on the furnace body, a camera is provided outside the furnace body, and liquid level detection is performed through the observation window.

The present invention also provides a crystal growth device, including the liquid level detection device as described above.

According to the liquid level detection device for crystal growth provided by the present invention, at least a part of the positioning pin is filled with opaque material, so as to use a camera to obtain the reflection of the positioning pin arranged at the bottom of the guide cylinder and the positioning pin on the melt liquid surface Clear image to accurately calculate the distance between the positioning pin and the melt level, easy operation and low cost.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without one or more of these details. In other instances, some technical features known in the art have not been described in order to avoid obscuring the present invention.

For a thorough understanding of the present invention, a detailed description will be set forth in the following description to explain the liquid level detection apparatus for crystal growth of the present invention. Obviously, the practice of the present invention is not limited to the particular details familiar to those skilled in the art of crystal growth. Preferred embodiments of the present invention are described in detail below, however, the present invention may have other embodiments in addition to these detailed descriptions.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments in accordance with the present invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly dictates otherwise. Furthermore, it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, it indicates the presence of the stated features, integers, steps, operations, elements and/or components, but does not exclude the presence or Addition of one or more other features, integers, steps, operations, elements, components and/or combinations thereof.

Now, exemplary embodiments according to the present invention will be described in more detail with reference to the accompanying drawings. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity, and the same reference numerals are used to denote the same elements, and thus their descriptions will be omitted.

1, the apparatus for crystal growth includes a furnace body 1, which includes a crucible 5, the periphery of the crucible 5 is provided with a heater 6, and the crucible 5 has a melt 4 therein, A crystal 2 is formed above the melt 4 , and a guide tube 3 is provided above the crucible 5 around the crystal 2 . As an example, the crystal 2 is a single crystal silicon ingot.

Exemplarily, the furnace body 1 is a stainless steel cavity, and the furnace body 1 is vacuumed or filled with protective gas. As an example, the protective gas is argon, the purity of which is above 99.999%, the pressure is 5mbar-100mbar, and the flow rate is 70slpm-200slpm.

Exemplarily, the crucible 5 is made of high-temperature and corrosion-resistant materials, and the crucible 5 contains the melt 4 for crystal growth. In one embodiment, the crucible 5 comprises a quartz crucible and/or a graphite crucible. The crucible 5 contains raw materials, such as polysilicon. The raw material is heated in the crucible 5 into a melt 4 for growing single crystal silicon rods. Specifically, a seed crystal is immersed in the melt, and the seed crystal is rotated and slowly pulled by the seed crystal axis, so that the silicon atoms move along the The seed crystals grow into single crystal silicon rods. The seed crystal is cut or drilled from a silicon single crystal with a certain crystal orientation. Common crystal orientations are <100>, <111>, <110>, etc. The crystal seed is generally a cylinder.

Exemplarily, a heater 6 is provided on the periphery of the crucible 5, and the heater 6 can be a graphite heater, which can be arranged on the side and/or bottom of the crucible 5, in order to electrically heat the crucible 5. . Further, the heater 6 includes one or more heaters arranged around the crucible 5 to make the thermal field distribution of the crucible 5 uniform.

Exemplarily, the furnace body 1 is also provided with a guide tube 3, which is located above the crucible 5, and is located on the outside of the crystal 2 and is arranged around the crystal 2 to prevent the heat of the melt 4 from being transferred to the crystal 2 in the form of thermal radiation and the like. In the furnace body 1, heat loss occurs.

Further, the crystal growth apparatus further includes a crucible lifting mechanism 7 for supporting and rotating the crucible shaft, so as to realize the lifting and lowering of the crucible 5 .

Exemplarily, the crystal growth process of the single crystal silicon ingot sequentially includes several stages of seeding, shoulder placing, shoulder turning, equalizing and finishing.

The seeding stage is performed first. That is, after the melt 4 is stabilized to a certain temperature, the seed crystal 3 is immersed in the melt 4, and the seed crystal 3 is lifted at a certain pulling speed, so that the silicon atoms grow along the seed crystal into a narrow neck of a certain diameter, until the narrow neck to the predetermined length. The main function of the seeding process is to eliminate the dislocation defect formed by the single crystal silicon caused by thermal shock, and use the supercooling degree of the crystallization front to drive the silicon atoms to arrange the silicon solid at the solid-liquid interface in order, Monocrystalline silicon is formed. Exemplarily, the pulling speed is 1.5mm/min-4.0mm/min, the length of the slender neck is 0.6-1.4 times the diameter of the crystal rod, and the diameter of the slender neck is 4mm-6mm.

Then, in the shouldering stage, when the thin neck reaches a predetermined length, the upward pulling speed of the seed crystal 3 is slowed down, and the temperature of the melt 4 is slightly lowered at the same time. The cooling is performed to promote the lateral growth of the single crystal silicon. , even if the diameter of the single crystal silicon increases, this process is called the shouldering stage.

Then, enter the shoulder turning stage. When the diameter of the single crystal silicon increases to the target diameter, by increasing the heating power of the heater 6, the temperature of the melt 4 is increased, and at the same time, the upward pulling speed of the seed crystal 3, the speed of rotation and the temperature of the crucible 5 are adjusted. The rotation speed, etc., inhibits the lateral growth of the single crystal silicon, promotes its vertical growth, and makes the single crystal silicon grow nearly equal in diameter.

Then, enter the equal diameter stage. When the diameter of the single crystal silicon ingot reaches a predetermined value, it enters the equal diameter stage, and the cylindrical ingot formed in this stage is the equal diameter section of the ingot. Specifically, the temperature of the crucible, the crystal pulling speed, the rotating speed of the crucible and the crystal are adjusted to stabilize the growth rate and keep the crystal diameter unchanged until the crystal pulling is completed. The isodiametric process is the main stage of single crystal silicon growth, which lasts for dozens of hours or even more than a hundred hours.

Finally, enter the finishing stage. At the end, the lifting rate is increased, and the temperature of melt 4 is increased at the same time, so that the diameter of the ingot is gradually reduced to form a cone, and when the cone tip is small enough, it will eventually leave the liquid surface. The finished ingot is lifted to the upper furnace chamber for cooling for a period of time and taken out, that is, a growth cycle is completed.

In the crystal growth process, it is very important to measure the distance between the liquid level of the melt 4 and the guide cylinder 3. Therefore, the crystal growth device provided by the present invention includes a liquid level detection device for crystal growth, such as As shown in FIG. 1 , it includes: a furnace body 1 , a crucible 5 is arranged in the furnace body 1 , and the crucible 5 includes a melt 4 ; a guide tube 3 , the guide tube 3 is located in the melt 4, the bottom of the guide tube 3 is provided with a positioning pin 9, and at least a part of the positioning pin 9 is filled with opaque material; the camera 8 is used to obtain the positioning pin 9 and the positioning pin in the The image of the reflection on the liquid surface of the melt 4; the image processor, based on the image of the positioning pin 9 and the reflection of the positioning pin on the liquid surface of the melt, calculates the positioning pin 9 and the The distance between the liquid levels of the melt 4.

Illustratively, the camera 8 includes any device that can be used for optical imaging, including but not limited to digital cameras, high-definition video cameras, and the like. In one embodiment, the camera 8 comprises a CCD camera.

Further, the camera 8 is arranged outside the furnace body 1 , and liquid level detection is performed through an observation window opened on the furnace body 1 .

Exemplarily, the liquid level detection device for crystal growth provided by the present invention further includes an image processor, and the image processor can detect the liquid level of the melt 4 based on the positioning pin 9 and the positioning pin. Calculate the distance between the positioning pin 9 and the level of the melt 4 on the image of the reflection.

Due to the high temperature environment for crystal growth, the positioning pins should be made of high temperature resistant materials, preferably transparent high-purity quartz. Quartz can be used normally at 1350°C, its softening temperature is about 1700°C, and the expansion coefficient is low, which is suitable for crystal growth. . Further, because crystal growth has high requirements on impurities and metals, and the impurity content of high transparency is the smallest, the lower the impurity content of quartz, the purer and more transparent the quartz, and the better the high temperature resistance, so most of the high-purity and transparent quartz is used. pins as internal locating pins.

However, when the positioning pin 9 is made of a transparent material, the reflection of the positioning pin 9 on the liquid level of the melt 4 is very blurred, and it is difficult to accurately calculate the distance between the positioning pin 9 and the liquid level of the melt 4 by an image processor. However, replacing the camera 8 with a higher precision is not obvious for improving the imaging effect of the reflection, and increases the production cost.

Based on the advantages of the above-mentioned transparent high-purity quartz as the positioning pin, in the case of continuing to use the transparent high-purity quartz as the positioning pin material, in order to solve the unclear reflection of the high-purity transparent quartz, at least part of the positioning pin needs to be filled with opaque materials to achieve The purpose of the reflection shadow is clear.

In one embodiment, as shown in FIG. 2 , the positioning pin 9 includes a housing portion 901 and a filling portion 902 .

Illustratively, the housing portion 901 includes a high temperature resistant material. Further, the housing part 901 is made of transparent high-purity quartz.

In one embodiment, the central portion of the quartz locating pin widely used in the prior art is removed to form a hollow quartz locating pin, and the quartz is used as the housing portion of the locating pin.

In one embodiment, a hollow quartz locating pin is prepared using a hollow design, and quartz is used as the housing part of the locating pin.

Further, since the casing part 901 is made of a transparent material, an opaque material must be used as the filling part 902 . As an example, the high-purity graphite-based high temperature resistance is much higher than that of quartz and the thermal expansion coefficient is smaller than that of quartz, the filling portion 902 includes but is not limited to graphite or silicon.

For the quartz positioning pins widely used in the prior art, it is only necessary to form a hollow part therein and fill with opaque materials, and then it can be used as the positioning pin 9 of the liquid level detection device for crystal growth provided by the present invention, which is less difficult to manufacture and low in cost. , the imaging effect of the reflection can be significantly improved, so that the distance between the positioning pin 9 and the liquid level of the melt 4 can be accurately calculated.

According to the liquid level detection device for crystal growth provided by the present invention, a camera is used to obtain a clear image of the positioning pin arranged at the bottom of the guide tube and the reflection of the positioning pin on the melt liquid level, so as to accurately calculate the The distance between the positioning pin and the melt level is easy to operate and low in cost.

The present invention has been described by the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of illustration and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and more variations and modifications can also be made according to the teachings of the present invention, which all fall within the requirements of the present invention. within the scope of protection. The protection scope of the present invention is defined by the application patent scope and its equivalent scope.

1: Furnace body 2: Crystal 3: guide tube 4: Melt 5: Crucible 6: Heater 7: Crucible lifting mechanism 8: Camera 9: Locating pin 901: Shell part 902: Padding section

The following drawings of the present invention are incorporated herein as a part of the present invention for understanding of the present invention. The accompanying drawings illustrate embodiments of the present invention and their description, which serve to explain the principles of the present invention.

FIG. 1 is a schematic diagram of a liquid level detection apparatus for crystal growth and a crystal growth apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a positioning pin according to an exemplary embodiment of the present invention.

none

1: Furnace body

2: Crystal

3: guide tube

4: Melt

5: Crucible

6: Heater

7: Crucible lifting mechanism

8: Camera

9: Locating pin

Claims (9)

A liquid level detection device for crystal growth, comprising: a furnace body, the furnace body is provided with a crucible, and the crucible contains a melt; a guide tube, the guide tube is located above the melt, the bottom of the guide tube is provided with a positioning pin, and at least a part of the positioning pin is filled with opaque material; a camera for acquiring the image of the positioning pin and the reflection of the positioning pin on the melt surface; An image processor calculates the distance between the positioning pin and the melt level based on the image of the positioning pin and the reflection of the positioning pin on the melt level. The liquid level detection device of claim 1, wherein the positioning pin includes a housing part and a filling part. The liquid level detection device of claim 2, wherein the housing portion includes a high temperature resistant material. The liquid level detection device of claim 3, wherein the housing portion includes quartz. The liquid level detection device of claim 4, wherein the housing portion comprises high-transparency quartz with a low impurity content. The liquid level detection device of claim 2, wherein the filling portion includes an opaque material. The liquid level detection device according to claim 6, wherein the filling part comprises graphite or silicon. The liquid level detection device according to claim 1, wherein an observation window is provided on the furnace body, the camera is provided outside the furnace, and the liquid level detection is performed through the observation window. A crystal growth device, comprising the liquid level detection device according to any one of claims 1-8.

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