Liquid opening distance measuring device, preparation method thereof and method for measuring liquid opening distance in single crystal furnace

Abstract

The invention relates to the technical field of semiconductors, and provides a liquid opening distance measuring device, a preparation method thereof and a liquid opening distance measuring method in a single crystal furnace. The liquid port distance measuring device comprises: a quartz piece, the interior of which is provided with a cross-shaped accommodating cavity extending along a first direction, the first direction being parallel to the axial direction of the quartz piece; the graphite piece is in a cross-shaped cylinder shape, the graphite piece is contained in the cross-shaped containing cavity of the quartz piece in a sealed mode, and the graphite piece is visible relative to the first end portion of the quartz piece; the graphite piece is made of high-purity graphite, and the quartz piece is made of high-purity quartz. High-purity materials are processed to form the matched graphite piece and quartz piece, the graphite piece and the quartz piece are fired and sealed to prepare the liquid opening distance measuring device, and the liquid opening distance can be accurately measured according to changes of imaging pixels of inverted image imaging by capturing inverted image imaging of the graphite piece in a silicon melt in combination with a CCD imaging system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a liquid port distance measuring device for single crystal silicon direct growth, a preparation method thereof, and a liquid port distance measuring method in a single crystal furnace. BACKGROUND

[0002] High-purity single crystal silicon is an important semiconductor material, which can be made into diodes, triodes, thyristors, and various integrated circuits (including chips and CPUs in computers), and can also be made into solar photovoltaic cells to convert radiant energy into electrical energy. With the development of the integrated circuit industry, higher requirements are placed on the purity, high uniformity, high integrity, and large diameter of single crystal silicon materials.

[0003] The liquid port distance refers to the distance from the lower end face of the flow guide cylinder of the single crystal furnace close to the surface of the silicon melt to the surface of the silicon melt, and is a key process parameter in single crystal silicon production. The liquid port distance has a significant impact on the quality of the crystal during the direct growth of single crystal silicon, and is reflected in the heat field distribution and temperature gradient, impurity and oxygen content control, improvement of crystal defects, process stability and automatic control, and crystal diameter stability.

[0004] Therefore, accurate control of the liquid port distance is crucial for improving the quality, stability, and production efficiency of single crystal silicon. SUMMARY

[0005] The present application aims to provide a liquid port distance measuring device and a preparation method thereof, and a liquid port distance measuring method in a single crystal furnace, which can improve the accurate measurement of the liquid port distance during crystal growth.

[0006] To achieve the above-mentioned purpose, the present application provides a preparation method of a liquid port distance measuring device, which comprises the following steps: processing high-purity graphite into a cruciform column-shaped graphite piece; processing high-purity quartz into a quartz piece having a cruciform accommodating cavity extending from a first end portion to the interior along a first direction, the cruciform accommodating cavity being adapted to the cruciform column, and the depth of the cruciform accommodating cavity being greater than the height of the cruciform column, the first direction being parallel to the axial direction of the quartz piece; and placing the graphite piece into the cruciform accommodating cavity of the quartz piece and sealing by firing to form a sealed structure of the graphite piece visible relative to the first end portion of the quartz piece as the liquid port distance measuring device.

[0007] In order to achieve the above object, the application further provides a liquid mouth distance measuring device prepared by the preparation method, comprising: a quartz piece having a cross-shaped accommodating cavity extending along a first direction inside, the first direction being parallel to the axial direction of the quartz piece; a graphite piece having a cross-shaped columnar shape, the graphite piece being sealingly accommodated in the cross-shaped accommodating cavity of the quartz piece and being visible relative to the first end of the quartz piece; the graphite piece being made of high-purity graphite, and the quartz piece being made of high-purity quartz.

[0008] In order to achieve the above object, the application further provides a liquid mouth distance measuring method in a single crystal furnace, the measuring method comprising the following steps: providing a single crystal furnace, the single crystal furnace carrying a silicon melt; suspending a liquid mouth distance measuring device above the silicon melt in the single crystal furnace, the liquid mouth distance measuring device being the liquid mouth distance measuring device according to the application; and capturing the inverted imaging of the graphite piece of the liquid mouth distance measuring device in the silicon melt by using a CCD imaging system, and obtaining the current liquid mouth distance according to the imaging pixels of the inverted imaging.

[0009] The above technical solution is characterized in that the graphite piece and the quartz piece are processed from high-purity materials, and the liquid mouth distance measuring device is prepared by sealing and firing, and the inverted imaging of the graphite piece in the silicon melt is captured by using a CCD imaging system, and the liquid mouth distance is accurately measured according to the change of the imaging pixels of the inverted imaging. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor.

[0011] Figure 1 The preparation method flow chart of the liquid mouth distance measuring device provided by an embodiment of the application; Figure 2 The structure schematic diagram of the liquid mouth distance measuring device provided by an embodiment of the application; Figure 3 The flow chart of the liquid mouth distance measuring method in a single crystal furnace provided by an embodiment of the application. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings. Obviously, the described embodiments are only some embodiments of the application, not all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0013] Please see Figures 1-2 wherein, Figure 1 The preparation method flow chart of the liquid port distance measuring device provided by an embodiment of the present application is shown in the figure. Figure 2 The structure schematic diagram of the liquid port distance measuring device provided by an embodiment of the present application is shown in the figure.

[0014] As Figure 1 shown, the preparation method of the liquid port distance measuring device provided by the embodiment includes the following steps: S11, processing high-purity graphite into a graphite piece in the shape of a cross-shaped column; S12, processing high-purity quartz into a quartz piece having a cross-shaped accommodating cavity extending from a first end portion to the interior along a first direction, the cross-shaped accommodating cavity being adapted to the cross-shaped column, and the first direction being parallel to the axial direction of the quartz piece; and S13, placing the graphite piece into the cross-shaped accommodating cavity of the quartz piece and sintering to seal the graphite piece, thereby forming the liquid port distance measuring device. The execution order of steps S11 and S12 can be exchanged or they can be executed simultaneously.

[0015] Regarding step S11, high-purity graphite is processed into a graphite piece in the shape of a cross-shaped column.

[0016] Before preparing the liquid port distance measuring device, the material of the device needs to be determined. Considering the control requirements of impurities in the silicon single crystal direct growth, high-purity graphite material is selected for the internal structure of the device. High-purity graphite (carbon content > 99.99%) is a new type of industrial core material and plays a key role in the fields of semiconductors, aerospace, etc.

[0017] In this embodiment, the purity of the high-purity graphite is semiconductor grade. The purity of semiconductor-grade high-purity graphite can reach 99.99995% or even 7N grade (99.99999%); semiconductor-grade high-purity graphite is used for wafer manufacturing and can meet the extreme purity requirements of materials for chip production.

[0018] In this embodiment, high-purity graphite is polished into a graphite piece 21 (shown in Figure 2 ) in the shape of a cross-shaped column. The outer contour size of the cross-shaped column ranges from 4mm*4mm*18mm to 6mm*6mm*22mm, and the graphite thickness of the graphite piece is 0.75-1.25mm. For example, the outer contour size of the cross-shaped column is 4mm*4mm*18mm, and the graphite thickness of the graphite piece is 0.75mm; or, the outer contour size of the cross-shaped column is 5mm*5mm*20mm, and the graphite thickness of the graphite piece is 1mm; or, the outer contour size of the cross-shaped column is 6mm*6mm*22mm, and the graphite thickness of the graphite piece is 1.25mm.

[0019] As to step S12, high-purity quartz is processed into a quartz piece having a cruciform accommodating cavity extending from a first end portion to an interior along a first direction, the cruciform accommodating cavity being adapted to the cruciform column body, and a depth of the cruciform accommodating cavity being greater than a height of the cruciform column body. Here, the first direction D1 is parallel to an axial direction of the quartz piece 22 (shown in Figure 2 FIG. 2).

[0020] Before the liquid port distance measuring device is prepared, the material of the device needs to be determined. Considering the control requirements of impurities in the silicon single crystal Czochralski growth, high-purity quartz material is selected for the external structure of the device. High-purity quartz (Ultra-High Purity Quartz, referred to as UHPQ) refers to a quartz material with a purity of SiO2≥99.995% (4N5 level) or above, which has the characteristics of high temperature resistance and low thermal expansion, and is a key material for semiconductor silicon wafers, photovoltaic quartz crucibles, etc.

[0021] In this embodiment, the purity of the high-purity quartz is semiconductor grade. The semiconductor-grade high-purity quartz is a quartz material with a purity of SiO2≥99.998% (4N8 level) or above, and the total amount of impurity elements (such as Al, Fe, Ti, Na, K, etc.) is usually less than 20 ppm (parts per million). Due to its extremely high chemical purity and structural stability, high-purity quartz has excellent optical transmittance in the ultraviolet-visible-infrared band, and also has extremely low thermal expansion coefficient (5.5×10 -7 / ℃), excellent high temperature resistance (softening point > 1700℃), and excellent dielectric properties.

[0022] In this embodiment, a mold can be used to process high-purity quartz into a quartz piece 22 (shown in Figure 2 FIG. 2) having a cruciform accommodating cavity 220 extending from a first end portion to an interior along a first direction D1, and a gap between an inner diameter of the cruciform accommodating cavity 220 and an outer diameter of the cruciform column body satisfies the expansion value of the high-purity graphite and the high-purity quartz thermal expansion when sintering and sealing, avoiding the risk of mismatch between the cruciform accommodating cavity and the cruciform column body caused by thermal expansion of quartz and graphite.

[0023] As to step S13, the graphite piece is placed in the cruciform accommodating cavity of the quartz piece and sintered and sealed to form a sealed structure of the graphite piece relative to the first end portion of the quartz piece as the liquid port distance measuring device.

[0024] Due to the depth of the cross-shaped accommodating cavity is greater than the height of the cross-shaped column, when sealing by firing, the quartz material of the first end of the quartz piece melts and extends to the cross-shaped accommodating cavity, covering the cross-shaped column, so that the graphite oxidation of the graphite piece can be avoided. The transparency of high-purity quartz makes the graphite piece of the first end of the quartz piece and the cross-shaped column still visible after the cross-shaped accommodating cavity is sealed.

[0025] In the embodiment, the preparation method further includes: forming a through hole 229 (shown in Figure 2 ) through the quartz piece 22 in a second direction D2 at the second end of the quartz piece 22. The second end 222 is arranged opposite to the first end 221 in the first direction D1, the first direction D1 is parallel to the axial direction of the quartz piece 22, and the second direction D2 is parallel to the radial direction of the quartz piece 22.

[0026] The embodiment forms the graphite piece and the quartz piece by determining the material of the device, and forms the liquid level distance measuring device by firing and sealing. The CCD imaging system is combined to capture the inverted image of the graphite piece in the silicon melt, and the liquid level distance can be accurately measured according to the change of the imaging pixels of the inverted image.

[0027] Based on the same inventive concept, the application also provides a liquid level distance measuring device prepared by the preparation method.

[0028] As Figure 2 shown, the liquid level distance measuring device includes a quartz piece 22 and a graphite piece 21.

[0029] Specifically, the quartz piece 22 has a cross-shaped accommodating cavity 220 extending in a first direction D1 inside the quartz piece 22, and the first direction D1 is parallel to the axial direction of the quartz piece 22. The graphite piece 21 has a cross-shaped column shape, the graphite piece 21 is sealed and accommodated in the cross-shaped accommodating cavity 220 of the quartz piece 21, and the graphite piece 21 is visible relative to the first end 221 of the quartz piece 22. The material of the graphite piece 21 is high-purity graphite, and the material of the quartz piece 22 is high-purity quartz.

[0030] In the embodiment, high-purity graphite is polished into a graphite piece 21 in the shape of a cross-shaped column, the cross-shaped column has an outer contour size ranging from 4mm*4mm*18mm to 6mm*6mm*22mm, and the graphite thickness of the graphite piece is 0.75mm to 1.25mm. For example, the outer contour size of the cross-shaped column ranges from 4mm*4mm*18mm, and the graphite thickness of the graphite piece is 0.75mm; or the outer contour size of the cross-shaped column ranges from 5mm*5mm*20mm, and the graphite thickness of the graphite piece is 1mm; or the outer contour size of the cross-shaped column ranges from 6mm*6mm*22mm, and the graphite thickness of the graphite piece is 1.25mm.

[0031] In the embodiment, the second end portion 222 of the quartz piece 22 is further formed with a through hole 229 penetrating the quartz piece 22 in a second direction, and the liquid level distance measuring device can be suspended through the through hole 229. The second end portion 222 is arranged opposite to the first end portion 221 in the first direction D1, the first direction D1 is parallel to the axial direction of the quartz piece 22, and the second direction D2 is parallel to the radial direction of the quartz piece 22.

[0032] Based on the same inventive concept, the present application further provides a liquid level distance measuring method in a single crystal furnace, which adopts the liquid level distance measuring device to accurately measure the liquid level distance.

[0033] Referring to Figure 2 , which is a flow chart of the liquid level distance measuring method in a single crystal furnace provided by an embodiment of the present application. As shown in Figure 3 Figure 3 , the liquid level distance measuring method in a single crystal furnace provided by the embodiment includes the following steps: S31, providing a single crystal furnace, the single crystal furnace carrying a silicon melt; S32, suspending a liquid level distance measuring device above the silicon melt in the single crystal furnace, the liquid level distance measuring device being the liquid level distance measuring device provided by the present application; and S33, capturing the inverted imaging of the graphite piece of the liquid level distance measuring device in the silicon melt by using a CCD imaging system, and acquiring the current liquid level distance according to the imaging pixels of the inverted imaging.

[0034] Regarding step S31, a single crystal furnace is provided, and the single crystal furnace carries a silicon melt.

[0035] Specifically, the single crystal furnace is provided with a crucible carrying a silicon melt, a single crystal silicon ingot is formed above the silicon melt, a flow guide cylinder is arranged above the crucible, and the flow guide cylinder surrounds the ingot. The liquid level distance measuring device is suspended above the silicon melt in the single crystal furnace and arranged in the space defined by the silicon melt, the flow guide cylinder and the ingot.

[0036] In step S32, the liquid level measurement device is suspended above the silicon melt in the single crystal furnace.

[0037] The transparency of the high-purity quartz allows the graphite part of the cross-shaped cylinder to be visible from the first end of the quartz part after the cross-shaped cavity is sealed. The orthographic projection of the liquid level measurement device in the single crystal furnace falls above the silicon melt, so that the graphite part of the liquid level measurement device can form a mirror image in the silicon melt.

[0038] In the present embodiment, the second end of the quartz part of the liquid level measurement device is also formed with a through hole penetrating the quartz part in a second direction, wherein the second end is arranged opposite to the first end in the first direction, and the second direction is parallel to the radial direction of the quartz part. Step S32 further includes suspending the liquid level measurement device above the silicon melt in the single crystal furnace through the through hole.

[0039] In step S33, the mirror image of the graphite part of the liquid level measurement device in the silicon melt is captured by a CCD imaging system, and the current liquid level is obtained according to the imaging pixels of the mirror image.

[0040] In some embodiments, the step of obtaining the current liquid level according to the imaging pixels of the mirror image specifically includes: calibrating the CCD imaging system according to a known liquid level and the corresponding imaging pixels of the graphite part; and obtaining the current liquid level according to the current imaging pixels of the mirror image and the conversion coefficient. For example, in implementation, the CCD imaging system is first calibrated; then, in the case of a known liquid level (e.g., 100 mm and 20 mm), the imaging pixels (e.g., 40*40 and 120*120) of the corresponding graphite part are obtained, and then the conversion coefficient (0.8) is obtained; when the liquid level changes, the current liquid level can be determined as long as the current imaging pixels are obtained; for example, if the current imaging pixels are 80*80, the current liquid level is determined to be 60 mm. Through measurement, the error of the method of the present application is within 0.5 mm, and accurate measurement of the liquid level can be achieved.

[0041] The above embodiments use high-purity materials to process the matching graphite part and quartz part, and then seal and prepare the liquid level measurement device. Combined with a CCD imaging system, the mirror image of the graphite part in the silicon melt is captured, and the liquid level is accurately measured according to the change of the imaging pixels of the mirror image.

[0042] It should be noted that reference to "an embodiment", "one embodiment", "an example embodiment", "some embodiments" etc. in the specification indicates that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment can not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of those skilled in the relevant art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicit

[0043] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that one skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, the mere fact that several of these listed means are refened to in parallel in the claim does not exclude that devices other than the listed means are used in the device. In a method claim enumerating several steps, the mere fact that several of these steps are recited in parallel in the claim does not exclude the presence of steps other than the ones listed. The terms "first", "second" and the like in the description do not imply any particular order, but they are used for purposes of nomenclature only. The terms "comprise", "comprising", "include", "including" and the like are used herein to indicate the presence of stated features, steps or components but do not preclude the presence or addition of one or more other features, steps or components. The indefinite articles "an" and "a" and "the" used in the context of the present application are to be construed as referring to one or more (i.e. at least one) of the items to which they refer. It is to be understood that the terms so used are interchangeable under appropriate circumstances and herein are used for ease of expre

[0044] The above description is only the preferred embodiment of the application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can make some improvements and refinements, these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing a liquid outlet distance measuring device, characterized in that, The preparation method includes the following steps: processing high-purity graphite into a graphite part in the shape of a cross-shaped column; processing high-purity quartz into a quartz part having a cross-shaped cavity extending from a first end inward along a first direction, wherein the cross-shaped cavity is adapted to the cross-shaped column and the depth of the cross-shaped cavity is greater than the height of the cross-shaped column, and the first direction is parallel to the axial direction of the quartz part. The graphite part is placed into the cross-shaped cavity of the quartz part and sealed by firing, forming a visible sealing structure of the first end of the graphite part relative to the quartz part as the liquid outlet distance measuring device.

2. The preparation method according to claim 1, characterized in that, Both the high-purity quartz and the high-purity graphite are of semiconductor grade purity.

3. The preparation method according to claim 1, characterized in that, The gap between the inner diameter of the cross-shaped cavity and the outer diameter of the cross-shaped column satisfies the thermal expansion value of the high-purity graphite and the high-purity quartz during the firing and sealing process.

4. The preparation method according to claim 1, characterized in that, Also includes: A through hole is formed at the second end of the quartz component, extending through the quartz component along a second direction; wherein the second end is disposed opposite to the first end along the first direction, and the second direction is parallel to the radial direction of the quartz component.

5. A liquid outlet distance measuring device, characterized in that, The product is prepared by the method described in claim 1, comprising: a quartz component having a cross-shaped cavity extending along a first direction, the first direction being parallel to the axial direction of the quartz component; a graphite component having a cross-shaped columnar shape, the graphite component being sealed and housed within the cross-shaped cavity of the quartz component, and the graphite component being visible relative to a first end of the quartz component; the graphite component is made of high-purity graphite, and the quartz component is made of high-purity quartz.

6. The liquid outlet distance measuring device as described in claim 5, characterized in that, The outer contour dimensions of the cross-shaped column range from 4mm*4mm*18mm to 6mm*6mm*22mm, and the graphite thickness of the graphite part is 0.75~1.25mm.

7. The liquid outlet distance measuring device as described in claim 5, characterized in that, The second end of the quartz component is further provided with a through hole extending through the quartz component in a second direction, through which the liquid outlet distance measuring device can be suspended; wherein, the second end and the first end are disposed opposite to each other in the first direction, and the second direction is parallel to the radial direction of the quartz component.

8. A method for measuring the liquid outlet distance in a single crystal furnace, characterized in that, The measurement method includes the following steps: providing a single crystal furnace, wherein a silicon melt is carried inside the single crystal furnace; suspending a liquid gate distance measuring device above the silicon melt inside the single crystal furnace, wherein the liquid gate distance measuring device is the liquid gate distance measuring device as described in claim 5; and using a CCD imaging system to capture the reflection image of the graphite part of the liquid gate distance measuring device in the silicon melt, and obtaining the current liquid gate distance based on the imaging pixels of the reflection image.

9. The method for measuring the liquid outlet distance in a single crystal furnace as described in claim 8, characterized in that, The step of obtaining the current liquid nozzle distance based on the imaging pixels of the reflection image specifically includes: obtaining a conversion coefficient in advance based on the known liquid nozzle distance and the corresponding imaging pixels of the graphite component; and obtaining the current liquid nozzle distance based on the current imaging pixels of the reflection image and the conversion coefficient.

10. The method for measuring the liquid outlet distance in a single crystal furnace as described in claim 8, characterized in that, The second end of the quartz component of the liquid outlet distance measuring device is further provided with a through hole extending through the quartz component in a second direction, wherein the second end and the first end are disposed opposite to each other in the first direction, and the second direction is parallel to the radial direction of the quartz component; the step of suspending the liquid outlet distance measuring device above the silicon melt in the single crystal furnace specifically includes: suspending the liquid outlet distance measuring device above the silicon melt in the single crystal furnace through the through hole.

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