Silicon rod preparation method, silicon rod production device, silicon rod and silicon wafer

Abstract

The invention provides a silicon rod preparation method, a silicon rod production device, a silicon rod and a silicon wafer, and the preparation method comprises the steps: in a first equal-diameter stage, furnace pressure is maintained to be first furnace pressure, and in the first equal-diameter stage, the silicon rod does not enter an auxiliary chamber and the distance between the silicon rod and the auxiliary chamber is greater than a preset distance; in the second equal-diameter stage, the furnace pressure is increased to second furnace pressure, and in the second equal-diameter stage, the distance between the silicon rod and the auxiliary chamber is equal to or smaller than the preset distance; and in the third equal-diameter stage, the furnace pressure is reduced to third furnace pressure, and in the third equal-diameter stage, the length of the part, entering the auxiliary chamber, of the silicon rod is equal to or larger than the preset length. According to the silicon rod preparation method and the silicon rod production device, shaking and wire breaking of the silicon rod can be avoided.

Description

Technical Field

[0001] The present application mainly relates to the field of photovoltaic technology, and in particular to a method for preparing a silicon rod, a silicon rod production device, a silicon rod and a silicon wafer. Background Art

[0002] As an important semiconductor material, silicon rods are used in the integrated circuit industry and the photovoltaic industry. In the process of drawing silicon rods, argon gas is blown from the top of the secondary chamber to the main chamber, and the silicon rods are in a low-pressure inert gas (such as argon) atmosphere. In the process of the silicon rods entering the secondary chamber from the main chamber, the argon gas flow space becomes sharply smaller, which will cause airflow turbulence, which in turn causes the silicon rods to shake, and in severe cases, it will cause wire breakage. Therefore, how to avoid wire breakage caused by airflow turbulence is a hot issue in this field. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a method for preparing a silicon rod, a silicon rod and a silicon wafer. The method for preparing the silicon rod can avoid air flow turbulence and line breakage.

[0004] To solve the above technical problems, the present application provides a method for preparing silicon rods, wherein the silicon rods are prepared in a single crystal furnace, wherein the single crystal furnace includes a main chamber and a sub-chamber connected to the main chamber, and the method includes: in a first equal-diameter stage, maintaining the furnace pressure at a first furnace pressure, wherein the silicon rods do not enter the sub-chamber and the distance between the silicon rods and the sub-chamber is greater than a preset distance; in a second equal-diameter stage, increasing the furnace pressure to a second furnace pressure, wherein the distance between the silicon rods and the sub-chamber is equal to or less than the preset distance; and in a third equal-diameter stage, reducing the furnace pressure to a third furnace pressure, wherein the length of the silicon rods entering the sub-chamber is equal to or greater than a preset length.

[0005] In one embodiment of the present application, the preparation method also includes: in the first equal-diameter stage, maintaining the flow rate of the inert gas at a first flow rate, in the second equal-diameter stage, reducing the flow rate of the inert gas to a second flow rate, and in the third equal-diameter stage, increasing the flow rate of the inert gas to a third flow rate.

[0006] In one embodiment of the present application, in the second equal diameter stage, the furnace pressure is adjusted first, and then the flow rate of the inert gas is adjusted after a first predetermined period of time from the start of adjusting the furnace pressure.

[0007] In one embodiment of the present application, in the third equal-diameter stage, the furnace pressure is adjusted first, and then the flow rate of the inert gas is adjusted after a second predetermined period of time from the start of adjusting the furnace pressure.

[0008] In an embodiment of the present application, the third flow rate is equal to the first flow rate.

[0009] In one embodiment of the present application, the third furnace pressure is equal to the first furnace pressure.

[0010] In one embodiment of the present application, in the first equal-diameter stage, the growth rate of the silicon rod is a first rate, and in the second equal-diameter stage, the growth rate of the silicon rod is a second rate, and the second rate is less than the first rate.

[0011] On the other hand, the present application also proposes a silicon rod production device, comprising: a single crystal furnace; a gas supply device configured to provide inert gas into the single crystal furnace; a pump configured to regulate the furnace pressure of the single crystal furnace; and a controller configured to execute the preparation method as described above.

[0012] On the other hand, the present application further provides a silicon rod, which is prepared according to the preparation method as described above.

[0013] On the other hand, the present application further provides a silicon wafer, which is cut from the silicon rod as described above.

[0014] Compared with the prior art, this application has the following advantages:

[0015] (1) In the second equal diameter stage, the furnace pressure is increased from the first furnace pressure in the first equal diameter stage to the second furnace pressure, so as to avoid the silicon rod shaking and wire breaking;

[0016] (2) Take measures to increase furnace pressure and reduce flow rate at the same time to better avoid silicon rod shaking and wire breakage;

[0017] (3) The growth rate of the silicon rods in the second equal diameter stage is lower than that in the first equal diameter stage. By reducing the growth rate of the silicon rods in the second equal diameter stage, the rate of change of the space between the silicon rods and the side wall of the main chamber can be reduced, which helps to avoid silicon rod shaking and wire breakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0019] Figure 1 It is a schematic flow chart of a method for preparing a silicon rod in one embodiment of the present application;

[0020] Figures 2 to 4 is a schematic diagram of the positions of silicon rods at different equal diameter stages in one embodiment of the present application;

[0021] Figure 5 It is a table of equal slopes in a proportional relationship;

[0022] Figure 6 It is a constant diameter slope table in one embodiment of the present application.

[0023] Reference numerals

[0024] Silicon rod 10 , dotted line 20 , single crystal furnace 210 , main chamber 211 and sub-chamber 212 . DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0026] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0027] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0028] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0029] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0030] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0031] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0032] Next, the silicon rod preparation method, silicon rod production device, silicon rod and silicon wafer of the present application are described through examples.

[0033] refer to Figure 1 The schematic diagram of the process of preparing a silicon rod in an embodiment shown in FIG. Figure 1 The preparation method in the embodiment includes the following steps S110 to S130.

[0034] S110: In the first equal diameter stage, the furnace pressure is maintained at the first furnace pressure, and in the first equal diameter stage, the silicon rod does not enter the auxiliary chamber and the distance between the silicon rod and the auxiliary chamber is greater than a preset distance;

[0035] S120: In the second equal diameter stage, the furnace pressure is increased to a second furnace pressure, and in the second equal diameter stage, the distance between the silicon rod and the auxiliary chamber is equal to or less than a preset distance;

[0036] S130: In the third equal diameter stage, the furnace pressure is reduced to a third furnace pressure. In the third equal diameter stage, the length of the silicon rod entering the sub-chamber is equal to or greater than a preset length.

[0037] Next, steps S110 to S130 are described in detail.

[0038] refer to Figure 2 As shown, a silicon rod 10 is prepared in a single crystal furnace 210. The single crystal furnace 210 includes a main chamber 211 and a sub-chamber 212. The sub-chamber 212 is located above the main chamber 211, and the two are connected. To more clearly understand the positional relationship between the main chamber 211 and the sub-chamber 212, Figure 2 The dotted line 20 is used to illustrate the connection between the main chamber 211 and the secondary chamber 212.

[0039] In step S110, in the first equal diameter stage, the furnace pressure is maintained at the first furnace pressure. In the first equal diameter stage, the silicon rod 10 does not enter the auxiliary chamber 212, and the distance D1 between the silicon rod 10 and the auxiliary chamber 212 is greater than the preset distance, which will be described in step S120 and will not be expanded here.

[0040] refer to Figure 2 As shown, in the first equal diameter stage, the silicon rod 10 has not yet entered the secondary chamber 212, and the distance change rate between the silicon rod 10 and the side wall of the main chamber 211 is slow. Therefore, the spatial change between the silicon rod 10 and the main chamber 211 will not cause turbulence and increase in flow rate, or even if turbulence and increase in flow rate are caused, it will not affect the quality of the silicon rod 10.

[0041] The furnace pressure of the single crystal furnace can be adjusted by a pump located below the single crystal furnace 210. The present application does not limit the first furnace pressure, and it can be adjusted according to actual production requirements.

[0042] refer to Figure 3 As shown, in step S120, in the second equal diameter stage, the furnace pressure is increased to the second furnace pressure. In the second equal diameter stage, the distance D2 between the silicon rod 10 and the auxiliary chamber 212 is equal to or less than the preset distance. The second furnace pressure is not limited in this application and can be adjusted according to actual production needs.

[0043] Specifically, as the silicon rod 10 grows, the distance between the silicon rod 10 and the auxiliary chamber 212 is Figure 2 D1 in is reduced to Figure 3D2 in (i.e., the distance between the silicon rod 10 and the auxiliary chamber 212 is reduced), the silicon rod 10 enters the second equal-diameter stage from the first equal-diameter stage, and after the silicon rod 10 enters the second equal-diameter stage, the space between the silicon rod 10 and the side wall of the main chamber 211 is sharply reduced, which will cause turbulence in the inert gas entering from the top of the auxiliary chamber 212, thereby causing the silicon rod 10 to shake. In addition, the reduction in space causes the inert gas flow rate to increase, and the inert gas with a higher flow rate will blow the molten silicon liquid surface, thereby causing the radial temperature gradient of the liquid surface to change, and ultimately causing the wire to break. In step S120, the furnace pressure is increased from the first furnace pressure in the first equal-diameter stage to the second furnace pressure, so that the flow rate of the inert gas can be slowed down and turbulence can be avoided, thereby preventing the silicon rod 10 from shaking and breaking.

[0044] The inert gas in the present application may be argon, or other inert gases, such as helium, but preferably argon, which has the advantage of low cost.

[0045] Here, the "preset distance" is explained. When the distance between the silicon rod 10 and the auxiliary chamber 212 is equal to or less than the preset distance, the silicon rod 10 may have just entered the second equal diameter stage, or may have already entered the second equal diameter stage, and the turbulence and flow rate increase caused by the reduction in the space between the silicon rod 10 and the side wall of the main chamber 211 begin to affect (or not affect) the quality of the silicon rod. For the case of "not affecting the quality of the silicon rod", increasing the furnace pressure to the second furnace pressure can prepare for the upcoming turbulence and speed that affect the quality of the silicon rod. The preset distance can be determined according to actual production conditions or related simulation software.

[0046] refer to Figure 4 As shown, in S130, in the third equal diameter stage, the furnace pressure is reduced from the second furnace pressure to the third furnace pressure to ensure the quality and growth rate of the silicon rod 10. In the third equal diameter stage, the length D3 of the silicon rod 10 entering the auxiliary chamber 212 is equal to or greater than the preset length, and the "length D3" refers to the length of the silicon rod 10 located above the dotted line 20. The "preset length" should satisfy that as the silicon rod 10 grows, the space between the silicon rod 10 and the side wall of the main chamber 211 and the side wall of the auxiliary chamber 212 remains stable and unchanged, so that the change in the space will not cause the change in the inert gas flow rate. The preset length can be determined according to actual production conditions or related simulation software.

[0047] In one embodiment, the third furnace pressure is equal to the first furnace pressure, that is, in the third equal-diameter stage, the furnace pressure is restored from the second furnace pressure to the first furnace pressure in the first equal-diameter stage.

[0048] In one embodiment, in order to better avoid turbulence and increased flow rate affecting the quality of silicon rods, the preparation method further includes the following steps S310 to S330.

[0049] S310: In the first equal diameter stage, the flow rate of the inert gas is maintained at the first flow rate. Figure 2 As shown, in the first equal diameter stage, the silicon rod 10 has not yet entered the secondary chamber 212, and the spatial change between the silicon rod 10 and the main chamber 211 will not cause turbulence and increase in flow rate, or even if turbulence and increase in flow rate are caused, it will not affect the quality of the silicon rod 10, so the flow rate of the inert gas can be kept unchanged.

[0050] S320: In the second equal diameter stage, the flow rate of the inert gas is reduced to a second flow rate. Figure 3 As shown, in the second equal diameter stage, as the silicon rod 10 grows, the distance between the silicon rod 10 and the side wall of the main chamber 211 decreases, which will cause turbulence and increased flow rate of the inert gas. To avoid turbulence and increased flow rate, in addition to taking the measure of increasing the furnace pressure to the second furnace pressure in step S120, the present application also reduces the flow rate of the inert gas from the first flow rate to the second flow rate. Taking the measures of increasing the furnace pressure and reducing the flow rate at the same time can better avoid turbulence and increased flow rate.

[0051] In the second equal diameter stage, the furnace pressure can be increased and the flow rate can be reduced at the same time, or the furnace pressure can be increased first and then the flow rate can be reduced, or the flow rate can be reduced first and then the furnace pressure can be increased. Preferably, the furnace pressure is increased first, and the flow rate of the inert gas is reduced after the first predetermined period of time from the start of increasing the furnace pressure, because the present application has found that among the above three situations, the above situation has the best effect of avoiding turbulence and increasing flow rate. The first predetermined period of time can be determined according to actual production conditions or relevant simulation software.

[0052] S330: In the third equal diameter stage, the flow rate of the inert gas is increased to a third flow rate to ensure the quality and growth rate of the silicon rod 10. In one embodiment, the third flow rate is equal to the first flow rate, that is, in the third equal diameter stage, the flow rate is restored from the third flow rate to the first flow rate of the first equal diameter stage.

[0053] In the third equal diameter stage, the furnace pressure can be reduced and the flow rate can be increased at the same time, or the furnace pressure can be reduced first and then the flow rate can be increased, or the flow rate can be increased first and then the furnace pressure can be reduced. Preferably, the furnace pressure is reduced first, and the flow rate of the inert gas is increased after the second predetermined period from the start of reducing the furnace pressure, because the present application finds that among the above three situations, the above situation has the best effect of avoiding turbulence and increasing flow rate. The second predetermined period can be determined according to actual production conditions or relevant simulation software.

[0054] In one embodiment, in order to better avoid turbulence and increased flow rate affecting the quality of silicon rods, the present application also proposes the following technical solution. In the first equal diameter stage, the growth rate of the silicon rod is a first rate, and in the second equal diameter stage, the growth rate of the silicon rod is a second rate, which is less than the first rate. By reducing the growth rate of the silicon rod in the second equal diameter stage, the rate of change of the space between the silicon rod and the side wall of the main chamber can be reduced, thereby reducing the risk of turbulence and reducing the magnitude of the increase in flow rate.

[0055] In order to more clearly understand the preparation method of the present application, an example and a comparative example are given here.

[0056] Comparative Example

[0057] refer to Figure 5 As shown in the constant diameter slope table, the argon flow rate is maintained at 100slpm from the beginning to the end of the constant diameter, and the furnace pressure is maintained at 5 torr from the beginning to the end of the constant diameter. In the process of constant diameter from 1500mm to 1600mm, the argon flow space at the lower mouth of the auxiliary chamber becomes sharply smaller, and the continuous argon flow rate will accelerate at this time, causing the silicon rod to shake. In addition, the increase in flow rate causes the argon to blow to the surface of the molten silicon, and the radial temperature gradient of the liquid surface changes, which leads to wire breakage. According to statistics, the wire breakage rate of the comparative example is between 42% and 48%.

[0058] Example

[0059] refer to Figure 6 The equal diameter slope table is shown. When the equal diameter reaches 1100mm, the argon flow rate begins to decrease and eventually decreases to the minimum value of 70slpm, so as to avoid turbulence and increase in gas flow rate caused by the reduction of the space between the silicon rod and the side wall of the main chamber. In the process of equal diameter from 1600mm to 1900mm, the argon flow rate is gradually increased and finally restored to 100slpm.

[0060] When the equal diameter reaches 900mm, the furnace pressure begins to increase, and eventually the furnace pressure is increased to 7 Torr. Figure 6 As shown, the overall gas flow rate in the single crystal furnace is slowed down, so that the argon flow when the silicon rod enters the auxiliary chamber becomes further slow. In the process of equal diameter 1500mm to 1800mm, the furnace pressure is gradually reduced and finally restored to 5 Torr.

[0061] Compared with the comparative example, the above embodiment adopts the preparation method described above, thereby avoiding the shaking of the silicon rod and reducing the wire breakage rate.

[0062] On the other hand, the present application also proposes a silicon rod production device, including: a single crystal furnace, a gas supply device, a pump and a controller, the gas supply device is configured to provide inert gas into the single crystal furnace, the pump is configured to adjust the furnace pressure of the single crystal furnace, and the controller is configured to execute the preparation method as described above. The controller can control the flow rate of the inert gas by controlling the gas supply device, and control the furnace pressure by controlling the pump.

[0063] On the other hand, the present application further provides a silicon rod, which is prepared according to the preparation method as described above.

[0064] On the other hand, the present application further provides a silicon wafer, which is cut from the silicon rod as described above.

[0065] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0066] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0067] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0068] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0069] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for preparing a silicon rod, wherein the silicon rod is prepared in a single crystal furnace, wherein the single crystal furnace comprises a main chamber and a sub-chamber connected to the main chamber, wherein: include: In the first equal diameter stage, the furnace pressure is maintained at the first furnace pressure, and in the first equal diameter stage, the silicon rod does not enter the auxiliary chamber and the distance between the silicon rod and the auxiliary chamber is greater than a preset distance; In the second equal diameter stage, the furnace pressure is increased to a second furnace pressure, and in the second equal diameter stage, the distance between the silicon rod and the auxiliary chamber is equal to or less than the preset distance; as well as In the third equal-diameter stage, the furnace pressure is reduced to a third furnace pressure. In the third equal-diameter stage, the length of the silicon rod entering the auxiliary chamber is equal to or greater than a preset length.

2. The preparation method according to claim 1, characterized in that Also includes: In the first equal-diameter stage, the flow rate of the inert gas is maintained at a first flow rate, in the second equal-diameter stage, the flow rate of the inert gas is reduced to a second flow rate, and in the third equal-diameter stage, the flow rate of the inert gas is increased to a third flow rate.

3. The preparation method according to claim 2, characterized in that: In the second equal diameter stage, the furnace pressure is adjusted first, and then the flow rate of the inert gas is adjusted after a first predetermined period of time from the start of adjusting the furnace pressure.

4. The preparation method according to claim 2, characterized in that: In the third equal diameter stage, the furnace pressure is adjusted first, and then the flow rate of the inert gas is adjusted after a second predetermined period of time from the start of adjusting the furnace pressure.

5. The preparation method according to claim 2, characterized in that: The third flow rate is equal to the first flow rate.

6. The preparation method according to claim 1, characterized in that: The third furnace pressure is equal to the first furnace pressure.

7. The preparation method according to claim 1, characterized in that: In the first equal-diameter stage, the growth rate of the silicon rod is a first rate, and in the second equal-diameter stage, the growth rate of the silicon rod is a second rate, and the second rate is less than the first rate.

8. A silicon rod production device, characterized in that: include: Single crystal furnace; A gas supply device, configured to provide inert gas into the single crystal furnace; A pump configured to adjust the furnace pressure of the single crystal furnace; as well as A controller configured to execute the preparation method according to any one of claims 1 to 7.

9. A silicon rod, characterized in that: The silicon rod is prepared according to the preparation method according to any one of claims 1 to 7.

10. A silicon wafer, characterized in that: The silicon wafer is cut from the silicon rod as claimed in claim 9.

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