Silicon material melting method, high-quality silicon single crystal rod and preparation method of high-quality silicon single crystal rod

Abstract

The invention discloses a silicon material melting method, a high-quality silicon single crystal rod and a preparation method thereof, and the silicon material melting method comprises the following steps: melting a blocky polycrystalline silicon raw material in a crucible into a silicon liquid, and carrying out stabilization treatment on the molten silicon liquid under the combined action of furnace pressure, pot rotation, a main heater and bottom power, the furnace pressure, the pot rotating power and the bottom adding power are in gradient change, and each gradient value is kept for a certain period of time so as to obtain stably molten silicon liquid; and performing crystal pulling on the stably molten silicon liquid to prepare the high-quality silicon single crystal rod. By means of convection acceleration formed by furnace pressure control and pot rotation control and heating of the crucible by the bottom heater, volatilization of gas on the surface of the silicon liquid is promoted, gas in the silicon liquid can be removed easily, and therefore the pore reject ratio of the silicon single crystal rod can be controlled optimally.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal silicon rod preparation, and in particular to a silicon material melting method, a high-quality single crystal silicon rod and a preparation method thereof. Background Art

[0002] Monocrystalline silicon is one of the important materials in the preparation of semiconductor materials and is widely used in the fields of solar panels, integrated circuits, photovoltaic cells, etc. The single crystal silicon direct pulling process is one of the commonly used processes for preparing single crystal silicon, which has the characteristics of simple process flow, high production efficiency, and good quality of prepared crystals.

[0003] The principle of the single crystal silicon Czochralski process is to place high-purity polysilicon raw materials in a quartz crucible, heat and melt them in a vacuum state and under the protection of high-purity inert gas, stabilize the crucible and silicon liquid at the melting temperature, and then insert a seed crystal fixed on the seed crystal axis into the silicon liquid to carry out the crystal pulling process; after the seed crystal and the melt are melted, the silicon liquid crystallizes on the seed crystal, and the seed crystal is slowly pulled upward, and the crystal grows at the lower end of the seed crystal, and gradually grows to form a single crystal silicon rod as the seed crystal is pulled. However, the melting temperature of the prior art is above 1420°C, at which time there is still a small amount of residual small granular polysilicon that has not been completely melted on the inner wall of the crucible, and there are bubbles gathered in the silicon liquid, which will cause more pore defects in the prepared single crystal silicon rod.

[0004] Therefore, it is urgent to propose a method for preparing a single crystal silicon rod that can reduce pore defects, so as to improve the quality of the single crystal silicon rod. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention discloses a silicon material melting method, a high-quality single crystal silicon rod and a preparation method thereof, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems in the prior art.

[0006] The present invention discloses a method for melting silicon material, comprising the following steps:

[0007] S1, placing block polycrystalline silicon raw materials into a crucible;

[0008] S2, adjusting the furnace pressure of the furnace body to a first threshold;

[0009] S3, adjusting the power of the main heater to a second threshold value, and adjusting the power of the bottom heater to a third threshold value, so as to heat the block polycrystalline silicon raw material in the crucible; maintaining the first preset time length until the block polycrystalline silicon raw material in the crucible is melted into silicon liquid;

[0010] S4, performing a stabilization treatment on the silicon liquid melted in the step S3 in a molten state to obtain a molten and stable silicon liquid.

[0011] Preferably, in step S4, the stabilization treatment process of the silicon liquid includes the following steps:

[0012] S401, adjusting the power of the main heater to a set threshold and keeping it unchanged, so that the main heater heats the crucible at a constant power; the power of the bottom heater is reduced to a fourth threshold at a first preset rate, and the power of the bottom heater is maintained at the fourth threshold for a second preset time; then the power of the bottom heater is gradually reduced to 0 kW, and the power of the bottom heater is maintained at each gradient value for a second preset time;

[0013] S402, adjusting the pot rotation to the fifth threshold value, the pot rotation changes in a step cycle with the fifth threshold value--sixth threshold value--fifth threshold value--sixth threshold value..., and the pot rotation maintains the third preset time length at each gradient value of the step cycle change until the cumulative time length of the third preset time length reaches the fourth preset time length; then adjusting the pot rotation to the seventh threshold value, the pot rotation changes in a step cycle with the seventh threshold value--eighth threshold value--seventh threshold value--eighth threshold value..., and the pot rotation maintains the fifth preset time length at each gradient value of the step cycle change until the cumulative time length of the fifth preset time length reaches the sixth preset time length;

[0014] S403, adjusting the furnace pressure to a ninth threshold value, and maintaining the furnace pressure at the ninth threshold value for a seventh preset time length; then adjusting the furnace pressure from the ninth threshold value to a tenth threshold value, and maintaining the furnace pressure at the tenth threshold value for an eighth preset time length;

[0015] S404, step S401, step S402 and step S403 are performed simultaneously to complete the stabilization treatment of the silicon liquid in a molten state.

[0016] Preferably, in step S401, the first preset rate is 10 kW / min.

[0017] Preferably, in step S401, the difference between two adjacent gradient values ​​of the power of the bottom heater is 5 kW, the fourth threshold is 15 kW, and the second preset time is 30 minutes.

[0018] Preferably, in step S402, the fifth threshold is 5 rpm, the sixth threshold is 10 rpm, the third preset time is 15 min, and the fourth preset time is 1 h.

[0019] Preferably, in step S402, the seventh threshold is 6 rpm, the eighth threshold is 12 rpm, the fifth preset time is 15 min, and the sixth preset time is 1 h.

[0020] Preferably, in step S403, the ninth threshold is 12-15 torr, the tenth threshold is 20 torr, the seventh preset time length is 1 hour, and the eighth preset time length is 1 hour.

[0021] Preferably, in step S3, the third threshold is 50-60 kW.

[0022] In addition, the present invention also discloses a method for preparing high-quality single crystal silicon rods, which further comprises the following steps after melting and stabilizing the block polycrystalline silicon raw material using the silicon material melting method as described above:

[0023] The seed crystal on the seed crystal axis is inserted into the silicon liquid to carry out the crystal pulling process; after the seed crystal and the melt are melted, the silicon liquid crystallizes on the seed crystal and slowly pulls the seed crystal upward to obtain a single crystal silicon rod.

[0024] Furthermore, the present invention discloses high-quality single crystal silicon rods prepared by the method for preparing high-quality single crystal silicon rods.

[0025] The present invention has the following beneficial effects:

[0026] The technical solution provides a silicon material melting method, a high-quality single crystal silicon rod and a preparation method thereof, wherein the melted silicon liquid is stabilized, and the furnace pressure is controlled to a gradient change of 15-20 torr or 12-20 torr, and the furnace pressure is first lowered to reduce the pressure on the silicon liquid in the crucible, and at the same time, the gradient change of the pot rotation and the bottom power is coordinated. Under the joint action of the furnace pressure, the pot rotation and the bottom power, the volatilization of the gas on the surface of the silicon liquid is promoted, thereby removing the gas in the silicon liquid, so that the pore defect rate of the single crystal silicon rod finally obtained is optimally controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present disclosure, the following briefly introduces the drawings required for use in the specific embodiments. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0028] Figure 1 It is a structural schematic diagram of a single crystal silicon growth furnace of the present invention;

[0029] Figure 2 It is a schematic diagram of the feeding scheme 1 (a) of the present invention;

[0030] Figure 3 It is a schematic diagram of feeding scheme 2 (b) of the present invention;

[0031] Figure 4 A schematic diagram of the change of the bottom power gradient during the stabilization process of the present invention;

[0032] Figure 5 It is a schematic diagram of the change of the pot rotation gradient during the stabilization treatment process of the present invention;

[0033] Figure 6 It is a schematic diagram of the change of furnace pressure gradient during the stabilization treatment process of the present invention.

[0034] Reference numerals:

[0035] 1-crucible, 11-crucible axis, 2-main heater, 3-bottom heater, 4-seed crystal, 5-silicon liquid, 6-crystal. DETAILED DESCRIPTION

[0036] The following embodiments of the technical solution of the present disclosure are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present disclosure, and are therefore only used as examples, and cannot be used to limit the protection scope of the present disclosure.

[0037] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0038] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "main", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0039] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0040] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0042] like Figure 1 As shown, the single crystal silicon growth furnace of the present invention comprises a furnace body and a crucible 1, a crucible shaft 11, a lower driving system, a main heater 2, a bottom heater 3, a seed crystal 4 and a crystal lifting mechanism arranged inside the furnace body. The upper end of the crucible shaft 11 is connected to the bottom of the crucible 1, and the lower end of the crucible shaft 11 is connected to the lower driving system. The lower driving system controls the crucible 1 to rotate through the crucible shaft 11; the crucible 1 is arranged in the main heater 2, and the bottom heater 3 is located at the bottom of the crucible 1; the polycrystalline silicon raw material is melted in the crucible 1 to form a molten silicon liquid 5, and the silicon liquid 5 crystallizes on the seed crystal 4; the crystal lifting mechanism is connected to the seed crystal 4 through the seed crystal shaft, and the crystal lifting mechanism is used to slowly pull the seed crystal 4 upward, and the crystal 6 grows at the lower end of the seed crystal 4, and gradually grows to form a single crystal silicon rod as the seed crystal 4 is pulled. The single crystal silicon growth furnace belongs to the prior art and will not be repeated here. Among them, the power of the bottom heater is defined as the bottom added power, and the lower driving system controls the crucible rotation through the crucible shaft to be defined as pot rotation.

[0043] Embodiments 1-2 of the present invention and comparative examples 1-29 provide a method for preparing a high-quality single crystal silicon rod. Specific parameters of the preparation process of the high-quality single crystal silicon rod are shown in Table 1.

[0044] A method for melting silicon material comprises the following steps:

[0045] S1, placing block polycrystalline silicon raw materials into a crucible;

[0046] S2, adjusting the furnace pressure of the furnace body to a first threshold;

[0047] S3, adjusting the power of the main heater to a second threshold value, and adjusting the power of the bottom heater to a third threshold value, so as to heat the block polycrystalline silicon raw material in the crucible; maintaining the first preset time length until the block polycrystalline silicon raw material in the crucible is melted into silicon liquid;

[0048] S4, performing a stabilization treatment on the melted silicon liquid in step S3 in a molten state to obtain a molten and stable silicon liquid; the stabilization treatment process of the silicon liquid includes the following steps:

[0049] S401. Adjust the power of the main heater to a set threshold and keep it unchanged, so that the main heater heats the crucible with a constant power; the power of the bottom heater is reduced to a fourth threshold at a first preset rate, and the power of the bottom heater is maintained at the fourth threshold for a second preset time; then the power of the bottom heater is reduced to 0kW in a gradient manner, and the power of the bottom heater is maintained at the second preset time at each gradient value; the difference between two adjacent gradient values ​​of the power of the bottom heater is 5kW, the first preset rate is 10kW / min, the fourth threshold is 15kW, and the second preset time is 30min; specifically, when the power of the bottom heater is reduced from the fourth threshold to 10kW, the power of the bottom heater is maintained at 10kW for a second preset time; the power of the bottom heater is reduced from 10kW to 5kW, and the power of the bottom heater is maintained at 5kW for a second preset time; the power of the bottom heater is reduced from 5kW to 0kW, and the power of the bottom heater is maintained at 0kW for a second preset time; Figure 4 As shown;

[0050] S402, adjust the pot rotation to the fifth threshold, the pot rotation changes in a step cycle with the fifth threshold--sixth threshold--fifth threshold--sixth threshold..., the pot rotation maintains the third preset time at each gradient value of the step cycle change, until the cumulative time of the third preset time reaches the fourth preset time; wherein the fifth threshold is 5rpm, the sixth threshold is 10rpm, the third preset time is 15min, and the fourth preset time is 1h; then adjust the pot rotation to the seventh threshold, the pot rotation changes in a step cycle with the seventh threshold--eighth threshold--seventh threshold-eighth threshold..., the pot rotation maintains the fifth preset time at each gradient value of the step cycle change, until the cumulative time of the fifth preset time reaches the sixth preset time; wherein the seventh threshold is 6rpm, the eighth threshold is 12rpm, the fifth preset time is 15min, and the sixth preset time is 1h; Figure 5 As shown;

[0051] S403, adjusting the furnace pressure to the ninth threshold, the furnace pressure is maintained at the ninth threshold for the seventh preset time; then adjusting the furnace pressure from the ninth threshold to the tenth threshold, the furnace pressure is maintained at the tenth threshold for the eighth preset time; wherein the ninth threshold is 12-15torr, the tenth threshold is 20torr, the seventh preset time is 1h, and the eighth preset time is 1h; Figure 6 As shown;

[0052] S404, step S401, step S402 and step S403 are performed simultaneously to complete the stabilization treatment of the silicon liquid in a molten state.

[0053] In step S1, the bulk polysilicon raw material is divided into small blocks and large blocks, and the volume ratio between the two is 2:3. There are two schemes for arranging the bulk polysilicon raw material in the crucible. The feeding scheme 1 (a) is that the large block polysilicon raw material in the crucible wraps the small block polysilicon raw material, that is, the small block polysilicon raw material is located in the middle of the raw material in the crucible, such as Figure 2 As shown; Feeding scheme 2 (b): small pieces of polysilicon raw materials are placed in the middle of the crucible and evenly placed along the periphery of the crucible, and the remaining positions are filled with large pieces of polysilicon raw materials, such as Figure 3 Of course, the volume ratio of the small polysilicon raw material to the large polysilicon raw material can also be other ratios, so long as a good molten silicon liquid can be formed in the crucible.

[0054] In step S2, the furnace pressure of the furnace body is 10 torr.

[0055] In step S3, the second threshold is 110kW, and the third threshold is 50-60kW. The first preset time is set based on melting the block polysilicon raw material in the crucible into silicon liquid, and is not fixedly limited, and belongs to the prior art, which will not be described here.

[0056] In step S401, the power of the main heater is adjusted to 100 kW and then kept constant, so that the main heater heats the crucible at the constant power and does not change during the stabilization process.

[0057] The embodiments of the present application also provide a method for preparing high-quality single crystal silicon rods. After the block polycrystalline silicon raw material is melted and stabilized by the silicon material melting method as described above, the seed crystal on the seed crystal axis is inserted into the silicon liquid to carry out the crystal pulling process. After the seed crystal and the melt are melted, the silicon liquid crystallizes on the seed crystal, and the seed crystal is slowly pulled upward to obtain a single crystal silicon rod.

[0058] The performance test is shown in Table 1.

[0059] Test standard:

[0060] (1) Porosity defects are detected using an ultrasonic flaw detector.

[0061] Table 1

[0062]

[0063]

[0064]

[0065] Note: when the crucible speed in Table 1 is a specific value, for example, the pot speed is 2rpm, it means that the crucible rotates at 2rpm for the fourth preset time plus the sixth preset time; when the crucible rotates into two step parameter changes, for example, the pot rotates into 4-10rpm, it means that the crucible rotates first at 4rpm for the fourth preset time, and then at 10rpm for the sixth preset time; when the crucible rotates into four step parameter changes, for example, the pot rotates into 5-10|6-12rpm, it means that the pot rotates first at 5rpm--10rpm--5rpm--10rpm... in a step cycle, and the pot rotates at each gradient value of the step cycle change for the third preset time until the cumulative time of the third preset time reaches the fourth preset time; then the pot rotates at 6rpm--12rpm--6rpm--12rpm... in a step cycle, and the pot rotates at each gradient value of the step cycle change for the fifth preset time until the cumulative time of the fifth preset time reaches the sixth preset time.

[0066] Secondly, when the bottom added power is a specific value, for example, the bottom added power is 15kW, it means that the bottom added power is 15kW to keep the bottom heater working during the entire stabilization process. Figure 4 As can be seen from the above, the working time is 2h; when the bottom power changes in two step parameters, for example, the bottom power is 5-0kW, it means that the bottom power keeps the bottom heater at 5kW for half of the working time in the entire stabilization process, and then keeps the bottom heater at 0kW for the remaining half of the working time in the entire stabilization process; when the bottom power changes in four step parameters, for example, the bottom power is 15-10-5-0kW, the power of the bottom heater is maintained at each gradient value for the second preset time.

[0067] When the furnace pressure is a specific numerical value, for example, when the furnace pressure is 15torr, it means that the furnace pressure is maintained at 15torr for the seventh preset time plus the eighth preset time; when the furnace pressure changes in two step parameters, for example, when the furnace pressure is 15-20torr, it means that the furnace pressure is first maintained at 15torr for the seventh preset time and then at 20torr for the eighth preset time.

[0068] From the analysis of comparative examples 22-29, it can be seen that after the polysilicon raw material is put into the crucible and melted into silicon liquid according to the feeding scheme 1 (a), as the pot rotation increases from 2rpm to 12rpm, the pore defect rate of the single crystal silicon rod finally obtained shows a downward trend. When the pot rotation is adjusted to a gradient cycle change, the pore defect rate of the single crystal silicon rod is further reduced. When the pot rotation changes in a gradient cycle of 5-10|6-12rpm, the pore defect rate of the single crystal silicon rod is optimally controlled. When the pot rotation changes according to the gradient cycle, the convection speed of the silicon liquid in the crucible changes back and forth between fast and slow. The change in the convection speed of the silicon liquid can increase the friction of the silicon liquid on the inner wall of the crucible. A small amount of residual small granular polysilicon is forced to break away from the inner wall of the crucible and melt quickly in the silicon liquid, thereby achieving the problem of removing a small amount of residual small granular polysilicon on the inner wall of the crucible. In addition, when the pot rotation changes according to the gradient cycle, the pot rotation can change the convection speed of the silicon liquid in the crucible. By increasing the free convection speed of the silicon liquid, the convection of the silicon liquid becomes active, thereby removing the bubbles remaining in the silicon liquid to reduce the pores generated in the single crystal silicon rod.

[0069] From the analysis of comparative examples 14-21, it can be seen that after the polysilicon raw material is put into the crucible and melted into silicon liquid according to the feeding scheme 2 (b), as the pot rotation increases from 2rpm to 12rpm, the pore defect rate of the single crystal silicon rod finally obtained shows a downward trend. When the pot rotation is adjusted to a gradient cycle change, the pore defect rate of the single crystal silicon rod is further reduced. When the pot rotation changes in a gradient cycle of 5-10|6-12rpm, the pore defect rate of the single crystal silicon rod is optimally controlled.

[0070] By comparing Comparative Examples 14-21 and Comparative Examples 14-21, it can be seen that there is no significant difference in the porosity defect rate of the single crystal silicon rods prepared by feeding scheme 1 (a) and feeding scheme 2 (b); therefore, in practical applications, both feeding methods are feasible.

[0071] Analysis of comparative example 5-13 shows that the pot rotation of comparative example 5-13 changes according to the gradient cycle of 5-10|6-12rpm. When the bottom power is reduced from 20kW to 0kW, the pore defect rate of the single crystal silicon rod finally obtained shows an overall upward trend, indicating that high bottom power is beneficial to reduce the bubbles in the silicon liquid. When the bottom power is adjusted to a gradient change, the pore defect rate of the single crystal silicon rod is further reduced. During the stabilization treatment of the silicon liquid, the temperature of the crucible and the silicon liquid is increased by increasing the power of the bottom heater. Due to the increase in the overall silicon liquid temperature, the buoyancy of the bubbles in the silicon liquid increases and overflows upward, making the removal speed of the bubbles in the silicon liquid faster. When the bottom power changes in a gradient of 15-10-5-0kW, the removal effect of the bubbles in the silicon liquid is optimally controlled, and the pore defect rate of the single crystal silicon rod is optimally controlled.

[0072] Analysis of Example 1-2 and Comparative Example 1-4 shows that the pot rotation of Example 1-2 and Comparative Example 1-4 changes according to the gradient cycle of 5-10|6-12rpm, and the bottom power of Example 1-2 and Comparative Example 1-4 changes according to the gradient of 15-10-5-0kW. When the furnace pressure is reduced from 25torr to 12torr, the pore defect rate of the single crystal silicon rod finally obtained shows a downward trend, indicating that a lower furnace pressure is beneficial to reducing the bubbles in the silicon liquid. When the furnace pressure is adjusted to a gradient change, the pore defect rate of the single crystal silicon rod is further reduced. When the furnace pressure changes in a gradient of 15-20torr or 12-20torr, by first reducing the furnace pressure to reduce the pressure on the silicon liquid in the crucible, and at the same time cooperating with the pot rotation and the bottom power, the bubbles inside the silicon liquid can be promoted to float to the surface of the silicon liquid faster, and finally volatilize from the surface of the silicon liquid, thereby removing the gas in the silicon liquid, so that the pore defect rate of the single crystal silicon rod finally obtained reaches the optimal control of 0.05%.

[0073] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present disclosure, and they should all be included in the scope of the claims and specification of the present disclosure.

Claims

1. A method for melting silicon material, characterized in that: The steps include: S1, placing block polycrystalline silicon raw materials into a crucible; S2, adjusting the furnace pressure of the furnace body to a first threshold; S3, adjusting the power of the main heater to a second threshold value, and adjusting the power of the bottom heater to a third threshold value, so as to heat the block polycrystalline silicon raw material in the crucible; maintaining the first preset time length until the block polycrystalline silicon raw material in the crucible is melted into silicon liquid; S4, performing a stabilization treatment on the silicon liquid melted in the step S3 in a molten state to obtain a molten and stable silicon liquid.

2. The method for melting silicon material according to claim 1, characterized in that: In step S4, the stabilization treatment process of the silicon liquid includes the following steps: S401, adjusting the power of the main heater to a set threshold and keeping it unchanged, so that the main heater heats the crucible at a constant power; the power of the bottom heater is reduced to a fourth threshold at a first preset rate, and the power of the bottom heater is maintained at the fourth threshold for a second preset time; then the power of the bottom heater is gradually reduced to 0 kW, and the power of the bottom heater is maintained at each gradient value for a second preset time; S402, adjusting the pot rotation to the fifth threshold value, the pot rotation changes in a step cycle with the fifth threshold value--sixth threshold value--fifth threshold value--sixth threshold value..., and the pot rotation maintains the third preset time length at each gradient value of the step cycle change until the cumulative time length of the third preset time length reaches the fourth preset time length; then adjusting the pot rotation to the seventh threshold value, the pot rotation changes in a step cycle with the seventh threshold value--eighth threshold value--seventh threshold value--eighth threshold value..., and the pot rotation maintains the fifth preset time length at each gradient value of the step cycle change until the cumulative time length of the fifth preset time length reaches the sixth preset time length; S403, adjusting the furnace pressure to a ninth threshold value, and maintaining the furnace pressure at the ninth threshold value for a seventh preset time length; then adjusting the furnace pressure from the ninth threshold value to a tenth threshold value, and maintaining the furnace pressure at the tenth threshold value for an eighth preset time length; S404, step S401, step S402 and step S403 are performed simultaneously to complete the stabilization treatment of the silicon liquid in a molten state.

3. The method for melting silicon material according to claim 2, characterized in that: In step S401, the first preset rate is 10 kW / min.

4. The method for melting silicon material according to claim 2, characterized in that: In the step S401, the difference between two adjacent gradient values ​​of the power of the bottom heater is 5 kW, the fourth threshold is 15 kW, and the second preset time is 30 minutes.

5. The method for melting silicon material according to claim 2, characterized in that: In step S402, the fifth threshold is 5 rpm, the sixth threshold is 10 rpm, the third preset time is 15 minutes, and the fourth preset time is 1 hour.

6. The method for melting silicon material according to claim 2, characterized in that: In step S402, the seventh threshold is 6 rpm, the eighth threshold is 12 rpm, the fifth preset time is 15 minutes, and the sixth preset time is 1 hour.

7. The method for melting silicon material according to claim 2, characterized in that: In the step S403, the ninth threshold is 12-15 torr, the tenth threshold is 20 torr, the seventh preset time length is 1 hour, and the eighth preset time length is 1 hour.

8. The method for melting silicon material according to claim 1, characterized in that: In step S3, the third threshold is 50-60 kW.

9. A method for preparing high-quality single crystal silicon rods, characterized in that: After the block polycrystalline silicon raw material is melted and stabilized by the silicon material melting method as described in any one of items 1 to 8, the method further comprises the following steps: The seed crystal on the seed crystal axis is inserted into the silicon liquid to carry out the crystal pulling process; after the seed crystal and the melt are melted, the silicon liquid crystallizes on the seed crystal and slowly pulls the seed crystal upward to obtain a single crystal silicon rod.

10. A high-quality single crystal silicon rod prepared by the method for preparing a high-quality single crystal silicon rod according to claim 9.

Images