Preparation method for crystal bar, and crystal bar

Abstract

The present invention belongs to the technical field of single crystal growth. Disclosed herein are a preparation method for a crystal bar, and a crystal bar. The preparation method for a crystal bar of the present application comprises a shoulder transformation step and an equal-diameter step. During the shoulder transformation step and / or the equal-diameter step, a hydrogen-containing gas is introduced, wherein the hydrogen-containing gas comprises hydrogen, the mass of hydrogen is mH, and the total mass of the hydrogen-containing gas is mtotal, which satisfy: mH / mtotal≤30%. In the present application, the introduction of hydrogen during a preparation process of the crystal bar can reduce the oxygen content of single crystals, thereby reducing internal defects of single crystal silicon; and when a boron-doped single crystal is drawn, the formation of a boron-oxygen complex can be reduced, thereby preventing the phenomenon of efficiency decline of a battery piece.

Description

A method for preparing a crystal rod and a crystal rod Technical Field

[0001] The present application belongs to the field of single crystal growth technology, and specifically relates to a method for preparing a crystal rod and a crystal rod. Background Art

[0002] The characteristics of Czochralski single crystal silicon products include oxygen content, minority carrier lifetime, carbon content, resistivity, defects, dislocations, etc.; excessively high oxygen content in the head of the single crystal product or too low lifetime at the tail of the single crystal will affect product quality. Technical issues

[0003] The main source of oxygen impurities in single crystal silicon is the incorporation of SiO2 produced by the reaction between the quartz crucible and the silicon raw material. The oxygen element improves the mechanical strength of the silicon wafer to a certain extent. However, in the later production process, a large amount of oxygen impurity precipitation (>16ppma) will cause the silicon wafer to warp. At the same time, it will also cause a large number of secondary defects, and to a certain extent affect the performance of the battery and play a certain destructive role. Technical Solutions

[0004] The embodiment of the present application provides a method for preparing a crystal rod, comprising a shoulder turning step and a diameter equalizing step, wherein a hydrogen-containing gas is introduced during the shoulder turning step and / or the diameter equalizing step; the hydrogen-containing gas comprises hydrogen, and the mass of the hydrogen is m H , the total mass of the hydrogen-containing gas is m 总 , satisfy: m H / m 总 ≤30%.

[0005] In some embodiments, the method for preparing the crystal rod further includes melting, welding, seeding, and shoulder expansion steps, and the hydrogen-containing gas is introduced into any one or more of the melting, welding, seeding, and shoulder expansion steps.

[0006] In some embodiments, the shoulder expansion step includes a stage in which the shoulder grows to a target shoulder length, and the shoulder expansion step includes a stage in which the shoulder grows to a target shoulder length. In the shoulder expansion step, the shoulder length is L1, and the target shoulder length is L; in the stage of 0<L1≤0.3L, the first crucible is controlled to rotate V1; in the stage of 0.3L<L1≤L, the second crucible is controlled to rotate V2; satisfying: V1>V2.

[0007] In some embodiments, the first crucible rotation speed V1 ranges from 9 rpm to 15 rpm.

[0008] In some embodiments, the second crucible rotation speed V2 ranges from 7 rpm to 12 rpm.

[0009] In some embodiments, in the shoulder expansion step, the shoulder length during the shoulder expansion process is L1, and the target shoulder length is L; wherein, in the stage of 0<L1≤0.3L, the time for passing the hydrogen-containing gas is T1; in the stage of 0.3L<L1≤0.6L, the time for passing the hydrogen-containing gas is T2; in the stage of 0.6L<L1≤L, the time for passing the hydrogen-containing gas is T3; the total time for passing the hydrogen-containing gas in the shoulder expansion step is T 扩肩 , T 扩肩 =T1+T2+T3; satisfies: T2<T1.

[0010] In some embodiments, T2 < T3 is satisfied.

[0011] In some embodiments, it satisfies: T3<T1.

[0012] In some embodiments, in the equal diameter step, in the stage of 0V4, H1 is the pulling length, and H is the total length of the target crystal rod.<h1>

[0013] In some embodiments, the equalizing step includes a first equalizing stage, wherein the first equalizing stage is: 0

[0014] In some embodiments, the equal-diameter step includes a second equal-diameter stage, a third equal-diameter stage and a fourth equal-diameter stage; the second equal-diameter stage is a 0.11H

[0015] In some embodiments, the time for passing the hydrogen-containing gas into the first equal-diameter stage is T4, the time for passing the hydrogen-containing gas into the second equal-diameter stage is T5, the time for passing the hydrogen-containing gas into the third equal-diameter stage is T6, and the time for passing the hydrogen-containing gas into the fourth equal-diameter stage is T7;

[0016] Among them, T4<T5=T7<T6.

[0017] In some embodiments, the hydrogen content of the hydrogen-containing gas in the first isodiametric stage is higher than the hydrogen content of the hydrogen-containing gas in the second isodiametric stage, the third isodiametric stage, and the fourth isodiametric stage.

[0018] ​​In some embodiments, the melting step includes feeding, re-feeding and volatilization steps, and the feeding temperature is 300°C to 1600°C.

[0019] In some embodiments, the re-injection temperature is 1400°C to 1600°C.

[0020] In some embodiments, the volatilization temperature is 1460°C to 1480°C.

[0021] In some embodiments, the feeding time is 4 hours to 12 hours.

[0022] In some embodiments, the re-administration time is 3 hours to 10 hours.

[0023] In some embodiments, the volatilization time is 0.3 h to 3 h.

[0024] In some embodiments, a hydrogen-containing gas is introduced into the melting step, and the hydrogen content in the hydrogen-containing gas is ≤30%.

[0025] In some embodiments, hydrogen-containing gas is introduced during the feeding stage, and the hydrogen content is ≤30%.

[0026] In some embodiments, the hydrogen-containing gas introduced during the re-injection stage has a hydrogen content of ≤20%, and the hydrogen-containing gas introduced during the volatilization stage has a hydrogen content of ≤20%.

[0027] In some embodiments, the welding step includes a high temperature preheating stage and a low temperature welding stage.

[0028] In some embodiments, the temperature in the high temperature preheating stage is 1457°C to 1475°C.

[0029] In some embodiments, the temperature of the low temperature welding stage is 1449°C to 1457°C.

[0030] In some embodiments, the crucible rotation speed in the welding step ranges from 6 rpm to 15 rpm.

[0031] In some embodiments, the high temperature preheating stage lasts for 0.1 h to 1 h.

[0032] In some embodiments, the low-temperature welding stage lasts for 0.1 h to 4 h.

[0033] In some embodiments, hydrogen-containing gas is introduced into the welding step, and the hydrogen content in the hydrogen-containing gas is ≤15%.

[0034] In some embodiments, the content of boron and / or gallium in the raw materials for preparing the crystal rod is 0.007 mg / g to 0.8 mg / g.

[0035] In some embodiments, the phosphorus content in the raw material for preparing the crystal rod is 0.001 mg / g to 0.01 mg / g.

[0036] The present application provides a crystal rod, which is prepared by the crystal rod method. Beneficial effects

[0037] The present application provides a method for preparing a crystal rod, comprising a shoulder turning step and a diameter equalizing step, wherein a hydrogen-containing gas is introduced during the shoulder turning step and / or the diameter equalizing step; the hydrogen-containing gas comprises hydrogen, and the mass of the hydrogen is m H , the total mass of hydrogen-containing gas is mtotal, satisfying: m H / m 总 ≤30%. This application reduces the oxygen content of the single crystal by introducing hydrogen during the crystal rod preparation process, thereby reducing the defects inside the single crystal silicon. When pulling the boron-doped single crystal, the formation of boron-oxygen complexes can be reduced, preventing the efficiency decline of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0039] FIG1 is a schematic diagram of the crystal rod preparation structure in an embodiment of the present application;

[0040] Description of the drawings: 100 - crystal rod, 200 - shoulder, 300 - crucible.

[0041] Implementation Methods of the Application

[0042] The following, in conjunction with the accompanying drawings, provides a clear and complete description of the technical solutions in the embodiments of the present application. It should be noted that the described embodiments are only a portion of the embodiments of the present application, and not all of the embodiments. All other embodiments derived by persons skilled in the art based on the embodiments of the present application without inventive effort are within the scope of protection of the present application. Furthermore, in the description of the present application, the term "including" means "including but not limited to." The terms "first," "second," and "third," etc., are used merely as designations and do not impose numerical requirements or establish a sequence. Various embodiments of the present application may be presented in the form of a range. It should be understood that describing in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application. Therefore, the range description should be considered to specifically disclose all possible subranges and individual numerical values ​​within the range. For example, a range description of 1 to 6 should be considered to specifically disclose subranges, such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., as well as individual numerical values ​​within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

[0043] The main source of oxygen impurities in single crystal silicon is the reaction between the quartz crucible and the silicon raw material to produce SiO fusion. At a high temperature of 1400℃, the silicon melt and the quartz crucible undergo a chemical reaction:

[0044] Si+SiO2→2SiO SiO+Si→O

[0045] At high temperatures, most of the SiO2 evaporates from the free surface of the melt, and after the SiO2 in the scattered boundary layer at the solid-liquid interface decomposes, oxygen atoms will enter the crystal rod by segregation.

[0046] The presence of oxygen in silicon improves the mechanical strength of silicon wafers to a certain extent. During post-processing, high temperatures can form oxygen precipitation and corresponding defects, which can reduce dispersed carrier recombination centers to a certain extent, improving the efficiency of solar cells and the photoelectric conversion efficiency. However, during the post-production process, large amounts of oxygen impurity precipitation (>16ppma) can cause silicon wafer warping and create a large number of secondary defects, which can affect the performance of the battery to a certain extent and have a certain destructive effect.

[0047] The present application replaces the argon gas introduced into the furnace during the original single crystal growth process with a hydrogen-containing gas, which can reduce the oxygen content of the single crystal and thus reduce the defects inside the single crystal silicon. In some embodiments, the present application provides a method for preparing a crystal rod, including a shoulder turning step and a diameter equalizing step. During the shoulder turning step and / or the diameter equalizing step, a hydrogen-containing gas is introduced; the hydrogen-containing gas includes hydrogen, and the mass of the hydrogen is m H , the total mass of hydrogen-containing gas is m 总 , satisfy: m H / m 总 ≤30%.

[0048] In some embodiments, the hydrogen-containing gas is a mixture of hydrogen and argon.

[0049] In some embodiments, the hydrogen-containing gas is a mixture of hydrogen and nitrogen.

[0050] The present application introduces hydrogen as a protective gas during the silicon single crystal pulling process, places the silicon crystal in a vacuum heating furnace, and during the heat treatment process of the silicon crystal, introduces the protective gas into the vacuum heating furnace and flows through the surface of the silicon crystal. The protective gas is a gas containing hydrogen atoms. After the silicon crystal is heat-treated using the method of the present application using a mixture of hydrogen atom-containing gas and an inert gas, the minority carrier lifetime of the silicon crystal is significantly improved due to the passivation and gettering effects of hydrogen on impurities and defects in the silicon crystal. At the same time, the uniformity of the radial and axial resistivity distribution of the silicon crystal is adjusted, making the resistivity of the silicon crystal more uniform in the radial and longitudinal directions of the crystal. The method of the present application is simple to operate, easy to industrialize, and can significantly improve the quality of the product.

[0051] In some embodiments, based on the total mass of the hydrogen-containing gas, the mass percentage (%) of hydrogen in the hydrogen-containing gas is any value of 5, 10, 15, 20, 25, 30, or a range of any two values.

[0052] In some embodiments, during the crystal rod preparation process, argon gas or hydrogen-containing gas is introduced, and the flow rate of the introduced gas is 20 slpm to 220 slpm.

[0053] In some embodiments, the gas flow rate (slpm) is any value of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, or a range consisting of any two values.

[0054] In some embodiments, the crystal rod preparation further includes the steps of melting, welding, seeding, and shoulder expansion, and hydrogen-containing gas is introduced into any one or several of the steps of melting, welding, seeding, and shoulder expansion.

[0055] In some embodiments, the shoulder expansion step includes expanding the shoulder to a target shoulder length stage, as shown in FIG1 , wherein the shoulder length during the shoulder expansion process is L1, and the target shoulder length is L; in the 0<L1≤0.3L stage, the first crucible is controlled to rotate to V1; in the 0.3L<L1≤L stage, the second crucible is controlled to rotate to V2; satisfying: V1>V2.

[0056] In some embodiments, the first crucible rotation speed V1 ranges from 9 r / min to 15 r / min, such as the first crucible rotation speed V1 (r / min) is any value among 9, 10, 11, 12, 13, 14, 15 or a range consisting of any two values.

[0057] In some embodiments, the second crucible rotation speed V2 ranges from 7 r / min to 12 r / min, and the value of the second crucible rotation speed V2 (r / min) is any value of 7, 8, 9, 10, 11, 12 or a range consisting of any two values.

[0058] In some embodiments, in the shoulder expansion step, the shoulder length during the shoulder expansion process is L1, and the target shoulder length is L; wherein, in the stage of 0<L1≤0.3L, the time for passing the hydrogen-containing gas is T1; in the stage of 0.3L<L1≤0.6L, the time for passing the hydrogen-containing gas is T2; in the stage of 0.6L<L1≤L, the time for passing the hydrogen-containing gas is T3; the total time for passing the hydrogen-containing gas in the shoulder expansion step is T 扩肩 , T 扩肩 =T1+T2+T3; satisfies: T2<T1.

[0059] In some embodiments, T2 < T3 is satisfied.

[0060] In some embodiments, it satisfies: T3<T1.

[0061] In some embodiments, the range of T1 is 0.6h to 1.8h, such as the value of T1(h) is any value of 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or a range consisting of any two values.

[0062] In some embodiments, the range of T2 is 0.3h to 1.5h, such as the value of T2(h) is any value of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a range consisting of any two values.

[0063] In some embodiments, the range of T3 is 0.5h to 1.6h, such as the value of T3(h) is any value of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or a range consisting of any two values.

[0064] In some embodiments, in the stage of 0<L1≤0.3L, the hydrogen content in the hydrogen-containing gas is ≤15%, such as the hydrogen content (%) in the hydrogen-containing gas is any value among 5, 10, 15 or a range consisting of any two values.

[0065] In some embodiments, in the stage of 0.3L<L1≤0.6L, the hydrogen content in the hydrogen-containing gas is ≤15%, such as the hydrogen content (%) in the hydrogen-containing gas is any value among 5, 10, 15 or a range consisting of any two values.

[0066] In some embodiments, in the stage of 0.6L<L1≤L, the hydrogen content in the hydrogen-containing gas is ≤15%, such as the hydrogen content (%) in the hydrogen-containing gas is any value among 5, 10, 15 or a range consisting of any two values.

[0067] In some embodiments, in the equal diameter step, in the stage of 0V4, H1 is the pulling length, and H is the total length of the target crystal rod.<h1>

[0068] As shown in Figure 1, during the crystal growth process, the pulling length H1 is the length from the crucible liquid level to the top of the crystal ingot. The target total ingot length H is the total length of the crystal ingot after the crystal growth is completed.

[0069] In some embodiments, the third crucible speed V3 ranges from 7 r / min to 12 r / min, and the value of the third crucible speed V3 (r / min) is any value of 7, 8, 9, 10, 11, 12 or a range consisting of any two values.

[0070] In some embodiments, the range of the fourth crucible speed V4 is 6 r / min to 10 r / min, and the value of the fourth crucible speed V4 (r / min) is any value among 6, 7, 8, 9, 10 or a range consisting of any two values.

[0071] In some embodiments, the equalizing step includes a first equalizing stage, which is: 0

[0072] In some embodiments, the equal-diameter step includes a second equal-diameter stage, a third equal-diameter stage and a fourth equal-diameter stage; the second equal-diameter stage is a 0.11H ​​

[0073] In some embodiments, the time for introducing hydrogen-containing gas in the first equal-diameter stage is T4, the time for introducing hydrogen-containing gas in the second equal-diameter stage is T5, the time for introducing hydrogen-containing gas in the third equal-diameter stage is T6, and the time for introducing hydrogen-containing gas in the fourth equal-diameter stage is T7.

[0074] In some embodiments, hydrogen-containing gas is introduced into the first isodiametric stage, the second isodiametric stage, the third isodiametric stage, and the fourth isodiametric stage.

[0075] In some embodiments, the value range of T4 is 5h to 9h, such as the value of T4(h) is any value of 5, 6, 7, 8, 9 or a range consisting of any two values.

[0076] In some embodiments, the value range of T5 is 8h to 16h, such as the value of T5(h) is any value among 8, 9, 10, 11, 12, 13, 14, 15, 16 or a range consisting of any two values.

[0077] In some embodiments, the value range of T6 is 16h to 24h, such as the value of T6(h) is any value among 16, 17, 18, 19, 20, 21, 22, 23, 24 or a range consisting of any two values.

[0078] In some embodiments, the value range of T7 is 9h to 15h, such as the value of T7(h) is any value among 9, 10, 11, 12, 13, 14, 15 or a range consisting of any two values.

[0079] In some embodiments, the following is satisfied: T4<T5=T7<T6.

[0080] In some embodiments, the hydrogen content in the hydrogen-containing gas introduced into the first equal-diameter stage is ≤15%, such as the hydrogen content (%) in the hydrogen-containing gas introduced into the first equal-diameter stage is any value among 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range consisting of any two values.

[0081] In some embodiments, the hydrogen content in the hydrogen-containing gas introduced into the second equal-diameter stage is ≤10%, such as the hydrogen content (%) in the hydrogen-containing gas introduced into the second equal-diameter stage is any value among 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range consisting of any two values.

[0082] In some embodiments, the hydrogen content in the hydrogen-containing gas introduced into the third equal-diameter stage is ≤10%, such as the hydrogen content (%) in the hydrogen-containing gas introduced into the third equal-diameter stage is any value of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range consisting of any two values.

[0083] In some embodiments, the hydrogen content in the hydrogen-containing gas introduced into the fourth equal-diameter stage is ≤10%, such as the hydrogen content (%) in the hydrogen-containing gas introduced into the fourth equal-diameter stage is any value of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range consisting of any two values.

[0084] In some embodiments, the hydrogen content of the hydrogen-containing gas in the first isometric stage is higher than the hydrogen content in the second isometric stage, the third isometric stage, and the fourth isometric stage.

[0085] In some embodiments, the hydrogen content in this application refers to the mass percentage of hydrogen in the hydrogen-containing gas.

[0086] In some embodiments, the melting step includes feeding, re-feeding and volatilization steps, and the feeding temperature is 300°C to 1600°C, such as the feeding temperature (°C) is any value of 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600 or a range consisting of any two values.

[0087] In some embodiments, the re-injection temperature is 1400° C. to 1600° C., such as the re-injection temperature (° C.) is any value among 1400, 1450, 1500, 1550, 1600, or a range consisting of any two values.

[0088] In some embodiments, the volatilization temperature is 1460° C. to 1480° C., for example, the volatilization temperature (° C.) is any value among 1460, 1470, 1480° C. or a range consisting of any two values.

[0089] In some embodiments, the feeding time is 4 hours to 12 hours, such as the feeding time (h) is any value of 4, 5, 6, 7, 8, 9, 10, 11, 12 or a range consisting of any two values.

[0090] In some embodiments, the re-investment time is 3 hours to 10 hours, such as the re-investment time (h) is any value of 3, 4, 5, 6, 7, 8, 9, 10 or a range consisting of any two values.

[0091] In some embodiments, the volatilization time is 0.3 to 3 hours, for example, the volatilization time (h) is any value of 0.3, 0.5, 1, 1.5, 2, 2.5, 3, or a range consisting of any two values.

[0092] In some embodiments, hydrogen-containing gas is introduced into the melting step, and the hydrogen content in the hydrogen-containing gas is ≤30%, such as the hydrogen content (%) is any value of 0, 5, 10, 15, 20, 25, 30 or a range consisting of any two values.

[0093] In some embodiments, hydrogen-containing gas is introduced during the feeding stage, and the hydrogen content is ≤30%, such as the hydrogen content (%) is any value of 0, 5, 10, 15, 20, 25, 30 or a range consisting of any two values.

[0094] In some embodiments, during the re-injection phase, hydrogen-containing gas is introduced, and the hydrogen content (%) is ≤20%, such as the hydrogen content (%) is any value among 0, 5, 10, 15, 20 or a range consisting of any two values.

[0095] In some embodiments, hydrogen-containing gas is introduced during the volatilization stage, and the hydrogen content is ≤20%, such as the hydrogen content (%) is any value among 0, 5, 10, 15, 20 or a range consisting of any two values.

[0096] In some embodiments, the welding step includes a high temperature preheating stage and a low temperature welding stage.

[0097] In some embodiments, the temperature of the high temperature preheating stage is 1457°C to 1475°C, such as the temperature (°C) of the high temperature preheating stage is any value of 1457, 1460, 1465, 1470, 1475 or a range consisting of any two values.

[0098] In some embodiments, the temperature of the low temperature welding stage is 1449°C to 1457°C, such as the temperature (°C) of the low temperature welding stage is any value of 1449, 1450, 1451, 1452, 1453, 1454, 1455, 1456, 1457 or a range consisting of any two values.

[0099] In some embodiments, the crucible speed in the welding step ranges from 9 r / min to 15 r / min, such as the crucible speed (r / min) is any value among 9, 10, 11, 12, 13, 14, 15 or a range consisting of any two values.

[0100] In some embodiments, the high temperature preheating stage duration is 0.1h to 1h, such as the high temperature preheating stage duration (h) is any value of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or a range consisting of any two values.

[0101] In some embodiments, the duration of the low temperature welding stage is 0.1h to 4h, such as the duration of the low temperature welding stage (h) is any value of 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 or a range consisting of any two values.

[0102] In some embodiments, hydrogen-containing gas is introduced into the welding step, and the hydrogen content in the hydrogen-containing gas is ≤15%, such as the hydrogen content (%) is any value among 0, 5, 10, 15 or a range consisting of any two values.

[0103] In some embodiments, the content of boron and / or gallium in the raw materials for preparing the crystal rod is 0.007 mg / g to 0.8 mg / g.

[0104] In some embodiments, the phosphorus content in the raw materials for preparing the crystal rod is 0.001 mg / g to 0.01 mg / g.

[0105] In some embodiments, the boron content (mg / g) in the raw material of single crystal silicon is any value of 0.007, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or a range consisting of any two values.

[0106] In some embodiments, the gallium content (mg / g) in the raw material of single crystal silicon is any value of 0.007, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or a range consisting of any two values.

[0107] In some implementations, the phosphorus content (mg / g) in the single crystal silicon raw material is any value among 0.001, 0.005, 0.01, or a range consisting of any two values.

[0108] In this application, resistivity is the ratio of the product of the resistance and the cross-sectional area in the crystal rod to the length, that is, the material formed by silicon atoms in an arranged form. Phosphorus-doped silicon is n-type. The more phosphorus-doped silicon is, the more free electrons there are, the stronger the conductivity is, and the lower the resistivity is. On the contrary, boron-doped silicon is p-type. The more boron-doped silicon is, the more holes can be replaced by silicon, the stronger the conductivity is, and the lower the resistivity is. The smaller the resistivity concentration, that is, the head-to-tail ratio, the better, which is beneficial to the quality compliance rate of the crystal rod and directly affects the conversion efficiency of the solar cell.

[0109] In this application, the content of boron, gallium or phosphorus refers to the ratio of the mass of boron, gallium or phosphorus, gallium or phosphorus element to the mass of single crystal silicon raw material. Taking boron element as an example, the mass of boron element is M1mg, the mass of single crystal silicon raw material is M2g, and the boron content = M1 / M2mg / g.

[0110] The present application introduces hydrogen during the crystal rod preparation process, especially when pulling boron-doped single crystals, to reduce the formation of boron-oxygen complexes and prevent efficiency degradation in the battery cell.

[0111] Accordingly, the present application provides a crystal rod prepared by the above-mentioned preparation method. The present application reduces the oxygen content of the single crystal silicon by introducing hydrogen-containing gas during the crystal rod preparation process, thereby reducing the defects inside the single crystal silicon, improving the resistivity and minority carrier lifetime of the crystal tail, and then increasing the length of the pulled crystal rod, reducing the total proportion of time in the non-equal diameter state, and improving the output; at the same time, it can improve the conversion efficiency of solar cells; the present application can reduce the generation and accumulation of oxides in the single crystal furnace, reduce the time and number of oxide cleaning after shutdown, reduce manual workload, and enable the single crystal furnace to start production faster, saving time and increasing output. The present application further obtains high-quality single crystal silicon products by controlling the parameters in the crystal rod preparation process, which are used to improve the efficiency of downstream battery components.

[0112] Example 1:

[0113] Melt: 500 kg of raw material was added to the furnace, consisting of 50% virgin polysilicon and 50% gallium-containing recycled material. The virgin polysilicon contained 0.5 mg of boron and 0.1 mg of phosphorus. The recycled material contained 5.5 mg of boron, and the crucible bottom material contained 0.9 mg of phosphorus. 86 g of boron was added as a dopant.

[0114] The material was melted at a temperature of 1500° C. for 8 hours, and hydrogen-containing gas was introduced at a flow rate of 110 slpm. The hydrogen content of the hydrogen-containing gas was 20%, the argon content was 80%, and the crucible speed was 3 r / min.

[0115] Re-injection: After the melt, 560 kg of raw polysilicon from the melt stage is added again, the temperature is 1500 ° C, the melt is carried out for 7 hours, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 110 slpm, the hydrogen content in the hydrogen-containing gas is 10%, the argon content is 90%, and the crucible speed is 6 r / min.

[0116] Volatilization: control the temperature to 1470°C, volatilize for 2 hours, introduce hydrogen-containing gas, the hydrogen-containing gas flow rate is 110 slpm, the hydrogen content in the hydrogen-containing gas is 10%, the argon content is 90%, and the crucible speed is 6 r / min.

[0117] Welding:

[0118] High-temperature preheating: preheat at 1470°C for 0.3h, introduce hydrogen-containing gas, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 10%, the argon content is 90%, and the crucible speed is 12r / min.

[0119] Low-temperature welding: welding was performed at 1450°C for 2 h, with hydrogen-containing gas introduced at a flow rate of 100 slpm. The hydrogen content of the hydrogen-containing gas was 5%, the argon content was 95%, and the crucible speed was 12 r / min.

[0120] Seeding: The seeding temperature was maintained at 1450°C for 1 hour, and hydrogen-containing gas was introduced with a flow rate of 100 slpm. The hydrogen content in the hydrogen-containing gas was 5%, and the argon content was 95%. The crucible speed was 12 r / min.

[0121] Shoulder expansion: When the shoulder length is 0-75mm, the pulling speed is controlled at 1.4mm / min, the time is 1.2h, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 5%, the argon content is 95%, and the crucible speed is 12r / min.

[0122] When the shoulder length is: 75mm~149mm, the pulling speed is controlled at 1.5mm / min, the time is 0.9h, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 5%, the argon content is 95%, and the crucible speed is 10r / min.

[0123] When the shoulder length is: 150mm~250mm, the pulling speed is controlled at 1.5mm / min, the time is 1h, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 5%, the argon content is 95%, and the crucible speed is 10r / min.

[0124] Shoulder rotation: During the shoulder rotation process, the power of the main heater is maintained at 50kW, the pulling speed is controlled at 1.2mm / min, the time is 0.2h, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 5%, the argon content is 95%, and the crucible speed is 10r / min.

[0125] Equal diameter: When the length of the crystal rod is 0-500mm, the equal diameter time is 7h, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 15%, the argon content is 85%, the crucible speed is 10r / min, and the heating power of the heater is maintained at 46KW.

[0126] When the length of the crystal rod is 500mm~1500mm, the equal diameter time is 12h, hydrogen-containing gas is introduced, the hydrogen-containing gas flow rate is 100slpm, the hydrogen content in the hydrogen-containing gas is 10%, the argon content is 90%, the crucible speed is 8r / min, and the heating power of the heater is maintained at 46KW.

[0127] When the length of the crystal rod is 1500mm~3500mm, the equal diameter time is 20h, hydrogen-containing gas is introduced with a flow rate of 100slpm, a hydrogen content of 10%, an argon content of 90%, a crucible speed of 8r / min, and the heating power of the heater is maintained at 49KW.

[0128] When the length of the crystal rod is 3500mm~4500mm, the equal diameter time is 12h, hydrogen-containing gas is introduced with a flow rate of 100slpm, a hydrogen content of 10%, an argon content of 90%, a crucible speed of 8r / min, and the heating power of the heater is maintained at 49KW.

[0129] The preparation parameters of Example 1 are shown in Table 1.

[0130] Table 1 Crystal ingot preparation parameters of Example 1

[0131] Example 2: The preparation method is different from that of Example 1, except that the time period for passing hydrogen gas is changed. Specific parameters are shown in Table 2.

[0132] Table 2 Crystal ingot preparation parameters of Example 2

[0133] Example 3: The preparation method is different from that of Example 1, except that the time period for passing hydrogen gas is changed. Specific parameters are shown in Table 3.

[0134] Table 3 Crystal ingot preparation parameters of Example 3

[0135] Example 4: The preparation method is different from that of Example 1, except that the time period for passing hydrogen gas is changed. Specific parameters are shown in Table 4.

[0136] Table 4 Crystal ingot preparation parameters of Example 4

[0137] Example 5: The preparation method is different from that of Example 1, except that the parameters of the hydrogen gas are changed. The specific parameters are shown in Table 5.

[0138] Table 5 Crystal ingot preparation parameters of Example 5

[0139] Example 6: The preparation method is the same as that of Example 1, except that the rotation speeds of the first crucible and the second crucible are both controlled to be 10 r / min.

[0140] Example 7: The preparation method is the same as Example 1, except that, during the shoulder expansion process, in the shoulder length stage of 0-75mm, the shoulder length stage of 76mm-149mm and the shoulder length stage of 150mm-245mm, the control step duration is all 1h, and the control time for introducing hydrogen-containing gas is all 1h.

[0141] Example 8: The preparation method is the same as that of Example 1, except that, during the diameter-equalizing process, the speeds of the third and fourth crucible rotations are both controlled to be 8 r / min.

[0142] Example 9: The preparation method is the same as Example 1, except that, in the equal-diameter process, when the crystal rod length is 0-500mm, the control step time is 9h, and the time for introducing hydrogen is 9h; when the crystal rod length is 500mm-1500mm, the control step time is 9h, and the time for introducing hydrogen-containing gas is 9h; when the crystal rod length is 1500mm-3500mm, the control step time is 20h, and the time for introducing hydrogen is 20h; when the crystal rod length is 3500mm-4500mm, the control step time is 9h, and the time for introducing hydrogen-containing gas is 9h.

[0143] Example 10: The preparation method is the same as that of Example 4, except that, during the isobaric process, the hydrogen content in the hydrogen-containing gas introduced is 20%.

[0144] Comparative Example 1: The preparation method is the same as that of Example 1, except that argon gas is introduced throughout the process.

[0145] Performance test: The performance test was performed on the crystal rods prepared in Examples 1 to 10 and Comparative Example 1. The test method is as follows.

[0146] Resistivity test: Use KDY~1A resistivity tester to test the resistivity of the crystal rod.

[0147] The test method for oxygen in the crystal rod head is as follows: oxygen content is measured at the crystal rod head. The test method refers to GB / T1557~2018, and the Nicolet6700 Fourier transform infrared spectrometer is used to test the oxygen content in the crystal rod.

[0148] Life test: The minority carrier lifetime of the crystal ingot is tested using a Sinton BLS-1 minority carrier lifetime tester.

[0149] Carbon content test method: Nicolet 6700 Fourier transform infrared spectrometer is used to test the carbon content in the crystal rod.

[0150] Defect testing method: Use PL defect tester to test crystal ingot defects.

[0151] Table 6 Test results

[0152] The above results show that the ingots produced using the furnaces containing hydrogen gas in Examples 1 to 10 exhibit significantly lower oxygen content than the ingot produced using the furnace in Comparative Example 1. This indicates that hydrogen reduction occurs after the ingot is vented, reducing the oxygen concentration at the solid-liquid interface and, consequently, the oxygen content of the single crystal silicon. This also improves the minority carrier lifetime and pull rate. Furthermore, the ingot production process using hydrogen gas can reduce defects in the single crystal silicon.

[0153] From the data of Examples 1 to 10, it can be seen that hydrogen is located at the bonding center of the B-Si bond in the boron- or gallium-doped P-type single crystal silicon. The distance between hydrogen and boron or gallium is 0.135 nm, and the distance between hydrogen and silicon is 0.164 nm. It is obvious that a B / G-H bond can be formed. Theoretical calculations show that the stretching vibration of the infrared spectrum (IR) of B / G-H is 2031 cm ～1 , rocking vibration is 233cm ～1 , while the experimental measurement of the stretching vibration of B~H is 1903cm ～1 . When the boron or gallium concentration is low, that is, the resistivity is high (10Ω·cm~100Ω·cm), boron or gallium combines with a single hydrogen or two hydrogens. When the resistivity is low (0~0.1Ω·cm), boron or gallium combines with multiple hydrogens (B~H8~12), thereby weakening the acceptor properties of boron or gallium. Hydrogen impurities combine with boron or gallium to form H~B / G complexes, which reduces the boron or gallium concentration in silicon and causes an increase in resistivity. Other acceptor impurities, such as aluminum, phosphorus, indium, etc., can also form complexes with hydrogen, resulting in an increase in resistivity, making it possible to produce longer single crystal rods (silicon rods), thereby improving product yield and quality.

[0154] It can be seen from the data of Examples 1 to 10 that the solution of the present application can significantly reduce the difference in resistivity between the head and tail of the crystal ingot, and improve the axial uniformity of the crystal ingot.

[0155] The source of minority carrier lifetime mainly comes from harmful metal elements in various links; the impact of low minority carrier lifetime: directly affects the conversion efficiency of solar cells. This application introduces hydrogen-containing gas during the crystal rod preparation process to improve the minority carrier lifetime.

[0156] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0157] The above is a detailed introduction to the preparation method and crystal rod of a crystal rod provided in the embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a crystal rod, comprising: A shoulder turning step and a diameter equalizing step, wherein during the shoulder turning step and / or the diameter equalizing step, a hydrogen-containing gas is introduced; the hydrogen-containing gas includes hydrogen, and the mass of the hydrogen is m H , the total mass of the hydrogen-containing gas is m 总 , satisfying: m H / m 总 ≤30%.

2. The method for preparing a crystal rod according to claim 1, wherein: The method for preparing the crystal rod further comprises the steps of melting material, welding, seeding and shoulder expansion, and the hydrogen-containing gas is introduced into any one or several of the steps of melting material, welding, seeding and shoulder expansion.

3. The method for preparing a crystal rod according to claim 2, wherein: The shoulder expansion step includes a shoulder expansion growth stage to a target shoulder length, wherein the shoulder length in the shoulder expansion step is L1, and the target shoulder length is L; in the 0<L1≤0.3L stage, the first crucible is controlled to rotate to V1; in the 0.3L<L1≤L stage, the second crucible is controlled to rotate to V2; and V1>V2 is satisfied.

4. The method for preparing a crystal rod according to claim 3, wherein: The first crucible speed V1 ranges from 9r / min to 15r / min; And / or, the second crucible rotation speed V2 ranges from 7 r / min to 12 r / min.

5. The method for preparing a crystal rod according to claim 2, wherein: In the shoulder expansion step, the shoulder length is L1, the target shoulder length is L; in the stage of 0<L1≤0.3L, the time for passing the hydrogen-containing gas is T1; in the stage of 0.3L<L1≤0.6L, the time for passing the hydrogen-containing gas is T2; in the stage of 0.6L<L1≤L, the time for passing the hydrogen-containing gas is T3; the total time for passing the hydrogen-containing gas in the shoulder expansion step is T 扩肩 , T 扩肩 =T1+T2+T3; Satisfy: T2<T1; And / or, satisfy: T2<T3; And / or, satisfies: T3<T1.

6. The method for preparing a crystal rod according to claim 1, wherein: In the equal diameter step, at the stage of 0<H1≤0.11H, the third crucible is controlled to rotate to V3; at the stage of 0.11H<H1≤H, the fourth crucible is controlled to rotate to V4, satisfying: V3>V4, H1 is the crystal pulling length, and H is the total length of the target crystal rod.

7. The method for preparing a crystal rod according to claim 1, wherein: The equal diameter step includes a first equal diameter stage, wherein the first equal diameter stage is: 0<H1≤0.11H, hydrogen-containing gas is introduced in the first equal diameter stage, H1 is the crystal pulling length, and H is the total length of the target crystal rod.

8. The method for preparing a crystal rod according to claim 7, wherein: The equal diameter step includes a second The second equal-diameter stage is a stage of 0.11H<H1≤0.33H; the third equal-diameter stage is a stage of 0.33H<H1≤0.77H, and the fourth equal-diameter stage is 0.77H<H1≤H; the hydrogen-containing gas is introduced into any one or several stages of the second equal-diameter stage, the third equal-diameter stage and the fourth equal-diameter stage.

9. The method for preparing a crystal rod according to claim 8, wherein: The time for introducing the hydrogen-containing gas in the first equal diameter stage is T4, the time for introducing the hydrogen-containing gas in the second equal diameter stage is T5, the time for introducing the hydrogen-containing gas in the third equal diameter stage is T6, and the time for introducing the hydrogen-containing gas in the fourth equal diameter stage is T7; satisfying: T4<T5=T7<T6; And / or, the hydrogen content of the hydrogen-containing gas in the first equal-diameter stage is higher than the hydrogen content of the hydrogen-containing gas in the second equal-diameter stage, the third equal-diameter stage and the fourth equal-diameter stage.

10. The method for preparing a crystal rod according to claim 2, wherein: The melting step includes feeding, re-feeding and volatilization steps, and the feeding temperature is 300°C to 1600°C; And / or, the re-investment temperature is 1400° C. to 1600° C.; And / or, the volatilization temperature is 1460°C to 1480°C.

11. The method for preparing a crystal rod according to claim 10, wherein: The feeding time is 4h to 12h; And / or, the re-investment time is 3h to 10h; And / or, the volatilization time is 0.3h to 3h.

12. The method for preparing a crystal rod according to claim 10, wherein: The melting step introduces a hydrogen-containing gas, wherein the hydrogen content of the hydrogen-containing gas is ≤30%; And / or, hydrogen-containing gas is introduced during the feeding stage, and the hydrogen content is ≤30%; And / or, the hydrogen-containing gas introduced in the re-injection stage has a hydrogen content of ≤20%, and the hydrogen-containing gas introduced in the volatilization stage has a hydrogen content of ≤20%.

13. The method for preparing a crystal rod according to claim 2, wherein: The welding step includes a high temperature preheating stage and a low temperature welding stage; the temperature of the high temperature preheating stage is 1457°C to 1475°C, and the temperature of the low temperature welding stage is 1449°C to 1457°C; And / or, the crucible rotation speed in the welding step ranges from 6 r / min to 15 r / min; And / or, hydrogen-containing gas is introduced into the welding step, and the hydrogen content in the hydrogen-containing gas is ≤15%; And / or, the high temperature preheating stage lasts for 0.1h to 1h; And / or, the low temperature welding stage lasts for 0.1h to 4h.

14. The method for preparing a crystal rod according to claim 1, wherein: The content of boron and / or gallium in the raw material for preparing the crystal rod is 0.007 mg / g to 0.8 mg / g; or, The phosphorus content in the raw material for preparing the crystal rod is 0.001 mg / g to 0.01 mg / g.

15. A crystal rod, comprising: The crystal rod is prepared by the method according to any one of claims 1 to 14.

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