Method for reducing oxygen content of monocrystalline silicon

Abstract

The invention discloses a method for reducing the oxygen content of monocrystalline silicon. The method for reducing the oxygen content of the monocrystalline silicon comprises the following steps: starting to introduce hydrogen into a furnace in one of a seeding stage, a necking stage, a shouldering stage and a shouldering stage; confirming that the length of the equal-diameter section of the crystal bar reaches L1; and stopping introducing the hydrogen. According to the method for reducing the oxygen content of the monocrystalline silicon, hydrogen is introduced into a furnace at one of a seeding stage, a necking stage, a shouldering stage and a shouldering stage; and after confirming that the length of the equal-diameter section of the crystal bar reaches L1, stopping introducing the hydrogen. Hydrogen can be neutralized with oxygen in the furnace, and water vapor is generated at high temperature, so that the oxygen content in the furnace is reduced, the defects of concentric circles, black chips and the like of monocrystalline silicon wafers produced from monocrystalline silicon are avoided, and the influence on the efficiency and the service life of the monocrystalline silicon wafers is avoided; and when the equal-diameter section reaches L1, the oxygen content in the furnace is low, so that the hydrogen filling can be stopped, the hydrogen filling amount can be reduced, and the manufacturing cost of the monocrystalline silicon can be reduced.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of single crystal silicon preparation, and in particular to a method for reducing the oxygen content of single crystal silicon. Background Art

[0002] In the prior art, the oxygen content is relatively high during the production of single crystal silicon, and the single crystal silicon wafers produced by the single crystal silicon are prone to defects such as concentric circles and black chips, which affect the efficiency and service life of the single crystal silicon wafers. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for reducing the oxygen content of single crystal silicon, which can reduce the oxygen content in the furnace, avoid defects such as concentric circles and black chips in the single crystal silicon wafers produced by single crystal silicon, avoid affecting the efficiency and service life of the single crystal silicon wafers, and the manufacturing cost of the single crystal silicon is low.

[0004] According to an embodiment of the present invention, the method for reducing the oxygen content of single crystal silicon includes: starting to introduce hydrogen into the furnace in one of the seeding stage, necking stage, shoulder release stage and shoulder rotation stage; confirming that the length of the equal-diameter section of the crystal rod reaches L1; and stopping the introduction of hydrogen.

[0005] According to the method for reducing the oxygen content of single crystal silicon in an embodiment of the present invention, hydrogen is introduced into the furnace at one of the stages of seeding, necking, shoulder release and shoulder rotation; and the introduction of hydrogen is stopped after confirming that the length of the equal diameter section of the crystal rod reaches L1. Hydrogen can neutralize the oxygen in the furnace and produce water vapor at high temperature, thereby reducing the oxygen content in the furnace, avoiding defects such as concentric circles and black chips in the single crystal silicon wafers produced by single crystal silicon, and avoiding affecting the efficiency and service life of the single crystal silicon wafers; and when the equal diameter section reaches L1, the oxygen content in the furnace is already low, and the introduction of hydrogen can be stopped, so the amount of hydrogen introduced can be reduced, thereby reducing the manufacturing cost of single crystal silicon.

[0006] In some embodiments of the present invention, the total length of the equal-diameter sections of the crystal rod is L, and satisfies: 0.225≤L1 / L≤0.275.

[0007] In some embodiments of the present invention, L1 satisfies 900 mm ≤ L1 ≤ 1100 mm.

[0008] In some embodiments of the present invention, a first sensor is arranged in the furnace, and the distance between the first sensor and the crucible is L1. Confirming that the length of the equal diameter section of the crystal rod reaches L1 includes: determining that the first sensor recognizes the boundary point between the shoulder turning stage and the equal diameter stage.

[0009] In some embodiments of the present invention, the method for reducing the oxygen content of single crystal silicon further includes: confirming that the length of the equal-diameter section of the crystal rod reaches L2; ​​and starting to introduce hydrogen into the furnace again.

[0010] In some embodiments of the present invention, the total length of the equal-diameter sections of the crystal rod is L, and satisfies: 0.9≤L2 / L≤0.95.

[0011] In some embodiments of the present invention, L2 satisfies 3800 mm ≤ L2 ≤ 4000 mm.

[0012] In some embodiments of the present invention, when the length of the equal diameter section is less than L1, the crystal pulling speed of the equal diameter section is V1, and after the length of the equal diameter section is greater than or equal to L1, the crystal pulling speed of the equal diameter section is V2, and V1 is satisfied. <V2。

[0013] In some embodiments of the present invention, the crystal pulling speed in the seeding stage is V, and satisfies: 2*V1≤V≤3*V1; 2*V2≤V≤3*V2.

[0014] In some embodiments of the present invention, a second sensor is arranged in the furnace, and the distance between the second sensor and the crucible is L2. Confirming that the length of the equal diameter section of the crystal rod reaches L2 includes: determining that the second sensor recognizes the dividing point between the shoulder turning stage and the equal diameter stage.

[0015] In some embodiments of the present invention, the method for reducing the oxygen content of single crystal silicon further includes: confirming that the crystal rod enters the final stage and the diameter of the crystal rod begins to decrease; and stopping the introduction of hydrogen.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 is a flow chart of a method for reducing the oxygen content of single crystal silicon according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0020] In the description of the present invention, 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", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 a limitation on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Reference below Figure 1 A method for reducing the oxygen content of single crystal silicon according to an embodiment of the present invention is described.

[0023] like Figure 1 As shown, the method for reducing the oxygen content of single crystal silicon according to an embodiment of the present invention is used to prepare single crystal silicon.

[0024] Specifically, hydrogen is introduced into the furnace during one of the crystal induction stage, necking stage, shoulder release stage and shoulder rotation stage to neutralize the oxygen in the furnace and generate water vapor at high temperature, thereby reducing the oxygen content in the furnace and avoiding defects such as concentric circles and black chips in the single crystal silicon wafers produced by single crystal silicon, thereby avoiding affecting the efficiency and service life of the single crystal silicon wafers.

[0025] Confirming that the length of the equal-diameter section of the crystal rod has reached L1, it can be understood that in the process of producing crystal rods by the Czochralski method, single crystal silicon enters the equal-diameter section after the crystal seeding stage, necking stage, shoulder release stage and shoulder rotation stage. The equal-diameter section is used for slicing to produce single crystal silicon wafers.

[0026] Stop introducing hydrogen, that is, continue introducing hydrogen before the length of the equal-diameter section reaches L1. Hydrogen continues to combine with oxygen to reduce the oxygen content in the furnace. When the equal-diameter section reaches L1, the oxygen content in the furnace is already low, and the introduction of hydrogen can be stopped. This can reduce the amount of hydrogen introduced and reduce the manufacturing cost of single crystal silicon.

[0027] According to the method for reducing the oxygen content of single crystal silicon in an embodiment of the present invention, hydrogen is introduced into the furnace at one of the stages of seeding, necking, shoulder release and shoulder rotation; and the introduction of hydrogen is stopped after confirming that the length of the equal diameter section of the crystal rod reaches L1. Hydrogen can neutralize the oxygen in the furnace and produce water vapor at high temperature, thereby reducing the oxygen content in the furnace, avoiding defects such as concentric circles and black chips in the single crystal silicon wafers produced by single crystal silicon, and avoiding affecting the efficiency and service life of the single crystal silicon wafers; and when the equal diameter section reaches L1, the oxygen content in the furnace is already low, and the introduction of hydrogen can be stopped, so the amount of hydrogen introduced can be reduced, thereby reducing the manufacturing cost of single crystal silicon.

[0028] In this embodiment, silicon material and a small amount of antimony material are put into the crucible in the furnace, and after melting together, the crystal is pulled directly, so that the antimony material can be evenly distributed in the silicon melt, maintaining a stable resistivity, to achieve precise control of the resistivity, improve the quality of the single crystal, and provide for the back-end process of photovoltaic cells. In addition, hydrogen combines with oxygen to reduce the oxygen content in the furnace, which can reduce the production of toxic antimony oxides and reduce the risk of poisoning by antimony oxides. At this time, the single crystal silicon is an N-type single crystal, which is used to manufacture N-type single crystal silicon wafers.

[0029] In some embodiments of the present invention, the total length of the equal diameter section of the crystal rod is L, and satisfies: 0.225≤L1 / L≤0.275. It can be understood that the ratio of L1 to L can be 0.225, 0.23, 0.235, 0.24, 0.245, 0.25, 0.255, 0.26, 0.265, 0.27 or 0.275, and the ratio between the position L1 where the hydrogen is stopped and the total length L of the equal diameter section of the crystal rod is not less than 0.225, which can avoid the proportion of the part of the equal diameter section where hydrogen is introduced is too small, and avoid the single crystal silicon wafer produced by the single crystal silicon to produce defects such as concentric circles and black chips; the ratio between the position L1 where the hydrogen is stopped and the total length L of the equal diameter section of the crystal rod is not greater than 0.275, which can avoid the length of the part of the equal diameter section where hydrogen is introduced is too large, and can reduce the amount of hydrogen introduced, and reduce the manufacturing cost of the single crystal silicon.

[0030] In some embodiments of the present invention, L1 satisfies 900mm≤L1≤1100mm. It is understandable that L1 can be 900mm, 910mm, 920mm, 930mm, 940mm, 950mm, 960mm, 970mm, 980mm, 990mm, 1000mm, 1010mm, 1020mm, 1030mm, 1040mm, 1050mm, 1060mm, 1070mm, 1080mm, 1090mm or 1100mm. L1 is not less than 900mm, which can avoid the part of the equal diameter section into which hydrogen is introduced being too small, and avoid the single crystal silicon wafers produced by the single crystal silicon to produce defects such as concentric circles and black chips; L1 is not greater than 1100mm, which can avoid the length of the equal diameter section into which hydrogen is introduced being too large, and can reduce the amount of hydrogen introduced, thereby reducing the manufacturing cost of single crystal silicon.

[0031] In some embodiments of the present invention, a first sensor is provided in the furnace, and the distance between the first sensor and the crucible is L1. Confirming that the length of the equal diameter section of the crystal rod reaches L1 includes: determining that the first sensor recognizes the dividing point between the shoulder turning stage and the equal diameter stage. It can be understood that when the first sensor recognizes the dividing point between the shoulder turning stage and the equal diameter stage, the distance between the dividing point between the shoulder turning stage and the equal diameter stage and the crucible is L1, and the length of the equal diameter section reaches L1. At this time, it can be more convenient to confirm that the length of the equal diameter section of the crystal rod reaches L1, which is convenient for stopping the operation of introducing hydrogen, thereby increasing the reliability of the operation of the method for reducing the oxygen content of single crystal silicon.

[0032] In some embodiments of the present invention, Figure 1 As shown, the method for reducing the oxygen content of single crystal silicon also includes: confirming that the length of the equal diameter section of the crystal rod reaches L2, and starting to introduce hydrogen into the furnace again. When the length of the equal diameter section of the crystal rod reaches L2 from L1, the oxygen content in the furnace rises again. By introducing hydrogen into the furnace again, the oxygen content in the furnace can be reduced to avoid a high oxygen content in the furnace. Hydrogen can neutralize the oxygen in the furnace and generate water vapor at high temperature, reducing the oxygen content in the furnace, and avoiding defects such as concentric circles and black chips in the single crystal silicon wafers produced by single crystal silicon, which affects the efficiency and service life of the single crystal silicon wafers.

[0033] In some embodiments of the present invention, the total length of the equal-diameter section of the ingot is L, and it satisfies: 0.9 ≤ L2 / L ≤ 0.95. It can be understood that the ratio of L2 to L can be 0.9, 0.905, 0.91, 0.915, 0.92, 0.925, 0.93, 0.935, 0.94, 0.945, or 0.95. The ratio between the position L2 where hydrogen is re-introduced into the furnace and the total length L of the equal-diameter section of the ingot is not less than 0.9, which can prevent the length of the part of the equal-diameter section where hydrogen is introduced from being too large, reduce the amount of hydrogen introduced, and reduce the manufacturing cost of monocrystalline silicon; the ratio between the position L2 where hydrogen is re-introduced into the furnace and the total length L of the equal-diameter section of the ingot is not greater than 0.95, which can prevent the proportion of the part where hydrogen is re-introduced in the equal-diameter section from being too small, and avoid defects such as concentric circles and black chips in the monocrystalline silicon wafers produced from monocrystalline silicon.

[0034] In some embodiments of the present invention, L2 satisfies 3800mm ≤ L2 ≤ 4000mm. It can be understood that L2 can be 3800mm, 3810mm, 3820mm, 3830mm, 3840mm, 3850mm, 3860mm, 3870mm, 3880mm, 3890mm, 3900mm, 3910mm, 3920mm, 3930mm, 3940mm, 3950mm, 3960mm, 3970mm, 3980mm, 3990mm, or 4000mm. L2 not being less than 3800mm can prevent the length of the part of the equal-diameter section where hydrogen is introduced from being too large, reduce the amount of hydrogen introduced, and reduce the manufacturing cost of monocrystalline silicon; L2 not being greater than 4000mm can prevent the part where hydrogen is re-introduced in the equal-diameter section from being too small, and avoid defects such as concentric circles and black chips in the monocrystalline silicon wafers produced from monocrystalline silicon.

[0035] In some embodiments of the present invention, when the length of the equal-diameter section is less than L1, the crystal pulling speed of the equal-diameter section is V1, and when the length of the equal-diameter section is greater than or equal to L1, the crystal pulling speed of the equal-diameter section is V2, and it satisfies V1 < V2. It can be understood that the crystal pulling speed V1 of the equal-diameter section when the length of the equal-diameter section is less than L1 is less than the crystal pulling speed V2 of the equal-diameter section when the length of the equal-diameter section is greater than or equal to L1. When the crystal pulling just enters the equal-diameter section, the diameter of the monocrystalline silicon reaches the maximum, and the crystal pulling speed decreases, making the growth of the crystal more uniform and making the manufacturing process of the ingot more reliable.

[0036] In some embodiments of the present invention, the crystal pulling speed in the seed crystal stage is V, and it satisfies: 2*V1 ≤ V ≤ 3*V1; 2*V2 ≤ V ≤ 3*V2. It can be understood that the crystal pulling speed in the seed crystal stage is 2 to 3 times the crystal pulling speed of the equal-diameter section. The diameter of the ingot in the seed crystal stage is smaller, and the crystal pulling speed in the seed crystal stage is faster, which can accelerate the process of ingot manufacturing and reduce the manufacturing cost of crystal pulling.

[0037] In addition, under normal circumstances, the heating power in the furnace continues to decrease, and the heating power may be changed according to the situation in the furnace to meet the processing progress of the crystal rod.

[0038] In some embodiments of the present invention, a second sensor is provided in the furnace, and the distance between the second sensor and the crucible is L2. Confirming that the length of the equal diameter section of the crystal rod reaches L2 includes: determining that the second sensor recognizes the dividing point between the shoulder turning stage and the equal diameter stage. It can be understood that when the second sensor recognizes the dividing point between the shoulder turning stage and the equal diameter stage, the distance between the dividing point between the shoulder turning stage and the equal diameter stage and the crucible is L2, and the length of the equal diameter section reaches L2. At this time, it can be more convenient to confirm that the length of the equal diameter section of the crystal rod reaches L2, which is convenient for the operation of introducing hydrogen again, thereby increasing the reliability of the operation of reducing the oxygen content of single crystal silicon.

[0039] In some embodiments of the present invention, Figure 1 As shown, the method for reducing the oxygen content of single crystal silicon also includes: confirming that the crystal rod enters the final stage and the diameter of the crystal rod begins to decrease; and stopping the introduction of hydrogen. The crystal rod in the final stage does not need to be cut into single crystal silicon wafers. At this time, the introduction of hydrogen is stopped to avoid defects such as concentric circles and black chips on the single crystal silicon wafers, thereby avoiding affecting the efficiency and service life of the single crystal silicon wafers.

[0040] In this embodiment, the hydrogen flow rate is 2-10L / min, which can not only avoid excessive hydrogen flow and waste, but also reduce the oxygen content of single crystal silicon, avoid defects such as concentric circles and black chips in single crystal silicon wafers produced by single crystal silicon, and avoid affecting the efficiency and service life of single crystal silicon wafers.

[0041] Other structures and operations of the method for reducing the oxygen content of single crystal silicon according to the embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0042] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0043] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for reducing the oxygen content of single crystal silicon, characterized in that: include: Hydrogen begins to be introduced into the furnace during one of the seeding stage, necking stage, shoulder release stage and shoulder rotation stage; Confirm that the length of the equal diameter section of the crystal rod reaches L1; Stop the hydrogen flow.

2. The method for reducing the oxygen content of single crystal silicon according to claim 1, characterized in that: The total length of the equal-diameter sections of the crystal rod is L, and satisfies: 0.225≤L1 / L≤0.

275.

3. The method for reducing the oxygen content of single crystal silicon according to claim 1, characterized in that: L1 satisfies 900mm≤L1≤1100mm.

4. The method for reducing the oxygen content of single crystal silicon according to claim 1, characterized in that: A first sensor is arranged in the furnace, and the distance between the first sensor and the crucible is L1. The confirmation that the length of the equal diameter section of the crystal rod reaches L1 includes: Determine the dividing point between the shoulder rotation phase and the equal diameter phase detected by the first sensor.

5. The method for reducing the oxygen content of single crystal silicon according to claim 1, characterized in that: Also includes: Confirm that the length of the equal diameter section of the crystal rod reaches L2; Start to feed hydrogen into the furnace again.

6. The method for reducing the oxygen content of single crystal silicon according to claim 5, characterized in that: The total length of the equal-diameter sections of the crystal rod is L, and satisfies: 0.9≤L2 / L≤0.

95.

7. The method for reducing the oxygen content of single crystal silicon according to claim 5, characterized in that: L2 satisfies 3800mm≤L2≤4000mm.

8. The method for reducing the oxygen content of single crystal silicon according to claim 5, characterized in that: When the length of the equal diameter section is less than L1, the crystal pulling speed of the equal diameter section is V1. When the length of the equal diameter section is greater than or equal to L1, the crystal pulling speed of the equal diameter section is V2, and V1 is satisfied. <V2。 9. The method for reducing the oxygen content of single crystal silicon according to claim 8, characterized in that: The crystal pulling speed in the seeding stage is V, and satisfies: 2*V1≤V≤3*V1; 2*V2≤V≤3*V2.

10. The method for reducing the oxygen content of single crystal silicon according to claim 5, characterized in that: A second sensor is arranged in the furnace, and the distance between the second sensor and the crucible is L2. The confirmation that the length of the equal diameter section of the crystal rod reaches L2 includes: Determine the dividing point at which the second sensor recognizes the shoulder rotation stage and the equal diameter stage.

11. The method for reducing the oxygen content of single crystal silicon according to claim 5, characterized in that: Also includes: Confirm that the crystal ingot has entered the final stage and the diameter of the crystal ingot has begun to decrease; Stop the hydrogen flow.

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