WO2022148402A1 - 一种单晶硅拉晶工艺方法 - Google Patents

一种单晶硅拉晶工艺方法 Download PDF

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WO2022148402A1
WO2022148402A1 PCT/CN2022/070545 CN2022070545W WO2022148402A1 WO 2022148402 A1 WO2022148402 A1 WO 2022148402A1 CN 2022070545 W CN2022070545 W CN 2022070545W WO 2022148402 A1 WO2022148402 A1 WO 2022148402A1
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single crystal
furnace
furnace pressure
length
torr
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French (fr)
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邓浩
谢志宴
靳乾
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Longi Green Energy Technology Co Ltd
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Longi Green Energy Technology Co Ltd
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Priority to EP22736564.0A priority Critical patent/EP4257734A4/en
Priority to MYPI2023003991A priority patent/MY210159A/en
Priority to US18/270,540 priority patent/US20240084478A1/en
Priority to AU2022205729A priority patent/AU2022205729B2/en
Publication of WO2022148402A1 publication Critical patent/WO2022148402A1/zh
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/20—Controlling or regulating
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
    • C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/14—Heating of the melt or the crystallised materials
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present disclosure belongs to the technical field of single crystal silicon growth, and in particular relates to a CZ pulling process method for pulling a single crystal silicon doped with dopants (including volatile dopants) with a given target resistivity, in particular to a gallium-doped monocrystalline silicon pulling process method.
  • Crystal silicon pulling process method In the crystal growth process, the accuracy of the resistivity of the head of the crystal rod is controlled, and the production efficiency and yield are improved.
  • the main basic material for photovoltaic power generation is gallium-doped P-type single crystal. Compared with the traditional boron-doped single crystal, it avoids the generation of BO complexes, effectively reduces the initial light-induced attenuation (LID), and ensures the P-type single crystal.
  • the photovoltaic modules can maintain high-efficiency, stable and reliable operation for a long time.
  • the segregation coefficient of gallium is very low, only 0.008.
  • the resistivity of the head and tail of the gallium-doped single crystal is generally set to 1.0 and 0.4 respectively. According to the principle of segregation, during the growth of the crystal rod, the resistivity of the crystal rod will gradually decrease with the increase of its length, which limits the resistivity. The ingot length within the effective range and the oxygen content increase, the minority carrier lifetime of the ingot decreases.
  • the present disclosure aims to solve the problems that the axial resistivity of a single crystal doped with a dopant (especially a volatile dopant, such as gallium) has a relatively fast decay rate, the effective length of the resistivity is limited in principle, the oxygen content is increased, and the The problem of reduced life expectancy for the minority.
  • a dopant especially a volatile dopant, such as gallium
  • a single crystal silicon crystal pulling process method comprises that the single crystal furnace furnace pressure in the equal diameter stage of crystal growth does not exceed 18 Torr, and the flow rate of argon gas introduced into the single crystal furnace furnace is kept within a constant range , the single crystal silicon is doped with dopants.
  • the furnace pressure of the single crystal furnace at the equal diameter stage of crystal growth does not exceed 15 Torr; preferably, the furnace pressure of the single crystal furnace does not exceed 10 Torr.
  • the furnace pressure of the single crystal furnace is controlled to be U 5a , and U 5a takes the value Within the range of 8-15Torr; when the equal diameter length of the single crystal silicon is greater than or equal to 250mm and less than 600mm, the furnace pressure of the single crystal furnace is controlled to be U 5b , and the value of U 5b is within the range of 4-12 Torr; When the isodiametric length of silicon is 600mm and above, the furnace pressure of the single crystal furnace is controlled to be U 5c , and the value of U 5c is in the range of 2-8 Torr; where U 5c ⁇ U 5b ⁇ U 5a .
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the furnace pressure value U of the single crystal furnace When the equal diameter length of single crystal silicon is any length less than 10% of the total ingot length, obtain the furnace pressure value U of the single crystal furnace; compare the obtained furnace pressure value U of the single crystal furnace with the preset furnace pressure value U 51 , when U>U 51 , reduce the furnace pressure until U ⁇ U 51 , where U 51 is in the range of 4-10 Torr;
  • the furnace pressure value U of the single crystal furnace When the equal diameter length of single crystal silicon is greater than or equal to 10% of the total ingot length and less than any length within the range of 45% of the total ingot length, obtain the furnace pressure value U of the single crystal furnace; compare the obtained furnace pressure values of the single crystal furnace U and the preset furnace pressure value U 52 , when U > U 52 , reduce the furnace pressure until U ⁇ U 52 , where the value of U 52 is in the range of 2-4 Torr;
  • the furnace pressure of the single crystal furnace is controlled to be U S501 , and the value of U S501 is in the range of 1-3 Torr;
  • the furnace pressure of the single crystal furnace is controlled to be U S502 , and the value of U S502 is in the range of 0.3-2 Torr Inside;
  • the furnace pressure of the single crystal furnace is controlled to be U S503 , and the value of U S503 is 0.01-0.3 Torr;
  • the furnace pressure of the single crystal furnace is controlled to be U S501 , and U S501 does not exceed 500mTorr;
  • the furnace pressure of the single crystal furnace is controlled to be U S502 , and U S502 does not exceed 300mTorr;
  • the furnace pressure of the single crystal furnace is controlled to be U S503 , and U S503 does not exceed 100mTorr;
  • the single crystal silicon crystal pulling process method according to any one of items 1 to 3, the method further comprises a melting/feeding stage, a seeding stage, a shoulder placing stage, and a shoulder turning stage before the equal diameter stage.
  • the furnace pressure is controlled;
  • the furnace pressure does not exceed 18 Torr, and further preferably, the furnace pressure does not exceed 2 Torr.
  • the single crystal silicon crystal pulling process method according to item 1 the single crystal furnace furnace pressure U, the equal diameter length percentage L of the crystal rod, the argon gas flow rate P, and the vacuum pump frequency F are at least one moment in the equal diameter stage of crystal growth. Room meets:
  • the unit of furnace pressure U of the single crystal furnace is Torr
  • the percentage of equal diameter length of the crystal rod L is the percentage of the drawn length to the total length of the crystal rod
  • the unit of argon flow P is slpm
  • the unit of vacuum pump frequency F is HZ.
  • the single crystal silicon pulling process method according to item 14 the furnace pressure is 0.001Torr ⁇ U ⁇ 15Torr, the argon gas flow rate is 0slpm ⁇ P ⁇ 70slpm; and the vacuum pump frequency is 20HZ ⁇ F ⁇ 60HZ.
  • the single crystal silicon crystal pulling process method according to item 1 characterized in that the furnace pressure range of the single crystal furnace in the equal diameter stage of crystal growth is 0-15 Torr, preferably 2-10 Torr.
  • the unit of furnace pressure U of the single crystal furnace is Torr
  • the percentage of equal diameter length of the crystal rod L is the percentage of the drawn length to the total length of the crystal rod
  • the unit of argon flow P is slpm
  • the unit of vacuum pump frequency F is HZ.
  • the single crystal silicon pulling process method according to any one of items 1-19, wherein the dopant is gallium.
  • the mass percentage content of gallium is preferably 0.01%-0.03%.
  • the vacuum pump is preferably a dry pump.
  • Torr is the pressure unit
  • 1 Torr is 1 mmHg
  • 1 Torr 1000 mtorr
  • slpm is the abbreviation of star liter per minute, that is, the standard liter per minute flow value.
  • the present disclosure adopts a low furnace pressure crystal pulling process, which accelerates the volatilization rate of impurity elements including gallium, and reduces the impurity elements in the solution, thereby suppressing the resistivity decay rate of the crystal rod and increasing the crystal rod within the effective range of resistivity.
  • the tail resistivity is 0.45, the length of the ingot increases significantly, the pull-out ratio increases, and the minority carrier lifetime is greatly improved, reaching more than 10%, and the improvement effect is obvious.
  • the melting point of silicon decreases, the ambient temperature decreases to a certain extent, the heating temperature of the crucible wall decreases, and the dissolution rate of the crucible also decreases, resulting in a decrease in the oxygen content, effectively controlling the amount of oxygen in the crystal.
  • the oxygen content at the head of the ingot decreases significantly, and the oxygen reduction effect is obvious.
  • Fig. 1 - A graph of the axial resistivity decay trend when simulating different furnace pressures according to some theoretical models according to specific embodiments of the present disclosure.
  • Figure 2- a partial enlarged view of the block section of Figure 1.
  • the present disclosure provides a low furnace pressure single crystal silicon crystal pulling process method.
  • the present disclosure adopts the Czochralski method (abbreviated as CZ method) to produce single crystal silicon.
  • CZ method the Czochralski method
  • the polycrystalline silicon material is melted in a quartz crucible.
  • the seed crystal and the melt are first contacted.
  • the molten silicon at the solid-liquid interface is cooled and crystallized along the seed crystal, and grows by slowly pulling out the seed crystal.
  • the crystal growth diameter is enlarged by reducing the pulling rate and/or the melt temperature until the target diameter is reached; After turning the shoulder, the crystal growth enters the "equal diameter growth" stage by controlling the pulling speed and the melt temperature; finally, by increasing the pulling speed and increasing the melt temperature, the diameter of the crystal growth surface is gradually reduced to form an end cone, until the final stage.
  • the growth of the single crystal silicon rod is completed.
  • a crucible is charged, and all the silicon material is melted to obtain a melt. And after the melt is stabilized, it enters the above temperature adjustment operation stage. Then, after lowering the seed crystal to a certain distance from the liquid level of the melt, the seed crystal is preheated to reduce the temperature difference between the seed crystal and the melt and prevent thermal stress from being generated inside the seed crystal when the seed crystal is in contact with the melt. After the temperature difference between the seed crystal and the melt meets the temperature requirement range, the seeding stage is entered. In the seeding stage, a seed crystal is inserted into the melt to fuse the seed crystal with the melt.
  • the crystal diameter needs to be enlarged to the target diameter after the seeding stage is completed. Specifically, when the slender neck grows to a sufficient length and reaches a certain pulling rate, the pulling rate can be appropriately reduced to enter the shoulder-releasing stage.
  • the shouldering stage needs to be performed. After the crystal diameter grows to the preset target diameter, it enters the equal diameter stage.
  • the finishing stage In the isodiametric stage, in order to keep the isothermal surface of the crystal as a plane, the height of the crucible will change with the increase of the crystal.
  • the finishing stage After the equal diameter length of the crystal satisfies the preset target equal diameter length, the finishing stage is performed.
  • the role of the finishing stage is to prevent the dislocation retrogression phenomenon when the crystal suddenly leaves the melt level, and to ensure that the crystal rods grown in the equal diameter operation stage have good quality.
  • the finishing stage After the finishing stage is over, according to the actual growth situation, choose to continue feeding and carry out continuous crystal pulling, or enter the furnace shutdown stage to complete the crystal pulling work.
  • the present disclosure provides a single crystal silicon crystal pulling process method, which is characterized in that the crystal pulling process method includes that the single crystal furnace furnace pressure does not exceed 18 Torr in the equal diameter stage of crystal growth, and argon gas is introduced into the single crystal furnace furnace. The flow rate was kept within a constant range and the single crystal silicon was doped with dopants.
  • the process method optionally includes: a melting/feeding stage, a seeding stage, a shoulder placing stage, a shoulder turning stage, and an equal diameter stage, as follows:
  • Melting material/feeding stage S100 place the silicon block in the quartz crucible, pass argon gas, control the furnace pressure 0.5-15 Torr, the melting material power 60-110 Kw, the silicon material is heated and melted to form a uniform silicon melt, and the melting material starts
  • the argon gas flow is controlled to be 10-100SLPM in the stage. After the material in the crucible is completely melted into a liquid, the melting stage is over, and then the temperature stabilization stage is entered, and the thermal field is stabilized to a suitable seeding temperature. Be prepared, control the furnace pressure to 0.5-10 Torr and the argon flow to 10-100 SLPM during the temperature stabilization stage;
  • Seeding stage S200 The seed crystal is welded with the silicon melt, the dislocations generated during solid-liquid contact are excluded, the furnace pressure is controlled to 0.5-15 Torr, the argon gas flow is 10-100 SLPM, and the maximum cannot exceed 120 SLPM, which provides a stable welding process.
  • the upper limit of the welding diameter is controlled to 16.5mm, the lower limit of the welding diameter is 13mm, the minimum diameter is 10mm, and the seeding gain value is adjusted to 0.085;
  • Shouldering stage S300 Adjust the temperature and pulling speed, enlarge the diameter to the required crystal diameter, the diameter of the single crystal silicon rod is 240-310mm, control the argon flow rate to 10-100SLPM in the shouldering stage, and control the furnace pressure to 0.5-15Torr;
  • Turning shoulder stage S400 After the crystal diameter reaches the specified requirements, adjust the pulling speed and temperature, and perform shoulder turning, so that the crystal can enter the stage of equal diameter growth. In the shoulder turning stage, control the argon flow rate to 10-100SLPM, and control the furnace pressure to 0.5- 15 Torr;
  • Equal diameter stage S500 After the silicon rod reaches the specified diameter, it enters the equal diameter stage, and the single crystal growth process is controlled by controlling the pulling speed of the single crystal silicon rod and the temperature of the melt in the furnace. At this stage, the crystal growth tends to be stable, and the process increases with time.
  • the furnace pressure is gradually reduced as the length of the ingot increases. After the diameter is 200 mm, the furnace pressure is kept less than 2 Torr, and the argon flow rate is reduced. And synchronously adjust other crystal pulling parameters such as power.
  • the whole process of equal diameter is automatically controlled by the system;
  • the molten silicon in the crucible decreases continuously. After the remaining material reaches a certain weight, the diameter of the single crystal silicon rod is reduced by changing the pulling speed and temperature, and by reducing the thermal shock to the crystal from the liquid level.
  • the argon flow can be increased to 40-100SLPM, and the furnace pressure can be controlled at 0-15 Torr.
  • the cycle repeats until the furnace is finished.
  • the furnace pressure of the single crystal furnace is gradually reduced as the length of the ingot increases in the equal diameter stage of crystal growth.
  • the furnace pressure of the single crystal furnace at the equal diameter stage of crystal growth does not exceed 15 Torr; preferably, the furnace pressure of the single crystal furnace does not exceed 10 Torr;
  • the single crystal furnace pressure can be 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6 , 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 , 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, or any range in between.
  • the furnace pressure of the single crystal furnace is controlled to be U 5a , and the value of U 5a is in the range of 8-15 Torr;
  • the furnace pressure of the single crystal furnace is controlled to be U 5b , and the value of U 5b is in the range of 4-12 Torr;
  • the furnace pressure of the single crystal furnace is controlled to be U 5c , and the value of U 5c is in the range of 2-8 Torr; where U 5c ⁇ U 5b ⁇ U 5a .
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the process of gradually reducing the furnace pressure of the single crystal furnace includes:
  • the furnace pressure value U of the single crystal furnace When the equal diameter length of single crystal silicon is any length less than 10% of the total ingot length, obtain the furnace pressure value U of the single crystal furnace; compare the obtained furnace pressure value U of the single crystal furnace with the preset furnace pressure value U 51 , when U>U 51 , reduce the furnace pressure until U ⁇ U 51 , where U 51 is in the range of 4-10 Torr;
  • the furnace pressure value U of the single crystal furnace When the equal diameter length of single crystal silicon is greater than or equal to 10% of the total ingot length and less than any length within the range of 45% of the total ingot length, obtain the furnace pressure value U of the single crystal furnace; compare the obtained furnace pressure values of the single crystal furnace U and the preset furnace pressure value U 52 , when U > U 52 , reduce the furnace pressure until U ⁇ U 52 , where the value of U 52 is in the range of 2-4 Torr;
  • the furnace pressure of the single crystal furnace is controlled to be US501 , and the value of US501 is in the range of 1-3 Torr Inside;
  • the furnace pressure of the single crystal furnace is controlled to be U S502 , and the value of U S502 is in the range of 0.3-2 Torr Inside;
  • the furnace pressure of the single crystal furnace is controlled to be U S503 , and the value of U S503 is 0.01-0.3 Torr;
  • U S503 ⁇ U S502 ⁇ U S501 , wherein U S501 is less than the preset furnace pressure value at any stage of seeding, shoulder placing and shoulder turning.
  • U S53 ⁇ U S52 ⁇ U S51 , wherein U S51 is less than the preset furnace pressure value in any stage of seeding, shoulder placing and shoulder turning.
  • the furnace pressure of the single crystal furnace is controlled to be US501 , and US501 does not exceed 500mTorr;
  • the furnace pressure of the single crystal furnace is controlled to be U S502 , and U S502 does not exceed 300mTorr;
  • the furnace pressure of the single crystal furnace is controlled to be U S503 , and U S503 does not exceed 100mTorr;
  • U S503 ⁇ U S502 ⁇ U S501 , wherein U S501 is less than the preset furnace pressure value at any stage of seeding, shoulder placing and shoulder turning.
  • U S53 ⁇ U S52 ⁇ U S51 , wherein U S51 is less than the preset furnace pressure value in any stage of seeding, shoulder placing and shoulder turning.
  • the method further includes controlling the pressure in the furnace in the melting/feeding stage, the seeding stage, the shouldering stage, and the shouldering stage before the equal diameter stage; preferably, in the In the stages of melting/feeding, seeding, shoulder placement, and shoulder turning, the furnace pressure does not exceed 18 Torr, and further preferably, the furnace pressure does not exceed 2 Torr;
  • the furnace pressure in the melt/feed stage, seeding stage, shouldering stage, and shouldering stage can be 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6,6.5,7,7.5,8,8.5,9,9.5,10,10.5,11,11.5,12,12.5,13,13.5,14,14.5,15,15.5,16,16.5,17,17.5,18Torr or any range in between.
  • At least one moment in the equal diameter stage of crystal growth, the furnace pressure U of the single crystal furnace, the equal diameter length percentage L of the crystal rod, the argon gas flow rate P, and the vacuum pump frequency F satisfy:
  • the unit of furnace pressure U of single crystal furnace is Torr
  • the percentage of equal diameter length of crystal rod L is the percentage of drawn length to the total length of crystal rod
  • the unit of argon flow P is slpm
  • the unit of vacuum pump frequency F is HZ; among them, the furnace pressure is 0.001 Torr ⁇ U ⁇ 15Torr, argon flow 0slpm ⁇ P ⁇ 70slpm; vacuum pump frequency 20HZ ⁇ F ⁇ 60HZ.
  • the single crystal silicon is doped with dopants.
  • the dopant is gallium.
  • a single crystal furnace is a device that melts polycrystalline materials such as polycrystalline silicon with a graphite heater in an inert gas environment, and grows dislocation-free silicon single crystals by the Czochralski method.
  • dopants are added during the growth of crystalline silicon to meet the requirements of electrical properties.
  • Group V elements are commonly used as N-type dopants for single crystal silicon, mainly including phosphorus, arsenic, and antimony.
  • Group III elements are commonly used as P-type dopants for single crystal silicon, mainly including boron, aluminum, and gallium.
  • the drawn silicon single crystal will be formed.
  • the longitudinal resistivity is inconsistent, that is, the resistivity of the drawn silicon single crystal gradually decreases from the head to the tail.
  • the resistivity difference between the head and tail of the silicon single crystal is particularly large.
  • the resistivity of the semiconductor-grade monocrystalline silicon currently produced is seriously attenuated from the head to the tail.
  • the resistivity of the semiconductor-grade mono-crystalline silicon head is about 38 ⁇ cm
  • the resistivity of the semiconductor-grade mono-crystalline silicon middle is about 32 ⁇ cm.
  • the resistivity of its tail is about 20 ⁇ cm.
  • the formation of boron-oxygen complexes can be avoided by doping gallium, and the phenomenon of light attenuation can be suppressed.
  • the small segregation coefficient of gallium (0.008) leads to a wide range of resistivity of the obtained crystalline silicon, especially the part of the crystalline silicon that grows last during the crystallization process (the tail of Czochralski monocrystalline silicon, the directionally solidified polycrystalline silicon.
  • the gallium doping concentration is high, the resistivity is low, and the area where the resistivity meets the requirements (1-3 ⁇ cm) is too small, which can be used for the preparation of high-efficiency solar cells.
  • the rate is only 50%-60%, which makes the cost of growing crystalline silicon prohibitive.
  • a low furnace pressure crystal pulling process is adopted, even reaching the millitorr level.
  • the furnace pressure is close to the saturated vapor pressure of gallium atoms of 0.01 Torr, the volatilization rate of gallium atoms is accelerated, including P, As, Zn, Mg.
  • the saturated vapor pressures of elements such as , Ca, Mn, etc. are all >0.01 Torr, and they will volatilize quickly under this condition, so the impurities in the molten silicon will decrease rapidly under this condition.
  • the gallium atoms in the solution decrease rapidly, which can suppress the decay rate of the resistivity of the ingot, increase the length of the ingot within the effective range of resistivity, improve the uniformity of resistivity during the crystal pulling process, and change the resistivity.
  • the range fluctuation is small, controlled within ⁇ 0.1, the minority carrier lifetime is greatly improved, reaching more than 10%, and the resistivity distribution is uniform, achieving a good technical effect.
  • the term “minority carrier lifetime” refers to the average lifetime of non-equilibrium minority carriers, which is called minority carrier lifetime, or minority carrier lifetime for short.
  • the minority carrier (minority carrier) lifetime of crystalline silicon solar cells is one of the important parameters for evaluating solar cells, which is closely related to the material integrity and impurity content.
  • the minority carrier lifetime reflects the recombination speed of photogenerated carriers on the surface of the solar cell and the matrix, that is, the utilization of photogenerated carriers.
  • the "oxygen content” in the term refers to the oxygen concentration in the crystal, which is one of the core parameters of the crystal quality, mainly derived from the quartz crucible.
  • the "oxygen content” in the term refers to the oxygen concentration in the crystal, which is one of the core parameters of the crystal quality, mainly derived from the quartz crucible.
  • most of the SiO in the silicon melt is freely volatilized on the surface of the melt, part of it enters the single crystal due to segregation, and part remains in the silicon melt. Since there are more silicon melts in the crucible at the beginning of the equal diameter process, and the contact area with the crucible is the largest, the oxygen content is high at this time. During the process, thermal depletion or oxygen precipitation will be formed, which will ultimately affect the minority carrier lifetime or resistivity.
  • Oxygen content/minority carrier lifetime a technical parameter that characterizes the intrinsic quality of single crystal silicon (in the field of photovoltaics, generally, the lower the oxygen content, the better, and the higher the minority carrier lifetime, the better).
  • Czochralski monocrystalline silicon a growth technology for growing monocrystalline silicon.
  • Different conductivity types of monocrystalline silicon need to be doped with different elements. For example, boron (B) is doped for P-type monocrystalline silicon, and phosphorus (P) is doped. It is N-type single crystal silicon.
  • ⁇ is the resistivity
  • q is the unit charge
  • p is the hole concentration in p-type silicon or the electron concentration in n-type silicon
  • ⁇ is the majority carrier mobility .
  • ingot length at a tail resistivity of 0.45" refers to the length of a drawn ingot when the ingot tail resistivity is 0.45 ⁇ .cm.
  • pulse-out ratio when the tail resistivity is 0.45" means the ratio of the weight of the ingot pulled out to the total initial charge of the crucible when the resistivity of the tail of the ingot is 0.45 ⁇ .cm.
  • the single crystal silicon crystal growth process (CZ method) doped with gallium is as follows:
  • the furnace pressure is gradually reduced to 0-10 Torr as the ingot length increases.
  • the isodiameter is automatically controlled by the system, and the furnace pressure is controlled by adjusting the argon flow and/or the frequency of the dry pump.
  • the parameters are shown in Table 1 below:
  • the dry pump is used to adjust the furnace pressure.
  • the upper limit of the frequency of the dry pump is set to avoid full load and affect the service life.
  • Comparative Example 1 The difference between Comparative Example 1 and Example 1 is only that the parameters such as the furnace pressure in the following table are different, and the furnace pressure data in this comparative example are as follows in the comparison table 1:
  • Example 1 Comparative Example 1 The obtained 2500mm monocrystalline silicon ingot head resistivity and the effective ingot tail resistivity are compared as shown in Table 1:
  • Example 1 Comparative Example 1 Ingot head resistivity 1.01 1.01 Effective Ingot Tail Resistivity 0.50 0.46
  • the single crystal silicon crystal growth process (CZ method) doped with gallium is as follows:
  • the furnace pressure of the single crystal furnace is kept at 11-15 Torr, and the argon gas flow is 100 slpm.
  • the ingot equal diameter length percentage and the single crystal furnace pressure were controlled according to the following Table 2, and the furnace pressure was controlled to correspond to each other by adjusting the argon gas flow and/or the dry pump frequency.
  • Comparative Example 2 The difference between Comparative Example 2 and Example 2 is only that the parameters shown in the following table are different, and the data such as furnace pressure in Comparative Example 2 are as follows in Comparative Table 2:
  • the single crystal silicon crystal growth process (CZ method) doped with gallium is as follows:
  • the furnace pressure of the single crystal furnace was maintained at 11-15 Torr, and the argon gas flow was 100 slpm.
  • the value of furnace pressure is within the range of 2Torr ⁇ U ⁇ 10Torr
  • the value of argon gas flow is within the range of 50slpm ⁇ P ⁇ 70slpm
  • the value of dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ
  • Example 2 Example 3 Comparative Example 2 Ingot head resistivity 1.01 1.01 1.01 Effective Ingot Tail Resistivity 0.50 0.49 0.46
  • the obtained 100% single-crystal silicon ingot has the same head resistivity
  • the resistivity of the tail of the effective crystal rod in Example 2 and Example 3 is higher than that of Comparative Example 2.
  • the single crystal silicon crystal growth process (CZ method) doped with gallium is as follows:
  • the furnace pressure of the single crystal furnace at 5-11 Torr, the argon flow rate at 70slpm, and the dry pump frequency at 20Hz;
  • the furnace pressure is within the range of 0.01Torr ⁇ U ⁇ 4Torr
  • the argon flow rate is within the range of 5slpm ⁇ P ⁇ 50slpm
  • the dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ
  • the single crystal silicon crystal growth process (CZ method) doped with gallium is as follows:
  • the furnace pressure of the single crystal furnace at 5-11 Torr, the argon flow rate at 70slpm, and the dry pump frequency at 20Hz;
  • the value of furnace pressure is within the range of 0.01Torr ⁇ U ⁇ 1.5Torr
  • the value of argon gas flow is within the range of 5slpm ⁇ P ⁇ 35slpm
  • the value of dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ
  • the single crystal silicon crystal growth process (CZ method) doped with gallium is as follows:
  • the furnace pressure of the single crystal furnace at 5-11 Torr, the argon flow rate at 70slpm, and the dry pump frequency at 20Hz;
  • the value of furnace pressure is within the range of 1mTorr ⁇ U ⁇ 500mTorr
  • the value of argon gas flow is within the range of 5slpm ⁇ P ⁇ 35slpm
  • the value of dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ
  • Example 7 Compared with Example 5, the difference between Example 7 and Example 5 lies in the melting/feeding stage, seeding stage, shoulder placing stage and shoulder turning stage of crystal growth.
  • the furnace pressure of the single crystal furnace is kept not more than 2 Torr.
  • the parameters of the stage are the same as in Example 5.
  • Example 8 Compared with Example 6, the difference between Example 8 and Example 6 lies in the melting/feeding stage, seeding stage, shoulder placing stage, and shoulder turning stage of crystal growth.
  • the parameters of the stage are the same as in Example 6.
  • resistivity requirements 0.4-1.0, thermal field size 26 inches, single furnace charge: 330kg, furnace pressure 11Torr, argon flow: 80L/min, round bar size: 228mm;
  • resistivity requirements 0.4-1.0, thermal field size 26 inches, single furnace charge: 330kg, furnace pressure ⁇ 1.5Torr, argon flow: 5-70L/min, round bar size: 228mm;
  • Characterization method resistivity: detected by four-probe method; oxygen content: detected by Fourier infrared; minority carrier lifetime: detected by BCT400 equipment.
  • Example 7 Example 5, Example 8 and Example 6 that under the same furnace pressure in the equal diameter stage, when the melting/feeding stage, seeding stage, shouldering stage, and shouldering stage are , when the furnace pressure of the single crystal furnace is kept not more than 2 Torr, the longer the ingot length when the tail resistivity is 0.45, the higher the pull-out ratio when the tail resistivity is 0.45, and the lower the minority carrier lifetime when the ingot length is 100%, that is, The better the technology.
  • a relatively high fixed furnace pressure is usually used to pull a gallium-doped single crystal, and its axial resistivity decay rate is constant.
  • the crystal pulling process of changing furnace pressure in the equal diameter stage is realized, and the volatilization of gallium is promoted, thereby reducing its decay rate and increasing the effective length of resistivity.
  • L is the percentage of the drawn length to the total ingot length, that is, the percentage of equal diameter length
  • ⁇ T is the upper limit of resistivity control, that is, the resistivity of the ingot head
  • ⁇ W is the lower limit of resistivity control, that is, the tail resistivity of the effective crystal rod
  • L 0 is the length of pulling all silicon liquids into crystal rods
  • C(0) is the gallium concentration in the silicon liquid at the beginning of the equal diameter
  • K is the segregation coefficient of gallium
  • Z 1 is the height of the crucible
  • Z 0 is the initial silicon liquid height
  • ⁇ is the gas diffusion coefficient constant
  • T is the temperature of silicon liquid (K);
  • m is the ratio of the diameter of the crystal rod to the inner diameter of the crucible
  • K is the Boltzmann constant
  • C Si is the concentration of silicon atoms in the silicon liquid
  • P is the air pressure in the furnace
  • R is the crystal growth rate
  • the gallium-doped single crystal can be drawn stably under the condition of low furnace pressure by controlling the process parameters of the same diameter by the constant diameter furnace pressure.
  • the shown process method optionally includes:
  • the melting stage keep the normal furnace pressure and argon flow. Typically, the normal furnace pressure is 11-15 Torr and the argon flow is 40-100 splm. The melting power is 50-90kw. After the material in the crucible is completely melted into a liquid, the melting stage ends. Lower the seed crystal to the tempering height.
  • the seed crystal in the stage of temperature adjustment, seeding and shoulder placement, keep the normal furnace pressure.
  • the seed crystal is immersed in the silicon liquid until four crystal points appear, indicating that the fusion is successful, and the seed crystal can be raised for seeding.
  • the seeding length is generally 100-250mm, in order to eliminate dislocations.
  • the seeding After the seeding is completed, it enters the shouldering stage, and the diameter of the crystal gradually increases to form a conical shoulder until the diameter reaches the equal diameter, and the shoulder is turned. After the shoulder is turned, the equal diameter stage is entered.
  • equal diameter stage gradually reduce the furnace pressure with the increase of the length of the ingot, generally to 0-10 Torr. And synchronously adjust other crystal pulling parameters such as vacuum pump power. The whole process of equal diameter is automatically controlled by the system.
  • furnace pressure and other parameters gradually return to normal levels.
  • the equal diameter length reaches the requirement, exit the equal diameter stage and gradually lift the crystal rod out of the liquid surface.
  • the cycle repeats until the furnace is finished.
  • S1, S2, S3 can be carried out in the charging stage, and S4 can be carried out in the finishing stage.
  • one aspect of the present disclosure has the beneficial effect that: by controlling the frequency of the dry pump and/or the flow of argon gas in the equal diameter stage, the gallium-doped single crystal can be drawn stably at a lower furnace pressure, and the gallium-doped single crystal can be effectively reduced.
  • the single crystal axial resistivity decay rate increases the length of the crystal rod within the effective range of resistivity.
  • the single crystal silicon crystal growth process (CZ method) doped with 0.014% (mass percentage) gallium is as follows:
  • the normal furnace pressure is 11-15 Torr (pressure unit, 1 Torr is 1 mmHg), and the argon flow is 100 slpm (stard liter per minute, that is, the standard liter per minute flow value).
  • the dry pump is used to adjust the furnace pressure.
  • the upper limit of the frequency of the dry pump is set to avoid full load carrying and affect the service life.
  • Example 10 The difference between Example 10 and Example 9 is only that the argon flow rate of the single crystal furnace is different.
  • the argon gas flow rate data in Example 10 is as follows in Table 8:
  • Comparative Example 3 The difference between Comparative Example 3 and Example 9 is only that the parameters such as the furnace pressure in the following table are different, and the furnace pressure data in this comparative example are as follows in the comparison table 3:
  • the single crystal silicon crystal growth process (CZ method) doped with 0.014% (mass percentage) of gallium is as follows:
  • the comparison table of the equal diameter length percentage L of the crystal rod and the corresponding preset single crystal furnace pressure U 0 (Table 3'), compare the preset single crystal furnace furnace pressure U 5 with the detected furnace pressure size of U.
  • U 5 ⁇ U keep the dry pump frequency F 1 and the argon flow rate is 70 slpm; when U 0 ⁇ U, increase the dry pump frequency F 1 , gradually increase the dry pump frequency to F 2 , and then detect the single crystal
  • the furnace pressure U and compare the size of U and U 5 , when U 5 ⁇ U, keep the dry pump frequency at F 2 ; when U 5 ⁇ U, continue to increase the dry pump frequency until the equal diameter stage single crystal furnace The furnace pressure is less than or equal to U 5 .
  • the preset single crystal furnace pressure is selected within the range of 2Torr ⁇ U 5 ⁇ 10Torr; the dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ.
  • the single crystal silicon crystal growth process (CZ method) doped with 0.014% (mass percentage) of gallium is as follows:
  • Comparative Example 4 The difference between Comparative Example 4 and Example 12 is only that the parameters shown in the following table are different, and the data such as furnace pressure in Comparative Example 4 are as follows in Comparative Table 2:
  • the single crystal silicon crystal growth process (CZ method) doped with 0.014% (mass percentage) of gallium is as follows:
  • the value of furnace pressure is within the range of 2Torr ⁇ U ⁇ 10Torr
  • the value of argon gas flow is within the range of 50slpm ⁇ P ⁇ 70slpm
  • the value of dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ
  • the single crystal silicon crystal growth process (CZ method) doped with 0.014% (mass percentage) of gallium is as follows:
  • the equal diameter stage according to the following table 6', control the percentage of equal diameter length of the ingot to be L, the furnace pressure of the single crystal furnace U, the flow rate of argon gas P, and the frequency of the dry pump to make them correspond to each other, and always keep them satisfying each other.
  • U A*L+B*P+D*F+C,
  • the value of furnace pressure is within the range of 2Torr ⁇ U ⁇ 10Torr
  • the value of argon gas flow is within the range of 50slpm ⁇ P ⁇ 70slpm
  • the value of dry pump frequency is within the range of 20HZ ⁇ F ⁇ 60HZ

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Abstract

一种掺有挥发性掺杂剂单晶硅拉晶工艺方法，所述拉晶工艺方法包括在晶体生长的等径阶段单晶炉采用不超过18Torr的低炉压，单晶炉炉内通入氩气流量保持在恒定范围内，实现在较低炉压下进行等径拉晶。通过该工艺方法，可以降低掺有挥发性掺杂剂，尤其是镓的单晶的轴向电阻率衰减斜率，提高其电阻率有效长度。

Description

一种单晶硅拉晶工艺方法
相关申请的交叉引用
本申请要求在2021年08月25日提交中国专利局、申请号为202110984273.4、名称为“一种单晶硅拉晶工艺方法”；以及在2021年01月08日提交中国专利局、申请号为202110024166.7、名称为“一种单晶硅拉晶工艺方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本公开属于单晶硅生长技术领域，尤其涉及一种给定目标电阻率的CZ拉制掺有掺杂剂(包括挥发性掺杂剂)的单晶硅拉晶工艺方法，特别涉及掺镓单晶硅拉晶工艺方法。在晶体生长工艺中控制晶棒的头部电阻率准确性，提高生产效率和成品率。
背景技术
随着全球气候变化带来的环境危机和化石能源过度开采引起的能源危机，人们越来越重视清洁能源的发展，而光伏发电作为最具代表性的清洁能源，日益受到全球的重视并得到大力发展。
目前，光伏发电主要的基础材料为掺镓的P型单晶，相比传统的掺硼单晶，由于其避免了BO复合体的产生，有效降低了初始光致衰减(LID)，保证了P型光伏组件能够长期保持高效稳定可靠运行。
然而，镓的分凝系数很低，只有0.008。掺镓单晶头部与尾部电阻率一般分别设定为1.0和0.4，根据分凝原理可知，在晶棒生长过程中，晶棒的电阻率会随其长度增长而逐渐降低，限制了电阻率有效范围内的晶棒长度，同时氧含量增加，晶棒少子寿命变低。
概述
本公开旨在解决掺有掺杂剂(尤其是挥发性掺杂剂，如镓)单晶轴向电阻率衰减速度较快，电阻率有效长度范围在原理上受限制的问 题、氧含量增加及少子寿命变低的问题。
本公开具体技术方案如下：
1.一种单晶硅拉晶工艺方法，所述拉晶工艺方法包括在晶体生长的等径阶段单晶炉炉压不超过18Torr，单晶炉炉内通入氩气流量保持在恒定范围内，所述单晶硅掺有掺杂剂。
2.根据项1所述的单晶硅拉晶工艺方法，在晶体生长的等径阶段随晶棒长度增加逐步降低单晶炉炉压。
3.根据项2所述的单晶硅拉晶工艺方法，在晶体生长的等径阶段单晶炉炉压不超过15Torr；优选地，单晶炉炉压不超过10Torr。
4.根据项2所述的单晶硅拉晶工艺方法，当单晶硅等径长度在大于0mm且小于250mm范围内任一长度时，控制单晶炉炉压为U 5a，U 5a取值在8-15Torr范围内；当单晶硅等径长度在大于或等于250mm且小于600mm范围内时，控制单晶炉炉压为U 5b，U 5b取值在4-12Torr范围内；当单晶硅等径长度在600mm及以上时，控制单晶炉炉压为U 5c，U 5c取值在2-8Torr范围内；其中U 5c<U 5b<U 5a。
5.根据项2所述的单晶硅拉晶工艺方法，逐步降低单晶炉炉压的过程包括：
当晶体生长到预设长度时，获取单晶炉炉压值U；
比较获取的单晶炉炉压值U与预设的炉压值U 5，当U＞U 5时，降低炉压直至U≤U 5。
6.根据项5所述的单晶硅拉晶工艺方法，逐步降低单晶炉炉压的过程包括：
当晶体生长到预设长度时，获取单晶炉炉压值U；
比较获取的单晶炉炉压值U与预设的炉压值U 5，
当U≤U 5时，保持真空泵频率不变；
当U＞U 5时，增大真空泵频率，随后检测单晶炉炉压U，并比较U和U 5的大小，当U≤U 5时，保持真空泵频率不变。
7.根据项5所述的单晶硅拉晶工艺方法，逐步降低单晶炉炉压的过程包括：
当单晶硅等径长度生长到大于或等于100mm且小于350mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 51，当U＞U 51时，降低炉压直至U≤U 51，其中U 51取值在6-14Torr范围内，优选U 51取值在8-12Torr范围内；
当单晶硅等径长度生长到大于或等于350mm且小于600mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 52，当U＞U 52时，降低炉压直至U≤U 52，其中U 52取值在4-10Torr范围内，优选U 52取值在5-8Torr范围内；
当单晶硅等径长度生长到大于或等于600mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 53，当U＞U 53时，降低炉压直至U≤U 53，其中U 53取值在2-8Torr范围内，优选U 53取值在2-6Torr范围内；
其中U 53<U 52<U 51。
8.根据项5所述的单晶硅拉晶工艺方法，逐步降低单晶炉炉压的过程包括：
当单晶硅等径长度为小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 51，当U＞U 51时，降低炉压直至U≤U 51，其中U 51取值在4-10Torr范围内；
当单晶硅等径长度为大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 52，当U＞U 52时，降低炉压直至U≤U 52，其中U 52取值在2-4Torr范围内；
当单晶硅等径长度为大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 53，当U＞U 53时，降低炉压直至U≤U 53，其中U 53取值在0-2Torr范围内；
其中U 53<U 52<U 51。
9.根据项5所述的单晶硅拉晶工艺方法，
当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，控制单晶炉炉压为U S501，U S501取值在1-3Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S502，U S502取值在0.3-2Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S503，U S503取值在0.01-0.3Torr；
其中U S503<U S502<U S501。
10.根据项9所述的单晶硅拉晶工艺方法，
当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S51，当U＞U S51时，降低炉压直至U≤U S51，U S51取值在1-3Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S52，当U＞U S52时，降低炉压直至U≤U S52，U S52取值在0.3-2Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S53，当U＞U S53时，降低炉压直至U≤U S53，U S53取值在0.01-0.3Torr范围内；
其中U S53<U S52<U S51。
11.根据项5所述的单晶硅拉晶工艺方法，
当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，控制单晶炉炉压为U S501，U S501不超过500mTorr；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S502，U S502不超过300mTorr；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S503，U S503不超过100mTorr；
其中U S503<U S502<U S501。
12.根据项11所述的单晶硅拉晶工艺方法，
当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S51，当U＞U S51时，降低炉压直至U≤U S51，U S51不超过500mTorr；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S52，当U＞U S52时，降低炉压直至U≤U S52，U S52不超过300mTorr；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S53，当U＞U S53时，降低炉压直至U≤U S53，U S53不超过100mTorr；
其中U S53<U S52<U S51。
13.根据项1-3任一项所述的单晶硅拉晶工艺方法，所述方法还包括在等径阶段之前的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段对炉内压力进行控制；
优选地，在所述熔料/加料、引晶、放肩、转肩阶段中，炉压不超过18Torr，进一步优选地，炉压不超过2Torr。
14.根据项1所述的单晶硅拉晶工艺方法，在晶体生长的等径阶段至少一个时刻单晶炉炉压U、晶棒等径长度百分比L、氩气流量P、真空泵频率F之间满足：
U＝A*L+B*P+D*F+C，
其中，
1≤A≤10，0.01≤B≤0.02，-0.6≤D≤-0.2，10≤C≤25；
单晶炉炉压U单位为Torr、晶棒等径长度百分比L为已拉制长度占总晶棒长度的百分比、氩气流量P单位为slpm、真空泵频率F单位为HZ。
15.根据项14所述的单晶硅拉晶工艺方法，炉压0.001Torr≤U≤15Torr，氩气流量0slpm＜P≤70slpm；真空泵频率20HZ≤F≤60HZ。
16.根据项1所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段单晶炉炉压范围为0-15Torr，优选2-10Torr。
17.根据项1所述的单晶硅拉晶工艺方法，其特征在于，所述单晶炉炉内通入氩气流量为40-100slpm，优选50-70slpm。
18.根据权项1所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段至少一个时刻单晶炉炉压U、晶棒等径长度百分比L、氩气流量P、真空泵频率F之间满足：
U＝A*L+B*P+D*F+C，
其中，
5≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，15≤C≤20；
单晶炉炉压U单位为Torr、晶棒等径长度百分比L为已拉制长度占总晶棒长度的百分比、氩气流量P单位为slpm、真空泵频率F单位为HZ。
19.根据项18所述的单晶硅拉晶工艺方法，其特征在于，炉压2Torr≤U≤10Torr，氩气流量50slpm≤P≤70slpm；真空泵频率20HZ≤F≤60HZ。
20.根据项1-19任一项所述的单晶硅拉晶工艺方法，所述掺杂剂为镓。镓的质量百分含量优选为0.01％-0.03％。
根据本公开的一个实施方式，所述拉晶工艺方法中，所述真空泵优选为干泵。
本公开中Torr为压强单位，1Torr即1mmHg，1Torr＝1000mtorr；slpm为stard liter per minute缩写,即标准公升每分钟流量值。
本公开的技术方案具有如下技术效果：
(1)本公开采用低炉压拉晶工艺，加快了包括镓在内的杂质元素的挥发速度，溶液中杂质元素减少，从而抑制晶棒电阻率衰减速率，增长电阻率有效范围内的晶棒长度，当尾部电阻率为0.45时，晶棒长度增加明显，拉出比增加提高，少子寿命大幅提升，可达10％以上，改善效果明显。
(2)在本公开的低炉压下，硅的熔点下降，环境温度会发生一定程度的下降，坩埚壁受热温度随之下降，坩埚溶解速率也会降低，导致氧含量降低，有效控制晶体中的氧含量，晶棒头部氧含量降低明显， 降氧效果明显。
附图简述
图1-根据本公开具体实施方式部分理论模型模拟不同炉压下拉晶时轴向电阻率衰减趋势图。
图2-图1方框部分的局部放大图。
详细描述
说明书后续描述为实施本公开的较佳实施方式，所述描述是以说明书的一般原则为目的，并非用以限定本公开的范围。本公开的保护范围当以权利要求所界定的范围为准。下面将参照附图更详细地描述本公开的具体实施方式。虽然附图中显示了本公开的具体实施例，然而应当理解，可以以各种形式实现本公开而不应被这里阐述的实施例所限制。
本公开提供了一种低炉压单晶硅拉晶工艺方法。
本公开采用切克劳斯基法(简称为CZ法)制作单晶硅，该方法通过将多晶硅硅料放置在石英坩埚内融化，在直拉单晶过程中，首先让籽晶和熔体接触，使固液界面处的熔硅沿着籽晶冷却结晶，并通过缓慢拉出籽晶而生长，引晶完成之后通过降低拉速和/或熔体温度来放大晶体生长直径直至达到目标直径；转肩之后，通过控制拉速和熔体温度使晶体生长进入“等径生长”阶段；最后，通过增大拉速和提高熔体温度使晶体生长面的直径逐步减小形成尾锥，直至最后晶体离开熔体表面，即完成了单晶硅棒的生长。
具体来说，以生长硅棒为例，向坩埚内装料，将硅料全部熔化，获得熔体。并待熔体稳定后，进入到上述调温作业阶段。接着降下籽晶至离熔体液面一定距离后，使籽晶预热，以减小籽晶与熔体的温度差，抑制籽晶与熔体接触时籽晶内部产生热应力。待籽晶与熔体之间的温度差满足温度要求范围后，进入引晶阶段。在引晶阶段，将籽晶插入熔体内，使籽晶与熔体熔接。之后，通常采用高拉速将晶体直径缩小到长度要求范围内，以防止生长的晶棒内产生位错。引晶阶段完 成后需要将晶体直径放大到目标直径。具体的，当细颈生长到足够长度，并且达到一定的提拉速率后，可适当降低提拉速率进入放肩阶段。当放肩阶段的晶体直径接近预设的目标直径时，为使得放肩阶段生长出的晶体能够平滑，且直径均匀地过渡到等径阶段，需要进行转肩阶段。待晶体直径生长到预设目标直径后，进入到等径阶段。在等径阶段，为保持晶体的等温面为平面，坩埚的高度会随着晶体的升高而发生变化。待晶体的等径长度满足预设的目标等径长度后，进行收尾阶段。收尾阶段的作用是防止晶体在突然脱离熔体液面时出现位错反延现象，确保等径作业阶段生长出的晶棒具有良好的品质。待收尾阶段结束后，根据实际生长情况选择继续加料，进行连续拉晶，或进入停炉阶段，完成拉晶工作。
本公开提供了一种单晶硅拉晶工艺方法，其特征在于，所述拉晶工艺方法包括在晶体生长的等径阶段单晶炉炉压不超过18Torr，单晶炉炉内通入氩气流量保持在恒定范围内，所述单晶硅掺有掺杂剂。
在本公开的一个实施方式中，所述工艺方法可选地包括：熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段、等径阶段，具体如下：
熔料/加料阶段S100：将硅块放置到石英坩埚中，通入氩气，控制炉压0.5-15Torr，熔料功率60-110Kw，硅料加热融化形成均一的硅熔体，融料起始阶段控制氩气流量为10-100SLPM，待坩埚内料块完全熔化为液体后，熔料阶段结束，随后进入稳温阶段，热场稳定到合适的引晶温度，为籽晶与硅熔体熔接做好准备，稳温阶段控制炉压0.5-10Torr，氩气流量为10-100SLPM；
引晶阶段S200：籽晶与硅熔体熔接，排除固液接触时产生的位错，控制炉压0.5-15Torr，氩气流量为10-100SLPM，最高不得超过120SLPM，为熔接过程提供一个稳定的环境，避免籽晶在溶解过程中出现晃动，为了提高成晶率，控制熔接直径上限为16.5mm，熔接直径下限为13mm，最小直径值为10mm，调整引晶增益值为0.085；
放肩阶段S300：调整温度和拉速，将直径放大到所需晶体直径，单晶硅棒直径为240-310mm，放肩阶段控制氩气流量为10-100SLPM，控制炉压0.5-15Torr；
转肩阶段S400：晶体直径达到规定要求后，调节拉速和温度，进行转肩，使得晶体能够进入到等直径生长的阶段，转肩阶段控制氩气流量为10-100SLPM，控制炉压0.5-15Torr；
等径阶段S500：硅棒达到规定直径后进入等径阶段，通过控制单晶硅棒的拉速和炉内熔体的温度控制单晶生长过程，这一阶段晶体生长趋于稳定，过程中随晶棒长度增加逐步降低炉压，等径200mm后保持炉压不超过2Torr，氩气流量降低。并同步调整功率等其他拉晶参数。等径全程由系统自动化控制；
收尾阶段：随着晶体生长，坩埚中熔硅不断减少，剩料到达一定重量后，通过改变拉速和温度使单晶硅棒直径变小，通过减少热冲击对晶体脱离液面时产生的位错长度，这一阶段可将氩气流量升高到40-100SLPM，炉压控制在0-15Torr。
……
循环往复，直至本炉完结。
在本公开的一个实施方式中，在晶体生长的等径阶段随晶棒长度增加逐步降低单晶炉炉压。
在本公开的一个实施方式中，在晶体生长的等径阶段单晶炉炉压不超过15Torr；优选地，单晶炉炉压不超过10Torr；
例如，单晶炉炉压可以为0.001、0.01、0.02、0.03、0.04、0.05、0.06、0.07、0.08、0.09、0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8、8.5、9、9.5、10、10.5、11、11.5、12、12.5、13、13.5、14、14.5、15或其之间的任意范围。
在本公开的一个实施方式中，当单晶硅等径长度在大于0mm且小于250mm范围内任一长度时，控制单晶炉炉压为U 5a，U 5a取值在8-15Torr范围内；当单晶硅等径长度在大于或等于250mm且小于600mm范围内时，控制单晶炉炉压为U 5b，U 5b取值在4-12Torr范围内；当单晶硅等径长度在600mm及以上时，控制单晶炉炉压为U 5c，U 5c取值在2-8Torr范围内；其中U 5c<U 5b<U 5a。
在本公开的一个实施方式中，逐步降低单晶炉炉压的过程包括：
当晶体生长到预设长度时，获取单晶炉炉压值U；
比较获取的单晶炉炉压值U与预设的炉压值U 5，当U＞U 5时，降低炉压直至U≤U 5。
在本公开的一个实施方式中，逐步降低单晶炉炉压的过程包括：
当晶体生长到预设长度时，获取单晶炉炉压值U；
比较获取的单晶炉炉压值U与预设的炉压值U 5，
当U≤U 5时，保持真空泵频率不变；
当U＞U 5时，增大真空泵频率，随后检测单晶炉炉压U，并比较U和U 5的大小，当U≤U 5时，保持真空泵频率不变。
在本公开的一个实施方式中，逐步降低单晶炉炉压的过程包括：
当单晶硅等径长度生长到大于或等于100mm且小于350mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 51，当U＞U 51时，降低炉压直至U≤U 51，其中U 51取值在6-14Torr范围内，优选U 51取值在8-12Torr范围内；
当单晶硅等径长度生长到大于或等于350mm且小于600mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 52，当U＞U 52时，降低炉压直至U≤U 52，其中U 52取值在4-10Torr范围内，优选U 52取值在5-8Torr范围内；
当单晶硅等径长度生长到大于或等于600mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 53，当U＞U 53时，降低炉压直至U≤U 53，其中U 53取值在2-8Torr范围内，优选U 53取值在2-6Torr范围内；
其中U 53<U 52<U 51。
在本公开的一个实施方式中，逐步降低单晶炉炉压的过程包括：
当单晶硅等径长度为小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 51，当U＞U 51时，降低炉压直至U≤U 51，其中U 51取值在4-10Torr范围内；
当单晶硅等径长度为大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉 炉压值U与预设的炉压值U 52，当U＞U 52时，降低炉压直至U≤U 52，其中U 52取值在2-4Torr范围内；
当单晶硅等径长度为大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 53，当U＞U 53时，降低炉压直至U≤U 53，其中U 53取值在0-2Torr范围内；
在本公开的一个优选实施方式中，当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，控制单晶炉炉压为U S501，U S501取值在1-3Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S502，U S502取值在0.3-2Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S503，U S503取值在0.01-0.3Torr；
其中U S503<U S502<U S501，其中U S501小于引晶、放肩、转肩任一阶段的预设炉压值。
具体地，当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S51，当U＞U S51时，降低炉压直至U≤U S51，U S51取值在1-3Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S52，当U＞U S52时，降低炉压直至U≤U S52，U S52取值在0.3-2Torr范围内；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S53，当U＞U S53时，降低炉压直至U≤U S53，U S53取值在0.01-0.3Torr范围内；
其中U S53<U S52<U S51，其中，U S51小于引晶、放肩、转肩任一阶段的预设炉压值。
在本公开的一个优选实施方式中，当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，控制单晶炉炉压为U S501，U S501不超过500mTorr；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S502，U S502不超过300mTorr；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S503，U S503不超过100mTorr；
其中U S503<U S502<U S501，其中U S501小于引晶、放肩、转肩任一阶段的预设炉压值。
具体地，当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S51，当U＞U S51时，降低炉压直至U≤U S51，U S51不超过500mTorr；
当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S52，当U＞U S52时，降低炉压直至U≤U S52，U S52不超过300mTorr；
当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S53，当U＞U S53时，降低炉压直至U≤U S53，U S53不超过100mTorr；
其中U S53<U S52<U S51，其中U S51小于引晶、放肩、转肩任一阶段的预设炉压值。
在本公开的一个实施方式中，所述方法还包括在等径阶段之前的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段对炉内压力进行控制；优选地，在所述熔料/加料、引晶、放肩、转肩阶段中，炉压不超过18Torr，进一步优选地，炉压不超过2Torr；
例如，熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段的炉压可以为0.001、0.01、0.02、0.03、0.04、0.05、0.06、0.07、0.08、0.09、0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8、8.5、9、9.5、10、 10.5、11、11.5、12、12.5、13、13.5、14、14.5、15、15.5、16、16.5、17、17.5、18Torr或其之间的任意范围。
在本公开的一个实施方式中，在晶体生长的等径阶段至少一个时刻单晶炉炉压U、晶棒等径长度百分比L、氩气流量P、真空泵频率F之间满足：
U＝A*L+B*P+D*F+C，
其中，
1≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，10≤C≤25；
单晶炉炉压U单位为Torr、晶棒等径长度百分比L为已拉制长度占总晶棒长度的百分比、氩气流量P单位为slpm、真空泵频率F单位为HZ；其中，炉压0.001Torr≤U≤15Torr，氩气流量0slpm＜P≤70slpm；真空泵频率20HZ≤F≤60HZ。
在本公开的一个实施方式中，单晶硅掺有掺杂剂。
在本公开的一个优选实施方式中，所述掺杂剂为镓。
单晶炉是一种在惰性气体环境中，用石墨加热器将多晶硅等多晶材料熔化，并用直拉法生长无错位硅单晶的设备。采用单晶炉生产硅单晶过程中，为了满足电池片加工的要求，在晶体硅生长过程中添加掺杂剂，满足电学性能的要求。五族元素常用作单晶硅的N型掺杂剂，主要有磷、砷、锑等。三族元素常用作单晶硅的P型掺杂剂，主要有硼、铝、镓等。但是实际采用单晶炉生产硅单晶过程中，由于上述掺杂剂的掺杂元素在硅单晶内生长界面处固液两相中的扩散速度不同，从而导致拉制成型硅单晶晶体的纵向电阻率不一致，即拉制成型硅单晶晶体的电阻率由头部至尾部逐渐降低。尤其是对于N型硅单晶来说，其硅单晶晶体头尾之间的电阻率相差特别大。例如，目前所生产半导体级单晶硅的电阻率由头部至尾部衰减较为严重，半导体级单晶硅头部的电阻率约38Ω·cm，半导体级单晶硅中部的电阻率约32Ω·cm，而其尾部的电阻率约20Ω·cm。
其中，因硼在硅中的分凝系数(0.8)较接近1，制得的掺硼硅晶体电阻率分布较均匀。然而，掺硼硅片制备的电池片使用后会出现光致衰减现象，降低电池的转换效率，目前主要认为是掺杂硼原子和晶 体硅中的氧原子在太阳光照射下形成的硼-氧复合体有关。
通过掺入镓可以避免硼-氧复合体的生成，抑制光衰减现象。但镓的分凝系数较小(0.008)导致得到的晶体硅的电阻率范围较宽，尤其是在长晶过程中最后生长出的晶体硅部分(直拉单晶硅的尾部、定向凝固的多晶硅碇或类单晶硅的头部)的镓掺杂浓度较高，电阻率偏低，电阻率满足要求的区域(1-3Ω·cm)过少，可用于制备高效太阳电池的晶体硅的收率只有50％-60％，这使得生长晶体硅的成本过高。
在本公开技术方案中，采用低炉压拉晶工艺，甚至达到毫托级，当炉压接近镓原子饱和蒸气压0.01Torr时，镓原子挥发速度加快，此时包括P、As、Zn、Mg、Ca、Mn等元素的饱和蒸气压均＞0.01Torr，在此条件下也会快速挥发，因此在此条件下熔硅中的杂质会快速减少。随着镓原子的快速挥发，溶液中镓原子快速减少，从而可抑制晶棒电阻率衰减速率，增长电阻率有效范围内的晶棒长度，拉晶过程中的电阻率均匀性提高，电阻率变化范围波动小，控制在±0.1内，少子寿命大幅提升，可达10％以上，电阻率分布均匀，达到了很好的技术效果。
术语“少子寿命”指非平衡少数载流子的平均生存时间称为少数载流子寿命，简称少子寿命。晶体硅(Crystalline silicon)太阳电池的少数载流子(少子)寿命是评估太阳电池的重要参数之一，它与材料的完整性和杂质含量有极密切的关系。少子寿命反映了太阳电池表面和基体对光生载流子的复合速度，即反映了光生载流子的利用程度。
术语中的“氧含量”指晶体中的氧浓度，是晶体品质的核心参数之一，主要来源于石英坩埚，在熔融状态下，熔硅与石英坩埚反应生成SiO熔与硅熔体中，在拉晶过程中，硅熔体中绝大部分SiO经熔体表面自由挥发掉，一部分由于分凝进入单晶体内，一部分则留在硅熔体中。由于在刚开始等径过程中，坩埚内硅熔体较多，与坩埚接触面积最大，因此此时氧含量较高，在氧含量高于一定程度后，会形成空位氧缺陷环，在晶体冷却过程中会形成热失主或氧沉淀，最终影响少子寿命或电阻率。
氧含量/少子寿命：表征单晶硅内在品质的技术参数(在光伏领 域，通常氧含量越低越好，少子寿命越高越好)。
直拉单晶硅：一种生长单晶硅的生长技术，不同的导电类型单晶硅需掺入不同元素，例如，掺入硼(B)为P型单晶硅，掺入磷(P)为N型单晶硅。
电阻率公式表示为ρ＝1/qpμ(其中ρ为电阻率，q为单位电荷量，p为p型硅中的空穴浓度或者n型硅中的电子浓度，μ为多数载流子迁移率)。在非补偿硅中，该式中μ和p的关系已经通过以往大量实验得到了明确，可以通过测试电阻率直接换算成硅晶体中载流子浓度。但是在存在补偿效应的硅晶体中，施主和受主的杂质总浓度、补偿度都将造成迁移率偏离原有的μ-p关系，并且这种偏离难以预先测量。
术语“尾部电阻率0.45时的晶棒长度”表示晶棒尾部电阻率为0.45Ω.cm时，拉制晶棒的长度。
术语“尾部电阻率0.45时的拉出比”表示晶棒尾部电阻率为0.45Ω.cm时，拉出晶棒的重量与坩埚初始总投料量的比例。
通过实施例可以对本公开做进一步详细说明，这些实施例仅用来说明本公开，并不限制本公开的范围。本公开的实施例部分由“实施例”、“对比例”、“比较例”、“实验例”组成。
下面将详细地描述本公开的具体实施例。虽然在此显示了本公开的具体实施例，然而应当理解，可以以各种形式实现本公开而不应被这里阐述的实施例所限制。相反，提供这些实施例是为了能够更透彻地理解本公开，并且能够将本公开的范围完整的传达给本领域的技术人员。
实施例1
掺有镓的单晶硅晶体生长过程(CZ法)如下：
熔料阶段，保持炉压为11-15Torr(压强单位，1Torr即1mmHg)，氩气流量为100slpm(stard liter per minute,即标准公升每分钟流量值)。
调温、引晶、放肩阶段，保持炉压为11-15torr。
等径阶段，随晶棒长度增加逐步降低炉压，降低至0-10Torr。等径全程由系统自动化控制，通过调节氩气流量和/或干泵频率来控制炉压。参数如下表1所示：
表1
等径长度(mm) 炉压(Torr)
0 11-15
150 10-14
250 8-12
350 6-10
600 4-8
1500 3-7
2500 2-6
3250 2-6
3400 2-6
收尾阶段，炉压逐步恢复至正常水平。
进入下一循环。
采用干泵调节炉压，为了保护干泵，设定了干泵频率上限，避免其满负荷运载，影响使用寿命。
对比例1
对比例1和实施例1的区别仅在于下表炉压等参数不同，本对比例中炉压数据如下对比表1：
对比表1
等径长度(mm) 炉压(Torr)
0 70
150 50-60
250 40-50
350 30-40
600 20-30
1500 15-20
2500 10-15
比较例1
实施例1、对比例1所得2500mm单晶硅晶棒头部电阻率和有效晶棒尾部电阻率比较如下比较表1：
比较表1
  实施例1 对比例1
晶棒头部电阻率 1.01 1.01
有效晶棒尾部电阻率 0.50 0.46
参见上比较表1，所得2500mm单晶硅晶棒在头部电阻率相等的情况下，实施例1中有效晶棒尾部电阻率高于对比例1。
实施例2
掺有镓的单晶硅晶体生长过程(CZ法)如下：
在晶体生长的熔料阶段、调温阶段、引晶阶段、放肩阶段，保持单晶炉的炉压为11-15Torr，氩气流量100slpm。
在等径阶段，按照如下表2控制晶棒等径长度百分比、单晶炉炉压，通过调节氩气流量和/或干泵频率来控制炉压使其相互对应。
表2
等径长度百分比 炉压(Torr)
0％ 10
4％ 7
7％ 5
10％ 4
18％ 3
44％ 2
74％ 2
96％ 2
100％ 2
对比例2
对比例2和实施例2的区别仅在于下表所示参数不同，对比例2中炉压等数据如下对比表2：
对比表2
等径长度百分比 炉压(Torr)
0％ 70
4％ 70
7％ 70
10％ 70
18％ 68
44％ 58
74％ 40
96％ 20
100％ 10
实施例3
掺有镓的单晶硅晶体生长过程(CZ法)如下：
在晶体生长的熔料阶段、调温阶段、引晶阶段、放肩阶段，保持单晶炉的炉压11-15Torr，氩气流量100slpm。
等径阶段，按照如下表3控制晶棒等径长度百分比为L、单晶炉炉压U、氩气流量P、干泵频率F使其相互对应，并始终保持其相互之间满足U＝A*L+B*P+D*F+C，
其中5≤A≤10，0.01≤B≤0.02，-0.6≤D≤-0.2，15≤C≤20。
其中，炉压取值在2Torr≤U≤10Torr范围内，氩气流量取值在50slpm≤P≤70slpm范围内；干泵频率取值在20HZ≤F≤60HZ范围内
本实施例中相关参数如下表3所示：
表3晶体生长的等径阶段的参数
Figure PCTCN2022070545-appb-000001
比较例2
实施例2、3、对比例2所得100％单晶硅晶棒头部电阻率和有效晶棒尾部电阻率比较如下比较表2：
比较表2
  实施例2 实施例3 对比例2
晶棒头部电阻率 1.01 1.01 1.01
有效晶棒尾部电阻率 0.50 0.49 0.46
参见上比较表2，所得100％单晶硅晶棒在头部电阻率相等的情况下，
实施例2、实施例3中有效晶棒尾部电阻率均高于对比例2。
实施例4
掺有镓的单晶硅晶体生长过程(CZ法)如下：
在晶体生长的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压为5-11Torr，氩气流量为70slpm，干泵频率为20Hz；
等径阶段，按照如下表4控制晶棒等径长度百分比为L、单晶炉炉压U、氩气流量P、干泵频率F使其相互对应，并始终保持其相互之间满足U＝A*L+B*P+D*F+C，
其中1≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，10≤C≤25。
其中，炉压取值在0.01Torr≤U≤4Torr范围内，氩气流量取值在5slpm≤P≤50slpm范围内；干泵频率取值在20HZ≤F≤60HZ范围内
本实施例中相关参数如下表4所示：
表4晶体生长的等径阶段的参数
Figure PCTCN2022070545-appb-000002
实施例5
掺有镓的单晶硅晶体生长过程(CZ法)如下：
在晶体生长的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压为5-11Torr，氩气流量为70slpm，干泵频率为20Hz；
等径阶段，按照如下表5控制晶棒等径长度百分比为L、单晶炉炉压U、氩气流量P、干泵频率F使其相互对应，并始终保持其相互之间满足U＝A*L+B*P+D*F+C，
其中1≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，10≤C≤25。
其中，炉压取值在0.01Torr≤U≤1.5Torr范围内，氩气流量取值在5slpm≤P≤35slpm范围内；干泵频率取值在20HZ≤F≤60HZ范围内
本实施例中相关参数如下表5所示：
表5晶体生长的等径阶段的参数
Figure PCTCN2022070545-appb-000003
实施例6
掺有镓的单晶硅晶体生长过程(CZ法)如下：
在晶体生长的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压为5-11Torr，氩气流量为70slpm，干泵频率为20Hz；
等径阶段，按照如下表6控制晶棒等径长度百分比为L、单晶炉炉压U、氩气流量P、干泵频率F使其相互对应，并始终保持其相互之间满足U＝A*L+B*P+D*F+C，
其中1≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，10≤C≤25。
其中，炉压取值在1mTorr≤U≤500mTorr范围内，氩气流量取值在5slpm≤P≤35slpm范围内；干泵频率取值在20HZ≤F≤60HZ范围内
本实施例中相关参数如下表6所示：
表6晶体生长的等径阶段的参数
Figure PCTCN2022070545-appb-000004
实施例7
实施例7与实施例5相比，区别在于晶体生长的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压不超过2Torr，其余参数相同，等径阶段的参数同实施例5。
实施例8
实施例8与实施例6相比，区别在于晶体生长的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压不超过2Torr，其余参数相同，等径阶段的参数同实施例6。
实验例1
对比条件：电阻率要求：0.4—1.0，热场尺寸26寸，单炉投料量：330kg，炉压11Torr，氩气流量：80L/min，圆棒尺寸：228mm；
实验条件：电阻率要求：0.4—1.0，热场尺寸26寸，单炉投料量：330kg，炉压＜1.5Torr，氩气流量：5-70L/min，圆棒尺寸：228mm；
表征方法：电阻率：四探针法检测；氧含量：傅里叶红外检测；少子寿命：BCT400设备检测。
其他实验条件按本领域通常的实验条件进行
比较例3
实施例4-8所得100％单晶硅晶棒头部电阻率和有效晶棒尾部电阻率比较如下比较表3：
比较表3
Figure PCTCN2022070545-appb-000005
从比较表3可知，从实施例4-6可知，熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压为5-11Torr，而在等径阶段，炉压控制得越低，尾部电阻率0.45时的晶棒长度越长，尾部电阻率0.45时的拉出比越高，晶棒长度100％时的少子寿命越低。
从实施例7与实施例5、从实施例8和实施例6可以看出，在等径阶段炉压相同的情况下，当熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段，保持单晶炉的炉压不超过2Torr时，尾部电阻率0.45时的晶棒长度越长，尾部电阻率0.45时的拉出比越高，晶棒长度100％时的少子寿命越低，即技术效果越好。
现有技术中，通常采用较高的固定炉压拉制掺镓单晶，其轴向电阻率衰减速率恒定。本公开通过在晶体生长的等径阶段控制炉压等参数，实现在等径阶段变炉压的拉晶工艺，促进镓的挥发，从而降低其衰减速率，提升电阻率有效长度。
本公开依据的理论模型如下：
Figure PCTCN2022070545-appb-000006
Figure PCTCN2022070545-appb-000007
其中：L为已拉制长度占总晶棒长度的百分比，即等径长度百分比；
ρ T为电阻率管控上限，即晶棒头部电阻率；
ρ W为电阻率管控下限，即有效晶棒的尾部电阻率；
L 0为将所有硅液拉制为晶棒的长度；
C(0)为等径开始时刻硅液中镓浓度；
K为镓分凝系数；
E为挥发系数；
Z 1为坩埚高度；
Z 0为初始硅液高度；
κ为气体扩散系数常数；
T为硅液温度(K)；
Figure PCTCN2022070545-appb-000008
为镓蒸汽压；
m为晶棒直径与坩埚内径之比；
K为玻尔兹曼常数；
C Si为硅液中硅原子浓度；
P为炉内气压；
R为晶体生长速度。
在头部电阻率相等的情况下，炉压越低，电阻率轴向衰减的斜率越低。根据上述理论模型模拟不同炉压下拉晶时轴向电阻率衰减趋势，得到如图1和图2所示，炉压2Torr相比炉压11Torr拉晶电阻率为0.45时的长度增加了约130mm。由此可以在理论上证明，低炉压拉晶对改善掺镓单晶的轴向电阻率衰减及提升电阻率有效长度是可行的。
根据上述理论模型，通过等径炉压控制等径时工艺参数，可稳定在低炉压条件下拉制掺镓单晶。
与本公开相关的拉晶工艺方法中，所示工艺方法可选地包括：
S1、熔料阶段，保持正常炉压和氩气流量。通常，正常炉压为11-15Torr，氩气流量为40-100splm。熔料功率为50-90kw，待坩埚内料块完全熔化为液体后，熔料阶段结束。下降籽晶至调温高度。
S2、调温、引晶、放肩阶段，保持正常炉压。将籽晶浸入硅液中，直至出现四个晶点，表示熔接成功，可上升籽晶进行引晶，引晶长度一般为100-250mm，目的是排除位错。引晶结束后，进入放肩阶段，晶体直径逐渐变大，形成锥形肩部，直至直径达到等径直径，进行转肩，转肩完成后进入等径阶段。
S3、等径阶段，随晶棒长度增加逐步降低炉压，一般降低至0-10Torr。并同步调整真空泵功率等其他拉晶参数。等径全程由系统自动化控制。
S4、收尾阶段，炉压和其他参数逐步恢复至正常水平。等径长度达到要求时，退出等径阶段，逐步将晶棒提离液面。
S5、熔料阶段，保持正常炉压
……
循环往复，直至本炉完结。
其中S1、S2、S3可在装料阶段进行，S4可在收尾阶段进行。
与现有技术相比，本公开的一个方面有益效果在于：通过在等径阶段控制干泵频率和/或氩气流量，可稳定在较低炉压下拉制掺镓单 晶，有效降低掺镓单晶轴向电阻率衰减速率，增大电阻率有效范围内的晶棒长度。
实施例9
掺有0.014％(质量百分含量)镓的单晶硅晶体生长过程(CZ法)如下：
S1、熔料阶段，保持正常炉压和氩气流量。正常炉压为11-15Torr(压强单位，1Torr即1mmHg)，氩气流量为100slpm(stard liter per minute,即标准公升每分钟流量值)。
S2、调温、引晶、放肩阶段，保持正常炉压。
S3、等径阶段，随晶棒长度增加逐步降低炉压，降低至0-10Torr。等径全程由系统自动化控制。参数如下表7所示：
表7
等径长度(mm) 炉压(Torr) 氩气流量(slpm)
0 11-15 50-70
150 10-14 50-70
250 8-12 50-70
350 6-10 50-70
600 4-8 50-70
1500 3-7 50-70
2500 2-6 50-70
3250 2-6 50-70
3400 2-6 50-70
S4、收尾阶段，炉压逐步恢复至正常水平。
S5、熔料阶段，保持正常炉压。
采用干泵调节炉压，为了保护干泵，设定了干泵频率上限，避免其满负荷运载，影响使用寿命。
实施例10
实施例10和实施例9的区别仅在于单晶炉氩气流量不同，实施例10中氩气流量数据如下表8：
表8
等径长度(mm) 炉压(Torr) 氩气流量(slpm)
0 11-15 71-100
150 10-14 71-100
250 8-12 71-100
350 6-10 71-100
600 4-8 71-100
1500 3-7 71-100
2500 2-6 71-100
3250 2-6 71-100
3400 2-6 71-100
对比例3
对比例3和实施例9的区别仅在于下表炉压等参数不同，本对比例中炉压数据如下对比表3：
对比表3
等径长度(mm) 炉压(Torr) 氩气流量(slpm)
0 70 50-80
150 50-60 50-80
250 40-50 50-80
350 30-40 50-80
600 20-30 50-80
1500 15-20 50-80
2500 10-15 50-80
比较例4
实施例9和10、对比例1所得2500mm单晶硅晶棒头部电阻率和有效晶棒尾部电阻率比较如下比较表4：
比较表4
Figure PCTCN2022070545-appb-000009
参见上比较表4，所得2500mm单晶硅晶棒在头部电阻率相等的情况下，实施例9和实施例10中有效晶棒尾部电阻率均高于对比例1。
实施例11
掺有0.014％(质量百分含量)镓的单晶硅晶体生长过程(CZ法)如下：
S1、在晶体生长的熔料阶段、调温阶段、引晶阶段、放肩阶段，保持单晶炉的炉压11-15Torr,氩气流量100slpm。
S2、在等径阶段，当晶棒等径长度百分比达到如表3’设定值时，通过单晶炉内的检测结果获取此刻对应的炉压；
S3、根据等径阶段，晶棒等径长度百分比L与对应的预设单晶炉炉压U 0对照表(表3’)，比较预设的单晶炉炉压U 5与检测的炉压U的大小。当U 5≥U时，则保持干泵频率F 1，氩气流量为70slpm；当U 0＜U时，增大干泵频率F 1，逐步增大干泵频率至F 2，随后检测单晶炉炉压U，并比较U和U 5的大小，当U 5≥U时，保持干泵频率为F 2；当U 5＜U时，继续增大干泵频率，直至等径阶段单晶炉炉压小于或等于U 5。
优选地，选取预设单晶炉炉压在2Torr≤U 5＜10Torr范围之内；干泵频率20HZ≤F＜60HZ范围之内。
本实施例中相关参数如下表9所示：
表9
Figure PCTCN2022070545-appb-000010
S4、收尾阶段，炉压和其他参数逐步恢复至等径前的数值范围。
实施例12
掺有0.014％(质量百分含量)镓的单晶硅晶体生长过程(CZ法)如下：
S1、在晶体生长的熔料阶段、调温阶段、引晶阶段、放肩阶段，保持单晶炉的炉压11-15Torr,氩气流量100slpm。
S2、在等径阶段，按照如下表10控制晶棒等径长度百分比、单晶炉炉压、氩气流量、干泵频率使其相互对应。
表10
等径长度百分比 炉压(Torr) 氩气流量(slpm) 干泵频率(HZ)
0％ 10 70 20
4％ 7 70 20
7％ 5 70 30
10％ 4 70 40
18％ 3 70 50
44％ 2 70 52
74％ 2 70 54
96％ 2 70 55
100％ 2 70 58
对比例4
对比例4和实施例12的区别仅在于下表所示参数不同，对比例4中炉压等数据如下对比表2：
对比表4
等径长度百分比 炉压(Torr) 氩气流量(slpm) 干泵频率(HZ)
0％ 70 70 20
4％ 70 70 20
7％ 70 70 30
10％ 70 70 40
18％ 68 70 50
44％ 58 70 52
74％ 40 70 54
96％ 20 70 55
100％ 10 70 58
实施例13
掺有0.014％(质量百分含量)镓的单晶硅晶体生长过程(CZ法)如下：
S1、在晶体生长的熔料阶段、调温阶段、引晶阶段、放肩阶段，保持单晶炉的炉压11-15Torr,氩气流量100slpm。
S2、在等径阶段，当晶棒等径长度百分比为L时，通过单晶炉内的检测结构获取此刻对应的炉压U；
S3、等径阶段，单晶炉炉压U、晶棒等径长度百分比L、氩气流量P、干泵频率F之间满足U＝A*L+B*P+D*F+C，
其中5≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，15≤C≤20。
其中，炉压取值在2Torr≤U≤10Torr范围内，氩气流量取值在50slpm≤P≤70slpm范围内；干泵频率取值在20HZ≤F≤60HZ范围内
本实施例中相关参数如下表11所示：
表11
等径长度百分比 炉压(Torr)
0％ 10
4％ 7
7％ 5
10％ 4
18％ 3
44％ 2
74％ 2
96％ 2
100％ 2
实施例14
掺有0.014％(质量百分含量)镓的单晶硅晶体生长过程(CZ法)如下：
S1、在晶体生长的熔料阶段、调温阶段、引晶阶段、放肩阶段，保持单晶炉的炉压11-15Torr,氩气流量100slpm。
S2、等径阶段，按照如下表6’控制晶棒等径长度百分比为L、单晶炉炉压U、氩气流量P、干泵频率F使其相互对应，并始终保持其相互之间满足U＝A*L+B*P+D*F+C，
其中5≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，15≤C≤20。
其中，炉压取值在2Torr≤U≤10Torr范围内，氩气流量取值在50slpm≤P≤70slpm范围内；干泵频率取值在20HZ≤F≤60HZ范围内
本实施例中相关参数如下表12所示：
表12
等径长度百分比 炉压(Torr) 氩气流量(slpm) 干泵频率(HZ)
0％ 10 70 20
4％ 7 70 20
7％ 5 70 30
10％ 4 60 30
18％ 3 60 35
44％ 2 60 35
74％ 2 50 40
96％ 2 50 50
100％ 2 50 60
比较例5
实施例11至14、对比例2所得100％单晶硅晶棒头部电阻率和有效晶棒尾部电阻率比较如下比较表5：
比较表5
Figure PCTCN2022070545-appb-000011
参见上比较表5，所得100％单晶硅晶棒在头部电阻率相等的情况下，实施例11至实施例14中有效晶棒尾部电阻率均高于对比例2。
以上所述，仅是本公开的较佳实施例而已，并非是对本公开作其它形式的限制，任何熟悉本专业的技术人员可能利用上述揭示的技术内容加以变更或改型为等同变化的等效实施例。但是凡是未脱离本公开技术方案内容，依据本公开的技术实质对以上实施例所作的任何简单修改、等同变化与改型，仍属于本公开技术方案的保护范围。

Claims (20)

  1. 一种单晶硅拉晶工艺方法，其特征在于，所述拉晶工艺方法包括在晶体生长的等径阶段单晶炉炉压不超过18Torr，单晶炉炉内通入氩气流量保持在恒定范围内，所述单晶硅掺有掺杂剂。
  2. 根据权利要求1所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段随晶棒长度增加逐步降低单晶炉炉压。
  3. 根据权利要求2所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段单晶炉炉压不超过15Torr；优选地，单晶炉炉压不超过10Torr。
  4. 根据权利要求2所述的单晶硅拉晶工艺方法，其特征在于，当单晶硅等径长度在大于0mm且小于250mm范围内任一长度时，控制单晶炉炉压为U 5a，U 5a取值在8-15Torr范围内；当单晶硅等径长度在大于或等于250mm且小于600mm范围内时，控制单晶炉炉压为U 5b，U 5b取值在4-12Torr范围内；当单晶硅等径长度在600mm及以上时，控制单晶炉炉压为U 5c，U 5c取值在2-8Torr范围内；其中U 5c<U 5b<U 5a。
  5. 根据权利要求2所述的单晶硅拉晶工艺方法，其特征在于，逐步降低单晶炉炉压的过程包括：
    当晶体生长到预设长度时，获取单晶炉炉压值U；
    比较获取的单晶炉炉压值U与预设的炉压值U 5，当U＞U 5时，降低炉压直至U≤U 5。
  6. 根据权利要求5所述的单晶硅拉晶工艺方法，其特征在于，逐步降低单晶炉炉压的过程包括：
    当晶体生长到预设长度时，获取单晶炉炉压值U；
    比较获取的单晶炉炉压值U与预设的炉压值U 5，
    当U≤U 5时，保持真空泵频率不变；
    当U＞U 5时，增大真空泵频率，随后检测单晶炉炉压U，并比较U和U 5的大小，当U≤U 5时，保持真空泵频率不变。
  7. 根据权利要求5所述的单晶硅拉晶工艺方法，其特征在于，逐步降低单晶炉炉压的过程包括：
    当单晶硅等径长度生长到大于或等于100mm且小于350mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 51，当U＞U 51时，降低炉压直至U≤U 51，其中U 51取值在6-14Torr范围内，优选U 51取值在8-12Torr范围内；
    当单晶硅等径长度生长到大于或等于350mm且小于600mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 52，当U＞U 52时，降低炉压直至U≤U 52，其中U 52取值在4-10Torr范围内，优选U 52取值在5-8Torr范围内；
    当单晶硅等径长度生长到大于或等于600mm范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 53，当U＞U 53时，降低炉压直至U≤U 53，其中U 53取值在2-8Torr范围内，优选U 53取值在2-6Torr范围内；
    其中U 53<U 52<U 51。
  8. 根据权利要求5所述的单晶硅拉晶工艺方法，其特征在于，逐步降低单晶炉炉压的过程包括：
    当单晶硅等径长度为小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 51，当U＞U 51时，降低炉压直至U≤U 51，其中U 51取值在4-10Torr范围内；
    当单晶硅等径长度为大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 52，当U＞U 52时，降低炉压直至U≤U 52，其中U 52取值在2-4Torr范围内；
    当单晶硅等径长度为大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U；比较获取的单晶炉炉压值U与预设的炉压值U 53，当U＞U 53时，降低炉压直至U≤U 53，其中U 53取值在0-2Torr范围内；
    其中U 53<U 52<U 51。
  9. 根据权利要求5所述的单晶硅拉晶工艺方法，其特征在于，
    当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，控制单晶炉炉压为U S501，U S501取值在1-3Torr范围内；
    当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S502，U S502取值在0.3-2Torr范围内；
    当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S503，U S503取值在0.01-0.3Torr；
    其中U S503<U S502<U S501。
  10. 根据权利要求9所述的单晶硅拉晶工艺方法，其特征在于，
    当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S51，当U＞U S51时，降低炉压直至U≤U S51，U S51取值在1-3Torr范围内；
    当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S52，当U＞U S52时，降低炉压直至U≤U S52，U S52取值在0.3-2Torr范围内；
    当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S53，当U＞U S53时，降低炉压直至U≤U S53，U S53取值在0.01-0.3Torr范围内；
    其中U S53<U S52<U S51。
  11. 根据权利要求5所述的单晶硅拉晶工艺方法，其特征在于，
    当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，控制单晶炉炉压为U S501，U S501不超过500mTorr；
    当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S502，U S502不超过300mTorr；
    当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，控制单晶炉炉压为U S503，U S503不超过100mTorr；
    其中U S503<U S502<U S501。
  12. 根据权利要求11所述的单晶硅拉晶工艺方法，其特征在于，
    当单晶硅等径长度小于总晶棒长度10％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S51，当U＞U S51时，降低炉压直至U≤U S51，U S51不超过500mTorr；
    当单晶硅等径长度大于或等于总晶棒长度10％且小于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S52，当U＞U S52时，降低炉压直至U≤U S52，U S52不超过300mTorr；
    当单晶硅等径长度大于或等于总晶棒长度45％范围内任一长度时，获取单晶炉炉压值U，比较获取的单晶炉炉压值U与预设的炉压值U S53，当U＞U S53时，降低炉压直至U≤U S53，U S53不超过100mTorr；
    其中U S53<U S52<U S51。
  13. 根据权利要求1-3任一项所述的单晶硅拉晶工艺方法，其特征在于，所述方法还包括在等径阶段之前的熔料/加料阶段、引晶阶段、放肩阶段、转肩阶段对炉内压力进行控制；
    优选地，在所述熔料/加料、引晶、放肩、转肩阶段中，炉压不超过18Torr，进一步优选地，炉压不超过2Torr。
  14. 根据权利要求1所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段至少一个时刻单晶炉炉压U、晶棒等径长度百分比L、氩气流量P、真空泵频率F之间满足：
    U＝A*L+B*P+D*F+C，
    其中，
    1≤A≤10，0.01≤B≤0.02，-0.6≤D≤-0.2，10≤C≤25；
    单晶炉炉压U单位为Torr、晶棒等径长度百分比L为已拉制长度占总晶棒长度的百分比、氩气流量P单位为slpm、真空泵频率F单位为HZ。
  15. 根据权利要求14所述的单晶硅拉晶工艺方法，其特征在于，炉压0.001Torr≤U≤15Torr，氩气流量0slpm＜P≤70slpm；真空泵频率20HZ≤F≤60HZ。
  16. 根据权利要求1所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段单晶炉炉压范围为0-15Torr，优选2-10Torr。
  17. 根据权利要求1所述的单晶硅拉晶工艺方法，其特征在于，所述单晶炉炉内通入氩气流量为40-100slpm，优选50-70slpm。
  18. 根据权利要求1所述的单晶硅拉晶工艺方法，其特征在于，在晶体生长的等径阶段至少一个时刻单晶炉炉压U、晶棒等径长度百分比L、氩气流量P、真空泵频率F之间满足：
    U＝A*L+B*P+D*F+C，
    其中，
    5≤A≤10，0.01≤B≤0.02,-0.6≤D≤-0.2，15≤C≤20；
    单晶炉炉压U单位为Torr、晶棒等径长度百分比L为已拉制长度占总晶棒长度的百分比、氩气流量P单位为slpm、真空泵频率F单位为HZ。
  19. 根据权利要求18所述的单晶硅拉晶工艺方法，其特征在于，炉压2Torr≤U≤10Torr，氩气流量50slpm≤P≤70slpm；真空泵频率20HZ≤F≤60HZ。
  20. 根据权利要求1-19任一项所述的单晶硅拉晶工艺方法，其特征在于，所述掺杂剂为镓。
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