A quartz crucible for Czochralski silicon single crystal and a method for growing a silicon single crystal ingot by the Czochralski method

Abstract

The present invention relates to the technical field of silicon single crystal preparation, and provides a quartz crucible for pulling silicon single crystals and a method for growing silicon single crystal ingots. On the inner cavity side surface of the quartz crucible, one or more first convex ridges protruding relative to the inner cavity side surface of the quartz crucible are arranged, and the first convex ridge pressing angle is 10° ≤ α1 ≤ 85°; the height of the first convex ridge is greater than the first boundary layer thickness of the liquid silicon on the inner cavity side surface of the quartz crucible, or on the inner cavity bottom surface of the quartz crucible, one or more second convex ridges protruding relative to the inner cavity bottom surface of the quartz crucible are provided, with a second convex ridge pressing angle α2, and the second convex ridge pressing angle α2 gradually decreases with the increase of the distance r from the z-axis, and the variation range is 2° < α2 < 78°, so as to suppress the liquid silicon flow and reduce the oxygen content. In the silicon single crystal preparation method, the equivalent angular velocity ω of the crucible rotation is used as an important adjustment parameter in the control method, which can simplify the process control process and more easily achieve the ideal control effect.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon single crystal preparation. Specifically, it relates to a quartz crucible for pulling silicon single crystals and a method for growing silicon single crystal ingots by the Czochralski method. Background Art

[0002] The prior art of growing silicon single crystal rods by the Czochralski method has the advantages of high production efficiency, large cross-sectional area of the crystal rod, and high dimensional control accuracy. However, in the following three aspects: the oxygen element content, the axial impurity concentration gradient of n-type silicon single crystal rods, and the uniformity of internal stress and radial impurity distribution in the silicon single crystal rods, there are also the following three deficiencies:

[0003] First, due to the use of a quartz crucible in the growth of silicon crystals, the erosion of the crucible wall by the thermal convection of liquid silicon causes a large amount of oxygen elements in the quartz crucible to enter the liquid silicon, resulting in a high content of impurity oxygen in the silicon single crystal. And due to the change in the height of the liquid silicon surface during the crystal pulling process affecting the intensity of the thermal convection of liquid silicon, and the segregation coefficient of impurity oxygen greater than 1, the longitudinal distribution of impurity oxygen in the entire silicon single crystal rod is uneven, and the controllability of the oxygen impurity distribution is poor.

[0004] Too high an oxygen content in the silicon single crystal will generate large stress, resulting in warping and fracture of the silicon wafer, and inducing defects such as dislocations and stacking faults; in the production of silicon photovoltaic cells, too high an oxygen content and defect density will reduce the minority carrier lifetime of the silicon single crystal material and the photoelectric conversion efficiency of the solar cell; the increase in the oxygen content in the silicon single crystal will also lead to an increase in the light-induced degradation trend of the silicon photovoltaic cell; the poor controllability of the impurity oxygen distribution leads to poor quality consistency of the product.

[0005] Second, in the prior art when growing n-type conductive silicon single crystals, since the solid-liquid interface equilibrium segregation coefficient of the n-dopant phosphorus is much lower than 1, in order to maintain the phosphorus impurity concentration at the head of the silicon single crystal, the initial doping amount of phosphorus is relatively high, and during the process of pulling the silicon single crystal, the content of impurity phosphorus in the liquid silicon will become higher and higher, so that the impurity concentration at the tail of the silicon single crystal rod also becomes higher and higher, exceeding the quality control range, ultimately limiting the length of the silicon single crystal rod and reducing the production rate.

[0006] Third, in the prior art when growing silicon single crystals, due to the poor heat dissipation conditions at the central part of the growth interface, the temperature of the liquid silicon at the central part is relatively high, making the growth interface of the crystal concave. The concave crystal surface will generate high internal stress in the silicon single crystal and the silicon wafer. Too high internal stress in the crystal will damage the growth environment of the silicon single crystal and is a limiting factor for the maximum cross-sectional area of the silicon single crystal rod. The concave crystal surface increases the internal stress on the plane of the cut silicon wafer, and the impurity distribution in the wafer is uneven and often shows concentric circular defects, which reduce the photoelectric conversion efficiency and reliability of the silicon photovoltaic cell.

[0007] The technical measures for controlling the oxygen content and its distribution uniformity in Czochralski silicon single crystals in the prior art include two categories: magnetic field oxygen control and non-magnetic field oxygen control. The former places the silicon melt in a certain magnetic field environment and weakens the thermal convection movement of the liquid silicon by means of the Lorentz force to achieve the purpose of oxygen control. This measure is effective in oxygen control, but both the equipment and operating costs are relatively high. The latter controls oxygen by adopting appropriate thermal field distribution, crucible position, crucible rotation, crystal rotation and other process means, with lower costs. However, it is more involved with other technical indicators of silicon single crystals, such as the shape of the crystallization interface, impurity distribution, crystal defect requirements, etc. Therefore, the regulation is complex and it is difficult to achieve an ideal control effect.

[0008] The methods for controlling the axial doping concentration distribution of n-dopant phosphorus in silicon single crystals in the prior art include:

[0009] 1) Controlling the growth length of the silicon single crystal;

[0010] 2) During the crystal pulling process, gradually adding p-type impurity boron to counteract the gradually increasing n-type impurity concentration;

[0011] 3) By co-doping n-type dopants arsenic and antimony, adjusting the doping concentration of the total n-dopant by utilizing the high volatility of impurities arsenic and antimony.

[0012] The deficiencies of the prior art:

[0013] 1) Method 1) reduces productivity;

[0014] 2) Method 2) is at the cost of increasing the total impurity content in the silicon single crystal. A high total impurity content leads to a decrease in the minority carrier lifetime of the silicon single crystal, and a low minority carrier lifetime results in a low photoelectric conversion efficiency of the photovoltaic cell;

[0015] 3) For method 3), the toxicity of impurity arsenic will cause relatively serious environmental problems, and the high volatility and low segregation coefficient of antimony make the control difficult.

[0016] The technical measures for controlling the crystal growth interface to be concave in the prior art are:

[0017] 1) As the silicon single crystal rod grows, appropriately increase the heating power of the surrounding graphite heater. By increasing the temperature of the liquid silicon at the edge, reduce the crystallization rate at the edge of the silicon single crystal rod, and then gradually reduce the pulling speed to control the pit depth of the crystallization interface within the permitted range;

[0018] 2) Improve the heat dissipation conditions near the axis of the silicon single crystal ingot by reducing the cross-sectional area of the silicon single crystal rod, and control the pit depth of the crystallization interface within the permitted range.

[0019] However, both of the above two measures are at the cost of sacrificing production efficiency and the maximum cross-sectional area of the pulled silicon single crystal rod.

[0020] The present invention is proposed to solve at least one of the three problems existing in the above prior art. It should be noted that some content of the present invention only provides background art related to the present invention, and does not necessarily constitute prior art or well-known art. Summary of the Invention

[0021] I. Nouns and Terms:

[0022] For the convenience of description, the following nouns and terms are defined in this application document:

[0023] 1) (Liquid silicon) pressing angle:

[0024] Observe an intersection point p of the convex rib contour line on the inner wall of the quartz crucible (including the inner side wall and the bottom wall) with the xoz plane. The quartz crucible rotates by an angle of Δθ around its vertical symmetry axis, causing the intersection point p to move a distance of Δ along the inner wall convex rib in the xoz plane l , then the angle α near point p is defined as the pressing angle:

[0025]

[0026] where d is the distance from the z-axis of the crucible to point p.

[0027] 2) "Right-handed rotation" and "left-handed rotation" of the quartz crucible:

[0028] Close the four fingers of the right hand, with the thumb pointing downwards in the direction of the bottom of the crucible (-z direction). The rotation direction of the four fingers represents the rotation direction Ω of the crucible, then this is the "right-handed rotation" of the crucible; similarly, close the four fingers of the left hand, with the thumb pointing downwards in the direction of the bottom of the crucible (-z direction), then the rotation direction of the four fingers represents the rotation direction Ω of the crucible, and this is the "left-handed rotation" of the crucible.

[0029] 3) "Right-handed rotation" and "left-handed rotation" of the convex rib:

[0030] For the convex rib on the inner side wall of the quartz crucible: Close the four fingers of the right hand, with the thumb pointing downwards in the direction of the bottom of the crucible (-z direction). The rotation direction Ω of the four fingers represents the downward oblique direction of the convex rib rotation, then this is regarded as the "right-handed rotation" of the convex rib; similarly, close the four fingers of the left hand, with the thumb pointing downwards in the direction of the bottom of the crucible (-z direction). The rotation direction Ω of the four fingers represents the downward oblique direction of the convex rib rotation, then this is regarded as the "left-handed rotation" of the convex rib.

[0031] For the convex rib on the inner bottom of the quartz crucible: Close the four fingers of the right hand, with the thumb pointing downwards in the direction of the bottom of the crucible (-z direction). The rotation direction Ω of the four fingers represents the direction of the convex rib shrinking and rotating towards the crucible rotation axis, then this is regarded as the "right-handed rotation" of the bottom convex rib; similarly, close the four fingers of the left hand, with the thumb pointing downwards in the direction of the bottom of the crucible (-z direction). The rotation direction Ω of the four fingers represents the direction of the convex rib shrinking and rotating towards the crucible rotation axis, then this is regarded as the "left-handed rotation" of the bottom convex rib.

[0032] 4) "Right-handed" and "left-handed" of single crystal silicon rods:

[0033] Close the four fingers of the right hand, with the thumb pointing downwards, towards the bottom of the crucible (-z direction). The direction of rotation of the four fingers represents the rotation direction of the single crystal silicon rod, and this is the "right-handed" rotation of the single crystal silicon rod; similarly, close the four fingers of the left hand, with the thumb pointing downwards, towards the bottom of the crucible (-z direction), and the direction of rotation of the four fingers represents the rotation direction of the single crystal silicon rod, which is the "left-handed" rotation of the single crystal silicon rod.

[0034] 5) "First boundary layer" and "first outer boundary layer" of liquid silicon at the liquid silicon / crucible interface:

[0035] The "first boundary layer" of liquid silicon is a thin flowing layer in the liquid silicon fluid where the viscous force close to the inner cavity side surface of the crucible cannot be ignored. In this application document, the thickness of the first boundary layer is a function of the crucible wall position (such as the liquid level height z), and has the following relationship:

[0036]

[0037] Where:

[0038] : The first correlation coefficient. When calculating, a numerical value of 5 can be tentatively taken;

[0039] : The viscosity coefficient of liquid silicon;

[0040] : The characteristic length, which is related to the transverse diameter length of the eddy current along the movement direction of the liquid silicon close to the crucible wall on one side of the crucible. When calculating, half of its length can be taken as the characteristic length;

[0041] : The density of liquid silicon;

[0042] : The thermal convection rising rate of the liquid silicon in the first outer boundary layer of the liquid silicon at the first convex edge on the inner cavity side surface of the quartz crucible.

[0043] It can be obtained by simulating the internal flow field of liquid silicon through simulation software such as CG-sim and FEMAG, or it can also be obtained through experiments. Here, only the rate of the corresponding area in the liquid silicon fluid is given as an example. Since the rate in the existing liquid silicon fluid can be obtained by various methods such as simulation and theoretical calculation, the specific method of obtaining it is not specifically limited here.

[0044] The "first outer boundary layer" refers to a thin layer outside the "first boundary layer" where the thermal convection rate of the liquid silicon can reach more than 90% of the highest flow rate in the vicinity.

[0045] 6) "Second boundary layer" and "second outer boundary layer" of liquid silicon at the liquid silicon / crucible interface:

[0046] Similar to the "first boundary layer" of liquid silicon, the "second boundary layer" of liquid silicon is a flowing thin layer with non-negligible viscous force that adheres to the bottom surface of the inner cavity of the crucible in the liquid silicon fluid. In this application document, the thickness of the second boundary layer is a function of the position of the crucible wall (such as the distance r from the axis), and has the following relationship:

[0047]

[0048] where:

[0049] : The second correlation coefficient. When calculating, a value of 5 can be tentatively taken;

[0050] : The viscosity coefficient of liquid silicon;

[0051] : The characteristic length, which is related to the cross-sectional diameter length of the eddy current in the direction of the liquid silicon moving along the crucible wall near the crucible. When calculating, half of its length can be taken as the characteristic length;

[0052] : The density of liquid silicon;

[0053] : The convective rate of the liquid silicon in the outer layer of the second boundary of the liquid silicon at the second convex rib;

[0054] It can be obtained by simulating the internal flow field of liquid silicon through simulation software such as CG-sim and FEIMAG, or can also be obtained through experiments. Here, only the rate of the corresponding area in the liquid silicon fluid is given as an example. Since the rate in the existing liquid silicon fluid can be obtained by various methods such as simulation and theoretical calculation, the obtaining method thereof is not specifically limited herein.

[0055] The "outer layer of the second boundary" refers to a thin layer outside the "second boundary layer" where the thermal convective rate of the liquid silicon can reach more than 90% of the highest flow rate in the vicinity.

[0056] The above first or second boundary layer can also be defined by the impurity concentration contained in the layer. Assume that there is an excess oxygen impurity concentration in the boundary layer that exceeds the average oxygen ion impurity concentration level of the liquid silicon inside the crucible , and the excess oxygen impurity concentration at the crucible wall is . Starting from the position close to the crucible wall, until the excess oxygen impurity concentration in the liquid silicon drops to 0.37 . A thin layer. It has been proven that the thicknesses of the boundary layers defined by the above two methods are quite equivalent.

[0057] 7) "Third boundary layer" and "outer layer of the third boundary":

[0058] The "third boundary layer" is the liquid silicon / silicon single crystal boundary layer, referring to a thin layer of liquid silicon adjacent to the silicon single crystal. The most important feature of this thin layer is the existence of a difference from the average impurity concentration level of the liquid silicon inside the crucible. , assuming that there is an excess impurity concentration in the third boundary layer that exceeds the average impurity concentration level of the liquid silicon inside the crucible. , for impurities with a segregation coefficient of silicon less than 1, such as phosphorus, arsenic, and antimony, it is positive, and for impurities with a segregation coefficient of silicon greater than 1, such as oxygen, it is negative. The excess impurity concentration at the crystal silicon crystallization interface is .

[0059] Define a thin layer starting from the crystal silicon solid-liquid interface and ending where the excess impurity concentration in the liquid silicon drops to 0.37 as the third boundary layer.

[0060] The thickness of the third boundary layer can be calculated by the following formula:

[0061]

[0062] Where:

[0063] : Correlation coefficient. For example, for the impurity antimony, 1.61 can be selected;

[0064] D: Diffusion coefficient of the impurity in liquid silicon;

[0065] : Kinematic viscosity coefficient of liquid silicon;

[0066] : Relative movement rate of the liquid silicon in the "outer third boundary layer".

[0067] It can be obtained by simulating the internal flow field of liquid silicon through simulation software such as CG-sim and FEIMAG, or it can also be obtained through experiments. Here, only the corresponding regional rate in the liquid silicon flow is given as an example. Since the existing rates in the liquid silicon flow can be obtained by various methods such as simulation and theoretical calculation, the obtaining method is not specifically limited here.

[0068] The "outer third boundary layer" refers to a layer of liquid silicon adjacent to the third boundary layer, and the outer third boundary layer has the highest liquid silicon flow rate nearby.

[0069] 8) Equilibrium segregation coefficient and effective segregation coefficient :

[0070] In this application document, the equilibrium segregation coefficient is the solid-liquid segregation coefficient, which refers to the ratio of the concentration of impurities in the solid-phase thin layer to the concentration of impurities in the liquid-phase thin layer at the interface between crystalline silicon and liquid silicon. The effective segregation coefficient refers to the ratio of the concentration of impurities in the solid-phase thin layer at the interface between crystalline silicon and liquid silicon to the average concentration in the entire liquid phase. During crystal growth, there is the following relationship:

[0071]

[0072] Where:

[0073] : Effective segregation coefficient;

[0074] : Equilibrium segregation coefficient;

[0075] D : The equivalent diffusion coefficient of the impurity in liquid silicon;

[0076] : The growth rate of the silicon single crystal in the z direction (pulling rate);

[0077] : The thickness of the third boundary layer.

[0078] 9) Front angle β (of the convex rib):

[0079] Take the cross-section of the convex rib perpendicular to the length direction of the convex rib. The angle between the line of the surface that pushes the liquid silicon to move and the line segment between the two end points of its bottom surface is defined as the front angle β (of the convex rib).

[0080] 10) Rear angle γ (of the convex rib):

[0081] Take the cross-section of the convex rib perpendicular to the length direction of the convex rib. The angle between the line that deviates from the movement direction of the convex rib and the line segment between the two end points of its bottom surface is defined as the rear angle γ (of the convex rib).

[0082] II. Invention Objectives and Invention Content:

[0083] The objectives of the present invention include at least one of the following three. First, controlling the oxygen content and its longitudinal distribution of the Czochralski silicon single crystal; second, increasing the effective segregation coefficient when pulling an n-type conductive silicon single crystal , making it closer to 1 to reduce the axial impurity distribution gradient of the n-type silicon single crystal; third, improving the flatness of the crystallization plane of the silicon single crystal rod.

[0084] The content of the present invention includes:

[0085] In a first aspect, the present invention provides a quartz crucible for pulling single crystal silicon, the inner cavity of the xy plane cross-section thereof is quasi-circular, on the inner cavity side surface of the quartz crucible, one or more first convex ridges protruding relative to the inner cavity side surface of the quartz crucible are arranged in a rotation around the z-axis, the rotation direction of the first convex ridge is opposite to the rotation direction of the quartz crucible, and the first convex ridge has a first convex ridge pressing angle. , ; the height of the first convex ridge is greater than the thickness of the first boundary layer of liquid silicon on the inner cavity side surface of the quartz crucible . Observing an intersection point p of the contour line of the first convex ridge protruding from the inner cavity side surface of the quartz crucible and the xoz plane, when the quartz crucible rotates by an angular radian Δθ around its vertical symmetry axis, causing the intersection point p to move a distance Δl along the first convex ridge in the xoz plane, the angle α near the point p is defined as the pressing angle:

[0086]

[0087] where d is the distance from the z-axis to the intersection point p.

[0088] The height of the first convex ridge .

[0089] Alternatively, the height of the first convex ridge (optionally 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 27mm, 30mm, etc.).

[0090] Alternatively, the height of the first convex ridge (optionally 5mm, 5mm, 6mm, 7mm, 8mm, etc.).

[0091] Alternatively, the height of the first convex ridge .

[0092] Alternatively, the first convex ridge has a first convex ridge pressing angle which is (optionally 46°, 49°, 52°, 55°, 58°, 61°, 64°, 67°, 70°, 75°, 80°, 85°, etc.).

[0093] Alternatively, the first convex ridge has a first convex ridge pressing angle which is (optionally 10°, 11°, 16°, 21°, 26°, etc.).

[0094] Alternatively, the first convex ridge has a first convex ridge pressing angle which is (optionally 30°, 31°, 36°, 40°, 44°, 45°, etc.).

[0095] Further, the first convex rib pressing angle and the angular velocity of the rotation of the quartz crucible , the crucible radius R, and the liquid silicon thermal convection rising rate of the outer layer of the first boundary of the liquid silicon at the first convex rib on the inner cavity side surface of the quartz crucible have the following relationship:

[0096]

[0097] Where:

[0098] : The first convex rib pressing angle Coefficient of correlation, ;

[0099] : The angular velocity of the rotation of the quartz crucible;

[0100] R: Crucible radius;

[0101] : The liquid silicon thermal convection rising rate of the outer layer of the first boundary of the liquid silicon when there is no convex rib at the first convex rib on the inner cavity side surface of the quartz crucible;

[0102] Preferably, the cross-section of the first convex rib is a serrated asymmetric cross-section, and its first convex rib front angle is , 75° ≤ ≤ 95° (optional values are 75°, 77°, 82°, 85°, 87°, 89°, 91°, 93°, 95°, etc.); its first convex rib rear angle is , 5° ≤ < 75° (optional values are 5°, 9°, 11°, 24°, 33°, 43°, 55°, 62°, 68°, 71°, 74°, etc.);

[0103] Optionally, for the first convex rib arranged in rotation on the inner cavity side wall of the quartz crucible, the distance s between two adjacent first convex ribs (optional values are 21mm, 27mm, 33mm, 36mm, 38mm, 40mm, 49mm, 50mm, etc.).

[0104] Optionally, for the first convex rib arranged in rotation on the inner cavity side wall of the quartz crucible, the distance s between two adjacent first convex ribs (optional values are 51mm, 54mm, 62mm, 70mm, 78mm, 90mm, 110mm, 140mm, 170mm, 200mm, etc.).

[0105] Second aspect, the present invention provides a second quartz crucible for pulling single crystal silicon. The inner cavity of the quartz crucible is quasi-circular in the xy plane cross-section. The bottom surface of the inner cavity of the quartz crucible is a quasi-rotating surface. One or more second ridges protruding relative to the bottom surface of the inner cavity of the quartz crucible are provided on the bottom surface of the inner cavity. The second ridges are arranged in a rotation around the z-axis, and the rotation direction of the second ridges is opposite to the rotation direction of the quartz crucible. The second ridges have a second ridge pressing angle , and the second ridge pressing angle gradually decreases as the distance r from the z-axis increases, and the change range is 2° < < 78° (which can be optionally 3°, 5°, 9°, 11°, 24°, 33°, 43°, 55°, 62°, 68°, 71°, 74°, 77°, etc.). Observe an intersection point p between the contour line of the second ridge protruding from the bottom surface of the inner cavity of the quartz crucible and the xoz plane. When the quartz crucible rotates by an angular radian Δθ around its vertical symmetry axis, the intersection point p moves a distance Δl along the second ridge in the xoz plane. Then, the angle α near the point p is defined as the pressing angle:

[0106]

[0107] where d is the distance from the z-axis to the intersection point p.

[0108] Furthermore, the second ridges on the bottom surface of the inner cavity of the quartz crucible are helical lines with the z-axis as the axis at the bottom of the inner cavity of the quartz crucible.

[0109] Preferably, the height of the protrusion of the second ridge is , 5mm ≤ < 9mm (which can be optionally 5mm, 6mm, 8mm, etc.);

[0110] Alternatively, the height of the protrusion of the second ridge is , 9mm ≤ ;

[0111] Alternatively, the height of the protrusion of the second ridge is , the height is greater than the thickness of the second boundary layer of the liquid silicon at the bottom surface of the inner cavity of the quartz crucible (which can be optionally 11mm, 13mm, 15mm, 17mm, 19mm, etc.);

[0112] Preferably, the cross-section of the second ridge is a serrated asymmetric cross-section, and its second ridge front angle , 75° ≤ ≤ 95° (which can be optionally 75°, 77°, 82°, 85°, 87°, 89°, 91°, 93°, 95°, etc.), and its second ridge rear angle , 5° ≤ < 75° (optionally 5°, 9°, 11°, 24°, 33°, 43°, 55°, 62°, 68°, 71°, 74°, etc.);

[0113] Further, the second ridge pressing angle of the second ridge near the side wall end of the quartz crucible is less than the second liquid silicon pressing angle of the second ridge near the z-axis end .

[0114] In a third aspect, the present invention provides a quartz crucible for pulling single crystal silicon by the Czochralski method. The inner cavity of the cross-section in the xy plane is quasi-circular, and the bottom surface of the inner cavity of the quartz crucible is a quasi-rotating surface. On the side surface of the inner cavity of the quartz crucible, one or more first ridges protruding relative to the side surface of the inner cavity of the quartz crucible are arranged in a rotation around the z-axis as described above; and, on the bottom surface of the inner cavity of the quartz crucible, one or more second ridges protruding relative to the bottom surface of the inner cavity of the quartz crucible are provided as described above. Understandably, the quartz crucible for pulling single crystal silicon in the third aspect combines the relevant designs and effects of the quartz crucibles for pulling single crystal silicon in the first and second aspects, and can have a better effect of coordinated cooperation.

[0115] In a fourth aspect, the present invention provides a method for growing a single crystal silicon ingot by the Czochralski method. Using the quartz crucible provided in the first aspect, during the crystal growth process, the quartz crucible rotates around the central symmetry axis z. For the quartz crucible with the first ridge being right-handed, the rotation direction of the crucible is left-handed; for the quartz crucible with the first ridge being left-handed, the rotation direction of the crucible is right-handed.

[0116] Further, the angular velocity ω of the rotation of the quartz crucible, the first ridge pressing angle of the first ridge of the quartz crucible , the crucible radius R, and the first boundary outer layer heat convection rising rate of the liquid silicon at the first ridge of the side surface of the inner cavity of the quartz crucible have the following correlation relationship:

[0117]

[0118] During the pulling process, as the liquid silicon level drops, decreases, and the angular velocity of the rotation of the quartz crucible decreases.

[0119] Further, the decreasing range of the product of the angular velocity ω of the rotation of the quartz crucible and the crucible radius R is:

[0120] When it is, 400 mm / second > ωR > 35 mm / second;

[0121] When when it is 140 mm / second > ωR > 25 mm / second;

[0122] When it is 100 mm / second > ωR > 17 mm / second.

[0123] Furthermore, in coordination with the product of the angular velocity ω of the rotation of the quartz crucible and the crucible radius R, the crystal rotation change range is 0 to 4 revolutions, in the opposite direction to the crucible rotation direction.

[0124] From the correlation relationship between the angular velocity ω of the rotation of the quartz crucible, the first convex edge pressing angle of the first convex edge of the quartz crucible, the crucible radius R, and the first boundary outer layer thermal convection rising rate of the liquid silicon at the first convex edge of the inner cavity side surface of the quartz crucible, in the single crystal silicon preparation method, the equivalent angular velocity ω of the crucible rotation, which is closely related to the formation of the pressed liquid silicon flow, is used as an important adjustment parameter in the control method, which can simplify the process control process and is easier to achieve the ideal control effect.

[0125] Furthermore, in coordination with the pressing and restraint of the liquid silicon thermal convection by the first convex edge, it no longer relies on the inertial centrifugal force of the crystal rotation to press the liquid silicon thermal convection. Therefore, the rotation speed of the crystal rotation is set to 0 to 4 revolutions per minute, which is much lower than 8 to 12 revolutions per minute in the prior art. According to the relationship between the effective segregation coefficient and the equilibrium segregation coefficient:

[0126]

[0127] The beneficial effect of the lower crystal rotation rate is that the effective diffusion coefficient D decreases, and the movement speed of the third boundary outer layer liquid silicon relative to the single crystal silicon decreases, and thickens.

[0128] The known solid-liquid equilibrium segregation coefficient of the impurity oxygen , is greater than 1. Therefore, the result of thickening is that the solid-liquid effective segregation coefficient of the impurity oxygen decreases and approaches 1. The decrease in the effective segregation coefficient reduces the impurity oxygen in the single crystal silicon;

[0129] On the other hand, the solid-liquid equilibrium segregation coefficient of the n-type impurity in the n-type single crystal silicon is less than 1. Therefore, the result of thickening is that the solid-liquid effective segregation coefficient of the n-type impurity increases and approaches 1. The increase in the effective segregation coefficient improves the doping efficiency at the head of the n-type single crystal silicon and equalizes the doping concentration of the whole single crystal.

[0130] Fifth aspect, the present invention provides another method for growing a silicon single crystal ingot by the Czochralski method. Using the quartz crucible provided in the second aspect, during crystal growth, the quartz crucible rotates about the central symmetry axis z. For the quartz crucible having the second convex ridge with right-handedness, the rotation direction of the crucible is left-handed; for the quartz crucible having the second convex ridge with left-handedness, the rotation direction of the crucible is right-handed.

[0131] Further, during the pulling of the silicon single crystal, as the liquid silicon level drops, the convection intensity of the liquid silicon decreases. Correspondingly, the rotation speed of the crucible decreases.

[0132] Further, in cooperation with the restraint and confinement of the second convex ridge on the thermal convection of the liquid silicon, replacing or partially replacing the inertial centrifugal force of the crystal rotation to suppress the thermal convection of the liquid silicon and homogenize the liquid silicon is beneficial to reducing the rotation speed of the crystal rotation and obtaining the beneficial effects brought about by the aforementioned reduction of the crystal rotation.

[0133] Specifically, the first object of the present invention is to control the oxygen content and its longitudinal distribution of the Czochralski silicon single crystal.

[0134] To control the oxygen content of the silicon single crystal, first, by increasing the thickness of the first boundary layer and reducing the oxygen impurity concentration gradient in the boundary layer; second, by suppressing the thermal convection intensity and reducing the effective diffusion coefficient of oxygen impurities into the liquid silicon; third, by increasing the thickness of the third boundary layer and suppressing the flow rate of the liquid silicon in the outer layer of the third boundary to reduce the solid-liquid segregation coefficient of impurity oxygen.

[0135] To control the longitudinal distribution of the oxygen content of the silicon single crystal, it is controlled by changing the rotation of the crucible. The specific description is as follows:

[0136] Since the oxygen in the liquid silicon mainly comes from the quartz crucible, especially the high-temperature area of the crucible closest to the heater, the buoyancy of the thermal convection of the liquid silicon caused by high temperature is several to dozens of times that of other forces (such as the inertial centrifugal force generated by the rotation of the crucible and the crystal, the surface tension of the liquid silicon, the blowing and shearing force of argon, the advection force of the liquid silicon caused by crystallization, etc.). Therefore, in the prior art without the participation of a magnetic field, the balance and restraint of each force on the buoyancy of the thermal convection are relatively insufficient, and the eddy current generated by the thermal convection liquid silicon in the liquid silicon / crucible boundary layer excessively scours the quartz crucible wall, bringing a large amount of oxygen ions into the liquid silicon and entering the crystal, increasing the oxygen content of the silicon single crystal. The buoyancy of the thermal convection of the liquid silicon is proportional to the height of the liquid surface in the heating section of the liquid silicon. Therefore, the oxygen content at the head of the silicon single crystal is higher.

[0137] One of the ways for the present invention to control the oxygen content and its longitudinal distribution of the Czochralski silicon single crystal is that the first convex ridge on the inner sidewall of the quartz crucible is arranged to rotate around the z-axis, and the first convex ridge has a pressing angle of the first convex ridge of the liquid silicon , 10° ≤85°; The height of the first convex rib is greater than the thickness of the first boundary layer of the liquid silicon on the side surface of the inner cavity of the crucible. .

[0138] The rotationally arranged first convex rib, in cooperation with the rotation direction of the quartz crucible (for a crucible with a right-handed first convex rib, the crucible rotates to the left; for a crucible with a left-handed first convex rib, the crucible rotates to the right), generates a reverse pressing force on the natural thermal convection of the first outer boundary layer of the liquid silicon, balances and restricts the natural thermal convection generated by buoyancy, reduces the intensity of the eddy current, alleviates the erosion of the liquid silicon eddy current on the quartz crucible wall, and increases the thickness of the first boundary layer. , reducing the total amount of impurity oxygen entering the liquid silicon from the quartz crucible wall. The height of the first convex rib is greater than the thickness of the first boundary layer of the liquid silicon on the side surface of the inner cavity of the crucible. , which can cross the first boundary layer to form a more effective suppression of the high-speed thermal convection of the first outer boundary layer of the liquid silicon, thereby more effectively reducing the total amount of impurity oxygen entering the liquid silicon from the quartz crucible wall.

[0139] It can be understood that the pressing angle of the first convex rib has a certain angle, which can enable the first convex rib to have the effect of suppressing the thermal convection of the liquid silicon in the first outer boundary layer. Since the range of the optimal pressing angle of the first convex rib corresponding to different technical states and crystal pulling process parameters of the quartz crucible can be different, the following different pressing angle ranges are all optional.

[0140] Specifically, from the formula , the pressing angle of the first convex rib is positively correlated with the rising rate of the thermal convection of the liquid silicon in the first outer boundary layer of the liquid silicon when there is no convex rib at the position of the first convex rib on the side surface of the inner cavity of the quartz crucible (the rising rate of the natural thermal convection of the outer boundary layer ), and for the liquid silicon at different depths of the quartz crucible, the rising rate of the natural thermal convection of its outer boundary layer can be different. A larger can be selected at a higher position, such as 45° < ≤85°; A smaller can be selected at a lower position, such as 10° < ≤30°.

[0141] Furthermore, since the suppression of the thermal convection of the liquid silicon is jointly maintained by the pressing angle and the crucible rotation linear velocity ωR, when it is constant, is inversely proportional to ωR. Therefore, when some embodiments require a higher crucible rotation speed (such as when a more uniform distribution of impurities in the liquid silicon is required), a smaller pressing angle of the first convex rib can be selected. , for example, select 10° < ≤ 30°; Similarly, when some embodiments require a lower crucible rotation speed (such as when pursuing a more stable flow field and thermal field distribution), a larger pressing angle of the first convex rib can be selected , for example, select 45° < ≤ 85°.

[0142] The height of the first convex rib can be selected as . Greater than the first boundary layer thickness , from the formula it can be seen that is a function of the position on the inner wall of the crucible, and the first boundary layer thickness at different positions of the crucible is different. Therefore, different combinations of the height ranges of different first convex ribs can obtain a better comprehensive effect. The height of the first convex rib , are all optional different heights of the first convex rib related to the first boundary layer thickness at different positions of the crucible range. Understandably, the designer can either design different first convex ribs with different heights , or design different segments of the same first convex rib to have different heights which can be selected within the different height ranges. can be selected within the different height ranges.

[0143] Select different pressing angles of the first convex rib , and different heights of the first convex rib , to provide different pressing intensities for the thermal convection of liquid silicon, so as to achieve a better balance and restrain the natural thermal convection generated by buoyancy, reduce the intensity of the thermal convection of liquid silicon, reduce the erosion of the liquid silicon on the quartz crucible wall, increase the thickness of the first boundary layer, and achieve the reduction of the total amount of impurity oxygen entering the liquid silicon from the quartz crucible wall at each stage of crystal pulling.

[0144] The design of different angle ranges and height ranges of the first convex rib can simplify the regulation process and more easily achieve the ideal control effect. From the example, when a relatively stable low-speed crucible rotation is required, the pressing angle of the first convex rib can select a larger value within the range with better effects, for example, select 70° within the range of 45° < ≤ 85°. Only a small change in the crucible rotation is required at different times of crystal pulling to achieve the required different pressing effects; Similarly, when a higher rotation speed of the crucible is required, for example, to meet the centripetal driving requirements of the second convex rib at the bottom of the crucible, the pressing angle of the first convex rib can select a smaller value within the range with better effects, for example, within the range of 10° < Select 26° within the range of ≤30°. Similarly, by slightly changing the crucible rotation at different stages of crystal pulling, different required pressing effects can be achieved.

[0145] Based on the correlation between the angular velocity ω of the quartz crucible rotation and the upward heat convection rate of the first boundary outer layer of the liquid silicon at the first convex rib on the inner cavity side surface of the quartz crucible In the silicon single crystal preparation method, taking the equivalent angular velocity ω of the crucible rotation, which is closely related to the formation of the pressed liquid silicon flow, as an important adjustment parameter in the control method can simplify the process regulation process and more easily achieve the ideal control effect.

[0146] In a preferred solution, the cross-section of the first convex rib is a serrated asymmetric cross-section, with a relatively steep front angle of the first convex rib of the "serration" and a relatively gentle rear angle of the first convex rib. The beneficial effects of such an arrangement are that it is beneficial to form a relatively gentle laminar vortex between the first convex ribs, preventing the formation of violent turbulent vortices that cause excessive impact and corrosion on the quartz crucible wall; it is beneficial to minimize the contact area between the liquid silicon and the crucible and reduce the way for impurity oxygen to enter the liquid silicon.

[0147] In a preferred solution, the distance s between the two first convex ribs In another preferred solution, the distance s between the two first convex ribs Both are for adapting to the design requirements of crucibles of different sizes and first convex ribs of different heights On the premise of meeting the need for heat convection pressing of the liquid silicon, the inner surface area of the crucible increased by the first convex rib is minimized as much as possible to reduce the adverse impact on reducing the oxygen content caused by the increase in the contact area between the crucible and the liquid silicon.

[0148] In addition to the above points, since the first convex rib enhances the rotational flow effect of the liquid silicon surface with the crucible rotation, extending the path and time for the liquid silicon to flow from the crucible wall to the silicon crystal, more oxygen dissolved in the liquid silicon volatilizes into the argon atmosphere in the furnace in the form of SiO vapor, which is also beneficial to reducing the oxygen content of the silicon single crystal.

[0149] The second way to control the oxygen content and its longitudinal distribution of the Czochralski silicon single crystal in the present invention is to provide one or more second convex ribs on the inner bottom of the quartz crucible, arranged in a rotation around the z-axis, with the rotation direction of the second convex rib opposite to that of the quartz crucible, and the pressing angle gradually decreases with the increase of the distance from the z-axis, and the change range is 2° < < 78°, The change range of the angle depends on the type and number of the spiral lines.

[0150] The second convex rib, in coordination with the rotation of the quartz crucible (for a crucible with a right-handed convex rib, the crucible rotates to the left; for a crucible with a left-handed convex rib, the crucible rotates to the right), the second convex rib pressing angle generates a centripetal pressing liquid silicon flow opposite to the direction of the thermal convection of the liquid silicon at the bottom of the crucible, balancing and restraining the thermal convection generated by the buoyancy of the liquid silicon, thereby reducing the intensity of the erosion of the quartz crucible wall by the liquid silicon and increasing the thickness of the first boundary layer. This achieves the purpose of reducing the total amount of impurity oxygen entering the liquid silicon from the quartz crucible wall.

[0151] The second convex rib pressing angle The gradual change angle and spiral arrangement are both for improving the pressing efficiency of the liquid silicon.

[0152] The height of the second convex rib The beneficial effects of the setting and the setting of the cross-section being a serrated asymmetric cross-section are the same as those of the first convex rib.

[0153] The third way of the present invention to control the oxygen content and its longitudinal distribution in the Czochralski single crystal silicon is known that under the action of only crystal rotation, the oxygen impurity content in the single crystal silicon is proportional to the rotation speed of the crystal rotation. The reasons are as follows: 1) Crystal rotation transports more impurity oxygen to the crystallization interface; 2) Crystal rotation makes the effective segregation coefficient of oxygen closer to the equilibrium segregation coefficient of oxygen , and the equilibrium segregation coefficient of oxygen , therefore, more impurity oxygen will segregate into the single crystal silicon. Whether it is the first way or the second way of the present invention, due to the cooperation of the first convex rib pressing angle and the crucible rotation ωR replacing part of the function of crystal rotation, the crystal rotation has been greatly reduced until it becomes zero, so it is beneficial to reduce the oxygen impurity content in the single crystal silicon and make it uniform.

[0154] The second object of the present invention - to increase the effective segregation coefficient of n-type impurities is achieved as follows:

[0155] The impurity concentration on the crystal side of the crystallization interface of the single crystal silicon rod is determined by the doping concentration of the liquid silicon and the effective segregation coefficient of the impurity between the crystal and the liquid silicon , and the effective segregation coefficient and the equilibrium segregation coefficient have the following relationship:

[0156]

[0157] where is the effective segregation coefficient, is the equilibrium segregation coefficient, D is the equivalent diffusion coefficient of the n-type impurity in the liquid silicon, is the growth rate of silicon single crystal in the z direction (drawing speed), is the silicon single crystal / liquid silicon interface, and the thickness of the third boundary layer of liquid silicon, can be determined by the following empirical formula:

[0158]

[0159] wherein is the correlation coefficient, is the kinematic viscosity coefficient of liquid silicon is the relative movement speed of the liquid silicon in the third boundary outer layer relative to the silicon single crystal.

[0160] From the above two formulas, it can be obtained that when the relative movement speed of the liquid silicon in the third boundary outer layer relative to the crystal is low enough, the effective segregation coefficient will be closer to 1, and the segregation coefficient closer to 1 can reduce the longitudinal distribution concentration gradient of n-type impurities in the silicon single crystal ingot, and obtain a longer and heavier single n-type silicon single crystal rod.

[0161] The strong thermal convection of liquid silicon in the prior art increases the flow rate of the third boundary outer layer To resist the increase in the oxygen content of the silicon single crystal caused by thermal convection, a relatively high crystal rotation is introduced, and the inertial centrifugal force generated by the crystal rotation will also increase the flow rate of the third boundary outer layer , The increase of ( ) reduces the thickness of the liquid silicon boundary layer ( ) The reduction reduces the effective segregation coefficient of the dopant For n-type dopants such as phosphorus and antimony, the effective segregation coefficient decreases in the direction away from 1, increasing the longitudinal impurity concentration gradient of the silicon single crystal ingot, thereby limiting the drawing length of the silicon single crystal ingot and reducing the production rate.

[0162] With the aid of the vortex effect of the second convex rib at the bottom of the crucible, the present invention generates a centripetal and upward liquid silicon vortex from the bottom of the crucible. The vortex path is similar to the trumpet-shaped liquid flow generated upward by a vortex nozzle. The function of this liquid flow in the process can replace the function of crystal rotation, but it does not directly impact the liquid silicon near the crystallization interface, causing an increase in the flow rate of the boundary outer layer . Maintaining at a low level is beneficial to the increase of the liquid silicon boundary layer thickness ( ) The increase, ( ) The increase increases the effective segregation coefficient of the dopant Combined with the suppression of the thermal convection intensity of liquid silicon by the vortex effect of the second convex rib, while reducing the oxygen content of the silicon single crystal, an increased effective segregation coefficient (closer to 1) can be obtained, achieving the beneficial effect of reducing the longitudinal impurity concentration gradient of the silicon single crystal ingot.

[0163] The third objective of the present invention - to improve the flatness of the crystallization plane of the silicon single crystal rod - is achieved as follows:

[0164] The growth of silicon single crystals by the Czochralski method is a controlled crystal growth process. A seed crystal is introduced into the liquid silicon, and the crystal grows by the continuous transfer of atoms from the liquid phase to the solid phase at the solid-liquid interface in a specific crystal orientation. The growth conditions at the solidification front of the silicon single crystal can be described by the following formula:

[0165]

[0166] In the formula:

[0167] n: the vector perpendicular to the solid-liquid interface at the solidification front of the silicon single crystal (downward is positive);

[0168] : the growth rate of the silicon single crystal (along the vector n direction);

[0169] : the density of the silicon single crystal;

[0170] L: the latent heat of crystallization of silicon;

[0171] : the thermal conductivity of the silicon crystal;

[0172] : the thermal conductivity of the liquid silicon;

[0173] : the temperature gradient along the vector n direction on the silicon crystal side of the crystallization interface;

[0174] : the temperature gradient along the vector n direction on the liquid silicon side of the crystallization interface.

[0175] After the silicon single crystal enters the isodiameter stage during pulling, as the silicon single crystal rod grows, the heat dissipation path at the crystallization interface continuously becomes longer, the thermal resistance increases, and the temperature gradient on the silicon single crystal side of the crystallization interface continuously decreases. Since the thermal resistance of the heat dissipation path in the central part of the silicon single crystal ingot is greater, the decrease is also more. The crystal growth rate in the central part of the crystallization interface is lower than that in the edge part, making the crystallization interface concave.

[0176] To control the degree of concavity of the silicon single crystal crystallization interface, one of the measures is to increase the temperature of the liquid silicon around the silicon single crystal ingot to increase value, which reduces the rate of edge crystallization, but this will inevitably reduce the overall crystal pulling rate and productivity; the second measure is to reduce the crystal rotation speed in order to weaken the high-temperature liquid silicon flow that is forced to flow towards the central part of the crystallization interface of the silicon single crystal ingot due to inertial centrifugal force. By reducing the near the center of the crystallization interface, the purpose of reducing the pit depth of the silicon single crystal ingot is achieved. The disadvantage of this technical measure is that there are other functions in the process that need to be realized by the inertial centrifugal force of crystal rotation, such as counteracting buoyancy heat convection, prolonging the evaporation time of silicon oxide on the surface of liquid silicon, and reducing the oxygen content of the silicon single crystal ingot. The second measure involves more aspects in the process.

[0177] The technology of the present invention provides a method to solve this problem. By means of the centripetal vortex effect of the second convex ridge at the bottom of the crucible, a centripetal and upward liquid silicon vortex is generated from the bottom of the crucible. The vortex path is similar to the flared liquid flow generated upward by a vortex nozzle. Its influence on the flow direction of liquid silicon is similar to that of crystal rotation, but it has more beneficial advantages than crystal rotation. First, the power of the technology of the present invention is at the bottom of the liquid silicon, while the power of crystal rotation is on the surface of the liquid silicon. The present invention generates a centripetal and upward liquid silicon vortex from the bottom of the liquid silicon, and its rising path is in the shape of an upward flared opening, which does not directly impact the liquid silicon near the crystallization interface, and the liquid silicon with a lower temperature at the bottom of the crucible flows towards the vicinity of the crystallization interface. Therefore, it can achieve the purpose of reducing the temperature gradient of the liquid silicon near the crystallization interface , controlling the depth of the pit on the crystallization plane, and can slow down the reduction of the pulling speed compared with the prior art, and can also maintain a higher impurity concentration near the crystallization interface and improve the effective segregation coefficient of n-type impurities , reduce the effective segregation coefficient of impurity oxygen by reducing the disturbance to the central part of the crystallization interface. As mentioned above, this is especially beneficial for reducing the oxygen impurity content and pulling n-type silicon single crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0178] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, so they should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0179] Figure 1 It is a schematic longitudinal section structure diagram of a quartz crucible according to Embodiment 1 of the present invention.

[0180] Figure 2 It is a schematic longitudinal section structure diagram of a quartz crucible according to Embodiment 2 of the present invention.

[0181] Figure 3A top view schematic diagram of the bottom structure of the quartz crucible according to Embodiment 3 of the present invention.

[0182] Figure 4 A longitudinal sectional structure schematic diagram of the quartz crucible according to Embodiment 4 of the present invention.

[0183] Explanation of reference numerals in the drawings:

[0184] 1 - Quartz crucible; 11 - First convex rib; α1 - Pressing angle of the first convex rib; β1 - Front angle of the first convex rib; γ1 - Rear angle of the first convex rib; h1 - Height of the first convex rib; 12 - Second convex rib; α2 - Pressing angle of the second convex rib; β2 - Front angle of the second convex rib; γ2 - Rear angle of the second convex rib; h2 - Height of the second convex rib; 2 - Heater; 3 - Crucible rotation axis z-axis. Detailed implementation manners

[0185] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0186] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0187] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0188] In the description of the present invention, it should be noted that if terms such as "upper", "lower", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is 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 thus should not be construed as a limitation to the present invention.

[0189] Embodiment 1

[0190] An embodiment of the present invention provides a quartz crucible 1 for growing silicon single crystals by the Czochralski method, which is heated by a heater 2. The inner cavity of its xy-plane cross-section is quasi-circular. The diameter of the quartz crucible 1 is 840 mm and the height is 650 mm, of which the cylindrical part is 450 mm high and the bottom arc part is 200 mm high. On the surface of the inner cavity side wall of the quartz crucible 1, 18 first convex ribs 11 protruding from the surface of the inner cavity side wall of the crucible are arranged around the crucible rotation axis z-axis 3. The rotation direction of the first convex ribs 11 is right-handed, opposite to the rotation direction of the quartz crucible 1. The first convex ribs 11 have a first convex rib pressing angle α1 of 70°. The thickness δ1 of the first boundary layer of the liquid silicon on the side surface of the inner cavity of the quartz crucible is considered as 6 mm; the height h1 of the first convex rib is 16 mm; the cross-section of the first convex rib 11 is a serrated asymmetric cross-section, its first convex rib front angle β1 is 90°; its first convex rib rear angle γ1 is 12°; the vertical distance s between two first convex ribs 11 is 118 mm. When using the above crucible to grow silicon single crystals by the Czochralski method, the crucible rotation angular velocity is determined by the formula to determine the adjustment principle. The crucible rotation angular velocity in this embodiment is: 1.5 revolutions / min, and in the end section of crystal pulling, the crucible rotation angular velocity is: 0.5 revolutions / min.

[0191] The beneficial effects of this embodiment compared with the prior art are as follows:

[0192] 1) By means of the inhibitory effect of the first convex ribs 11 on the thermal convection of the liquid silicon, this embodiment weakens the impact and corrosion effect of the liquid silicon on the quartz crucible 1, increases the thickness of the first boundary layer δ1, and reduces the oxygen content in the silicon single crystal by 20% compared with the existing magnetic field-free Czochralski method;

[0193] 2) In this embodiment, the oxygen impurity concentration of the silicon single crystal can be simply adjusted by adjusting the angular velocity of the crucible rotation, so that the oxygen impurity concentrations at the head and tail of the silicon single crystal ingot are within the required range;

[0194] 3) With a relatively low crucible rotation, the thermal convection of the liquid silicon is constrained, and the flow field and thermal field in the crucible are stable.

[0195] 4) Compared with the prior art, this embodiment does not rely on the blowing and shearing force of the argon gas flow to inhibit the intensity of the thermal convection of the liquid silicon, which is beneficial to maintaining the stability of the silicon liquid surface temperature and its distribution, can reduce the consumption of argon gas, and reduce costs;

[0196] 5) Compared with the prior art, this embodiment does not rely on the inertial centrifugal force generated by the crystal rotation to inhibit the intensity of the thermal convection of the liquid silicon. When pulling n-type conductive silicon single crystals, it is beneficial to keep the n-type impurity concentration near the crystallization interface stable at a relatively high level, improve the effective segregation coefficient of n-type impurities , improve the doping uniformity, and improve the production efficiency; at the same time, reduce the effective segregation coefficient of impurity oxygen , and reduce the impurity oxygen content in the silicon single crystal.

[0197] Example 2

[0198] Example 2 of the present invention provides a quartz crucible 1 for growing single crystal silicon by the Czochralski method, which is substantially the same as that in Example 1. On the inner cavity side wall surface of the quartz crucible 1, eight first convex ridges 11 protruding relative to the inner cavity side wall surface of the crucible are arranged around the crucible rotation axis z-axis 3. The spiral direction of the first convex ridges 11 is right-handed, which is opposite to the spiral direction of the quartz crucible 1. The first convex ridge 11 has a first convex ridge pressing angle α1 of 26°, considering that the thickness δ1 of the first boundary layer of liquid silicon on the inner cavity side surface of the quartz crucible is 6 mm; the height h1 of the first convex ridge 11 is 24 mm. The cross section of the first convex ridge 11 is a serrated asymmetric cross section, its first convex ridge front angle β1 is 90°; its first convex ridge rear angle γ1 is 12°; the vertical distance s between two first convex ridges 11 is 118 mm. When using the above crucible to grow single crystal silicon by the Czochralski method, the crucible rotation angular velocity is determined by the formula to determine the adjustment principle. The crucible rotation angular velocity in this example is 2.5 revolutions / min, and the angular velocity at the end of crystal pulling is: 0.8 revolutions / min.

[0199] Beneficial effects compared with Example 1:

[0200] First, the first convex ridge pressing angle α1 in this example is relatively small. Its advantage is that it occupies a relatively small inner wall surface area of the crucible. Therefore, the total surface area of the crucible exposed in the liquid silicon is relatively small, and less impurity oxygen enters the liquid silicon through this way.

[0201] Second, the crucible rotation in this example is higher than that in Example 1, and it is easy to be compatible with the structure that requires a higher crucible rotation such as Example 3.

[0202] Example 3

[0203] As Figure 3 shown and referring to Figure 2 , Example of the present invention provides a quartz crucible 1 for growing single crystal silicon by the Czochralski method. The inner cavity cross section in the xy plane is quasi-circular. The diameter of the quartz crucible 1 is 840 mm and the height is 650 mm. Among them, the height of the cylindrical part is 450 mm, the height of the bottom arc part is 200 mm, the bottom arc is 840 mm, and the transition arc is 140 mm. On the inner cavity bottom surface of the quartz crucible 1, three second convex ridges 12 protruding relative to the inner cavity surface of the quartz crucible are symmetrically distributed at the center. The projection of the second convex ridges 12 in the xy plane is a part of an involute with the center of the base circle on the crucible rotation axis z-axis 3. The three arranged second convex ridges 12 are rotationally symmetrically arranged around the crucible rotation axis z-axis 3. Its second convex ridge pressing angle α2 continuously changes from 10° to 22° from the outside to the inside, and the pressing angle near the axis is greater than the pressing angle near the side wall.

[0204] In this embodiment, the height h2 of the second convex rib 12 that protrudes is 12 mm; the cross-section of the second convex rib 12 is a serrated asymmetric cross-section, its front angle β2 of the second convex rib is 90°, and the rear angle γ2 of the second convex rib is 30°; the second convex rib 12 is right-handed.

[0205] In this embodiment, during the growth of silicon single crystal, the quartz crucible 1 rotates about the crucible rotation axis z-axis 3 of the central symmetry axis, and for the quartz crucible 1 with a right-handed second convex rib 12, its crucible rotation direction is left-handed.

[0206] Beneficial effects of this embodiment:

[0207] 1) In this embodiment, by means of the restraint effect of the second convex rib 12 on the thermal convection of liquid silicon, the impact corrosion of the liquid silicon on the quartz crucible 1 is weakened, and the oxygen impurity content in the silicon single crystal is reduced by 10%. 2) Compared with the prior art, this embodiment does not rely on the blowing shear force of the argon gas flow to inhibit the intensity of the thermal convection of liquid silicon, which is beneficial to maintaining the stability of the temperature and its distribution of the silicon liquid surface, can reduce the consumption of argon gas, and reduce costs;

[0208] 3) Compared with the prior art, this embodiment does not rely on the inertial centrifugal force generated by crystal rotation to inhibit the intensity of the thermal convection of liquid silicon. When pulling an n-type conductive silicon single crystal, it is beneficial to keep the n-type impurity concentration near the crystallization interface stable at a relatively high level, increase the effective segregation coefficient of the impurity phosphorus from 0.35 to 0.4, improve the doping uniformity, and improve the production efficiency; at the same time, the effective segregation coefficient of the impurity oxygen can be reduced to further reduce the impurity oxygen content in the silicon single crystal.

[0209] 4) In this embodiment, on the one hand, the second convex rib 12 will generate a centripetal forced liquid silicon flow pressure near the bottom of the quartz crucible 1, and this forced liquid silicon flow pressure will restrain the thermal convection of the liquid silicon rising along the inner wall of the quartz crucible 1, reduce the intensity of the liquid silicon scouring the inner wall of the quartz crucible 1, and reduce the impurity oxygen entering the liquid silicon; on the other hand, this forced liquid silicon flow pressure, the eddy current formed by it has the effect of pumping the liquid silicon at a lower temperature at the bottom of the quartz crucible 1 to the central part of the silicon single crystal ingot, which can improve the flatness of the crystallization plane of the silicon single crystal ingot, and has the beneficial effects of reducing the internal stress in the crystal and improving the uniformity of the impurity distribution in the wafer.

[0210] Example 4

[0211] Embodiment 4 of the present invention provides a quartz crucible 1 for growing silicon single crystals by the Czochralski method, which is substantially the same as that in Embodiment 1. The difference is that the first pressing angles α1 of the upper and lower parts of the first convex rib 11 are different. The angle α1 of the upper half of the first pressing angle α1 is 80°, and the lower half transitions to α1 = 20°. The beneficial effect is that from the beginning stage to the end stage of crystal pulling, the quartz crucible 1 can operate at a substantially same crucible rotation angular velocity ω, which is beneficial to the stable operation of the process.

[0212] In summary, compared with the prior art technical solution for controlling the oxygen content in a silicon single crystal ingot by applying an external magnetic field, the technical solution provided by the present invention has significant cost advantages and cost reduction potential, and is of great significance to the development of the industry.

[0213] The above embodiments are only preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A quartz crucible for Czochralski silicon single crystal, the inner cavity of its xy plane cross-section is quasi-circular, and on the inner cavity side surface of the quartz crucible, a plurality of first convex edges protruding relative to the inner cavity side surface of the quartz crucible are arranged in a rotation around the z-axis. It is characterized in that, The helix direction of the first convex rib is opposite to that of the quartz crucible, and the first convex rib has a first convex rib pressing angle , ; the height of the first convex rib is greater than the thickness of the first boundary layer of liquid silicon on the inner cavity side surface of the quartz crucible ; observing an intersection point p between the contour line of the first convex rib protruding from the inner cavity side surface of the quartz crucible and the xoz plane, when the quartz crucible rotates by a radian Δθ around its vertical symmetry axis, causing the intersection point p to move a distance Δl along the first convex rib in the xoz plane, the angle α near the point p is defined as the pressing angle: Where d is the distance from the z axis to the intersection point p.

2. The quartz crucible according to claim 1, characterized in that The height of the first convex rib is or .

3. The quartz crucible according to claim 1, characterized in that, The first convex rib has a first convex rib pressing angle is .

4. The quartz crucible according to claim 1, characterized in that, The first convex rib has a first convex rib pressing angle is or .

5. The quartz crucible according to claim 1, characterized in that, The first convex rib pressing angle is related to the angular velocity of the rotation of the quartz crucible , the crucible radius R, and the liquid silicon heat convection rising rate of the outer layer of the first boundary of the liquid silicon at the first convex rib on the inner cavity side surface of the quartz crucible There is the following relationship: in: : First convex rib pressing angle Correlation coefficient, ; : Angular velocity of quartz crucible rotation; R: crucible radius; : The thermal convection rising rate of the liquid silicon in the outer layer of the first boundary of the liquid silicon when there is no convex rib at the first convex rib on the inner cavity side surface of the quartz crucible.

6. The quartz crucible according to claim 1, characterized in that, The first ridge located on the side surface of the inner cavity of the quartz crucible has at least one of the following characteristics: 1) The cross-section of the first convex rib is a serrated asymmetric cross-section, and its front angle of the first convex rib is , 75° ≤ ≤ 95°; its rear angle of the first convex rib is , 5° ≤ < 75°; 2) The distance s between two adjacent ones of the first ridges rotatably arranged on the inner cavity side surface of the quartz crucible, ; or, the distance s between two adjacent ones of the first ridges rotatably arranged on the inner cavity side surface of the quartz crucible, .

7. A quartz crucible for Czochralski silicon single crystal, the inner cavity of its xy plane cross-section is quasi-circular, and the bottom surface of the inner cavity of the quartz crucible is a quasi-rotational surface, characterized in that, On the bottom surface of the inner cavity of the quartz crucible, one or more second convex ridges protruding relative to the bottom surface of the inner cavity of the quartz crucible are provided. The second convex ridges are arranged to rotate around the z-axis, and the rotation direction of the second convex ridges is opposite to that of the quartz crucible. The second convex ridges have a second convex ridge pressing angle , and the second convex ridge pressing angle gradually decreases as the distance r from the z-axis increases, and the change range is 2° < < 78°. Observe an intersection point p between the contour line of the second convex ridge protruding on the bottom surface of the inner cavity of the quartz crucible and the xoz plane. When the quartz crucible rotates by a radian Δθ around its vertical symmetry axis from the 0 azimuth, it causes the intersection point p to move a distance Δl along the second convex ridge in the xoz plane. Then, the angle α near the point p is defined as the pressing angle: Where d is the distance from the z axis to the intersection point p.

8. The quartz crucible according to claim 7, characterized in that, The second convex ridge on the bottom surface of the inner cavity of the quartz crucible is a spiral line with the z-axis as the axis.

9. The quartz crucible according to claim 7, characterized in that, The second ridge on the bottom surface of the inner cavity of the quartz crucible has at least one of the following characteristics: 1) The height of the raised second convex rib is , the height is greater than the thickness of the second boundary layer of liquid silicon at the bottom surface of the inner cavity of the quartz crucible , 5 mm ≤ <9 mm; or, the height of the raised second convex rib is , the height is greater than the thickness of the second boundary layer of liquid silicon at the bottom surface of the inner cavity of the quartz crucible , 9 mm ≤ <11 mm; or, the height of the raised second convex rib is , the height is greater than the thickness of the second boundary layer of liquid silicon at the bottom surface of the inner cavity of the quartz crucible , ; 2) The cross-section of the second convex rib is a serrated asymmetric cross-section, and its front angle of the second convex rib , 75° ≤ ≤ 95°; its rear angle of the second convex rib , 5° ≤ < 75°; 3) The second rib pressing angle of the second rib near the side wall end of the quartz crucible is less than the second rib pressing angle of the second rib near the z-axis end .

10. A quartz crucible for Czochralski silicon single crystal, the inner cavity of its xy plane cross-section is quasi-circular, and the bottom surface of the inner cavity of the quartz crucible is a quasi-rotational surface, characterized in that, On the side surface of the inner cavity of the quartz crucible, a plurality of first ridges as described in any one of claims 1 to 6 are arranged rotating around the z-axis and protrude relative to the side surface of the inner cavity of the quartz crucible; and, on the bottom surface of the inner cavity of the quartz crucible, one or more second ridges as described in any one of claims 7 to 9 are arranged and protrude relative to the bottom surface of the inner cavity of the quartz crucible.

11. A method for growing a silicon single crystal ingot by the Czochralski method, characterized in that, Using the quartz crucible described in any one of claims 1 to 6, during the crystal growth process, the quartz crucible rotates around the central symmetry axis z, and the quartz crucible with the first right-handed convex ridge rotates in a left-handed direction; the quartz crucible with the first left-handed convex ridge rotates in a right-handed direction.

12. The method for growing a silicon single crystal ingot by the Czochralski method according to claim 11, wherein, The angular velocity ω of the rotation of the quartz crucible and the first convex edge pressing angle of the first convex edge of the quartz crucible , the crucible radius R, and the heat convection rising rate of the first boundary outer layer of the liquid silicon at the first convex edge on the inner cavity side surface of the quartz crucible have the following correlation: During the drawing process, as the liquid silicon level drops, decreases, and the angular velocity of the quartz crucible rotation decreases progressively.

13. The method for growing a silicon single crystal ingot by the Czochralski method according to claim 12, characterized in that, The decreasing range of the product of the angular velocity ω of the quartz crucible and the crucible radius R is: When it is 400 mm / sec > ωR > 35 mm / sec; When it is 140 mm / sec > ωR > 25 mm / sec; When it is 100 mm / sec > ωR > 17 mm / sec.

14. The method for growing a silicon single crystal ingot by the Czochralski method according to claim 13, characterized in that, According to the product of the angular velocity ω of the quartz crucible and the radius R of the crucible, the crystal rotation speed varies in the range of 0 to 4 revolutions, which is opposite to the rotation direction of the crucible.

15. A method for growing a silicon single crystal ingot by the Czochralski method, characterized in that, Using the quartz crucible described in any one of claims 7 to 10, during the crystal growth process, the quartz crucible rotates around the central symmetry axis z, and the quartz crucible with the second right-handed convex ridge rotates in a left-handed direction; the quartz crucible with the second left-handed convex ridge rotates in a right-handed direction.

16. The method for growing a silicon single crystal ingot by the Czochralski method according to claim 15, characterized in that, During the drawing process, as the liquid silicon level drops, the angular velocity of the rotation of the quartz crucible decreases.

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