Quartz crucible for czochralski silicon single crystal and method for growing silicon single crystal ingot by czochralski method

Abstract

The invention relates to the technical field of silicon single crystal preparation, and provides a quartz crucible for czochralski silicon single crystal and a method for growing a silicon single crystal ingot, one or more first convex edges protruding relative to the side surface of an inner cavity of the quartz crucible are arranged on the side surface of the inner cavity of the quartz crucible, and the first convex edge pressing angle alpha is larger than or equal to 10 degrees and smaller than or equal to 85 degrees; the height of the first rib is larger than the thickness of a first boundary layer of liquid silicon on the side surface of the inner cavity of the quartz crucible, or one or more second ribs protruding relative to the surface of the bottom of the inner cavity of the quartz crucible are arranged on the surface of the bottom of the inner cavity of the quartz crucible, a second rib pressing angle alpha 2 is formed, and the second rib pressing angle alpha 2 is gradually decreased along with increase of the distance r from the z-axis; the change range is that alpha 2 is more than 2 degrees and less than 78 degrees, so that the liquid silicon flow is pressed, and the oxygen content is reduced. In the preparation method of the silicon single crystal, the crucible rotation equivalent angular velocity omega is used as an important adjustment parameter in the control method, so that the process regulation process can be simplified, and an ideal control effect can be achieved more easily.

Description

Technical Field

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

[0002] The existing technology 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, it also has the following three shortcomings in terms of oxygen content, axial impurity concentration gradient of n-type silicon single crystal rods, and uniformity of internal stress and radial impurity distribution of silicon single crystal rods: First, since a quartz crucible is used 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 in the quartz crucible to enter the liquid silicon, resulting in a high content of impurity oxygen in the silicon single crystal; and since the change in the liquid silicon liquid level during the crystal pulling process affects the intensity of the liquid silicon thermal convection, and the segregation coefficient of the impurity oxygen is greater than 1, the longitudinal impurity oxygen distribution of the entire silicon single crystal rod is uneven, and the controllability of the oxygen impurity distribution is poor.

[0003] Too high an oxygen content in silicon single crystals will produce greater stress, causing the silicon wafer to warp and break, and inducing defects such as dislocations and stacking faults. In the production of silicon photovoltaic cells, excessive oxygen content and defect density will reduce the minority carrier lifetime of silicon single crystal materials and reduce the photoelectric conversion efficiency of solar cells. An increase in the oxygen content in silicon single crystals will also lead to an increase in the photoinduced degradation trend of silicon photovoltaic cells. The poor controllability of impurity oxygen distribution leads to poor product quality consistency.

[0004] Second, when growing n-conductive type silicon single crystals in the prior art, 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. In addition, during the process of pulling the silicon single crystal, the content of impurity phosphorus in the liquid silicon will become higher and higher, resulting in higher and higher impurity concentration at the tail of the silicon single crystal rod, which exceeds the quality control range, ultimately limiting the length of the silicon single crystal rod and reducing productivity.

[0005] Third, when growing silicon single crystals in the prior art, due to the poor heat dissipation conditions in the center of the growth interface and the high temperature of the liquid silicon in the center, the growth interface of the crystal is concave. The concave crystal surface will produce high crystal internal stress in the silicon single crystal and silicon wafer. Excessive crystal internal stress will destroy the growth environment of the silicon single crystal and is the 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 impurities in the wafer are unevenly distributed, often in the form of concentric defects. The defects lead to reduced photoelectric conversion efficiency and reliability of silicon photovoltaic cells.

[0006] The existing technical measures for controlling the oxygen content and distribution uniformity of CZ silicon single crystals include two categories: oxygen control with magnetic field and oxygen control without magnetic field. The former achieves the purpose of oxygen control by placing silicon melt in a certain magnetic field environment and weakening the thermal convection movement of liquid silicon by the Lorentz force. This measure is effective in controlling oxygen, but the equipment and operation costs are relatively high. The latter controls oxygen by adopting appropriate thermal field distribution, crucible position, crucible rotation, crystal rotation and other process means, which has a lower cost, but is closely related to other technical indicators of silicon single crystals, such as crystal interface shape, impurity distribution, crystal defect requirements, etc. Therefore, the regulation is complicated and it is difficult to achieve the ideal control effect.

[0007] The prior art method for controlling the axial doping concentration distribution of n-dopant phosphorus in silicon single crystal includes: 1) Control the length of silicon single crystal growth; 2) During the crystal pulling process, p-type impurity boron is gradually added to offset the increasing concentration of n-type impurities; 3) By co-doping n-type dopants arsenic and antimony, the high volatility of impurities arsenic and antimony is used to adjust the doping concentration of the total n-dopant.

[0008] Deficiencies of existing technology: 1) Method 1) Reduce productivity; 2) Method 2) is at the expense of increasing the total impurity content in the silicon single crystal. If the total impurity content is high, the minority carrier lifetime of the silicon single crystal will be reduced, and if the minority carrier lifetime is low, the photoelectric conversion efficiency of the photovoltaic cell will be low; 3) Method 3) The toxicity of impurity arsenic will cause serious environmental problems, and the high volatility and low segregation coefficient of antimony make it more difficult to control.

[0009] The existing technical measures for controlling the concave shape of the crystal growth interface are: 1) As the silicon single crystal rod grows, the heating power of the peripheral graphite heater is appropriately increased, the temperature of the liquid silicon at the edge is increased, the crystallization rate of the edge of the silicon single crystal rod is reduced, and the pit depth of the crystallization interface is controlled within the permitted range by gradually reducing the pulling speed; 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 crystal interface within a permissible range.

[0010] However, both of the above measures come at the expense of production efficiency and the maximum cross-sectional area of ​​the pulled silicon single crystal rod.

[0011] 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 contents of the present invention only provide background technology related to the present invention, and do not necessarily constitute prior art or known technology. Summary of the invention

[0012] 1. Nouns and terminology: For the convenience of description, this application document defines the following nouns and terms: 1) (Liquid Silicon) Pressing Angle: Observe an intersection point p of the convex ridge contour line of the inner wall (including the inner side wall and the bottom wall) of the quartz crucible and the xoz plane. The quartz crucible is rotated about its vertical symmetry axis from the 0 position by an arc Δθ, causing the intersection point p to move along the inner wall ridge on the xoz plane by a distance Δ l , then the angle α near point p is defined as the suppression angle:

[0013] where d is the distance from the z-axis of the crucible to point p.

[0014] 2) "Right-handed" and "left-handed" quartz crucibles: Put the four fingers of your right hand together, with the thumb pointing downwards towards the bottom of the crucible (-z direction). The rotation direction of the four fingers represents the rotation direction Ω of the crucible, which is the "right rotation" of the crucible. Similarly, put the four fingers of your left hand together, with the thumb pointing downwards towards the bottom of the crucible (-z direction). The rotation direction of the four fingers represents the rotation direction Ω of the crucible, which is the "left rotation" of the crucible.

[0015] 3) "Right-hand" and "left-hand" ridges: The ridge located on the inner side wall of the quartz crucible: put the four fingers of the right hand together, the thumb downward, pointing to the bottom of the crucible (-z direction), and the rotation direction Ω of the four fingers represents the rotation of the ridge obliquely downward, which is considered to be "right-handed" for the ridge; similarly, put the four fingers of the left hand together, the thumb downward, pointing to the bottom of the crucible (-z direction), and the rotation direction Ω of the four fingers represents the rotation of the ridge obliquely downward, which is considered to be "left-handed" for the ridge.

[0016] The convex ridge at the bottom of the quartz crucible: put the four fingers of the right hand together, the thumb downward, pointing to the bottom of the crucible (-z direction), and the rotation direction Ω of the four fingers represents the direction in which the convex ridge shrinks and rotates toward the crucible axis, which is considered "right-hand rotation" of the bottom convex ridge; similarly, put the four fingers of the left hand together, the thumb downward, pointing to the bottom of the crucible (-z direction), and the rotation direction Ω of the four fingers represents the direction in which the convex ridge shrinks and rotates toward the crucible axis, which is considered "left-hand rotation" of the bottom convex ridge.

[0017] 4) "Right-handed" and "left-handed" silicon single crystal rods: Put the four fingers of your right hand together, with the thumb pointing downward and pointing toward the bottom of the crucible (-z direction). The rotation direction of the four fingers represents the rotation direction of the silicon single crystal rod, which is the "right rotation" of the silicon single crystal rod. Similarly, put the four fingers of your left hand together, with the thumb pointing downward and pointing toward the bottom of the crucible (-z direction). The rotation direction of the four fingers represents the rotation direction of the silicon single crystal rod, which is the "left rotation" of the silicon single crystal rod.

[0018] 5) Liquid silicon "first boundary layer" and "first boundary outer layer" at the liquid silicon / crucible interface: The "first boundary layer" of liquid silicon is a thin layer of liquid silicon fluid that is close to the side surface of the crucible cavity and has a non-negligible viscous force. In this application document, the thickness of the first boundary layer is It is a function of the crucible wall position (such as liquid level height z), and has the following relationship:

[0019] in: : The first correlation coefficient, when calculating, you can try to take the value 5; : Viscosity coefficient of liquid silicon; : Characteristic length, which is related to the transverse diameter of the eddy current along the crucible wall moving direction of the liquid silicon close to the crucible. Half of its length can be taken as the characteristic length during calculation; : Liquid silicon density; : The thermal convection rise rate of liquid silicon in the outer layer of the first boundary of liquid silicon at the first ridge on the inner cavity side surface of the quartz crucible.

[0020] It can be obtained by simulating the flow field in liquid silicon through simulation software such as CG-sim and FEMAG, or by experiments. Here, the velocity of the corresponding area in the liquid silicon fluid is given as an example. Since the velocity in the existing liquid silicon fluid can be obtained by simulation, theoretical calculation and other methods, the method of obtaining it is not specifically limited here.

[0021] The “first boundary outer layer” refers to a thin layer adjacent to the “first boundary layer” where the thermal convection rate of liquid silicon can reach more than 90% of the nearby maximum flow rate.

[0022] 6) Liquid silicon "second boundary layer" and "second boundary outer layer" at the liquid silicon / crucible interface: Similar to the "first boundary layer" of liquid silicon, the "second boundary layer" of liquid silicon is a thin layer of liquid silicon fluid that is close to the bottom surface of the crucible cavity and has a non-negligible viscous force. In this application document, the thickness of the second boundary layer is is a function of the crucible wall position (e.g., distance r from the axis), and has the following relationship:

[0023] in: : The second correlation coefficient, when calculating, you can try to take the value 5; : Viscosity coefficient of liquid silicon; : Characteristic length, which is related to the transverse diameter of the eddy current along the crucible wall moving direction of the liquid silicon close to the crucible. Half of its length can be taken as the characteristic length during calculation; : Liquid silicon density; : Convection velocity of liquid silicon in the outer layer of the second boundary of liquid silicon at the second convex ridge; It can be obtained by simulating the flow field in liquid silicon through simulation software such as CG-sim and FEIMAG, or by experiments. Here, the velocity of the corresponding area in the liquid silicon fluid is given as an example. Since the velocity in the existing liquid silicon fluid can be obtained by simulation, theoretical calculation and other methods, the method of obtaining it is not specifically limited here.

[0024] The “second boundary outer layer” refers to a thin layer adjacent to the “second boundary layer” where the thermal convection rate of liquid silicon can reach more than 90% of the nearby maximum flow rate.

[0025] The 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. , the excess oxygen impurity concentration at the crucible wall is , starting from the crucible wall, to the excess oxygen impurity concentration in the liquid silicon Down to 0.37 It turns out that the boundary layer thicknesses of the two definitions are comparable.

[0026] 7) "Third boundary layer" and "third boundary outer layer": The "third boundary layer" is the liquid silicon / silicon single crystal boundary layer, which refers to a thin layer of liquid silicon adjacent to the silicon single crystal. The most important feature of this thin layer is that there is a difference in 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 liquid silicon inside the crucible For impurities with a silicon solid-liquid segregation coefficient less than 1, such as phosphorus, arsenic, and antimony, Is a positive value. For impurities with a silicon solid-liquid segregation coefficient greater than 1, such as oxygen, is a negative value. The excess impurity concentration close to the crystalline silicon crystal interface is .

[0027] The definition is from the solid-liquid interface of crystalline silicon to the excess impurity concentration in liquid silicon. Down to 0.37 The last thin layer is the third boundary layer.

[0028] Thickness of the third boundary layer It can be calculated by the following formula:

[0029] in: : Correlation coefficient, for example, for the impurity antimony, You can choose 1.61; D: diffusion coefficient of the impurity in liquid silicon; : kinematic viscosity coefficient of liquid silicon; : The relative movement rate of liquid silicon in the "third boundary outer layer".

[0030] It can be obtained by simulating the flow field in liquid silicon through simulation software such as CG-sim and FEIMAG, or by experiments. Here, the velocity of the corresponding area in the liquid silicon fluid is given as an example. Since the velocity in the existing liquid silicon fluid can be obtained by simulation, theoretical calculation and other methods, the method of obtaining it is not specifically limited here.

[0031] The "third outer boundary layer" refers to a liquid silicon layer adjacent to the third boundary layer, and the third outer boundary layer has the highest liquid silicon flow rate in the vicinity.

[0032] 8) Equilibrium segregation coefficient and effective fractionation coefficient : The equilibrium segregation coefficient in this application document 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. In the crystal growth process, there is the following relationship:

[0033] in: : effective segregation coefficient; : equilibrium segregation coefficient; D : is the equivalent diffusion coefficient of the impurity in liquid silicon; : Growth rate of silicon single crystal in z direction (pulling speed); : Thickness of the third boundary layer.

[0034] 9) Front angle β (of ridge): Take the cross section of the ridge perpendicular to the length direction of the ridge, and 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 ridge).

[0035] 10) Back angle γ of (convex ridge): Take the cross section of the ridge perpendicular to the length direction of the ridge, and the angle between the line that deviates from the direction of movement of the ridge and the line segment between the two end points of its bottom surface is defined as the back angle γ (of the ridge).

[0036] 2. Purpose and content of the invention: The present invention has at least one of the following three purposes: first, to control the oxygen content and its longitudinal distribution in a CZ silicon single crystal; second, to increase the effective segregation coefficient when pulling an n-type conductive silicon single crystal. , making it closer to 1, so as to reduce the axial impurity distribution gradient of the n-type silicon single crystal; thirdly, to improve the flatness of the crystal plane of the silicon single crystal rod.

[0037] The content of the present invention includes: In a first aspect, the present invention provides a quartz crucible for pulling silicon single crystals, wherein the inner cavity of the crucible is quasi-circular in cross section in the xy plane, and one or more first convex edges protruding relative to the inner cavity side surface of the quartz crucible are arranged around the z-axis, wherein the rotation direction of the first convex edge is opposite to the rotation direction of the quartz crucible, and the first convex edge has a first convex edge pressing angle , ; The height of the first ridge The first boundary layer of liquid silicon larger than the inner surface of the quartz crucible The thickness of the first convex ridge outline protruding from the inner cavity side surface of the quartz crucible is observed, and an intersection point p with the xoz plane is observed. The quartz crucible is rotated about its vertical symmetry axis by an arc Δθ from the 0 position, causing the intersection point p to move a distance Δl along the first convex ridge on the xoz plane. Then the angle α near the point p is defined as the pressing angle:

[0038] Where d is the distance from the z axis to the intersection point p.

[0039] The height of the first ridge .

[0040] Alternatively, the height of the first ridge (Optional 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 27mm, 30mm, etc.).

[0041] Alternatively, the height of the first ridge (5mm, 5mm, 6mm, 7mm, 8mm, etc. are optional).

[0042] Alternatively, the height of the first ridge .

[0043] Alternatively, the first ridge has a first ridge pressing angle for (Optional are 46°, 49°, 52°, 55°, 58°, 61°, 64°, 67°, 70°, 75°, 80°, 85°, etc.).

[0044] Alternatively, the first ridge has a first ridge pressing angle for (Optional are 10°, 11°, 16°, 21°, 26°, etc.).

[0045] Alternatively, the first ridge has a first ridge pressing angle for (Optional are 30°, 31°, 36°, 40°, 44°, 45°, etc.).

[0046] Furthermore, the first convex edge pressing angle The angular velocity of the quartz crucible , crucible radius R, the thermal convection rise rate of the liquid silicon in the outer layer of the first boundary of the liquid silicon at the first ridge on the inner surface of the quartz crucible The following relationship exists:

[0047] in: :First convex edge pressing angle Correlation coefficient, ; : angular velocity of the quartz crucible; R: crucible radius; : The thermal convection rise rate of the liquid silicon in the outer layer of the first boundary of the liquid silicon when there is no convex ridge at the first convex ridge on the inner cavity side surface of the quartz crucible; Preferably, the cross section of the first ridge is a sawtooth asymmetric cross section, and the front angle of the first ridge is , 75°≤ ≤95° (optional: 75°, 77°, 82°, 85°, 87°, 89°, 91°, 93°, 95°, etc.); the first convex edge back angle is , 5°≤ <75° (optional: 5°, 9°, 11°, 24°, 33°, 43°, 55°, 62°, 68°, 71°, 74°, etc.); Optionally, the first ridges are arranged in a rotation manner on the inner cavity side wall of the quartz crucible, and the distance s between two adjacent first ridges is, (Optional: 21mm, 27mm, 33mm, 36mm, 38mm, 40mm, 49mm, 50mm, etc.).

[0048] Optionally, the first ridges are arranged in a rotation manner on the inner cavity side wall of the quartz crucible, and the distance s between two adjacent first ridges is, (Optional: 51mm, 54mm, 62mm, 70mm, 78mm, 90mm, 110mm, 140mm, 170mm, 200mm, etc.).

[0049] In a second aspect, the present invention provides a second quartz crucible for pulling silicon single crystals, wherein 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-rotational curved surface, and the bottom surface of the inner cavity is provided with one or more second convex ridges protruding relative to the bottom surface of the inner cavity of the quartz crucible, the second convex ridges are arranged to rotate around the z-axis, the rotation direction of the second convex ridges is opposite to the rotation direction of the quartz crucible, and the second convex ridges have a second convex ridge pressing angle , the second convex edge pressing angle It gradually decreases with the increase of the distance r from the z-axis, and the range of change is 2°< <78° (optionally 3°, 5°, 9°, 11°, 24°, 33°, 43°, 55°, 62°, 68°, 71°, 74°, 77°, etc.). Observe an intersection point p of the second convex ridge contour line protruding from the bottom surface of the inner cavity of the quartz crucible and the xoz plane. The quartz crucible rotates around its vertical symmetry axis by an arc Δθ from the 0 position, causing the intersection point p to move a distance Δl along the second convex ridge on the xoz plane. The angle α near point p is defined as the pressing angle:

[0050] Where d is the distance from the z axis to the intersection point p.

[0051] Furthermore, 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 at the bottom of the inner cavity of the quartz crucible.

[0052] Preferably, the height of the second convex ridge is , 5mm≤ <9mm (optional: 5mm, 6mm, 8mm, etc.); Alternatively, the height of the second convex ridge is , 9mm≤ ; Alternatively, the height of the second convex ridge 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. (11mm, 13mm, 15mm, 17mm, 19mm, etc. are available); Preferably, the cross section of the second convex edge is a sawtooth asymmetric cross section, and the front angle of the second convex edge is , 75°≤ ≤95° (optional: 75°, 77°, 82°, 85°, 87°, 89°, 91°, 93°, 95°, etc.), the back angle of the second convex edge , 5°≤ <75° (optional: 5°, 9°, 11°, 24°, 33°, 43°, 55°, 62°, 68°, 71°, 74°, etc.); Furthermore, the second ridge pressing angle of the second ridge near the side wall end of the quartz crucible is The second liquid silicon pressing angle is smaller than the second convex edge near the z-axis end. .

[0053] In a third aspect, the present invention provides a third quartz crucible for Czochralski silicon single crystals, whose inner cavity in the xy plane cross section is quasi-circular, the bottom surface of the inner cavity of the quartz crucible is a quasi-rotational curved surface, one or more first ridges protruding relative to the inner cavity side surface of the quartz crucible are arranged around the z-axis on the inner cavity side surface of the quartz crucible; and one or more second ridges protruding relative to the inner cavity bottom surface of the quartz crucible are arranged on the inner cavity bottom surface of the quartz crucible. It can be understood that the third quartz crucible for Czochralski silicon single crystals has the relevant designs and effects of the first and second quartz crucibles for Czochralski silicon single crystals, and can have a better effect of synergy.

[0054] In a fourth aspect, the present invention provides a method for growing a silicon single crystal ingot by a 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 having a right-handed first ridge, the crucible rotates in a left-handed direction; for the quartz crucible having a left-handed first ridge, the crucible rotates in a right-handed direction.

[0055] Furthermore, the angular velocity ω of the rotation of the quartz crucible is proportional to the first ridge pressing angle of the first ridge of the quartz crucible. , crucible radius R, the thermal convection rise rate of the first boundary outer layer of liquid silicon at the first ridge on the inner cavity surface of the quartz crucible There are the following relationships between them:

[0056] During the drawing process, as the liquid silicon level decreases, Reduce the angular velocity of the quartz crucible Decreasing.

[0057] Furthermore, the decreasing range of the product of the angular velocity ω of the quartz crucible and the crucible radius R is: when When, 400mm / sec>ωR>35mm / sec; when When, 140mm / sec>ωR>25mm / sec; when When, 100mm / sec>ωR>17mm / sec.

[0058] Furthermore, in accordance with the product of the angular velocity ω of the quartz crucible and the radius R of the crucible, the crystal rotation range is 0 to 4 revolutions, which is opposite to the rotation direction of the crucible.

[0059] Based on the correlation between the angular velocity ω of the quartz crucible rotation and the first ridge suppression angle of the first ridge of the quartz crucible, the crucible radius R, and the rising rate of the outer layer heat convection of the first boundary of liquid silicon at the first ridge on the inner cavity side surface of the quartz crucible, in the silicon single crystal preparation method, the equivalent angular velocity ω of the crucible rotation, which is closely related to the formation of the suppressed liquid silicon flow, is used as an important adjustment parameter in the control method, which can simplify the process control process and make it easier to achieve the ideal control effect.

[0060] Furthermore, in conjunction with the suppression and restriction of the thermal convection of liquid silicon by the first convex ridge, the thermal convection of liquid silicon is no longer suppressed by the inertial centrifugal force of the crystal rotation. Therefore, the rotation speed of the crystal rotation is set to 0-4 rpm, which is much lower than 8-12 rpm in the prior art. According to the relationship between the effective segregation coefficient and the equilibrium segregation coefficient:

[0061] The beneficial effect of the lower crystal rotation rate is that the effective diffusion coefficient D is reduced, and the movement speed of the liquid silicon outside the third boundary relative to the silicon single crystal is reduced. reduce, Thickening.

[0062] The solid-liquid equilibrium segregation coefficient of the known impurity oxygen , is greater than 1, so, The result of thickening is that the solid-liquid effective segregation coefficient of impurity oxygen Decreases and approaches 1. The decrease in the effective segregation coefficient reduces the impurity oxygen in the silicon single crystal; On the other hand, the solid-liquid equilibrium segregation coefficient of n-type impurities in n-type silicon single crystal is is less than 1, so The result of the thickening is that the solid-liquid effective segregation coefficient of n-type impurities Increases and approaches 1. The increase of the effective segregation coefficient improves the doping efficiency of the head of the n-type silicon single crystal and makes the doping concentration of the whole single crystal uniform.

[0063] In a fifth aspect, the present invention provides another method for growing a silicon single crystal ingot by a Czochralski method, using the quartz crucible provided in the second aspect. During the crystal growth process, the quartz crucible rotates around the central symmetry axis z. For the quartz crucible having a right-handed second ridge, the crucible rotates in a left-handed direction; for the quartz crucible having a left-handed second ridge, the crucible rotates in a right-handed direction.

[0064] Furthermore, in the process of pulling a silicon single crystal, as the liquid silicon level decreases, the convection intensity of the liquid silicon decreases, and accordingly, the crucible rotation speed decreases.

[0065] Furthermore, the second ridge restrains and constrains the thermal convection of liquid silicon, replaces or partially replaces the inertial centrifugal force of crystal rotation to suppress the thermal convection of liquid silicon and homogenize the liquid silicon, which is beneficial to reduce the rotation speed of crystal rotation and obtain the beneficial effect brought by the aforementioned reduction in crystal rotation.

[0066] Specifically, the first purpose of the present invention is to control the oxygen content and its longitudinal distribution of the CZ silicon single crystal.

[0067] The oxygen content of silicon single crystal is controlled by, firstly, increasing the thickness of the first boundary layer to reduce the oxygen impurity concentration gradient in the boundary layer; secondly, suppressing the intensity of thermal convection to reduce the effective diffusion coefficient of oxygen impurities to liquid silicon; thirdly, increasing the thickness of the third boundary layer to suppress the flow rate of liquid silicon outside the third boundary and reduce the solid-liquid segregation coefficient of impure oxygen.

[0068] Control the longitudinal distribution of oxygen content in silicon single crystal by changing the crucible rotation. The specific instructions are as follows: Because the oxygen in liquid silicon mainly comes from the quartz crucible, especially the high-temperature area of ​​the crucible closest to the heater, the thermal convection buoyancy of liquid silicon caused by high temperature is several to dozens of times greater than other forces (such as the inertial centrifugal force generated by crucible rotation and crystal rotation, the surface tension of liquid silicon, the blowing shear force of argon gas, and the advection force of liquid silicon caused by crystallization, etc.). Therefore, in the absence of magnetic field participation, the existing technology is relatively insufficient in the balance and constraint of the thermal convection buoyancy of various forces. The eddy currents generated by the thermal convection liquid silicon in the liquid silicon / crucible boundary layer excessively scour the quartz crucible wall, bringing a large number of oxygen ions into the liquid silicon and into the crystal, increasing the oxygen content of the silicon single crystal. The thermal convection buoyancy of liquid silicon is proportional to the height of the liquid surface in the liquid silicon heating section, so the oxygen content at the head of the silicon single crystal is higher.

[0069] One of the ways to control the oxygen content and longitudinal distribution of the CZ silicon single crystal in the present invention is that the first ridge located on the inner side wall of the quartz crucible is arranged to rotate around the z-axis, and the first ridge has a liquid silicon first ridge pressing angle , 10° ≤85°; the height of the first ridge is greater than the thickness of the first boundary layer of liquid silicon on the side surface of the inner cavity of the crucible .

[0070] The first convex edge arranged in rotation cooperates with the rotation direction of the quartz crucible (the crucible with the right-handed first convex edge rotates to the left; the crucible with the left-handed first convex edge rotates to the right), thereby generating a reverse suppression force on the natural thermal convection of the outer layer of the first boundary of liquid silicon, balancing and restraining the natural thermal convection generated by buoyancy, reducing the intensity of the eddy current, alleviating the scouring of the quartz crucible wall by the liquid silicon eddy current, and increasing 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 ridge is greater than the first boundary layer thickness of the liquid silicon on the side surface of the inner cavity of the crucible , it can cross the first boundary layer, forming a more effective suppression of the high-speed liquid silicon thermal convection outside the first boundary layer, thereby more effectively reducing the total amount of impurity oxygen entering the liquid silicon from the quartz crucible wall.

[0071] Understandably, the first convex edge pressing angle With a certain angle, the first convex ridge can suppress the heat convection of liquid silicon in the outer layer of the first boundary. Due to the optimal first convex ridge pressing angle corresponding to different technical states of the quartz crucible and crystal pulling process parameters, The range can be different, so the following different pressing angle ranges are optional.

[0072] Specifically, by , first convex edge pressing angle When there is no ridge at the first ridge on the inner cavity side surface of the quartz crucible, the liquid silicon heat convection rise rate of the first boundary outer layer of the liquid silicon (the natural heat convection rise rate of the boundary outer layer) ), while the natural heat convection rise rate of the outer layer of the boundary of liquid silicon at different depths in the quartz crucible is It can be different. You can choose a larger one for higher places. , for example 45°< ≤85°; You can choose a smaller one for the lower part , for example 10°< ≤30°.

[0073] Furthermore, due to the suppression angle Together with the crucible rotation speed ωR, the thermal convection of liquid silicon is suppressed. At a certain time, Therefore, when some embodiments require a higher crucible rotation (for example, when the impurities in the liquid silicon need to be more evenly distributed), a smaller first convex edge pressing angle may be selected. , for example, choose 10°< ≤30°; Similarly, when some embodiments require a lower crucible rotation (for example, when pursuing a more stable flow field and thermal field distribution), a larger first convex edge pressing angle can be selected. , for example, choose 45°< ≤85°.

[0074] The height of the first ridge Optional . Greater than the first boundary layer thickness , by formula It can be seen that is a function of the position of the inner wall of the crucible. The first boundary layer thickness at different positions of the crucible is different, therefore, different first ridge height Range combination can get better comprehensive effect. The height of the first ridge , are optional first boundary layer thicknesses at different locations from the crucible The height of the first ridge is different range. Understandably, the designer can either Different first ridges can be designed, and different sections of the same first ridge can be designed to have different heights. It can be selected within the different height ranges.

[0075] Select different pressing angles of the first ridge , and different first ridge heights , providing different suppression intensities for the thermal convection of liquid silicon to achieve a better balance and constrain the effect of natural thermal convection generated by buoyancy, reducing the intensity of thermal convection of liquid silicon, reducing the scouring of liquid silicon on the wall of the quartz crucible, and increasing the thickness of the first boundary layer, so as to reduce the total amount of impurity oxygen entering the liquid silicon from the wall of the quartz crucible at all stages of crystal pulling.

[0076] The design of different angle ranges and height ranges of the first convex ridge can simplify the control process and more easily achieve the desired control effect. You can choose a larger value in the range with better effect, such as 45°< ≤85° range, select 70°, and only need to slightly change the crucible rotation at different times of crystal pulling to achieve the required different pressing effects; similarly, when a higher speed crucible rotation is required, for example, to meet the centripetal drive requirements of the second convex ridge at the bottom of the crucible, the first convex ridge pressing angle You can choose a smaller value within the range with better results, such as 10°< Select 26° in the range of ≤30°. Similarly, different required pressing effects can be achieved by slightly changing the crucible rotation at different times of crystal pulling.

[0077] The angular velocity ω of the quartz crucible and the rising rate of the heat convection of the first boundary outer layer of the liquid silicon at the first ridge on the inner cavity side surface of the quartz crucible are Based on the correlation between the two, in the silicon single crystal preparation method, the crucible rotation equivalent angular velocity ω, 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 make it easier to achieve the ideal control effect.

[0078] In a more preferred solution, the cross-section of the first ridge is a sawtooth-shaped asymmetric cross-section, wherein the front angle of the "sawtooth" first ridge is relatively steep and the rear angle of the first ridge is relatively gentle. The beneficial effect of such an arrangement is that it is beneficial to form a relatively gentle laminar vortex between the first ridges, preventing the formation of violent turbulent vortexes that cause excessive impact and corrosion on the wall of the quartz crucible; it is beneficial to minimize the contact area between the liquid silicon and the crucible, and reduce the path for impurity oxygen to enter the liquid silicon.

[0079] In a preferred solution, the distance s between the two first ridges is In another preferred embodiment, the distance s between the two first ridges is, , all to accommodate crucibles of different sizes and first ridges of different heights In order to meet the design requirements, under the premise of satisfying the need for suppressing the thermal convection of liquid silicon, the inner surface area of ​​the crucible increased by the first convex ridge is minimized as much as possible to reduce the adverse effect of the increase in the contact area between the crucible and the liquid silicon on reducing the oxygen content.

[0080] In addition to the above points, since the first convex ridge enhances the flow effect of the liquid silicon surface rotating with the crucible, the path and time of the liquid silicon flowing from the crucible wall to the silicon crystal are prolonged, so that more oxygen dissolved in the liquid silicon evaporates into the argon atmosphere in the furnace in the form of SiO2 vapor, which is also beneficial to reduce the oxygen content of the silicon single crystal.

[0081] The second method of controlling the oxygen content and longitudinal distribution of the CZ silicon single crystal of the present invention is to set one or more second convex edges at the bottom of the inner side of the quartz crucible, which are arranged to rotate around the z-axis, and the rotation direction of the second convex edges is opposite to the rotation direction of the quartz crucible, and the second convex edges are pressed at an angle of It gradually decreases with the increase of distance from the z-axis, and the range of change is 2°< <78°, The range of angle variation depends on the type and number of spirals.

[0082] The second convex ridge cooperates with the rotation of the quartz crucible (the crucible with right-handed convex ridge rotates to the left; the crucible with left-handed convex ridge rotates to the right), and the second convex ridge suppresses the angle A centripetal compressed liquid silicon flow is generated at the bottom of the crucible in the opposite direction to the heat convection of the liquid silicon, balancing and restraining the heat convection generated by the buoyancy of the liquid silicon, thereby reducing the intensity of the liquid silicon scouring the quartz crucible wall and increasing the thickness of the first boundary layer. , so as to reduce the total amount of impurity oxygen entering the liquid silicon from the quartz crucible wall.

[0083] Second convex edge pressing angle The gradual angle and spiral setting are intended to improve the pressing efficiency of liquid silicon.

[0084] Height of the second ridge The beneficial effects of the setting of the sawtooth asymmetric cross section are the same as those of the first convex ridge.

[0085] The third way of controlling the oxygen content and its longitudinal distribution of the CZ silicon single crystal in the present invention is that it is known that under the action of simple crystal rotation, the oxygen impurity content in the silicon single crystal is proportional to the rotation speed of the crystal rotation. The reasons are: 1) crystal rotation transports more impurity oxygen to the crystal interface; 2) crystal rotation makes the effective segregation coefficient of oxygen Closer to the equilibrium segregation coefficient of oxygen , and the equilibrium fractionation coefficient of oxygen Therefore, more impurity oxygen will be condensed into the silicon single crystal. In the present invention, whether it is the first approach or the second approach, the first convex edge pressing angle and the crucible rotation ωR cooperate to replace the function of part of the crystal rotation, thereby greatly reducing the crystal rotation to zero, which is beneficial to reduce the oxygen impurity content in the silicon single crystal and make it uniform.

[0086] The second object of the present invention is to improve the effective segregation coefficient of n-type impurities by: The impurity concentration on one side of the crystal interface of the silicon single crystal rod is determined by the liquid silicon doping concentration. and the effective segregation coefficient of impurities between crystal and liquid silicon The effective fractionation coefficient and equilibrium segregation coefficient There are the following relationships:

[0087] in is the effective segregation coefficient, is the equilibrium segregation coefficient, D is the equivalent diffusion coefficient of the n-type impurity in liquid silicon, is the z-direction growth rate (pulling speed) of silicon single crystal, is the silicon single crystal / liquid silicon interface, the thickness of the third boundary layer of liquid silicon, It can be determined by the following empirical formula:

[0088] in Correlation coefficient, is the kinematic viscosity coefficient of liquid silicon It is the movement speed of the liquid silicon outside the third boundary relative to the silicon single crystal.

[0089] From the above two equations, we can get: When the outer layer of liquid silicon at the third boundary moves at a speed relative to the crystal When it is low enough, the effective segregation coefficient It will be closer to 1, closer to the segregation coefficient of 1 The longitudinal distribution concentration gradient of the n-type impurities in the silicon single crystal ingot can be reduced to obtain a longer and heavier single n-type silicon single crystal rod.

[0090] The strong thermal convection of liquid silicon in the prior art makes the flow rate of the outer layer of the third boundary In order to resist the increase of oxygen content in silicon single crystal caused by thermal convection, a higher crystal rotation is introduced. The inertial centrifugal force generated by the crystal rotation will also increase the flow velocity of the outer layer of the third boundary. , The increase in the thickness of the liquid silicon boundary layer ( )reduce, ( ) decreases, the effective segregation coefficient of the dopant For n-type dopants such as phosphorus and antimony, the effective segregation coefficient It decreases in the direction away from 1, which increases the longitudinal impurity concentration gradient of the silicon single crystal ingot, thereby limiting the pulling length of the silicon single crystal ingot and reducing productivity.

[0091] The present invention uses the vortex effect of the second convex edge at the bottom of the crucible to generate 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 the vortex nozzle. The role of the liquid flow in the process can replace the role of crystal rotation, but it does not directly impact the liquid silicon near the crystallization interface, causing the boundary outer layer flow velocity to increase. Maintaining a low level is beneficial to the liquid silicon boundary layer thickness ( )Increase, ( ) increases, the effective segregation coefficient of the dopant increases Combined with the vortex effect of the second convex ridge to suppress the thermal convection intensity of liquid silicon, it is possible to reduce the oxygen content of the silicon single crystal while increasing the effective segregation coefficient. (closer to 1), achieving the beneficial effect of reducing the longitudinal impurity concentration gradient of the silicon single crystal ingot.

[0092] The third object of the present invention is to improve the flatness of the crystal plane of the silicon single crystal rod, which is achieved as follows: The growth of silicon single crystals by the Czochralski method is a controlled crystal growth process. A seed crystal is introduced into liquid silicon, and the crystal grows in a specific crystal direction through the continuous transfer of atoms from the liquid phase to the solid phase at the solid-liquid interface. The growth conditions at the solidification front of the silicon single crystal can be described by the following formula:

[0093] Where: n: the vector of the silicon single crystal solidification front perpendicular to the solid-liquid interface (positive downward); : Growth rate of silicon single crystal (along the direction of vector n); : Density of silicon single crystal; L: latent heat of crystallization of silicon; : Thermal conductivity of silicon crystal; : Thermal conductivity of liquid silicon; : Temperature gradient along the vector n direction on the silicon crystal side of the crystallization interface; : Temperature gradient along the vector n direction on the liquid silicon side of the crystallization interface.

[0094] After the silicon single crystal is pulled into the equal diameter stage, as the silicon single crystal rod grows, the heat dissipation path of the crystal interface continues to lengthen, the thermal resistance increases, and the temperature gradient on the silicon single crystal side of the crystal interface The thermal resistance of the heat dissipation path in the center of the silicon single crystal ingot is greater. The decrease is also greater, and the crystal growth rate in the center of the crystallization interface is lower than that in the edge part, making the crystallization interface concave.

[0095] In order to control the degree of concave of the silicon single crystal crystal interface, one of the measures is to increase the temperature of the liquid silicon around the silicon single crystal ingot, increase The second measure is to reduce the crystal rotation, in order to weaken the high-temperature liquid silicon flow to the center of the crystal interface of the silicon single crystal ingot caused by the forced flow of inertial centrifugal force, by reducing the crystallization rate near the center of the crystal interface. , to achieve the purpose of reducing the pit depth of the silicon single crystal ingot. The shortcoming of this technical measure is that there are other effects in the process that need to be achieved with the help of the inertial centrifugal force of crystal rotation, such as counteracting buoyancy heat convection, prolonging the volatilization time of silicon oxide on the surface of liquid silicon, and reducing the oxygen content of silicon single crystal ingot. The second measure involves more technology.

[0096] The technology of the present invention provides a method for solving this problem. With the help of the centripetal vortex effect of the second 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 trumpet-shaped liquid flow generated upward by the vortex nozzle. The influence on the flow direction of liquid silicon is similar to 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, and the power of crystal rotation is on the surface of liquid silicon. The present invention generates a centripetal and upward liquid silicon vortex from the bottom of the liquid silicon. The rising path is in an upward trumpet shape, 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 to the vicinity of the crystallization interface. Therefore, the temperature gradient of the liquid silicon near the crystallization interface can be reduced. , the purpose of controlling the depth of the pits on the crystal plane can also slow down the pulling speed compared with the existing technology The degree of reduction can also be achieved by reducing the disturbance to the central part of the crystal interface, so as to maintain a higher impurity concentration near the crystal interface and increase the effective segregation coefficient of n-type impurities. , reduce the effective segregation coefficient of impurity oxygen As mentioned above, this is particularly beneficial for reducing the oxygen impurity content and pulling n-type silicon single crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0098] Figure 1 This is a schematic diagram of the longitudinal cross-section structure of a quartz crucible according to Example 1 of the present invention.

[0099] Figure 2 This is a schematic diagram of the longitudinal cross-section structure of a quartz crucible according to Example 2 of the present invention.

[0100] Figure 3 Schematic diagram of a top view of the bottom structure of a quartz crucible according to Example 3 of the present invention.

[0101] Figure 4 Schematic diagram of the longitudinal section structure of the quartz crucible of Example 4 of the present invention.

[0102] Description of reference numerals: 1-quartz crucible; 11-first convex edge; α 1 - first ridge pressing angle; β 1 - the first convex edge rake angle; γ 1 - first convex edge back angle; h 1 - first ridge height; 12 - second ridge; α 2 -Second ridge pressing angle; β 2 - the second convex edge rake angle; γ 2 -Second convex edge back angle; h 2 - Height of the second ridge; 2 - Heater; 3 - Crucible rotation axis z-axis. DETAILED DESCRIPTION

[0103] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0104] 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 invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0105] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0106] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0107] Example 1 The embodiment of the present invention provides a quartz crucible 1 for growing silicon single crystals by a Czochralski method, which is heated by a heater 2, and whose inner cavity in the xy plane cross section is quasi-circular. The diameter of the quartz crucible 1 is 840 mm, and the height is 650 mm, wherein the cylindrical part is 450 mm high, and the bottom arc part is 200 mm high. On the inner cavity side wall surface of the quartz crucible 1, 18 first convex ridges 11 protruding relative to the inner cavity side wall surface of the quartz crucible 1 are arranged in a rotational manner around the crucible rotation axis z axis 3, and the first convex ridges 11 are right-handed, which is opposite to the rotation direction of the quartz crucible 1, and the first convex ridges 11 have a first convex ridge pressing angle α 1 is 70°, the first boundary layer thickness of liquid silicon on the inner surface of the quartz crucible is δ 1 Consider 6mm; the height of the first ridge h 1 The cross section of the first ridge 11 is a serrated asymmetric cross section, and the first ridge front angle β 1 is 90°; its first convex edge back angle γ 1 The vertical distance between the two first ridges 11 is s=118 mm. The above crucible is used to grow silicon single crystal by Czochralski method, and the crucible rotation angular velocity is given by the formula According to the adjustment principle, the crucible rotation speed in this embodiment is 1.5 revolutions per minute, and the crucible rotation speed at the end of crystal pulling is 0.5 revolutions per minute.

[0108] The beneficial effects of this embodiment compared with the prior art are: 1) In this embodiment, the first convex ridge 11 suppresses the thermal convection of liquid silicon, thereby reducing the impact corrosion of liquid silicon on the quartz crucible 1 and increasing the first boundary layer δ 1 The thickness of the silicon single crystal is reduced by 20% compared with the existing Czochralski method without a magnetic field. 2) This embodiment can simply adjust the angular velocity of the crucible to adjust the oxygen impurity concentration of the silicon single crystal so that the oxygen impurity concentration at the head and tail of the silicon single crystal ingot is within the required range; 3) With a lower crucible rotation, the thermal convection of liquid silicon is restrained, and the flow field and thermal field in the crucible are stable.

[0109] 4) Compared with the prior art, this embodiment does not rely on the shear force of the argon gas flow to suppress the thermal convection intensity of the liquid silicon, which is conducive to maintaining the stability of the silicon liquid surface temperature and its distribution, and can reduce the consumption of argon gas and reduce costs; 5) Compared with the prior art, this embodiment does not rely on the inertial centrifugal force generated by crystal rotation to suppress the thermal convection intensity of liquid silicon. When pulling n-conductive type silicon single crystals, it is beneficial to maintain the concentration of n-type impurities near the crystal interface at a high level and improve the effective segregation coefficient of n-type impurities. , improve the uniformity of doping and production efficiency; at the same time reduce the effective segregation coefficient of impurity oxygen , reducing the impurity oxygen content in silicon single crystals.

[0110] Example 2 Embodiment 2 of the present invention provides a quartz crucible 1 for growing a silicon single crystal by a Czochralski method which is substantially the same as Embodiment 1. On the inner cavity side wall surface of the quartz crucible 1, eight first ridges 11 protruding relative to the inner cavity side wall surface of the quartz crucible 1 are arranged in a rotational manner around the crucible rotation axis z axis 3. The first ridges 11 have a right-handed rotation direction, which is opposite to the rotation direction of the quartz crucible 1. The first ridges 11 have a first ridge pressing angle α. 1 is 26°, according to the first boundary layer thickness δ of liquid silicon on the inner surface of the quartz crucible 1 The height h of the first ridge 11 is considered to be 6mm; 1 The cross section of the first ridge 11 is a sawtooth asymmetric cross section, and the first ridge front angle β 1 is 90°; its first convex edge back angle γ 1 The vertical spacing between the two first ridges 11 is s = 118mm, and the above crucible is used to grow a silicon single crystal by the Czochralski method, and the angular velocity of the crucible is given by the formula According to the adjustment principle, the angular velocity of the crucible in this embodiment is 2.5 rpm, and the angular velocity at the end of crystal pulling is 0.8 rpm.

[0111] Beneficial effects compared with Example 1: First, the first convex edge pressing angle α of this embodiment 1 Smaller, the advantage is that the surface area of ​​the inner wall of the crucible occupied is smaller, so the total surface area of ​​the crucible exposed in the liquid silicon is smaller, and less impurity oxygen enters the liquid silicon through this route; Second, the crucible rotation of this embodiment is higher than that of the embodiment 1, and is easily compatible with the structure of the embodiment 3 which requires a higher crucible rotation.

[0112] Example 3 like Figure 3 Shown and referenced Figure 2 The embodiment of the present invention provides a quartz crucible 1 for growing silicon single crystals by a Czochralski method, wherein the inner cavity of the quartz crucible 1 in the xy plane cross section is quasi-circular, the diameter of the quartz crucible 1 is 840 mm, the height is 650 mm, the cylindrical part is 450 mm high, the bottom arc part is 200 mm high, the bottom arc is 840 mm, and the transition arc is 140 mm. On the bottom surface of the inner cavity of the quartz crucible 1, three second convex ridges 12 protruding relative to the inner cavity surface of the quartz crucible 1 are evenly distributed symmetrically at the center, and the projection of the second convex ridge 12 on the xy plane is a part of the involute of the center of the three base circles on the crucible rotation axis z axis 3, and the three second convex ridges 12 are rotationally symmetrically arranged around the crucible rotation axis z axis 3, and the second convex ridge pressing angle α 2 , from outside to inside α 2It changes continuously from 10° to 22°, and the pressing angle near the axis is greater than the pressing angle near the side wall.

[0113] In this embodiment, the height h of the second convex ridge 12 is 2 The cross section of the second ridge 12 is a serrated asymmetric cross section, and the second ridge front angle β 2 is 90°, the back angle of the second convex edge is γ 2 The second convex edge 12 is right-handed.

[0114] In this embodiment, during the growth of silicon single crystal, the quartz crucible 1 rotates about the crucible rotation axis z-axis 3 which is the central symmetry axis, and the quartz crucible 1 having the right-handed second convex ridge 12 rotates in the left-handed direction.

[0115] Beneficial effects of this embodiment: 1) This embodiment uses the second convex ridge 12 to restrain the thermal convection of liquid silicon, thereby reducing the impact corrosion of liquid silicon on the quartz crucible 1 and reducing the oxygen impurity content in the silicon single crystal by 10%. 2) Compared with the prior art, this embodiment does not rely on the shear force of the argon gas flow to suppress the thermal convection intensity of liquid silicon, which is conducive to maintaining the stability of the silicon liquid surface temperature and its distribution, and can reduce the consumption of argon gas and reduce costs; 3) Compared with the prior art, this embodiment does not rely on the inertial centrifugal force generated by crystal rotation to suppress the thermal convection intensity of liquid silicon. When pulling a silicon single crystal of n-conductivity type, it is beneficial to keep the concentration of n-type impurities near the crystal interface stable at a high level, increase the solid-liquid effective segregation coefficient of impurity phosphorus from 0.35 to 0.4, improve the uniformity of doping, and improve production efficiency; at the same time, it can reduce the effective segregation coefficient of impurity oxygen , further reducing the impurity oxygen content in silicon single crystals.

[0116] 4) In this embodiment, on the one hand, the second ridge 12 will generate a centripetal forced liquid silicon flow pressure near the bottom of the quartz crucible 1, and the 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, the forced liquid silicon flow pressure, the vortex formed by it has the effect of pumping the lower temperature liquid silicon at the bottom of the quartz crucible 1 to the center of the silicon single crystal ingot, which can improve the flatness of the crystal plane of the silicon single crystal ingot, and has the beneficial effect of reducing the stress within the crystal and improving the uniformity of impurity distribution within the wafer.

[0117] Example 4 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 of Embodiment 1, except that the first ridge pressing angles α at the upper and lower portions of the first ridge 11 are 1With different pressing angles, the first convex pressing angle α 1 Angle α of the upper part 1 =80°, the lower half transitions to α 1 =20°. Its beneficial effect is that the quartz crucible 1 can be operated at substantially the same crucible rotation angular velocity ω from the beginning stage to the end stage of crystal pulling, which is conducive to the smooth operation of the program.

[0118] In summary, compared with the prior art technical solution of 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.

[0119] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A quartz crucible for pulling silicon single crystals, wherein the inner cavity of the crucible is quasi-circular in cross section in the xy plane, and one or more first convex edges protruding relative to the inner cavity side surface of the quartz crucible are arranged on the inner cavity side surface of the quartz crucible in a rotational manner around the z-axis, characterized in that: The rotation direction of the first ridge is opposite to that of the quartz crucible, and the first ridge has a first ridge pressing angle , ; The height of the first ridge Greater than the first boundary layer thickness of liquid silicon on the inner cavity side surface of the quartz crucible Observe an intersection point p of the first convex ridge contour line protruding from the inner cavity side surface of the quartz crucible and the xoz plane. The quartz crucible rotates from the 0 position by an arc Δθ around its vertical symmetry axis, causing the intersection point p to move a distance Δl along the first convex ridge on 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.

2. The quartz crucible according to claim 1, characterized in that: The height of the first ridge for .

3. The quartz crucible according to claim 2, characterized in that: The height of the first ridge for or .

4. The quartz crucible according to claim 1, characterized in that: The first ridge has a first ridge pressing angle for .

5. The quartz crucible according to claim 1, characterized in that: The first ridge has a first ridge pressing angle for or .

6. The quartz crucible according to claim 1, characterized in that: The first convex edge pressing angle The angular velocity of the quartz crucible , crucible radius R, the liquid silicon thermal convection rise rate of the liquid silicon first boundary outer layer at the first convex edge of the inner cavity side surface of the quartz crucible The following relationship exists: in: :First convex edge pressing angle Correlation coefficient, ; : angular velocity of the quartz crucible; R: crucible radius; : The thermal convection rise rate of liquid silicon in the outer layer of the first boundary of liquid silicon when there is no convex ridge at the first convex ridge on the inner cavity side surface of the quartz crucible.

7. 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 ridge is a sawtooth asymmetric cross section, and the front angle of the first ridge is , 75°≤ ≤95°; the first convex edge back angle is , 5°≤ <75°; 2) The first convex ridges are arranged in a rotation manner on the inner cavity side surface of the quartz crucible, and the distance s between two adjacent first convex ridges is, ; or, the first ridges arranged in rotation on the inner cavity side surface of the quartz crucible, the distance s between two adjacent first ridges, .

8. A quartz crucible for pulling silicon single crystals, wherein the inner cavity of the crucible in the xy plane cross section is quasi-circular, and the bottom surface of the inner cavity of the quartz crucible is a quasi-rotational curved surface, characterized in that: On the bottom surface of the inner cavity of the quartz crucible, one or more second ridges are provided which are raised relative to the bottom surface of the inner cavity of the quartz crucible. The second ridges are arranged to rotate around the z-axis. The rotation direction of the second ridges is opposite to that of the quartz crucible. The second ridges have a second ridge pressing angle , the second convex edge pressing angle It gradually decreases with the increase of the distance r from the z-axis, and the range of change is 2°< <78°, observe an intersection point p of the second convex ridge contour line protruding from the bottom surface of the inner cavity of the quartz crucible and the xoz plane, and the quartz crucible rotates from the 0 position by an arc Δθ around its vertical symmetry axis, causing the intersection point p to move a distance Δl along the second convex ridge on 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.

9. The quartz crucible according to claim 8, 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.

10. The quartz crucible according to claim 8, 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 second convex ridge 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. , 5mm≤ <9mm; or, the height of the second convex ridge 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. , 9mm≤ <11mm; or, the height of the second convex ridge 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 ridge is a sawtooth asymmetric cross section, and the front angle of the second convex ridge is , 75°≤ ≤95°; the back angle of the second convex edge , 5°≤ <75°; 3) The second ridge pressing angle of the second ridge near the side wall end of the quartz crucible The second ridge pressing angle is smaller than the second ridge near the z-axis end. .

11. A quartz crucible for pulling silicon single crystals, wherein the inner cavity of the quartz crucible in the xy plane cross section is quasi-circular, and the bottom surface of the inner cavity of the quartz crucible is a quasi-rotational curved surface, characterized in that: On the side surface of the inner cavity of the quartz crucible, one or more first ridges as described in any one of claims 1 to 7 are arranged to rotate around the z-axis and are protruding 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 8 to 10 are arranged to protrude relative to the bottom surface of the inner cavity of the quartz crucible.

12. A method for growing a silicon single crystal ingot by using a Czochralski method, characterized in that: Using the quartz crucible described in any one of claims 1 to 7, 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.

13. The method for growing a silicon single crystal ingot by using a Czochralski method according to claim 12, characterized in that: The angular velocity ω of the quartz crucible rotation and the first ridge pressing angle of the first ridge of the quartz crucible , crucible radius R, thermal convection rise rate of the first boundary outer layer of liquid silicon at the first ridge on the inner surface of the quartz crucible There are the following relationships between them: During the drawing process, as the liquid silicon level decreases, Reduce the angular velocity of the quartz crucible Decreasing.

14. The method for growing a silicon single crystal ingot by using a Czochralski method according to claim 13, 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 When, 400mm / sec>ωR>35mm / sec; when When, 140mm / sec>ωR>25mm / sec; when When, 100mm / sec>ωR>17mm / sec.

15. The method for growing a silicon single crystal ingot by using a Czochralski method according to claim 14, 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.

16. A method for growing a silicon single crystal ingot by using a Czochralski method, characterized in that: Using the quartz crucible described in any one of claims 8 to 11, 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.

17. The method for growing a silicon single crystal ingot by using a Czochralski method according to claim 16, characterized in that: During the pulling process, as the liquid silicon level decreases, the angular velocity of the quartz crucible Decreasing.

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