CN-121976283-A - Silicon single crystal pulling method for improving OISF defect and product thereof

CN121976283ACN 121976283 ACN121976283 ACN 121976283ACN-121976283-A

Abstract

The invention provides a silicon single crystal pulling method for improving OISF defects and a product thereof. The silicon single crystal pulling method comprises the following steps of pulling a silicon single crystal in a thermal field of a single crystal furnace, and in a constant diameter growth stage of the silicon single crystal, establishing a regulation and control relation among pulling speed, an axial temperature gradient of a growth interface and OISF defects by increasing the distance between a water cooling screen and the liquid level of a silicon melt in a set pulling speed range so as to enable the OISF defects to move towards the edge of a crystal bar. According to the invention, the regulation and control relation between the pulling speed, the axial temperature gradient of the growth interface and the OISF defect is established by increasing the distance between the water cooling screen and the liquid level of the silicon melt, so that the OISF defect moves towards the edge of the crystal rod, and the active inhibition and partition control of the OISF defect are realized on the premise of keeping the high pulling speed potential and obviously improving the unit yield, so that the proportion of the crystal rod with the existing harmful OISF defect is greatly reduced, and the production yield is obviously improved.

Inventors

ZHANG JUNKAI
PAN JUNMING
WANG LIN
WANG YONGQIAN
CHEN GANG

Assignees

浙江爱旭太阳能科技有限公司
珠海富山爱旭太阳能科技有限公司
山东爱旭太阳能科技有限公司
广东爱旭科技有限公司
天津爱旭太阳能科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260128

Claims (10)

1. A silicon single crystal pulling method for improving OISF defect, characterized by comprising the steps of: and in the equal diameter growth stage of the silicon single crystal, the regulation and control relation among the pulling speed, the axial temperature gradient of the growth interface and the OISF defect is established by increasing the distance between the water cooling screen and the liquid level of the silicon melt in the range of setting the pulling speed, so that the OISF defect moves towards the edge of the crystal bar.
2. The method for pulling a silicon single crystal according to claim 1, wherein the target constant diameter of the silicon single crystal is 250 to 310mm, and the set pulling rate is in the range of 80 to 120mm/h; and/or setting the pulling rate to gradually rise in the initial stage of the equal diameter and to remain unchanged in the middle stage of the equal diameter and to decrease in the final stage of the equal diameter in the equal diameter growth stage of the silicon single crystal; and/or setting the heating power to gradually decrease and then to remain unchanged at an initial stage of the isodiametric of the silicon single crystal.
3. The method for pulling a silicon single crystal according to claim 2, wherein the axial temperature gradient is decreased at the same portion in the radial direction of the crystal interface in the initial stage of the isodiametric dimension of the silicon single crystal.
4. The method of pulling a silicon single crystal according to claim 3, wherein the pulling rate V and the growth interface axial temperature gradient G are controlled so that V/G is not less than 0.12mm 2 /min.K at a position 3-5mm in the radial direction of the silicon single crystal from the center of the ingot to the edge of the ingot in the mid-and end-isodiametric stages of the silicon single crystal.
5. The method for pulling a silicon single crystal according to any one of claims 1 to 4, wherein the thermal field of the single crystal furnace comprises a furnace body, wherein a coaxially arranged crucible is arranged in the furnace body, and a supporting rod is connected below the crucible and used for supporting and driving the crucible to move; A heat preservation cylinder is arranged between the crucible and the furnace body, and comprises an upper heat preservation cylinder and a lower heat preservation cylinder which are sequentially arranged along the axial direction; the upper heat preservation cylinder is arranged on the periphery of the guide cylinder, the lower heat preservation cylinder is arranged on the periphery of the crucible, and a side heater is arranged between the lower heat preservation cylinder and the crucible; the water cooling screen is connected with a lifting mechanism, and the lifting mechanism is fixed on a furnace cover of the furnace body and used for driving the water cooling screen to move up and down.
6. The method of pulling a silicon single crystal according to claim 5, wherein a vertical distance between a lower edge of the water-cooled screen and a lower edge of the guide tube is referred to as a screen distance, and is denoted by m, a lower limit value of m is 15 to 25mm, and an upper limit value of m is 50 to 150mm.
7. The method of pulling a silicon single crystal according to claim 6, wherein the vertical distance between the lower edge of the guide cylinder and the liquid surface of the silicon melt is referred to as a liquid gap distance, denoted as d, and d has a value in the range of 20 to 60mm.
8. The method of pulling a silicon single crystal according to claim 7, wherein the vertical distance between the lower edge of the water-cooled shield and the liquid surface of the silicon melt is referred to as a liquid shield distance, denoted as L, l=m+d.
9. The silicon single crystal pulling method according to any one of claims 1 to 8, characterized in that the silicon single crystal pulling method comprises the steps of: (1) Providing a single crystal furnace thermal field, wherein the single crystal furnace thermal field comprises a furnace body, a coaxially arranged crucible is arranged in the furnace body, a supporting rod is connected below the crucible and used for supporting and driving the crucible to move, and a guide cylinder and a water cooling screen are arranged above the crucible; A heat preservation cylinder is arranged between the crucible and the furnace body, and comprises an upper heat preservation cylinder and a lower heat preservation cylinder which are sequentially arranged along the axial direction; the upper heat preservation cylinder is arranged on the periphery of the guide cylinder, the lower heat preservation cylinder is arranged on the periphery of the crucible, and a side heater is arranged between the lower heat preservation cylinder and the crucible; the water cooling screen is connected with a lifting mechanism, and the lifting mechanism is fixed on a furnace cover of the furnace body and used for driving the water cooling screen to move up and down; (2) Drawing a silicon single crystal by adopting a Czochralski method based on the thermal field of the single crystal furnace, and performing isodiametric growth on the silicon single crystal in the isodiametric growth stage according to the following method: (a) In the initial stage of the equal diameter with the equal diameter length of 0-500mm, a direct power control mode is adopted firstly, the set pulling speed is gradually increased by adjusting the gradual reduction of heating power, then a growth control system is started to directly adjust the set pulling speed, and the power elevation is automatically adjusted according to the difference between the set pulling speed and the actual pulling speed; In the initial stage of the equal diameter, the liquid level of the silicon melt moves upwards to gradually reduce the liquid opening distance, and meanwhile, the water cooling screen is controlled to move upwards to gradually increase the screen cylinder distance, so that the same radial position of the crystallization interface is reduced along the axial temperature gradient, the relation between the pulling speed, the axial temperature gradient of the growth interface and the OISF defect is regulated and controlled, and the OISF defect moves towards the edge of the crystal bar; (b) Under the condition of keeping the liquid opening distance and the screen cylinder distance unchanged, controlling the pulling speed V and the axial temperature gradient G of a growth interface, so that V/G is more than or equal to 0.12mm 2 /min.K from the center of the crystal bar to the 3-5mm position of the edge of the crystal bar in the radial direction of the silicon single crystal, and continuing to perform the mid-diameter stage and the end-diameter stage to obtain the silicon single crystal bar with the target isodiametric length; the pulling speed is set to be unchanged in the mid-diameter stage, the pulling speed is set to be reduced in the end-diameter stage, and the target equal-diameter of the silicon single crystal rod is 250-310mm.
10. A silicon single crystal product produced by the silicon single crystal pulling method for improving OISF defects according to any one of claims 1 to 9.

Description

Silicon single crystal pulling method for improving OISF defect and product thereof Technical Field The invention belongs to the technical field of monocrystalline silicon manufacture, and particularly relates to a silicon monocrystalline drawing method for improving OISF defects and a product thereof. Background Conventional photovoltaic PV-grade and chip IC-grade silicon single crystal growth mainly employs CZ Czochralski (CZ) method. During the growth of single crystals, various defects are easily generated inside the crystal, wherein Oxidation-induced stacking faults (OISF, also commonly referred to as Oxidation-induced stacking fault OSF) are a critical and significant risk of intrinsic defects. OISF defects result from the aggregation and evolution of point defects such as vacancies (V) and self-interstitials (I) during crystal growth under specific thermal history and stress conditions, and are induced to form extended defects in subsequent high temperature oxidation processes. Further, in semiconductor device fabrication, OISF defects may destroy lattice integrity, become scattering centers and recombination centers of carriers, resulting in increased leakage current, reduced breakdown voltage, degraded performance, and failure of the device, which severely restricts yield and reliability of the high-end integrated circuit. In the photovoltaic field, OISF defects are often concentric in distribution in a silicon wafer, are efficient carrier recombination centers, can cause significant reduction in photoelectric conversion efficiency of a solar cell, and cause abnormal dark areas or black spots in an EL (electroluminescence) test, thereby affecting power output and quality of a component. For inhibiting OISF defects, a patent CN117431620A adopts a crystal pulling method for reducing oxidation induced stacking faults of large-size silicon single crystals, and comprises the steps of pulling a plurality of crystal rods, wherein the first crystal rod has a higher crystal pulling speed than the subsequent crystal rods in an initial crystal pulling state in a crystal pulling constant diameter stage, the control time period is 2-2.5h in the ending process, the crystal rods are controlled to be lifted to a secondary chamber of a single crystal furnace after the crystal rods deviate from a liquid level after the crystal rods are completed, a gate valve between a main chamber and the secondary chamber of the single crystal furnace is closed after the crystal rods reach the secondary chamber of the single crystal furnace, air is controlled to enter the secondary chamber for cooling the crystal rods, the main chamber of the single crystal furnace is still subjected to argon circulation protection cooling in the process, and the rest crystal rods are pulled by the rest of the crystal rods according to the first crystal rod pulling operation after the previous crystal rods are pulled, so that the rest of the crystal rods are subjected to the high crystal pulling speed growth stage of the crystal rods in the crystal pulling constant diameter stage. Patent CN117604613a discloses a single crystal furnace thermal field and a single crystal furnace and a method for improving a lightly boron doped silicon single crystal OISF, the single crystal furnace thermal field comprises a furnace body, a heat insulation material, a crucible, a bottom heater, a side heater and a heat shield, the heat insulation material is arranged in the furnace body, the crucible is arranged in the heat insulation material, the side heater and the bottom heater are arranged between the crucible and the heat insulation material, the heat shield is arranged above the crucible, the upper end of the side heater extends to be flush with the upper end surface of the crucible, the heat insulation material comprises an upper ring, a middle ring and a lower ring which are sequentially arranged from top to bottom, the thickness of the middle ring is consistent with that of the lower ring, the heat shield is of a cylindrical structure with an upper opening and a lower opening and is used for guiding the flow direction of argon gas, and the inner side of the heat shield is distributed with a first vertical surface, a concave cambered surface and a second vertical surface from top to bottom in a gradient manner so as to prolong the flow path of the argon gas, and the heat quantity of solution taken away when the argon gas flows out is reduced. The thermal field of the single crystal furnace is adopted to draw the lightly boron-doped silicon single crystal, and the axial temperature gradient of the crystal bar is improved to reduce vacancies, so that vacancies combined with Oi atoms are reduced, and further OISF is improved. The prior patent has certain limitation, can not maintain or even exert the potential of high pulling speed to promote single production in actual mass production, and can dynamically and accurately regulate and control the crystal growth