Silicon single crystal rod oxygen concentration control method, silicon single crystal rod preparation method and silicon single crystal rod

Abstract

The invention discloses a silicon single crystal rod oxygen concentration control method, a silicon single crystal rod preparation method and a silicon single crystal rod. According to the method for controlling the oxygen concentration of the single crystal silicon rod, in the equal-diameter growth process of the single crystal silicon rod, according to the curing rate of the equal-diameter part of the single crystal silicon rod, the flow of argon flowing into the single crystal furnace for generating the single crystal silicon rod and the in-furnace pressure of the single crystal furnace are controlled by stages according to corresponding control strategies, so that the stable control of the oxygen concentration of the single crystal silicon rod can be realized; the oxygen atom concentration can be uniformly distributed along the length direction of the silicon single crystal rod, and the deviation of the oxygen atom concentration along the length direction of the silicon single crystal rod is effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of single crystal rod preparation, and particularly to a method for controlling the oxygen concentration of a single crystal rod, a method for preparing a single crystal rod, and a single crystal rod. Background Art

[0002] Single crystal rods are key basic materials for semiconductor materials and cathode manufacturing, and are usually prepared by the Czochralski method. In this method, a seed crystal is immersed in molten silicon, the quartz crucible and the seed crystal are rotated in opposite directions, and the seed crystal is pulled to grow a single crystal rod. During this process, the quartz crucible reacts with the melt to release oxygen atoms. About 99% of the released oxygen atoms evaporate in the form of SiO (monosilicon monoxide), and about 1% of the oxygen atoms flow into the interior of the single crystal rod. The oxygen atoms flowing into the interior of the single crystal rod can improve the mechanical strength and heat resistance of the wafer processed from the above single crystal rod. In addition, during the heat treatment of the wafer, the oxygen impurities diffuse out of the silicon lattice through high temperature.

[0003] As described above, the oxygen atoms flowing into the interior of the single crystal rod improve the characteristics of the single crystal wafer. However, when the concentration of oxygen atoms is not appropriate, the oxygen atoms cannot contribute well to improving the wafer characteristics. Therefore, it is very important to control the concentration of oxygen atoms flowing into the interior of the single crystal rod.

[0004] The concentration of oxygen atoms flowing into the interior of the single crystal rod varies depending on the amount of oxygen atoms released from the melt. The amount of oxygen atoms released from the melt varies depending on the contact area between the quartz crucible and the melt and the contact flow rate of the melt per unit time. Therefore, the concentration of oxygen atoms flowing into the interior of the single crystal rod can be adjusted and controlled by controlling the contact area between the quartz crucible and the melt and the contact flow rate of the melt per unit time.

[0005] However, the contact area between the quartz crucible and the melt only decreases as the single crystal grows. Therefore, it is actually very difficult to arbitrarily change the contact area. The main control factor for the oxygen atom concentration inside the single crystal rod is the contact flow rate of the melt per unit time.

[0006] In the prior art, the adjustment of the contact flow rate of the melt per unit time of the quartz crucible is carried out by controlling the crucible rotation speed and the seed crystal rotation speed. This adjustment method uses the forced convection of the melt to control the oxygen atom concentration.

[0007] However, forced convection has the characteristics of non-linearity and rapid change. Therefore, the method of adjusting the contact flow rate of the solution per unit time of the quartz crucible by controlling the crucible rotation speed and the seed crystal rotation speed cannot stably control the melt flow, resulting in difficulty in uniformly adjusting the contact flow rate of the melt per unit time of the quartz crucible as desired.

[0008] To solve this problem, the prior art has proposed the horizontal magnetic field Czochralski method. In this method, a horizontal magnetic field is applied to the melt to stabilize the melt convection. According to the horizontal magnetic field Czochralski method, the forced convection of the melt is stably controlled by the horizontal magnetic field, and the concentration of oxygen atoms is relatively easier to control.

[0009] However, the amount of melt contained in the quartz crucible gradually decreases as the single crystal silicon rod grows. Moreover, due to such a phenomenon, the oxygen atoms released from the melt will continuously decrease in the later stage of the single crystal silicon rod growth process. Therefore, when entering the later stage of the single crystal silicon rod growth process, the concentration of oxygen atoms flowing into the single crystal silicon rod will only decrease. Especially when the length of the single crystal silicon rod is relatively large, the deviation of the oxygen atom concentration between the early stage and the later stage of the single crystal silicon rod growth process will be greater.

[0010] The horizontal magnetic field Czochralski method is to stabilize the forced convection of the melt and more evenly control the concentration of oxygen atoms released per unit area in the quartz crucible. However, the horizontal magnetic field Czochralski method still has certain limitations in solving the problem of the reduction of the released oxygen atoms themselves due to the reduction of the contact area between the melt and the quartz crucible when the single crystal silicon rod growth process enters the later stage.

[0011] The prior art has also proposed to control the oxygen atom concentration in the single crystal silicon rod by adjusting the argon gas flow rate and the furnace pressure. However, in the prior art, during the entire growth process of the single crystal silicon rod, the argon gas flow rate and the furnace pressure basically remain unchanged, and the prior art does not clearly define the combination method of specific control parameters (such as the flow rate, the pressure change node, and the change amount, etc.), resulting in a large deviation of the oxygen atom concentration along the length direction of the single crystal silicon rod, especially more significant when growing a large silicon rod (with a diameter of 340 mm to 450 mm).

[0012] Therefore, how to achieve stable control of the oxygen concentration in the single crystal silicon rod and reduce the deviation of the oxygen atom concentration along the length direction of the single crystal silicon rod is an urgent problem to be solved in the field at present. Summary of the Invention

[0013] To solve the above technical problems, the present application provides a method for controlling the oxygen concentration of a single crystal silicon rod, a method for preparing a single crystal silicon rod, and a single crystal silicon rod, so as to achieve stable control of the oxygen concentration of the single crystal silicon rod, enable the oxygen atom concentration to be evenly distributed along the length direction of the single crystal silicon rod, and effectively reduce the deviation of the oxygen atom concentration along the length direction of the single crystal silicon rod.

[0014] The first object of the present application is to provide a method for controlling the oxygen concentration of a single crystal silicon rod.

[0015] The above object one of the present application is achieved by the following technical solutions:

[0016] A method for controlling the oxygen concentration of a single crystal silicon rod, the method comprising:

[0017] During the isodiameter growth process of the single-crystal silicon rod, according to the solidification rate of the isodiameter part of the single-crystal silicon rod, the argon gas flow rate flowing into the single-crystal furnace for generating the single-crystal silicon rod and the internal pressure of the single-crystal furnace are controlled in stages according to the corresponding control strategy, so as to improve the uniformity of the oxygen concentration in the length direction of the single-crystal silicon rod.

[0018] Preferably, the control process of the isodiameter growth process of the single-crystal silicon rod is divided into an initial control stage, a middle control stage, and an end control stage according to the solidification rate of the isodiameter part of the single-crystal silicon rod. Among them, the control strategies corresponding to different control stages are different.

[0019] Preferably, the step-by-step control of the argon gas flow rate flowing into the single-crystal furnace for generating the single-crystal silicon rod and the internal pressure of the single-crystal furnace according to the corresponding control strategy includes:

[0020] In the initial control stage, the argon gas flow rate flowing into the single-crystal furnace is kept unchanged after reaching the preset initial flow rate, and the internal pressure of the single-crystal furnace is kept unchanged after reaching the preset initial pressure;

[0021] In the middle control stage, the argon gas flow rate flowing into the single-crystal furnace is reduced step by step from the preset middle starting flow rate to the preset middle target flow rate, and the internal pressure of the single-crystal furnace is increased step by step to the preset middle target pressure, where the preset middle starting flow rate is less than or equal to the preset initial flow rate;

[0022] In the end control stage, the argon gas flow rate flowing into the single-crystal furnace is reduced step by step to the preset end target flow rate, and the internal pressure of the single-crystal furnace is kept unchanged at the preset middle target pressure.

[0023] Preferably, in the middle control stage, the process of the argon gas flow rate flowing into the single-crystal furnace being reduced step by step from the preset middle starting flow rate is reduced equally under the same solidification rate increment;

[0024] The process of the internal pressure of the single-crystal furnace increasing step by step is increased equally under the same solidification rate increment.

[0025] Preferably, in the middle control stage, the nodes where the argon gas flow rate flowing into the single-crystal furnace is reduced step by step from the preset middle starting flow rate coincide with the nodes where the internal pressure of the single-crystal furnace is increased step by step.

[0026] Preferably, the preset middle starting flow rate is 95% - 100% of the preset initial flow rate.

[0027] Preferably, the preset initial flow rate is 120 lpm - 150 lpm, and the preset initial pressure is 50 Torr - 90 Torr.

[0028] Preferably, the argon flow rate at which nodes start to form in the equal-diameter part of the single-crystalline silicon rod is 70% - 85% of the preset initial flow rate; the furnace pressure at which nodes start to form in the equal-diameter part of the single-crystalline silicon rod is 20% - 35% of the preset initial pressure.

[0029] The second object of the present application is to provide a method for preparing a single-crystalline silicon rod.

[0030] The above second object of the present application is achieved through the following technical solutions:

[0031] A method for preparing a single-crystalline silicon rod, the method comprising the following steps:

[0032] Growing a single-crystalline silicon rod by the Czochralski method;

[0033] During the growth of the single-crystalline silicon rod, according to the single-crystalline silicon rod oxygen concentration control method described in any one of the above first objects, the argon flow rate flowing into the single-crystal furnace for generating the single-crystalline silicon rod and the furnace pressure of the single-crystal furnace are adjusted in stages.

[0034] The third object of the present application is to provide a single-crystalline silicon rod.

[0035] The above third object of the present application is achieved through the following technical solutions:

[0036] A single-crystalline silicon rod prepared by using the single-crystalline silicon rod oxygen concentration control method described in the above second object.

[0037] The above technical solutions of the present application have the following advantages compared with the prior art:

[0038] 1. During the equal-diameter growth of the single-crystalline silicon rod, by controlling the argon flow rate flowing into the single-crystal furnace for generating the single-crystalline silicon rod and the furnace pressure of the single-crystal furnace in stages according to different control strategies based on the solidification rate of the equal-diameter part of the single-crystalline silicon rod, the argon flow rate and the furnace pressure can be precisely controlled, and the deviation of the oxygen atom concentration along the length direction of the silicon rod can be significantly reduced;

[0039] 2. It is applicable to the preparation of large single-crystalline silicon rods with a diameter of 340 mm - 450 mm, the oxygen concentration uniformity is improved, and the performance of the wafers prepared from the single-crystalline silicon rod is more stable;

[0040] 3. Specific control parameters such as the flow rate, pressure change nodes and change amounts are provided, which has strong operability and is easy to be applied industrially. Description of the Drawings

[0041] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0042] Figure 1 It is a schematic diagram for dividing the control stage according to the solidification rate of the equal-diameter part (Body) of a single-crystal silicon rod in the equal-diameter growth process of a single-crystal silicon rod in an embodiment of the present application;

[0043] Figure 2 It is a control curve graph of the argon gas flow rate and the furnace internal pressure in different control stages in an embodiment of the present application;

[0044] Figure 3 It is a comparison graph of the oxygen atom concentration change curves of the radius silicon rods obtained by the prior art solution and the solution of the embodiment of the present application in an embodiment of the present application with respect to the solidification rate of the equal-diameter part of the single-crystal silicon rod. Detailed implementation manners

[0045] In order to enable those skilled in the art to better understand the technical solutions in the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0046] In the embodiments provided by the present application, it should be understood that the disclosed methods and systems can be implemented in other ways. The system embodiments described below are only illustrative. For example, the division of units and modules is only a logical function division. In actual implementation, there may be other division methods, such as: multiple units or modules can be combined, or can be integrated into another system, or some features can be ignored, or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed with each other can be through some interfaces, indirect coupling or communication connection of devices or modules, and can be electrical, mechanical, or other forms.

[0047] In addition, each functional unit in the embodiments of the present application can be all integrated in one processor, or each unit can be separately used as a device, or two or more units can be integrated in one device; each functional unit in the embodiments of the present application can be implemented in the form of hardware, or in the form of a combination of hardware and software functional units.

[0048] Those of ordinary skill in the art can understand that all or part of the steps of implementing the following method embodiments can be completed by program instructions and related hardware. The foregoing program instructions can be stored in a computer-readable storage medium. When the program instructions are executed, the steps of the following method embodiments are executed; and the foregoing storage medium includes: various media that can store program codes such as removable storage devices, read-only memory (ROM), magnetic disks, or optical discs.

[0049] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" or "several" means two or more, unless otherwise specifically defined.

[0050] As Figure 1 shown, an embodiment of this application provides a method for controlling the oxygen concentration of a single-crystal silicon rod. The method includes:

[0051] During the equal-diameter growth process of the single-crystal silicon rod, according to the solidification rate of the equal-diameter part of the single-crystal silicon rod, the argon gas flow rate into the single-crystal furnace for generating the single-crystal silicon rod and the internal pressure of the single-crystal furnace are controlled in stages according to the corresponding control strategy to improve the uniformity of the oxygen concentration in the length direction of the single-crystal silicon rod.

[0052] In this embodiment, during the equal-diameter growth process of the single-crystal silicon rod, by precisely controlling the argon gas flow rate and the internal pressure in stages, stable control of the oxygen concentration of the single-crystal silicon rod can be achieved, so that the oxygen atom concentration can be evenly distributed along the length direction of the single-crystal silicon rod, effectively reducing the deviation of the oxygen atom concentration along the length direction of the single-crystal silicon rod, and it can be well applied to the preparation of large single-crystal silicon rods.

[0053] In one embodiment, the control process of the equal-diameter growth process of the single-crystal silicon rod is divided into an initial control stage, a middle control stage, and an end control stage according to the solidification rate of the equal-diameter part of the single-crystal silicon rod. Among them, the control strategies corresponding to different control stages are different.

[0054] Specifically, as Figure 1 shown, in this embodiment, in the order of the growth process, the grown single-crystal silicon rod includes a shoulder (Crown), an equal-diameter part (Body), and a tail (Tail). Among them, the control process of the equal-diameter growth process of the single-crystal silicon rod is divided into an initial control stage (5% < solidification rate of the equal-diameter part ≤ 35%), a middle control stage (35% < solidification rate of the equal-diameter part ≤ 82.5%), and an end control stage (82.5% < solidification rate of the equal-diameter part ≤ 100%) according to the solidification rate of the equal-diameter part (Body) of the single-crystal silicon rod.

[0055] It should be noted that the solidification rate ranges corresponding to the division of the initial control stage, the intermediate control stage, and the final control stage in this embodiment are only a preferred example. For the specific solidification rate ranges corresponding to each control stage, they can be adjusted according to the actual conditions such as the growth conditions of the single crystal silicon rod (such as the rotation speed of the quartz crucible, the rotation speed of the seed crystal, and the thermal field design). Therefore, the specific solidification rate ranges corresponding to each control stage are not limited in this embodiment.

[0056] In this embodiment, by adopting different control strategies in different stages of the initial control stage, the intermediate control stage, and the final control stage during the equal-diameter growth process of the single crystal silicon rod to control the argon gas flow rate flowing into the single crystal furnace for generating the single crystal silicon rod and the internal pressure of the single crystal furnace, the uniformity of the oxygen concentration in the length direction of the single crystal silicon rod can be effectively improved.

[0057] In one embodiment, controlling the argon gas flow rate flowing into the single crystal furnace for generating the single crystal silicon rod and the internal pressure of the single crystal furnace according to the corresponding control strategy in stages includes:

[0058] In the initial control stage, control the argon gas flow rate flowing into the single crystal furnace to remain unchanged after reaching the preset initial flow rate, and control the internal pressure of the single crystal furnace to remain unchanged after reaching the preset initial pressure;

[0059] In the intermediate control stage, control the argon gas flow rate flowing into the single crystal furnace to decrease step by step from the preset intermediate starting flow rate to the preset intermediate target flow rate, and control the internal pressure of the single crystal furnace to increase step by step to the preset intermediate target pressure, where the preset intermediate starting flow rate is less than or equal to the preset initial flow rate;

[0060] In the final control stage, control the argon gas flow rate flowing into the single crystal furnace to decrease step by step to the preset final target flow rate, and control the internal pressure of the single crystal furnace to remain unchanged at the preset intermediate target pressure.

[0061] In this embodiment, in the initial control stage, the argon gas flow rate flowing into the single crystal furnace for generating the single crystal silicon rod and the internal pressure of the single crystal furnace are stably controlled. That is, in the initial control stage, a certain argon gas flow rate and internal pressure are maintained, so that the change in the oxygen atom concentration along the length direction of the silicon rod is within a relatively small range.

[0062] In the intermediate control stage, initially, the argon gas flow rate is reduced from the preset initial flow rate to the preset intermediate starting flow rate, and then the argon gas flow rate flowing into the single crystal furnace is gradually reduced in a stepped manner from the preset intermediate starting flow rate to the preset intermediate target flow rate. At the same time, the pressure inside the single crystal furnace is gradually increased in a stepped manner to the preset intermediate target pressure. That is, when growing a single crystal silicon rod using the Czochralski method, in the length range of the silicon rod where oxygen concentration deviation occurs in the intermediate control stage, by using a stepped method, while reducing the argon gas flow rate, the pressure inside the furnace is increased, so as to reduce the oxygen concentration deviation along the length direction of the silicon rod.

[0063] In the final control stage, while controlling the argon gas flow rate to decrease in a stepped manner, the pressure inside the furnace is controlled to remain unchanged, so that the oxygen atom concentration deviation can be effectively reduced in the latter half of the single crystal silicon rod.

[0064] In one embodiment, the preset initial flow rate is 120 lpm to 150 lpm, and the preset initial pressure is 50 Torr to 90 Torr; the preset intermediate starting flow rate is 95% to 100% of the preset initial flow rate; the argon gas flow rate at which nodes start to form in the equal-diameter part of the single crystal silicon rod is 70% to 85% of the preset initial flow rate; the pressure inside the furnace at which nodes start to form in the equal-diameter part of the single crystal silicon rod is 20% to 35% of the preset initial pressure.

[0065] Preferably, the preset initial flow rate is 140 lpm, and the preset initial pressure is 80 Torr; the preset intermediate starting flow rate is 96.4% of the preset initial flow rate, that is, 135 lpm; the argon gas flow rate at which nodes start to form in the equal-diameter part of the single crystal silicon rod is 77% to 80% of the preset initial flow rate; the pressure inside the furnace at which nodes start to form in the equal-diameter part of the single crystal silicon rod is 25% of the preset initial pressure, that is, 20 Torr.

[0066] In this embodiment, by adopting the above corresponding control strategies in different stages of the initial control stage, intermediate control stage, and final control stage during the equal-diameter growth process of the single crystal silicon rod to control the argon gas flow rate flowing into the single crystal furnace for generating the single crystal silicon rod and the pressure inside the single crystal furnace, the uniformity of the oxygen concentration in the length direction of the single crystal silicon rod can be further effectively improved.

[0067] In one embodiment, in the intermediate control stage, the process of the argon gas flow rate flowing into the single crystal furnace decreasing in a stepped manner from the preset intermediate starting flow rate is a equal reduction at the same solidification rate increment; the process of the pressure inside the single crystal furnace increasing in a stepped manner is a equal increase at the same solidification rate increment.

[0068] Furthermore, the nodes at which the argon gas flow rate flowing into the single crystal furnace decreases in a stepped manner from the preset intermediate starting flow rate coincide with the nodes at which the pressure inside the single crystal furnace increases in a stepped manner.

[0069] In this embodiment, in the intermediate control stage, by synchronously reducing the argon gas flow rate and increasing the furnace pressure at the same node, both of them increase and decrease equally. In this way, when the argon gas flow rate and the furnace pressure are controlled, according to the length of the single crystal silicon rod, the oxygen atom concentration deviation is effectively reduced in the middle part of the single crystal silicon rod.

[0070] As Figure 2 shown, it is a control curve graph of the argon gas flow rate and the furnace pressure in different control stages in an embodiment of the present application. The abscissa represents the growth rate (i.e., the percentage of the length) of the equal-diameter part of the single crystal silicon rod, and the ordinate represents the argon gas flow rate (unit: lpm) flowing into the single crystal furnace and the furnace pressure (unit: Torr) of the single crystal furnace.

[0071] It can be seen from Figure 2 that in this embodiment, the preset initial flow rate maintained in the initial control stage is 140 lpm, and the preset initial pressure is 80 Torr; the preset intermediate starting flow rate is 96.4% of the preset initial flow rate, that is, the preset intermediate starting flow rate is 135 lpm; the argon gas flow rate when the equal-diameter part of the single crystal silicon rod starts to form a node (i.e., when the solidification rate is 0%) is 78.6% of the preset initial flow rate, that is, the argon gas flow rate when the equal-diameter part of the single crystal silicon rod starts to form a node is 110 lpm; the furnace pressure when the equal-diameter part of the single crystal silicon rod starts to form a node is 25% of the preset initial pressure, that is, the furnace pressure when the equal-diameter part of the single crystal silicon rod starts to form a node is 20 Torr.

[0072] In addition, it can also be seen from Figure 2 that in the intermediate control stage, the argon gas flow rate flowing into the single crystal furnace decreases step by step twice from the preset intermediate starting flow rate of 135 lpm according to the trend of decreasing 10 lpm for every 17.5% of the solidification rate (this value is equivalent to 7% of the preset initial flow rate of 140 lpm in the initial control stage), reaching the preset intermediate target flow rate of 115 lpm, that is, after the solidification rate reaches the 35% node, it is maintained at the intermediate starting flow rate of 135 lpm, after the solidification rate of 52.5%, it decreases by 10 lpm and is maintained, and after the solidification rate reaches the 70% node, it further decreases by 10 lpm and is maintained;

[0073] the furnace pressure of the single crystal furnace increases step by step twice from the preset starting pressure of 80 Torr according to the trend of increasing 10 Torr for every 17.5% of the solidification rate (this value is equivalent to 13% of the preset initial pressure of 80 Torr in the initial control stage), reaching the preset intermediate target pressure of 100 Torr, that is, after the solidification rate reaches the 35% node, it is maintained at the preset starting pressure of 80 Torr, after the solidification rate of 52.5%, it increases by 10 Torr and is maintained, and after the solidification rate reaches the 70% node, it further increases by 10 Torr and is maintained.

[0074] This embodiment provides specific control parameters such as the change nodes and change amounts of the argon flow rate and the furnace internal pressure, which are highly operable and easy to be applied industrially.

[0075] It should be noted that in the above medium-term control stage, the phased reduction ratio of the argon flow rate, the solidification rate range of the equal-diameter part maintaining the reduction of the argon flow rate, the node at which the argon flow rate starts to decrease, as well as the phased increase ratio of the furnace internal pressure, the solidification rate range of the equal-diameter part maintaining the increase of the furnace internal pressure, and the starting point of the increase of the furnace internal pressure are only one example. In different embodiments, according to the growth conditions of the single-crystal silicon rod (various factors such as the rotation speed of the quartz crucible, the rotation speed of the seed crystal, and the thermal field design), each parameter may change.

[0076] In order to better understand the advantages of the single-crystal silicon rod oxygen concentration control method of this application embodiment, the following takes multiple groups of embodiments and comparative examples for comparative analysis to demonstrate and explain the technical effects of the single-crystal silicon rod oxygen concentration control method of this application.

[0077] Specifically, in the following embodiments, the control process of the equal-diameter growth process of the single-crystal silicon rod is divided into an initial control stage (5% < solidification rate of the equal-diameter part ≤ 35%), a medium-term control stage (35% < solidification rate of the equal-diameter part ≤ 82.5%), and a final control stage (82.5% < solidification rate of the equal-diameter part ≤ 100%) according to the solidification rate of the equal-diameter part (Body) of the single-crystal silicon rod.

[0078] Example 1 (as Figure 2 shown):

[0079] The node where the equal-diameter part of the single-crystal silicon rod starts to form, control the furnace internal pressure to be 20 Torr and keep increasing; control the argon flow rate to be 110 lpm and keep increasing;

[0080] In the initial control stage, control the argon flow rate flowing into the single-crystal furnace to remain unchanged after reaching the preset initial flow rate of 140 lpm, and control the furnace internal pressure of the single-crystal furnace to remain unchanged after reaching the preset initial pressure of 80 Torr;

[0081] In the medium-term control stage, control the argon flow rate flowing into the single-crystal furnace to first decrease to 135 lpm, and then decrease step by step from the preset medium-term starting flow rate of 135 lpm to the preset medium-term target flow rate of 115 lpm, and control the furnace internal pressure of the single-crystal furnace to increase step by step from the preset initial pressure of 80 Torr to the preset medium-term target pressure of 100 Torr;

[0082] In the final control stage, control the argon flow rate flowing into the single-crystal furnace to decrease step by step to the preset final target flow rate of 95 lpm, and control the furnace internal pressure of the single-crystal furnace to remain unchanged at the preset medium-term target pressure of 100 Torr.

[0083] Example 2:

[0084] The preset initial flow rate is 120 lpm, and other control processes and control parameters are the same as those in Embodiment 1;

[0085] Embodiment 3:

[0086] The preset initial flow rate is 150 lpm, and other control processes and control parameters are the same as those in Embodiment 1;

[0087] Embodiment 4:

[0088] The preset initial pressure is 50 Torr, and other control processes and control parameters are the same as those in Embodiment 1;

[0089] Embodiment 5:

[0090] The preset initial pressure is 90 Torr, and other control processes and control parameters are the same as those in Embodiment 1;

[0091] Comparative Example 1 (Prior Art):

[0092] During the entire growth process of the equal-diameter part of the single-crystal silicon rod, the argon gas flow rate is 120 lpm, and the pressure inside the furnace is 20 lpm.

[0093] The correspondence table between the oxygen atom content and the solidification rate range of the single-crystal silicon rods obtained in the above 5 embodiments and 1 comparative example is shown in the following table:

[0094]

[0095] In the above table, Ar represents the argon gas flow rate flowing into the single-crystal furnace, with the unit of lpm, P represents the pressure inside the single-crystal furnace, with the unit of Torr, and Oi represents the oxygen atom content, with the unit of ppma.

[0096] By comparing the oxygen atom content of the single-crystal silicon rods in the above table, it can be seen that:

[0097] In Comparative Example 1, the oxygen atom content of the equal-diameter part of the single-crystal silicon rod fluctuates greatly in each solidification rate range. In the range of 5% - 35% solidification rate, the oxygen atom content is 16.5 - 14.3; in the range of 35% - 82.5% solidification rate, the oxygen atom content is 14.3 - 13.6; in the range of 82.5% - 100% solidification rate, the oxygen atom content is 13.6 - 12.4.

[0098] In Embodiments 1 - 5, the deviation of the oxygen atom content of the equal-diameter part of the single-crystal silicon rod in each solidification rate range is relatively small, indicating that the single-crystal silicon rod oxygen concentration control method of the present application can achieve stable control of the oxygen concentration of the single-crystal silicon rod, enabling the oxygen atom concentration to be evenly distributed along the length direction of the single-crystal silicon rod and effectively reducing the deviation of the oxygen atom concentration along the length direction of the single-crystal silicon rod.

[0099] Among them, the deviation of the oxygen atom content in the isodiametric part of the single-crystal silicon rod in Example 1 is the smallest in each curing rate interval, indicating that the argon gas flow rate and the furnace internal pressure in the Example are more excellent than those in Examples 2 to 5 in each control mode at each control stage.

[0100] As Figure 3 shown, it is a comparative graph of the change curves of the oxygen atom concentration of the radius silicon rod obtained by the prior art solution (Comparative Example 1) and the solution of the Example of the present application (Example 1) in an embodiment of the present application. Among them, the abscissa represents the curing rate of the isodiametric part of the single-crystal silicon rod, the ordinate represents the oxygen atom content, the curve before the change shown by the black square is the change curve of the oxygen atom concentration with the curing rate of the isodiametric part of the single-crystal silicon rod in Comparative Example 1, and the curve after the change shown by the white square is the change curve of the oxygen atom concentration with the curing rate of the isodiametric part of the single-crystal silicon rod in Example 1.

[0101] According to Figure 3 and the above comparison table, when using the control method of Example 1 of the present application, the deviation of the oxygen atom concentration in the 5% - 100% part of the isodiametric curing rate of the single-crystal silicon rod is -1.2 (the minimum value of Oi is 13.0, and the maximum value of Oi is 14.2). When using the prior art shown in Comparative Example 1 with the argon gas flow rate and the internal pressure fixed and unchanged, the deviation of the oxygen atom concentration in the 5% - 100% part of the isodiametric curing rate of the single-crystal silicon rod is -4.1 (the minimum value of Oi is 12.4, and the maximum value of Oi is 16.5). This shows that when using the control method of stage-by-stage controlling the argon gas flow rate and the furnace internal pressure in the Example of the present application, the absolute value of the oxygen atom concentration gradient is reduced compared with that in the prior art when the argon gas flow rate and the internal pressure are not changed, that is to say, the oxygen concentration deviation along the length direction of the single-crystal silicon rod is reduced.

[0102] Example 1 of the present application also provides a method for preparing a single-crystal silicon rod, which includes the following steps:

[0103] Growing a single-crystal silicon rod by the Czochralski method;

[0104] During the growth of the single-crystal silicon rod, stage-by-stage adjust the argon gas flow rate flowing into the single-crystal furnace for generating the single-crystal silicon rod and the furnace internal pressure of the single-crystal furnace according to the single-crystal silicon rod oxygen concentration control method described in any of the above embodiments.

[0105] Since the method for preparing the single-crystalline silicon rod adjusts the flow rate of argon gas flowing into the single-crystal furnace for generating the single-crystalline silicon rod and the internal pressure of the single-crystal furnace in stages by using the oxygen concentration control method for the single-crystalline silicon rod described in any of the above embodiments of the present application, therefore, the stable control of the oxygen concentration of the single-crystalline silicon rod can also be achieved, so that the oxygen atom concentration can be evenly distributed along the length direction of the single-crystalline silicon rod, effectively reducing the deviation of the oxygen atom concentration along the length direction of the single-crystalline silicon rod.

[0106] An embodiment of the present application further provides a single-crystalline silicon rod, which is prepared by using the oxygen concentration control method for the single-crystalline silicon rod described in the above embodiment.

[0107] Since the single-crystalline silicon rod is prepared by using the oxygen concentration control method for the single-crystalline silicon rod described in the above embodiment, therefore, the single-crystalline silicon rod has the advantage of small deviation of the oxygen atom concentration along the length direction of the single-crystalline silicon rod, and the performance of the wafer prepared by the single-crystalline silicon rod is more stable.

[0108] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0109] Those skilled in the art can further realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed in this embodiment can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components and steps of the examples have been generally described according to their functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0110] The steps of the method or algorithm described in combination with the embodiments disclosed in this embodiment can be directly implemented by hardware, a software module executed by a processor, or a combination of the two. The software module can be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field.

[0111] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling oxygen concentration of a single crystal silicon rod, characterized in that: The method comprises: During the equal-diameter growth process of the single crystal silicon rod, according to the solidification rate of the equal-diameter part of the single crystal silicon rod, the argon flow rate flowing into the single crystal furnace for generating the single crystal silicon rod and the furnace pressure of the single crystal furnace are controlled in stages according to the corresponding control strategy to improve the uniformity of the oxygen concentration of the single crystal silicon rod in the length direction.

2. The method for controlling oxygen concentration of a single crystal silicon rod according to claim 1, characterized in that: The control process of the equal-diameter growth process of the single crystal silicon rod is divided into an initial control stage, a mid-term control stage and a final control stage according to the solidification rate of the equal-diameter part of the single crystal silicon rod, wherein different control stages correspond to different control strategies.

3. The method for controlling oxygen concentration of a single crystal silicon rod according to claim 2, characterized in that: The step of controlling the flow rate of argon gas flowing into the single crystal furnace for producing the single crystal silicon rods and the pressure inside the single crystal furnace in accordance with corresponding control strategies in stages includes: In the initial control stage, the flow rate of argon gas flowing into the single crystal furnace is controlled to remain unchanged after reaching a preset initial flow rate, and the pressure in the single crystal furnace is controlled to remain unchanged after reaching a preset initial pressure; In the mid-term control stage, the argon flow rate flowing into the single crystal furnace is controlled to decrease in a step-like manner from a preset mid-term starting flow rate to a preset mid-term target flow rate, and the pressure in the single crystal furnace is controlled to increase in a step-like manner to a preset mid-term target pressure, wherein the preset mid-term starting flow rate is less than or equal to the preset initial flow rate; In the final control stage, the flow rate of argon gas flowing into the single crystal furnace is controlled to be reduced in steps to a preset final target flow rate, and the pressure in the single crystal furnace is controlled to remain unchanged at the preset mid-term target pressure.

4. The method for controlling oxygen concentration of a single crystal silicon rod according to claim 3, characterized in that: In the mid-term control stage, the process in which the argon gas flow rate flowing into the single crystal furnace is reduced in a step-like manner from a preset mid-term starting flow rate is an equal amount reduction at the same solidification rate increment; The process in which the pressure in the single crystal furnace increases in a step-like manner is an equal increase at the same solidification rate increment.

5. The method for controlling oxygen concentration of a single crystal silicon rod according to claim 4, characterized in that: In the mid-term control stage, the node where the argon gas flow rate flowing into the single crystal furnace decreases in a step-like manner from a preset mid-term starting flow rate is consistent with the node where the pressure in the single crystal furnace increases in a step-like manner.

6. The method for controlling oxygen concentration in a single crystal silicon rod according to any one of claims 3 to 5, characterized in that: The preset mid-term starting flow rate is 95% to 100% of the preset initial flow rate.

7. The method for controlling oxygen concentration in a single crystal silicon rod according to any one of claims 3 to 5, characterized in that: The preset initial flow rate is 120 lpm to 150 lpm, and the preset initial pressure is 50 Torr to 90 Torr.

8. The method for controlling oxygen concentration in a single crystal silicon rod according to any one of claims 3 to 5, characterized in that: The argon flow rate at which the equal-diameter part of the single crystal silicon rod begins to form nodes is 70% to 85% of the preset initial flow rate; the furnace pressure at which the equal-diameter part of the single crystal silicon rod begins to form nodes is 20% to 35% of the preset initial pressure.

9. A method for preparing a single crystal silicon rod, characterized in that: The method comprises the following steps: The Czochralski method is used to grow single crystal silicon rods; During the growth of the single crystal silicon rod, the single crystal silicon rod oxygen concentration control method according to any one of claims 1 to 8 adjusts the argon flow rate flowing into the single crystal furnace for generating the single crystal silicon rod and the furnace pressure of the single crystal furnace in stages.

10. A single crystal silicon rod, characterized in that: The single crystal silicon rod is prepared by the single crystal silicon rod oxygen concentration control method according to claim 9.

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