Necking method for N-type 12-inch seeding in czochralski method single crystal

Abstract

The invention discloses a necking method for N-type 12-inch seeding in czochralski single crystal. The necking method comprises the following steps: step 1, determining a seeding starting period before necking; and 2, monitoring the change of the diameter of the crystal bar during seeding to obtain to-be-measured diameters with different lengths, judging the size relationship between the to-be-measured diameters and the target diameter, and determining the pulling speed during seeding until the to-be-measured diameters are consistent with the target diameter. The pulling speed is automatically controlled, dislocation is effectively eliminated, it is guaranteed that necking is smooth during seeding, the diameter of the guided fine grains is uniform, and the oxidation coloring phenomenon is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of single crystal silicon manufacturing, and in particular to a necking method for N-type 12-inch seeding in a Czochralski single crystal. Background Art

[0002] The production process of single crystal silicon includes the following steps: dismantling the furnace - loading - melting material - seeding - shoulder release - shoulder rotation - equal diameter - tailing - furnace shutdown. Among them, seeding and shoulder release is the process of using seed crystals to pull the growth of single crystals at a temperature suitable for single crystal growth by reducing the heating power of the single crystal furnace after the silicon material is melted. When the seed crystal contacts the liquid surface, dislocations will occur and a thin neck is needed to eliminate the dislocations. The temperature in the single crystal furnace is appropriate, and the thin neck can arrange the dislocations and start crystal growth. The length, quality, uniformity, thickness and average pulling speed of the seeded fine crystals all have a great influence on the survival rate of the single crystal.

[0003] In view of this, the present application is proposed to reduce the influence of necking during seeding on the survival rate of single crystals. Summary of the invention

[0004] The object of the present invention is to provide a necking method for N-type 12-inch seeding in a Czochralski single crystal, by setting various parameters during seeding to ensure smooth necking during seeding and uniform diameter of the seeded fine crystals, thereby solving the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following solutions:

[0006] A necking method for N-type 12-inch seeding in a Czochralski single crystal, comprising the following steps:

[0007] Step 1, determining the seeding start time period before necking;

[0008] Step 2: monitor the change of the diameter of the crystal rod during seeding, obtain the diameters to be measured of different lengths, determine the size relationship between the diameter to be measured and the target diameter, and determine the pulling speed during seeding until the diameter to be measured is consistent with the target diameter.

[0009] In this application, the starting time period for seeding is first determined after the silicon material is melted, and then seeding is performed. The seeding first necks and seed thin crystals, thereby eliminating dislocations and improving the survival rate of single crystals. When necking and seeding thin crystals, the system in the single crystal furnace corresponds each length of the crystal rod during seeding to a target diameter, and determines the size relationship between the diameter to be measured at this length and the target diameter, thereby changing the pulling speed, so that the diameter to be measured at this length meets the target diameter to complete necking.

[0010] Further preferably, in the step 1, after the silicon raw material is melted, the temperature stabilization time of the silicon liquid level in the crucible is ≥30 min, and the four points of the seed crystal are round and full after melting.

[0011] Further preferably, in step one, the distance between the lower edge of the guide tube and the silicon liquid surface is 31.5 mm to 32.5 mm.

[0012] More preferably, the argon flow rate is 135 sL / min; and the furnace pressure is 1.3 kPa.

[0013] Before seeding, the seeding period after welding mainly meets three conditions: the stabilization time of the silicon liquid surface, the state of the seed crystal, and the distance between the lower edge of the guide tube and the silicon liquid surface. When these three conditions are met, seeding can be started. Under the condition that the initial diameter of the seed crystal is 16mm, the necking is gradually carried out so that the crystal rod after necking meets the target diameter requirement. At the same time, the argon flow rate and furnace pressure are always kept consistent during the diameter reduction to ensure smooth necking.

[0014] At the same time, the power inside the single crystal furnace is set according to the specific furnace.

[0015] Further preferably, the step two also includes an automatic speed control system for necking, the automatic speed control system includes a camera, an information processing module and a controller, the camera is used to monitor the diameter change of the crystal rod during crystal induction, the information processing module is used to compare the size relationship between the measured diameter and the target diameter in the crystal rod, and the controller controls the pulling speed of the crystal induction according to the result obtained by the information processing module.

[0016] The pulling speed during seeding necking is controlled by an automatic speed control system, so that the measured diameter under a certain seeding length condition is consistent with the target diameter, meeting the fine grain requirements.

[0017] Further preferably, after comparison by the information processing module, when the diameter to be measured is greater than the target diameter, the pulling speed is increased;

[0018] When the diameter to be measured is equal to the target diameter, the pulling speed is maintained to continue seeding.

[0019] The information processing module will compare the measured diameter at a certain seeding length with the target diameter at this seeding length, thereby controlling the pulling speed for the next seeding length so that the final crystal rod diameter meets the target diameter requirement.

[0020] More preferably, the initial pulling speed during necking is 3.5 mm / min, the minimum pulling speed is 0.6 mm / min, and the maximum pulling speed is 8 mm / min.

[0021] Further preferably, the seeding length is 0-300 mm, and when the seeding length is 270 mm, the seeding power of the single crystal furnace is reduced by 0.5 kW.

[0022] Further preferably, during the necking, the pan rotates at 4 rpm, clockwise; and the crystal rotates at 8 rpm, counterclockwise.

[0023] The parameter settings of pot rotation and crystal rotation in step 1 and step 2 of the necking method in this application are consistent.

[0024] The beneficial effects of the present invention are as follows: the present invention is a necking method for N-type 12-inch seeding in a Czochralski single crystal, which determines the time period for seeding and then controls the pulling speed during seeding necking through an automatic speed control system, so that the measured diameter under a certain seeding length condition is consistent with the target diameter, and meets the fine crystal requirements; the pulling speed is automatically controlled, dislocations are effectively eliminated, ensuring smooth necking during seeding, uniform diameter of the seeded fine crystals, and no oxidation coloring phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a recording diagram of a seeding length of 210 mm in Example 2 of the present invention;

[0026] Figure 2 This is a recording diagram of a seeding length of 250 mm in Example 2 of the present invention;

[0027] Figure 3 This is a record diagram of the seeding length of 300 mm in Example 2 of the present invention;

[0028] Figure 4 This is a physical picture of the fine crystals obtained in Example 2 of the present invention;

[0029] Figure 5 This is a physical picture of the fine crystals obtained in the comparative example of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment 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.

[0031] The relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0032] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0033] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness.One of ordinary skill in the art will recognize that various changes and modifications may be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0034] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0035] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0036] Example 1

[0037] Embodiment 1 of the present application is a necking method for N-type 12-inch seeding in a Czochralski single crystal, comprising the following steps:

[0038] Step 1, determining the seeding start time period before necking;

[0039] Step 2: monitor the change of the diameter of the crystal rod during seeding, obtain the diameters to be measured of different lengths, determine the size relationship between the diameter to be measured and the target diameter, and determine the pulling speed during seeding until the diameter to be measured is consistent with the target diameter.

[0040] In this application, the starting time period for seeding is first determined after the silicon material is melted, and then seeding is performed. The seeding first necks and seed thin crystals, thereby eliminating dislocations and improving the survival rate of single crystals. When necking and seeding thin crystals, the system in the single crystal furnace matches multiple lengths during seeding with target diameters of corresponding lengths one by one, and each length corresponds to a target diameter, and determines the size relationship between the diameter to be measured at this length and the target diameter, thereby changing the pulling speed so that the diameter to be measured at this length meets the target diameter.

[0041] In some preferred embodiments, in step 1, after the silicon raw material is melted, the temperature stabilization time of the silicon liquid level in the crucible is ≥30 min, and the four points of the seed crystal are round and full after melting.

[0042] In some preferred embodiments, in step 1, the distance between the lower edge of the guide tube and the silicon liquid surface is 31.5 mm to 32.5 mm.

[0043] In some preferred embodiments, the argon flow rate is 135 sL / min; and the furnace pressure is 1.3 kPa.

[0044] Before seeding, the seeding period after welding mainly meets three conditions: the stabilization time of the silicon liquid surface, the state of the seed crystal, and the distance from the lower edge of the guide tube to the silicon liquid surface. When these three conditions are met, seeding can be started. Under the condition that the initial diameter of the seed crystal is 16mm, the necking is gradually carried out so that the crystal rod after necking meets the target diameter requirement. At the same time, the argon flow rate and furnace pressure are always kept consistent during the diameter reduction to ensure smooth necking.

[0045] It should be noted that the initial diameter of the seed crystal here is equivalent to the initial diameter during seeding, that is, necking is performed to the desired target diameter under the condition of this initial diameter.

[0046] At the same time, the furnace power inside the single crystal furnace is set according to the specific furnace used.

[0047] In some preferred embodiments, the step 2 also includes an automatic speed control system for necking, the automatic speed control system includes a camera, an information processing module and a controller, the camera is used to monitor the diameter change of the crystal rod during crystal induction, the information processing module is used to compare the size relationship between the measured diameter and the target diameter, and the controller controls the pulling speed of the crystal induction according to the result obtained by the information processing module.

[0048] The camera monitors the diameter at the bottom of the seeding process, and the pulling speed during seeding necking is controlled by the automatic speed control system, so that the measured diameter under a certain seeding length condition is consistent with the target diameter, see Table 1, thereby meeting the fine crystal requirements, dislocations are effectively eliminated, and there is no oxidation coloring phenomenon.

[0049] Table 1 Correspondence between different seeding lengths and target diameters

[0050]

[0051]

[0052] At the same time, the connection between the camera, information processing module and controller in this system belongs to the existing technology and will not be described in detail.

[0053] In some preferred embodiments, when the diameter to be measured is greater than the target diameter after comparison by the information processing module, the pulling speed is increased;

[0054] When the diameter to be measured is equal to the target diameter, the pulling speed is maintained to continue seeding.

[0055] The information processing module will compare the measured diameter at a certain seeding length with the target diameter at this seeding length, thereby controlling the pulling speed for the next seeding length so that the final crystal rod diameter meets the target diameter requirement.

[0056] In some preferred embodiments, the initial pulling speed during necking is 3.5 mm / min, the minimum pulling speed is 0.6 mm / min, and the maximum pulling speed is 8 mm / min.

[0057] Specifically, the initial diameter of the neck during seeding is 16mm, and the initial pulling speed is 3.5mm / min. When the seeding length is 20mm, the camera will detect the diameter at this time and transmit the diameter information to the information processing module. The information processing module will compare the measured diameter with a seeding length of 20mm with the corresponding target diameter to obtain the size relationship between the two, thereby controlling the pulling speed.

[0058] It should be noted that the seeding length will be displayed in real time in the main controller of the single crystal furnace. This is a prior art and will not be described in detail here.

[0059] In some preferred embodiments, the seeding length is 0-300 mm. When the seeding length is 270 mm, the seeding power of the single crystal furnace is reduced by 0.5 kW.

[0060] In some preferred embodiments, the pan rotates at 4 rpm, clockwise, and the crystal rotates at 8 rpm, counterclockwise during necking.

[0061] The parameter settings of pot rotation and crystal rotation in step 1 and step 2 of the necking method in this application are consistent.

[0062] Example 2

[0063] In this embodiment 2, the method of embodiment 1 is used to seed the crystal, and the survival rates in different pulling speed ranges of different lengths are compared, as shown in Table 2 below.

[0064] Table 2 Comparison of survival rate in different lengths and pulling speed intervals

[0065]

[0066] Reference Figure 1 and Figure 2 According to Table 2, when the pulling speed is constant, the survival rate of the crystal rod increases with the increase of the seeding length; when the seeding length is constant, when the seeding length is 300mm, the survival rate reaches the highest when the pulling speed range is 3.5-5.5mm / min. Therefore, the pulling speed is changed within the pulling speed range of 3.5-5.5mm / min to make the diameter of the crystal rod meet the final target diameter.

[0067] At the same time, the obtained fine grain physical map refers to Figure 4 , among which fine crystals do not produce oxidation coloring phenomenon.

[0068] Comparative Example 1

[0069] Refer to the actual picture of fine crystals obtained by seeding with conventional operation Figure 5, among which the fine crystals show oxidation and colorization.

[0070] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A necking method for N-type 12-inch seeding in a Czochralski single crystal, characterized in that: The following steps are involved: Step 1, determining the seeding start time period before necking; Step 2: monitor the change of the diameter of the crystal rod during seeding, obtain the diameters to be measured of different lengths, determine the size relationship between the diameter to be measured and the target diameter, and determine the pulling speed during seeding until the diameter to be measured is consistent with the target diameter.

2. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 1, characterized in that: In the step 1, after the silicon raw material is melted, the temperature stabilization time of the silicon liquid surface in the crucible is ≥30 minutes, and the four points of the seed crystal are round and full after melting.

3. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 1, characterized in that: In the step 1, the distance between the lower edge of the guide tube and the silicon liquid surface is 31.5 mm to 32.5 mm.

4. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 1, characterized in that: The argon flow rate is 135sL / min; the furnace pressure is 1.3kPa.

5. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 1, characterized in that: The step 2 also includes an automatic speed control system for necking, the automatic speed control system includes a camera, an information processing module and a controller, the camera is used to monitor the diameter change of the crystal rod during crystal induction, the information processing module is used to compare the size relationship between the measured diameter and the target diameter in the crystal rod, and the controller controls the pulling speed of the crystal induction according to the result obtained by the information processing module.

6. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 5, characterized in that: After comparison by the information processing module, when the diameter to be measured is larger than the target diameter, the pulling speed is increased; When the diameter to be measured is equal to the target diameter, the pulling speed is maintained to continue seeding.

7. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 5, characterized in that: The initial pulling speed during necking was 3.5 mm / min, the minimum pulling speed was 0.6 mm / min, and the maximum pulling speed was 8 mm / min.

8. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 5, characterized in that: The seeding length is 0 to 300 mm. When the seeding length is 270 mm, the seeding power of the single crystal furnace is reduced by 0.5 kW.

9. The necking method for N-type 12-inch seeding in a Czochralski single crystal according to claim 5, characterized in that: During the necking, the pan rotates at 4 rpm, clockwise; the crystal rotates at 8 rpm, counterclockwise.

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