CN116200810A - Control method for micro defects of silicon crystal body - Google Patents

Control method for micro defects of silicon crystal body Download PDF

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Publication number
CN116200810A
CN116200810A CN202111446129.1A CN202111446129A CN116200810A CN 116200810 A CN116200810 A CN 116200810A CN 202111446129 A CN202111446129 A CN 202111446129A CN 116200810 A CN116200810 A CN 116200810A
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silicon crystal
segment
temperature
standard
section
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袁长宏
娄中士
李鹏飞
田旭东
李振
闫鹏飞
沙志强
张净源
周宏邦
贾海洋
王淼
张强
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Inner Mongolia Central Leading Semiconductor Materials Co ltd
Zhonghuan Advanced Semiconductor Materials Co Ltd
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Inner Mongolia Central Leading Semiconductor Materials Co ltd
Zhonghuan Advanced Semiconductor Materials Co Ltd
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Priority to CN202111446129.1A priority Critical patent/CN116200810A/en
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/20—Controlling or regulating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K13/00—Thermometers specially adapted for specific purposes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • General Physics & Mathematics (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)

Abstract

A control method of micro defect of silicon crystal body, in the course of equal diameter growth of silicon crystal, the section of equal diameter that has already pulled out carries on the sectional temperature measurement; obtaining temperature measurement values of each segmented isodiametric segment of the silicon crystal, comparing the temperature measurement values with standard temperatures of corresponding segmented isodiametric segments, and selecting a heat preservation mode suitable for each segmented isodiametric segment of the silicon crystal so that the temperature of each segmented isodiametric segment of the silicon crystal is within a standard temperature range of the corresponding segment; and comparing the index of the bulk micro defect density of the silicon crystal with the standard bulk micro defect density, and determining the heat preservation time of the constant diameter section within the standard temperature range of the constant diameter section to obtain the silicon crystal conforming to the index of the bulk micro defect density. The invention can change the nucleation degree of the oxygen precipitate in the silicon crystal in different gradient sectional temperature ranges so as to change the growth condition of BMD, obtain the silicon crystal with different BMD densities required by different requirements, and adapt to the silicon crystal with the BMD density required by different end products.

Description

Control method for micro defects of silicon crystal body
Technical Field
The invention belongs to the technical field of Czochralski crystal growth, and particularly relates to a control method for micro defects of a silicon crystal body.
Background
BMD (Bulk Micro Defect ) for Czochralski silicon single crystal used for large scale integrated circuit fabrication, it is generally considered that oxygen present in a gap state is in a supersaturated state in a temperature range (.ltoreq.1200℃) of a general device manufacturing process because oxygen is introduced into a silicon wafer at about 1400 ℃ at a melting point temperature. These oxygen impurities may cause oxygen precipitation due to a decrease in solid solubility during thermal cycling of the device process, and may induce secondary defects such as dislocation, stacking fault, and the like. Excessive oxygen precipitation can also cause phenomena such as slippage, warping and the like, and seriously affects the yield of devices. But at the same time, the defect has the internal gettering characteristic, so that the point defect in the silicon single crystal and heavy metal impurities introduced in the device process can be effectively removed, and the pollution to the surface source region is reduced;
the oxygen precipitate also has stronger capability of pinning dislocation, greatly improves the mechanical strength of the silicon wafer, can greatly inhibit the warpage of the silicon wafer in the subsequent thermal cycle process, and improves the yield of devices. These are all related to the density of oxygen precipitates generated during the cooling of the silicon single crystal
In such applications, the BMD of such oxide precipitates needs to be correlated, matched to the chip thermal process, rather than simply pursuing too low BMD or too high BMD. In the existing conventional single crystal growth process, after the silicon crystal grows to leave the solid-liquid interface, the silicon crystal sequentially enters the auxiliary chamber from the main chamber, and no other operation is performed, so that the existing crystal pulling method cannot realize the further control function of BMD, but is determined by an initial crystal crystallization process; control of BMD defect density cannot be achieved, which causes trouble to subsequent chip manufacturing processes.
Therefore, how to dynamically control the BMD density in the process of growing single crystal silicon becomes a major problem of improving the quality, high utilization rate and yield of semiconductor silicon crystal, and needs to be solved.
Disclosure of Invention
The invention provides a control method of micro defects in a silicon crystal body, which solves the technical problem that the BMD density cannot be dynamically controlled in the silicon crystal growth process in the prior art.
In order to solve at least one of the technical problems, the invention adopts the following technical scheme:
a control method of micro defects in a silicon crystal body comprises the following steps:
in the equal-diameter growth process of the silicon crystal, carrying out sectional temperature measurement on the pulled equal-diameter section;
obtaining temperature measurement values of each segmented isodiametric segment of the silicon crystal, comparing the temperature measurement values with standard temperatures of corresponding segmented isodiametric segments, and selecting a heat preservation mode suitable for each segmented isodiametric segment of the silicon crystal so that the temperature of each segmented isodiametric segment of the silicon crystal is within a standard temperature range of the corresponding segment;
and comparing the index of the bulk micro defect density of the silicon crystal with the standard bulk micro defect density, and determining the heat preservation time of the constant diameter section within the standard temperature range of the constant diameter section to obtain the silicon crystal conforming to the index of the bulk micro defect density.
Further, the selecting a heat preservation mode suitable for each segmented constant diameter segment of the silicon crystal specifically comprises the following steps:
measuring the temperature of each section of the pulled constant diameter section along the pulling direction of the silicon crystal;
judging whether the measured temperature of each isodiametric section of the silicon crystal is within the standard temperature range of the isodiametric section of the section;
if yes, continuing to monitor the temperature of the constant diameter section;
if the temperature is lower than the standard temperature, heating the constant-diameter section;
if the temperature is higher than the standard temperature, cooling the constant-diameter section;
the position of the measured temperature of each constant diameter section is the position of the constant diameter section close to the nearest point of the solid-liquid interface.
Further, the segments of the isodiametric section from which the silicon crystal is pulled out are based on the nucleation temperature range of the point micro defect and the height corresponding to the nucleation temperature range of the bulk micro defect, and the isodiametric section comprises a first segment and a second segment which are sequentially connected from bottom to top along the length direction of the first segment and the second segment, and the second segment is arranged close to one side of the head; the standard temperature of the first segment is greater than the standard temperature of the second segment.
Further, the position of the first section is located within the range of 500-900mm from the solid-liquid interface;
the second section is positioned within a range of 700-1100mm from the solid-liquid interface.
Further, the first segment corresponds to a formation position where the point micro defect is located; the second segment corresponds to a formation location of the bulk micro defect.
Further, the nucleation temperature of the point micro defect is 950-1150 ℃; the nucleation temperature of the bulk micro defect is 600-950 ℃.
Further, the standard temperature of the first segment is the highest value of nucleation temperature of the point micro defect, and is 1150+/-50 ℃.
Further, the standard temperature of the second segment is the highest value of nucleation temperature of the bulk micro defect, which is 950+/-50 ℃.
Further, the determining the heat preservation duration of the constant diameter section within the standard temperature range specifically includes:
controlling each constant diameter section within the standard temperature range;
judging the index of the bulk micro defect density of the silicon crystal and the standard bulk micro defect density of the silicon crystal;
based on the standard heat-preserving duration of each equal-diameter section of the silicon crystal, adjusting the heat-preserving duration of each equal-diameter section of the silicon crystal;
wherein the standard bulk micro defect density of the silicon crystal is 1E+9-5E+9.
Further, when the index of the bulk micro defect density of the silicon crystal is larger than the standard bulk micro defect density of the silicon crystal, controlling the heat preservation duration of the first section to be smaller than the standard heat preservation duration of the first section, and controlling the heat preservation duration of the second section to be longer than the standard heat preservation duration of the second section.
Further, when the index of the bulk micro defect density of the silicon crystal is smaller than the standard bulk micro defect density of the silicon crystal, controlling the heat preservation time length of the first section to be longer than the standard heat preservation time length of the first section, and controlling the heat preservation time length of the second section to be shorter than the standard heat preservation time length of the second section.
Further, the standard heat preservation duration of the first section is 1-3h; and the standard heat preservation duration of the second section is 3-5h.
By adopting the control method of the silicon crystal internal micro defect designed by the invention, the body surface temperature of the different segmented constant diameter sections of the pulled silicon crystal is monitored to adjust the heat preservation mode of the constant diameter sections of the sections; and then, according to the index requirements of the BMD density of the silicon crystal, selecting the heat preservation time lengths of different sectional constant diameter sections to change the nucleation degree of the oxide precipitate in the silicon crystal in different gradient sectional temperature ranges, thereby dynamically changing the growth condition of the BMD, obtaining the silicon crystal with different BMD densities, and adapting to the silicon crystal with the BMD density required by different end products.
Drawings
FIG. 1 is a flow chart of a method for controlling micro-defects in a silicon crystal according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a silicon crystal pulling state according to an embodiment of the present invention;
FIG. 3 is a microscopic image of the standard single crystal NPC containing standard bulk micro defect density in accordance with the present invention;
FIG. 4 is a microscopic view showing the density of micro defects contained in the silicon crystal of example 1 of the present invention;
FIG. 5 is a microscopic view showing the density of micro defects contained in the silicon crystal of example 2 in the present invention.
In the figure:
10. main chamber 20, sub-chamber 30, silicon crystal
31. First segment 32, second segment 40, and first temperature stabilization device
50. Second temperature stabilizing device 60 and thermometer
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples.
The embodiment provides a method for controlling micro defects in a silicon crystal, as shown in fig. 1, comprising the following steps:
s1, in the equal-diameter growth process of the silicon crystal 30, the pulled equal-diameter section is subjected to sectional temperature measurement.
Silicon crystal 30 may be grown for any process, such as CZ, MCZ, and FZ; in this example, a silicon crystal 30 prepared by the CZ method is taken as an example, and a drawing structure is shown in fig. 2.
In the growth process of the silicon crystal 30, the polysilicon material is melted into silicon melt, then seeding is carried out through butt joint of seed crystal and silicon melt so as to remove dislocation, and then growth is carried out through links such as shoulder expansion, shoulder rotation, equal diameter and the like; defects are always accompanied during the growth of the silicon single crystal, and the defects are changed from point defects to point micro defects in the silicon crystal 30 along with the reduction of temperature, and then bulk micro defects are gradually formed from the point micro defects. Since many defects exist at the head of the silicon crystal 30 and need to be removed, only the isodiametric section of the silicon crystal 30 is the finished section.
Specifically, the temperature of the solid-liquid interface at which the silicon crystal 30 starts to grow is about 1420 ℃, and the equilibrium temperature can be maintained due to the point defects generated at the solid-liquid interface, that is, the gaps and vacancies at the solid-liquid interface are balanced. The silicon crystal 30 continues to be lifted upwards after solidification, along with the rising of the silicon crystal 30, the constant diameter section after leaving the solid-liquid interface begins to be gradually cooled, the constant diameter section of the silicon crystal 30 begins to be cooled from 1400 ℃, at this time, oxygen in the constant diameter section of the silicon crystal 30 begins to diffuse to the outside of the silicon crystal 30, and gaps and vacancies in the constant diameter section of the silicon crystal 30 begin to undergo recombination and other reactions to form point defects. When the temperature is lowered to 1150 c, supersaturated point defects start to precipitate, forming point micro defects such as COP, FPD, LSTD, and the like. The isodiametric section of the silicon crystal 30 continues to move upwards, and the point micro-defect in the silicon crystal 30 consumes adjacent point defects when the temperature is reduced from 1150 ℃ to 950 ℃, so that the vacancy defects and oxygen are polymerized to form an oxygen compound, and the point micro-defect starts to nucleate and grow up and expand. When the temperature of the silicon crystal 30 is continuously reduced from 950 ℃ to 600 ℃, vacancies and oxygen atoms form an oxygen polymer, and the residual vacancy point defects promote nucleation of oxygen precipitates, forming bulk micro defects. The temperature range of existence of point defects is 1150-1400 ℃; the nucleation temperature of the point micro defect is 950-1150 ℃; the nucleation temperature of the bulk micro defect is 600-950 ℃.
In the art, the semiconductor grade silicon single crystal is called NPC standard single crystal, and the density of bulk micro defects in the isodiametric section thereof is the standard bulk micro defect density of the silicon crystal 30, which is 1e+9-5e+9; the standard segment of the isodiametric segment of the NPC standard single crystal is the segment standard of the isodiametric segment from which the silicon crystal 30 has been pulled out, and the segment standard is based on the height corresponding to the nucleation temperature range of the point microdefect and the nucleation temperature range of the bulk microdefect in the silicon crystal 30. That is, the section of the constant diameter section of the NPC standard single crystal, that is, the section of the constant diameter section of the silicon crystal 30, is a first section 31 and a second section 32 which are sequentially connected and divided from bottom to top along the pulling direction of the silicon crystal 30; and the standard temperature of the first section 31 is higher than the standard temperature of the second section 32.
The first section 31 is positioned in the range of 500-900mm from the solid-liquid interface height, spanning the primary chamber 10 and the secondary chamber 20; the second section 32 is positioned within the sub-chamber 20 and near one end of the chamber at a height in the range of 700-1100mm from the solid-liquid interface. The nucleation temperature range for the point micro defects is 950-1150 ℃; the nucleation temperature of the bulk micro-defect ranges from 600 ℃ to 950 ℃, i.e. the first segment 31 corresponds to the formation position of the point micro-defect; the second segment 32 corresponds to the formation location of the bulk micro defect.
Since the temperature of the silicon crystal 30 is changed from high temperature to low temperature, the initial nucleation temperature at which the point defect is formed after the point defect enters the first segment 31 should be the highest temperature value of the point defect; accordingly, the initial nucleation temperature at which the bulk micro-defect is formed after the point micro-defect enters the second section 32 should be the highest temperature value of the bulk micro-defect. Meanwhile, since the nucleation temperatures have certain variation amplitude, and in order to improve the accuracy of the nucleation temperatures, the standard temperature of the first section 31 is set to be the maximum value of the nucleation temperature of the point micro defect, and is 1150+/-50 ℃; the standard temperature of the second segment 32 is the maximum value of nucleation temperature of the bulk micro defect, which is 950+/-50 ℃; this ensures that the temperature entering the first and second sections 31, 32 is reasonably controllable. Therefore, the position point of the measured temperature of each isodiametric segment of the silicon crystal 30 should be selected to be the temperature of the position point of the isodiametric segment near the closest point of the solid-liquid interface, that is, the position of the measured temperature of the first segment 31 is at the lowest point a of the first segment 31, and the inlet temperature of the first segment 31 is the measured temperature of the first segment 31; accordingly, the position of the measured temperature of the second segment 32 is at the lowest point B of the second segment 32, and the monitored inlet temperature of the second segment 32 is the measured temperature of the second segment 32. The temperature is measured by adopting a common infrared thermometer, that is, a thermometer 60 is arranged at the positions A and B respectively, and the equal diameter sections of the first section 31 and the second section 32 are measured respectively.
For NPC standard single crystals, the point micro defects are extremely unstable at high temperature, so that the nucleation speed is high, and the required nucleation time is short; accordingly, bulk micro defects nucleate at a lower temperature, requiring more time. Therefore, for semiconductor grade silicon crystals, if the nucleation temperature of the point micro defects in the first section 31 is always within 950-1150 ℃ and the heat preservation time is 1-3h; and the nucleation temperature of the bulk micro defects in the second section 32 is always 600-950 ℃ and the heat preservation time is 3-5h, so that the NPC standard single crystal with the standard bulk micro defect density of 1E+9-5E+9 can be obtained. That is, the standard incubation period T1 of the first segment 31 is 1-3h, the standard incubation period T2 of the second segment 32 is 3-5h, and the standard bulk micro defect density is 1E+9-5E+9.
S2, obtaining temperature measurement values of each segmented isodiametric segment of the silicon crystal 30, comparing the temperature measurement values with the standard temperature of the corresponding segmented isodiametric segment, and selecting a heat preservation mode suitable for each segmented isodiametric segment of the silicon crystal 30 so that the temperature of each segmented isodiametric segment of the silicon crystal 30 is within the standard temperature range of the corresponding segment.
The method specifically comprises the following steps:
along the pulling direction of the isodiametric section of the silicon crystal 30, and the temperature is measured for each section separately.
The measured value of the first section 31 and the measured value of the second section 32 are sequentially obtained by the thermometers 60 respectively provided in the first section 31 and the second section 32.
In order to ensure the temperature of the silicon crystal 30 in the corresponding section, a first temperature stabilizing device 40 and a second temperature stabilizing device 50 are sequentially arranged in the height ranges of the first section 31 and the second section 32 respectively, and the first temperature stabilizing device 40 and the second temperature stabilizing device 50 have heating and cooling functions, and electromagnetic induction heating or copper pipe water heating can be adopted during heating; the cooling can be realized by adopting a cold water pipe for circulating cooling or introducing inert gas for cooling; in any way, as long as it has heating and cooling functions, this is a conventional device in the art, and the structure is omitted here. The first temperature stabilizing device 40 and the second temperature stabilizing device 50 are located within the height interval of the first section 31 and the second section 32, respectively, and have a height range of 50-150mm.
And judging whether the measured temperature of each constant diameter section is within the standard temperature range of the constant diameter section.
The silicon crystal 30 is stably stepped up at a constant pull rate, and whichever segment of the silicon crystal 30 must pass through the first segment 31 and the second segment 32 in order, and the constant diameter segments of the silicon crystal 30 are monitored simultaneously in the first segment 31 and the second segment 32.
If the measured temperature is within the standard temperature range, continuing to monitor the temperature of the constant diameter section. That is, if the measured temperature value of the first segment 31 is within 1150±50 ℃ or the measured temperature value of the second segment 32 is within 950±50 ℃, the temperature monitoring is continued.
And if the measured temperature is less than the standard temperature, heating the constant diameter section. If the measured temperature value of the first section 31 is less than 1150±50 ℃, the first heat preservation device 40 is controlled to heat the first section 31, so that the temperature of the first section meets the standard temperature requirement. If the measured temperature value of the second section 32 is less than 950±50 ℃, the second heat preservation device 50 is controlled to heat the second section 32, so that the temperature of the second section meets the standard temperature requirement.
If the measured temperature is higher than the standard temperature, the constant diameter section of the section is cooled. If the measured temperature value of the first section 31 is greater than 1150±50 ℃, the first heat preservation device 40 is controlled to cool the first section 31, so that the temperature of the first section meets the standard temperature requirement. If the measured temperature value of the second section 32 is greater than 950±50 ℃, the second heat preservation device 50 is controlled to cool the second section 32, so that the temperature of the second section meets the standard temperature requirement.
S3, comparing the standard bulk micro defect density with the index of the bulk micro defect density of the silicon crystal 30, and determining the heat preservation duration of the constant diameter section within the standard temperature range of the constant diameter section to obtain the silicon crystal 30 meeting the index of the bulk micro defect density.
The index of bulk micro defect density required for different terminal silicon wafers is different.
The constant diameter sections of each section are controlled within the standard temperature range, namely, the measured temperature of the first section 31 is within 1150 plus or minus 50 ℃, the measured temperature of the second section 32 is within 950 plus or minus 50 ℃, and the whole temperature of the first section 31 is ensured to be within 950-1150 ℃, and the whole temperature of the second section 32 is ensured to be within 600-950 ℃.
Comparing the target index of the bulk micro defect density of the silicon crystal 30 with the standard bulk micro defect density 1E+9-5E+9, and adjusting the heat preservation duration of each equal-diameter section of the silicon crystal 30 based on the standard heat preservation duration of each equal-diameter section of the silicon crystal 30.
When the index of the bulk micro defect density of the silicon crystal 30 is greater than the standard bulk micro defect density 1E+9-5E+9, controlling the heat preservation time period T1 of the first section 31 to be smaller than the standard heat preservation time period T1 of the first section 31, and controlling the heat preservation time period T2 of the second section 32 to be greater than the standard heat preservation time period T2 of the second section 32; that is, the first heat preservation device 40 is controlled such that the temperature of the first section 31 is always in the range of 950-1150 ℃, and the second heat preservation device 50 is controlled such that the temperature of the second section 32 is always in the range of 600-950 ℃. Also, compared to the standard heat-retaining period, the heat-retaining period t1 of the first segment 31 is shortened, and the heat-retaining period t2 of the second segment 32 is increased, that is, the nucleation time of the point micro defect is reduced and the nucleation time of the bulk micro defect is increased, so as to obtain a greater number of bulk micro defects, thereby obtaining the silicon crystal 30 with a bulk micro defect density greater than that of the standard bulk micro defect.
When the index of the bulk micro defect density of the silicon crystal 30 is smaller than the standard bulk micro defect density 1e+9-5e+9, the heat preservation time period T1 of the first section 31 is controlled to be longer than the standard heat preservation time period T1 of the first section 31, and the heat preservation time period T2 of the second section 32 is controlled to be shorter than the standard heat preservation time period T2 of the second section 32. That is, the first heat preservation device 40 is controlled such that the temperature of the first section 31 is always in the range of 950-1150 ℃, and the second heat preservation device 50 is controlled such that the temperature of the second section 32 is always in the range of 600-950 ℃. Also, compared to the standard heat-retaining period, the heat-retaining period t1 of the first segment 31 is prolonged, and the heat-retaining period t2 of the second segment 32 is shortened, that is, the nucleation time of the point micro defect is increased and the nucleation time of the bulk micro defect is shortened, so that a smaller number of bulk micro defects are obtained, and thus, a silicon crystal 30 with a bulk micro defect density less than that of the standard bulk micro defect density is obtained.
For a further understanding of the method according to the invention, the following detailed description of the solution according to the invention will be made in connection with specific examples, which are obviously only some, but not all, of the examples.
Example 1:
s1, in the equal-diameter growth process of the silicon crystal 30, carrying out sectional temperature measurement on the first section 31 and the second section 32 of the pulled equal-diameter section, and obtaining the measurement temperature of the first section 31 to be 1120 ℃ and the measurement temperature of the second section 32 to be 960 ℃.
S2, based on the measured temperature value of the first section 31 and the measured temperature value of the second section 32, which are respectively in the standard temperature ranges, heating or cooling of the first section 31 and the second section 32 is not needed.
S3, the target index of the iron micro-defect density of the silicon crystal 30 is 5E+10, which is larger than the standard body micro-defect density 1E+9-5E+9.
The first heat-retaining means 40 is controlled so that the temperature of the first segment 31 is always in the range of 950-1150 c and so that the heat-retaining period T1 of the first segment 31 is set to 50% of the standard heat-retaining period T1 of the first segment 31.
And the second heat-insulating means 50 is controlled so that the temperature of the second section 32 is always in the range of 600-950 deg.c, and so that the heat-insulating period T2 of the second section 32 is 3 hours more than the standard heat-insulating period T2 of the second section 32.
In this embodiment, the nucleation time of the point microdefect is reduced and the nucleation time of the bulk microdefect is increased to obtain a larger number of bulk microdefects, thereby obtaining a silicon crystal 30 with a bulk microdefect density greater than that of the standard bulk microdefect density, and finally obtaining a microscopic image of the silicon crystal 30, as shown in fig. 4; the number of bulk micro-defects in this embodiment is large compared to the microscopic image of a standard bulk micro-defect density silicon crystal 30 as shown in fig. 3.
Example 2:
s1, in the equal-diameter growth process of the silicon crystal 30, carrying out sectional temperature measurement on the first section 31 and the second section 32 of the pulled equal-diameter section, and obtaining the measurement temperature of the first section 31 at 1250 ℃ and the measurement temperature of the second section 32 at 800 ℃.
S2, based on the fact that the measured temperature value of the first section 31 is larger than the standard temperature value of the first section 31, the first heat preservation device 40 is controlled to start a cooling function so as to cool the temperature of the first section 31 and keep the temperature within 950-1150 ℃.
Based on the measured temperature value of the second section 32 being smaller than the standard temperature value of the second section 32, the second heat preservation device 50 is controlled to turn on the heating function so as to raise the temperature of the second section 31 and maintain the temperature thereof within 600-950 ℃.
S3, the target index of the iron micro-defect density of the silicon crystal 30 is 1E+5, which is smaller than the standard micro-defect density 1E+9-5E+9.
The first heat-retaining means 40 is controlled so that the temperature of the first section 31 is always in the range of 950-1150 c and so that the heat-retaining period T1 of the first section 31 is 2 times the standard heat-retaining period T1 of the first section 31.
And the second holding means 50 is controlled such that the temperature of the second section 32 is always in the range of 600-950 c and such that the holding time period T2 of the second section 32 is 70% of the standard holding time period T2 of the second section 32.
In this embodiment, the nucleation time of the point microdefect is increased and the nucleation time of the bulk microdefect is reduced to obtain a smaller number of bulk microdefects, thereby obtaining a silicon crystal 30 with a bulk microdefect density smaller than that of the standard bulk microdefect density, and finally obtaining a microscopic image of the silicon crystal 30, as shown in fig. 5; the number of bulk micro-defects in this embodiment is small compared to the microscopic image of a standard bulk micro-defect density silicon crystal 30 as shown in fig. 3.
The control method of the micro defect of the silicon crystal body is suitable for the silicon crystal grown by CZ, MCZ, FZ and other processes, and the heat preservation mode of the section of equal diameter section is adjusted by monitoring the body surface temperature of the section of different sections of equal diameter section from which the silicon crystal is pulled out; and then, according to the index requirements of the BMD density of the silicon crystal, selecting the heat preservation time lengths of different sectional constant diameter sections to change the nucleation degree of the oxide precipitate in the silicon crystal in different gradient sectional temperature ranges, thereby dynamically changing the growth condition of the BMD, obtaining the silicon crystal with different BMD densities, and adapting to the silicon crystal with the BMD density required by different end products.
The foregoing detailed description of the embodiments of the invention has been presented only to illustrate the preferred embodiments of the invention and should not be taken as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.

Claims (12)

1. A method for controlling micro defects in a silicon crystal, comprising the steps of:
in the equal-diameter growth process of the silicon crystal, carrying out sectional temperature measurement on the pulled equal-diameter section;
obtaining temperature measurement values of each segmented isodiametric segment of the silicon crystal, comparing the temperature measurement values with standard temperatures of corresponding segmented isodiametric segments, and selecting a heat preservation mode suitable for each segmented isodiametric segment of the silicon crystal so that the temperature of each segmented isodiametric segment of the silicon crystal is within a standard temperature range of the corresponding segment;
and comparing the index of the bulk micro defect density of the silicon crystal with the standard bulk micro defect density, and determining the heat preservation time of the constant diameter section within the standard temperature range of the constant diameter section to obtain the silicon crystal conforming to the index of the bulk micro defect density.
2. The method for controlling micro defects in a silicon crystal according to claim 1, wherein the selecting a thermal insulation mode suitable for each segmented constant diameter segment of the silicon crystal specifically comprises:
measuring the temperature of each section of the pulled constant diameter section along the pulling direction of the silicon crystal;
judging whether the measured temperature of each isodiametric section of the silicon crystal is within the standard temperature range of the isodiametric section of the section;
if yes, continuing to monitor the temperature of the constant diameter section;
if the temperature is lower than the standard temperature, heating the constant-diameter section;
if the temperature is higher than the standard temperature, cooling the constant-diameter section;
the position of the measured temperature of each constant diameter section is the position of the constant diameter section close to the nearest point of the solid-liquid interface.
3. The method for controlling an internal micro defect of a silicon crystal according to claim 1 or 2, wherein the segments of the pulled-out isodiametric section of the silicon crystal are based on the nucleation temperature range of the point micro defect and the height corresponding to the nucleation temperature range of the bulk micro defect, and the method comprises a first segment and a second segment which are sequentially connected from bottom to top along the length direction of the first segment and the second segment, and the second segment is arranged close to one side of the head; the standard temperature of the first segment is greater than the standard temperature of the second segment.
4. A method of controlling a micro defect in a silicon crystal according to claim 3, wherein the position of the first segment is located within a range of 500-900mm from the solid-liquid interface height;
the second section is positioned within a range of 700-1100mm from the solid-liquid interface.
5. The method of claim 4, wherein the first segment corresponds to a formation location of the point micro defect; the second segment corresponds to a formation location of the bulk micro defect.
6. The method for controlling a micro defect in a silicon crystal according to claim 4 or 5, wherein the nucleation temperature of the point micro defect is in the range of 950-1150 ℃; the nucleation temperature of the bulk micro defect is 600-950 ℃.
7. The method according to claim 6, wherein the standard temperature of the first segment is the highest value of nucleation temperature of the point micro defect, which is 1150+ -50deg.C.
8. The method according to claim 6, wherein the standard temperature of the second segment is a maximum value of nucleation temperature of the bulk micro defect, which is 950±50 ℃.
9. The method for controlling micro defects in a silicon crystal according to any one of claims 4 to 5 and 7 to 8, wherein the determining the heat preservation time of the constant diameter section within the standard temperature range of the constant diameter section specifically comprises:
controlling each constant diameter section within the standard temperature range;
judging the index of the bulk micro defect density of the silicon crystal and the standard bulk micro defect density of the silicon crystal; based on the standard heat-preserving duration of each equal-diameter section of the silicon crystal, adjusting the heat-preserving duration of each equal-diameter section of the silicon crystal;
wherein the standard bulk micro defect density of the silicon crystal is 1E+9-5E+9.
10. The method according to claim 9, wherein when the index of the bulk micro defect density of the silicon crystal is greater than the standard bulk micro defect density thereof, the heat-preserving period of the first segment is controlled to be shorter than the standard heat-preserving period of the first segment, and the heat-preserving period of the second segment is controlled to be longer than the standard heat-preserving period of the second segment.
11. The method according to claim 9, wherein when the index of the bulk micro defect density of the silicon crystal is smaller than the standard bulk micro defect density thereof, the thermal insulation time length of the first segment is controlled to be longer than the standard thermal insulation time length of the first segment, and the thermal insulation time length of the second segment is controlled to be shorter than the standard thermal insulation time length of the second segment.
12. The method for controlling micro defects in a silicon crystal according to claim 10 or 11, wherein the standard heat preservation time of the first segment is 1-3h; and the standard heat preservation duration of the second section is 3-5h.
CN202111446129.1A 2021-11-30 2021-11-30 Control method for micro defects of silicon crystal body Pending CN116200810A (en)

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