JP2021098629A - Single crystal growth method and single crystal growth apparatus - Google Patents

Abstract

To increase a manufacturing yield of a large-diameter silicon single crystal with no crystal defect by enhancing a PvPi margin.SOLUTION: A single crystal growth method for growing a silicon single crystal composed of a shoulder part, a body part and a tail part by a Czochralski method includes: a lifting step P4A for lifting the body part of the silicon single crystal; and a cooling body pulling up and down step P4B for changing a distance between a lower edge of the cooling body and a liquid surface of a silicon melt by pulling up and down the cooling body, the cooling body being installed so as to surround the silicon single crystal and enhancing cooling of the silicon single crystal from an outer peripheral side of the silicon single crystal.SELECTED DRAWING: Figure 4

Description

The present invention relates to a single crystal growing method and a single crystal growing device for growing a single crystal by the Czochralski method.

As a method for producing a single crystal such as a silicon single crystal, a method called the Czochralski method (hereinafter referred to as CZ method) is known. In the CZ method, a single crystal is produced by landing a seed crystal on the liquid surface of a silicon melt in a crucible and pulling the seed crystal upward.

The types and distribution of crystal defects contained in the silicon single crystal produced by the CZ method are the growth rate (pulling rate) V of the silicon single crystal and the inside of the crystal in the pulling axial direction near the crystal growth interface from the melting point to 1300 ° C. It is known that it depends on the ratio V / G with the temperature gradient G.
When the V / G is large, the pores become excessive, and void defects, which are aggregates thereof, occur. Void defects are crystal defects generally called COP (Crystal Originated Particle). On the other hand, when V / G is small, interstitial silicon atoms become excessive, and dislocation clusters due to the aggregates are generated. Therefore, in order to produce a single crystal that does not contain COP or dislocation clusters, V / G must be strictly controlled. At present, silicon single crystals for 300 mm wafers that do not contain COP or dislocation clusters are mass-produced by controlling the crystal pulling speed V.

However, even a silicon wafer that does not contain COP and dislocation clusters cut out from a silicon single crystal that has been pulled up by controlling V / G, the entire surface is not always homogeneous, and the behavior when heat-treated is different. Contains the area of. For example, between the region where COP is generated and the region where dislocation clusters are generated, there are three regions, an OSF region, a Pv region, and a Pi region, in descending order of V / G.

The OSF region contains OSF nuclei in an as-grown state, and OSF (Oxidation induced Stacking Fault) occurs when thermal oxidation treatment is performed at a high temperature of 1000 to 1200 ° C. for 1 to 10 hours. Area to do. The Pv region contains oxygen-precipitated nuclei in an as-grown state, and is a region in which oxygen precipitates are likely to be generated when two-step heat treatment of low temperature and high temperature is performed. The Pi region is a region in which oxygen precipitate nuclei are hardly contained in the as-grown state, and oxygen precipitates are unlikely to be generated even after heat treatment.

As a method for producing a silicon single crystal having few crystal defects, for example, in Patent Document 1, a manufacturing apparatus having a cooling unit installed so as to surround the silicon crystal and a heating unit above the cooling unit is used, and the crystal temperature is changed from the crystal solidification temperature to the crystal temperature of 1300. It is described that the cooling gradient up to ° C. is 2 ° C./mm or more, and then the crystal is pulled up under the condition that the holding region at the crystal temperature of 1200 ° C. or higher and the solidification temperature or lower is 200 mm or higher. According to the method for producing a silicon single crystal described in Patent Document 1, a CZ silicon single crystal having extremely few COP defects or dislocation defects and excellent device characteristics such as oxide film pressure resistance characteristics and PN junction leak current characteristics can be produced. Is possible.

Further, Patent Document 2, while the ingot is grown, any portion temperature of the ingot so as not to cool aggregation occurs temperature T _{A (eg} 1050 ° C.) of the ingot to a temperature lower than the intrinsic point defects in the ingot It is described that by adjusting the above, a single crystal silicon ingot having substantially no aggregation intrinsic point defect is grown. In this way, giving time to the single crystal stay to a temperature higher than the temperature T _A of agglutination results in a sufficiently either by annihilation of interstitial silicon atoms and vacancies, or by causing out-diffuse, at least a constant It grows a single crystal silicon ingot whose diametrical portion is substantially free of agglutinating intrinsic point defects.

Japanese Unexamined Patent Publication No. 11-433396 Special Table 2003-517412

By the way, the crystal diameter is steadily increasing, but as the diameter increases, the central portion of the crystal becomes harder to cool than the outer peripheral portion of the crystal, the temperature gradient G in the crystal in the pulling axial direction becomes smaller, and the temperature gradient G in the crystal becomes smaller. The distribution of the temperature gradient G in the cross section of the silicon single crystal orthogonal to the pulling axis direction tends to be non-uniform. As a result, the permissible width of V / G that can make the entire surface of the cross section of the silicon single crystal orthogonal to the pulling axis direction into the Pv region or the Pi region becomes very narrow, and it is rapidly difficult to control the crystal pulling speed V. There is a problem of becoming.

Therefore, an object of the present invention is to obtain an allowable width of a crystal pulling speed V (hereinafter, referred to as "PvPi margin") capable of forming the entire surface of a silicon single crystal orthogonal to the pulling axis direction into a Pv region or a Pi region. It can be expanded to increase the production yield of large-diameter silicon single crystals having a diameter of 300 mm or more that do not contain COP and dislocation clusters, thereby improving the productivity of large-diameter silicon wafers that do not contain COP and dislocation clusters and have a diameter of 300 mm or more. It is an object of the present invention to provide a possible single crystal growth method and a single crystal growth apparatus.

The present invention is suitable for producing a large-diameter silicon single crystal having a diameter of 300 mm or more, which does not contain COP and dislocation clusters, but COP and dislocation even in the production of a relatively small-diameter silicon single crystal having a diameter of less than 300 mm. It has the effect of increasing the production yield of silicon single crystals that do not contain clusters. Hereinafter, a silicon single crystal containing no COP and dislocation clusters will be referred to as a defect-free silicon single crystal, and a silicon wafer not containing COP and dislocation clusters will be referred to as a defect-free wafer.

The single crystal growing method of the present invention is a single crystal growing method for growing a silicon single crystal composed of a shoulder portion, a body portion, and a tail portion by a Czochralski method, and pulls up the body portion of the silicon single crystal. During the pulling step and the execution of the pulling step, a cooling body installed so as to surround the silicon single crystal and promoting cooling of the silicon single crystal is moved up and down from the outer peripheral side of the silicon single crystal to cool the silicon single crystal. It is characterized by having a cooling body elevating step for changing the distance between the lower end of the body and the liquid level of the silicon melt.

In the cooling body elevating step, it is preferable to lower the cooling body from the position at the start of pulling up the body portion (body portion starting position).

In the cooling body elevating step, it is preferable that the cooling body is lowered from the position at the start of pulling up the body portion and then raised.

In the single crystal growing method, in the pulling step, the body portion is pulled up in the order of three regions of a top region, a middle region, and a bottom region, and in the cooling body raising / lowering step, the distance during pulling up of the middle region. However, it is preferable to raise and lower the cooling body so as to be smaller than the distance at the start of pulling up the body portion and the distance at the end of pulling up the body portion (preset position of the end of the body portion). ..

In the single crystal growing method, in the cooling body elevating step, the cooling body is lowered at a pulling rate of 20% to 30% of the body portion, and the cooling body is raised at a pulling rate of 70% to 90% of the body portion. It is preferable to let it.
Here, the pull-up rate of the body portion is defined as a position in the crystal longitudinal direction defined as a preset length of the body portion as 100% and a start position of the body portion as 0% in the production of a single crystal. Is. Normally, when the single crystal is normally grown without any trouble on the device and without dislocation of the single crystal, the length of the grown body portion becomes the same as the preset length of the body portion. ..

The single crystal growing device of the present invention is a single crystal growing device that grows a silicon single crystal composed of a shoulder portion, a body portion, and a tail portion by a Czochralski method, and includes a rutsubo that holds a silicon melt and the above. The control device includes a cooling body that is installed so as to surround the silicon single crystal and can be raised and lowered to promote cooling of the silicon single crystal from the outer peripheral side, and at least a control device that controls the cooling body. It is characterized by having a cooling body control unit that raises and lowers the cooling body to change the distance between the lower end of the cooling body and the liquid level of the silicon melt.

In the single crystal growing apparatus, assuming that the body portion is pulled up in the order of three regions of a top region, a middle region, and a bottom region, the cooling body control unit uses the cooling body and the silicon while pulling up the middle region. The cooling body is moved up and down so that the distance of the melt from the liquid surface is smaller than the distance at the start of pulling up the body portion and the distance at the end of pulling up the body portion. It is preferable to control.

Assuming that the diameter of the silicon single crystal to be grown in the single crystal growing device is D, the cooling body control unit has a difference Hd between the highest position and the lowest position of the cooling body of 0.1 × D. <It is preferable that the cooling body is configured to move up and down so as to satisfy Hd.

In the single crystal growing apparatus, the cooling body control unit lowers the cooling body at a pulling rate of 20% to 30% of the body portion, and raises the cooling body at a pulling rate of 70% to 90% of the body portion. It is preferable to raise and lower the cooling body so as to cause the cooling.

In the single crystal growing apparatus, the cooling body is divided into two in the vertical direction, and it is preferable to raise and lower only the lower cooling body.

It is the schematic sectional drawing of the single crystal growth apparatus which concerns on embodiment of this invention. It is an enlarged cross-sectional view of the single crystal growth apparatus around the silicon single crystal to be grown. It is a figure which shows the general relationship between V / G and the type and distribution of a crystal defect. It is a flowchart which shows the process of the single crystal growth method which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the relationship between the pull-up rate of the body part in the comparative example, and the distance between the 2nd cooling body and the liquid level of a silicon melt. It is a schematic diagram for demonstrating the relationship between the pull-up rate of the body part in an Example, and the distance between the 2nd cooling body and the liquid level of a silicon melt.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[Single crystal growing device]
FIG. 1 is a schematic cross-sectional view of the single crystal growing apparatus 1 according to the embodiment of the present invention.
The single crystal growing device 1 is a device that pulls up and grows a silicon single crystal S by the Czochralski method. As shown in FIG. 1, the single crystal growing device 1 has a water-cooled chamber 2 constituting an outer shell, a crucible 3 arranged in the center of the chamber 2, a rotating shaft 4 for supporting the crucible 3, and rotation. It includes a shaft drive mechanism 5 for rotating and raising and lowering the shaft 4, a heater 6, a heat shield 7 arranged above the crucible 3, and a control device 8.
Further, the single crystal growing device 1 is installed so as to surround the silicon single crystal S to be grown, and is a cylindrical cooling body 12 (for promoting cooling of the silicon single crystal S from the outer peripheral side of the silicon single crystal S). Water-cooled body).

The chamber 2 is composed of a main chamber 10 and a cylindrical pull chamber 11 connected to an upper opening 10A of the main chamber 10. The crucible 3, the heater 6, the heat shield 7, and the cooler 12 are arranged in the main chamber 10.

The crucible 3 is a container that has a circular shape when viewed from above in the vertical direction and stores the silicon melt M. The crucible 3 has a double structure composed of an inner quartz crucible 3A and an outer graphite crucible 3B. The crucible 3 is fixed to the upper end of a rotating shaft 4 that can rotate and move up and down and extends in the vertical direction. The lower end of the rotating shaft 4 penetrates the bottom of the chamber 2 and is connected to a shaft drive mechanism 5 provided on the outside of the chamber 2.

The heater 6 is a heating device that heats the silicon melt M in the crucible 3. The heater 6 has a cylindrical shape and is arranged on the outer peripheral side of the crucible 3. The heater 6 is a resistance heating type so-called carbon heater. A heat insulating material 9 is provided on the outside of the heater 6 along the inner surface of the chamber 2.

Above the crucible 3, a wire 16 which is a pulling shaft of a silicon single crystal and a wire winding mechanism 17 for winding the wire 16 are provided. The wire winding mechanism 17 has a function of rotating the silicon single crystal S together with the wire 16.
The wire winding mechanism 17 is controlled by the control device 8. The wire winding mechanism 17 is arranged above the pull chamber 11. The wire 16 extends downward from the wire winding mechanism 17 through the inside of the pull chamber 11, and the tip end portion of the wire 16 reaches the internal space of the main chamber 10.
FIG. 1 shows a state in which the silicon single crystal S being grown is suspended from the wire 16. When the silicon single crystal S is pulled up, the silicon single crystal S is grown by gradually pulling up the wire 16 while rotating the crucible 3 and the silicon single crystal S, respectively.

The heat shield 7 has a tubular shape and surrounds the silicon single crystal S being grown above the silicon melt M in the crucible 3.
The heat shield 7 suppresses the temperature fluctuation of the silicon melt M to form an appropriate thermal environment near the crystal growth interface, and prevents the silicon single crystal S from being heated by the radiant heat from the heater 6 and the rutsubo 3. It is provided in. The heat shield 7 is a member made of graphite having a substantially cylindrical shape, and is provided so as to cover the region above the silicon melt M excluding the pulling path of the silicon single crystal S.

The pull chamber 11 is provided with a gas introduction port 14. The gas introduction port 14 introduces an inert gas such as argon gas into the chamber 2. An exhaust port 15 is provided in the lower part of the main chamber 10. The exhaust port 15 sucks and discharges the gas in the chamber 2 by driving a vacuum pump (not shown). The inert gas introduced into the chamber 2 from the gas introduction port 14 descends between the growing silicon single crystal S and the heat shield 7. Next, the inert gas passes through the gap between the lower end of the heat shield 7 and the liquid surface of the silicon melt M, and then flows toward the outside of the heat shield 7 and further toward the outside of the crucible 3. After that, the inert gas descends outside the crucible 3 and is discharged from the exhaust port 15.

The cooling body 12 forcibly cools the silicon single crystal S with a cooling liquid such as water flowing inside. The cooling body 12 is made of a metal having good thermal conductivity such as copper, and the inner surface side can be blackened and the outer surface side can be chrome-plated in order to increase the endothermic efficiency.

The cooling body 12 plays a role of controlling the temperature gradient G in the crystal in the pulling axial direction of the central portion of the single crystal and the outer peripheral portion of the single crystal by promoting the cooling of the silicon single crystal S during growth. Since the cooling body 12 takes heat from the outer peripheral portion of the silicon single crystal S, the outer peripheral portion of the silicon single crystal S faces the silicon single crystal S and the cooling body 12 in the outer peripheral portion of the silicon single crystal S rather than the central portion of the silicon single crystal S. Strongly influenced by 12. On the other hand, in the portion where the silicon single crystal S and the cooling body 12 do not face each other, the central portion of the silicon single crystal S is relatively more affected by the cooling body 12 than the outer peripheral portion of the silicon single crystal S. Therefore, by moving the cooling body 12 away from or closer to the crystal growth interface, it is possible to change the intracrystal radial distribution of the intracrystal temperature gradient G in the pulling axis direction in the vicinity of the crystal growth interface.

The cooling body 12 is arranged on the outer peripheral side of the silicon single crystal S to be grown so as to surround the pulling path of the silicon single crystal S.
The cooling body 12 is composed of a first cooling body 12A connected to the upper opening 10A of the main chamber 10 and a second cooling body 12B arranged below the first cooling body 12A and capable of raising and lowering. That is, the cooling body 12 of the present embodiment is divided into two in the vertical direction, and only the lower second cooling body 12B is moved up and down.

By dividing the cooling body 12 into two in the vertical direction and raising and lowering only the lower second cooling body 12B, even a lifting mechanism having a low lifting load capacity (for example, a small lifting mechanism of a motor) can raise and lower the second cooling body. Since 12B can be raised and lowered, the raising and lowering mechanism can be made compact. Further, the lower second cooling body 12B is arranged near the crystal growth interface from the melting point to 1300 ° C., which strongly affects the type and distribution of crystal defects in the silicon single crystal. Therefore, moving only the second cooling body 12B up and down to move it away from or closer to the crystal growth interface is the distribution of the temperature gradient G within the cross section (intra-crystal radial direction) of the silicon single crystal orthogonal to the pull-up axis direction. It is efficient in controlling the defect distribution in the cross section (radial direction in the crystal).
The distance between the grown silicon single crystal S and the cooling body 12 is preferably small, and is appropriately determined in consideration of the diameter margin of the silicon single crystal S.

FIG. 2 is an enlarged cross-sectional view of the periphery of the grown silicon single crystal S. As shown in FIG. 2, assuming that the diameter of the silicon single crystal S grown by the single crystal growing device 1 is D and the inner diameters of the first cooling body 12A and the second cooling body 12B are IDs, the first cooling body 12A and The second cooling body 12B is formed so that the inner diameter ID is 1.05 × D or more and 1.3 × D or less. For example, the diameter D of the grown silicon single crystal S can be 310 mm, and the inner diameter ID of the cooling body 12 can be 350 mm. The inner diameters of the first cooling body 12A and the second cooling body 12B do not have to be the same.

The second cooling body 12B can be moved in the vertical direction by an elevating mechanism (not shown). The elevating mechanism of the second cooling body 12B is controlled by the cooling body control unit 8A of the control device 8.
The second cooling body 12B can move up and down between a position as close as possible to the first cooling body 12A (upper end) and a position as close as possible to the liquid level MA of the silicon melt M (lower end). By raising and lowering the second cooling body 12B, the portion of the silicon single crystal S that promotes cooling can be changed.
The elevating mechanism for the second cooling body 12B can be composed of, for example, a mechanism including a rack, a pinion, and a motor, a linear motion cylinder, and the like.

The control device 8 controls the shaft drive mechanism 5 so that the distance G1 (gap) between the liquid level MA of the silicon melt M and the lower end of the heat shield 7 is constant, and raises the crucible 3. That is, the distance G1 is kept constant even if the amount of the silicon melt M in the crucible 3 decreases as the silicon single crystal S grows.
As a result, it is possible to suppress the temperature fluctuation of the silicon melt M and control the evaporation amount of the dopant from the silicon melt M by keeping the flow velocity of the inert gas flowing near the liquid surface MA constant. Therefore, it is possible to improve the stability of the crystal defect distribution, the oxygen concentration distribution, the resistivity distribution, etc. in the pull-up axial direction of the silicon single crystal S.

Assuming that the height of the first cooling body 12A is H1, the first cooling body 12A is formed so that 0.9 × D <H1 <1.5 × D. Similarly, assuming that the height of the second cooling body 12B is H2, the second cooling body 12B is formed so that 0.9 × D <H2 <1.5 × D.
The height H2 of the second cooling body 12B is preferably smaller than the height H1 of the first cooling body 12A.
Further, the first cooling body 12A and the second cooling body 12B are preferably formed so that 2 × G1 <ST <4 × G1 when the vertical stroke of the second cooling body 12B is ST. .. In other words, in the first cooling body 12A and the second cooling body 12B, when the second cooling body 12B is at the highest position, the distance between the lower end of the second cooling body 12B and the liquid level MA is less than 2 × G1. It is formed so as to be larger than 4 × G1.

Specifically, when the gap G1 is 80 mm and the diameter of the grown silicon single crystal S is 310 mm, the heights of the first cooling body 12A and the second cooling body 12B are preferably about 350 mm. The inner diameters of the first cooling body 12A and the second cooling body 12B are preferably about 350 mm, and the stroke ST of the second cooling body 12B is preferably about 200 mm.

[Relationship between the ratio V / G of the crystal pulling speed V and the temperature gradient G in the crystal and the crystal quality]
Next, the relationship between the ratio V / G of the crystal pulling speed V and the temperature gradient G in the crystal and the crystal quality will be described.
Since the type and distribution of crystal defects contained in the silicon single crystal S depend on the ratio V / G of the crystal pulling rate V and the intra-crystal temperature gradient G, it is necessary to control the crystal quality in the silicon single crystal S. It is necessary to control V / G.

FIG. 3 is a vertical cross-sectional view of the silicon single crystal S, showing a general relationship between V / G and the type and distribution of crystal defects.
As shown in FIG. 3, when the V / G is large, the pores become excessive, and void defects (COP), which are aggregates of the pores, occur. On the other hand, when the V / G is small, the interstitial silicon atoms become excessive, and dislocation clusters due to the aggregates of interstitial silicon are generated. Further, between the region where COP is generated and the region where dislocation clusters are generated, there are three regions, an OSF region, a Pv region, and a Pi region, in descending order of V / G. In order to say that the silicon single crystal is a defect-free crystal, it is necessary that the entire cross section of the silicon single crystal orthogonal to the pulling axis direction is a defect-free region. Here, the “defect-free region” refers to a region that does not contain the COP and dislocation clusters of the Green-in defect. Further, among the defect-free crystals, a single crystal in which the OSF ring is not generated after the evaluation heat treatment and is composed of only the Pv region or the Pi region is regarded as a more complete defect-free crystal. The present invention is effective not only for producing a defect-free crystal but also for producing a more complete defect-free crystal composed of only a Pv region or a Pi region.

In order to control the crystal pulling speed V and grow a defect-free crystal with a high yield, the thermal environment surrounding the single crystal being pulled so as to make the PvPi margin as wide as possible using the PvPi margin (pulling speed margin) as an index. It is preferable to control.
Here, the PvPi margin means a permissible range of the crystal pulling speed V in which an arbitrary region in the silicon single crystal S can be a Pv region or a Pi region in a broad sense, but in a narrow sense, a pulling shaft. It refers to the minimum value (PvPi in-plane margin) of the PvPi margin in the cross section of the silicon single crystal orthogonal to the direction. Normally, the intra-crystal temperature gradient G does not change significantly, so the PvPi margin is substantially proportional to the width of V / G from the Pv-OSF boundary to the Pi-dislocation cluster boundary in FIG.

The diameter of the silicon single crystal S is mainly controlled by adjusting the pulling speed V, and the crystal pulling speed V is appropriately changed in order to suppress the diameter fluctuation, and is about 0.015 mm / min during the crystal pulling process. Speed fluctuations are occurring. That is, since the fluctuation of the pulling speed V cannot be completely eliminated, a pulling speed margin that allows a speed fluctuation of about 0.015 mm / min is required.

The width of the PvPi margin is affected by the staying time in the temperature range of 600 ± 200 ° C. in addition to the temperature gradient near the melting point, and the shorter the staying time in the temperature range, the wider the PvPi margin. Therefore, in the present embodiment, the silicon single crystal S is rapidly cooled to shorten the residence time in the temperature range of 600 ± 200 ° C., and the distribution of the temperature gradient G in the crystal in the pulling axial direction near the melting point is made uniform to make PvPi. The in-plane margin will be expanded to improve the manufacturing yield of defect-free crystals.

The temperature of the silicon single crystal S pulled up from the silicon melt M decreases as the distance from the liquid level MA of the silicon melt M decreases, and the silicon single crystal S passes through the temperature range of 600 ± 200 ° C. in the cooling process. When the silicon single crystal S quickly passes through the temperature range of 600 ± 200 ° C., the aggregation of pores can be suppressed and the PvPi margin can be widened. How short the staying time in the temperature range of 600 ± 200 ° C. and how wide the PvPi margin is can be obtained from the point defect numerical analysis for analyzing the diffusion / pair annihilation of pores and interstitial silicon. As described above, if the PvPi margin is widened, the crystal pulling speed V can be easily controlled, so that defect-free crystals can be stably grown.

[Effect of Embodiment]
In the single crystal growing apparatus 1 of the present embodiment, the staying time in the temperature range of 600 ± 200 ° C. is shortened by the first cooling body 12A. Further, by moving the second cooling body 12B to optimize the thermal environment in the furnace surrounding the crystal, particularly the thermal environment near the crystal growth interface, the crystal in the cross section of the silicon single crystal orthogonal to the pulling axis direction. The distribution of the internal temperature gradient G can be made uniform, the PvPi margin can be expanded, and the production yield of defect-free crystals can be increased.

When the thermal environment near the crystal growth interface changes due to the movement of the second cooling body 12B, the shape of the crystal growth interface also changes, so that the movement of the second cooling body 12B affects the distribution of the temperature gradient G in the crystal. Is complicated. Therefore, in order to make the temperature gradient G in the crystal uniform, a means such as an experiment or a numerical simulation is effective.
Hereinafter, a single crystal growth method including a specific control method for the second cooling body 12B will be described.

FIG. 4 is a flowchart showing a single crystal growing method according to the present embodiment. Further, FIGS. 5 and 6 are schematic views for explaining the relationship between the pulling rate of the body portion of the silicon single crystal S and the position of the second cooling body 12B.
Here, the pull-up rate of the body portion is defined as a position in the crystal longitudinal direction defined as a preset length of the body portion as 100% and a start position of the body portion as 0% in the production of a single crystal. is there. Normally, when the single crystal is normally grown without any trouble on the device and without dislocation of the single crystal, the length of the grown body portion becomes the same as the preset length of the body portion. ..

As shown in FIG. 4, in the single crystal growing method of the present embodiment, the raw material melting step P1 for producing the silicon melt M by heating the silicon raw material in the rutsubo 3 with the heater 6 and melting the silicon raw material, and the wire 16 A single crystal is grown by gradually pulling up the seed crystal while maintaining the contact state between the liquid landing step P2 in which the seed crystal attached to the tip is lowered and landed on the silicon melt M and the silicon melt M. It has a pulling step (P3 to P5).

In the pulling step, the shoulder part pulling step P3 for forming the shoulder part S1 which is a diameter-expanded part whose crystal diameter gradually increases as the crystal grows, and the body part which is a constant diameter part maintained at a specified crystal diameter of 300 mm or more. The body portion pulling step P4A for forming S2 and the tail portion pulling step P5 for forming the tail portion S3, which is a reduced diameter portion whose crystal diameter gradually decreases with crystal growth, are sequentially carried out.
Further, in the single crystal growing method of the present embodiment, the second cooling body 12B is raised and lowered during the execution of the body portion pulling step P4A, and the lower end of the second cooling body 12B and the liquid level MA of the silicon melt M are brought into contact with each other. It has a cooling body elevating step P4B that changes the distance.

In the present invention, as shown in FIGS. 5 and 6, the body portion S2 has a top region R1 (pull-up rate 0% to 33%) and a middle region R2 (pull-up rate 33% to 33%) in this order from above the body portion S2. Three regions are defined: 67%) and bottom region R3 (raising rate 67% to 100%). The three regions divide the body portion S2 into three substantially evenly. In the body portion pulling step P4A, the body portion S2 is pulled up in the order of the top region R1, the middle region R2, and the bottom region R3.

As described above, in the single crystal growing method of the present embodiment, the second cooling body 12B is moved in the vertical direction. Specifically, in the cooling body control unit 8A of the control device 8, the distance G2 during the pulling up of the middle region R2 is at the start of pulling up the body portion S2 (the pulling rate of the body portion S2 is 0%, see FIGS. 5 and 6). ), The second cooling body 12B is moved up and down so as to be smaller than the distance G2 at the end of pulling up the body portion S2 (the pulling rate of the body portion S2 is 100%). The distance G2 is the distance between the lower end of the second cooling body 12B and the liquid level MA of the silicon melt M.
That is, in the single crystal growing method of the present embodiment, the second cooling body 12B is temporarily placed between the liquid level MA of the silicon melt M (between the silicon single crystal S and the silicon melt M) while the body portion S2 is being pulled up. Close to the solid-liquid interface).

Further, the cooling body control unit 8A of the control device 8 raises and lowers the second cooling body 12B so that the difference Hd between the highest position and the lowest position of the second cooling body 12B satisfies 0.1 × D <Hd. Let me.

Next, the details of the elevating control of the second cooling body 12B will be described with reference to the schematic views shown in FIGS. 5 and 6. FIG. 5 shows a comparative example, and FIG. 6 shows an embodiment. In the comparative example shown in FIG. 5, the distance G2 (see FIG. 2) between the lower end of the second cooling body 12B and the liquid level MA of the silicon melt M is constant, and in the embodiment shown in FIG. 6, the distance G2 is changed. ing.

In FIGS. 5 and 6, the upper part is a vertical cross-sectional view of the silicon single crystal S, and a diagram explaining the relationship between V / G and the type and distribution of crystal defects is shown in the top region R1, the middle region R2, and the bottom. Each of the regions R3 is shown.
The lower part shows a graph explaining the position of the second cooling body 12B. In the graph, the horizontal axis is the pull-up rate of the body portion S2, and the vertical axis is the distance G2 between the lower end of the second cooling body 12B and the liquid level MA of the silicon melt M.

As shown in FIG. 5, when the distance G2 is constant, the in-plane distribution of crystal defects cannot be maintained constant. That is, the in-plane distribution of crystal defects is different in the top region R1, middle region R2, and bottom region R3 of the body portion S2 of the silicon single crystal S, and a desired PvPi margin can be secured in the middle region R2 of the body portion S2. However, a desired PvPi margin cannot be secured in the top region R1 and the bottom region R3 of the body portion S2.

The PvPi region between the OSF region and the dislocation cluster region of the top region R1 in FIG. 5 is displaced in the higher V / G direction at the outer peripheral portion of the crystal than at the central portion of the crystal. Therefore, in order to obtain a defect distribution similar to that of the middle region R2 and secure a desired PvPi margin, the second cooling body 12B is moved up and down in the crystal in the cross section of the silicon single crystal orthogonal to the pulling axial direction. It is necessary to make the distribution of the temperature gradient G uniform.

On the other hand, in the method of pulling up the silicon single crystal S of the present embodiment, as shown in FIG. 6, the second cooling body 12B is moved up and down so that the distance G2 changes.
Specifically, the PvPi region in the top region R1 of the conventional example shown in FIG. 5 has a distribution similar to that of the middle region R2, and the cooling of the crystal center portion is relaxed in order to secure a desired PvPi margin. 2 The cooling body 12B is raised to move it away from the crystal growth interface. Further, in order to make the PvPi region in the bottom region R3 of the conventional example similar to that in the middle region R2, the second cooling body 12B is raised so as to relax the cooling of the crystal center portion and kept away from the crystal growth interface.

That is, the cooling body control unit 8A of the control device 8 controls the second cooling body 12B so that the second cooling body 12B comes closest to the liquid level MA while the middle region R2 is being pulled up.
More specifically, the cooling body control unit 8A of the present embodiment has a second cooling body so that the distance G2 is about 220 mm from the start of pulling up the body portion S2 (starting position of the body portion) to the pulling up of the top region R1. Control 12B.

Next, at the timing when the body portion S2 is pulled up by about 20%, the second cooling body 12B is lowered so that the distance G2 becomes 212 mm from the position (distance G2 = 220 mm) at the start of pulling up the body portion S2.
After that, in the middle region R2, the distance G2 is kept at 212 mm, and at the timing when the body portion S2 is raised by about 80%, the second cooling body 12B is raised so that the distance G2 becomes 252 mm. After that, the distance G2 is kept at 252 mm until the end of pulling up the body portion S2.

The timing for lowering the second cooling body 12B is preferably a pull-up rate of 20% to 30% (20% or more and 30% or less). The timing for raising the second cooling body 12B is preferably a pulling rate of 70% to 90% (70% or more and 90% or less).

By controlling the second cooling body 12B in this way, the temperature gradient G in the crystal is optimized, and as shown in the vertical cross-sectional view of the silicon single crystal S in the upper part of FIG. 6, the top region R1 of the body portion S2 It is possible to maintain a constant in-plane distribution of crystal defects from to the bottom region R3 and increase the production yield of defect-free crystals.

Further, the cooling body 12 is divided into two in the vertical direction, and only the lower second cooling body 12B is moved up and down, so that the lifting device can be made compact.

The control method of the second cooling body 12B is an example, and the distance G2 during the pulling up of the middle region R2 is the distance G2 at the start of pulling up the body portion S2 and the distance at the end of pulling up the body portion S2. It is not limited to this if the second cooling body 12B is moved up and down so as to be smaller than G2. For example, the distance G2 at the start of pulling may be larger than the distance G2 at the end of pulling.

Regarding how much the cooling body is raised and lowered, the relationship between the defect distribution and the distance G2 as shown in the upper part of FIG. 5 or FIG. 6, or the relationship between the PvPi margin and the distance G2 is determined in the longitudinal direction of the crystal ( It can be grasped over a crystal pulling rate of 0% to 100%) and determined based on the relationship. Further, in grasping the relationship between the defect distribution and the distance G2 as shown in the upper part of FIG. 5 or FIG. 6, or the relationship between the PvPi margin and the distance G2, a single crystal pulling experiment in which the distance G2 was variously changed or It can be grasped by defect simulation by computer.

Further, in the above embodiment, the cooling body 12 is divided into two in the vertical direction, but a single cooling body 12 may be moved up and down.
In that case, the lower limit of the elevating range of the cooling body 12 can be set to a position where the lower end of the cooling body 12 is at the same height as the lower end of the heat shield 7, and the upper limit of the elevating range of the cooling body 12 is the cooling body. The lower end of the 12 can be positioned at the same height as the upper opening 10A of the main chamber 10.
When the lower end of the cooling body 12 is located below the lower end of the heat shield 7, it is the same as changing the distance G1 (gap) between the liquid level MA of the silicon melt M and the lower end of the heat shield 7. Since the effect is produced, the production of a defect-free single crystal is rather difficult. When the lower end of the cooling body 12 is located above the upper opening 10A, the cooling body 12 is stored in the pull chamber 11, and the effect of raising and lowering the cooling body 12 cannot be obtained.

1 ... Lifting device, 2 ... Chamber, 3 ... Crucible, 4 ... Rotating shaft, 5 ... Shaft drive mechanism, 6 ... Heater, 7 ... Heat shield, 8 ... Control device, 12 ... Cooler, S ... Silicon single crystal, S2 ... Body part.

Claims (10)

A single crystal growing method for growing a silicon single crystal consisting of a shoulder portion, a body portion, and a tail portion by the Czochralski method.
A pulling step of pulling up the body portion of the silicon single crystal and
During the execution of the pulling step, a cooling body installed so as to surround the silicon single crystal and promoting cooling of the silicon single crystal is moved up and down from the outer peripheral side of the silicon single crystal to the lower end of the cooling body. A single crystal growing method characterized by having a cooling body elevating step for changing the distance of a silicon melt from the liquid surface. In the cooling body elevating step
The single crystal growing method according to claim 1, wherein the cooling body is lowered from the position at the start of pulling up the body portion. In the cooling body elevating step
The single crystal growing method according to claim 2, wherein the cooling body is lowered from the position at the start of pulling up the body portion and then raised. In the pulling step, the body portion is pulled up in the order of three regions, a top region, a middle region, and a bottom region.
In the cooling body elevating step, the cooling body is set so that the distance during the pulling up of the middle region is smaller than the distance at the start of pulling up the body portion and the distance at the end of pulling up the body portion. The single crystal growing method according to claim 3, wherein the single crystal is raised and lowered. In the cooling body elevating step, the cooling body is lowered at a pulling rate of 20% to 30% of the body portion, and the cooling body is raised at a pulling rate of 70% to 90% of the body portion. Item 4. The single crystal growing method according to Item 4. A single crystal growing device that grows a silicon single crystal consisting of a shoulder part, a body part, and a tail part by the Czochralski method.
A crucible that holds the silicone melt,
A cooling body that is installed so as to surround the silicon single crystal, can be raised and lowered, and promotes cooling of the silicon single crystal from the outer peripheral side.
A control device for controlling at least the cooling body is provided.
The control device is a single crystal growing device having a cooling body control unit that raises and lowers the cooling body to change the distance between the lower end of the cooling body and the liquid level of the silicon melt. Assuming that the body portion is pulled up in the order of three regions, a top region, a middle region, and a bottom region,
In the cooling body control unit, the distance between the cooling body and the liquid level of the silicon melt during the pulling up of the middle region is the distance at the start of pulling up the body portion and the distance at the end of pulling up the body portion. The single crystal growing apparatus according to claim 6, wherein the cooling body is controlled so as to move the cooling body up and down so as to be smaller than the distance. Assuming that the diameter of the silicon single crystal to be grown is D, the cooling body control unit performs the cooling body control unit so that the difference Hd between the highest position and the lowest position of the cooling body satisfies 0.1 × D <Hd. The single crystal growing apparatus according to claim 7, wherein the cooling body is configured to move up and down. The cooling body control unit lowers the cooling body at a pulling rate of 20% to 30% of the body portion, and raises the cooling body at a pulling rate of 70% to 90% of the body portion. The single crystal growing apparatus according to claim 7 or 8, wherein the single crystal growing apparatus is moved up and down. The single crystal growing apparatus according to any one of claims 6 to 9, wherein the cooling body is divided into two in the vertical direction, and only the lower cooling body is moved up and down.

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