WO2017159028A1 - シリコン単結晶の製造方法 - Google Patents
シリコン単結晶の製造方法 Download PDFInfo
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- WO2017159028A1 WO2017159028A1 PCT/JP2017/001493 JP2017001493W WO2017159028A1 WO 2017159028 A1 WO2017159028 A1 WO 2017159028A1 JP 2017001493 W JP2017001493 W JP 2017001493W WO 2017159028 A1 WO2017159028 A1 WO 2017159028A1
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- single crystal
- silicon
- tail
- silicon single
- melt
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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
- C30B15/22—Stabilisation or shape controlling of the molten zone near the pulled crystal; Controlling the section of the crystal
-
- 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
-
- 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
- C30B15/14—Heating of the melt or the crystallised materials
-
- 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
-
- 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
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
Definitions
- the present invention relates to a method for producing a silicon single crystal by the Czochralski method (hereinafter referred to as CZ method), and particularly to a method for growing a tail portion of a silicon single crystal ingot.
- Epitaxial silicon wafers are widely used as substrate materials for semiconductor devices.
- An epitaxial silicon wafer is obtained by forming an epitaxial layer on the surface of a bulk silicon substrate, and has high crystal perfection. Therefore, it is possible to manufacture a semiconductor device with high quality and high reliability.
- the silicon single crystal used as the substrate material for the epitaxial silicon wafer is manufactured by the CZ method.
- a quartz crucible is filled with a raw material such as polycrystalline silicon, and the silicon raw material is heated and melted in a chamber.
- the seed crystal attached to the lower end of the pulling shaft is lowered from above the quartz crucible and brought into contact with the silicon melt, and the seed crystal is gradually raised while rotating the seed crystal and the quartz crucible.
- a single crystal having a large diameter is grown below the substrate.
- Patent Document 1 As a method for producing an epitaxial silicon wafer, for example, in Patent Document 1, when pulling up a silicon single crystal ingot, a temperature range of 1030 to 920 ° C. during the pulling is set at a cooling rate of 1.0 ° C./min or more, and then 920 to It describes that after growing a silicon single crystal grown in a temperature region of 720 ° C. at a cooling rate of 0.5 ° C./min or less, an epitaxial layer is formed on the surface of the wafer cut out from the single crystal.
- OSF Oxygen ⁇ ⁇ ⁇ induced Stacking Fault: Oxygen-induced stacking fault
- nuclei easily pass through the temperature range (1030 ⁇ 920 ° C) to make the OSF nucleus size very small, thereby reducing the OSF-induced epitaxial defects (below) , Referred to as epi defects).
- a necking process that narrows the crystal diameter by the dash neck method
- a shoulder growth process that gradually increases the crystal diameter
- crystal growth while maintaining the crystal diameter constant A body part growing process to be advanced and a tail part growing process for gradually reducing the crystal diameter to form a conical tail part are sequentially performed.
- the thermal balance between the melt and the single crystal existing at the crystal growth interface is disrupted, and a sudden thermal shock is applied to the crystal, resulting in quality abnormalities such as slip dislocations and oxygen precipitation abnormalities. This is a process necessary for separating the single crystal from the melt while preventing this.
- Patent Document 2 discloses a relatively constant speed in which the lifting speed of the terminal cone part (tail part) of the ingot is equal to the lifting speed of the second half of the main body part (body part) of the ingot. And, if necessary, increase the power (heat amount) supplied to the heater, or decrease the crystal rotation speed and crucible rotation speed to produce a single crystal silicon ingot with a uniform thermal history It is described.
- JP 2010-30856 A Japanese Patent Laid-Open No. 10-95698
- Patent Document 1 a single crystal pulling apparatus equipped with a water-cooled body is used to control the pulling speed during single crystal growth and the temperature gradient in the pulling axis direction of the single crystal immediately after crystallization.
- the portion used as the substrate material of the epitaxial silicon wafer is a body portion (straight barrel portion) in which the crystal diameter is kept constant, and the tail portion is a portion that is not used as a wafer product. Therefore, Patent Document 1 describes cooling conditions for the body portion, but does not describe specific pulling conditions such as the pulling speed at the tail portion, the heater power, and the single crystal rotation speed.
- the tail growth it is common to increase the single crystal pulling speed to gradually reduce the crystal diameter. This is because tail drawing can be easily performed by increasing the pulling rate of the single crystal, and the tail part growing period is shortened, leading to reduction in manufacturing cost. Further, as described above, the tail portion is a portion that does not become a wafer product, and it does not matter if the crystal quality of the tail portion itself is lowered by increasing the pulling speed. For this reason, in the conventional general tail part growing process, control for increasing the pulling speed of the single crystal is performed, and it is considered that the condition that the tail can be easily narrowed is also adopted in Patent Document 1. It is done.
- Patent Document 2 describes that the pulling speed of the tail part is maintained at a relatively constant speed equivalent to the pulling speed of the latter half of the body part.
- the control for keeping the tail pulling speed constant seems to have a relatively constant cooling rate and residence time over the entire body of the single crystal.
- the pulling speed of the tail is the same as that of the body, the pulling speed of the single crystal is slower than the conventional tail growing process.
- the time for which the single crystal stays in the OSF nucleation temperature region is actually increased, which may increase epi defects.
- the crystal diameter gradually decreases, so that the distance D between the heat shield 17 and the silicon single crystal 3 increases as shown in FIG. 8, and the heat from the silicon melt 2 or the like is indicated by a white arrow.
- the periphery of the silicon single crystal 3 immediately after crystallization diffuses upward and the temperature rises.
- the influence of the high temperature around the silicon single crystal 3 is further increased. That is, the time during which the silicon single crystal 3 pulled up from the silicon melt 2 stays in the OSF nucleation temperature region is further increased, and the epi defects are increased.
- the tail portion 3d is likely to undergo dislocation because the crystal diameter decreases and the state of pulling up the crystal changes every moment. Furthermore, since the amount of melt in the crucible is small and the melt is held at the bottom of the crucible in the tail portion growing step, the state of the melt in the crucible changes momentarily as the tail portion 3d is pulled up, causing dislocation. Cheap. For this reason, when the tail portion 3d is lifted at the same speed as the body portion 3c, the time required to complete the lifting of the tail portion 3d becomes very long, and there is a problem that the risk of dislocation in the tail portion 3d increases. is there.
- the object of the present invention is to prevent the occurrence of epi defects when used as a substrate material for an epitaxial silicon wafer while preventing a decrease in the rate of single crystallization due to crystal bends or separation from the melt.
- Another object of the present invention is to provide a method for manufacturing a silicon single crystal.
- a method for producing a silicon single crystal according to the present invention is a method for producing a silicon single crystal by the Czochralski method of pulling up a silicon single crystal from a silicon melt in a quartz crucible, wherein the crystal diameter is constant.
- the silicon single crystal pulled up from the silicon melt is cooled using a water-cooled body disposed on the inner side of the thermal shield, and in the tail part growing step, from the start of growing the tail part
- the silicon single crystal is pulled up at the same pulling speed as that at the end of the body part growth until the end.
- the crystal diameter gradually decreases, so that the lateral gap between the heat shield and the single crystal gradually widens, and the heat shielded by the heat shield diffuses upward, and silicon The single crystal becomes difficult to be cooled.
- the gap between the heat shield and the melt surface is gradually widened due to a decrease in the melt surface.
- the radiant heat from the quartz crucible is more easily diffused upward. Therefore, the crystal quality of the body part near the tail part is different from the crystal quality on the top side under the influence of heat.
- the residence time in the temperature range of 1020 to 980 ° C. becomes longer and becomes gradually cooled, resulting in a crystal containing large OSF nuclei that easily cause epi defects.
- the water-cooled body is provided around the pulling path above the heat shield, so that the silicon single crystal immediately after crystallization is subjected to the OSF nucleation temperature without increasing the pulling speed of the single crystal.
- the period of staying in the area can be shortened. Therefore, it is possible to manufacture a silicon single crystal that can prevent the crystal bend and the decrease in the single crystallization rate due to the crystal being separated from the melt, and can suppress the generation of epi defects during the formation of the epitaxial layer.
- the temperature range from 1020 ° C. to 980 ° C. of the body part of the silicon single crystal is passed within 15 minutes.
- the silicon single crystal pulled up from the silicon melt quickly passes through the OSF nucleation temperature region, so that the size of the OSF nuclei in the silicon single crystal can be reduced. Therefore, when an epitaxial layer is formed on the surface of the silicon wafer cut out from the single crystal ingot, the occurrence of epi defects due to OSF can be suppressed.
- the power of the heater for heating the silicon melt is gradually increased from the start to the end of the tail portion growth, and the power of the heater at the end of the tail portion growth is increased. It is preferable to set the power of the heater at 1.1 times or more and 1.5 times or less at the time of starting the tail part. According to this, it is possible to realize tail tailing while preventing crystal bending and separation of the single crystal from the silicon melt.
- the quartz crucible is raised so that the distance between the thermal shield and the silicon melt is constant.
- the rotation speed of the quartz crucible or the silicon single crystal it is preferable to keep the rotation speed of the quartz crucible or the silicon single crystal constant, and it is also preferable to apply a magnetic field to the silicon melt.
- the amount of melt in the quartz crucible is small and the melt is held at the bottom of the crucible, so that the melt is easily affected by changes in the rotation speed of the quartz crucible and the state of the melt is not good. Since it is stable, the melt state can be stabilized by maintaining the rotation speed constant, and the risk of dislocations in the silicon single crystal can be reduced.
- the melt state is stabilized in the tail growth process, and the dislocation of the silicon single crystal is achieved. The risk of conversion can be reduced.
- the rotation speeds of the quartz crucible and the silicon single crystal need only be substantially constant, and fluctuations within ⁇ 2 rpm are acceptable.
- silicon that can suppress the occurrence of epi defects when used as a substrate material for an epitaxial silicon wafer while preventing a decrease in the rate of single crystallization due to crystal bending or separation from the melt.
- a method for producing a single crystal can be provided.
- FIG. 1 is a side sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to a first embodiment of the present invention.
- FIG. 2 is a flowchart for explaining a method of manufacturing a silicon single crystal according to an embodiment of the present invention.
- FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
- FIG. 4 is a schematic cross-sectional view showing a single crystal pulling state during the tail portion growing step.
- FIG. 5 is a sequence diagram showing changes in the pulling rate and heater power of the single crystal.
- FIG. 6 is a side sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to the second embodiment of the present invention.
- FIG. 1 is a side sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to a first embodiment of the present invention.
- FIG. 2 is a flowchart for explaining a method of manufacturing a silicon single crystal according to an embodiment of the present invention.
- FIG. 3 is
- FIG. 7 is a graph showing the relationship between the pulling position of the single crystal and the transit time of the OSF nucleation temperature region (1020 to 980 ° C. region) of the single crystal.
- FIG. 8 is a schematic diagram for explaining a conventional problem in the tail part growing step.
- FIG. 1 is a side sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to a first embodiment of the present invention.
- a single crystal manufacturing apparatus 1A includes a chamber 10, a quartz crucible 11 that holds the silicon melt 2 in the chamber 10, a graphite susceptor 12 that holds the quartz crucible 11, and a susceptor 12.
- a heat insulating member 16 disposed above the quartz crucible 11, a water-cooled body 18 provided inside the heat shielding member 17 and above the lower end of the heat shielding member 17, and a quartz crucible. 11 and a wire 19 for pulling up a single crystal arranged coaxially with the rotating shaft 13 and above the chamber 10. And and a wire winding mechanism 20.
- the single crystal manufacturing apparatus 1A includes a magnetic field generator 21 disposed outside the chamber 10, a CCD camera 22 that captures the inside of the chamber 10, an image processing unit 23 that processes an image captured by the CCD camera 22, A control unit 24 that controls the shaft drive mechanism 14, the heater 15, and the wire winding mechanism 20 based on the output of the image processing unit 23 is provided.
- the chamber 10 is composed of a main chamber 10a and an elongated cylindrical pull chamber 10b connected to the upper opening of the main chamber 10a.
- the quartz crucible 11, the susceptor 12, the heater 15, and the heat shield 17 are composed of the main chamber. 10a.
- the pull chamber 10b is provided with a gas inlet 10c for introducing an inert gas (purge gas) such as argon gas into the chamber 10, and a gas for discharging the inert gas at the lower part of the main chamber 10a.
- a discharge port 10d is provided.
- a viewing window 10e is provided on the upper part of the main chamber 10a, and the growth state (solid-liquid interface) of the silicon single crystal 3 can be observed from the viewing window 10e.
- the quartz crucible 11 is a quartz glass container having a cylindrical side wall and a curved bottom.
- the susceptor 12 is held in close contact with the outer surface of the quartz crucible 11 so as to wrap the quartz crucible 11.
- the quartz crucible 11 and the susceptor 12 form a double structure crucible that supports the silicon melt in the chamber 10.
- the susceptor 12 is fixed to the upper end portion of the rotary shaft 13 extending in the vertical direction.
- the lower end portion of the rotating shaft 13 passes through the center of the bottom portion of the chamber 10 and is connected to a shaft drive mechanism 14 provided outside the chamber 10.
- the susceptor 12, the rotating shaft 13 and the shaft driving mechanism 14 constitute a rotating mechanism and a lifting mechanism for the quartz crucible 11.
- the heater 15 is used for melting the silicon raw material filled in the quartz crucible 11 to generate the silicon melt 2.
- the heater 15 is a carbon resistance heating heater, and is provided so as to surround the quartz crucible 11 in the susceptor 12. Furthermore, the outside of the heater 15 is surrounded by a heat insulating material 16, thereby improving the heat retaining property in the chamber 10.
- the heat shield 17 suppresses temperature fluctuation of the silicon melt 2 to form an appropriate hot zone near the solid-liquid interface, and prevents the silicon single crystal 3 from being heated by radiant heat from the heater 15 and the quartz crucible 11. It is provided for.
- the heat shield 17 is a graphite member that covers the upper region of the silicon melt 2 excluding the pulling path of the silicon single crystal 3, and has an inverted truncated cone shape whose diameter is reduced from the upper side to the lower side. ing.
- a circular opening 17a larger than the diameter of the silicon single crystal 3 is formed at the center of the lower end of the heat shield 17, and a pulling path for the silicon single crystal 3 is secured. As shown in the figure, the silicon single crystal 3 is pulled upward through the opening 17a.
- the diameter of the opening 17 a of the heat shield 17 is smaller than the diameter of the quartz crucible 11, and the lower end of the heat shield 17 is located inside the quartz crucible 11, so the upper end of the rim of the quartz crucible 11 is the lower end of the heat shield 17.
- the heat shield 17 does not interfere with the quartz crucible 11 even if it is raised further upward.
- the amount of melt in the quartz crucible 11 decreases as the silicon single crystal 3 grows, by raising the quartz crucible 11 so that the distance (gap ⁇ G) between the melt surface and the heat shield 17 becomes constant, It is possible to control the evaporation amount of the dopant from the silicon melt 2 while suppressing the temperature fluctuation of the silicon melt 2 and keeping the flow velocity of the gas flowing in the vicinity of the melt surface (purge gas guiding path) constant. Therefore, the stability of the crystal defect distribution, oxygen concentration distribution, resistivity distribution, etc. in the pulling axis direction of the single crystal can be improved.
- a water-cooled body 18 is disposed above the lower end 17 b of the heat shield 17 and inside the heat shield 17. Like the heat shield 17 and the like, the water-cooled body 18 is provided so as to surround the pulling path of the silicon single crystal 3.
- the water-cooled body 18 is made of a metal having good heat conductivity such as copper, iron, stainless steel (SUS), and molybdenum, and it is preferable that the surface temperature can be maintained from room temperature to about 200 ° C. by passing cooling water through the inside. Although details will be described later, the cooling of the silicon single crystal 3 immediately after crystallization can be promoted by the presence of the water-cooled body 18.
- FIG. 1 shows a state in which the silicon single crystal 3 being grown is suspended from the wire 19.
- the seed crystal is immersed in the silicon melt 2, and the single crystal is grown by gradually pulling up the wire 19 while rotating the quartz crucible 11 and the seed crystal, respectively.
- a gas inlet 10c for introducing an inert gas into the chamber 10 is provided at the top of the pull chamber 10b, and a gas exhaust for exhausting the inert gas in the chamber 10 is provided at the bottom of the main chamber 10a.
- An outlet 10d is provided.
- the inert gas is introduced into the chamber 10 from the gas inlet 10c, and the introduction amount is controlled by a valve. Further, since the inert gas in the sealed chamber 10 is exhausted from the gas outlet 10d to the outside of the chamber 10, the SiO gas and CO gas generated in the chamber 10 are collected to keep the inside of the chamber 10 clean. Is possible.
- a vacuum pump is connected to the gas discharge port 10d through a pipe, and the flow rate is controlled by a valve while sucking an inert gas in the chamber 10 by the vacuum pump. Is kept at a constant reduced pressure.
- the magnetic field generator 21 applies a horizontal magnetic field or a vertical magnetic field to the silicon melt 2.
- a magnetic field By applying a magnetic field to the silicon melt 2, melt convection in a direction perpendicular to the magnetic field lines can be suppressed. Therefore, elution of oxygen from the quartz crucible 11 can be suppressed, and the oxygen concentration in the silicon single crystal can be reduced.
- a viewing window 10e for observing the inside is provided at the upper part of the main chamber 10a, and the CCD camera 22 is installed outside the viewing window 10e.
- the CCD camera 22 takes an image of the boundary portion between the silicon single crystal 3 and the silicon melt 2 that can be seen through the opening 17a of the heat shield 17 from the viewing window 10e.
- the CCD camera 22 is connected to the image processing unit 23, the captured image is processed by the image processing unit 23, and the processing result is used by the control unit 24 to control the lifting conditions.
- FIG. 2 is a flowchart for explaining a method for producing a silicon single crystal according to an embodiment of the present invention.
- FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
- the silicon raw material in the quartz crucible 11 is heated to generate the silicon melt 2 (step S11). Thereafter, the seed crystal attached to the tip end portion of the wire 19 is lowered and deposited on the silicon melt 2 (step S12).
- a single crystal pulling step is performed in which the seed crystal is gradually pulled up and the single crystal is grown while maintaining the contact state with the silicon melt 2.
- a necking step step S13 for forming a neck portion 3a with a narrowed crystal diameter for dislocation elimination, and a shoulder portion in which the crystal diameter gradually increases to obtain a specified diameter.
- a shoulder portion growing step step S14 for forming 3b, a body portion growing step (step S15) for forming a body portion 3c in which the crystal diameter is maintained constant, and a tail portion 3d in which the crystal diameter is gradually reduced is formed.
- step S16 The tail part growing process (step S16) to be performed is sequentially performed, and the tail part growing process is completed by finally separating the single crystal from the melt surface.
- the silicon single crystal ingot 3 having the neck portion 3a, the shoulder portion 3b, the body portion 3c, and the tail portion 3d in order from the upper end (top) to the lower end (bottom) of the single crystal is completed.
- the CCD camera 22 takes an image of the boundary between the silicon single crystal 3 and the silicon melt 2 in order to control the diameter of the silicon single crystal 3 and the liquid surface position of the silicon melt 2.
- the diameter of the single crystal at the solid-liquid interface and the distance between the melt surface and the heat shield 17 (gap ⁇ G) are calculated from the photographed image.
- the controller 24 controls the pulling conditions such as the pulling speed of the wire 19 and the power of the heater 15 so that the diameter of the silicon single crystal 3 becomes the target diameter.
- the control unit 24 controls the height position of the quartz crucible 11 so that the distance between the melt surface and the heat shield 17 is constant.
- FIG. 4 is a schematic cross-sectional view showing a single crystal pulling state during the tail portion growing step.
- the crystal diameter gradually decreases with the progress of pulling in the tail portion growing step, so that the heat shield 17 and the silicon single crystal 3 are separated.
- the distance D between the crystals 3 gradually increases.
- the width of the heat dissipation path extending upward from the silicon melt 2 is widened and heat is more easily diffused upward than the lower end 17b of the heat shield 17, so that the space in the space above the lower end 17b of the heat shield 17 is increased.
- the temperature rises. Thereby, the upper part of the heat shield 17 is heated, and the heat shield 17 itself becomes a heat source, and the silicon single crystal 3 immediately after crystallization is heated.
- the silicon single crystal 3 cannot quickly pass through the temperature range of 1020 to 980 ° C. (OSF nucleation temperature range) in which OSF nuclei are easily formed in the single crystal, and the pulling speed of the silicon single crystal 3 is increased. It becomes even more difficult when slowing down.
- OSF nucleation temperature range 1020 to 980 ° C.
- the water cooling body 18 is provided above the lower end 17b of the heat shield 17 and inside the heat shield 17, so that it passes through the opening of the lower end 17b of the heat shield 17. Then, the temperature in the high temperature region can be lowered, and the width in the crystal growth direction in the temperature region of 1020 to 980 ° C. can be narrowed. Therefore, even when the pulling rate of the silicon single crystal 3 is made slower than before, the time for the silicon single crystal 3 to stay in the temperature range of 1020 to 980 ° C. can be shortened, and the OSF nucleation temperature range can be quickly passed.
- the OSF nucleus size in a single crystal can be made very small.
- FIG. 5 is a sequence diagram showing changes in the pulling speed of the silicon single crystal 3 and the power of the heater 15.
- the pulling speed of the silicon single crystal 3 is controlled to be constant from the body portion 3c to the tail portion 3d.
- the constant pulling speed during the tail part growing process means that the variation rate with respect to the pulling speed at the start of the tail part growing process is within ⁇ 3%.
- the crystal diameter is narrowed down by increasing the pulling speed faster than the body part growing process and by increasing the power of the heater 15 in an auxiliary manner.
- the tail aperture is realized by changing only the power of the heater 15 without changing the pulling speed. In this way, by maintaining the pulling rate constant from the start to the end of the tail 3d growth, it is possible to prevent the occurrence of dislocation of the single crystal due to crystal bending or separation from the melt.
- the pulling speed of the tail part 3d is made equal to the pulling speed of the body part 3c, it becomes difficult to control the tail aperture, but the power of the heater 15 is increased to create a situation in which the silicon melt 2 is difficult to solidify. This makes it easier to tail tail.
- the power of the heater 15 is increased, the influence of the radiant heat is further increased, and without the water-cooled body 18, the OSF nucleation temperature region of 1020 to 980 ° C. is further expanded as described above.
- the OSF nucleation temperature region can be narrowed, and the transit time (stay time) of the OSF nucleation temperature region of the silicon single crystal 3 can be shortened.
- the power of the heater 15 during the tail part growing process is larger than the power of the heater 15 at the end of the body part growing process.
- the power of the heater 15 gradually increases from the start of tail part growth, and the power of the heater 15 at the end of tail part growth is preferably 1.1 to 1.5 times that at the start of tail part growth. In this way, by gradually increasing the power of the heater 15 in the tail part growing process, and keeping the power of the heater 15 at the end of tail part growing within the range of 1.1 to 1.5 times that at the start of growing. Even when the pulling speed of the tail portion 3d is made equal to that of the body portion 3c, tail restriction can be realized, and further crystal bend and dislocation can be prevented.
- the quartz crucible 11 it is preferable to gradually raise the quartz crucible 11 to keep the liquid surface position of the silicon melt 2 constant.
- the quartz crucible 11 is at a sufficiently high position at the start of tail portion growth.
- the quartz crucible 11 interferes with the heat shield 17.
- the rise of the quartz crucible 11 must be stopped at the start or midway of the tail portion growing process, and the gap between the melt surface and the heat shield 17 is widened due to the decrease in the melt surface, so that the silicon single crystal 3 is formed.
- the OSF nucleation temperature region is widened because it is easily affected by radiant heat from the quartz crucible 11.
- the tail portion growing process is started before the silicon melt 2 is sufficiently consumed, and the quartz crucible 11 is raised until the tail portion growing process is finished, so that the height position of the melt surface is constant.
- the influence of radiant heat from the quartz crucible 11 can be suppressed, and the spread of the OSF nucleation temperature region can be suppressed.
- the crystal diameter gradually decreases and the crystal pulling state changes every moment, so that the silicon single crystal 3 is likely to be dislocated. If the pulling speed during tail part growth is slower than the conventional method, the tail part growing process time becomes longer and the risk of dislocations further increases. In order to reduce the risk of dislocation formation as much as possible under such conditions, it is preferable to keep the rotational speeds of the silicon single crystal 3 and the quartz crucible 11 constant in the tail growing step. These rotational speeds may be the same as or different from the rotational speed in the body part growing step. Thereby, the convection of the silicon melt 2 in the quartz crucible 11 can be stabilized and the melt temperature can be stabilized.
- the horizontal magnetic field or the vertical magnetic field to the silicon melt 2 by operating the magnetic field generator 21 also in the tail part growing step. By doing in this way, the convection of the silicon melt 2 in the quartz crucible 11 can be further stabilized. Since the tail portion 3d of the silicon single crystal 3 is a portion that is not used as a product and the productized region is the body portion 3c, a crystal such as an oxygen concentration level and its in-plane distribution is applied by applying a magnetic field in the tail portion growing step S16. There is no need to control quality.
- the tail portion growing step S16 it is important to quickly separate the silicon single crystal 3 from the silicon melt 2 so as not to deteriorate the quality of the body portion 3c of the silicon single crystal 3 that has been grown so far.
- the convection of the silicon melt 2 in the quartz crucible 11 can be stabilized and the melt temperature can be stabilized, thereby preventing crystal bends and dislocations. be able to.
- FIG. 6 is a side cross-sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to the second embodiment of the present invention.
- the single crystal manufacturing apparatus 1B is characterized in that the water-cooled body 18 is made of a cylindrical member that is sufficiently longer than that of the first embodiment, and the upper end of the main chamber (the lower end of the pull chamber). ) Extending downward from the position) to the inner side 17i of the heat shield 17 surrounded by a one-dot chain line in the figure. That is, the water cooling body 18 is provided so as to cover the pulling path of the silicon single crystal 3 as long as possible.
- the water-cooled body 18 exists above the lower end 17b of the heat shield 17 and on the inner side 17i of the heat shield 17, after passing through the opening of the lower end 17b of the heat shield 17.
- the temperature in the high temperature region can be lowered, and the width of the crystal region in the temperature region of 1020 to 980 ° C. can be narrowed. Therefore, even when the pulling rate of the silicon single crystal 3 is made slower than before, the time for the silicon single crystal 3 to stay in the temperature range of 1020 to 980 ° C. can be shortened, and the OSF nucleation temperature range can be quickly passed.
- the OSF nucleus size in a single crystal can be made very small.
- the water-cooled body 18 is disposed above the lower end 17b of the thermal shield 17 and inside the thermal shield 17, and in the tail growing process. Since the silicon single crystal 3 immediately after crystallization is cooled by the water-cooled body 18 and the tail portion 3d is pulled up at a constant speed with the body portion 3c, it prevents crystal bend and separation from the melt in the tail portion growing step S16. A high-quality silicon single crystal with very few OSF nuclei causing epi defects can be produced.
- the single crystallization rate and the occurrence of epi defects due to the difference in the pulling rate of the single crystal and the presence or absence of the water-cooled body 18 in the tail part growing process were evaluated.
- samples 1 to 6 of a silicon single crystal ingot having a diameter of 300 mm were pulled up using the single crystal manufacturing apparatus 1A shown in FIG.
- the lifting speed of the body part is set to 1.0 mm / min, and the quartz crucible is raised so that the distance between the melt surface and the lower end of the heat shield is constant not only during the body part growth but also during the tail part growth.
- the single crystal was pulled up while letting it go.
- samples 1 to 6 of the silicon single crystal ingot thus obtained are processed to produce a silicon wafer (polished wafer) having a thickness of 775 ⁇ m, and an epitaxial layer having a thickness of 4 ⁇ m is formed on the surface of the silicon wafer.
- Epitaxial silicon wafers corresponding to samples 1 to 6 were produced. The number of epi defects in each epitaxial silicon wafer was measured with a particle counter.
- Table 1 is a table showing the results of an evaluation test of the single crystallization rate and epi defects of samples 1 to 6.
- the single crystallization rate was 75% or more, and the number of epi defects was 5 to 10 / wf. .
- the single crystallization rate is 75% or more and the number of epi defects is less than 5 / wf. It was confirmed that the quality standard of epi defects was satisfied.
- FIG. 7 is a graph showing the relationship between the pulling position of the single crystal and the transit time of the OSF nucleation temperature region (1020 to 980 ° C. region) of the single crystal.
- the horizontal axis of the graph of FIG. 7 indicates the distance from the bottom of the single crystal (the lower end of the tail portion 3d), and the vertical axis indicates the passage time of the OSF nucleation temperature region.
- the quartz crucible 11 is raised to increase the distance (gap ⁇ G) between the melt surface and the heat shield 17, that is, the melt surface is lowered, and the melt surface and the heat shield. It can be seen that, when the control for keeping the distance from 17 constant is not performed, the passing time of the OSF nucleation temperature region of the single crystal becomes longer as the pulling position approaches the bottom. Since the pulling speed of the tail portion 3d is constant, the passage time of the OSF nucleation temperature region becomes longer. This means that the OSF nucleation temperature region expands in the pulling axis direction as the pulling position approaches the bottom. Means.
- the influence of the difference in the output of the heater 15 during the tail growing process on the quality of the single crystal was evaluated.
- the power of the heater 15 at the start and end of tail part growth was CkW and DkW, respectively, the heater power ratio D / C was changed in the range from 0.9 to 1.8 in the evaluation test.
- the other pulling conditions were the same as those for the single crystal crystallization rate and epi defect evaluation test described above.
- Table 2 is a table showing the results of the evaluation test of the crystal growth status according to the difference in the heater power ratio.
- tail heating could not be performed when the heater power ratio D / C was below 1.1. Further, when the heater power ratio D / C exceeded 1.5, crystal bend occurred, and the tail portion 3d could not be adjusted to a clean cone shape. On the other hand, when the heater power ratio D / C was in the range of 1.1 to 1.5, tail restriction could be performed and the tail portion 3d could be grown.
- the heater power ratio D / C at the end of tail part growth relative to the start of tail part growth satisfies 1.1 to 1.5, and the heater power during tail part growth is higher than that at the start of tail part growth.
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Abstract
Description
2 シリコン融液
3 シリコン単結晶(インゴット)
3a ネック部
3b ショルダー部
3c ボディー部
3d テール部
10 チャンバー
10a メインチャンバー
10b プルチャンバー
10c ガス導入口
10d ガス排出口
10e 覗き窓
11 石英ルツボ
12 サセプタ
13 回転シャフト
14 シャフト駆動機構
15 ヒーター
16 断熱材
17 熱遮蔽体
17a 熱遮蔽体の開口
17b 熱遮蔽体の下端
17i 熱遮蔽体の内側
18 水冷体
19 ワイヤー
20 ワイヤー巻き取り機構
21 磁場発生装置
22 CCDカメラ
23 画像処理部
24 制御部
Claims (7)
- 石英ルツボ内のシリコン融液からシリコン単結晶を引き上げるチョクラルスキー法によるシリコン単結晶の製造方法であって、
結晶直径が一定に維持されたボディー部を育成するボディー部育成工程と、
結晶直径が徐々に減少したテール部を育成するテール部育成工程とを含み、
前記石英ルツボの上方に配置された熱遮蔽体の下端よりも上方であって前記熱遮蔽体の内側に配置された水冷体を用いて前記シリコン融液から引き上げられた前記シリコン単結晶を冷却し、
前記テール部育成工程では前記テール部の育成開始時から終了時まで前記ボディー部育成終了時における引き上げ速度と同じ引き上げ速度で前記シリコン単結晶を引き上げることを特徴とするシリコン単結晶の製造方法。 - 前記テール部育成工程では前記シリコン単結晶の前記ボディー部の1020℃から980℃までの温度領域を15分以内で通過させる、請求項1に記載のシリコン単結晶の製造方法。
- 前記テール部の育成開始時から終了時まで前記シリコン融液を加熱するヒーターのパワーを漸増させると共に、前記テール部の育成終了時における前記ヒーターのパワーを前記テール部の育成開始時における前記ヒーターのパワーの1.1倍以上1.5倍以下に設定する、請求項1または2に記載のシリコン単結晶の製造方法。
- 前記テール部育成工程では前記熱遮蔽体と前記シリコン融液との間隔が一定となるように前記石英ルツボを上昇させる、請求項1ないし3のいずれか一項に記載のシリコン単結晶の製造方法。
- 前記テール部育成工程では前記石英ルツボの回転速度を一定に維持する、請求項1ないし4のいずれか一項に記載のシリコン単結晶の製造方法。
- 前記テール部育成工程では前記シリコン単結晶の回転速度を一定に維持する、請求項1ないし5のいずれか一項に記載のシリコン単結晶の製造方法。
- 前記テール部育成工程では前記シリコン融液に磁場を印加する、請求項1ないし6のいずれか一項に記載のシリコン単結晶の製造方法。
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CN115369482A (zh) * | 2021-05-21 | 2022-11-22 | 内蒙古中环协鑫光伏材料有限公司 | 一种适用于吸料实验的极限拉晶工艺 |
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TWI698557B (zh) * | 2018-12-28 | 2020-07-11 | 環球晶圓股份有限公司 | 矽單晶長晶方法及矽單晶長晶設備 |
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