KR20050041438A - Silicon single crystal growing method - Google Patents

Abstract

An object of the present invention is to improve the productivity of defect-free, high-quality silicon single crystal rods than before. While lowering the seed crystal 24 vertically descending to the center of the heat shield member 36 and contacting the silicon melt 12 while flowing an inert gas inside the heat shield member 36, The silicon single crystal rod 25 is grown. The heat shield member 36 has a tubular portion 37 positioned at an upper end thereof at a distance from the surface of the silicon melt 12 and surrounding the outer circumferential surface of the silicon single crystal rod 25, and in the cylinder portion at the lower portion of the tubular portion 37. And a swelling portion 41 provided in a swelling manner, the seed crystal 25 having a flow rate index S of inert gas flowing between the swelling portion 41 and the silicon single crystal rod 25 as 2.4 to 5.0 m / s. Raise). The gap W between the bulging portion 41 and the silicon single crystal rod 25 is 10 mm to 35 mm, the flow rate of the inert gas is 70 liter / min or more, and the ratio between the flow rate and the pressure in the chamber 11 is 0.017 to 0.040 liters / minute Pa.

Description

Silicon Single Crystal Growth Method {SILICON SINGLE CRYSTAL GROWING METHOD}

The present invention relates to a method for growing a silicon single crystal that pulls the silicon single crystal rod from the silicon melt while flowing an inert gas between the pulled silicon single crystal rod and the heat shield member surrounding the outer circumferential surface thereof.

Conventionally, as a device of this kind, as shown in Fig. 8, a quartz crucible 3 in which a silicon melt 2 is stored in a chamber 1 is accommodated, so that the outer circumferential surface of the silicon single crystal rod 5 and the quartz crucible 3 are formed. It is known that the heat shield member 6 is inserted between the inner circumferential surfaces so as to surround the silicon single crystal rod 5, and the upper end of the heat shield member 6 protrudes outward in a substantially horizontal direction. In this apparatus, the heat shield 6 is formed in a tubular shape whose diameter decreases along the downward direction, and its lower end extends to the vicinity of the surface of the silicon melt 2. Moreover, the upper end part of the heat shield member 6 is provided in the upper end part of the thermal insulation tube 9, and the radiant heat irradiated to the silicon single crystal rod 5 from the heater 8 is interrupted by this heat shield member 6. When an inert gas is supplied into the chamber 1 by a gas supply / distribution means (not shown) connected to the chamber 1, the inert gas is silicon single crystal rod 5 as indicated by the double-dotted arrow. It flows down along the outer circumferential surface, and is discharged out of the quartz crucible 3 through the gap between the lower end of the heat shield member 6 and the surface of the silicon melt 2.

As a method for growing a silicon single crystal using the apparatus configured as described above, a method of pulling by the Czochralski method (hereinafter referred to as CZ method) is known. This CZ method is a method of growing a columnar silicon single crystal rod under the seed crystal by bringing the seed crystal into contact with the silicon melt stored in the quartz crucible and pulling the seed crystal while rotating the quartz crucible and the seed crystal.

On the other hand, as a cause of decreasing the yield in the process of manufacturing a semiconductor integrated circuit using a wafer obtained from such a silicon single crystal rod, there is a defect due to the wafer. These defects include microdefects of oxygen precipitates, which are the nuclei of Oxidation Induced Stacking Faults (OSFs), particles originating from crystals (Crystal Originated Particles, or COPs), or intrusions. Interstitial-type Large Dislocation (hereinafter referred to as L / D). In the OSF, micro-defects, which become nuclei, are introduced during crystal growth, and they are prominent in thermal oxidation processes in manufacturing semiconductor devices, and defects such as an increase in the leakage current of the manufactured semiconductor devices are caused. do. In addition, COP is a pit caused by crystals appearing on the wafer surface when the silicon wafer after mirror polishing is washed with a mixed solution of ammonia and hydrogen peroxide. When the wafer is measured with a particle counter, this pit is also detected as a light scattering defect along with the original particles.

This C0P causes deterioration of electrical characteristics, for example, the time dependent dielectric breakdom (TDDB) of the oxide film, the time zero dielectric breakdown (TZDB), and the like. In addition, if COP is present on the wafer surface, a step may occur in the wiring process of the device, which may cause disconnection. Also in the element isolation part, it becomes a cause of leakage and the like and lowers the yield of the product. L / D is also called dislocation cluster, or is called dislocation pit because pit occurs when immersed silicon wafer with this defect in selective etching solution containing hydrofluoric acid as main component. This causes deterioration of the leakage characteristics, isolation characteristics, and the like. As a result, it is necessary to reduce OSF, COP, and L / D from silicon wafers used to fabricate semiconductor integrated circuits.

The method for producing a silicon single crystal rod using Boron Corp's theory for cutting out defect-free silicon wafers without OSF, COP and L / D is disclosed in Japanese Patent Laid-Open No. 11-1393 corresponding to US Patent No. 6045610. Is disclosed. Boronkov's theory states that in order to grow a high-purity single crystal rod with a small number of defects, the pulling speed of the single crystal rod is V (mm / min), and the temperature gradient in the single crystal rod near the interface between the single crystal rod and the silicon melt is called G (° C / mm). The V / G (mm 2 / min. In this theory, as shown in Fig. 6, V / G is taken along the horizontal axis, vacancy type point defect concentration and interstitial silicon type point defect concentration are taken on the same longitudinal axis, and V / G is taken as the vertical axis. The relationship between G and the point defect concentration is shown graphically to explain that the boundary between the hollow hole region and the lattice silicon region is determined by V / G. More specifically, when the V / G ratio is greater than or equal to the critical point, a single crystal rod having a predominantly hollow hole point defect concentration is formed, whereas when the V / G ratio is less than or equal to the critical point, a single crystal rod is formed that is superior to a lattice silicon type defect defect. In Fig. 6, [I] represents a region [(V / G) ₁ or less] in which interstitial silicon type defects are dominant and aggregates of interstitial silicon type defects exist, and [V] represents a bin in a single crystal rod. The hole-type point defect is dominant and indicates a region [(V / G) ₂ or more] in which the hole-type point defect agglomerates are present, and [P] indicates that the hole-type point defect agglomerates and the lattice silicon-type point defects do not exist. Perfect regions [(V / G) ₁ to (V / G) ₂ ] are shown. In the region [V] adjacent to the region [P], there are regions [(V / G) ₂ to (V / G) ₃ ] that form a ring-shaped OSF when the oxidation of the wafer composed of this portion is performed.

In other words, in Voronkov's theory, if the single crystal rod of silicon single crystal is pulled up at a high speed, a region [V] where the aggregate of void hole type defects dominates is formed inside the single crystal rod, and if the single crystal rod is pulled at a low speed, the single crystal The region [I] in which the aggregate of interstitial silicon type defects dominates is formed inside the rod. For this reason, in the said manufacturing method, by pulling up a single crystal rod at the most suitable pulling speed, the silicon single crystal which consists of perfect region [P] in which the aggregate of the said point defect does not exist can be manufactured.

However, in the CZ method without magnet application, there is a limit to further increase the speed of pulling up the silicon single crystal rod made of the perfect region [P] to improve the productivity. Also, impurities may be generated from a member located above the silicon single crystal rod pulled up from the silicon melt, and this impurity is mixed in an inert gas and conveyed to the outer circumferential surface of the silicon single crystal rod, whereby the silicon single crystal rod is contaminated by the impurity. You need to avoid that.

An object of the present invention is to provide a method for growing a silicon single crystal capable of improving the productivity of a defect-free, high-quality silicon single crystal rod than in the prior art.

In the invention according to claim 1, as shown in Fig. 1, an inert gas is supplied from an upper portion of the chamber 11 to the inside of the chamber 11, and the train is made to flow in an inert gas into the heat shield member 36. Raising the seed crystal 24 vertically lowered to the center of the closing member 36 in contact with the silicon melt 12 stored in the quartz crucible 13 to grow the silicon single crystal rod 25 under the seed crystal 24. It is an improvement of the method of growing a silicon single crystal.

The heat shield member 36 is characterized in that the heat shield member 36 has a tubular portion 37 in which the lower end thereof is located at an interval from the surface of the silicon melt 12 and surrounds the outer circumferential surface of the silicon single crystal rod 25. Flow rate index (S) of the inert gas obtained by the following Formula 1 provided with the bulging part 41 which expanded and installed in the direction of a cylinder in the lower part of the inside, and flows down between the bulging part 41 and the silicon single crystal rod 25. Is a method of growing a silicon single crystal, wherein the seed crystal 25 is pulled at 2.4 to 5.0 m / s.

(Formula 1)

S = (Po / E) × F / A

Here, Po is the atmospheric pressure Pa outside the chamber 11, E is the internal pressure Pa of the chamber 11, and F is the pressure of the inert gas of the room temperature state supplied to the chamber 11 here. (Po) is the flow rate (m 3 / s), and A is the cross-sectional area (m 2) between the bulging portion 41 and the silicon single crystal rod 25.

When the flow rate index S of the inert gas flowing between the bulging portion 41 and the silicon single crystal rod 25 is 2.4 to 5.0 m / s, the speed V ₂ at the boundary between the OSF generation region and the Pv region is determined. In other words, it was found that the maximum velocity (hereinafter referred to as V ₂ ) of the defect-free region, which is the velocity at the boundary with the Pv region, is fast. Therefore, in the silicon single crystal pulling method according to claim 1, the crystal axial direction temperature gradient G becomes large due to the effect of crystal cooling by inert gas or the effect of changing convection by melt cooling, and according to the theory of Boronkov. The pulling speed of the single crystal rod 25 and V (mm / min) can be raised more than before.

The invention according to claim 2 is the invention according to claim 1, wherein the gap W between the bulging portion 41 and the silicon single crystal rod 25 is 10 mm to 35 mm, and the F / E is 0.017 to 0.040 liters. It is the growth method of the silicon single crystal which is /min.Pa.

In the silicon single crystal pulling method according to this claim 2, the crystal axis direction temperature gradient G is increased, and the pulling speed of the single crystal rod 25, V (mm / min) can be increased by the theory of boronkov, and the Productivity can be improved than before. If the gap W is less than 10 mm, the swelling portion 41 may be in contact with the silicon single crystal rod 25. If the F / E is less than 0.017 liter / min · Pa, the silicon single crystal rod 25 is [P]. If the F / E exceeds 0.040 liters / minute Pa, there is a possibility that a dislocation is generated in the silicon single crystal rod 25. Here, the preferable gap W is 15 mm to 25 mm, and the preferred F / E is 0.025 to 0.035 liter / min · Pa.

The invention according to claim 3 is the invention according to claim 1 or 2, which is a method for growing a silicon single crystal having a flow rate F of 70 liters / minute or more.

Also in the silicon single crystal pulling method described in claim 3, the crystal axis direction temperature gradient G is increased to increase the pulling speed of the single crystal rod 25, V (mm / min), and improve the productivity than before. have. If the flow rate F is less than 70 liters / minute, the silicon single crystal rod 25 will hardly be in the [P] region.

(Embodiment of the Invention)

EMBODIMENT OF THE INVENTION Next, embodiment of this invention is described based on drawing.

Fig. 1 shows a growth apparatus 10 for silicon single crystal used in the method of the present invention. In the chamber 11 of the silicon single crystal growing apparatus 10, a quartz crucible 13 for storing the silicon melt 12 is provided, and the outer surface of the quartz crucible 13 is formed by the graphite susceptor 14. Is covered. The lower surface of the quartz crucible 13 is fixed to the upper end of the support shaft 16 via the graphite susceptor 14, and the lower portion of the support shaft 16 is connected to the crucible driving means 17. Although not shown, the crucible driving means 17 has a first rotating motor for rotating the quartz crucible 13 and a lifting motor for elevating the quartz crucible 13, and the quartz crucible 13 is defined by these motors. It can rotate in the direction of, and can move to an up-down direction. The outer circumferential surface of the quartz crucible 13 is surrounded by the heater 18 at predetermined intervals from the quartz crucible 13, and the heater 18 is surrounded by the thermostat 19. The heater 18 heats and melts a high-purity silicon polycrystal introduced into the quartz crucible 13 to form a silicon melt 12.

In addition, a cylindrical casing 21 is connected to the upper end of the chamber 11. The casing 21 is provided with the pulling means 22. The pulling means 22 includes a pulling head (not shown) rotatably provided in a horizontal state at the upper end of the casing 21, a second rotating motor (not shown) for rotating the head, and a quartz crucible from the head. A wire cable 23 vertically lowered toward the rotation center of (13) and an impression motor (not shown) installed in the head to wind or feed the wire cable 23; . A seed crystal 24 is attached to the lower end of the wire cable 23 so as to be immersed in the silicon melt 12 to pull up the silicon single crystal rod 25.

The chamber 11 is also connected with a gas supply / distribution means 28 for supplying an inert gas to the silicon single crystal rod side of the chamber 11 and discharging the inert gas from the crucible inner circumferential side of the chamber 11. The gas supply / distribution means 28 includes a supply pipe 29 having one end connected to a main wall of the casing 21 and the other end connected to a tank (not shown) for storing the inert gas, and one end of the chamber 11. It has a discharge pipe 30 connected to the bottom wall and connected to the vacuum pump (not shown) at the other end. The supply pipe 29 and the discharge pipe 30 are provided with first and second flow rate regulating valves 31 and 32 for adjusting the flow rate of the inert gas flowing through these pipes 29 and 30, respectively.

On the other hand, an encoder (not shown) is provided on an output shaft (not shown) of the pulling motor, and an encoder (not shown) is installed on the crucible driving means 17 for detecting a lifting position of the support shaft 16. . Each detection output of the two encoders is connected to a control input of a controller (not shown), and the control output of the controller is connected to a motor for pulling up of the pulling means 22 and a motor for lifting up and down the crucible driving means, respectively. In addition, the controller is provided with a memory (not shown), in which the winding length of the wire cable 23 to the detection output of the encoder, that is, the pulling length of the silicon single crystal rod 25 is stored as the first map. In addition, the liquid level of the silicon melt 12 in the quartz crucible 13 with respect to the pulling length of the silicon single crystal rod 25 is stored in the memory as the second map. The controller is configured to control the lifting motor of the crucible drive means 17 to always maintain the liquid level of the silicon melt 12 in the quartz crucible 13 on the basis of the detection output of the encoder in the pulling motor. do.

Between the outer circumferential surface of the silicon single crystal rod 25 and the inner circumferential surface of the quartz crucible 13, a heat shield member 36 surrounding the outer circumferential surface of the silicon single crystal rod 25 is provided. The heat shield member 36 is formed in a cylindrical shape to block radiant heat from the heater 18, and a flange portion which is continuously installed at an upper edge of the tube portion 37 and protrudes in an approximately horizontal direction to the outside. Has 38. By installing the flange portion 38 on the thermos 19, the heat shield member 36 is provided with the chamber 11 such that the lower edge of the tube portion 37 is positioned upward by a predetermined distance from the surface of the silicon melt 12. Is fixed inside. The heat shield member 36 is formed of graphite, or graphite coated with SiC on its surface. The cylinder part 37 is formed with the tubular body of the same diameter, or the tubular body formed small in diameter along the downward direction.

As shown in FIG. 2, the cylinder part 37 in this embodiment is a cylindrical body of the same diameter, and the bulging part 41 which expands in the direction inside a cylinder is provided in the lower part of the cylinder part 37. As shown in FIG. As an example of the bulge 41, the bulge 41 is connected to the lower edge of the tube portion 37 and extends horizontally to reach near the outer circumferential surface of the silicon single crystal rod 25 ( 42, the vertical wall 44 continuously installed at the inner edge of the bottom wall 42, and the upper wall 46 continuously installed at the upper edge of the vertical wall 44 and formed to increase in diameter in an upward direction. It is composed. The cylinder portion 37 and the bottom wall 42 are integrally formed, and the vertical wall 44 and the upper wall 46 are integrally formed. Here, the bulging part 41 in this embodiment is formed so that the clearance gap W between the outer peripheral surface of the silicon single crystal rod 25 to be pulled up and the vertical wall 44 may be 10 mm or more and 35 mm or less.

When the diameter of the silicon single crystal rod 25 to be pulled is referred to as D, the vertical wall 44 has a height H of 10 mm or more and D / 2 or less, and an axial line of the silicon single crystal rod 25 is used. It is formed in parallel with the line or inclined at an angle of −5 degrees or more and +30 degrees or less. -5 degrees means that the diameter is reduced with an angle of 5 degrees with respect to the axial line toward the upper direction, and +30 degrees means with an angle of 30 degrees with respect to the axial line and directed upward. Although it is shown that it is formed so that a diameter may become large, it is preferable to form so that it may become parallel with the axial center line of the silicon single crystal rod 25, ie, the vertical wall 44 is perpendicular. In addition, the space | interval W and height H mentioned above are suitably determined according to the diameter of the silicon single crystal rod 25 to be pulled up. The upper wall 46 is formed horizontally, or is formed so that the diameter increases in the upward direction at an angle of less than 80 degrees to 0 degrees with respect to the horizontal plane so that the upper edge is in contact with the inner circumferential surface of the tube portion 37 . In addition, a felt material made of carbon fibers is formed inside the swelling portion 41 surrounded by the lower portion of the cylinder portion 37, the bottom wall 42, the vertical wall 44, and the upper wall 46. Is charged.

The pulling method of this invention using the apparatus of such a structure is demonstrated.

When pulling up the silicon single crystal rod 25, the pulling motor (not shown) is rotated to feed out the wire cable 23, and the seed crystal 24 attached to the lower end portion is immersed in the silicon melt 12. After that, the seed crystal 24 is gradually raised to form a religious shaft at the lower portion thereof to further form a shoulder. After the shoulder is formed, the linear motion portion is continuously formed in the lower portion thereof. When the linear motion portion is formed, the inert gas is supplied from the upper part of the chamber 11 to the inside of the chamber 11 by adjusting the first and second flow rate regulating valves 31 and 32, and to the outside of the chamber 11. The atmospheric pressure in Po, the internal pressure of the chamber 11 is E, the temperature is 25 ° C., and the flow rate in the pressure Po of the inert gas supplied to the chamber 11 is F, the bulge 41 and the silicon. When the cross-sectional area between the single crystal rods 25 is A, the swelling portion 41 obtained by (Po / E) × F / A = S and the linear portion in the silicon single crystal rod 25 are obtained. The flow rate index S of the inert gas flowing in between is adjusted to 2.4 to 5.0 m / s, preferably 3.5 to 5.0 m / s. In addition, the inert gas flows down between the swelling part 41 and the linear motion part, and then passes between the surface of the silicon melt 12 and the lower end of the heat shielding member 26 to be discharged to the outside from the discharge pipe 30.

Here, in the method of the present invention, it is required that a bulge portion 41 that expands in the direction of the barrel is formed under the cylinder portion 37, so that heat dissipation from the silicon melt 12 is applied to the bulge portion 41. It is difficult to escape upward by the provided heat insulating material 47. Therefore, the heat radiation from the silicon single crystal rod 25 in the liquid surface vicinity is also suppressed. As a result, the temperature drop in the outer peripheral portion of the silicon single crystal rod 25 can be prevented, and the temperature distribution in the silicon single crystal rod 25 becomes substantially uniform from the center toward the outer circumferential surface so that the inside of the silicon single crystal rod 25 becomes a perfect region. The permissible range of the pulling speed of the ingot is expanded by the reason that the in-plane uniformity of the pulling speed to be a perfect area is improved.

In addition, since the flow rate index S of the inert gas flowing between the bulging portion 41 and the silicon single crystal rod 25 is set to a relatively fast 2.4 to 5.0 m / s, preferably 3.5 to 5.0 m / s, the single crystal rod The ability to cool 25 rises. As a result, the temperature gradient G in the silicon single crystal rod 25 is also relatively large, and according to Boronkov's theory, the pulling speed and V (mm / min) of the single crystal rod can be increased than before, and the productivity can be improved. have.

On the other hand, the inert gas supplied from the gas supply pipe 27a into the chamber 11 may contain particles of heavy metals such as iron or copper generated from the upper members in the chamber 11, and the particles may contain the chamber 11. Although it flows down according to the flow of inert gas along the member surface of the upper part in the inside), the particle is discharged out of the chamber 11 according to the flow of inert gas, without contacting the silicon single crystal rod 25. As a result, since the silicon single crystal rod 25 pulled up from the silicon melt 12 is hardly contaminated by particles, the silicon single crystal rod 25 of high purity can be manufactured.

Further, the lower limit of the flow rate of the inert gas to 2.4 m / s increases the possibility that the silicon single crystal rod 25 does not become the [P] region when the flow rate is lower than this, and the upper limit of the flow rate of the inert gas is 5.0. The m / s is because when the flow rate exceeds this, the potential for generation of the silicon single crystal rod 25 is increased due to the particle generated in the chamber 11 attached to the silicon single crystal rod 25 or the like.

(Example)

Next, the Example of this invention is described in detail with a comparative example.

<First Embodiment>

In the silicon single crystal pulling apparatus as shown in Figs. 1 and 2, the height of the heater 18 is about 450 mm, and the flow rate of the inert gas flowing down inside the heat shield member 36 is 110 liter / Fig. 6 (V / G) in which a ring-shaped OSF ring is formed when the silicon single crystal rod having a diameter of about 200 mm is pulled about 400 mm for each of the minute, 130 liter, and 150 liter / minute cases The pulling speed in ₂ , that is, the pulling speed V ₂ in FIG. 7 and the pulling speed in (V / G) ₁ in FIG. 6 forming a perfect region, that is, the pulling speed V in FIG. ₁ ) were obtained respectively.

Second Embodiment

Except having changed the height of the heater 18 into about 600 mm, the pulling apparatus comprised similarly to 1st Example was prepared. In this pulling device, a silicon single crystal rod having a diameter of about 200 mm is applied to each of the cases where the amount of inert gas flowing into the heat shield member 36 is changed to 70 liters / minute and 110 liters / minute. The pulling speed in FIG. 6 (V / G) ₂ in which a ring-shaped OSF ring is formed when pulled up by 400 mm, that is, the pulling speed V _{2 in} FIG. The pulling speed in V / G) ₁ , that is, the pulling speed V _{1 in} FIG.

<First comparative test and evaluation>

Fig. 3 shows each pulling speed V ₂ (standard value) corresponding to the flow rate of the inert gas obtained in the first and second embodiments. Here, the pulling speed V ₂ is represented by a relative value when the pulling speed is 1 when the amount of the inert gas is 70 liters / minute.

Further, the differences in the respective pulling speeds V ₂ and V ₁ obtained by the first and second embodiments, that is, the pure margins V ₂ -V ₁ and V ₂ ′-shown in FIG. 7. V ₁ ') was obtained. Here, the pure margin means the difference between the maximum pulling speed and the minimum pulling speed, which are perfect regions without the presence of agglomerates of point defects throughout the cross section of the silicon single crystal rod 25, and (V ₂ -V ₁ ) in the present specification. The description of (V2 '-V ₁ ') is omitted. The pulling speed difference in the amount of this inert gas is shown in accordance with FIG. The pulling-up speed difference (V ₂ - V ₁₎ is shown the flow rate of the inert gas, the first exemplary embodiment relative value in the case where the pulling rate of the car in the 110 l / min to 1.

As apparent from Fig. 3, it can be seen that the pulling speed V ₂ also increases proportionally as the flow rate of the inert gas increases with the first and second embodiments. This is considered to be because the ability to cool the single crystal rod 25 also increases when the flow rate of the inert gas increases.

In addition, from the results of the second embodiment, it can be seen that when the supply amount of the inert gas increases, the pulling speed difference also increases. This is due to the increase in the cooling effect of the silicon single crystal rod 25 and the cooling effect on the liquid level of the silicon melt 12 by the inert gas, so that the flow of the silicon melt 12 changes and the vicinity of the solid-liquid boundary surface. It is considered that the temperature gradient of the silicon single crystal rod 25 of Z is changed.

<2nd comparative test and evaluation>

From the flow rates of the respective inert gases determined by the first and second embodiments, the flow rate index S of the inert gas flowing between the bulge 41 and the silicon single crystal rod 25 was obtained. 4 shows the relationship between the flow rate index S of the inert gas and the pulling speed V ₂ (standard value). Here, the pulling speed V ₂ is represented by a relative value when the pulling speed is 1 when the amount of the inert gas is 70 liters / minute. From the flow rates of the inert gas of the first and second embodiments, the flow rate index S of the inert gas flowing between the bulge 41 and the silicon single crystal rod 25 is obtained, and the impression to the flow rate index S is obtained. The speed difference (V ₂ -V ₁ ) was obtained, respectively. This difference is shown in accordance with FIG. The pulling-up speed difference (V ₂ - V ₁₎ exhibited a relative value in the case where the pulling rate difference in the flow rate of an inert gas of the first embodiment to 110 liters / minute to 1.

As is apparent from FIG. 4, the pulling speed V ₂ and the pulling speed of the flow rate index S of the inert gas flowing between the bulging portion 41 and the silicon single crystal rod 25 in the range of 2.4 to 5.0 m / s. It can be seen that a relatively high value is shown when the flow velocity index S is large in both of the differences V ₂ -V ₁ . In particular, the speed difference increases with the flow rate index (S). This means that the OSF, COP, or L / D does not occur in the silicon single crystal rod even when the silicon single crystal rod is pulled up at a relatively high pulling speed. Thus, the productivity of the defect-free and high-quality silicon single crystal rod is improved according to the present invention. It turns out that it can improve more.

Third comparative test and evaluation

The flow rate of each inert gas determined by the first and second embodiments was divided by the pressure in the chamber 11 to obtain the ratio. The relationship between this ratio and the pulling speed V ₂ (standard value) is shown in FIG. 5. Here, the pulling speed V ₂ is represented by a relative value when the pulling speed is 1 when the amount of the inert gas is 70 liters / minute. From the flow rates of the inert gas of the first and second embodiments, the flow rate was divided by the pressure in the chamber 11 to obtain the ratio, and the pulling speed differences V ₂ -V ₁ to the ratio were obtained, respectively. This difference is shown in accordance with FIG. The pulling-up speed difference (V ₂ - V ₁₎ exhibited a relative value in the case where the pulling rate difference in the flow rate of an inert gas of the first embodiment to 110 liters / minute to 1.

As is apparent from Fig. 5, the ratio of the pulling speed V ₂ and the pulling speed difference V ₂ -V _{1 in} the range of 0.017 to 0.040 liters / minute · Pa of the ratio between the flow rate of the inert gas and the pressure in the chamber 11 is shown. It can be seen that both show relatively high values when the ratio of flow rate and pressure is large. In particular, the speed difference increases with the ratio of flow rate and pressure. This means that the OSF, COP, or L / D does not occur in the silicon single crystal rod even when the silicon single crystal rod is pulled up at a relatively high pulling speed. Thus, the productivity of the defect-free and high-quality silicon single crystal rod is improved according to the present invention. It turns out that it can improve more.

As described above, according to the present invention, the flow rate index S of the inert gas flowing between the bulge and the silicon single crystal rod is 2.4 by using the heat shield member provided with the bulge in the swelling direction in the lower part of the barrel. Since the seed crystal is pulled up to 5.0 m / s, the ability to cool the single crystal rod can be increased. As a result, the temperature gradient G in the silicon single crystal rod is also relatively large, and according to Boronkov's theory, the pulling speed and V (mm / min) of the single crystal rod can be increased than before, and the productivity can be improved than before.

1 is a cross-sectional configuration diagram of a silicon single crystal pulling apparatus used in the method of the present invention.

FIG. 2 is an enlarged cross-sectional view of portion A of FIG. 1 showing a heat shield member of the apparatus; FIG.

Fig. 3 is a diagram showing a pulling speed and a difference in speed with respect to the gas flow rate in the embodiment.

Fig. 4 is a diagram showing a pulling speed and a difference in speed with respect to the gas flow rate in the embodiment.

Fig. 5 is a diagram showing the difference between the pulling speed and the speed with respect to the ratio of the gas flow rate and the pressure in the embodiment.

Fig. 6 is a view showing that ingots having a predominantly hollow hole defect concentration are formed when the V / G ratio based on the Voronkov's theory is higher than or equal to the critical point, and ingots that are predominantly interstitial silicon type defect defect are formed when the V / G ratio is below the critical point. .

Fig. 7 is an explanatory diagram showing the distribution of interstitial silicon and voids in a single crystal rod when the silicon single crystal rod is pulled up at a predetermined variable pulling rate.

Fig. 8 is a sectional view corresponding to Fig. 2 showing a conventional general pulling apparatus.

<Explanation of symbols for the main parts of the drawings>

10: silicon single crystal pulling apparatus

12: silicone melt

13: quartz crucible

18: heater

24: seed crystal

25: silicon single crystal rod

36: heat shield member

37: tube

41: bulge

Claims (3)

The heat shield member 36 is supplied with an inert gas from the upper portion of the chamber 11 to the inside of the chamber 11, and the inert gas flows down inside the heat shield member 36 installed in the chamber 11. Of silicon single crystal which is vertically lowered to the center of the silicon crystal 12 to raise the seed crystal 24 brought into contact with the silicon melt 12 stored in the quartz crucible 13 to grow the silicon single crystal rod 25 under the seed crystal 24. In the upbringing method, The heat shield member 36 has a lower end portion disposed upwardly at a distance from the surface of the silicon melt 12 and a cylindrical portion 37 surrounding the outer circumferential surface of the silicon single crystal rod 25 and a lower portion of the cylindrical portion 37. It is provided with the bulging part 41 expanded and installed in the direction inside a cylinder, Inert gas in the room temperature state where P _O is the atmospheric pressure Pa outside the chamber 11, E is the internal pressure Pa of the chamber 11, and F is supplied to the chamber 11. Is the flow rate (m 3 / s) at the pressure Po, and when A is the cross-sectional area (m 2) between the bulge 41 and the silicon single crystal rod 25, the bulge 41 and The flow rate index S of the inert gas flowing between the silicon single crystal rods 25 is obtained by S = (Po / E) × F / A, and the flow rate index S is set to 2.4 to 5.0 m / s. And growing the seed crystal (25). The silicon (W) according to claim 1, wherein the gap (W) between the bulging portion 41 and the silicon single crystal rod 25 is 10 mm to 35 mm, and the F / E is 0.017 to 0.040 liter / min.Pa. How to grow single crystals. The method for growing a silicon single crystal according to claim 1 or 2, wherein the flow rate F is 70 liters / minute or more.