JP3719336B2 - Silicon single crystal pulling apparatus and pulling method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicon single crystal pulling apparatus for pulling and growing a silicon single crystal rod and a pulling method thereof.
[0002]
[Prior art]
The Czochralski method (hereinafter referred to as CZ method) is known as a method for growing a silicon single crystal rod, in which a high-purity silicon single crystal rod for semiconductor is grown from a silicon melt obtained by melting silicon polycrystal and storing it in a crucible. It has been. In this CZ method, a silicon melt in a quartz crucible is heated and maintained at a predetermined temperature, a mirror-etched seed crystal is brought into contact with the silicon melt, and the seed crystal is pulled to grow a silicon single crystal rod. is there. In this method of growing a silicon single crystal rod, after pulling up the seed crystal and preparing a seed drawn portion from the silicon melt, the shoulder is formed by gradually thickening the crystal to the diameter of the target silicon single crystal rod, Thereafter, it is further pulled up to form a straight body portion of the silicon single crystal rod.
[0003]
As shown in FIG. 4, a conventional apparatus of this type includes a quartz crucible 3 that is fixed to the upper end of a support shaft 6 and stores a silicon melt 2 provided in the chamber 1, and the quartz crucible 3 is supported on the support shaft. A crucible lifting / lowering means 7 that moves up or down via 6, a side carbon heater 8 provided in the chamber 1 around the quartz crucible 3, and a bottom carbon heater 9 provided in the chamber 1 below the quartz crucible 3. The one with is known. The crucible raising / lowering means 7 prevents the surface of the silicon melt 2 from being lowered by pulling up the silicon single crystal rod 5 by raising the quartz crucible 3 through the support shaft 6, and the surface of the silicon melt 2 is placed at a predetermined position. So that the high-quality silicon single crystal rod 5 can be obtained and the side carbon heater 8 and the bottom carbon heater 9 can heat the silicon melt 2 to maintain the temperature of the silicon melt 2 at a predetermined temperature. Configured as follows.
[0004]
[Problems to be solved by the invention]
However, in the conventional silicon single crystal pulling apparatus, the quartz crucible 3 is raised by the crucible lifting / lowering means 7, so that the gap between the bottom carbon heater 9 provided in the chamber 1 below the quartz crucible 3 and the quartz crucible 3 is between. The distance increases as the silicon single crystal rod 5 is pulled up, and when the silicon single crystal rod 5 grows and the amount of the silicon melt 2 decreases, the silicon melt 2 that is the remaining liquid from the bottom carbon heater 9. Since the liquid level of the silicon melt 2 is lowered and the heat from the side carbon heater 8 does not reach the remaining liquid sufficiently, there is a problem that the remaining silicon melt 2 is easily recrystallized. If the residual liquid 2 is recrystallized during the growth of the silicon single crystal rod 5, there is a possibility that the grown silicon single crystal rod 5 may have a serious adverse effect.
[0005]
Further, the temperature control of the silicon melt 2 by the side carbon heater 8 and the bottom carbon heater 9 in a state in which the amount of the silicon melt 2 is reduced and the silicon melt 2 is separated from the bottom carbon heater 9 Since the liquid level of the liquid 2 is lowered, there is a problem that the quartz crucible 3 itself storing the silicon melt 2 is subjected to thermal stress and its life is reduced. In order to prevent the pulling up of the silicon single crystal rod 5 in a state in which the residual liquid is recrystallized, the remaining amount of the silicon melt 2 is conventionally about 30% of the amount of the silicon melt 2 at the beginning of storage. By the way, the pulling of the silicon single crystal rod 5 is finished. Therefore, the so-called solidification rate expressed as a value obtained by multiplying the weight of the pulled silicon single crystal rod 5 by the weight of the silicon melt 2 initially stored in the quartz crucible 3 by 100 is about 70%. There were relatively small defects. In particular, when a large-diameter crucible is used to pull up a large-diameter silicon single crystal rod, the tendency becomes stronger.
[0006]
An object of the present invention is to provide a silicon single crystal pulling apparatus and a pulling method thereof capable of improving the solidification rate while suppressing deterioration of a carbon heater and a quartz crucible.
[0007]
[Means for Solving the Problems]
As shown in FIG. 1, the invention according to claim 1 is a quartz crucible 13 which is fixed to the upper end of the support shaft 16 and is provided in the chamber 11 and stores the silicon melt 12, and the quartz crucible 13 is connected to the support shaft 16. A crucible raising / lowering means 17 for raising or lowering through a side, a side carbon heater 18 provided in the chamber 11 around the quartz crucible 13, and a bottom carbon heater 27 provided in the chamber 11 below the quartz crucible 13. This is an improvement of the silicon single crystal pulling device provided with the heater lifting / lowering means 41 for raising or lowering the bottom carbon heater 27 independently of the crucible lifting / lowering means 17 .
As shown in FIG. 3 , the characteristic configuration is that the bottom carbon heater 27 is constituted by two or more ring-shaped carbons 27a, 27b, and 27c arranged concentrically around the support shaft 16 .
[0008]
When pulling up the silicon single crystal rod 25 c, the crucible lifting / lowering means 17 raises the quartz crucible 13 via the support shaft 16 to prevent the surface of the silicon melt 12 from being lowered due to the pulling up of the silicon single crystal rod 25. The heater lifting / lowering means 41 moves the bottom carbon heater 27 upward to bring the bottom carbon heater 27 closer to the quartz crucible 13. The bottom carbon heater 27 is heated close to the quartz crucible 13 to keep the melt surface temperature of the silicon melt 12 at a predetermined temperature while suppressing power consumption.
And the quartz crucible 13 can be heated effectively by comprising the bottom carbon heater 27 by 1 or 2 or more ring-shaped carbon 27a, 27b, 27c.
[0009]
The invention according to claim 2 is the invention according to claim 1, wherein the heater elevating means 41 is provided with a support rod 42 in which a bottom carbon heater 27 is attached to the upper end, penetrates the lower portion of the chamber 11, and a rack gear is formed around it. And a drive gear 43 that is provided below the chamber 11 and meshes with the rack gear, and a motor 46 that drives the drive gear 43, and a support bar 42 is provided for each of the ring-shaped carbons 27a, 27b, and 27c. This is a silicon single crystal pulling device having rods 42b, 42c and 42d .
Since the support bar 42 moves up and down by the rotation of the drive gear meshing with the rack gear, the position of the bottom carbon heater 27 can be easily controlled.
[0011]
The support rod is provided with auxiliary rods 42b, 42c, and 42d that support the ring-shaped carbons 27a, 27b, and 27c, thereby reliably supporting the ring-shaped carbons 27a, 27b, and 27c, and the bottom carbon heater 27 with the quartz crucible 13. Can be effectively approached.
[0012]
In the invention according to claim 3 , as shown in FIG. 1, the quartz crucible 13 fixed to the upper end of the support shaft 16 and provided in the chamber 11 is disposed around the quartz crucible 13 and in the chamber 11 below. The silicon polycrystal is melted by the side carbon heater 18 and the bottom carbon heater 27 and the silicon melt 12 is stored, and the quartz crucible 3 is grown from the silicon melt 12 while being lifted by the crucible lifting / lowering means 17 via the support shaft 16. This is an improvement of the method of pulling up the silicon single crystal rod 25.
The characteristic feature is that the bottom carbon heater 27 is composed of two or more ring-shaped carbons 27a, 27b, 27c arranged concentrically around the support shaft 16 , and the bottom carbon heater 27 is pulled up when the silicon single crystal rod 25 is pulled up. The crucible is lifted by the heater lifting / lowering means 41 independently of the crucible lifting / lowering means 17.
The heater lifting / lowering means 41 moves the bottom carbon heater 27 upward to bring the bottom carbon heater 27 closer to the quartz crucible 13, and the bottom carbon heater 27 is heated close to the quartz crucible 13 to suppress power consumption. However, the melt surface temperature of the silicon melt 12 is maintained at a predetermined temperature.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, a quartz crucible 13 for storing a silicon melt 12 (FIG. 2) is provided in a chamber 11 of a silicon single crystal pulling apparatus 10, and the outer surface of the quartz crucible 13 is graphite. Covered by susceptor 14. 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 lifting / lowering means 17. Although not shown, the crucible elevating means 17 has a first rotating motor for rotating the quartz crucible 13 and an elevating motor for raising and lowering the quartz crucible 13, and the quartz crucible 13 can be rotated in a predetermined direction by these motors. At the same time, it is movable in the vertical direction. The outer peripheral surface of the quartz crucible 13 is surrounded by a side carbon heater 18 at a predetermined interval from the quartz crucible 13, and the side carbon heater 18 is surrounded by a heat retaining cylinder 19.
[0014]
A cylindrical casing 21 is connected to the upper end of the chamber 11. The casing 21 is provided with a pulling means 22. The pulling means 22 is a pulling head (not shown) provided at the upper end of the casing 21 so as to be turnable in a horizontal state, a second rotating motor (not shown) for rotating the head, and a quartz crucible 13 from the head. And a pulling motor (not shown) that is provided in the head and winds or feeds the wire cable 23. A seed crystal 24 is attached to the lower end of the wire cable 23 to immerse the silicon single crystal rod 25 in the silicon melt 12.
[0015]
Further, a gas supply / discharge 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 peripheral surface side of the chamber 11 is connected to the chamber 11. The gas supply / discharge means 28 has one end connected to the peripheral wall of the casing 21 and the other end connected to a tank (not shown) for storing the inert gas, and one end connected to the lower wall of the chamber 11. The other end has a discharge pipe 30 connected to a vacuum pump (not shown). The supply pipe 29 and the discharge pipe 30 are respectively provided with first and second flow rate adjusting valves 31 and 32 for adjusting the flow rate of the inert gas flowing through the pipes 29 and 30.
[0016]
On the other hand, a cylindrical heat shield 26 surrounding the silicon single crystal rod 25 is provided between the outer peripheral surface of the pulled silicon single crystal rod 25 and the inner peripheral surface of the quartz crucible 13. The heat shield 26 is provided to shield the heat of the silicon melt 12 from reaching the silicon single crystal rod 25, and a flange portion projecting outward in a substantially horizontal direction on the upper edge of the heat shield 26. 26a is continuously provided. By placing the flange portion 26a on the heat insulating cylinder 19, the heat shield 26 is fixed in the chamber 11, and the lower edge of the heat shield 26 is predetermined from the surface of the silicon melt 12 stored in the quartz crucible 13. It is configured to be positioned upward by a distance.
[0017]
A bottom carbon heater 27 is provided in the chamber 11 below the quartz crucible 13, and a pair of heater elevating means 41 is provided in the lower portion of the chamber 11. The bottom carbon heater 27 heats and melts the high-purity silicon polycrystal charged in the quartz crucible 13 together with the side carbon heater 18 to form the silicon melt 12. The heater elevating means 41 has a rack gear formed around it, a support rod 42 inserted through a lower wall which is the lower part of the chamber 11, a drive gear provided below the chamber 11 and meshed with the rack gear, and a drive for driving the drive gear. And a motor 46. The drive gear is built in the gear box 43 so that the support bar 42 can be moved up and down by rotation of the drive gear 46 by the drive motor 46, and the bottom carbon heater 27 is fixed to the upper end of the support bar 42. The heater raising / lowering means 41 is configured to raise or lower the bottom carbon heater 27 by moving the support bar 42 up and down.
[0018]
As shown in detail in FIG. 3, the bottom carbon heater 27 in the present embodiment is configured by three ring-shaped carbons 27 a, 27 b, and 27 c that are arranged concentrically around the support shaft 16. Each of the pair of support bars 42 includes a support bar main body 42a and three conductive auxiliary bars 42b, 42c, and 42d provided for each ring-shaped carbon. That is, a total of six auxiliary bars are provided. The upper ends of the pair of auxiliary rods 42b, 42c, and 42d are connected to the ring-shaped carbons 27a, 27b, and 27c, respectively. In FIG. 48 is fixed. The left and right auxiliary rods 42d are fixed through the base plates 47 and 48, and insulating couplings 45 and 45 are provided at the lower ends of the auxiliary rods 42d, respectively. The insulating coupling 45 is configured to be coupled to the support bar main body 42a and the auxiliary bar 42d coaxially and in an electrically non-contact manner.
[0019]
A power supply device 51 for supplying power to the ring-shaped carbons 27a, 27b, 27c is connected to the auxiliary rods 42b, 42c, 42d shown on the right side of the figure via fixed contacts 51a, 51b, 51c. The fixed contacts 51a, 51b, 51c are in contact with the auxiliary rods 42b, 42c, 42d shown on the right side of the drawing, so that the power of the power supply device 51 can be supplied to the auxiliary rods 42b, 42c, 42d while these are moving up and down. Configured. A grounded fixed contact 53 is provided in contact with the bent vertical surface 48 a of the base plate 48. The fixed contact 53 is configured to ground the auxiliary rods 42b, 42c, 42d and the ring-shaped carbons 27a, 27b, 27c while the base plate 48 moves up and down together with the auxiliary rods 42b, 42c, 42d.
[0020]
1 and 2, a rotary encoder (not shown) is provided on the output shaft (not shown) of the pulling motor in the pulling means 22, and the silicon melt in the quartz crucible 13 is placed in the crucible lifting / lowering means 17. A weight sensor (not shown) for detecting the weight of the liquid 12 and a linear encoder (not shown) for detecting the lift position of the support shaft 16 are provided. Further, the pulling device 10 is provided with a temperature sensor (not shown) for detecting the melt surface temperature of the silicon melt 12. The detection outputs of the rotary encoder, weight sensor, linear encoder, and temperature sensor are connected to the control input of a controller (not shown), and the control output of the controller is the lifting motor of the lifting means 22 and the lifting motor of the crucible lifting means 17. And the heater 46 is connected to a driving motor 46 of the lifting / lowering means 41. In addition, the controller is provided with a memory (not shown), and the winding length of the wire cable 23 with respect to the detection output of the rotary encoder, that is, the pulled length of the silicon single crystal rod 25 is stored as a first map. The liquid level of the silicon melt 12 in the quartz crucible 13 with respect to the detection output of the weight sensor is stored as the second map. The controller controls the raising / lowering motor of the crucible raising / lowering means 17 based on the detection output of the weight sensor so that the liquid level of the silicon melt 12 in the quartz crucible 13 is always kept at a constant level, and the bottom carbon heater 27 is turned on. The drive motor 46 of the heater lifting / lowering means 41 is controlled so as to be raised or lowered independently of the crucible lifting / lowering means 17.
[0021]
A method for pulling a silicon single crystal according to the present invention using the apparatus configured as described above will be described.
First, high-purity silicon polycrystal is put into the quartz crucible 13, and the high-purity silicon polycrystal is heated and melted by the side carbon heater 18 and the bottom carbon heater 27 to form the silicon melt 12. After the silicon polycrystal is melted and the silicon melt 12 is stored in the quartz crucible 13, the first and second flow rate adjusting valves 31 and 32 are opened to supply an inert gas into the casing 21 and the silicon melt. The gas evaporated from the surface of 12 is discharged from the discharge pipe 30 together with this inert gas, and the melt surface temperature of the silicon melt 12 that pulls up the silicon single crystal rod 25 is adjusted to a predetermined temperature. This temperature adjustment is performed by heating for a predetermined time by the side carbon heater 18 and the bottom carbon heater 27.
[0022]
After adjusting the melt surface temperature of the silicon melt 12, the wire 19 is drawn out by a pulling motor (not shown) of the pulling means to lower the seed crystal 24 and bring the tip portion into contact with the silicon melt 12. Thereafter, the seed crystal 24 is gradually pulled up to form a seed drawn portion 25a as shown in FIG. 2, and then the seed crystal 24 is further lifted to first grow a shoulder portion 25b below the seed drawn portion 25a. Thereafter, the seed crystal 24 is further pulled up to form a straight body portion 25c below the shoulder portion 25b as shown in FIG.
[0023]
When forming the straight body portion 25 c, the crucible elevating means 17 raises the quartz crucible 13 via the support shaft 16 to prevent the surface of the silicon melt 12 from being lowered due to the pulling up of the silicon single crystal rod 25, thereby The surface of the liquid 12 is maintained substantially uniform. When the straight body portion 25c is grown to a predetermined length, the surface area of the silicon single crystal rod 25 increases, and the amount of heat dissipated from this surface area increases. As the amount of heat dissipated increases, the melt surface temperature of the silicon melt 12 in which the straight body portion 25c is grown for a predetermined length decreases. The heater lifting / lowering means 41 moves the support bar 42 upward as indicated by the broken line arrow in FIG. 1 to bring the bottom carbon heater 27 closer to the quartz crucible 13 and prevent the melt surface temperature from decreasing. That is, the heater elevating means 41 brings the bottom carbon heater 27 close to the quartz crucible 13 and heats the bottom carbon heater 27 in the vicinity of the quartz crucible 13, thereby suppressing the power consumption and the melt surface of the silicon melt 12. Keep temperature at a predetermined temperature.
[0024]
In the above-described embodiment, the bottom carbon heater 27 composed of the three ring-shaped carbons 27a, 27b, and 27c is used. However, the bottom carbon heater may be a bottom carbon heater composed of a single ring heater. A bottom carbon heater composed of four or five ring heaters may be used.
[0025]
【The invention's effect】
As described above, according to the present invention, since the heater lifting / lowering means for raising or lowering the bottom carbon heater independently from the crucible lifting / lowering means is provided, the bottom carbon heater is moved to the crucible lifting / lowering means when the silicon single crystal rod is pulled up. The bottom carbon heater heats the silicon melt in the state of being close to the quartz crucible by being raised by the heater lifting means independently. For this reason, it becomes easier to control the temperature of the silicon melt as compared with the prior art, and the temperature can be controlled effectively while suppressing the deterioration of the carbon heater and the quartz crucible. As a result, the temperature of the silicon melt can be controlled even if the residual amount of the silicon melt is less than 30% of the silicon melt initially stored in the quartz crucible, and the silicon melt is solidified into a silicon single crystal rod. The rate can be improved to about 80%.
[0026]
Also, the heater lifting / lowering means drives the drive gear and the support rod, which has a bottom carbon heater attached to the upper end, penetrates the lower part of the chamber and has a rack gear formed around it, and is provided below the chamber and meshes with the rack gear. If the motor is configured, the support bar moves up and down by the rotation of the drive gear meshing with the rack gear, so that the position of the bottom carbon heater can be easily controlled.
Furthermore, if the bottom carbon heater is composed of one or more ring-shaped carbons arranged concentrically around the support shaft, the quartz crucible can be heated effectively, and a support bar is provided for each ring-shaped carbon. If the auxiliary rod is provided, the ring carbon can be reliably supported by the support rod, and the bottom carbon heater can be effectively brought close to the quartz crucible.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a silicon single crystal pulling apparatus according to the present invention when a linear motion part is pulled up.
FIG. 2 is a cross-sectional configuration diagram corresponding to FIG. 1 when the shoulder of the pulling device is pulled up.
FIG. 3 is a perspective view showing the configuration of the bottom carbon heater and heater lifting means.
FIG. 4 is a cross-sectional view corresponding to FIG. 1 showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Silicon single crystal pulling apparatus 11 Chamber 12 Silicon melt 13 Quartz crucible 16 Support shaft 17 Crucible lifting means 18 Side carbon heater 25 Silicon single crystal rod 27 Bottom carbon heaters 27a, 27b, 27c Ring-shaped carbon 41 Heater lifting means 42 Support Rods 42b, 42c, 42d Auxiliary rod 43 Drive gear 46 Drive motor

Claims (3)

A quartz crucible (13) which is fixed to the upper end of the support shaft (16) and is provided in the chamber (11) and stores the silicon melt (12), and the quartz crucible (13) is inserted through the support shaft (16). A crucible raising / lowering means (17) for raising or lowering, a side carbon heater (18) provided in the chamber (11) around the quartz crucible (13), and the lower part of the quartz crucible (13). a chamber (11) bottom carbon heater provided in (27), and a heater elevating means (41) for raising or lowering the bottom carbon heater (27) independently of the crucible elevating means (17) In the silicon single crystal pulling device,
Pulling up a silicon single crystal, wherein the bottom carbon heater (27) is composed of two or more ring-shaped carbons (27a, 27b, 27c) arranged concentrically around the support shaft (16) apparatus. A heater elevating means (41) includes a support rod (42) having a bottom carbon heater (27) attached to the upper end and penetrating through the lower portion of the chamber (11) and having a rack gear formed around the lower portion of the chamber (11). a drive gear meshing with the provided said rack gear (43) is constituted by a motor (46) for driving the driving gear (43), said support rod (42) is ring-like carbon (27a, 27b, 27c) each pulling apparatus of a silicon single crystal according to claim 1 having a provided auxiliary rods (42b, 42c, 42d) to. Side carbon heaters disposed around the quartz crucible (13) and in the chamber (11) below the quartz crucible (13) fixed to the upper end of the support shaft (16) and provided in the chamber (11) (18) and the bottom carbon heater (27) melt the silicon polycrystal to store the silicon melt (12), and the quartz crucible (13) is moved to the crucible lifting means (17) via the support shaft (16). In the method of pulling up the silicon single crystal rod (25) grown from the silicon melt (12) while being raised by
The bottom carbon heater (27) is composed of two or more ring-shaped carbons (27a, 27b, 27c) arranged concentrically around the support shaft (16) ,
A method for pulling a silicon single crystal, wherein the bottom carbon heater (27) is lifted by a heater lifting / lowering means (41) independently of the crucible lifting / lowering means (17) when the silicon single crystal rod (25) is pulled up .

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