JPH11263692A - Method for pulling up silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the generation of grown-in defect in the single crystal bar suppressible by reducing the density of point defects within the crystal of a single crystal bar under pulling-up operation. SOLUTION: A carbon heater is placed in such a way that a quartz crucible 13 is encircled with the heater and a silicon melt 12 reserved in the quartz crucible 13 is heated with the carbon heater and further, a silicon single crystal bar 15 is pulled up from the silicon melt 12 in such a way that each isothermal surface within the crystal of the single crystal bar 15 in the region of 1,300 to 1,100 deg.C of the temp. distribution within this crystal is reversed from an upwardly convex state to a downwardly convex state by a temp. distribution reversion means 26 surrounding the periphery of the silicon single crystal bar 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for pulling and growing a silicon single crystal.

[0002]

2. Description of the Related Art Conventionally, as a silicon single crystal pulling apparatus, as shown in FIG. 7, a quartz crucible 3 in which a silicon melt 2 is stored is housed in a chamber, and the outer peripheral surface of a silicon single crystal rod 5 is There is disclosed a pulling device (Japanese Patent Publication No. 57-40119) in which a heat shielding member 6 is inserted between the inner peripheral surface of the crucible 3 and the silicon single crystal rod 5 so as to surround the same. In this device, the cone portion 7 whose diameter decreases as the heat shielding member 6 faces downward, the outer peripheral edge is connected to the lower end of the cone portion 7 and extends horizontally, and the inner peripheral edge is near the outer peripheral surface of the silicon single crystal rod 5 It has a ring portion 8 that reaches, and a flange portion (not shown) whose inner peripheral edge is connected to the upper end of the cone portion 7 and extends horizontally, and whose outer peripheral edge reaches the upper surface of a heat retaining cylinder (not shown). The heat shielding member 6 is fixed by placing the flange portion on the upper surface of the heat retaining cylinder.

In the pulling apparatus constructed as described above, when the silicon single crystal rod 5 is pulled up from the silicon melt 2, the liquid level of the silicon melt 2 gradually decreases, and the inner peripheral wall of the quartz crucible 3 is exposed. Radiation heat from the exposed inner peripheral wall of the quartz crucible 3 is directed to the outer peripheral surface of the silicon single crystal rod 5, but the radiant heat is blocked by the heat shielding member 6 and does not reach the outer peripheral surface of the silicon single crystal rod 5. As a result, the solidification of the silicon single crystal rod 5 during pulling is not delayed, and the silicon single crystal rod 5 is quickly cooled.

[0004]

However, in the pulling apparatus described in the above-mentioned conventional Japanese Patent Publication No. 57-40119, the temperature distribution in the crystal of the silicon single crystal rod being pulled from the silicon melt, that is, the isothermal surface Is in an upwardly convex state over the entire length as shown by the dashed line in FIG. For this reason, the slope diffusion of point defects (interstitial silicon atoms or vacancies) in the crystal always points in the direction of the solid arrow in FIG. 7, that is, diagonally downwards from the outer peripheral surface side in the crystal of the silicon single crystal rod.
Point defects continue to flow into the crystal of the silicon single crystal rod being pulled from the outer peripheral surface thereof. As a result, if the silicon single crystal rod is pulled up and cooled as it is, it is solidified while the point defect concentration is high, and it is difficult to suppress the generation of glow-in defects in the silicon single crystal rod. There was a problem. Here, the slope diffusion is synonymous with the thermal drift movement, and means that the point defect moves from the low temperature side to the high temperature side orthogonal to the isothermal surface. An object of the present invention is to provide a method for pulling a silicon single crystal, which can suppress the occurrence of glow-in defects in a silicon single crystal rod by reducing the concentration of point defects in the crystal of the silicon single crystal rod during pulling. It is in.

[0005]

The invention according to claim 1 is
As shown in FIGS. 1 and 2, the silicon melt 12 stored in the quartz crucible 13 is heated by a carbon heater 18 provided so as to surround the quartz crucible 13, and the silicon melt 1 is heated.
This is an improvement in the method of pulling the silicon single crystal rod 15 from 2. The characteristic configuration is that the temperature distribution in the crystal of the silicon single crystal rod 15 is in a temperature range of 1300 to 1100 ° C., and the temperature distribution inversion means 26 surrounding the periphery of the silicon single crystal rod 15 causes The silicon single crystal rod 15 is being pulled up so that the isothermal surface in the crystal is inverted from the upwardly convex state to the downwardly convex state.

The glow-in defect generated in the crystal of the silicon single crystal rod 15 is considered to be one of the causes of a point defect flowing into the crystal from the outer peripheral surface of the silicon single crystal rod 15 when pulled from the silicon melt 12. Have been. In the method for pulling a silicon single crystal according to the first aspect, the isothermal surface in the crystal of the silicon single crystal rod 15 pulled from the silicon melt 12 is raised upward when the temperature distribution inverting means 26 reaches a predetermined height. Is inverted from the state shown in FIG. When the silicon single crystal rod 15 is gradually pulled up from the silicon melt 12 and reaches a position above the predetermined height and the isothermal surface in the crystal becomes convex upward, the slope diffusion of point defects in the crystal increases in the crystal. From the outer peripheral surface side, point defects are removed from the outer peripheral surface, and the absolute amount of point defects in the crystal of the silicon single crystal rod 15 can be reduced.

The invention according to claim 2 is the invention according to claim 1, and furthermore, as shown in FIGS. 1 and 2, the temperature distribution inversion means 26 surrounds the upper part of the silicon single crystal rod 15 being pulled. Upper member 27, a lower member 28 surrounding the lower portion of the silicon single crystal rod 15 being pulled, and a lower member 2
8 and a plurality of connecting members 29 for connecting the upper member 27 to the upper member 27 at a predetermined interval. In the method for pulling a silicon single crystal according to claim 2,
When the silicon single crystal rod 15 is pulled up from the silicon melt 12 and reaches an open portion between the lower member 28 and the upper member 27, the radiant heat from the carbon heater 18 is irradiated on the silicon single crystal rod 15, and the silicon single crystal rod 15 is irradiated. The rod 15 is kept warm, and the isothermal surface in the crystal of the silicon single crystal rod 15 is inverted from an upwardly convex state to a downwardly convex state. In this part, the temperature of the silicon single crystal rod 15 is about 1300 ° C. to about 120 ° C.
Lower to 0 ° C. When the silicon single crystal rod 15 is further pulled up and reaches the portion surrounded by the upper member 27, the radiant heat from the carbon heater 18 is applied to the upper member 27.
However, since the radiant heat from the silicon melt 12 is reflected on the upper member 27 and is irradiated on the silicon single crystal rod 15, the diffusion of point defects in the crystal on the slope is promoted. As a result, since the slope diffusion of point defects in the crystal is obliquely downward from the inside of the crystal toward the outer peripheral surface, most of the point defects in the crystal escape from the outer peripheral surface of the silicon single crystal rod, and the silicon single crystal rod The absolute amount of point defects in the 15 crystals can be reduced.

A third aspect of the present invention is the invention according to the first aspect, further comprising an auxiliary heater surrounding the periphery of the silicon single crystal rod 15 being pulled by the temperature distribution inverting means 66 as shown in FIG. It is characterized by being. In the method for pulling a silicon single crystal according to the third aspect, when the silicon single crystal rod is pulled up and reaches a portion surrounded by the auxiliary heater 66, the temperature is kept by the radiant heat of the auxiliary heater 66 at this portion, and the silicon single crystal rod is held. The isothermal surface in the crystal of the crystal rod 15 is inverted from the upwardly convex state to the downwardly convex state. When the silicon single crystal rod 15 is further pulled up and reaches above the auxiliary heater 66, the slope diffusion of the point defect in the crystal is directed obliquely downward from the crystal to the outer peripheral surface side. Most of the material comes off the outer peripheral surface of the silicon single crystal rod 15, and the absolute amount of point defects in the crystal can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, the silicon single crystal rod 15 is pulled by the pulling device 10 into the silicon melt 12.
Pulled up from. The chamber 11 of the pulling device 10
Inside, a quartz crucible 13 for storing the silicon melt 12 is provided, and the outer surface of the quartz crucible 13 is
4 coated. 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 (FIG. 2). Although the crucible driving means 17 is not shown, the quartz crucible 1
3 has a first rotation motor for rotating 3 and a lifting / lowering motor for raising / lowering the quartz crucible 13, and these motors can rotate the quartz crucible 13 in a predetermined direction,
It can be moved up and down. The outer peripheral surface of the quartz crucible 13 is surrounded by a carbon heater 18 at a predetermined interval from the quartz crucible 13, and the carbon heater 18 is surrounded by a heat retaining tube 19. The carbon heater 18 heats and melts the high-purity polycrystalline silicon charged in the quartz crucible 13 to form the silicon melt 12.

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 includes a pulling head (not shown) rotatably provided at the upper end of the casing 21 in a horizontal state, a second rotation motor (not shown) for rotating the head, and a quartz crucible 13 from the head.
A wire cable 23 suspended toward the center of rotation of
And a pulling motor (not shown) provided in the head for winding or feeding the wire cable 23. At the lower end of the wire cable 23 is attached a seed crystal 24 for dipping in the silicon melt 12 and pulling up the silicon single crystal rod 15.

A temperature distribution inversion means 26 surrounding the silicon single crystal rod 15 is provided between the outer peripheral surface of the silicon single crystal rod 15 and the inner peripheral surface of the quartz crucible 13 (FIGS. 2 to 5). The temperature distribution reversing means 26 includes an upper member 27 surrounding the upper part of the silicon single crystal rod 15 pulled up from the silicon melt 12, a lower member 28 surrounding the lower part of the silicon single crystal rod 15, and an upper member 27 are provided with a plurality of connecting members 29 connected at predetermined intervals. The upper member 27 has a straight cylindrical portion 27a and an upper cone portion 2 whose lower end is connected to the lower end of the straight cylindrical portion 27a and whose diameter decreases as going upward and is accommodated in the straight cylindrical portion 27a.
7b. A flange portion 27c extending outward in a substantially horizontal direction is continuously provided at an upper end of the straight tube portion 27a, and the temperature distribution reversing means 26 is fixed by mounting the flange portion 27c on the heat retaining tube 19. The lower member 28 is formed in a cone shape whose diameter becomes smaller as it goes downward, and the lower end of the lower member 28 is located above the surface of the silicon melt 12 at an interval. The inclination angle of the upper cone portion 27b and the lower member 28 is set in a range of 30 to 60 degrees with respect to a horizontal plane, and preferably 45 degrees.

In this embodiment, the connecting member 29 is 3
The upper end of each connecting member 29 is connected to an upper end of an upper cone portion 27b via a bolt 33a and a nut 33b (FIG. 3), and the lower end is connected to the lower end of a lower member 28. It has a lower connector 32 connected via bolts 34a and nuts 34b (FIG. 3) (FIGS. 2 to 5). Upper end of upper connector 31 and lower connector 3
2 are bent in a substantially V-shape, and the lower end of the upper connecting part 31 and the upper end of the lower connecting part 32 are connected with these connecting parts 3.
A plurality of first and second through holes 31a and 32a (FIG. 3) are formed at predetermined intervals in the longitudinal direction of the first and second holes 32, respectively. Bolts 35 are selectively inserted into these through holes 31a and 32a.
The lower end of the upper connecting tool 31 and the upper end of the lower connecting tool 32 are connected by inserting the nut a into the nut 35b (FIG. 3) and screwing it. In this way, by forming the entire length of the connecting member 33 so as to be changeable, the interval between the upper member 27 and the lower member 28 can be adjusted. The upper member 27, the lower member 28, and the connecting member 29 are preferably formed of Mo, W, C, or the like.

A gas supply / discharge means 36 for supplying an inert gas to the silicon single crystal rod side of the chamber 11 and discharging the inert gas from the inner peripheral surface side of the crucible of the chamber 11 is connected to the chamber 11 (see FIG. 1). (Fig. 2). The gas supply / discharge means 36 has one end connected to the peripheral wall of the casing 21 and the other end connected to a supply pipe 37 connected to a tank (not shown) for storing the inert gas, and one end connected to the lower wall of the chamber 11. Discharge pipe 3 whose other end is connected to a vacuum pump (not shown)
8 is provided. The supply pipe 37 and the discharge pipe 38 are provided with first and second flow control valves 41 and 42 for adjusting the flow rate of the inert gas flowing through these pipes 37 and 38, respectively.

Output shaft of pulling motor (not shown)
Is provided with a rotary encoder (not shown), and the crucible driving means 17 includes a silicon melt 1 in the quartz crucible 13.
A weight sensor (not shown) for detecting the weight of
6 linear encoder (not shown) for detecting the vertical position
Are provided. The respective detection outputs of the rotary encoder, the weight sensor and the linear encoder are connected to control inputs of a controller (not shown), and the control outputs of the controller are connected to a pulling motor of the pulling means 22 and a lifting motor of the crucible driving means, respectively. You. Further, the controller is provided with a memory (not shown). The memory has a wire cable 2 for detecting output of the rotary encoder.
3 is stored as the first map, and 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. Is done. The controller always keeps the liquid level of the silicon melt 12 in the quartz crucible 13 at a constant level based on the detection output of the weight sensor,
It is configured to control the motor for lifting and lowering of the crucible driving means 17.

When the silicon single crystal rod 15 is pulled up by using the pulling apparatus 10 configured as described above, and reaches the portion surrounded by the lower member 28 (portion of FIG. 1), the lower portion of the silicon single crystal rod 15 is pulled down. Radiation heat from the carbon heater 18 and the silicon melt 12 is blocked by the outer peripheral surface of the member 28, so that the outer peripheral surface of the silicon single crystal rod 15 is not irradiated,
Since the silicon single crystal rod 15 is rapidly cooled from about 1410 ° C. to about 1300 ° C., the growth rate of the crystal of the silicon single crystal rod 15 increases. At this time, the temperature distribution in the crystal of the silicon single crystal rod 15 is high at the center and low at the periphery on the same horizontal plane, that is, since the isothermal surface in the crystal is convex upward, the point defect in the crystal is Since the slope diffusion is directed obliquely downward from the outer peripheral surface of the silicon single crystal rod 15 to the inside of the crystal as shown by the broken arrow in FIG. 1, point defects flow into the crystal from the outer peripheral surface of the silicon single crystal rod 15. The heat flux (heat flow vector) in the silicon single crystal rod 15 is orthogonal to the isothermal surface and goes from the higher temperature to the lower temperature, that is, in the direction opposite to the direction of the slope diffusion of the point defect in the crystal. Become.

When the silicon single crystal rod 15 is further pulled up and reaches an open portion between the lower member 28 and the upper member 27 (portion in FIG. 1), the outer peripheral surface of the silicon single crystal rod 15 is applied from the carbon heater 18 to the outer peripheral surface. Irradiating the silicon single crystal rod 15 to keep the temperature constant, the temperature distribution in the crystal of the silicon single crystal rod 15 is lower at the center and higher at the periphery on the same horizontal plane, and the isothermal surface in the crystal is higher. The state is inverted from the convex state to the convex state. In this portion, the temperature of the silicon single crystal rod 15 drops to about 1200 ° C.

When the silicon single crystal rod 15 is further pulled up and reaches the portion surrounded by the upper member 27 (FIG. 1).
Portion), the radiant heat from the carbon heater 18 is blocked by the outer peripheral surface of the upper member 27.
The radiant heat from 2 is reflected on the inner peripheral surface of upper member 27 and irradiated on the outer peripheral surface of silicon single crystal rod 15 as shown by the two-dot chain line arrow in FIG. In this portion, the temperature of the silicon single crystal rod 15 drops to about 1200 ° C. to about 1100 ° C., which is an optimum temperature gradient that promotes the diffusion of point defects in the crystal on the slope. In this portion, since the isothermal surface in the crystal of the silicon single crystal rod 15 is convex downward, the slope diffusion of the point defect in the crystal is limited from the inside of the crystal to the outer periphery as shown by a thick solid arrow in FIG. Face diagonally downward toward the surface. As a result, most of the point defects in the crystal escape from the outer peripheral surface of the silicon single crystal rod 15, and the absolute amount of the point defects in the crystal can be reduced. The occurrence of defects can be suppressed.

FIG. 6 shows a second embodiment of the present invention.
6, the same reference numerals as those in FIG. 2 indicate the same parts. In this embodiment, an auxiliary heater surrounding the periphery of the silicon single crystal rod 15 being pulled from the silicon melt 12 is used as the temperature distribution inversion means 66. When the liquid level of the silicon melt 12 is lowered and the inner peripheral wall of the quartz crucible 13 is exposed, the auxiliary heater 66 controls the liquid level of the silicon melt 12 so as not to be affected by the radiant heat from the exposed inner peripheral wall. It is provided at a high position relatively far away from the vehicle. A portion between the surface of the silicon melt 12 and the lower end of the auxiliary heater 66 in the outer peripheral surface of the silicon single crystal rod 15 is surrounded by a heat shielding member (not shown). This heat shielding member is provided to shorten the melting time of the silicon polycrystal as a raw material and to make the flow of the inert gas in the chamber 11 constant. Except for the above, the configuration is the same as that of the first embodiment.

The silicon single crystal rod 15 is pulled up using the pulling apparatus 10 constructed as described above, and the silicon single crystal rod 15 is heated to about 1300 ° C. from the surface of the silicon melt 12 to the lower end of the auxiliary heater 66. Is cooled.
The silicon single crystal rod 15 is further pulled up and the auxiliary heater 6
When reaching the portion surrounded by 6, the portion is kept warm by the radiant heat of the auxiliary heater 66. At this time, the temperature distribution in the crystal of the silicon single crystal rod 15, that is, the isothermal surface in the crystal is inverted from an upwardly convex state to a downwardly convex state. In this portion, the temperature of the silicon single crystal rod 15 drops to about 1200 ° C.

When the silicon single crystal rod 15 is further pulled up and reaches a position above the auxiliary heater 66, the temperature of the silicon single crystal rod 15 further decreases, and the silicon single crystal rod 15 becomes approximately 1
Slope diffusion of point defects in the crystal is promoted during the fall from 200 ° C. to about 1100 ° C. At this time, silicon single crystal rod 1
Since the isothermal surface in the crystal of No. 5 is convex downward, the slope defect of the point defect in the crystal is directed obliquely downward from inside the crystal toward the outer peripheral surface side. As a result, most of the point defects in the crystal escape from the outer peripheral surface of the silicon single crystal rod 15, and the absolute amount of the point defects in the crystal can be reduced. The occurrence of defects can be suppressed.

[0021]

As described above, according to the present invention, the temperature distribution in the crystal of the silicon single crystal rod is 1300 to 110.
In a temperature range of 0 ° C., the silicon is so arranged that the isothermal surface in the crystal of the silicon single crystal rod is inverted from an upwardly convex state to a downwardly convex state by temperature distribution inversion means surrounding the periphery of the silicon single crystal rod. Since the single crystal rod is pulled up, after the isothermal surface in the crystal of the silicon single crystal rod is inverted to a downwardly convex state by the temperature distribution inverting means, the slope diffusion of point defects in the crystal causes the crystal of the silicon single crystal rod to change. Since the diagonal surface is directed obliquely downward from the inside to the outer peripheral side, point defects are removed from the outer peripheral surface of the silicon single crystal rod, and the absolute amount of point defects in the crystal can be reduced. Can be suppressed.

Further, the upper member of the temperature distribution inverting means surrounds the upper part of the silicon single crystal rod being pulled up, the lower member surrounds the lower part of the silicon single crystal rod being pulled up, and the lower member is joined by a plurality of connecting members. Is connected to the upper member at a predetermined interval, and when the silicon single crystal rod is pulled up from the silicon melt and reaches an open portion between the lower member and the upper member, silicon is irradiated by radiant heat from the carbon heater. The single crystal rod is kept warm, and the isothermal surface in the crystal of the silicon single crystal rod is inverted from an upwardly convex state to a downwardly convex state. When the silicon single crystal rod is further pulled up and reaches the portion surrounded by the upper member, the radiant heat from the carbon heater is blocked by the upper member. , The diffusion of point defects in the crystal on the slope is promoted. As a result, since the slope diffusion of point defects in the crystal is obliquely downward from the inside of the crystal toward the outer peripheral surface, most of the point defects in the crystal escape from the outer peripheral surface of the silicon single crystal rod, and the silicon single crystal rod , The absolute amount of point defects in the crystal can be reduced, and the occurrence of glow-in defects in the crystal due to this can be suppressed.

Further, if an auxiliary heater surrounding the pulling silicon single crystal rod is used as the temperature distribution inverting means, when the silicon single crystal rod is pulled up and reaches the portion surrounded by the auxiliary heater, the auxiliary heater is used. And the isothermal surface in the crystal of the silicon single crystal rod is inverted from an upwardly convex state to a downwardly convex state. When the silicon single crystal rod is further pulled up and reaches above the auxiliary heater, the slope diffusion of the point defects in the crystal is directed obliquely downward from the inside of the crystal toward the outer peripheral surface. Can escape from the outer peripheral surface of the silicon single crystal rod, and the absolute amount of point defects in the crystal can be reduced. As a result, the same effect as above can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram showing an isothermal surface of a silicon single crystal rod during pulling according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram of the silicon single crystal pulling apparatus.

FIG. 3 is an enlarged sectional view of a portion A in FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a perspective view of a main part including a temperature distribution reversing means of the pulling device.

FIG. 6 is a cross-sectional configuration diagram corresponding to FIG. 2 showing a second embodiment of the present invention.

FIG. 7 is a sectional view showing a conventional example and corresponding to FIG.

[Explanation of symbols]

 12 Silicon Melt 13 Quartz Crucible 15 Silicon Single Crystal Rod 18 Carbon Heater 26 Temperature Distribution Reversing Means 27 Upper Member 28 Lower Member 29 Connecting Member 66 Auxiliary Heater (Temperature Distribution Reversing Means)

Claims (3)

[Claims] The silicon melt (12) stored in the quartz crucible (13) is heated by a carbon heater (18) provided so as to surround the quartz crucible (13). In the method of pulling a silicon single crystal rod (15) from the above, the temperature distribution in the crystal of the silicon single crystal rod (15) is 130
In a temperature range of 0 to 1100 ° C., the silicon single crystal rod (1
5) By the temperature distribution inversion means (26, 66) surrounding the periphery of
A silicon single crystal, wherein the silicon single crystal rod (15) is pulled up so that an isothermal surface in the crystal of the silicon single crystal rod (15) is inverted from an upwardly convex state to a downwardly convex state. How to raise. 2. An upper member (27) surrounding the upper part of the silicon single crystal rod (15) being pulled by the temperature distribution inverting means (26),
A lower member (28) surrounding the lower portion of the silicon single crystal rod (15) being pulled up, and the lower member (28) being connected to the upper member (2
A plurality of connecting members (29) to be connected at predetermined intervals to (7)
The method for pulling a silicon single crystal according to claim 1, comprising: 3. The method for pulling a silicon single crystal according to claim 1, wherein the temperature distribution inverting means is an auxiliary heater surrounding the periphery of the silicon single crystal rod being pulled.