JP2012031005A - Method of manufacturing silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a silicon single crystal capable of adjusting a silicon melt surface temperature to a proper seeding temperature by stably measuring the silicon melt surface temperature in a seeding process in manufacturing a silicon single crystal by a horizontal magnetic field application Czochralski method (HMCZ method), remarkably suppressing generation of dislocations during cone growth caused by a failure of drawing or improper drawing as compared with a conventional one, and thereby improving productivity.SOLUTION: In this method of manufacturing a silicon single crystal, a silicon melt surface temperature distribution is previously measured by a two-dimensional thermometer before landing a seed crystal on a silicon melt, a range 19 where the melt surface temperature can be set in a low-temperature region lower than the other regions is identified, and thereafter, when the surface temperature of the silicon melt surface is measured by a radiation thermometer to adjust the melt temperature in landing of the seed crystal on the silicon melt 3 by the measurement temperature, the temperature measurement point by the radiation thermometer is set outside the range 19 that can be in a low-temperature region.

Description

  The present invention relates to a method for producing a silicon single crystal by a horizontal magnetic field application CZ (also referred to as a horizontal magnetic field application CZ; HMCZ) method.

There are various methods for producing a silicon single crystal used for a semiconductor substrate. Among them, the Czochralski method (hereinafter also referred to as “CZ method”) is widely adopted as a rotation pulling method. is there.
Furthermore, the HMCZ method in which the silicon single crystal is pulled up by the CZ method while applying a horizontal magnetic field is widely known for the purpose of reducing the oxygen concentration of the silicon single crystal and easily manufacturing a large-diameter crystal.

Here, in the CZ method, the surface temperature of the silicon melt is measured before seeding, and the output of the heater for forming the silicon melt is adjusted based on the result to match the surface temperature of the silicon melt suitable for seeding. Seeding has been done since then.
Then, after raising the seed crystal by a dash necking method or the like to produce a seed squeezed from the silicon melt, and growing a cone for expanding the diameter to the diameter of the straight body part (constant diameter part) having a predetermined diameter In general, a straight body part for growing a silicon single crystal with a predetermined diameter is formed, and when the single crystal reaches a target length, tail termination is performed at the end part to complete the growth of the single crystal. ing.

By the way, the melt surface temperature suitable for seeding refers to a temperature at which a diaphragm having an appropriate diameter can be produced when producing a diaphragm after seeding.
For example, if the melt surface temperature is too high, the aperture becomes thinner than a predetermined diameter and cannot withstand the weight of the silicon single crystal to be pulled up. Further, when the melt surface temperature is high, the diaphragm is separated from the silicon melt, and the single crystal pulling cannot be continued.
Further, when the melt surface temperature is too low, the diameter of the squeezing is not reduced, and as a result, the dislocations introduced into the seed crystal at the time of seeding are not completely removed, and the single crystal is dislocated.
In these cases (both high temperature and low temperature), the pulling of the single crystal is re-started from seeding, resulting in a decrease in productivity.

  Thus, the surface temperature of the silicon melt at the time of seeding is very important for pulling up the silicon single crystal, and it is required to stably measure the surface temperature of the melt before seeding.

However, in the HMCZ method, it is known that a low temperature range lower in temperature than the surroundings is formed in the direction parallel to the magnetic field lines on the surface of the silicon melt (see Patent Document 1, etc.). The position changes depending on the applied magnetic field strength and the crucible rotation. Further, even when the magnetic field strength and the crucible rotation are constant, the position of the low temperature range on the melt surface is constantly moving within a specific range (low temperature region) and is not stable.
Therefore, depending on the measurement position of the melt surface temperature, the measured value of the melt surface temperature varies depending on whether the temperature in the low temperature region is measured, and as a result, the melt surface temperature at the time of seeding is set to an appropriate temperature. There was a problem that the aperture could not be matched and a diaphragm with an appropriate diameter could not be produced.

  As a solution to this problem, Patent Document 2 proposes that a plurality of radiation thermometers are installed in one pulling device, the temperatures at a plurality of positions on the melt surface are measured, and the average value thereof is used.

Japanese Patent Laid-Open No. 2000-272992 JP 2009-161400 A

  However, since the method described in Patent Document 2 requires a plurality of radiation thermometers, there is a problem that the apparatus cost increases.

There is also a method of using a two-dimensional thermometer using a CCD camera as a thermometer.
However, this two-dimensional thermometer is very expensive compared to the radiation thermometer, and this method also has a problem that the apparatus cost becomes high. In addition, since this two-dimensional thermometer obtains the temperature from the luminance signal output from the CCD camera, the glass window of the lifting device provided for temperature measurement is contaminated with silicon oxide generated from the silicon melt. Unlike the radiation thermometer, the temperature measurement value changes greatly, and there is a problem that the silicon melt surface temperature appropriate for seeding cannot be measured.

  The present invention has been made in view of the above problems, and stably measures the surface temperature of a silicon melt in a seeding process (making a seed crystal settle in a silicon melt) in the production of a silicon single crystal by the HMCZ method. Therefore, it is possible to adjust to the appropriate seeding temperature, and it is possible to greatly suppress dislocations at the time of corn growth due to failure of drawing or inappropriate drawing, which improves productivity. An object of the present invention is to provide a method for producing a silicon single crystal that can be produced.

  In order to solve the above problems, in the present invention, a crucible in a single crystal manufacturing apparatus is filled with a polycrystalline silicon raw material, heated with a heater to melt the polycrystalline silicon raw material, and then a seed crystal is attached to the silicon melt. When a single crystal is grown under the seed crystal, a magnetic field applying device is arranged opposite to the outside of the heater with the crucible in between, and a horizontal magnetic field is applied to the raw material melt. A method for producing a silicon single crystal using the Czochralski method, wherein the surface temperature distribution of the silicon melt is measured in advance by a two-dimensional thermometer before the seed crystal is deposited on the silicon melt. A range in which the melt surface temperature can be a low temperature region lower than other regions is specified, and then the surface temperature of the silicon melt surface is measured by a radiation thermometer, and the silicon of the seed crystal is measured based on the measured temperature. In regulating the melt temperature during deposition solution of a liquid, said to provide a method for manufacturing a silicon single crystal, characterized in that setting the temperature measuring points with a radiation thermometer outside the range that can be the low temperature region.

Thus, when growing a silicon single crystal by the HMCZ method, the measurement position of the surface temperature of the silicon melt at the time of seeding is lower than other regions obtained in advance by measurement with a two-dimensional thermometer. It is set outside the range that can be a low temperature region, seeding is performed based on the surface temperature of the silicon melt measured at that position, and then the single crystal is pulled up.
This prevents the measurement temperature from fluctuating due to the low temperature of the silicon melt surface, which stabilizes the detected value of the melt surface temperature and stabilizes and increases the heater output control compared to the conventional technology. It can be made accurate. The surface temperature of the silicon melt at the time of seeding can be adjusted to an appropriate temperature, and the frequency of occurrence of dislocation failure during squeezing failure and corn growth can be reduced compared to the conventional case. Therefore, productivity can be improved and the cost of the silicon single crystal can be reduced.

Here, it is preferable that the two-dimensional thermometer is removed after specifying a range that can be the low temperature region, and the radiation thermometer is attached at a position where the two-dimensional thermometer is removed.
As a result, the removed two-dimensional thermometer can be used for the measurement of another single crystal manufacturing apparatus, and one silicon melt surface is added to one general pulling apparatus when seeding silicon single crystal pulling. Even with the configuration of a radiation thermometer for temperature measurement, the melt surface temperature can be stably measured. As a result, the apparatus cost can be reduced, the surface temperature of the silicon melt at the time of seeding can be adjusted to an appropriate temperature, and the manufacturing cost of the silicon single crystal can be further reduced.

  As described above, according to the present invention, since the measured value of the silicon melt surface temperature at the time of seeding is stabilized, it can be adjusted to the silicon melt surface temperature appropriate for seeding. And it becomes possible to prevent the failure of drawing and the dislocation at the time of corn growth more reliably than before, so that the productivity can be improved and the manufacturing cost of the silicon single crystal can be reduced. In addition, since it is not necessary to prepare a large number of expensive cameras and the cost of the apparatus can be reduced, the manufacturing cost of the single crystal can be reduced.

It is a figure which shows an example of the outline of the single crystal manufacturing apparatus suitable for enforcing the manufacturing method of the silicon single crystal by HMCZ method. It is a figure which shows typically the temperature distribution of the silicon melt surface of the silicon melt by HMCZ method. It is a figure which shows the outline of the silicon melt surface temperature measurement position of the radiation thermometer in an Example and a comparative example. It is a figure which shows the silicon melt surface temperature measured value in the radiation thermometer in an Example and a comparative example. It is a figure which shows the trouble (throttle failure and corn dislocation) occurrence rate per crystal in Examples and Comparative Examples.

Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
First, an example of an outline of a single crystal manufacturing apparatus suitable for carrying out a method for manufacturing a silicon single crystal by the HMCZ method as in the present invention will be described with reference to FIG.

  As shown in FIG. 1, the appearance of the single crystal manufacturing apparatus 20 is composed of a hollow cylindrical main chamber 9a and a pull chamber 9b communicating therewith, and an electromagnet for applying a horizontal magnetic field outside the main chamber 9a. 12 is installed.

A crucible is disposed at the center of the main chamber 9a.
This crucible has a double structure, and is an inner-layer holding container 1a made of quartz having a bottomed cylindrical shape (hereinafter, simply referred to as “quartz crucible”), and also has a bottomed structure adapted to hold the outside of the quartz crucible 1a. It is composed of a cylindrical graphite outer layer holding container 1b (hereinafter simply referred to as “graphite crucible”). These crucibles are fixed to the upper end of the support shaft 7 so that they can be rotated and lifted.

A resistance heating heater 2 is disposed substantially concentrically outside the quartz crucible 1a and the graphite crucible 1b, and a predetermined weight of polycrystalline silicon raw material charged into the crucible is melted by the heater 2, A silicon melt 3 is formed.
A heat insulating material is applied to the periphery of the heater 2, a heat insulating cylinder 8a is concentrically disposed outside the heater 2, and a heat insulating plate 8b is disposed below the apparatus at the bottom thereof. .

  Further, on the central axis of the crucible filled with the silicon melt 3, a pulling wire (or a pulling shaft, which is rotated at a predetermined speed in the reverse direction or the same direction on the same axis as the support shaft 7, A lifting shaft 4 ”) is provided, and a seed holder 6 is installed at the lower end of the lifting shaft 4, and a seed crystal 5 is held on the seed holder 6. Further, a purge tube 10 is disposed concentrically with the pulling shaft 4, and a collar 11 is provided at the lower end thereof.

Further, a thermometer for measuring the silicon melt surface temperature and a glass window 16 for measuring the melt surface temperature are provided outside the pull chamber 9b or the main chamber 9a. The liquid surface temperature can be measured.
One radiation thermometer 15a for measuring the surface temperature of the silicon melt at the time of seeding is installed outside the glass window 16 for temperature measurement provided in the pull chamber 9b during normal crystal pulling. Yes.

  In order to manufacture a silicon single crystal by the HMCZ method using such a single crystal manufacturing apparatus 20, first, a polycrystalline silicon raw material is introduced into the quartz crucible and heated by the heater 2 to melt the raw material. Thus, the silicon melt 3 is obtained.

When the melt surface temperature is stabilized at a temperature suitable for growing a single crystal, the seed crystal 5 fixed to the seed holder 6 is deposited on the silicon melt 3 in the crucible and the pulling wire is rotated. Winding up and growing a silicon single crystal under the seed crystal.
At this time, a single crystal is applied while applying a horizontal magnetic field (a magnetic field like a magnetic force line 13 centering on the magnetic field center 14) to the silicon melt 3 by a horizontal magnetic field applying device 12 disposed opposite to the heater 2 with a crucible interposed therebetween. Develop.

Here, before seeding the seed crystal 5 on the silicon melt 3, the surface temperature of the silicon melt 3 is measured, and the output of the heater 2 is adjusted based on the result, so that the melt is suitable for seeding. It is necessary to perform seeding after adjusting to the surface temperature.
In the present invention, the temperature of the silicon melt surface is not measured suddenly by the radiation thermometer 15a installed outside the glass window 16 for temperature measurement of the pull chamber 9b, but by the two-dimensional thermometer 15b in advance. The surface temperature distribution of the silicon melt 3 is measured, and the region 18 in which the surface temperature of the silicon melt 3 is lower than the other regions as shown in FIG. A range 19 that can be a low temperature region that can move to a low temperature region is specified. Specifically, the temperature in the direction perpendicular to the magnetic field lines at the same radius from the center of the crucible is measured, and the region where the temperature is lower by 5 ° C. or more is specified as the low temperature region.

  Since the low temperature region 18 on the surface of the silicon melt moves irregularly within a certain range, the two-dimensional distribution measurement of the surface temperature of the silicon melt is performed within a time period of 1 minute to 60 minutes. It is desirable to sufficiently determine the possible range 19.

In addition, it is desirable that the magnetic field strength at the time of measuring the two-dimensional distribution of the silicon melt surface temperature is 2000 gauss or more and 5000 gauss or less where the low temperature region is formed.
Furthermore, it is desirable to carry out with the magnetic field strength used at the time of actual seeding.

  The crucible rotation conditions at the time of measuring the two-dimensional distribution of the silicon melt surface temperature are preferably the crucible rotation conditions used during actual seeding. Other conditions such as gas flow rate, furnace pressure, crucible position, etc. should be the same as in actual seeding.

  When the range 19 that can be a low temperature region is specified by the two-dimensional distribution measurement of the silicon melt surface temperature as described above, the surface temperature of the silicon melt 3 surface is measured by the radiation thermometer 15a, and the seed temperature is measured by the measured temperature. The melt temperature when the crystal 5 is deposited on the silicon melt 3 is adjusted by controlling the output of the heater 2 and the like. At this time, the temperature measurement point 17 by the radiation thermometer 15a is within a range that can be in a low temperature region. 19 outside.

  In addition, as the measurement point 17 of the silicon melt surface temperature moves away from the position (center of the crucible) where the seed crystal 5 is deposited on the melt surface, the measured melt surface temperature and the seed crystal 5 are actually melted. Since the deviation from the temperature at the time of landing on the surface becomes large, the measurement point 17 of the silicon melt surface temperature by the radiation thermometer 15a is lifted from the center of the crucible at a position outside the range 19 which can be a low temperature region. The position is preferably within 1.0 times the radius of the silicon single crystal.

Thus, by setting the measurement position 17 of the silicon melt surface temperature by the radiation thermometer 15a, the measurement value of the melt surface temperature is affected by the low temperature region 18 where the melt surface temperature is lower than other regions. Since it is not received, the measured value of the melt surface temperature is stable.
As a result, it is possible to prevent seeding from being performed at an inappropriate surface temperature of the silicon melt, so that the incidence of squeezing failure and corn dislocation due to seeding should be reduced compared to the conventional case. Thus, the yield of single crystal production can be improved, and the production cost can be reduced.

Here, after specifying the range 19 that can be a low temperature region, the two-dimensional thermometer 15b can be removed, and the radiation thermometer 15a can be attached to the position where the two-dimensional thermometer 15b is removed.
By adopting such a method, if one expensive two-dimensional thermometer 15b is used for measuring the two-dimensional distribution of the silicon melt surface temperature, it can be used in a plurality of single crystal manufacturing apparatuses. Therefore, an appropriate silicon melt surface temperature measurement point 17 for each single crystal manufacturing apparatus can be obtained by the same method using a single two-dimensional thermometer.
Further, when pulling up the silicon single crystal, it is only necessary to install one general radiation thermometer 15a, so that the apparatus cost can be almost the same as the conventional one. Moreover, if it is a radiation thermometer, the influence on the temperature measurement value by the stain | pollution | contamination of the glass window 16 can be suppressed, and the improvement of a manufacturing yield can be achieved.

Thereafter, the seed crystal 5 is pulled up by a dash necking method or the like, a seed drawing is produced from the silicon melt 3, and a cone for expanding the diameter to a diameter of a straight body portion (constant diameter portion) having a predetermined diameter is grown. .
Further, a silicon single crystal is grown with a predetermined diameter. When the single crystal reaches a target length, tail termination is performed at the end portion, and the growth of the single crystal is completed.
By the above method, it becomes the manufacturing method of the silicon single crystal which can suppress the failure of a squeezing and the dislocation of a cone.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
A single crystal manufacturing apparatus as shown in FIG. 1 is used to fill a quartz crucible 1a having an inner diameter of 800 mm with a polycrystalline silicon raw material and melt it with a heater to form a silicon melt 3. Raised.

Here, the magnetic field strength during seeding was 4000 gauss, and the crucible rotation was 0.5 rpm.
In this state, a two-dimensional thermometer 15b was installed outside the glass window 16 provided on the pull chamber 9b. Then, a two-dimensional thermometer 15b was used to measure the two-dimensional distribution of the silicon melt surface temperature inside the purge tube 10 through the glass window 16 for 5 minutes, and a range 19 that could be a low temperature region on the silicon melt surface was determined in advance. At this time, the temperature in the direction perpendicular to the magnetic field lines at the same radius from the center of the crucible was measured, and the region having a temperature lower by 5 ° C. or more was specified as the low temperature region.
A range 19 that can be a low temperature region on the surface of the silicon melt obtained from the measurement result of the two-dimensional thermometer is a range of about ± 50 mm from the crucible center in a direction perpendicular to the magnetic force line 13 passing through the crucible center. I found out.

  Then, the two-dimensional thermometer 15b was removed and the radiation thermometer 15a was installed. At this time, the silicon melt surface temperature measurement position 17 ′ of the radiation thermometer 15 a is outside the range 19 that can be the low temperature region of the silicon melt surface as shown in FIG. 3 and has a radius of 150 mm from the center of the crucible. Set to position.

Then, the relationship between the temperature fluctuation of the silicon melt surface at the temperature measurement position 17 ′ set in this way and the elapsed time was evaluated. The result is shown in FIG. In addition, the vertical axis | shaft of FIG. 4 is a temperature difference with the temperature in time 0 second, and this was made into the temperature fluctuation value.
As shown in FIG. 4, the fluctuation range of the measured value of the silicon melt surface temperature was stable at 2.6 ° C., and the fluctuation range was not more than 1/3 times the temperature fluctuation range of the comparative example described later.

FIG. 5 shows the occurrence rate of trouble (re-drawing and dislocation of cone) per crystal in the example and the comparative example described later.
As shown in FIG. 5, the redrawing of the squeezing and the dislocation conversion rate of the cone were 0.2 times / piece, which was improved to 1/6 times or less of the comparative example.

(Comparative example)
In the embodiment, the melt temperature distribution on the surface of the silicon melt was not measured by the two-dimensional thermometer 15a, and the temperature measurement position on the radiation thermometer was changed to the position 17 ″ shown in FIG. The temperature variation on the surface of the silicon melt was measured under the same conditions, and the seeding process was performed in the same manner.
Then, the relationship between the temperature fluctuation of the silicon melt surface at the temperature measurement position 17 ″ at this time and the elapsed time was evaluated. The result is shown in FIG. FIG. 5 shows the occurrence rate of trouble (redrawing and relocation of cones) per crystal in the comparative example.

As shown in FIG. 4, the fluctuation range of the measured value of the melt surface temperature of the silicon melt was 8.6 ° C., which was more than three times that of the example.
Also, as shown in FIG. 5, the redrawing and the dislocation conversion rate of the cone were 1.3 times / piece, which was 6 times or more that of the example.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1a ... Quartz crucible, 1b ... Graphite crucible, 2 ... Heater, 3 ... Silicon melt, 4 ... Pulling shaft, 5 ... Seed crystal, 6 ... Seed holder, 7 ... Supporting shaft, 8a ... Insulating cylinder, 8b ... Insulating plate, 9a ... Main chamber, 9b ... Pull chamber, 10 ... Purge tube, 11 ... Collar, 12 ... Electromagnet for horizontal magnetic field, 13 ... Magnetic field line, 14 ... Magnetic field center, 15a ... Radiation thermometer, 15b ... Two-dimensional thermometer, 16 ... Glass window, 17, 17 ', 17''... Silicon melt surface temperature measurement point,
18 ... low temperature region, 19 ... range that can be a low temperature region,
20: Single crystal manufacturing apparatus.

Claims (2)

A crucible in a single crystal manufacturing apparatus is filled with polycrystalline silicon raw material, heated with a heater to melt the polycrystalline silicon raw material, and then seeded into the silicon melt and a single crystal below the seed crystal. When a single crystal of silicon using a horizontal magnetic field application Czochralski method is applied, a magnetic field application device is disposed opposite to the outside of the heater with the crucible interposed therebetween, and a horizontal magnetic field is applied to the raw material melt. A manufacturing method comprising:
Before the seed crystal is deposited on the silicon melt, the silicon melt surface temperature distribution is measured in advance by a two-dimensional thermometer, and the melt surface temperature can be in a low temperature region that is lower than other regions. And then measuring the surface temperature of the silicon melt surface with a radiation thermometer and adjusting the melt temperature at the time of landing of the silicon melt on the seed crystal by the measured temperature. A method for producing a silicon single crystal, characterized in that a temperature measurement point by a thermometer is set outside the range that can be the low temperature region.   2. The silicon single crystal production according to claim 1, wherein the two-dimensional thermometer is removed after the range that can be the low temperature region is specified, and the radiation thermometer is attached at a position where the two-dimensional thermometer is removed. Method.

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