JPH0891983A - Method for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE: To prevent both an oxidation induced stacking fault (OSF) and an oxygen deposit from being caused in a silicon wafer in heat treatment by lowering the temperature of a silicon single crystal ingot during the pulling up under specific conditions. CONSTITUTION: This method for pulling up a silicon single crystal is to house a silicon melt 7 in a quartz crucible 4 supported on a rotating shaft 3 under the interior of an apparatus 2 for pulling up an ingot, dipping a seed crystal 9 attached to the tip of a pulling up shaft 8 in the melt while heating the silicon melt with a heater 6 installed between a heat insulating unit 5 and the crucible 4, pull up the silicon single crystal ingot 11 at 0.6-2.0mm/min pulling up speed, passing a current through an auxiliary heater 10 at a temperature within the range of 1130-1070 deg.C in the temperature lowering temperature distribution, reduce the temperature lowering speed to 0-0.3 deg.C/min and keep the temperature lowering rate for at least 10min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pulling a silicon (Si) single crystal ingot with extremely few defects.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 8, a silicon single crystal ingot 1 is pulled up from a silicon melt 7 held in a quartz crucible 4 supported by a rotating shaft 3 in a lower portion of an ingot pulling apparatus 2. . At the same time, the silicon single crystal ingot 1 has a heater 6 provided between the heat retaining body 5 and the crucible 4.
It is manufactured by immersing the seed crystal 9 attached to the tip of the pulling shaft 8 in the silicon melt 7 heated by, and pulling it at a speed of, for example, 1 mm / min while rotating the pulling shaft 8. Therefore, when the length of the silicon single crystal ingot immediately after pulling is, for example, 30 cm, it has a temperature drop distribution from about 1400 ° C. at the lower end to about 800 ° C. at the upper end, and the pulling speed is the same as above. If it is about 1 mm / min, the growing time will be about 300 minutes (about 5
It takes time).

[0003]

However, since the pulled silicon single crystal ingot contains supersaturated oxygen, there are a large number of nuclei that form oxygen precipitates. In the device step, when various high temperature treatments are applied to the wafer manufactured from the silicon single crystal ingot, oxygen precipitates are formed on the wafer centering on the nucleus, and the oxygen precipitates are formed. The formation of dislocations and stacking faults (OSF: oxidation indu
ced stacking fault), and these defects cause the breakdown voltage of semiconductor devices and
It causes serious deterioration of characteristics such as reduction of carrier lifetime. In order to solve this point, the normal pulling speed is 0.4
By reducing the speed to about mm / min, the generation of nuclei that are the source of oxygen precipitates and stacking faults is suppressed. However, when the silicon single crystal ingot is pulled at a pulling rate of about 0.4 mm / min, there is a problem that productivity is poor.

An object of the present invention is to provide a method for pulling a silicon single crystal that does not cause stacking faults and oxygen precipitates that appear in a silicon wafer when heat-treated in a semiconductor device process when pulling a silicon single crystal ingot. It is in. Another object of the present invention is to provide a method for pulling a silicon single crystal with high productivity.

[0005]

As shown in FIG. 7, the present invention is an improvement of a method for pulling a silicon single crystal ingot 11 from a silicon melt 7 held in a crucible 4 in a pulling device 12. Its characteristic structure is 0.6 to 2.0 m.
1130 to 1070 of the temperature drop distribution of the silicon single crystal ingot 11 being pulled up at a pulling rate of m / min
In the temperature range of 0 ° C, the temperature decrease rate is reduced to 0 to 0.3 ° C / minute and the temperature decrease rate is maintained for at least 10 minutes so that stacking faults and oxygen precipitates do not occur in the silicon wafer when heat-treated after pulling. Is to

The present invention will be described in detail below. As a means for reducing the temperature lowering rate of the present invention, there is a method in which the periphery of the silicon single crystal ingot which is being pulled up is wrapped with a heat insulating material without slowing down the pulling rate, or is heated by an auxiliary heater. The temperature measuring method for setting the temperature lowering rate is not particularly limited as long as the object of the present invention is achieved, but this method includes, for example, a thermocouple attached to a silicon single crystal ingot as shown in Example 1. There is a method based on temperature measurement data, or a method of measuring the temperature of a silicon single crystal ingot which is being pulled up by a non-contact type infrared temperature sensor.

The pulling speed of the present invention is 0.6 to 2.0 mm.
/ Minute range. If it is less than 0.6 mm / min, the productivity is inferior, and if it exceeds 2.0 mm / min, there is a problem that it is difficult to grow a single crystal. Further, it is empirically determined from various experimental results that the cooling rate is reduced to 0 to 0.3 ° C./min in the temperature range of 1130 to 1070 ° C. in the temperature drop distribution of the silicon single crystal ingot. 1130-10
Even if the temperature decrease rate at 70 ° C exceeds 0.3 ° C / minute, the temperature range in which the temperature decrease rate is reduced to 0 to 0.3 ° C / minute is 113.
If the temperature exceeds 0 ° C. or is lower than 1070 ° C., it is not possible to sufficiently suppress the generation of stacking faults and oxygen precipitates in the silicon wafer when the silicon single crystal ingot is pulled and then heat-treated. The temperature range is 1120 to 10
80 ° C. is more preferable. Further, the temperature decrease rate of 0 ° C./min means that the temperature decrease is stopped and maintained at the corresponding temperature. Further, the holding time of the temperature decreasing rate is at least 10 minutes, preferably 10 minutes or more and 15 hours. From the viewpoint of improving productivity and energy consumption, 10 minutes or more and less than 3 hours is more preferable, and 1 hour or more and 2 hours or less is further preferable.

[0008]

In the temperature drop distribution of the silicon single crystal ingot which is being pulled up at a pulling rate of 0.6 to 2.0 mm / min, the temperature lowering rate is 0 to 0 in the temperature range of 1130 to 1070 ° C.
Decelerate to 0.3 ° C / min to reduce the temperature decrease rate to at least 10
The technical reason why the occurrence of defects is remarkably suppressed by holding for a minute is not yet fully understood, but it is presumed as follows. It is generally considered that point defects such as interstitial silicon and vacancies are involved in the formation of nuclei of bulk micro defects (BMD) during pulling. If these point defects are held at a high temperature of 1300 ° C. for about 2 hours during pulling, diffusion out of the crystal and pair annihilation of interstitial silicon and vacancies occur. It is believed that this reduces the point defects and prevents BMD formation.
On the other hand, it is considered that the lower the temperature, the slower the diffusion of these point defects and the formation of a complex by supersaturated oxygen, resulting in the point defects becoming relatively stable. The temperature is stopped at 1130 to 1070 ° C, which is a feature of the present invention, or the temperature is lowered at an extremely low speed.
If kept near 00 ° C, the above complex becomes unstable,
It is considered that the pair annihilation of interstitial silicon and vacancies occurs again and the point defects are reduced, and stable nuclei are not formed by the subsequent low temperature thermal history.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. <Example 1> First, FIG. 8 is shown in order to investigate in which temperature range the temperature of the silicon single crystal ingot being pulled up slows down the factor of stacking faults and oxygen precipitates. The temperature distribution of the silicon single crystal ingot itself being pulled by the ingot pulling apparatus 2 was examined.
For this reason, a hole having a depth of 400 mm was made in parallel with the central axis of a silicon single crystal ingot having a diameter of 5 inches and a length of 800 mm, which had been grown in the apparatus 2, and a plurality of thermocouples were equally spaced in the hole. I installed it. The ingot to which this thermocouple was attached was set in the pulling device 2, and the ingot was heated by the heater 6 while holding the silicon melt under the normal heating conditions for pulling. Then, the temperature was measured with a thermocouple while gradually melting the silicon single crystal ingot. FIG. 4 shows the temperature distribution of the silicon single crystal ingot 1 in the pulling device 2 of FIG. 8 obtained from the detection results of a plurality of thermocouples. In FIG. 4, the horizontal axis represents the length from the bottom (0 mm) to the top (800 mm) of the ingot 1, in other words, the distance from the silicon melt surface,
The vertical axis represents the temperature of the ingot itself corresponding to each distance.

When the ingot pulling apparatus 2 shown in FIG. 8 is used to pull at a constant velocity of about 0.6 to 0.8 mm / min, ring-shaped stacking faults occur at a high density when formed into a silicon wafer. Since it is known that in Example 1 and Comparative Example 1 below, at a constant velocity of 0.65 mm / min,
It was examined whether a ring-shaped stacking fault disappeared or occurred when a silicon single crystal ingot was newly pulled by using the ingot pulling apparatus 2. That is, in this example, a silicon single crystal ingot having a diameter of 5 inches was pulled at 0.65 mm / min in the apparatus 2, and when the length of the constant diameter portion of the ingot reached 450 mm, pulling was stopped while continuing heating with the heater. , Held there for 2 hours. Then, the silicon single crystal ingot 1 having a diameter of 5 inches and a length of 800 mm was grown again at a constant rate of 0.65 mm / min. The grown recon single crystal ingot is taken out from the apparatus 2, sliced in parallel to the pulling direction at the center of the ingot, and half of the sliced sample is heat-treated at 1100 ° C. for 1 hour in a wet oxygen (wetO ₂ ) atmosphere. Sample A1 was obtained. The other half is dry oxygen (d
Another sample B1 was obtained by heat treatment at 1000 ° C. for 40 hours in a ryO ₂ ) atmosphere.

<Comparative Example 1> A silicon single crystal ingot was pulled at a constant velocity of 0.65 mm / min using the pulling apparatus 2 shown in FIG. . 800m long with a diameter of 5 inches
Take out the silicon single crystal ingot 1 of m from the device 2,
Then, in the same manner as in Example 1, a slice was sliced parallel to the pulling direction at the center of the ingot, and half of the sliced sample was heat-treated at 1100 ° C. for 1 hour in a wet oxygen (wetO ₂ ) atmosphere to obtain a sample A1 ′. The remaining half was subjected to 10 in the dry oxygen (dryO ₂ ) atmosphere as in Example 1.
Another sample B1 ′ was obtained by heat treatment at 00 ° C. for 40 hours. FIG. 6 shows the heat history of the ingot when the whole ingot is pulled at a constant speed of 0.65 mm / min.
In FIG. 6, the distance on the horizontal axis of FIG. 4 is divided by the pulling speed of 0.65 mm / min, and the pulling time is plotted on the horizontal axis.

<Comparative Test 1 and Evaluation> Observation of Occurrence of Stacking Faults After the slice planes of the sample A1 of Example 1 and the sample A1 ′ of Comparative Example 1 were treated with an etchant having selectivity for stacking faults. It was observed visually and by an optical microscope. A close-up photograph of Example 1 is shown in (a-1) of FIG. 1, and a close-up photograph of Comparative Example 1 is shown in (a-2) of FIG. The temperature shown in FIG. 1 is the temperature of each part of the ingot when pulling is stopped and the pulling is held for 2 hours. The white stripes in both figures are stacking faults. In Comparative Example 1, stacking faults appeared near the periphery of the ingot over substantially the entire length of the ingot. This is called a ring-shaped stacking fault (ring OSF) because it is distributed in a ring shape when observed in the shape of a silicon wafer. In contrast to Comparative Example 1, in Example 1, the stacking fault disappeared in the region near 1100 ° C., and the stacking fault appeared in other temperature regions.

Observation of Occurrence of Oxygen Precipitate Sample B1 of Example 1 and sample B1 ′ of Comparative Example 1 were sliced with an etching solution having selectivity for oxygen precipitates, and then visually and It was observed with an optical microscope. A close-up photograph of Example 1 is shown in FIG. 1 (b-1), and a close-up photograph of Comparative Example 1 is shown in FIG. 2 (b-2).
In both figures, the white part is the region where oxygen precipitates are generated at high density. In Comparative Example 1, the oxygen precipitates appeared over the entire length of the ingot, whereas in Example 1, the oxygen precipitates disappeared in the region near 1100 ° C., and the oxygen precipitates appeared in other temperature regions.

<Examples 2 to 10> Example 1 and Comparative Example 1
From the results, it was found that stacking faults and oxygen precipitates disappeared in a temperature range near 1100 ° C. Therefore, using the ingot pulling device 12 shown in FIG. 7, a silicon single crystal ingot having a diameter of 5 inches and a length of 800 mm was used. 11 to 0.6
It was pulled up at a constant pulling speed of 5 mm / min. 7, the same components as those shown in FIG. 8 are designated by the same reference numerals. A characteristic configuration of the pulling device 12 shown in FIG. 7 is that the temperature of the silicon single crystal ingot 11 being pulled is 1130 ° C., 1100 ° C., and 1070 ° C. The auxiliary heater 10 as a temperature control device is provided in a predetermined zone above the position. Have been established respectively. The temperature decrease rate was controlled by the auxiliary heater 10. In this example, 1
At 130 ° C., 1100 ° C., 1070 ° C., the temperature decreasing rate becomes 0 ° C./min to stop the temperature decrease, and the stopping time at each temperature is 10 minutes, 1 hour or 2 hours (holding time 10 minutes, 1 hour or 2 hours) so that the heating amount of the auxiliary heater 10 and its length L
Was adjusted and provided. Specifically, the length L of the auxiliary heater 10 was set to the shortest when the stop time was 10 minutes, and set to the longest when the stop time was 2 hours. When the holding temperature was 1130 ° C, the heating amount of the auxiliary heater 10 was maximized, and when it was 1070 ° C, it was minimized.

FIG. 3 shows the temperature distribution of the silicon single crystal ingot in the ingot pulling apparatus 12 shown in FIG. 7 when the auxiliary heater 10 was adjusted so that the holding temperature was 1100 ° C. with the stop time of 1 hour in Example 6. Shown in. This temperature distribution was also obtained in the same manner as in FIG. FIG. 5 shows the heat history of the ingot when the entire ingot of Example 6 was pulled at a constant speed of 0.65 mm / min. In FIG. 5, the distance on the horizontal axis of FIG. 3 is divided by the pulling speed of 0.65 mm / min, and the pulling time is plotted on the horizontal axis. The grown silicon single crystal ingot is taken out from the apparatus 12, sliced in the center of the ingot in parallel with the pulling direction in the same manner as in Example 1, and half of the sliced sample is wet oxygen (w).
EtO ₂ ) atmosphere for 1 hour at 1100 ° C. for 9 hours
Samples A2 to A10 were obtained. The other half was subjected to the same procedure as in Example 1 in a dry oxygen (dryO ₂ ) atmosphere to 1000
Another 9 samples B2 to B10 after heat treatment at ℃ for 40 hours
Got

<Comparative Examples 2 to 9> 1000 ° C., 1050
At a temperature decrease rate of 0 ° C./min at 100 ° C. and 1200 ° C. to stop the temperature decrease, and the stop time at each temperature is 10 minutes, 1 hour or 2 hours, respectively (holding time is 10 minutes, 1 hour). As shown in FIG.
The heating amount and the length L of the auxiliary heater 10 of the ingot pulling device 12 shown in FIG. The method of this adjustment is the same as in Examples 2-10. Others were pulled up in the same manner as in Example 2 to obtain a silicon single crystal ingot. The grown silicon single crystal ingot is taken out from the apparatus 12, sliced parallel to the pulling direction at the center of the ingot as in Example 1, and half of the sliced sample is placed at 1100 ° C. in a wet oxygen (wetO ₂ ) atmosphere. Then, heat treatment was performed for 1 hour to obtain eight samples A2 'to A9'. The other half was heat-treated at 1000 ° C. for 40 hours in a dry oxygen (dryO ₂ ) atmosphere in the same manner as in Example 1 to obtain another eight samples B2 ′ to B9 ′.

<Comparative Test 2 and Evaluation> Measurement of Stacking Fault Density Samples A2 to A10 of Examples 2 to 10, Sample A1 'of Comparative Example 1 and Samples A2' to A9 'of Comparative Examples 2 to 9
Was treated with an etching liquid having selectivity for stacking faults, and an arbitrary portion was observed with an optical microscope to measure the number of stacking faults per 1 cm ³ (stacking fault density). The results are shown in Table 1.

Measurement of oxygen precipitate density Samples B2 to B10 of Examples 2 to 10, sample B1 ′ of Comparative Example 1 and samples B2 ′ to B9 ′ of Comparative Examples 2 to 9
Was treated with an etchant having selectivity for oxygen precipitates, and then an arbitrary portion was observed with an optical microscope to measure the number of oxygen precipitates per 1 cm ³ (oxygen precipitate density). The results are shown in Table 1.

[0019]

[Table 1]

As is clear from Table 1, the stacking fault densities of Comparative Examples 1 to 9 are 15.0 to 48.0 × 10 ⁶ / cm ³ , whereas the stacking fault densities of Examples 2 to 10 are Is 0
It was 1.6 × 10 ⁶ / cm ³ , which was extremely small. Furthermore, the oxygen precipitate density of Comparative Example 1 is 600 to 900 × 10 ⁶ /
cm ³ and the density of oxygen precipitates in Comparative Examples 2 to 9 was 2
While it is 2.0 to 360.0 × 10 ⁶ / cm ³ ,
The oxygen precipitate density of Examples 2-10 is 0-22.0x10.
^{It was 6} / cm ³ , which was extremely small.

[0021]

As described above, according to the method for pulling a silicon single crystal of the present invention, of the temperature drop distribution of the silicon single crystal ingot which is being pulled at a pulling rate of 0.6 to 2.0 mm / min. By decelerating the temperature lowering rate to 0 to 0.3 ° C./min in the temperature range of 1130 to 1070 ° C. and maintaining the temperature lowering rate for at least 10 minutes, stacking faults and oxygen are formed on the silicon wafer when heat-treated in the semiconductor device process. It is possible to prevent the formation of precipitates. As a result, the silicon single crystal wafer manufactured from the obtained silicon single crystal ingot has an excellent effect that the generation of defects is significantly reduced and the industrial utility value is extremely large. Further, in the method of the present invention, the pulling rate that suppresses the generation of nuclei that are the origin of oxygen precipitates and stacking faults is 0.
Since it is faster than the conventional method of 4 mm / min, productivity is high,
There is also an advantage that it consumes less energy.

[Brief description of drawings]

FIG. 1 is a close-up photograph of a crystal structure on an ingot slice plane showing a stacking fault and an occurrence of oxygen precipitates when a silicon single crystal ingot of Example 1 of the present invention is pulled and then heat treated.

FIG. 2 is a photograph showing a close-up of a crystal structure on an ingot slice plane showing a stacking fault and an occurrence of oxygen precipitates when a silicon single crystal ingot of Comparative Example 1 is pulled and then heat treated.

FIG. 3 is a temperature distribution diagram when pulling a silicon single crystal ingot of Example 6 of the present invention in the ingot pulling apparatus shown in FIG. 7.

4 is a temperature distribution diagram when pulling a silicon single crystal ingot of Comparative Example 1 in the ingot pulling apparatus shown in FIG.

FIG. 5 shows the ingot pulling device shown in FIG.
The temperature distribution figure of the silicon single crystal ingot of Example 6 when pulled up at a constant speed of 5 mm / min.

FIG. 6 shows the ingot pulling device shown in FIG.
FIG. 5 is a temperature distribution diagram of the silicon single crystal ingot of Comparative Example 1 when pulled at a constant speed of 5 mm / min.

FIG. 7 is a configuration diagram of a pulling apparatus used for growing the silicon single crystal ingots of Examples 2 to 10 of the present invention and Comparative Examples 2 to 9.

8 is a configuration diagram of a pulling apparatus used for growing the silicon single crystal ingots of Example 1 and Comparative Example 1. FIG.

[Explanation of symbols]

 1,11 Silicon single crystal ingot 2,12 Ingot pulling device 4 Quartz crucible 6 Heater 7 Silicon melt 10 Auxiliary heater

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[Procedure amendment]

[Submission date] September 19, 1994

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[0018] Measurement of Oxygen Precipitant Density Samples B2 to B10 of Examples 2 to 10 and Comparative Example 1
Sample B1 'and samples B2' to B of Comparative Examples 2 to 9
9'is treated with an etchant that is selective for oxygen precipitates.
After observing, 1cm by observing any part with an optical microscope^ThreeHit
The number of oxygen precipitates (oxygen precipitate density) was measured. That conclusion
The results are shown in Table 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Watanabe 1-297 Kitabukuro-cho, Omiya-shi, Saitama Prefecture Central Research Laboratory, Mitsubishi Materials Corporation (72) Hisashi Furuya 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Central Research Laboratory, Materials Co., Ltd.

Claims (2)

[Claims] 1. A silicon single crystal ingot (11) formed from a silicon melt (7) held in a crucible (4) in a pulling device (12).
In the method of pulling up silicon, one of the temperature drop distributions of the silicon single crystal ingot (11) being pulled up at a pulling rate of 0.6 to 2.0 mm / min.
In the temperature range of 130 to 1070 ° C, the temperature decreasing rate is 0 to 0.3.
A method for pulling up a silicon single crystal, which is characterized in that a stacking fault and an oxygen precipitate are not generated in a silicon wafer when heat-treated after pulling by decelerating to ° C / min and maintaining the temperature lowering rate for at least 10 minutes. . 2. The method for pulling a silicon single crystal according to claim 1, wherein the holding time of the temperature lowering rate in the temperature range of 1130 to 1070 ° C. is 10 minutes or more and less than 3 hours.