JPH07330484A - Pulling up device and production of silicon single crystal - Google Patents

Abstract

PURPOSE:To decrease crystal defects by measuring relative positions of the members in a furnace and a melt surface with a melt position measuring instrument installed at the members in the furnace which is brought into contact with a melt and pulling up a single crystal while controlling these relative positions. CONSTITUTION:Polycrystalline Si is charged into an inner quartz crucible 1a reinforced with an outer graphite crucible 1b and is melted by heating with a heater 5. An Ar atmosphere is then generated in the device by passing gaseous Ar and after a seed crystal 8 is brought into contact with the Si melt 2, the Si single crystal 3 is pulled up. The melt position measuring instrument 10 of an overall length about <=200mm consisting of high-purity quartz glass, etc., installed in the bottom end position of a tubular body 4 installed to enclose the Si single crystal 3 is used and the contact of the Si melt surface and the melt position measuring instrument 10 is detected with accuracy of about <=0.1mum by an image processor 13. The Si single crystal 3 is pulled up while the relative positions are controlled. The Si single crystal 3 having the decreased crystal defects is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the control of oxygen concentration in a silicon single crystal and the crystal defects represented by oxygen induced stacking faults (OSF) in the production of a silicon single crystal by the Czochralski method (CZ method). The present invention relates to an apparatus and a manufacturing method for preventing the occurrence of

[0002]

2. Description of the Related Art As a method for producing a single crystal, the CZ method, in which a crystal is pulled from a melt in a crucible while growing, is widely used. When manufacturing the silicon single crystal of the CZ method,
As disclosed in JP-A-64-72986, an inert gas typified by argon is caused to flow between a heat insulating cylinder and a melt surface to suppress evaporative substances from the melt, and silicon due to the adhered evaporative substances is suppressed. It prevents dislocation of the single crystal. Also,
The flow rate of argon, the furnace pressure, and the distance between the heat insulating cylinder and the melt surface are adjusted to control oxygen in the crystal and reduce crystal defects such as OSF.

As a method for measuring the position of the melt surface in the furnace, for example, as shown in Japanese Patent Laid-Open No. 61-86943, light is projected toward the melt surface and reflected light from the melt surface is used. There has been proposed a method for detecting and measuring from the change in the projection hole path or the reflection hole path. In addition, JP-A-63-2
In No. 81022, a reference point is set on a part of a radiation screen installed above the melt surface, a linear sensor captures this reference point and a reflection image of the reference point with respect to the melt surface, and the reference point on the linear sensor A method has been proposed in which the distance from the reference point to the melt surface is calculated based on the distance between the reflected image and the reflected image.

[0004]

However, during the production of a silicon single crystal, the inside of the furnace is in a high temperature state, so that the members inside the furnace are thermally expanded. Further, the quartz glass forming the crucible holding the silicon melt is softened. Due to these heat deformations, it is difficult to accurately set the relative position between the member in the pulling furnace and the melt surface. As a result, the effects of preventing dislocation of the silicon single crystal, controlling oxygen in the crystal, and reducing crystal defects such as OSF are lost.

Therefore, the present invention is an apparatus for pulling a silicon single crystal from a melt in a crucible, which measures the relative position between a member in the furnace and the surface of the melt and controls the position of the silicon single crystal. An object of the present invention is to provide an apparatus and a manufacturing method for pulling a crystal. The present invention also provides a manufacturing method capable of preventing dislocation of a silicon single crystal, controlling oxygen in the crystal, and reducing crystal defects such as OSF during the growth of the silicon single crystal by simple adjustment. The purpose is to do.

[0006]

Means for Solving the Problems The present invention for achieving the above object is an apparatus for pulling a silicon single crystal from a melt in a crucible, the position of the melt being installed in a furnace member such as a heat insulating cylinder. An apparatus for producing a silicon single crystal, characterized in that a distance between a lower end of a furnace member and a silicon melt surface is measured by a contact method using the apparatus.

Further, according to the present invention, by using the silicon single crystal manufacturing apparatus having the above-mentioned structure, the distance between the lower end of the furnace inner member such as a heat insulating cylinder and the silicon melt surface is controlled to grow the silicon single crystal. A method for producing a single crystal, which comprises preventing dislocation of a silicon single crystal, controlling oxygen and carbon in the crystal, and reducing crystal defects such as OSF.

[0008]

According to the apparatus for producing a silicon single crystal of the present invention,
It is possible to control the relative position between the member in the manufacturing apparatus and the melt surface.
Therefore, it becomes possible to prevent dislocation of a silicon single crystal from occurring, control oxygen in the crystal, and reduce crystal defects such as OSF.

Hereinafter, the present invention will be described in more detail based on the embodiments. FIG. 1 is a sectional view showing the configuration of an embodiment of the silicon single crystal pulling apparatus of the present invention. In the silicon single crystal pulling apparatus of this embodiment, the silicon single crystal 3 is pulled from the melt 2 in the crucible 1. In FIG. 1, the melt 2 is heated by a tubular heater 5 and covered with a tubular heat insulating material 6. Further, the crucible 1 is connected to a support base 7 below, and the support base 7 is connected to a crucible drive device 15 provided outside the furnace so that the crucible is supported so as to be vertically movable and rotatable. Reference numeral 8 is a seed crystal for growing a single crystal. Arrows 11 and 1 in the outer wall 9 of the pulling furnace
2 shows the gas flow in the furnace. A tube body 4 is installed so as to surround the crystal 3. Further, the melt position measuring device 10 is installed in the tube body 4 via a fixing pin 17 joined to the lower end portion of the tube body 4. Details of the melt position measuring device 10 are shown in FIG. In the melt position measuring device 10 of FIG.
It is designed so that the center of gravity is located on the axis connecting the fixed portion position (position of the fixing hole 19 through which the fixing pin 17 is inserted) and the measuring end 16 so that the melt position measuring end 16 becomes the lowermost end.
The melting point position measuring device 10 may be made of high-purity quartz glass similar to the crucible holding the silicon melt, but high-purity quartz crystal, carbon, silicon nitride, silicon carbide,
It is also possible to use carbon coated with silicon nitride or silicon carbide, or the same silicon as the raw material of the silicon single crystal (the material of the fixing pin 17 may be a high melting point material, such as molybdenum and tungsten). High-purity carbon, silicon nitride, silicon carbide, carbon coated with these silicon nitride and silicon carbide, and silicon can also be used.).

The total length L of the melt position measuring device 10 is, for example, about 5 × 10 ^-6 / deg of carbon having a high coefficient of linear thermal expansion β, and the temperature difference ΔT at the time of growing a single crystal is about 1400 ° C.
Then, in order to reduce the thermal expansion ΔL to 0.1 mm or less,

[0011]

[Equation 1]

From the calculation of, the total length L of the melt position measuring device 10 should be 14 mm or less. further,
In the case of high-purity quartz glass, the coefficient of linear thermal expansion is about 4 × 10 ^-7 /
Since it is deg, the total length L is 200 mm from the same calculation.
If it is below, the thermal expansion length can be set to 0.1 mm or less. In the melt position measuring device 10 made of silicon, when the melt position measuring device 10 is brought into contact with the silicon melt, the melt position measuring device 10 may be melted or the silicon melt may be solidified to change the entire length of the melt position measuring device 10. Therefore, as shown in FIG. 3, the melt position measuring device 10 made of silicon can be reused by making a notch on the surface or marking the scale 18 or the like.

The shape of the melt position measuring apparatus 10 is not limited to the shape shown in FIG. 2 or 3 as long as the area of the contact portion with the silicon melt is sufficiently small. Would be obvious.

The distance between the tube body 4 and the silicon melt was measured using the melt position measuring device 10, and the relationship with the oxygen concentration in silicon was arranged in FIG. It was found that the oxygen concentration in silicon increases as the distance increases. From the result of FIG. 4, it was discovered that the above-mentioned interval must be controlled with an accuracy of 0.1 mm in order to control the oxygen concentration to 0.1 × 10 ¹⁷ / cc or less. Further, since the crystal defects in the silicon single crystal such as OSF increase as the oxygen concentration in silicon increases, it is considered that the crystal defects in the OSF and the like can be inevitably reduced by reducing the fluctuation.

In order to exert the above effects in the production of a silicon single crystal, the position with the melt is measured by using the melt position measuring device 10 as shown in FIG. FIG. 5 (a)
Indicates a state in which the raw material is melted and a melt surface is formed. As a next step, FIG. 5B shows a method for measuring the position of the melt surface with the melt position measuring device. By moving the support base 7 by the driving device 15, the melt surface 2 and the melt position measuring device 1
The image processing device 13 detects the contact with 0. Further, as shown in (c) and (d) of FIG. 5, the moving distance for setting the distance between the melt and the lower end of the tube 4 to a desired value is calculated by the computer 14 using the signal of the image processing device 13. To do.
Based on the moving distance data, the drive device 15 supports the support base 7
To move. The above-described series of melt control is performed according to the control flow shown in FIG.

During the measurement, the melt position measuring device 10 comes into contact with the melt, but since the contact area is small and the contact area is small, the purity of the silicon melt is not reduced. If the purity of the melt is a problem, the melt position measuring device 10 may use the same silicon or single crystal silicon as the raw material. Furthermore, by preventing the length of the melt position measuring device 10 from coming into contact with the silicon melt during the production of a silicon single crystal, the flow in the silicon melt is not disturbed.

In the above embodiment, an example in which the straight tubular body 4 is arranged as the furnace inner member has been shown, but the furnace inner member is not limited to this, and for example, a taper. It may be various conventionally known ones such as a heat insulating cylinder having other shapes such as a tubular shape or a funnel shape, and further a water cooling mechanism and a heating mechanism.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the apparatus shown in FIG. 1, a quartz crucible 1a having an inner diameter of 18 inches, which is reinforced with a graphite crucible 1b from the outside.
Then, 60 kg of polycrystalline silicon as a raw material was charged and melted, and a silicon single crystal 3 having a diameter of 155 mm was pulled up. Argon gas was caused to flow in the direction of the arrow to make the inside of the apparatus an argon atmosphere. The total length of the tube 4 used for pulling up is about 5
At 00 mm, the length changes by about 3 to 5 mm due to thermal expansion. The material of the melt position measuring device 10 was made of high-purity quartz glass and had a total length of 50 mm. Using the melt position measuring device 10, the contact between the silicon melt surface 2 and the lower end of the melt position measuring device is detected by the image processing device. Image processing device 1
3 is used to move the support base 7 by the drive device 15 so as to control the liquid surface position with an accuracy of 0.1 mm or less, and in this embodiment, the lower end of the tube 4 and the silicon melt surface are used. The distance from 2 was controlled to 20.0 mm.

FIG. 7 shows an example of the effect of using the method of the present invention.
Shown in. The oxygen concentration and OSF of the pulled ingot before and after using the melt position measuring apparatus 10 are shown as average density changes. Each data was obtained by evaluating the oxygen concentration / OSF measurement test pieces collected at 8 sites from a silicon single crystal having a constant diameter portion of about 700 mm at intervals of 100 mm. The oxygen concentration was measured by the infrared absorption method. The OSF is measured by performing wet oxidation at 1100 ° C. for 60 minutes and then observing etch pits by selective etching (90 seconds with a light solution). Oxygen concentration and OS of each single crystal in FIG.
The F density was represented by the average value of 8 sites. In FIG.
Prior to using the method of the present invention, variations in oxygen concentration were about ±
0.5 × 10 ¹⁷ / cc (JEIDA), the average OSF generation was about 5 pieces / cm ² , but the oxygen concentration fluctuation was ± 0.1 × 10 ¹⁷ / cc by using the method of the present invention.
(JEIDA), OSF generation is 1 / c on average
It is clear that it is reduced to m ² or less. The dislocation ratio of the crystal was about 10% before the method of the present invention was used, while it was reduced to about 1% after the method of the present invention was used.

[0020]

As described above, according to the silicon single crystal manufacturing apparatus of the present invention, the relative position between the member in the manufacturing apparatus and the melt surface can be controlled with an accuracy of, for example, 0.1 mm or less. It is possible to prevent dislocation of a silicon single crystal, control oxygen in the crystal, and reduce crystal defects such as OSF.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a view showing a melt position measuring device made of high-purity quartz.

FIG. 3 shows a melt position measuring device made of a silicon single crystal, (a) is a plan view, (b) is a front view, and (c) is a side view.

FIG. 4 shows the relationship between the distance between the lower end of the tubular body and the surface of the silicon melt and the oxygen concentration in silicon.

5A and 5B are diagrams showing respective steps of melt position measurement according to the present invention, where FIG. 5A is when the raw material dissolution is completed, FIG. 5B is the melt position measurement, and FIGS. 3 shows the positional relationship between the lower end of the tubular body and the surface of the melt when pulling the single crystal.

FIG. 6 shows a control flow of the melt position control device.

FIG. 7 is a diagram showing an example of effects when the method of the present invention is used.

[Explanation of symbols]

1 ... crucible, 1a ... quartz crucible, 1b ... graphite crucible, 2 ... melt, 3 ... silicon single crystal, 4
... tubular body, 5 ... heater, 6 ... heat insulating material, 7 ... support base, 8 ... seed crystal, 9 ... furnace outer wall,
10 ... Melt position measuring device, 11, 12 ... Furnace gas flow, 13 ... Image processing device, 14 ... Calculator, 15 ... Crucible driving device (vertical / rotatable), 16 ... Melt position measuring end, 17 ... Fixed Pin, 18 ... Scale, 19
… Fixing holes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyo Kiyoshi Yamaguchi Prefecture Hikari City 3434 Shimada, Nittatsu Electric Co., Ltd.

Claims (2)

[Claims] 1. An apparatus for pulling a silicon single crystal from a melt in a crucible, wherein a relative position between a furnace inner member and a melt surface is measured by a melt position measuring device installed in the furnace inner member. A device that pulls a silicon single crystal while controlling the relative position by measuring by touching. 2. A method for pulling a silicon single crystal from a melt in a crucible, wherein a relative position between a furnace inner member and a melt surface is measured by a melt position measuring device installed in the furnace inner member. A method for manufacturing a silicon single crystal, which comprises pulling a silicon single crystal while controlling the relative position of the silicon single crystal by controlling the relative position.