JPH09235176A - Quartz crucible for melting silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equip the inner sidewall of a quartz crucible with a spiral staircase- shaped fin to regulate the rising of the thermal convection in a silicon melt along the sidewall of the crucible and thus enable the oxygen concentration of the melt to be controlled and a high-quality silicon single crystal to be pulled. SOLUTION: The inner sidewall 3 of a quartz crucible 1 is equipped with a spiral staircase-shaped fin 2. Thereby, such a control as to suppress or promote the rising of the thermal convection in a silicon melt in the crucible can be conducted by altering the direction and speed of revolution of the crucible, leading to obtain a silicon single crystal excellent in the in-plane distribution characteristics of impurities such as oxygen and in device characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon melting quartz crucible used for pulling a silicon single crystal,
The present invention relates to a quartz crucible capable of controlling an increase in thermal convection on a side wall of a crucible in a silicon melt, controlling an oxygen concentration, and pulling a high-quality silicon single crystal.

[0002]

2. Description of the Related Art In order to produce a silicon single crystal, a method of melting a high-purity silicon raw material in an argon atmosphere under reduced pressure and solidifying it by pulling it upward with a seed crystal (CZ
It is often used).

FIG. 4 is a vertical sectional view showing a silicon single crystal manufacturing apparatus for solidifying while pulling. Reference numeral 8 in the figure
Is a chamber for decompressing the pulling atmosphere of the silicon single crystal 11, a melting crucible 5 is arranged inside the chamber, and a heating heater 6 composed of an induction heating coil and the like is provided outside the crucible, surrounding the crucible 5. Further, on the outside thereof, a heat insulating cylinder 7 formed of a heat insulating material in a cylindrical shape is arranged. In the melting crucible, raw material for crystal growth melted by a heater,
That is, the melt 9 of the silicon raw material is contained. Seed crystal attached to the surface of the melt at the tip of pulling wire 12
By bringing the lower end of 10 into contact and pulling this seed crystal upward, a silicon single crystal 11 in which the melt is solidified is grown at the lower end.

At this time, the melting crucible is rotated by the rotating shaft 15, and the silicon single crystal is rotated by the rotating mechanism (not shown) provided above the pulling wire in opposite directions. The melting crucible has a double structure and is composed of a container 1 made of quartz inside (hereinafter referred to as "quartz crucible") and a container 4 made of carbon at outside (hereinafter referred to as "carbon crucible"). There is.

The inside of the decompression chamber is decompressed to about 10 torr, argon gas is supplied from the gas supply port 13, and SiO gas generated from the surface of the silicon melt and CO gas generated from the carbon crucible and the heater are exhausted. Discharge through mouth 14.

It is known that a quartz crucible reacts with a silicon melt to elute oxygen, and as a method for reducing this, a heating method or a method of controlling convection of the melt by magnetic control has been proposed. There is. However, these methods involve major equipment modifications.

The quartz crucible used in the above method has a smooth side wall and bottom as shown in FIG. 4 for ease of manufacture. There is also an attempt to control the thermal convection by changing the shape inside the quartz crucible. For example,
-130892 discloses a flow direction control in which the melt in the crucible flows from the center bottom of the crucible to the outer circumference along the bottom of the crucible along with the rotation of the crucible, and further upward along the inner wall of the crucible. A crucible has been proposed in which one piece is provided at the bottom of the crucible to reduce the amount of oxygen mixed into the single crystal. Further, in Japanese Utility Model Laid-Open No. 63-11574, a barrier that prevents convection of the melt on the inner wall of the crucible is provided in the shape of an eave in the direction of the inner diameter so that a single crystal with less striation can be obtained. Is proposed.

However, the method of integrally providing the control piece on the bottom of the crucible increases the surface area of the quartz body, which increases the amount of oxygen dissolved in the silicon melt and complicates the processing, resulting in a high cost. . Further, in the method of providing a barrier on the inner wall of the crucible, the process of fixing the barrier on the side wall is complicated, and the upward flow of thermal convection will be collected in the crystal growth part, disturbing the flow of the melt and mixing impurities. There is a problem of promoting.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a crucible capable of controlling the increase of thermal convection on the side wall of the crucible in the silicon melt, controlling the oxygen concentration, and pulling a high-quality silicon single crystal. To provide.

[0010]

The gist of the present invention resides in the following quartz crucible for melting silicon shown in FIG.

A quartz crucible for melting silicon having a double structure in which a quartz crucible is inserted inside a carbon crucible, characterized in that the quartz crucible 1 has a spiral step-like fin 2 on an inner side wall portion 3 thereof. Quartz crucible for melting silicon.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing a partial cross section of a quartz crucible for melting silicon according to the present invention. The melting crucible 1 of the present invention comprises a fin 2 which is developed in a spiral step shape on the inner side wall 3.
(Hereinafter, this is simply referred to as "fin") is fixed. By providing the fin 2 on the side wall inside the quartz crucible and changing the rotation direction and the rotation speed of the crucible, it is possible to perform control so as to suppress or accelerate the rise of thermal convection.

In the quartz crucible of the present invention, after the crucible body and the spiral step fins are manufactured from quartz by a usual method,
The fin can be manufactured by inserting the fin into the crucible and heating and welding the upper end of the fin.

FIG. 2 is a diagram showing the flow of the melt in the quartz crucible during the growth of a silicon single crystal by the ordinary pulling method.
(a) is a sectional view and (b) is a plan view. As described above, the quartz crucible is heated by radiation from the side wall by the cylindrical heater. Therefore, thermal convection a occurs in the molten liquid in the crucible.
, The forced flow b due to the rotation of the single crystal, the forced flow c due to the rotation of the crucible, and the Marangoni convection d generated only on the surface.

In these flows, the thermal convection a makes the temperature distribution of the melt uniform, and also affects the crystal growth rate and the ease of controlling the diameter. Further, it is said that thermal convection is in a turbulent state, which causes a temperature change, that is, a growth rate change at a crystal growth interface, which causes a non-uniform distribution of impurities and a defect. Further, it promotes the dissolution of the quartz crucible in the melt and increases the mixing of oxygen.

The forced flow b due to the rotation of the single crystal rotates in the direction opposite to the rotation of the crucible within the rotation speed of the crystal of 15 to 30 rpm, so that an inertial force is applied to the melt and a liquid flow is generated. . Since this flow is a laminar flow without turbulence, it is said that it has an action of preventing the entry of turbulent thermal convection just below the crystal growth interface and stabilizing the crystal growth.

The forced flow c due to the rotation of the crucible normally causes the crucible wall to be rotated in a direction opposite to the rotation of the crystal, so that a velocity substantially equal to the crucible rotation speed is given to the crucible wall surface as shown in Fig. (B). , It becomes a flow that suppresses thermal convection.

The Marangoni convection d is a flow generated by uneven surface tension, and is smaller than the thermal convection and the forced flow due to the rotation of the crystal and the crucible, and is said to have almost no effect on the growth of the silicon single crystal.

Thus, the convection of the melt has an effect of moving heat and impurities in the melt, and the oxygen concentration and the uniformity of the dopant distribution are determined by the size of the heat convection. Therefore, it is necessary to control the magnitude of the convection of the melt.

FIG. 3 is a diagram showing a possible liquid flow when the crucible of the present invention is used. (A) shows the case where the crucible is rotated in the same direction as the rising direction of the spiral staircase fin, (b) FIG. 6 is a diagram showing a case where the crucible is rotated in the direction opposite to the upward direction of the spiral staircase fin.

When the crucible is rotated in the same direction as the rising direction of the spiral staircase fin, the thermal convection a on the side wall of the crucible rises along the lower surface of the fin, and the forced flow c due to the rotation of the crucible is superposed. . On the other hand, when the crucible is rotated in the direction opposite to the rising direction of the spiral staircase fin, the thermal convection a on the side wall of the crucible rises along the lower surface of the fin and is suppressed by the forced flow c due to the rotation of the crucible.

[0022]

EXAMPLE A single crystal having a diameter of 8 inches was manufactured by using the silicon single crystal manufacturing apparatus shown in FIG. 4 in which the melting quartz crucible of the present invention shown in FIG. 1 was arranged. A fin having a width of 50 mm, a thickness of 3 mm and a spiral winding number of 3 was set on the inner wall of a quartz crucible having an inner diameter of 750 mm and a height of 400 mm.

100 kg of polycrystalline silicon was melted to produce a 800 mm long single crystal at a pulling rate of 1.0 mm / min. As a comparative example, a conventional fused silica crucible as shown in FIG. 4 was used to manufacture the same silicon single crystal.

In the test using the melting crucible for melting of the present invention, two kinds of tests were carried out: one in the case of rotating in the same direction as the rising direction of the spiral step fins, and the other in the case of rotating in the opposite direction to the rising direction of the spiral step fins. The single crystal was pulled up.

As an evaluation, impurities and defects in the obtained single crystal were investigated, and the results are shown in Table 1. In Table 1, the in-plane distribution of the dopant was measured by a four-edge probe method in a state of being cut into wafers, the oxygen concentration was measured by the FT-IR method, and the IR defect density was measured by the infrared tomography method.

[0026]

[Table 1]

The following can be seen from Table 1.

In Invention Example 1, the crucible was rotated in the same direction as the rising direction of the spiral staircase fin, and the crystal was rotated in the opposite direction. The in-plane distribution of the dopant was ± 1% and the IR defect density was 1 ×. As small as 10 ⁵ pieces / cm ³ , oxygen concentration is 17 × 10
^It became a little higher at ¹⁷ atoms / cc.

In Invention Example 2, the crucible was rotated in the direction opposite to the rising direction of the spiral staircase fin, and the crystal was rotated in the same direction as the rising direction of the spiral staircase fin. The density was the same as that of Inventive Example 1, but the oxygen concentration could be as low as 3 × 10 ¹⁷ atoms / cc. It is considered that when the crucible is rotated in the direction opposite to the rising direction of the spiral staircase fin, the thermal convection of the melt is suppressed, so that the oxygen introduced into the crystal growth interface is reduced.

Comparative Examples 3 and 4 are cases in which a normal crucible having no fin inside was used, and the in-plane distribution of the dopant was ± 5% and the IR defect density was 5 × 10 ⁵ / cm ^3. high.

[0031]

By using the silicon melting crucible of the present invention, a silicon single crystal having excellent in-plane distribution of impurities such as dopant and oxygen and excellent device characteristics can be obtained.
Furthermore, the oxygen concentration of the single crystal can be controlled from low oxygen to high oxygen.

[Brief description of drawings]

FIG. 1 is a view showing a vertical cross section of a silicon melting crucible of the present invention.

FIG. 2 is a diagram showing a flow of a molten liquid in a quartz crucible during the growth of a silicon single crystal by a normal pulling method, (a) is a sectional view,
(b) is a plan view.

FIG. 3 is a diagram showing a liquid flow in a fluid model test using the quartz crucible of the present invention, where (a) is the crucible rotated in the same direction as the rising direction of the spiral staircase fin, and (b) is the crucible. It is a figure showing the case where it rotates in the direction opposite to the ascending direction of the spiral staircase fin.

FIG. 4 is a vertical cross-sectional view showing a silicon single crystal manufacturing apparatus for solidifying while pulling.

[Explanation of symbols]

 1. Quartz crucible 2. Fin 3. Side wall 4. Carbon crucible 5. Melting crucible 6. Heater for heating 7. 7. Heat insulation tube Decompression chamber 9. Silicon melt 10. Seed crystal 11. Silicon single crystal 12. Pull wire 13. Gas supply port 14. Gas outlet 15. Rotating axis A. Crystal rotation direction B. Rotating direction of crucible a. Thermal convection b. Forced flow due to crystal rotation c. Forced flow by rotation of crucible d. Marangoni convection

Claims (1)

[Claims] 1. A quartz crucible for melting silicon having a double structure in which a quartz crucible is inserted inside a carbon crucible, wherein the inner wall of the quartz crucible has a spiral step fin. Quartz crucible for melting.