JPH04321587A - Device for pulling up single crystal - Google Patents

Abstract

PURPOSE:To obtain a device for pulling up single crystal capable of increasing growth rate of single crystal, stabilizing growth of single crystal, improving qualities of grown crystal and especially reducing variability of internal distribution of specific resistance. CONSTITUTION:Surface position of melt 4 is made higher than the top of a uniformly heating zone 25 of a heating element 12 and an inverted conical reflecting plate 18 to reflect heat radiation from the surface of the melt toward a contact zone 19 of the surface of the melt with a crucible 5 is laid between single crystal 3 and the crucible 5 covering the single crystal and the reflecting plate 18 is provided with a nozzle 31 of spraying an inert gas to prevent sticking of SiO to the reflecting surface. The reflecting plate 18 is supported by 8 gas pipes 30 for supplying an inert gas 32.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal pulling apparatus capable of suitably carrying out the Czochralski method.

0002

2. Description of the Related Art FIG. 9 is a longitudinal sectional view of a conventional single crystal pulling apparatus. A crucible 5 supported by a susceptor 6 contains a melt 4, and a seed chuck 2 is connected to a seed wire 1.
The single crystal 3 is pulled up through the . The heating body 12 has a temperature distribution as shown on the right side of the figure, and its isothermal region is called a soaking zone 25. In addition, 7 is a pedestal, 8 is a crucible shaft, 9 is a heat insulator, 10 is a post that supports this,
11 is a base plate, 13 is a support, and 14 is an electrode.

[0003] In the conventional Czochralski method, single crystals were pulled within a range in which the position of the melt surface 22 (hereinafter referred to as melt level) did not deviate from the soaking zone 25 of the heating element 12. The reason for this is that the melt level is set to 2 in the soaking zone.
This is because if it is removed upward from 5, the melt will solidify more easily from the crucible side, and pulling of the single crystal will be inhibited. Such conventional technology has the following two problems. (1) Since the region 21 where the melt 4 contacts the side wall of the crucible 5 is inside the soaking zone, the melt is heated in this region and cooled on the surface 22 of the melt. Therefore, thermal convection 23 indicated by the arrow
This extends to the vicinity of the solid-liquid interface between the single crystal and the melt, making crystal growth unstable. Note that the arrow 24 indicates convection due to rotation of the crystal. (2) During crystal growth, the crucible 5 and susceptor 6 are
It may be tilted as shown in the vertical cross-sectional view in a). In addition,
FIG. 10(b) is a sectional view taken along the line CC in FIG. 10(a). In this case, the melt 4 near point A is always far from the heating body 12, and the melt 4 near point B is always close to the heating body 12. Therefore, the temperature distribution on the surface of the melt on the straight line X passing through point AB becomes as shown in FIG. 10(c), which is asymmetrical with respect to the crystal pulling axis 27. As a result, the solid-liquid interface alternately passes through regions of high temperature and regions of low temperature during rotation. For this reason,
Unevenness occurs in the crystal growth rate, resulting in a decrease in crystal quality (non-uniform impurity concentration distribution).

In order to increase the crystal growth rate, it is possible to lower the temperature of the melt by lowering the heater power or raising the melt level higher than the soaking zone 25, but in these cases, the conventional In the apparatus, the melt tends to solidify from the crucible side, which inhibits the pulling of the single crystal.

[0005]

[Problems to be Solved by the Invention] The present inventors have attempted to achieve stable single crystal pulling even when the crucible is tilted, to achieve uniform quality of the single crystal, and to speed up crystal growth. , proposed Japanese Patent Application No. 2-322692. In Japanese Patent Application No. 2-322692, as shown in FIG. 8, a reflector 18 is installed on a heat insulating material 15 via a wire 29, a beam 28, and a reflector support 17. This prevents liquid coagulation and achieves high-speed pulling and stable quality.

However, in Japanese Patent Application No. 2-322692, the radiant heat reflecting plate 18 prevents the evaporation of SiO from the melt surface, and as time passes, SiO adheres to the reflecting plate 18, resulting in certain When a certain period of time or more elapses, a problem arises in that SiO adhering to the reflection plate 18 falls onto the surface of the melt and adversely affects the growth of the single crystal. An object of the present application is to provide a single crystal pulling device that can prevent SiO from adhering to a reflector plate and inhibit the growth of single crystals, and can stably and rapidly obtain single crystals with good crystal quality. This is an issue to be addressed.

[0007]

[Means for Solving the Problems] The present invention solves the above problems, and is applied to a single crystal pulling apparatus using the Czochralski method, and employs the following technical means. That is, the position of the melt surface can be made higher than the upper end of the soaking zone of the heating element that heats the melt, and the heat radiation from the melt surface can be directed toward the contact area between the melt surface and the crucible. A reflective plate is provided to surround the single crystal and between the single crystal and the crucible, and an inert gas jet nozzle is provided at the bottom of the reflective plate to prevent deposits from adhering to the reflective surface of the reflective plate. This is a single crystal pulling device characterized by the following.

[0008]

[Operation] FIG. 1 is a longitudinal sectional view of an embodiment of the apparatus of the present invention, FIG. 2 is an explanatory diagram showing the convection state of the melt in the present invention, and FIG. 3 is a comparison of the convection state of the melt in the present invention and the conventional example. FIG. As shown in FIG. 2, by keeping the melt level of the melt 4 at a high position outside the soaking zone 25 of the heating element 12, the heated melt rises in the region 26 outside the soaking zone. The temperature decreases and a downward flow begins to occur near the crucible side wall. As a result, as shown in FIG. 3, the effect of thermal convection is less likely to reach the vicinity of the solid-liquid interface compared to the conventional apparatus, and crystal growth is stabilized.

Furthermore, even if the crucible 5 and the susceptor 6 are tilted during crystal growth, the melt level of the melt 4 can be adjusted by the heating element 1.
As shown in FIG.
The asymmetry in the distance between the For example, suppose that when the distance between the crucible side of the melt and the heating body is 40 mm, the crucible and susceptor are tilted and the center of the melt surface is shifted by 3 mm. At this time, in the conventional apparatus, the melt level of the melt 4 cannot be made higher than the soaking zone 25 of the heating element 12, so as shown in FIG.
1 and the heating body is a maximum of 43 mm and a minimum of 37 mm. Therefore, calculating the ratio is 43÷37=1.
It becomes 162. Compared to this, if the melt level is raised by 50 mm according to the present invention, points A2 and B2 on the crucible side of the melt
The distance between and the heating body is 65.9mm at maximum and 62.9mm at minimum.
It becomes 2mm. Therefore, the ratio is 65.9÷62.2=
1.059, and the non-target is alleviated.

Furthermore, a point A on the melt crucible side from the heating element
The asymmetry of the radiant energy reaching 1 , B1 and A2 , B2 will be explained. From the heating element to the above point A
1 , B1 and A2 , B2 , the radiant intensity of the heating body is I, and the distance between the two is d, and the following equation holds between them.

E=k・I(1/d2) (k is a constant) Therefore, in the conventional method, if the radiant energies at points A1 and B1 are EA1 and EB1, the ratio is (EB1/EA1)=(432/372 )=1.35
becomes. On the other hand, in the present invention, points A2, B2
Letting the radiant energy at EA2 and EB2 be, the ratio is (EB2/EA2)=(65.92/62.
22 )=1.12. Therefore, it can be seen that according to the present invention, the asymmetry of the radiant energy received by the melt can be reduced to about ⅓.

[0012] Therefore, the temperature unevenness at the solid-liquid interface of the crystal becomes weaker than before, and the impurity distribution in the single crystal is also made uniform. Note that when the melt level is increased, solidification occurs from the crucible side. Therefore, by using the reflector plate 18 shown in FIG. 1, which shows a vertical cross section, the thermal radiation from the melt surface is reflected toward the region 19 where the melt surface contacts the crucible, and this region is kept warm. This prevents solidification from the crucible side.

Furthermore, in the present invention, an inert gas jet nozzle is provided at the bottom of the reflector to prevent deposits from adhering to the reflective surface of the reflector, thereby preventing SiO from adhering to the reflector. Therefore, a single crystal with good crystal quality can be stably obtained.

[0014]

Embodiment FIG. 1 shows a longitudinal sectional view of an embodiment of the present invention. Polycrystalline silicon 45 in a quartz crucible 5 with a diameter of 16 inches
kg was charged, and a silicon single crystal with a diameter of 6 inches was grown. Melt level is 10m above the top of heating element 12
m above.

As mentioned in the description of the prior art, simply increasing the melt level causes the melt 4 to start solidifying from the region 19 where the melt contacts the crucible. Therefore, the reflector 18 of the present invention was supported by the gas pipe 30 via the furnace 16. By providing the reflecting plate 18, thermal radiation from the surface of the melt 4 is reflected toward a region 19 where the crucible 5 and the melt 4 are in contact, thereby providing the effect of locally keeping this region warm. The distance between the lower end of the reflector 18 and the melt surface was 50 mm, however, the position of the reflector 18 was not limited to this.
Any location is sufficient as long as the purpose can be achieved. Note that 20 is a crystal growth region.

FIG. 5 shows the reflecting plate 18 of this embodiment. The reflecting plate 18 reflects thermal radiation from the surface of the melt 4 toward a region 19 where the crucible and the melt are in contact, and has the effect of locally keeping this region warm, and is formed in the shape of an inverted conical cylinder. FIG. 5A is a plan view of the reflection plate, and 30 is a gas pipe that supports the reflection plate 18 and supplies inert gas 32 to the injection nozzle 31. FIG. 5(b) shows the reflector 1 of FIG.
8, the reflection plate 18 is at an angle θ with respect to the melt surface.
It is installed so that the angle is 45 degrees. FIG. 5(c) shows a view taken along the line A-A in FIG. 5(b).

That is, in this embodiment, the reflector 18 is supported by eight gas pipes 30, and an inert gas is injected to the tips of the gas pipes 30 to prevent deposits of SiO from adhering to the reflective surface of the reflector 18. As shown in FIG. 1, the other end of the gas pipe 30 is connected to an inert gas supply device (not shown) via a furnace 16 and a heating device 33. Note that the gas injection nozzle 31 has an injection pattern as shown in FIG. 5(c). Therefore, the inert gas will not be injected onto the melt surface and cause the liquid surface to vibrate. Furthermore, since the inert gas has been heated in advance by the heating device 33, the evaporated SiO will not solidify on the reflecting plate 18. Nothing happens.

The shape of the reflector 18 is an inverted conical cylinder as shown in FIGS. 5(a) and 5(b), and the mounting angle θ of the reflector 18 is set to 45 degrees in the area where the crucible and the melt contact. This is to efficiently reflect thermal radiation to the vicinity of 19. Therefore, the shape and angle of the reflector are not limited to those in this embodiment, and may be any shape and angle that can achieve the object of the present invention. In this embodiment, the reflective plate 18 is made of molybdenum, which has high reflectance and excellent heat resistance. However, the material of the reflective plate 18 is not limited to molybdenum, and any material that is heat resistant and has a high reflectance may be used.

As a result of pulling using this example, the melt did not solidify from the crucible side until the end of crystal growth, and the average value of the pulling speed at the crystal body was 1.5% compared to the prior art.
It has increased five times. Further, there was no adhesion of SiO to the reflector, and as a matter of course, there was no possibility that SiO adhering to the reflector would fall onto the melt surface and adversely affect the growth of the single crystal.

FIG. 6 shows a comparison of the standard deviation of the pulling speed with that of the prior art. As can be seen from this figure, in the present invention, there was little variation in the pulling speed, and stable pulling could be achieved. Furthermore, asymmetry in the in-plane distribution of resistivity of wafers manufactured from the pulled crystal was alleviated and made uniform, as shown in FIG. 7 in comparison with the prior art.

[0021]

[Effects of the Invention] By using the single crystal pulling apparatus of the present invention, single crystals could be grown at high speed and at a stable pulling rate. Furthermore,
The quality of the grown crystals was improved, and in particular, the variation in the in-plane distribution of resistivity was reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of one embodiment of the device of the present invention.

FIG. 2 is an explanatory diagram showing the convection state of the melt according to the present invention.

FIG. 3 is an explanatory diagram showing a comparison of the convection state of the melt between the present invention and a conventional example.

FIG. 4 is an explanatory diagram showing a comparison of the positional relationship between the melt and the heating body when the crucible is tilted between the present invention and the conventional example.

FIG. 5 is an explanatory diagram of a reflector in an embodiment of the device of the present invention, FIG. 5(a) is a plan view of the reflector, FIG. 5(b)
) is an enlarged view of the reflection plate 18 in FIG. 1, and FIG. 5(c) shows a view taken along the line A-A in FIG. 5(b).

FIG. 6 is a graph showing the relationship between crystal length and standard deviation of pulling speed in the present invention and the prior art.

FIG. 7 is a graph showing the relationship between the in-plane resistivity of a wafer and the measurement position in the present invention and the prior art.

FIG. 8 is a longitudinal sectional view of the device shown in Japanese Patent Application No. 2-322692.

FIG. 9 is a longitudinal cross-sectional view of an example of a device used to implement the prior art.

FIG. 10 is an explanatory diagram illustrating the temperature change on the melt surface when the crucible is tilted; FIG. 10(a) is a longitudinal cross-sectional view, and FIG. The CC arrow view, FIG. 10(c), is the temperature distribution on the melt surface on the straight line in FIG. 10(b).

[Explanation of symbols]

1 Seed wire
2 Seed chuck 3 Single crystal
4 Melt 5 Crucible
6 Susceptor 7 Pedestal
8 Crucible shaft 9 Insulation material
10 Post 11 Base plate
12 heating element 13 support 14
Electrode 15 Insulating material
16 Furnace 17 Reflector support stand 18 Reflector 1
9 Region where the crucible and the melt surface contact 20 Crystal growth region 21 Region where the melt contacts the crucible side wall 22 Melt surface 23
Thermal convection 24 Convection due to crystal rotation
25 Soaking zone 26 Area outside the soaking zone
27 Single crystal pulling axis 28 Beam
29 wire 30 gas pipe
31 Injection nozzle 3
2 Inert gas
33 Heating device θ angle

Claims (1)

[Claims] Claim 1: In a single crystal pulling device using the Czochralski method, the melt surface can be positioned higher than the upper end of the soaking zone of a heating element that heats the melt, and the heat from the melt surface can be lowered. A reflector that reflects radiation toward the contact area between the melt surface and the crucible is provided surrounding the single crystal and between the single crystal and the crucible, and a reflector of the reflector is provided below the reflector. 1. A single crystal pulling device characterized by being provided with an inert gas jet nozzle for preventing deposits from adhering to the surface.