JP3870646B2 - Single crystal pulling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal pulling apparatus for pulling a semiconductor single crystal from a semiconductor melt stored in a crucible using a CZ method (Czochralski method).
[0002]
[Prior art]
In general, a single crystal pulling apparatus using a CZ method is known as one of means for growing a semiconductor single crystal such as silicon (Si) or gallium arsenide (GaAs).
As shown in FIG. 5, this single crystal pulling apparatus stores a semiconductor melt L in a quartz crucible 3 disposed on a susceptor 2 inside a chamber 1, and the semiconductor melt L is placed around the quartz crucible 3. The semiconductor single crystal C is pulled up from the semiconductor melt L by controlling the heating to a predetermined temperature with the cylindrical heater 4 arranged in the above.
Conventionally, in this single crystal pulling apparatus, the susceptor 2 that supports the quartz crucible 3 is formed entirely of carbon.
[0003]
[Problems to be solved by the invention]
However, the following problems remain in the conventional single crystal pulling apparatus. That is, when the raw material in the quartz crucible is melted, the susceptor is also brought into a high-temperature state by heating with the heater, so that there is a disadvantage that the life is shortened due to heat damage.
In addition, it is necessary to control the oxygen concentration as an important characteristic of the silicon single crystal. Conventionally, it has been controlled by changing the settings of the heater shape, crucible position, etc., but the oxygen concentration is controlled with higher accuracy. it is desired.
In order to grow a high-quality crystal, it is necessary to make the temperature distribution uniform in the radial direction at the solid-liquid interface between the semiconductor single crystal C and the semiconductor melt L.
In particular, when the temperature gradient in the growth axis direction at the solid-liquid interface is G in recent years, the growth of COP (Crystal Originated Particles) and the like is reduced by reducing the difference ΔG in the temperature gradient G between the center and the outer periphery of the crystal. It has been found that the occurrence of time-introduced defects can be suppressed. For this reason, it is desired to improve the temperature uniformity of the solid-liquid interface, control ΔG, and reduce it. However, in the conventional apparatus, as shown in FIG. 6, the temperature distribution at the solid-liquid interface is convex downward (the dotted line in the figure is an isotherm).
[0004]
The present invention has been made in view of the above-described problems, and reduces the damage caused by heat by reducing the temperature of the susceptor and controls the temperature distribution of the melt to control the oxygen concentration and the interface temperature distribution with high accuracy. An object of the present invention is to provide a single crystal pulling apparatus capable of achieving the above.
[0005]
[Means for Solving the Problems]
The present invention employs the following configuration in order to solve the above problems. That is,
The single crystal pulling apparatus of the present invention is a single crystal pulling apparatus for pulling up a semiconductor single crystal from a semiconductor melt in a crucible,
A susceptor for placing and supporting the crucible;
The susceptor is provided with a heat insulating material in a part of a portion supporting the crucible bottom,
The heat insulating material is arranged in an annular shape centering on the bottom center of the crucible, and from the crucible bottom center so as to lower the temperature around the crucible bottom center relative to the temperature at the crucible bottom center. It is characterized by being spaced apart.
In the present invention, by providing the heat insulating material, the temperature around the bottom center of the crucible can be lowered, and the temperature distribution at the solid-liquid interface can be made uniform.
In the present invention, when the inner diameter of the heat insulating material is lowered to reduce the oxygen concentration by lowering the semiconductor melt temperature, the inner diameter of the heat insulating material is reduced to positively increase the local temperature of the crucible itself. Can be configured to change.
The temperature distribution control method in the semiconductor melt in the crucible of the present invention is a control method in the single crystal pulling apparatus according to any one of the above,
The temperature distribution in the semiconductor melt in the crucible can be controlled by the position of the heat insulating material.
The present invention provides the above control method,
When the oxygen concentration is lowered by lowering the semiconductor melt temperature, the inner diameter of the heat insulating material can be set so as to set the inner diameter of the heat insulating material small.
The present invention provides the above control method,
Even when the temperature distribution at the solid-liquid interface in the state without the heat insulating material is convex downward, by providing the heat insulating material, the temperature around the bottom center of the crucible is lowered, and the temperature distribution at the solid-liquid interface Can be made uniform.
The present invention provides the above control method,
The difference in temperature gradient in the radial direction ΔG can be reduced by increasing the heater power to compensate for the temperature drop at the outer periphery of the semiconductor single crystal due to the heat insulating material. .
The single crystal pulling apparatus according to the present invention is a single crystal pulling apparatus that pulls up a semiconductor single crystal from a semiconductor melt in a crucible, and includes a susceptor for mounting and supporting the crucible. A technique in which a heat insulating material is provided in the part is adopted.
[0006]
In this single crystal pulling apparatus, since the heat insulating material is provided in a part of the susceptor, the temperature can be relatively lowered in the heat insulating material part, and damage due to heat is reduced. Moreover, since the temperature of the part which has arrange | positioned the heat insulating material can be selectively made low, the temperature in the crucible in the heat insulating material vicinity can also be set low. Therefore, the temperature distribution in the semiconductor melt in the crucible can be controlled by the position of the heat insulating material.
As a result of investigating the relationship between the melt temperature at the bottom of the crucible and the oxygen concentration by simulation or the like, the present inventors have shown that the oxygen concentration depends on the melt temperature at the bottom of the crucible (as shown in FIG. It was found that the higher the melt temperature at the bottom, the higher the oxygen concentration). That is, it has been found that in order to control the oxygen concentration while maintaining the melt interface temperature, it is necessary to positively change the local temperature of the crucible itself. Therefore, based on such knowledge, the configuration of the single crystal pulling apparatus was invented. Therefore, the local temperature of the inner surface of the crucible can be freely changed according to the position, size, shape and material of the heat insulating material. In particular, by arranging the heat insulating material at the bottom of the crucible, the oxygen concentration and the melt temperature distribution. Can be controlled with high accuracy.
[0007]
In a single crystal pulling apparatus of the present invention, the single crystal pulling apparatus described above, the heat insulating material, techniques that are arranged annularly around the bottom center of the crucible are employed.
[0008]
In this single crystal pulling apparatus, since the heat insulating material is arranged in an annular shape centering on the center of the bottom of the crucible, the oxygen concentration is controlled by changing the temperature at the center of the bottom of the crucible by changing the inner diameter of the heat insulating material. be able to. Further, the heat insulating material is disposed away from the crucible bottom center, and the temperature around the bottom center can be relatively lowered with respect to the temperature at the crucible bottom center. Therefore, even when the temperature distribution at the solid-liquid interface is in a downwardly convex state in the absence of the heat insulating material, by providing the heat insulating material, the temperature around the bottom of the crucible bottom is lowered, and the temperature distribution at the solid-liquid interface Can be made uniform. Moreover, although the temperature at the outer peripheral portion of the semiconductor single crystal is relatively lowered by the heat insulating material, if the heater power is increased to compensate for this by heating from the outer periphery, the temperature gradient in the radial direction becomes smaller as a result. G can be reduced.
[0009]
In a single crystal pulling apparatus of the present invention, the single crystal pulling apparatus described above, the heat insulating material, techniques that are disposed facing the bottom center of the crucible are employed.
[0010]
In this single crystal pulling apparatus, since the heat insulating material is arranged facing the center of the bottom of the crucible, the temperature at the center of the bottom of the crucible can be lowered, and oxygen rising from the center of the bottom can be selectively suppressed. , The oxygen concentration can be kept low.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of a single crystal pulling apparatus according to the present invention will be described with reference to FIGS.
In these drawings, reference numeral 11 denotes a chamber, 12 denotes a shaft, 13 denotes a susceptor, 14 denotes a crucible, 15 denotes a heater, and 16 denotes a heat insulating cylinder.
[0012]
FIG. 1 shows a single crystal pulling apparatus according to this embodiment. The single crystal pulling apparatus is vertically installed in a chamber 11 that is a hollow hermetic container and vertically at the lower center of the chamber 11. The shaft 12 is movable up and down, the susceptor 13 placed on the shaft 12, and quartz (SiO ₂₎ for storing the semiconductor melt L, which is placed on and supported by the susceptor 13 and is a silicon melt. ) Made crucible 14, a heater 15 arranged at a predetermined distance from the outer periphery of the crucible 14, and a heat retaining cylinder 16 arranged around the heater 15.
[0013]
Further, this single crystal pulling apparatus includes a substantially cylindrical flow pipe 17 disposed coaxially with the crucible 14 above the crucible 14 and an annular shape attached to the upper part of the heat insulating cylinder 16 and supporting the flow pipe 17. And an upper ring 18.
The crucible 14 is configured to rotate at a predetermined angular velocity on a horizontal plane around the axis of the shaft 12.
The heater 15 heats and melts the silicon raw material in the crucible 14 and keeps the generated semiconductor melt L. Usually, resistance heating is used.
[0014]
The heat insulating cylinder 16 is formed of a heat insulating material 16a made of carbon fiber (carbon fiber), and a carbon plate 16b is stretched as a support plate on the inner surface thereof.
A pull-up wire 19 is suspended from the upper part of the chamber 11 so as to be movable up and down and rotatable. A seed crystal of silicon is fixed to the lower end of the pull-up wire 19.
A transparent window 20 for observing the solid-liquid interface of the semiconductor single crystal C is provided in the upper part of the chamber 11.
[0015]
The flow tube 17 is a tapered cylindrical member whose inner diameter gradually decreases downward, and an upper end flange portion 17 a is fixed to an upper portion of the heat retaining cylinder 16 via an upper ring 18. This flow tube 17 blocks the radiant heat to the semiconductor single crystal C during the growth and allows the argon gas (inert gas) supplied from the gas inlet 11a at the upper end of the chamber 11 to pass therethrough and spray it onto the semiconductor melt L. The SiO2 generated from the semiconductor melt L is blown away. Note that the blown-in argon gas containing SiO 2 is sequentially discharged to the outside from the gas discharge port 11 b at the lower end of the chamber 11.
[0016]
The susceptor 13 is made of carbon, but an annular heat insulating material 13 a centering on the center of the bottom of the crucible 14 is embedded in a part of the portion that supports the bottom of the crucible 14.
The heat insulating material 13a is made of felt-like carbon fiber, for example.
[0017]
When crystal growth is performed in this single crystal pulling apparatus, first, argon gas is supplied from the gas introduction port 11a, and the heater 15 is energized to melt the silicon raw material in the crucible 14 to form the semiconductor melt L, and the heater The power of 15 is adjusted to keep the vicinity of the central liquid surface of the semiconductor melt L at the single crystal growth temperature. Next, the seed crystal suspended by the pull-up wire 19 is lowered and immersed in the semiconductor melt L so as to be dislocation-free by so-called necking, and then the crucible 15 and the pull-up wire 19 are opposite to each other. The semiconductor single crystal C is pulled up and grown while being rotated.
[0018]
In the present embodiment, in the susceptor 13, since the heat insulating material 13a is embedded at a position facing the center of the bottom of the crucible 14, the temperature can be relatively lowered at the portion of the heat insulating material 13a, and damage due to heat is caused. It is reduced. Further, by changing the inner diameter of the heat insulating material 13a, the oxygen concentration can be controlled by changing the temperature at the bottom center of the crucible 14. That is, as shown in FIG. 2, the melt temperature at the bottom of the crucible 14 depends on the inner diameter of the heat insulating material 13a. For example, the smaller the inner diameter, the lower the melt temperature and the lower the oxygen concentration. Therefore, by setting not only the heater shape and crucible position but also the inner diameter of the heat insulating material 13a, a predetermined oxygen concentration can be obtained with high accuracy.
[0019]
Moreover, the heat insulating material 13a will be distribute | arranged to the circumference | surroundings of the bottom center of the crucible 14, and the temperature of the circumference of the bottom part center can be relatively lowered with respect to the temperature of the crucible 14 bottom center. Therefore, even when the temperature distribution at the solid-liquid interface is in a downwardly convex state without the heat insulating material 13a, by providing the heat insulating material 13a, the temperature around the center of the crucible 14 can be reduced as shown in FIG. The temperature distribution at the solid-liquid interface (the dotted line in the figure is an isotherm) can be made uniform (flattened).
[0020]
Furthermore, although the temperature at the outer peripheral portion of the semiconductor single crystal C is relatively lowered by the heat insulating material 13a, it can be compensated by increasing the power of the heater 15 and heating from the outside in the radial direction, resulting in the temperature in the radial direction. The gradient can be reduced and ΔG can be reduced.
Thus, since the temperature of the portion where the heat insulating material 13a is arranged can be selectively lowered, the temperature distribution in the semiconductor melt L can be controlled by the position of the heat insulating material 13a.
[0021]
Next, a second embodiment of the single crystal pulling apparatus according to the present invention will be described with reference to FIG.
[0022]
The difference between the second embodiment and the first embodiment is that in the first embodiment, a susceptor 13 provided with an annular heat insulating material 13a is used, whereas in the second embodiment, it is shown in FIG. Thus, the point which employ | adopts the susceptor 23 which has arrange | positioned the disk-shaped heat insulating material 23a facing the center of the bottom part of the crucible 14 is used.
That is, in this embodiment, the temperature at the bottom center of the crucible 14 can be selectively lowered by the heat insulating material 23a, oxygen rising from the bottom center can be suppressed, and the oxygen concentration can be suppressed low.
[0023]
【The invention's effect】
The present invention has the following effects.
According to the single crystal pulling apparatus of the present invention , since the heat insulating material is provided in a part of the susceptor, the temperature can be relatively lowered in the heat insulating material part, the heat damage is reduced, and the quartz crucible is reduced. Can improve the service life. In addition, since the temperature of the portion where the heat insulating material is arranged becomes low, the temperature distribution in the semiconductor melt in the crucible can be controlled by the position of the heat insulating material, and the oxygen concentration can be controlled.
[0024]
According to the single crystal pulling apparatus of the present invention , since the heat insulating material is arranged in an annular shape centering on the bottom center of the crucible, the ambient temperature can be lowered relative to the temperature at the bottom center of the crucible. it can. Therefore, the temperature distribution of the solid-liquid interface that is in a downwardly convex state can be made uniform. In addition, a relatively low temperature at the outer periphery of the semiconductor single crystal due to the heat insulating material can be compensated by increasing the heater power, resulting in a small temperature gradient in the radial direction and a small ΔG. can. That is, by reducing ΔG, the COP can be reduced and so-called pure silicon can be grown. Therefore, it becomes possible to manufacture a single crystal for a high-performance device.
[0025]
According to the single crystal pulling apparatus of the present invention , since the heat insulating material is arranged facing the center of the bottom of the crucible, the temperature at the center of the bottom of the crucible can be lowered, and oxygen rising from the center of the bottom is suppressed. In addition, a single crystal having a low oxygen concentration can be easily obtained.
[Brief description of the drawings]
FIG. 1 is an overall sectional view showing a first embodiment of a single crystal pulling apparatus according to the present invention.
FIG. 2 is a graph showing the relationship between the inner diameter of the heat insulating material and the melt temperature at the bottom of the crucible in the first embodiment of the single crystal pulling apparatus according to the present invention.
FIG. 3 is a cross-sectional view of the main part showing the temperature distribution of the melt in the crucible in the first embodiment of the single crystal pulling apparatus according to the present invention.
FIG. 4 is an overall cross-sectional view showing a second embodiment of the single crystal pulling apparatus according to the present invention.
FIG. 5 is an overall sectional view showing a conventional example of a single crystal pulling apparatus according to the present invention.
FIG. 6 is a cross-sectional view of the main part showing the temperature distribution of the melt in the crucible in the conventional example of the single crystal pulling apparatus according to the present invention.
FIG. 7 is a graph showing the relationship between the melt temperature at the bottom of the crucible and the oxygen concentration in the conventional example of the single crystal pulling apparatus according to the present invention.
[Explanation of symbols]
13, 23 Susceptors 13a, 23a Heat insulation material 14 Crucible C Semiconductor single crystal L Semiconductor melt

Claims (7)

A single crystal pulling apparatus for pulling a semiconductor single crystal from a semiconductor melt in a crucible,
A susceptor for placing and supporting the crucible;
The susceptor is provided with a heat insulating material in a part of a portion supporting the crucible bottom ,
The heat insulating material is arranged in an annular shape centering on the bottom center of the crucible, and from the crucible bottom center so as to lower the temperature around the crucible bottom center relative to the temperature at the crucible bottom center. A single crystal pulling apparatus characterized by being arranged apart . The single crystal pulling apparatus according to claim 1, wherein
A single crystal pulling apparatus characterized in that by providing the heat insulating material, the temperature around the bottom center of the crucible is lowered and the temperature distribution at the solid-liquid interface is made uniform . The single crystal pulling apparatus according to claim 1, wherein
The inner diameter of the heat insulating material is set so as to positively change the local temperature of the crucible itself by reducing the inner diameter of the heat insulating material when lowering the oxygen concentration by lowering the semiconductor melt temperature. single crystal pulling device characterized by comprising Te. A control method in the single crystal pulling apparatus according to any one of claims 1 to 3,
  A temperature distribution control method in a semiconductor melt in a crucible, wherein the temperature distribution in a semiconductor melt in a crucible is controlled by the position of a heat insulating material. The control method according to claim 4, wherein
  The temperature distribution in the semiconductor melt in the crucible is characterized in that when the semiconductor melt temperature is lowered to lower the oxygen concentration, the inner diameter of the heat insulating material is set so as to reduce the inner diameter of the heat insulating material. Control method. The control method according to claim 4 or 5,
  Even when the temperature distribution at the solid-liquid interface in the state without the heat insulating material is convex downward, by providing the heat insulating material, the temperature around the bottom center of the crucible is lowered, and the temperature distribution at the solid-liquid interface A method for controlling temperature distribution in a semiconductor melt in a crucible, wherein the temperature is uniformized. The control method according to any one of claims 4 to 6,
  The difference in temperature gradient in the radial direction ΔG is reduced by increasing the heater power and heating from the outer periphery to compensate for the temperature drop at the outer periphery of the semiconductor single crystal by the heat insulating material. A temperature distribution control method in a semiconductor melt in a crucible.

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