JPH05208893A - Single crystal pulling apparatus and controlling method therefor - Google Patents

Abstract

PURPOSE:To obtain a crystal having decreased thermal strain of crystal near the solid-liquid interface, low crystal defect content and microscopically uniform oxygen concentration by rotating a crystal pull-up shaft relative to a crucible supporting rod. CONSTITUTION:A crucible 53 made of graphite or quartz, etc., is placed in an air-tight vessel 51. A cylindrical graphite heater 59 for melting a polycrystalline semiconductor raw material 57, etc., at a high temperature is placed at the outside of the crucible. The semiconductor raw material 57 melted by the heat of the heater is made to contact with a seed crystal 63 attached to a crystal pull-up shaft 61 and the seed crystal 63 is pulled up while rotating the seed crystal 63 and/or the crucible 53 to effect the growing of a single crystal 64. When the rotational speed of the crucible 53 is set to >=100rpm, the solid-liquid interface is flattened and, as a result, the thermal strain of the crystal near the solid-liquid interface is decreased to obtain a crystal having low defect content. A definite amount of oxygen is constantly supplied by the stirring effect of the melt at a high rotational speed of the crucible to form a crystal having microscopically uniform oxygen concentration in the direction of the crystal length.

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 and its control method, and more particularly to a single crystal pulling apparatus and its control method for maintaining the quality of a single crystal.

[0002]

2. Description of the Related Art Conventionally, a single crystal pulling apparatus of this type is shown in FIG.
As shown in FIG. Airtight container 51
A crucible 53 made of graphite, quartz (silica) or the like is provided inside, and a cylindrical graphite heating element 59 for melting the semiconductor material 57 such as polycrystalline material inserted in the crucible 53 at a high temperature is provided outside thereof. A (graphite heater 59) is provided. The semiconductor material 57 melted in the crucible 53 by the heat of the graphite heater 59 is brought into contact with the seed crystal 63 attached to the crystal pulling shaft 61, and the seed crystal 63 or the crucible 53.
Alternatively, the single crystal 64 is grown by pulling the seed crystal 63 while rotating both. The rotation speed of the pulling shaft is 10 rpm to 30 rp in order to make the melt stirring and temperature uniform.
The rotation speed of the support shaft 69 of the crucible 53 is 3 rpm to m.
It is set to 10 rpm, and is usually rotated at 30 rpm or less. In the above-mentioned conventional example, the pressure reduction is described, but the atmospheric pressure is similarly configured.

[0003]

However, in a single crystal pulling apparatus by the Czochralski method (hereinafter referred to as the CZ method), in the crucible rotation range of usually 30 rpm or less, the solid-liquid interface shape becomes higher as shown in FIG. The shape is a convex shape (C), and as shown in FIG. 10, the shape of the crystal growth interface is pulled up in a state where thermal strain is likely to occur. Also,
In this case, there is a problem that the convection mode period of the melt becomes about several to several tens of seconds and microscopic unevenness occurs in the oxygen concentration in the longitudinal direction of the pulled crystal. The present invention focuses on the above problems, and relates to a single crystal pulling apparatus and a control method thereof, and more particularly to an improvement of a single crystal pulling apparatus and a control method thereof for maintaining the quality of a single crystal.

[0004]

In order to achieve the above object, in the first invention of the single crystal pulling apparatus and the control method thereof according to the present invention, the inside of the crucible is rotated while rotating the crystal pulling shaft and the crucible support rod. In a single crystal pulling apparatus for growing a crystal from a melt or a solution and pulling the crystal with a crystal pulling shaft, the crystal pulling shaft and the crucible support rod are relatively rotated to bring the single crystal and the melt in the crucible to 100 rp.
Rotate at m or more to grow a single crystal.

According to the second aspect of the invention, a single crystal pulling apparatus for growing a crystal from a melt or a solution in a crucible while pulling the crystal on the crystal pulling axis while rotating the crystal pulling axis and the crucible support rod is used. And a command to rotate the crucible support rod relative to each other at a predetermined value of 100 rpm or more are measured, the actual rotation speeds of the crystal pulling shaft and the crucible support rod are measured, and the command value and the measured value are compared and the value is compared. When is out of the predetermined value, the rotation speed of the crystal pulling shaft is changed. In addition, in the third invention, which is mainly based on the second invention, the crystal pulling shaft and the crucible support rod are set to be relatively close to each other.
The crucible support rod is rotated faster than the crystal pulling shaft to rotate at rpm or more.

[0006]

According to the above structure, the rotation speed of the crucible is 100%.
By setting it to be rpm or more, the melt liquid surface shape becomes a parabolic surface having a downward convex shape. Therefore, when the crystal was pulled in this state, the solid-liquid interface shape was convex upward in the normal crucible rotation speed range, but the melt liquid surface shape and the solid-liquid interface shape were canceled out, and the solid-liquid interface shape was Becomes flat. As a result, crystal thermal strain near the solid-liquid interface is reduced, and a crystal with low defects can be obtained. Further, in a high-speed crucible rotation state, a constant oxygen is constantly supplied by the stirring effect of the melt, so that a crystal having a microscopically uniform oxygen concentration in the crystal length direction can be obtained. Furthermore, by rotating the crucible support rod at a high speed, shaking and swinging of the single crystal rod are reduced, and the device is simplified.

[0007]

Embodiments of a single crystal production apparatus and a control method therefor according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a first embodiment of a single crystal manufacturing apparatus of the present invention. Note that, in FIG. 1, the same parts as those of the related art are designated by the same reference numerals and the description thereof will be omitted. The single crystal manufacturing apparatus has, for example, an airtight container 1 as shown in FIG. 1, and the airtight container 1 is composed of a container 1a and a pulling chamber 1b composed of a stretchable portion such as a bellows. A crucible 53 is provided in the container 1, and a graphite heater 59 for melting a semiconductor material 57 such as a polycrystalline material inserted in the crucible 53 at a high temperature is arranged outside the crucible 53. The semiconductor material 57 melted in the crucible 53 by the heat of the graphite heater 59 is brought into contact with the seed crystal 5 attached to the crystal pulling shaft 3, and the seed crystal 5 or the crucible 53 or both are rotated to pull up the seed crystal 5. The crystal 7 is grown. The crucible 53 is held by the crucible support rod 9 and is rotated by the drive motor 11 via the chain belt 13.

A rotating device 20 for rotating the seed crystal 5 via the crystal pulling shaft 3 is disposed in the upper part of the pulling chamber 1b, and the rotating device 20 comprises a rotation motor 21 and a chain belt 23. There is. A pulling device 30 for pulling the grown single crystal 7 is disposed in the pulling chamber 1b, and the pulling device 30 includes a pulling motor 31 and a ball screw 33. Further, in the pulling chamber 1b, a bearing 35 for supporting the crystal pulling shaft 3 and a slider 37 for preventing the swinging or swinging of the crystal pulling shaft 3 are provided.
Is stored. The slider 37 has one end fixed to the container 1a and the other end fixed to the slider rod 37a fixed to the upper member 39 of the pulling chamber 1b, and to the slider rod 37a.
Also, a slider holding member 37 for holding the crystal pulling shaft 3
It consists of b. The slider rod 37a is a pulling device 30.
Along with the expansion and contraction, the bellows pivotally expands and contracts in the vertical direction shown in the figure, but the slider holding member 37b is fixed at a predetermined position so that the crystal pulling shaft 3 does not swing or swing.

The crystal pulling shaft 3 is provided with a pulling shaft rotation sensor 41, and the crucible support rod 9 is provided with a crucible rotation sensor 43. A detection signal is sent to the controller 40 to detect the rotation speed of each rotation shaft. ing. In the above-mentioned configuration, an example in which each shaft is driven via a chain belt is described, but without being limited to this example, a shaft direct motor may be arranged or driven via a gear. ..

In the above structure, the semiconductor material 57 melted in the crucible 53 is brought into contact with the seed crystal 3 attached to the crystal pulling shaft 1 and grows while the single crystal rod is gently pulled while rotating. Go. At this time, for example,
Crystals were grown at a rotation speed of the crucible support rod 9 of 80 rpm, a rotation speed of the crystal pulling shaft 3 of 20 rpm, and a crucible rotation speed of 100 rpm. As a result, as shown in FIG. Shows a downwardly convex parabolic surface (A), and the solid-liquid interface shape is flat (B). As a result, the crystal thermal strain near the solid-liquid interface is reduced, the shape of the crystal growth interface is flat as shown in FIG. 3, and a low defect crystal is obtained. Further, in a crucible rotating state at a high speed, a constant oxygen is constantly supplied due to the stirring effect of the melt, so that the oxygen concentration in the crystal length direction is as shown in FIG. 4, and as shown in FIG. Is obtained.

Also, substantially the same is true when the above-mentioned rotation is performed by setting the rotation speed of the crucible support rod 9 to 180 rpm, the rotation speed of the crystal pulling shaft 3 to 20 rpm, and the crucible to a rotation speed of 200 rpm. Good results were obtained.

The control method in the above embodiment will be described with reference to the flowchart of FIG. In step 1, a command for the rotation speed Mrpm of the crucible support rod 9 is issued.
In step 2, a command for the rotation speed N rpm of the crystal pulling shaft 1 is issued. By this command, the crucible 53 relatively rotates at a predetermined value α (100 rpm or more).

At this time, in step 3, the crucible support rod 9
The actual rotation speed Prpm of the crucible rotation sensor 43
Then, the rotation speed Qrpm of the crystal pulling shaft 1 is measured by the pulling shaft rotation sensor 41. The detection signal is sent to the controller 40, and the controller 40, like step 4,
The crucible 53 determines whether or not the rotation speed is relatively at a predetermined command value. If the actual rotation speed is the command value, the process returns to step 1. If no, step 5
Then, from the difference between the rotation speed of the crucible 53 having a predetermined value and the actual rotation speed, the difference is obtained in the controller 40 so that the actual rotation speed of the crucible 53 becomes the predetermined value α, and the difference is calculated in step 5. Correction value N ₁ r for rotation speed of crystal pulling shaft
pm is obtained, the process returns to step 2, and the rotation speed N ₁ r of the crystal pulling shaft 1 is adjusted so that the rotation speed of the crucible 53 becomes a predetermined value.
Issue pm command.

When the above-mentioned embodiment and the conventional example are compared and tested, the rotation speed and solid-liquid interface shape of the crucible shown in FIG.
Crucible rotation speed and micro oxygen concentration fluctuation in the crystal axis direction. The rotation speed of the crucible shaft is approximately 150 rpm
The oxygen concentration fluctuation in the micro axial direction is reduced.

Even if the rotation speed of the crystal pulling shaft 1 is controlled to the same level so that the rotation speed of the crucible 53 becomes a predetermined value as in the above embodiment (for example, the rotation speed of the crucible 53 has an error of 100 rpm). If it is 1%, it will be 5% when the rotation speed of the crystal pulling shaft 1 is 20 rpm.) While the control is improved, the moment of inertia of the crystal pulling shaft 1 is smaller than that of the crucible support rod 9, so that the control can be performed quickly.

[0016]

As described above, in the apparatus for pulling a single crystal and the method for controlling the same according to the present invention, the crucible is rotated at a high speed so that the melt liquid surface shape becomes a downward parabolic shape. As a result, the melt liquid surface shape and the solid-liquid interface shape are canceled out, and the solid-liquid interface shape becomes flat. As a result, crystal thermal strain near the solid-liquid interface is reduced, and crystals with low defects are obtained. Further, in a high-speed crucible rotation state, a constant oxygen is constantly supplied by the stirring effect of the melt, so that a crystal having a microscopically uniform oxygen concentration in the crystal length direction can be obtained. Furthermore, by rotating the crucible support rod at a high speed, shaking and swinging of the single crystal rod are reduced, and since the rotation speed of the crystal pulling shaft is controlled, the rotation speed can be controlled accurately and the device can be simplified. Excellent effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram of an embodiment of a single crystal pulling apparatus of the present invention.

FIG. 2 is a detailed cross-sectional view of a crucible portion of the single crystal pulling apparatus of the present invention.

FIG. 3 is a diagram showing a shape of a growth interface of a crystal of the present invention.

FIG. 4 is a diagram showing a relationship between oxygen concentration and crystal length according to the present invention.

FIG. 5 is a view showing a flow chart of rotation control of the single crystal pulling apparatus of the present invention.

FIG. 6 is a schematic overall configuration diagram of an example of a conventional single crystal pulling apparatus.

FIG. 7 is a diagram showing a crucible rotation speed and a solid-liquid interface shape according to the related art and the present invention.

FIG. 8 is a diagram showing a crucible rotation speed and microscopic oxygen concentration fluctuations in the crystal axis direction of the conventional and the present invention.

FIG. 9 is a detailed sectional view of a crucible portion of a conventional single crystal pulling apparatus.

FIG. 10 is a diagram showing the shape of a conventional crystal growth interface.

[Explanation of symbols]

 1 Airtight container 3 Crystal pulling shaft 5 Seed crystal 7 Single crystal 9 Crucible support rod 11 Drive motor 13,23 Chain belt 20 Rotating device 21 Rotating motor 30 Pulling device 31 Pulling motor 33 Ball screw 40 Controller 41 Rotating sensor for pulling shaft 43 Rotation sensor for crucible 51 Airtight container 53 Crucible 59 Cylindrical graphite heating element

Claims (3)

[Claims] 1. A single crystal pulling apparatus for growing a crystal from a melt or a solution in a crucible while rotating the crystal pulling shaft and the crucible support rod, and pulling the crystal on the crystal pulling shaft, the crystal pulling shaft and the crucible support rod. Is relatively rotated, and the single crystal and the melt in the crucible are rotated at 100 rpm or more to grow the single crystal. 2. A single crystal pulling apparatus for growing a crystal from a melt or a solution in a crucible while rotating the crystal pulling shaft and the crucible support rod, and pulling the crystal on the crystal pulling shaft, the crystal pulling shaft and the crucible support rod. And a command to rotate at a predetermined value of 100 rpm or more are measured, the actual rotation speeds of the crystal pulling shaft and the crucible support rod are measured, and the command value and the measured value are compared to obtain a predetermined value. A control method for a single crystal pulling apparatus, which is characterized in that a change value is given to the rotational speed of the crystal pulling shaft when the single crystal pulls up. 3. The single crystal pulling apparatus according to claim 2, wherein the crucible support rod is rotated faster than the crystal pulling shaft in order to rotate the crystal pulling shaft and the crucible supporting rod relatively at 100 rpm or more. Control method.