JPH0331673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a method for setting the initial position of a molten metal in a single crystal pulling apparatus suitable for use in a single crystal manufacturing process using the Czyochralski method.

"Prior Art" FIG. 3 is a sectional view showing the configuration of a conventional single crystal pulling apparatus. In FIG. 3, 1 is a furnace body, and a quartz crucible 2 is provided approximately in the center of the furnace body 1. This quartz crucible 2 is a graphite susceptor 3
The lower end of the graphite susceptor 3 is attached to the upper end of the shaft 4 by a predetermined joining member. In this case, the driving force of the crucible rotating motor and the crucible lifting motor is transmitted to the lower end of the shaft 4, so that the crucible 2 can rotate in a predetermined direction and can also move up and down in the vertical direction. It's summery. 6, 6 are heaters that control the temperature of the molten metal (silicon polycrystalline molten metal) 7 in the crucible 2, and are provided at a predetermined distance apart from the outside of the crucible 2; A heat insulating material 8 is provided in between.

Next, reference numeral 10 denotes a hollow cylindrical upper casing joined to the upper end of the furnace body 1, and a lifting head 11 is provided at the upper end of the upper casing so as to be horizontally pivotable. A wire pulling mechanism (not shown) is provided in the pulling head 11, and a wire cable 13 extends from this wire pulling mechanism toward the center of rotation of the crucible 2. Further, the driving force of the pulling motor 15 is transmitted to the wire pulling mechanism, and the wire cable 13 is pulled up or down depending on the direction of rotation of the pulling motor 15. ing. Also,
The lifting head 11 is a head rotation motor (not shown).
When the driving force is transmitted, it rotates in the direction of arrow TG.

Next, 20 is a seed holder attached to the lower end of the wire cable 13, which holds a seed (single crystal seed) 21 as shown.

In the above configuration, after the seed 21 is immersed in the molten metal 7, the head rotation motor is driven, and
When the pulling motor 15 is driven in the pulling direction, the wire cable 13 is pulled upward while being driven in the direction of the arrow TG, and as the seed 21 rises, the single crystal silicon 22 grows as shown in the figure. go. Further, in this single crystal growth step, the shaft 4 is rotated in a direction opposite to the arrow TG, so that the single crystal silicon 22 and the molten metal 7 are rotated in opposite directions.

Now, single crystal silicon 22 is being pulled up.
It is desirable that the growth shape of the upper end (hereinafter referred to as "top") and lower end (hereinafter referred to as "bottom") correspond to the desired shape.
In addition, it is desirable that the diameter of the straight body portion be uniform to a set diameter value. Since the growth shape and diameter are determined by the pulling speed, molten metal temperature, etc., it is necessary to control the shape and diameter of the single crystal silicon 22 to obtain the desired shape while adjusting these parameters. be.

Therefore, when controlling the diameter, the upper surface of the molten metal 7 is photographed using the television camera 25 through the window 1a provided at the upper end of the furnace body 1, and the image data of the television camera 25 is further analyzed to ensure that the monocrystalline silicon 22
The boundary position between the molten metal and the molten metal surface is detected, the diameter of the single crystal silicon 22 is determined based on the detection result, and each of the above parameters is controlled so that the determined diameter conforms to a predetermined value.

By the way, the surface position of the molten metal 7 is L shown in FIG.
Between the case of position 1 and the case of position L2, a deviation of Δθ occurs in the direction in which the boundary position is detected by the television camera 25, and as a result, a deviation of Δl occurs in the detected diameter value of the single crystal silicon 22. . Therefore, if the molten metal surface position shifts during diameter control,
The diameter of the single crystal silicon 22 deviates from the set value, which is extremely problematic. Therefore, during crystal growth, the position of the molten metal surface should always be maintained at the reference position.
The above-mentioned inconvenience is solved by raising the shaft 4 appropriately. That is, as the single crystal silicon 22 grows, the amount of molten metal in the crucible 2 decreases and the molten metal surface tends to lower, but the shaft 4 is raised by an amount corresponding to the amount of molten metal decrease to lower the molten metal surface position. I try to keep it. In this case, control is performed to maintain the initially set molten metal surface position, so if the initial set position is shifted, the diameter of the straight body will be uniform, but the value will differ from the set value. It becomes a vine.

On the other hand, if the initial position of the molten metal surface is different, a deviation occurs in the relative positional relationship between the molten metal 7 and the heater 6, and as a result, the thermal conditions (convection tracking of the molten metal, etc.) during the single crystal growth process change. As a result, a problem arose in that the oxygen concentration, etc. in the single crystal varied, resulting in non-uniform product quality.

Conventionally, in order to accurately initialize the molten metal surface position, a level measurement system using laser light or the like has been used to initialize the molten metal surface position.

``Problems to be Solved by the Invention'' However, in the conventional method for initializing the molten metal surface position described above, the level measurement system itself is expensive, and a dedicated window section that serves as a passage for the measurement laser beam is required to be installed in the furnace. The disadvantage was that it had to be installed on the body.

This invention was made in view of the above-mentioned circumstances, and it is possible to eliminate the need for an expensive level measurement system, eliminate the need to provide a window for initial position setting on the furnace body, and further improve positioning accuracy. The purpose of this invention is to provide a method for setting the initial position of molten metal in a single crystal pulling apparatus.

"Means for Solving the Problems" In order to solve the above-mentioned problems, this invention
In a single-crystal pulling device that rotates and grows a single crystal from polycrystalline molten metal melted in a crucible, a refractory rod-shaped body that reflects the color of an object in contact with the end surface is attached to the furnace body in which the crucible is housed. arranged in advance so as to extend from the top of the molten metal to near the surface of the molten metal,
and raising the crucible to bring the surface of the molten metal into contact with the end face of the rod-shaped body, further lowering the crucible by a predetermined amount from the time when the color of the rod-shaped body changes due to the contact, The method is characterized in that the surface position of the molten metal at this lowered position is set as the initial position.

"Function" Since the end face position of the rod-shaped body arranged in advance is at a predetermined fixed position, the molten metal surface position lowered by a predetermined amount from this position is always at a constant position.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the configuration of a single crystal pulling apparatus to which an embodiment of the present invention is applied. In FIG. 1, the same reference numerals are given to the parts corresponding to those in FIG. 3 described above, and the explanation thereof will be omitted.

In FIG. 1, 30 is a support rod extending downward from the upper end of the furnace body 1, and one end of a mounting member 31 is fixed to the lower end of the support rod 30. Further, the upper end portion of a quartz rod 32 extending in the vertical direction is joined to the other end of the mounting member 31. This quartz rod 32 is a round rod with a diameter of about 2 mm at the lower end, and the lower end surface is formed flat in the horizontal direction. Also,
The position where the quartz rod 32 is provided is outside the photographing range of the television camera 25 so as not to adversely affect diameter detection. As is clear from the figure, the difference between the apparatus shown in this figure and the conventional apparatus shown in FIG.
The only difference is that 0 to 32 are added.

Next, a method for initial positioning of the molten metal surface according to this embodiment will be explained with reference to FIGS. Note that 40 shown in FIGS. 2A to 2C is an indicator indicating the vertical position of the shaft 4, and has a pointer 40a that moves up and down in conjunction with the shaft 4 and a scale 40b.

First, at the start of initial positioning, the position of the shaft 4 is set downward, so that the surface of the molten metal 7 is aligned with the quartz rod 3.
Make sure that it is sufficiently below the bottom edge of the .
Next, the shaft 4 is gradually raised to bring the surface of the molten metal 7 closer to the lower end surface of the quartz rod 32. And molten metal 7
As the surface of the quartz rod 7 rises, at a certain point, as shown in FIG.
comes into close contact with the surface of the In this case, the color of the molten metal 7 is yellowish vermillion;
The color of the quartz rod 32 is transparent or translucent before it comes into contact with the molten metal 7. And molten metal 7
When the surface of the quartz rod 32 comes into contact with the lower end surface of the quartz rod 32, the quartz rod 32 reflects the color of the molten metal 7 inside, and as a result, the color of the quartz rod 32 changes from transparent (or translucent) to vermilion. That is, the state shown in FIG. 2A is the state at the moment when the quartz rod 32 turns vermilion.

Next, the operator recognizes the color change of the quartz rod 32 from the window 1a, stops the raising of the shaft 4 at this point, checks the indicated value of the indicating section 40, and sets this indicated value as the zero position Po. . Next, as shown in FIG. 2B, the operator lowers the shaft 4 so that the indicated value becomes lower than the zero position Po by Δls. As a result, the surface position of the molten metal 7 is
It will be lower than the lower end surface by an amount corresponding to Δls (the display is an enlarged version of the actual movement).
In this case, Δls is a movement amount that is preset corresponding to the initial position of the molten metal surface. That is, the initial surface position of the molten metal 7 in this embodiment is a position vertically lowered by an amount corresponding to Δls from the lower end surface of the quartz rod 32 (position Ps shown in the figure).
is set to . Therefore, the indicated position of the indicating section 40 shown in FIG. 2B becomes the standard initial position in this case.

Then, in the state shown in FIG. 2B, the seed 21 comes into contact with the surface of the molten metal 7, and from this state, the single crystal pulling operation is started. When this single crystal pulling operation starts, the surface position of the molten metal 7 tends to lower depending on the amount of the single crystal being pulled up.
As described above, the shaft 4 is raised by an amount corresponding to the amount of decrease in the molten metal to maintain the molten metal surface position. FIG. 2C shows a state in which the molten metal surface position is maintained, and as shown in this figure, the shaft 4 is raised so as to keep the molten metal surface position constant.

According to the method described above, even if the amount of molten metal 7 in the initial state varies, the initial surface position of molten metal 7 is always Δls from the lower end surface of quartz rod 32.
It is set exactly at the lower position by the amount corresponding to . According to experiments, the positioning accuracy in this case is as follows when using a laser measurement system (±1
The accuracy was 2 to 4 times (±0.5 mm or less) that of

In the above-described embodiment, the color change of the quartz rod 32 is detected visually by the operator, but instead of this, for example, a photo sensor or the like may be attached to the upper end of the quartz rod 32. Based on the change in the output signal of the photo sensor, the quartz rod 32
The quartz rod 32 may be configured to detect a color change, that is, a contact between the molten metal 7 and the quartz rod 32. Furthermore, axis 4
The vertical position of the molten metal 7 may be detected electrically using a potentiometer or the like, or the initial surface position setting of the molten metal 7 may be completely automated in combination with the photo sensor.

"Effects of the Invention" As explained above, according to the present invention, in a single crystal pulling apparatus that grows a single crystal while rotating it from a polycrystalline molten metal melted in a crucible, the color of the object in contact with the end surface is A refractory rod-shaped body reflecting the above-mentioned temperature is placed in advance so as to extend from the upper part of the furnace body in which the crucible is housed to near the surface of the molten metal, and the crucible is raised so that the surface of the molten metal is exposed to the end face of the rod-shaped body. The crucible was then lowered by a predetermined amount from the time when the color of the rod-shaped body changed due to the contact, and the surface position of the molten metal at this lowered position was set as the initial position. This eliminates the need for a level measurement system, eliminates the need to provide a window for setting the initial position on the furnace body, and also provides the advantage of increasing positioning accuracy.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the mechanical configuration of an embodiment of the present invention, FIGS. FIG. 4 is a cross-sectional view showing the configuration of a conventional single crystal pulling apparatus, and is a schematic view of a molten metal surface for explaining diameter control of a single crystal. 30...Support rod, 31...Mounting member, 32...
Quartz rod (rod-shaped body).

Claims (1)

[Claims] 1. In a single crystal pulling device that rotates and grows a single crystal from a polycrystalline molten metal melted in a crucible, a refractory rod-shaped body that reflects the color of an object in contact with the end surface is placed in a furnace in which the crucible is housed. The crucible is placed in advance so as to extend from the upper part of the body to near the surface of the molten metal, and the crucible is raised to bring the surface of the molten metal into contact with the end face of the rod-shaped body, and the color of the rod-shaped body is changed by the contact. 1. A method for setting an initial position of molten metal in a single crystal pulling apparatus, characterized in that the crucible is lowered by a predetermined amount from the time when the molten metal changes, and the surface position of the molten metal at this lowered position is set as the initial position.