JPS6287481A - Method of setting the initial melting position in single crystal-pulling-up apparatus - Google Patents

Abstract

PURPOSE:A refractory rod is brought into contact with the surface of the polycrystalline melt, and the crucible is allowed to go down in a prescribed height, when the color of the rod has changed and the resultant surface level is regarded as the initial position whereby the melt surface is positioned with high accuracy. CONSTITUTION:The polycrystalline melt 7 in the crucible 2 is raised up with the shaft 4 to get into contact with a rod 30 which extends down from the oven 1 between the refractory rod end 32 and the melt surface to reflect the color of the melt to the inside of the rod end 32. When the surface reaches the rod end 32, the shaft 4 is stopped and the indication of the indicator 40 is set to P0. Then, the shaft 4 is allowed to go down by a prescribed distance DELTAls and the point is regarded as the surface level of the melt 7 40a, represented by Ps. Then, the seed 21 is brought into contact with the surface of the melt 7 to start pulling up the seed crystal. The shaft 4 is pushed up in correspondence to the level down of the melt which is caused by pulling up the single crystal to keep the surface level of the melt constant.

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 Czochralski method.

"Prior Art" FIG. 3 is a sectional view showing the configuration of a conventional single crystal pulling apparatus. In FIG. 3, ``■'' is a furnace body, and a quartz crucible 2 is provided approximately at the center of the furnace body l. This quartz crucible 2 is held by a graphite susceptor 3, and the lower end of the graphite susceptor 3 is attached to the upper end of a 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 has become. 6.6 is a heater that controls the temperature of the molten metal (silicon polycrystalline molten metal) 7 in the crucible 2, and is provided outside the crucible 2 at a predetermined distance. A heat insulating material 8 is provided in the gap.

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 portion of this upper casing so as to be horizontally pivotable.

A wire pulling mechanism (path shown) is provided in the pulling head II, 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 I3 is pulled up or down depending on the rotational direction of the pulling motor 15. . Moreover, the pulling head 11 is
When the driving force of the head rotation motor (the path shown) is transmitted, the head rotates in the direction of the arrow TG force.

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 the pulling motor I5
When driven in the pulling direction, the wire cable 13 moves in the direction of arrow T.
The seed 21 is pulled upward while being driven in the direction of the G force, and as the seed 21 rises, the single crystal silicon 22 grows as shown. 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, it is desirable that the growth shape of the single crystal silicon 22 that is being pulled corresponds to the desired shape at the upper end (hereinafter referred to as top) and the lower end (hereinafter referred to as bottom). It is desirable to make the diameter uniform in the part. 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.

5. When controlling the diameter of the iron, the top 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 make simple measurements. The boundary position between the crystalline silicon 22 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, when the surface position of the molten metal 7 is at the position Ll shown in FIG. 4 and when it is at the position L2, a deviation of Δθ occurs in the direction in which the boundary position is detected by the television camera 25.
As a result, a deviation of ΔI occurs in the detected diameter value of the single crystal silicon 22. Therefore, if the molten metal surface position deviates 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 shaft 4 is raised appropriately so that the position of the molten metal surface is always maintained at the reference position to eliminate the above-mentioned inconvenience.

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 between 4 and -, but that value will be the set value. It becomes something different.

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

Therefore, in the past, in order to accurately initialize the molten metal surface position, a level measurement system using laser light, etc. was used.
In this way, the initial setting of the molten metal surface position was performed.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method for initializing the molten metal surface position, the level measurement system itself becomes expensive, and a dedicated window section that serves as a passage for the measurement laser beam is required 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 has an object 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 two problems, this invention is a single crystal pulling device that grows a single crystal while rotating it from a polycrystalline molten metal melted in a crucible. A refractory rod-shaped body reflecting the color of the object in contact with the end surface is placed in advance so as to extend from the second part of the furnace body in which the crucible is housed to near the surface of the molten metal, and the crucible is The surface of the molten metal is brought into contact with the end face of the rod-shaped body, and the crucible is lowered by a predetermined amount from the time when the color of the rod-shaped body changes due to the contact, and the crucible is lowered to this lowered position (J The surface position of the molten metal 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 addition, in Figure 1,
Components corresponding to those shown in FIG. 3 described above are given the same reference numerals and their explanations will be omitted.

In FIG. 1, 30 is a support rod extending downward from the upper end of the furnace body I, and a mounting member 3 is attached to the lower end of the support rod 30.
One end of 1 is fixed. 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 its lower end, and the lower end surface is formed flat in the horizontal direction.

Further, 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 only difference between the apparatus shown in this figure and the conventional apparatus shown in FIG. 3 is that the above-mentioned components 30 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. 2(A) to 2(C). In addition, 40 shown in FIGS. 2(a) to 2(c) is an indicator indicating the up and down position of the shaft 4, and has a pointer 40a that moves downward by two degrees in conjunction with the shaft 4, and a scale 40b. ing.

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 sufficiently below the lower end surface of the quartz rod 32.

Next, the shaft 4 is gradually raised to touch the surface of the molten metal 7 with the quartz rod 32.
Move it closer to the lower end of the . As the surface of the molten metal 7 rises, at a certain point, the lower end surface of the quartz rod 7 and the surface of the molten metal 7 come into contact with each other, as shown in FIG. 2(A). In this case, the color of the molten metal 7 is yellowish vermilion, while the color of the quartz rod 32 is transparent or translucent before it comes into contact with the molten metal 7. and,
When the surface of the molten metal 7 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. 2(a) 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 to the zero position Po.
shall be. Next, the operator lowers the shaft 4 as shown in FIG.
so that it is only as low as possible. As a result, the surface position of the molten metal 7 becomes lower than the lower end surface of the quartz rod 32 by an amount corresponding to 8σS (the display is enlarged from the actual movement). In this case, ΔQs is a preset movement amount 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 set at a position vertically lower than the lower end surface of the quartz rod 32 by an amount corresponding to Δ12S (position Ps shown in the figure). Therefore, the instruction section 40 shown in FIG.
The indicated position becomes the reference initial position in this case.

Then, in the state shown in FIG. 2(b), 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 according to the amount of the single crystal being pulled up, so as mentioned above, The molten metal surface position is maintained by raising the shaft 4 by a certain amount.Figure 2 (C) shows the operation state of the molten metal surface position holding operation, and as shown in this figure, the molten metal surface position is kept constant. Axis 4 is rising.

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 accurately positioned below the lower end surface of quartz rod 32 by an amount corresponding to ΔQs. Set.

According to experiments, the positioning accuracy in this case is approximately ±1++u++ when using a laser measurement system.
The accuracy was 2 to 4 times (±0, 5 mm or less).

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 photosensor or the like is attached to the upper end of the quartz rod 32, and this photosensor The configuration may be such that a change in the color of the quartz rod 32, that is, a contact between the molten metal 7 and the quartz rod 32, is detected from a change in the output signal. moreover,
The vertical position of the shaft 4 may be detected electrically using a potentiometer or the like, or the initial position setting of the surface 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. Further, the crucible is lowered by a predetermined amount from the time when the color of the rod-shaped body changes due to the contact, and the surface position of the molten metal at this lowered position is set as the initial position. This has the effect of eliminating the need for a measurement system and the need to provide a window for setting the initial position on the furnace body, and
There is also the advantage that positioning accuracy can be increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the mechanical configuration of an embodiment of the present invention, and FIGS. 2(A) to 2(C) are sectional views each illustrating a method of setting the initial position of the molten metal surface in the same embodiment. FIG. 3 is a sectional view showing the configuration of a conventional single crystal pulling apparatus, and FIG. 4 is a schematic view of the surface of a molten metal for explaining diameter control of a single crystal. 30...Support rod, 31...Mounting member,
32...Quartz rod (rod-shaped body).

Claims (1)

[Claims] 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. is arranged in advance so as to extend from the top of the crucible 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 surface of the rod-shaped body, and further, the color of the rod-shaped body changes due to the contact. 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 a point in time, and the surface position of the molten metal at this lowered position is set as an initial position.