JPH0331674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a single crystal manufacturing apparatus suitable for use in manufacturing, for example, silicon single crystals.

"Prior Art" FIG. 4 is a sectional view showing the configuration of a general single crystal manufacturing apparatus. In FIG. 4, 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 rotatable. A wire pulling mechanism 12 is provided in the pulling head 11, and a wire cable 13 extends from the wire lifting mechanism 12 toward the center of rotation of the crucible 2. The driving force of a pulling motor 15 is transmitted to the wire pulling mechanism 12, and the wire cable 13 is pulled up or down depending on the direction of rotation of the pulling motor 15. ing. Further, the lifting head 11 is configured to rotate in the direction of arrow TG when the driving force of the head rotation motor 16 is transmitted.

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, when the head rotation motor 16 is driven and the pulling motor 15 is driven in the pulling direction, the wire cable 13 is moved upward while being driven in the direction of the arrow TG. As the seed 21 rises, single crystal silicon 22 grows as shown in the figure. 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.
Further, it is desirable that the straight body portion has a uniform diameter. The growth shape is determined by the pulling speed, the temperature of the molten metal, the relative rotational speed of the single crystal silicon 22, and the liquid level of the molten metal.
It is necessary to control these parameters so that the shape of the single crystal silicon 22 becomes a desired shape.

This shape control is carried out by photographing the upper surface of the molten metal 7 with a television camera 25 through the window 1a provided at the upper end of the furnace body 1, and further analyzing the image data of the television camera 25 to determine whether the monocrystalline silicon 22 and the molten metal liquid surface are The boundary position is detected, and each of the above parameters is controlled based on the detection result so that the outer shape of the single crystal silicon 22 follows a predetermined shape. Furthermore, as the single crystal silicon 22 grows, the liquid level of the molten metal in the crucible 2 decreases, but the drop in the liquid level of the molten metal changes the diameter of the single crystal silicon 22 and has an adverse effect on the growth shape. 4 to keep the liquid level constant.

"Problems to be Solved by the Invention" By the way, in the manufacturing process of the single crystal silicon 22, it is extremely important to accurately detect the matters described below.

When the seed 21 is lowered, contact between the molten metal 7 and the seed 21 is detected. After this contact is detected, the seed 21 is raised and the growth process immediately begins.

When the growth of the crystal is finished and the bottom shape is adjusted, the molten metal 7 and the single crystal silicon 22 are separated, but the moment of separation is detected and the process moves to a crystal cooling process.

During the growth of single crystal silicon 22, the amount of decrease in molten metal 7 is accurately detected, and crucible 2 is raised by an amount corresponding to the amount of decrease.

However, in the above-mentioned conventional single crystal manufacturing apparatus, the above-mentioned detection items were carried out by visual inspection, which caused a problem in terms of accuracy. In addition, regarding the detection items, the amount of molten metal reduction is not directly detected, but the amount of molten metal reduction is calculated based on the values of each control parameter, data obtained in advance, etc., and the crucible 2 is raised in accordance with this calculation result. Because of the control, errors often occur in the actual amount of reduction, resulting in a problem that the diameter of the straight body portion becomes non-uniform.

This invention was made in view of the above-mentioned circumstances, and it is possible to automatically and accurately detect the contact between the seed and the molten metal, the separation between the bottom part and the molten metal, and the lowering of the surface position due to a decrease in the molten metal. The purpose is to provide a single crystal manufacturing device that can produce single crystals.

"Means for Solving the Problems" In order to solve the above problems, the present invention provides a seed attached via a seed holder to the lower end of a wire cable suspended from a device frame, and a polycrystalline molten metal inside. is provided with an insulating crucible in which the crucible is housed, and an electrically conductive support member that covers and supports the crucible, and the seed is brought into contact with the molten metal and then pulled up, whereby the lower end of the seed In a single crystal manufacturing apparatus for growing a single crystal, the wire cable is insulated from the apparatus frame, and the capacitance between a part electrically connected to the wire cable and a part electrically connected to the support member is provided. It is equipped with a capacitance detection section that detects.

"Operation" The contact between the seed and the molten metal, the amount of decrease in the molten metal due to the growth of the single crystal, and the separation between the growing single crystal and the molten metal appear as changes in the detection signal of the capacitance detection section.

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

FIG. 1 is a schematic configuration diagram showing the configuration of an embodiment of the present invention, and parts corresponding to those shown in FIG.

In FIG. 1, 30 is an insulating material that insulates the lifting head 11 and the upper casing 10. Next, 32 is a capacitance meter, and a high frequency oscillator 31 is provided between one input terminal of the capacitance meter and the lifting head 11.
The other input terminal of is connected to the upper casing 10 and the shaft 4 and is grounded. In this case, the capacitance meter 32 detects the capacitance to be detected from the value of the current flowing between both input terminals, and the output signal of the capacitance meter 32 is sent to the amplifier 34 and the comparator. 33, respectively. Further, the comparator 33 outputs an "H" level signal when the output signal of the capacitance meter 32 exceeds a predetermined threshold value, and outputs an "L" level signal when it is below the threshold value.

Next, 35 is the comparator 33 and the amplifier 3
This is a control unit that controls each part of the device based on the output signals of
ROM and various data are temporarily stored
It consists of RAM etc. In this case, the control unit 35
supplies a control signal to the motor drive circuit 38 via the interface 36, thereby controlling the rotation of the crucible lifting motor 39 and adjusting the vertical position of the crucible 2. The control unit 35 also controls the pulling motor 15 and the head rotation motor 16 via an interface 37 in order to control the shape of the single crystal 22 based on the image signal from the television camera 25.
is controlled, thereby adjusting the pulling speed and seed rotation speed, and further adjusting the amount of heat generated by the heaters 6, 6 via a path not shown.

Next, the operation of this embodiment with the above configuration will be explained. First, the control unit 35 lowers the wire cable 13 in order to bring the seed 21 into contact with the molten metal 7. In this case, before the seed 21 comes into contact with the molten metal 7, the capacitance to be detected by the capacitance meter 32 is as follows. That is, the pulling head 11, the wire cable 13, the seed holder 20,
A series of conductors consisting of the conductor and the seed 21 becomes the first electrode, and the graphite susceptor 3, the shaft 4, and the part electrically connected to these become the second electrode. The capacity to be detected is the capacity to be detected. Since the distance between the first and second electrodes is relatively large, the capacitance formed in this case becomes extremely small, as shown in period T ₁ in Figure 2. .

Next, when the seed 22 descends and comes into contact with the molten metal 7, the seed 22 and the molten metal 7 are electrically connected, so the molten metal 7 is added to the first electrode, and as a result, the first and second electrodes are connected to the crucible. (Quartz crucible) 2 is placed in close proximity to the dielectric. in this case,
The capacitance with the crucible 2 as a dielectric is relatively large because the distance between the electrodes is small and the area where the electrodes face each other is large. Therefore, the detected value of the capacitance meter 32 is a large value. Become. and,
For example, at time t ₁ shown in FIG.
When the capacitance meter 32 comes into contact with the molten metal 7, the detected value of the capacitance meter 32 suddenly increases at time _t1 . The threshold value of the comparator 33 shown in FIG. ₁ is set to a value that can detect a sudden change in capacitance as shown in FIG. changes from “L” level to “H”
rise to the level. Then, the control unit 35 detects the contact between the seed 21 and the molten metal 7 from the change in the output signal of the comparator 33, and thereby reverses the pulling motor 15 to perform the pulling process of the seed 21, that is, the growth process of the single crystal 22. to move to.

Next, when the single crystal growth process starts from time _t1 , the amount of molten metal 7 in the crucible 2 decreases according to the amount of growth of the single crystal. Then, as the molten metal 7 decreases, the surface area of one electrode (the tip of the first electrode) of the capacitance with the crucible 2 as a dielectric gradually decreases, and as a result, the value of the capacitance decreases to the Period T ₂ in Figure 2
As shown in , it decreases according to the amount of molten metal decrease.
Then, the control unit 35 calculates, from the amount of decrease in the capacitance value,
The relative decrease amount of the molten metal surface position in the crucible 2 is determined, and the crucible lifting motor 39 is driven by the amount corresponding to the determined surface position decrease amount, thereby maintaining the absolute surface position of the molten metal 7 at a constant position. do. In this case, since the amount of decrease in the molten metal 7 definitely appears as a change in the capacitance electrode area, the controller 3
Since the amount of decrease in the molten metal detected by 5 is extremely accurate, it is possible to accurately instruct the amount of drive of the crucible lifting motor 39 for stabilizing the molten metal surface position. In addition, in the period T ₂ , the period T ₂ a in which the capacitance decreases somewhat rapidly corresponds to a state in which the remaining amount of the molten metal 7 is small, and the molten metal 7
As shown in FIG. 3, the surface of the crucible 2 is located at a curved portion (so-called rounded portion) 2a at the bottom of the crucible 2. That is, in this state,
The cross-sectional area of the crucible 2 gradually decreases as it goes downwards, so even if the amount of molten metal decreases is the same, the surface position within the crucible 2 decreases at a faster rate than when the cross-sectional area is constant. It becomes faster.
Therefore, in such a state, it is necessary to increase the rate of rise of the crucible 2, but in the case of this example, the change in the shape of the crucible 2 is also reflected as a change in capacitance, as described above. Therefore, the crucible 2 can be raised accurately in accordance with the lowering of the surface position of the molten metal 7. In this way, the capacitance change during the period T ₂ accurately reflects the relative surface position of the molten metal 7 within the crucible 2, regardless of the cross-sectional area change of the crucible 2.

Next, at time t ₂ shown in FIG.
2 has finished growing and the bottom shape is controlled,
The lower end of the bottom and the molten metal 7 are separated. After this separation, the first electrode is constituted by a series of conductors including the wire cable 13, the seed holder 20, the seed 21, and the single crystal 22. In this case, since the first electrode and the second electrode are spatially separated and their opposing area is small, the detected capacitance is significantly reduced. Then, this rapid decrease in capacitance becomes lower than the threshold value of the comparator 33, whereby the output signal of the comparator 33 changes to "L" level, and the control unit 35 controls the change in the output signal of the comparator 33. The separation between the bottom and the molten metal 7 is detected. After the separation is detected, the process moves to a crystal cooling process.

As described above, in this embodiment, based on the output signal of the capacitance meter 32, the contact between the seed and the molten metal, the lowering of the molten metal surface position in the crucible, and the separation of the bottom and the molten metal are very accurately determined. And it can be detected automatically. Therefore, automation of the single crystal manufacturing process can be greatly promoted.

"Effects of the Invention" As explained above, according to the present invention, a seed is attached via a seed holder to the lower end of a wire cable suspended from a device frame;
An insulating crucible in which a polycrystalline molten metal is stored and a conductive support member that covers and supports the crucible are provided, and the seed is brought into contact with the molten metal and then pulled up, thereby In a single crystal manufacturing apparatus for growing a single crystal at the lower end of the seed, the wire cable is insulated from the apparatus frame, and a part electrically connected to the wire cable and a part electrically connected to the support member are separated. Equipped with a capacitance detection unit that detects the capacitance between the seed and the molten metal, it automatically detects contact between the seed and the molten metal, separation between the bottom part and the molten metal, and a relative surface position drop caused by a decrease in the molten metal. This provides the advantage of accurate detection. Therefore, using these detection results, the shape of the single crystal can be controlled accurately and automatically.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a characteristic diagram showing an example of a change in the output signal of the capacitance meter 32 shown in FIG. 1, and FIG. 3 is a crucible 2 FIG. 4 is a cross-sectional view showing the configuration of a conventional single crystal manufacturing apparatus. 2... Crucible, 3... Graphite susceptor (supporting member), 4... Shaft, 10... Upper casing (frame body), 13... Wire cable, 20... Seed holder, 21... Seed, 22... Single crystal silicon.

Claims (1)

[Claims] 1 A seed attached via a seed holder to the lower end of a wire cable suspended from the device frame, an insulating crucible in which polycrystalline molten metal is stored, and a conductive crucible that covers and supports this crucible. A support member is provided, and the wire cable is insulated from the device frame in a single crystal manufacturing device in which the seed is brought into contact with the molten metal and then pulled up, thereby growing a single crystal at the lower end of the seed. A single crystal manufacturing apparatus further comprising a capacitance detection unit that detects capacitance between a portion electrically connected to the wire cable and a portion electrically connected to the support member.