JPH04114992A - Method for controlling single crystal production device - Google Patents

Abstract

PURPOSE:To uniform oxygen concentration, stabilize quality and improve yield of a single crystal by controlling electric power amounts of a bottom heater and side heater so as to coincide temperature of a crucible side part with temperature of a crucible bottom. CONSTITUTION:An emitting light signal emitted from a side heater 4 for heating the side part of a crucible 3 is detected by the first temperature sensing member 26 provided opposite to through hole 4 opened in a heating chamber 2a and heat insulating cylinder 5 and the detected value is input to a temperature converter 27 to measure the temperature. On the one hand, the bottom of crucible 3 is heated with a bottom heater 22a and the temperature is detected with the second temperature sensing member 28 and input to a controller 30. Then signal from the converter 27 is operated in a operating device 29 and input to the controller 30. Electric powder amounts of the side heater 4 and bottom heater 22a are controlled so as to keep objective temperature of crucible bottom and temperature of crucible bottom measured by the sensing member 28 in a range previously set.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of controlling an apparatus for producing a single crystal by the Czochralski method (CZ method).

(Prior art) As a method for manufacturing single crystals of silicon, germanium, gallium arsenide, etc., the Czochralski method (Czochralski method) is used to grow and pull a single crystal from a raw material melt in a quartz crucible.
Z method) is widely practiced.

As a conventional manufacturing apparatus for carrying out this CZ method, for example, the one schematically shown in FIG. 4 is used.

This device 1 includes a heating chamber 2a and a pulling chamber 2b.
The heating chamber 2a includes a quartz crucible 3a and a graphite crucible 3 that protects it.
A crucible 3 composed of a crucible 3, a cylindrical side heater 4 surrounding the side of the crucible 3, and a heat insulating protection cylinder 5 erected on the outer periphery of the side heater 4 are provided.

The crucible 3 is connected to a drive device 6 located outside the chamber 2 via a rotating shaft 8 extending through the chamber bottom 7, and can be rotated and raised and lowered by operating the drive device 6. .

Note that the pulling chamber 2b is a portion where a silicon single crystal grown by immersing a seed crystal in the raw material melt in the crucible 3 is pulled.

The side heater 4 of this manufacturing apparatus 1 is generally made of carbon, and is heated by passing an electric current through it through the power supply connection part 9. This carbon heater heats the crucible. When silicon dioxide (Si02) is eluted, it reacts with oxygen and produces carbon dioxide (CO2).
2) is gradually consumed and the cross-sectional area becomes smaller. For this reason, the electrical resistance of the thinned portion increases compared to other portions, and the amount of heat generated in this portion increases, resulting in a high temperature.

Moreover, this heated part becomes more and more oxidized and becomes thinner.
There is a tendency for the amount of heat generated to increase.

As described above, when the heating temperature changes due to wear and tear of the side heater 4, the temperature state of the crucible 3 becomes non-uniform as a whole, with the sides of the crucible 3 being at a high temperature and the bottom being at a low temperature. As a result, there are problems such as a delay in dissolution during raw material melting, an unstable temperature state during pulling of the single crystal, and dislocations and diameter fluctuations in the crystal due to this, resulting in a decrease in yield.

For this reason, in order to make the heating temperature of the crucible 3 uniform, the crucible 3 has traditionally been rotated or moved up and down, but even with this method, it is difficult to maintain a uniform temperature throughout the crucible 3. there were.

Therefore, recently, there is a system in which the temperature of the side heater 4 is measured from the outside with a radiation thermometer 10 to control the position of the crucible 3 (Japanese Patent Laid-Open No. 63-107,888).
(see publication).

This control method involves installing radiation thermometers 10 at multiple locations at different heights of the side heater 4, and converting the radiation from the side heater 4 into temperature using these radiation thermometers 10. Detects the temperature distribution state of 3,
The position of the crucible is changed to obtain the most efficient heating condition.

In addition, as another method, a bottom heater 1 is provided at the bottom of the crucible 3 to actively heat the bottom of the crucible 3,
Alternatively, in addition to the heat insulation protection cylinder 5 provided on the side of the side heater 4, a bottom heat insulation member 12 is provided at the bottom of the crucible 3,
Some prevent the temperature from decreasing at the bottom of crucible 3 (
JP-A No. 5645.893, JP-A No. 61-186.
281, etc.).

(Problem to be Solved by the Invention) However, as in the former case, even if the radiation thermometer 10 detects the temperature distribution in the height direction of the crucible 3 and attempts to improve the heating efficiency of the crucible 3, the bottom of the crucible The temperature of the crucible is relatively lower than that of the sides, and the temperature is not uniform throughout the crucible, resulting in delayed melting of raw materials and instability of the temperature state during single crystal heating. Further, there is a problem in that crystal dislocations and diameter fluctuations occur due to this.

In the latter case, providing a bottom heater 11 or a bottom heat insulating member 12 at the bottom of the crucible 3 is certainly effective when melting the polycrystalline silicon raw material, but when pulling a single crystal, the crucible 3 The radiant heat from the heater 4 does not escape downward, resulting in excessive heating and an increase in the oxygen concentration of the single crystal. In other words, the bottom heater 1 and the bottom insulation member 12
By providing this, when the wall temperature of the crucible 3 increases, the amount of oxygen eluted from the quartz crucible 3a into the raw material melt increases, and the oxygen content in the single crystal to be pulled increases. The reality is that the situation is not necessarily favorable.

The present invention was made in view of the above-mentioned drawbacks and problems of the prior art, and it is an object of the present invention to maintain a uniform temperature throughout the crucible when producing a single crystal by the CZ method, so that the single crystal is It is an object of the present invention to provide a method for controlling a single crystal production apparatus that allows a single crystal to be produced without dislocations, with a low oxygen content, and of high quality.

(Means for Solving the Problems) A first invention for achieving the above object detects a crucible by using a first temperature sensing member provided opposite to a through hole formed in a heating chamber of a single crystal manufacturing apparatus. Measuring the temperature of a heating heater, measuring the temperature of the bottom of the crucible heated by the bottom heater with a second temperature sensing member, and determining the temperature of the side of the crucible corresponding to the temperature measured by the first temperature sensing member. , the control of the single crystal manufacturing apparatus, characterized in that the amount of electric power of the two and three heaters is controlled so that the temperature at the bottom of the crucible measured by the second temperature sensing section falls within a predetermined range. It's a method.

A second invention for achieving the above object is to control the temperature of a side heater that heats a crucible using a first temperature sensing member provided opposite to a through hole formed in a heating chamber of a single crystal manufacturing apparatus. At the same time, the temperature at the bottom of the crucible is measured by a second temperature sensing part, and the temperature at the side of the crucible corresponding to the temperature measured by the first temperature sensing part and the second temperature sensing part are A method for controlling a single crystal manufacturing apparatus, characterized in that the relative position of a heat insulating plate covering a lower area of the crucible and the crucible is adjusted so that the measured temperature at the bottom of the crucible falls within a predetermined range. It is.

Note that the appropriate set temperatures for the sides and bottom of the crucible vary depending on the device configuration and operating conditions. Therefore, it is necessary to determine the setting conditions appropriately in advance.

In this invention, it is preferable that the heat insulating plate covering the lower region of the crucible has an opening/closing structure that allows heat from the crucible to escape to the lower part.

(Function) In the invention configured as described above, the temperature of the crucible corresponding to the temperature of the heater measured by the first temperature sensing member and the temperature of the bottom of the crucible measured by the second temperature sensing member are determined in advance. We either controlled the power consumption of the side heater and bottom heater, or adjusted the relative positional relationship between the crucible and the heat insulating plate provided at the bottom of the crucible, so that the crucible remained within the specified range. The temperature inside becomes uniform throughout.

Therefore, if heat is prevented from escaping when melting raw materials,
It becomes possible to uniformly melt the raw material, there is no delay in dissolution, it is possible to prevent the formation of dislocations in the single crystal due to the instability of the temperature state during pulling of the single crystal, and the product yield is improved. Also,
When pulling a single crystal, if you prevent unnecessary heating of the crucible and make the temperature uniform throughout the crucible, you can suppress the increase in the amount of oxygen eluted from the quartz crucible throughout the crucible, and this will allow you to pull the single crystal. It is also possible to prevent oxygen from becoming too high and to make the oxygen concentration uniform throughout the single crystal.

(Example) Hereinafter, an example of the first invention will be described based on the drawings.

FIG. 1 is a cross-sectional explanatory diagram schematically showing an apparatus for carrying out the first method of the invention, and FIG. 2 is an explanatory diagram showing experimental results of the same method, and has the same function as the member shown in FIG. 4. The same reference numerals are given to the members, and some explanations thereof will be omitted.

A single crystal manufacturing apparatus 20 for carrying out the first invention method shown in FIG. 1 has a chamber 2 consisting of a large diameter heating chamber 2a and a small diameter pulling chamber 2b. A crucible 3 having a U-shaped cross section is provided in the heating chamber 2a, and the outer periphery of the quartz crucible 3a is covered and protected by a graphite crucible 3b. This crucible 3 is connected to a rotating shaft 8, and is moved up and down and rotated by a drive device 6. A side heater 4 is provided around the crucible 3 for melting the raw material contained in the quartz crucible 3a, and this side heater 4 uses various methods such as a resistance heating method or an induction heating method. However, when applied to a large continuous pulling device, it is preferable to use a resistance heater in consideration of economic efficiency.

The outer periphery of this side heater 4 is covered with a heat insulating tube 5 erected on a support base 21.

On the other hand, a bottom heater 22a is provided at the bottom of the crucible 3 to prevent at least heat dissipation from the crucible 3 to the bottom.
is provided. The height position of the bottom heater 22a relative to the crucible 3 can be adjusted so that the bottom temperature of the crucible 3 can be finely adjusted. That is, the operating rod 23 is attached to the bottom surface of the bottom heater 22a, and the operating rod 23 is attached to the bottom surface of the bottom heater 22a.
3 is raised and lowered by a drive member 24 such as a motor.

In particular, in this embodiment, a first temperature sensing member 26 such as a radiation thermometer is provided opposite to the through hole 25 opened in the heating chamber 2a and the heat insulating cylinder 5, and this first temperature sensing member 26 allows the side heater 4 to be A synchrotron radiation signal emitted from the sensor is detected, and this signal is input to a temperature converter 27 and converted into temperature. On the other hand, a second temperature sensing member 28 such as a thermocouple is provided at the bottom of the crucible 3.
Measuring the temperature at the bottom. The signal from the temperature converter 27 is sent to the computing unit 2 so as to correspond to the temperature of the side of the crucible 3.
9 and input to the controller 3o. On the other hand, the temperature at the bottom of the crucible detected by the second temperature sensing member 28 is also input to the controller 30 . In this case, as a signal input method, it is preferable to use a slip ring S for the thermocouple, or a transmitter may be attached to the bottom of the crucible 3 to perform the signal input wirelessly.

The controller 30 controls the power consumption of the side heater 4 and the bottom heater 22a so that the crucible bottom target temperature instructed by the calculator 29 and the temperature of the crucible bottom measured by the second temperature sensing member 28 fall within a predetermined range. is designed to be controlled.

However, the lower position may be adjusted by operating not only the electric power of both heaters 4 and 22a, but also the drive member 24 for the bottom heater 22a and the drive device 6 for the crucible 3.

By controlling the bottom temperature of the crucible 3 to an appropriate temperature using the signal from the controller 30 in this way, the temperature distribution throughout the crucible 3 from melting of the raw material to pulling out of the single crystal becomes uniform, thereby reducing the single crystallization rate. You can improve your performance.

First, a predetermined amount of polycrystalline silicon and a dopant to be added thereto as needed are supplied from a raw material supply device to a quartz crucible 3.
a, and when melting by operating the side heater 4 and bottom heater 22a, the bottom heater 22a:
It is raised by an external drive member 24 and brought close to the crucible 3.

The heat from both heaters 4 and 22a is radiated from around the crucible 3, but since the heating effect is performed while controlling the amount of electricity, the crucible 3 is heated almost uniformly throughout, and the raw materials are evenly melted. - to be carried out. Therefore, there will be no delay in dissolving some of the raw materials.

When the raw material melt 31 is formed, a seed crystal is immersed in the raw material melt 31, a single crystal is grown at the lower end of the seed crystal, and the crucible 3
Then, the pulling operation is started while rotating the seed crystal relative to each other. In the initial stage of single crystal pulling, the diameter of the single crystal is narrowed by setting a high pulling rate and/or increasing the raw material melt temperature, and dislocations are driven out to the single crystal surface to eliminate dislocations. do. Subsequently, by lowering the pulling rate and/or the temperature of the raw material melt, a single crystal having a desired diameter is grown. In this case as well, it is preferable to rotate the crucible 3 using the drive device 6 to stir the raw material melt 31 and equalize the temperature.

During this pulling, argon gas is blown into the heating chamber 2a and the heating chamber 2a is made into a reduced pressure argon atmosphere or a normal pressure argon atmosphere. In addition, the bottom heater 22a is lowered by a predetermined amount by operating the drive member 24, and the amount of electric power is lowered as necessary.
prevent it from being heated unnecessarily. In this way, the amount of oxygen eluted from the quartz crucible 3a is suppressed, and as a result, a secondary effect of preventing the single crystal from becoming highly oxygenated also occurs.

In addition, the evaporated matter from the upper surface of the raw material melt is sent out and discharged from the system by the argon gas blown during pulling.
High carbonization, high oxygen content, dislocations, and polycrystalization of the single crystal caused by evaporated substances are prevented.

FIG. 2 is an explanatory diagram showing the experimental results, and shows the amount of electric power applied to the side heater 4 and the bottom heater 22a when forming a melt from raw materials, and the amount of power detected by the first temperature sensing member 26 and the second temperature sensing member 28. This shows the relationship with temperature.

In this experiment, side heater 4 and bottom heater 2
The total amount of electric power added to 2a is approximately 70Kw.

As is clear from this figure, heating according to the method of the present invention (indicated by the solid line in the figure) can be performed, for example, when the number of charges of the raw material is 0 to 30.
In the range of 50Kw, the amount of power applied to the side heater 4
If the amount of electric power applied to the bottom heater 22a is 20Kw, the temperature of the side heater 22a is 1550°C,
The temperature at the bottom of crucible 3 was 1460°C. If the temperature of the side heater 22a is converted to the temperature of the side of the crucible 3, it is approximately 1460° C., which indicates that the entire crucible is in a uniform temperature state.

Next, when the number of charges is in the range of 30 to 50, the amount of power applied to the side heater 4 is set to 48KW, and the amount of power applied to the side heater 4 is set to 48KW.
The amount of electric power added to a was set to 22Kw. In this case, the temperature of the side heater 4 and the temperature of the bottom of the crucible 3 were the same as in the case where the number of charges was in the range of 1 to 30.

When the number of charges was in the range of 50 to 70, the same results as in the previous case were obtained when the amount of power applied to the side heater 4 was set to 46 Kw and the amount of power applied to the bottom heater 22a was set to 25 Kw.

On the other hand, in Comparative Example 1 (indicated by the broken line in the figure), when heating was performed with the amount of power applied to the side heater constant at 70Kw, the heater was locally worn out due to the reaction with SiO, and as a result, the side heater The temperature of 1550℃ to 15
The temperature rose to 70°C.

Furthermore, in Comparative Example 2 (indicated by the dotted chain line in the figure), the power amount of the side heater was lowered according to the number of charges so that the temperature of the side heater was constant.

As a result, the temperature at the bottom of the crucible decreased. the result,
In both Comparative Examples 1 and 2, the temperature at the bottom of the crucible decreased after about 50 charges, temperature instability occurred, and the yield of single crystals decreased.

As is clear from this point, in this embodiment, regardless of the number of charges, the temperatures at the sides and bottom of the crucible are determined in advance from the measured values of the first temperature sensing member 26 and the second temperature sensing member 28. It can be seen that since the amount of power applied to the side heaters 4 and bottom heaters 2.2a is controlled so as to maintain the range, the crucible 3 can be heated uniformly over the entire crucible 3, and stable pulling work can be performed.

Moreover, in Comparative Examples 1 and 2, when the charge exceeds about 50, the single crystal yield drops significantly due to local thinning of the heater, so the heater had to be replaced with a new one. In this example, no particular problem occurred even when the heater was used up to about 70 charges. That is, according to the present invention, it can be said that the life of the heater is extended and the manufacturing cost of the single crystal is reduced.

Although the apparatus for carrying out the second method of the invention is not particularly shown in the drawings, it will be described with reference to FIG. 2b. It is preferable to use a board material formed by stacking graphite sheets as the heat insulating board 22b.

Since this heat insulating plate 22b only prevents the heat radiated from the crucible 3 or the heater 4 from escaping downward, in order to control the temperature of the crucible 3, the position of the heat insulating plate 22b relative to the crucible 3 must be adjusted. Do it by doing this. In other words, similarly to the previous invention, this heat insulating plate 22b is also provided with an operating rod 23 on the lower surface, and this operating rod 23 is connected to a drive member such as a motor.
to raise and lower it.

In this way, the heat radiated from the crucible 3 or the heater 4 is blocked by the heat insulating plate 22b and does not escape downward, and when the heat insulating plate 22b is raised and lowered by the driving member 24, the crucible 3 as a whole becomes approximately even. -It will be heated to -.

Therefore, there will be no delay in dissolving some of the raw materials.

However, when heating the entire crucible uniformly, it is more preferable that the heat insulating plate 22b not only simply move up and down, but also allow the radiant heat from the crucible 3 and the like to escape downward. Therefore, the heat insulating board 2 in this second invention
As a specific example of 2b, it is preferable to configure it with an opening/closing mechanism, as shown in FIGS. 3A, B, and C, for example.

By opening these heat insulating plates 22b, the radiant heat from the crucible 3 and the like can be released to the lower part, and the internal temperature of the crucible 3 can be controlled more precisely.

The heat insulating plate 22b shown in FIG. 3(A) is constructed by dividing a disc-shaped graphite movable heat insulating plate 40a into six pieces, and connecting each piece to a drive unit side 42 such as a motor through a shaft 41. By connecting the pieces and driving the drive member 42, each piece is rotated about a shaft 41. However, instead of providing a plurality of drive members 42, one drive member 42 can be used to drive the plurality of shafts 4.
1 may be operated simultaneously.

The one shown in FIG. 3(B) has a shaft 41 connected to a disk-shaped movable heat shield plate 40b made of graphite divided into two parts, and is rotated by a driving member 42 such as a motor. .

The one shown in FIG. 3(C) has a pair of upper and lower movable heat shield plates 40c and 40d with radial pieces 45 projecting radially outward from the boss portion 43 through a predetermined space 44. , for example, the lower movable heat shield plate 40d is rotated via the link 46 etc., and both movable heat shield plates 40c are rotated.
, 40d, the heat radiated from the crucible 3 etc. is controlled by the overlapping state of the radial pieces 45 of 40d.

Note that the invention is not limited to the described embodiments, and can be modified in various ways.

For example, the first temperature sensing member 26 uses a radiation thermometer and the second temperature sensing member 28 uses a thermocouple. Member 28 may be a radiation thermometer, or both may be thermocouples or radiation thermometers.

In the above embodiment, the height position of the crucible 3 is fixed,
This crucible 3 is used to raise and lower the heat insulating plate 22b.
It goes without saying that the positional relationship between the heat insulating plate 22b and the heat insulating plate 22b is relative, and either one may be raised or lowered.

(Effects of the Invention) As described above, in the first invention, when producing a single crystal by the CZ method, the temperature at the side of the crucible measured by the first temperature sensing member and the temperature at the crucible side measured by the second temperature sensing member are The electric power of the bottom heater and the side heater is controlled so that the temperature at the bottom matches the temperature at the bottom, and in the second invention, the relative position of the heat insulating plate to the crucible is controlled, so both of these are controlled within the crucible. The temperature becomes uniform throughout, preventing delays in dissolution of raw materials and unnecessary heating of the quartz crucible, preventing the rotation of the single crystal, preventing high oxygen content, and making the oxygen concentration uniform throughout the single crystal. It is possible to grow stable single crystals of good quality and improve the yield of single crystal manufacturing.In addition, the series of operations from melting raw materials to pulling single crystals is performed under temperature control. , it is possible to improve the single crystallization rate.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view schematically showing an apparatus for carrying out the first method of the invention, FIG. 2 is an explanatory view showing experimental results of the example shown in FIG. 1, and FIGS. 3A and 3B. C is a perspective view showing a modification of the heat insulating plate, and FIG. 4 is a schematic sectional view showing a conventional device. 2.2a, 2b... Heating chamber, 3.3a, 3b... Crucible, 4... Side heater, 5... Heat insulation protection cylinder, 6...
...Drive device, 22a...Bottom heater, 22
b...Insulation board 25...Through hole, 26...First
Temperature sensing member, 28... second temperature sensing member.

Claims (1)

[Scope of Claims] 1) The side of the crucible (3) is controlled by the first temperature sensing member (26) provided opposite to the through hole (25) opened in the heating chamber (2a) of the single crystal manufacturing apparatus. The second temperature sensing member (28) measures the temperature of the bottom of the crucible (3) heated by the bottom heater (22a), and the first temperature sensing member (28) measures the temperature of the side heater (4) that heats the crucible (3).
Both heaters (4, 22a ) A method for controlling a single crystal manufacturing apparatus, characterized in that the amount of electric power is controlled. 2) A side heater (
4), and also measure the temperature at the bottom of the crucible (3) by a second temperature sensing member (28), and measure the temperature at the bottom of the crucible (3) corresponding to the temperature measured by the first temperature sensing member (26). temperature of the second temperature sensing member (28
) a heat insulating plate (22b) covering the lower area of the crucible (3) so that the temperature at the bottom of the crucible measured by
A method for controlling a single crystal manufacturing apparatus, characterized in that the relative positions of the crucible (3) and the crucible (3) are adjusted. 3) The method of controlling a single crystal manufacturing apparatus according to claim 2, wherein the heat insulating plate has an opening/closing structure that releases heat from the crucible (3) to a lower part.