JP2003055084A - Device and method for pulling single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single crystal pulling device equipped with a temperature sensor capable of stably and accurately measuring the temperature of the surface of a melt while suppressing the effects of radiation heat from a single crystal and the wall of a crucible and to provide a single crystal pulling method by which the distance between a radiation screen and the surface of the melt is always controlled to be a constant value. SOLUTION: The single crystal pulling device is equipped with the temperature sensor which has a constitution that a graphite chip for receiving radiation heat from the surface of the melt in a crucible is provided and a thermo couple is brought into contact with the graphite chip, which is covered with a heat insulating material except its heat receiving face, through a nonmetal protection tube. The single crystal pulling method comprises measuring the temperature of the surface of the melt in the crucible and controlling the surface level of the melt according to the measurement results so as to keep the distance from the surface of the melt to the lower end part of the radiation screen constant.

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 technique, and more particularly to a single crystal pulling apparatus and a single crystal pulling method for producing a single crystal having uniform crystal quality.

[0002]

2. Description of the Related Art There are various methods for growing a single crystal, and one of them is a Czochralski method (hereinafter referred to as CZ method) for growing a single crystal. Figure 4 shows CZ
FIG. 1 is a cross-sectional view schematically showing a single crystal pulling apparatus used in the method, in which 1 denotes a crucible.

This crucible 1 is composed of a quartz crucible with a bottomed cylindrical shape and a graphite crucible with a bottomed cylindrical shape that is fitted on the outside of this quartz crucible, and the crucible 1 has a predetermined shape. It is supported by a support shaft 2 which rotates and moves up and down at a speed of. A resistance heating type heater 3 is arranged outside the crucible 1, and the crucible 1 is filled with a melt 4 of a raw material for crystallization melted by the heater 3. A pulling shaft 5 made of a pulling rod or a wire is hung on the central axis of the crucible 1, and a seed crystal (not shown) is attached to the tip of the pulling shaft 5 via a holder 6. Has become. Reference numeral 8 in the drawing denotes a radiation screen, which is provided so as to surround the outer periphery of the single crystal 7 being grown so that an appropriate temperature gradient is given to the single crystal 7 in the pulling axis direction. Further, these members are housed in a water-cooled chamber whose pressure can be controlled.

A method for pulling the single crystal 7 using the above-mentioned single crystal pulling apparatus will be described. First, after decompressing the inside of the chamber, an inert gas is introduced to create a decompressed inert gas atmosphere in the chamber, and then the raw material for crystal is melted by the heater 3. Next, while rotating the pulling shaft 5 in the opposite direction at the same axis as the supporting shaft 2 at a predetermined speed, the seed crystal attached to the holder 6 is lowered to be deposited on the melt 4 to form a seed crystal. After accommodating the melt 3, the single crystal 7 is grown on the lower end of the seed crystal.

After that, after the steps of predetermined seed drawing, shoulder portion formation, straight body portion formation, and tail drawing, the single crystal 7 is separated from the melt 4 and cooled under predetermined conditions.
The wafer processed and manufactured from the single crystal 7 thus obtained is used as a substrate material for various semiconductor devices.

[0006]

By the way, in carrying out the above-mentioned single crystal pulling, the fluctuation of the melt temperature during the growth of the single crystal directly affects the crystal growth rate at the solid-liquid interface, and the diameter of the single crystal grown is increased. Therefore, it is necessary to accurately measure the melt temperature in the crucible and control the melt temperature at a constant temperature during the growth of the single crystal because the fluctuation of the above causes a decrease in product yield.

As a method for measuring the melt temperature, for example, in Japanese Patent Laid-Open No. 137088/1993, the temperature of the melt is directly measured by immersing the thermocouple in the melt near the solid-liquid interface and controlling the melt temperature. How to do is presented. In this case, since the thermocouple is directly immersed in the melt, there is a possibility that the thermocouple may be dissolved and impurities in the melt may be contaminated, and only intermittent measurement can be performed in order to prevent the thermocouple from being dissolved. Also,
There is also a problem with the life of thermocouples.

Further, in Japanese Unexamined Patent Publication No. 5-132391, in order to estimate the shape of the solid-liquid interface of a single crystal, thermocouples are placed and measured near the side surface of the single crystal at three different heights from the melt surface. , A method for controlling the temperature environment is presented. In this case, in addition to the ambient temperature at the tip of the thermocouple, it is presumed that radiant heat from the single crystal and the crucible wall is affected, and it is presumed that sufficient information on the melt temperature cannot be obtained.

As described above, although it is necessary to accurately control the melt temperature in growing a single crystal, the melt temperature measuring means provided so far does not generate impurity contamination in the melt. However, since the melt temperature cannot be measured accurately, there is a problem that a high quality single crystal cannot be grown with high accuracy.

On the other hand, as the single crystal is grown, the melt in the crucible decreases and the melt surface position lowers. Therefore, the crucible is raised to correct this and the melt surface position is always kept at a fixed position. Controls are in place. In particular, in recent years, in pulling a single crystal using a radiation screen, which is indispensable for growing a single crystal, when the melt surface position control is not properly performed, the melt surface and the lower end of the radiation screen are Interval (below,
There is a problem that the crystal quality varies in the pulling longitudinal direction of the single crystal, because the "gap") changes and the thermal history received by the growing single crystal greatly changes.

Therefore, in order to keep the gap position distance constant, it is necessary to accurately measure the melt surface position in the crucible. However, the melt surface position that has been adopted so far is
Since it is an optical measuring means using a two-dimensional CCD camera or the like, it is not possible to accurately measure the melt surface position due to the influence of waviness and stray light on the melt surface.

The present invention has been made in view of the above problems,
Provide a single crystal pulling device equipped with a temperature sensor that can measure the melt surface temperature stably and accurately by minimizing the effect of radiant heat from the single crystal and the crucible wall, and keep the gap position interval constant. An object is to provide a controllable single crystal pulling method.

[0013]

A single crystal pulling apparatus according to claim 1 of the present invention is provided with a graphite piece for receiving radiant heat from the surface of a melt in a crucible, and a graphite piece other than the heat receiving surface is covered with a heat insulating material. It is characterized in that a temperature sensor constituted by contacting a thermocouple with a graphite piece through a non-metal protective tube is provided.

A single crystal pulling apparatus according to a second aspect of the present invention is provided with a radiation screen surrounding the single crystal being grown, and the temperature sensor is attached to a lower end portion of the radiation screen. It is what

In the method for pulling a single crystal according to claim 3 of the present invention, when pulling a single crystal by using a single crystal pulling apparatus in which a radiation screen is arranged so as to surround the circumference of the growing single crystal, a crucible is used. Measuring the temperature of the melt surface in, based on the measurement result, characterized by controlling the melt surface position so that the distance from the preset melt surface to the lower end of the radiation screen is maintained constant To do.

The method for pulling a single crystal according to claim 4 of the present invention is a method for pulling a single crystal using a single crystal pulling apparatus in which a radiation screen is arranged so as to surround the circumference of the growing single crystal. Equipped with a graphite piece that receives radiant heat from the melt surface in the crucible, the graphite piece covered with a heat insulating material except the heat receiving surface, a temperature sensor configured by contacting a thermocouple through a non-metallic protective tube To measure the temperature of the melt surface in the crucible using, based on the measurement results, to control the melt surface position so that the distance from the preset melt surface to the lower end of the radiation screen is maintained constant It is characterized by.

The temperature sensor employed in the apparatus for pulling a single crystal according to claim 1 of the present invention is basically one in which graphite is heated by radiant heat from the surface of the melt and the temperature is detected by a thermocouple. is there. Graphite has excellent absorption of radiant heat, good heat conduction, and low specific heat, so by covering the radiant heat from the single crystal or crucible wall by covering the part other than the heat receiving surface of the graphite piece with a heat insulating material, the melt can be accurately melted. Radiant heat from the surface can be detected.

According to the single crystal pulling apparatus according to the second aspect of the present invention, by adopting a simple structure in which the temperature sensor is provided at the lower end portion of the radiation screen, a large-scale apparatus is not required. The surface temperature of the melt directly below the lower end of the radiation screen, which is near the growth interface of the single crystal, can be accurately measured.

According to the method for pulling a single crystal according to the third aspect of the present invention, the gap position can always be controlled to a constant position. If this point is described in detail, during single crystal growth, the melt surface temperature also changes when there is a change in the melt surface position, so the correlation between the melt surface temperature and the gap position is obtained in advance, The actual gap position can be calculated by measuring the melt surface temperature during actual growth and comparing it with the above correlation. Then, the gap position can be constantly controlled to a constant position by raising and lowering the crucible so as to correct the difference between the calculated gap value and the preset gap setting value.

According to the single crystal pulling method of the fourth aspect of the present invention, since the melt surface temperature during the growth can be calculated with higher accuracy, the accuracy of gap position control is further improved.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a single crystal pulling apparatus and a single crystal pulling method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a single crystal pulling apparatus according to the present invention. The conventional single crystal pulling apparatus described in FIG. 4 except that a temperature sensor 9 is attached to the lower end of a radiation screen 9. The device configuration and the same reference numerals are the same as those of the device, and the description of the reference symbols of each member is omitted.

FIG. 2 is a sectional view schematically showing a temperature sensor 9 used in the single crystal pulling apparatus according to the present invention. The heat receiving surface 1 of the graphite piece 10 facing the surface of the melt in the crucible 1
4 and the thermocouple 12 is brought into contact with the opposite side through the protective tube 13 so that the graphite piece 10 is surrounded by the heat insulating material 11 so as not to receive heat radiation directly from the surface other than the heat receiving surface 14. The structure will be covered.

The graphite pieces 10 are made of high-density and high-purity graphite,
The shape of the heat receiving surface 14 may be square or circular, and its shape is not particularly limited. The area of the heat receiving surface 14 is 19 to 23.
It may be about 5 mmφ, which is about 0 mm2, to about 15 mm square, and its thickness may be about 3 to 12 mm.

As the thermocouple 12, types such as JIS-C1602 B, R, and S which can withstand use at 1400 ° C. or higher are used. The thickness may be a usual diameter of 0.5 mm, and a finer diameter is preferable because it has little influence on heating of graphite.
The protective tube 13 and the insulating tube (not shown) may be made of quartz glass, but it is desirable to use a non-metallic porcelain having a resistance to use at 1400 ° C. or higher as shown in JIS-R1401 or R1402. The heat insulating material 11 may be made of graphite cloth, carbon felt, ceramic fiber, or the like that does not cause contamination, and it is preferable that the thin portion has a thickness of 2 mm or more. Further, from the viewpoint of preventing contamination due to desorption of impurities from the heat insulating material 11, it is desirable to cover the outer surface of the heat insulating material with a graphite material and further coat a SiC film thereon. The temperature sensor 9 is preferably installed so that the distance from the heat receiving surface 14 to the melt surface 3 is 3 mm to 10 mm.

In carrying out the actual pulling of the silicon single crystal using the single crystal pulling apparatus shown in FIG. 1, first, the silicon melt 4 is filled in advance before the actual pulling of the single crystal. The crucible 1 was moved up and down to perform various experiments of changing the gap position intervals by changing the melt surface position, and the melt surface temperature at each gap position was measured using the temperature sensor shown in FIG. A correlation table for determining the relationship between the interval and the melt surface temperature is prepared. This correlation table is input and managed by a CPU (not shown).

FIG. 2 is a graph showing the correlation between the gap position distance and the melt surface temperature when the single crystal pulling apparatus shown in FIG. 1 is used. As you can see from this figure,
The wider the gap position interval, the lower the melt temperature. According to the experiments conducted by the present inventors, the result was that the melt surface temperature was changed by 4,5 ° C. simply by shifting the gap position distance by 2 mm.

Next, in the actual silicon single crystal pulling process, the temperature of the melt surface is constantly measured by using the temperature sensor 9. The measurement result is input to the CPU, and the above-described gap position interval and the correlation table of the melt surface temperature are compared and calculated to calculate the current accurate gap position interval. Next, the CPU calculates a comparison between the calculated current gap position interval and a preset predetermined gap position interval. As a result, if there is a difference in the gap position interval, the CPU will correct the gap position interval. A control signal is transmitted to a crucible lifting device (not shown) to move the crucible 1 up and down, and the melt surface position is adjusted. Thereby, the single crystal can be always pulled under the condition that the gap position distance is constant, and the diameter deviation is small, and the single crystal with uniform crystal quality can be manufactured.

[0029]

As described above, by using the single crystal pulling apparatus of the present invention, the melt surface temperature in the crucible can be accurately measured without causing contamination of the melt. The melt temperature can always be kept constant.
Further, by adopting the single crystal pulling method of the present invention, even if the melt surface position fluctuates, it can be instantly corrected and the single crystal can be always pulled in a state where the gap position interval is constant. This reduces the diameter deviation,
It is possible to manufacture a single crystal having uniform crystal quality in the pulling longitudinal direction.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a single crystal pulling apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a temperature sensor used in the single crystal pulling apparatus according to the embodiment of the present invention.

FIG. 3 is a graph showing the correlation between the gap position distance and the melt surface temperature when the single crystal pulling apparatus of the present invention is used.

FIG. 4 is a sectional view schematically showing a conventional single crystal pulling apparatus.

[Explanation of symbols]

1 crucible 2 crucible lifting shaft 3 heater 4 Molten liquid 5 Lifting shaft 6 seed crystals 7 Single crystal 8 Radiation screen 9 Temperature sensor 10 Graphite pieces 11 Insulation 12 thermocouple 13 Protection tube 14 Heat receiving surface

Claims (4)

[Claims] 1. A structure in which a graphite piece for receiving radiant heat from the surface of a melt in a crucible is provided, and the graphite piece covered with a heat insulating material except for the heat receiving surface is contacted with a thermocouple via a non-metal protective tube. A single crystal pulling apparatus, which is equipped with a temperature sensor. 2. A radiation screen surrounding the single crystal being grown is provided, and the temperature sensor is attached to a lower end portion of the radiation screen.
The single crystal pulling apparatus described. 3. A method for pulling a single crystal by using a single crystal pulling apparatus in which a radiation screen is arranged so as to surround the circumference of the growing single crystal, and measuring the temperature of the melt surface in the crucible, A method for pulling a single crystal, characterized in that the position of the melt surface is controlled so that a preset distance from the melt surface to the lower end of the radiation screen is kept constant based on the measurement result. 4. A method for pulling a single crystal by using a single crystal pulling apparatus in which a radiation screen is arranged so as to surround the single crystal being grown, and the radiant heat from the melt surface in the crucible is received. The temperature of the melt surface in the crucible is measured using a temperature sensor that is equipped with a graphite piece, and the graphite piece covered with a heat insulating material except the heat receiving surface is contacted with a thermocouple through a non-metallic protective tube. Then, based on the measurement results, the melt surface position is controlled so that the preset distance from the melt surface to the lower end of the radiation screen is maintained constant, and a single crystal pulling method is characterized.