JPS59227797A - Method for pulling up single crystal - Google Patents

Abstract

PURPOSE:To facilitate the seeding operation and control of the diameter of a single crystal and pull up the single crystal while estimating the temperature gradient in the crystal, by specifying the fixing position of a thermocouple for measuring the temperature for controlling the power of a heater in the Czochralski method. CONSTITUTION:A thermocouple 9 is provided below the side of a seed crystal 4 at a position for wrapping the tip thereof in the head of a single crystal 5 to be grown. The thermocouple 9 is attached to a pulling up shaft 10 to be rotated, and lead wires are led to the outside by a slip ring on the shaft 10 and are made rotatable with the single crystal 5. The seed crystal 4 and the thermocouple 9 together are dipped in a raw material melt 3. At this time, the temperature of the thermocouple 9 is adjusted to be close to the melting point for seeding the single crystal 5. The seeding temperature can be measured directly with the thermocouple 9, and the operation is easily carried out without failure in seeding. The crystal 4 is then pulled up while reducing the temperature of the raw material melt 3 measured by the thermocouple 9 to grow the single crystal 5 to wrap the crystal 4. The power 8 of a heater 2 is controlled on the basis of the temperature measured by the thermocouple 9 during that time. In the process, the average temperature gradient in the crystal 4 can be directly estimated.

Description

Detailed Description of the Invention (Technical Field) The present invention is based on the Czoch/L/7-key method (hereinafter referred to as CZ method) or the liquid capsule Czochralski method (hereinafter referred to as L
Regarding the method of pulling single crystals by the EC method (referred to as the EC method),
In particular, it relates to a method of controlling the temperature inside the furnace.

(Background Art) In the CZ method, as shown in FIG. 1, a raw material melt 3 is placed in a crucible 1 heated by an in-furnace heater 2, and if necessary, the surface is covered with an 8203 melt (LEC
method), the seed crystal 4 is immersed in the surface of the melt 3, and after being blended, the seed crystal 4 is pulled up and the single crystal 5 is pulled out. In this case, conventionally, the diameter of the single crystal (hereinafter referred to as diameter) has been controlled by using the temperature measured at the side 6 of the heater or at the bottom 7 of the crucible, and by controlling the power 8 of the heater 2.

For example, check the change in the diameter of the single crystal 5 visually through the peephole or by the change in the weight of the single crystal 5, and if the diameter is getting thicker, increase the temperature setting a little, and the heater 2
The power of 8' increased by 2, the temperature of the raw material melt near the solid-liquid interface rose, and the crystals stopped growing. Also, when the diameter was getting smaller, I did the opposite operation as described above. These controls were performed by computer or manually.

However, in this method, the thermometer (e.g., thermocouple) is placed on the side of the heater 6 or on the crucible bottom 7, which is carved far from the single crystal 5 or near the solid-liquid interface. Since it takes time for the diameter to change, it is not suitable for controlling the diameter.

Furthermore, in order to reduce dislocations in a single crystal, it is necessary to raise the temperature in the vertical direction with a low temperature gradient, but it was not possible to know the temperature gradient in the crystal during pulling.

(Disclosure of the invention) The present invention has been made to solve the above-mentioned problems.
When pulling a single crystal, seeding makes it possible to detect the temperature, the temperature of the single crystal, and the temperature near the solid-liquid interface, making it easier to control the diameter of the single crystal and estimating the temperature gradient in the crystal. The purpose of this study is to provide a method for pulling single crystals.

The present invention is a method for pulling a single crystal using the Czochralski method, in which a thermocouple is provided below the side of the seed crystal at a position that will become the head of the single crystal to be grown, and the thermocouple is used to pull a single crystal using the This is a single crystal pulling method characterized by controlling an in-furnace heater.

The single crystal to which the method of the present invention is applied is Ill of the periodic table.
-V group compounds, II -IV group compounds or their crystals, semiconductors such as Si and Ge, oxides, nitrides, carbides, etc., are single crystals made by CZ method or LEC method. .

Hereinafter, the present invention will be described by iD! Examples using drawings. ! I will clarify.

FIG. 2 is a longitudinal sectional view showing an example of a single crystal pulling apparatus used in an embodiment of the method of the present invention. In the figure, the same reference numerals as in FIG. 1 indicate the same parts. In Figure 2,
The difference from FIG. 1 is that a VC thermocouple 9 is provided below the side of the seed crystal 4. The thermocouple 9 is located at a position where its tip is surrounded by the head of the single crystal 5 to be grown, as shown in FIG.
A position 10 to 15 mm below is appropriate. The thermocouple 9 is attached to the rotating pull-up lllll1110, and the thermocouple 9
The single crystal 5
At the same time, oral transmission became possible.

FIG. 3 is a schematic diagram showing the state in which a single crystal is pulled using two sets of devices in the order of steps, in which (a) shows the time of seeding, and (b) shows the state during pulling of a single crystal. First, to carry out seeding, a seed crystal 4 is attached to the thermocouple 9 along the material fusion line. At this time, the temperature of the thermocouple 9 is adjusted to be near the melting point of the raw material. At this time, seeding.

Since the temperature can be directly measured with the thermocouple 9, seeding failures can be avoided and the work is easy.

Next, when the seed crystal 4 is pulled up while lowering the temperature in the melt using the thermocouple 9, the single crystal 5 grows so as to enclose the thermocouple 9, as shown in FIG.

In this case, the storage tube for the thermocouple 9 is selected from a material that does not get wet with the melt 4.

During single crystal growth, the power 8 of the heater 2 is controlled based on the temperature measured by the thermocouple 9 to adjust the temperature inside the furnace. The thermocouple 9 not only directly measures the temperature at the head of the single crystal 5, but also allows the average temperature gradient in the crystal to be immediately estimated from this temperature. That is, as shown in FIG. 4, the temperature measured by the thermocouple 9 is T, the temperature of the solid-liquid interface is TM (melting point),
If the tip of the thermocouple 9 and the sector 11 of the solid-liquid interface are 4, then fi
From Equation 1, the ``Y uniform vorticity gradient k in the vertical direction in the crystal is determined. Furthermore, by using computer simulation, the temperature distribution within the crystal can be determined in real time by giving T and the crystal shape. As described above, according to the method of the present invention, the temperature gradient near the solid-liquid interface can be detected by estimation. thermocouple 9
By controlling the power 8 of the heater 2 according to changes in the measured temperature, it is possible to control the temperature gradient within the crystal and, by extension, the heat escaping through the crystal, making it possible to control the crystal grains easily and quickly.

(Example 1) Using the apparatus shown in Fig. 2, a 50 mmφ GaA
s Semiconductor single crystal was pulled.

PBN (pyrolytic boron nitride) as crucible 1
GaAs polycrystal [kg] and N2O3 were charged and melted.The height of the GaAs melt was about 30 mm, and the thickness of the B2O3 melt was 20 mm.Thermocouple 9 0.5 mmφ thermocouple (W・
5% Re-W/26% Re) was used to protect the PBN protection tube 11, and it was attached to the pulling shaft 10 so as to have the dimensions shown in FIG. 4 is a seed crystal.

First, as shown in Fig. 6, lower the puller 1iill 110 and attach the tip of the thermocouple 9 to the fuse 3 to measure the liquid temperature.
A seed crystal 4 was attached to the melt 3 at 235°C. 12 is B2O
3 melt.

Next, the power of the in-furnace heater 2 was controlled using a thermocouple 9 next to the seed crystal to control the crystal diameter. As a result, when the diameter variation was controlled by humans, the diameter variation of the single crystal 5 was 50 mm±1.5 mm at the straight body portion. 50 when using automatic diameter control based on crystal weight using a computer for control.
It was mm±0.5 mm.

(Example 2) F) 50 mmφ GaAs was produced by the method of the present invention using a single crystal pulling apparatus with a two-stage heater structure as shown in FIG.
Pulled semiconductor single crystal.

In the figure, the same reference numerals as in FIG. 2 indicate the same parts. In No. 71-1, the heater was placed near the solid-liquid interface.
The heater was divided into a lower heater 13 and a lower heater 14, and the power applied to them was controlled separately.

After seeding in the same manner as in Example], when pulling out the single crystal, the temperature measured with thermocouple 9 is T1 (°C), and so that While adjusting the individual powers 15 and 16 of the crucible, the overall power amount was controlled by the thermocouple 17 at the bottom of the crucible to perform pulling.

Normally, when lifting with such a device, the upper heater
The temperature of the upper heater 13 is raised to a constant value, but if the temperature of the upper heater 13 is raised in an attempt to create a low temperature gradient in order to lower the dislocation density, crystal melting may occur, diameter control is difficult, and heat flow is increased. is not stable, so even if a low temperature gradient was used, the dislocation density of the crystal did not decrease much in the end.

However, in the method of the present invention, by setting 5γσ in equation (3), the variation in crystal diameter becomes 51 ± 2 mm, and the dislocation density is reduced to 5XIO on average at the front part of the single crystal.
"7m, 7X]03/ffl at the back part. In the conventional method, the dislocation density is generally 2 x 10'/i at the front part, and 6x104 at the back part.
/C-rI.

(Effects of the Invention) The single crystal growth method of the present invention configured as described above has the following effects.

(b) A thermocouple is installed below the side of the seed crystal at the position that will become the head of the single crystal to be grown, and the furnace heater is controlled according to the temperature measured by the thermocouple. Since the melt temperature at the location can be directly controlled, the seeding conditions can be easily adjusted, so there is no seeding failure and the work is easy.

(b) Furthermore, since the temperature at the head of a single crystal can be measured using a thermocouple, the temperature gradient within the crystal can be immediately estimated as described above, and the power of the heater in the furnace can be controlled thereby. Since diameter control is easy and response is quick, precise diameter control is possible.

(c) Since the temperature gradient of the single crystal can be directly detected, it is easy to find the low temperature gradient conditions in the vertical direction, and it is also easy to maintain the low temperature gradient. Can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of a conventional single crystal pulling apparatus. FIG. 2 is a longitudinal sectional view showing an example of a single crystal pulling apparatus used in an embodiment of the method of the present invention. Figures 3 (a) and (b) are schematic diagrams showing the state of single crystal pulling in an embodiment of the method of the present invention, (a) shows the time of seeding, and (b) shows the state of donkey single crystal pulling. show. FIG. 4 is a diagram showing the temperature of a single crystal during drawing by the method of the present invention. FIG. 5 is a side view showing an example of the mounting state of the thermocouple in the embodiment of the method of the present invention. FIG. 6 is a longitudinal sectional view showing a state before seeding in an embodiment of the method of the present invention. FIG. 7 is a longitudinal sectional view showing an example of a single crystal pulling apparatus used in another embodiment of the method of the present invention. 1... Crucible, 2... Furnace heating heater, 3...
Raw material melt, 4... Seed crystal, 5... Single crystal, 6... Side of heater, 7... Crucible bottom, 8, 15. 16... Power, 9. I7... Thermocouple, 10... Pulling shaft, 11
... protection tube, 12 ... B2O3 melt, 13 ... upper heater, 14 ... lower heater, m, l ... distance front,
'r,'rM...Temperature. 1st Figure 2 Figure 3 (Tff) 4th Figure 5 Figure 6 Calculation Figure 7

Claims (1)

[Claims] f+) In a method of pulling a single crystal using the Czochralski method, a thermocouple is provided below the side of the seed crystal at a position that will become the head of the single crystal to be grown. A single crystal pulling method characterized by controlling an in-furnace heater based on the temperature measured by a thermocouple. (2) The thermocouple should be placed 1 point from the side of the seed crystal tip.
0~] 5 mm below the claim 1
Method for pulling single crystals as described in section.