JPH02216424A - Thermocouple - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding the structure of a thermocouple, especially a thermocouple for measuring melt temperature in single crystal growth, at least the tip part is bent and does not deform even in high temperature semiconductor melt. The purpose of the present invention is to provide a thermocouple that does not cause contamination of the melt. and a quartz protection tube that has an arcuate shape with the same radius as the tube and encloses an arcuate insulating tube into which the thermocouple element wire is inserted.

[Industrial application field]

The present invention relates to a thermocouple, and particularly to the structure of a thermocouple for measuring the temperature of a melt in semiconductor single crystal growth.

Semiconductor single crystals such as silicon (Si), gallium arsenide (GaAs), and indium v4 (InP) are grown from melts. In particular, a single crystal pulling method called the Czochralski method (CZ) method is often used for its growth, but in order to pull a high quality single crystal with few defects and a uniform resistivity distribution, it is necessary to temperature distribution,
It is necessary to accurately understand and control temperature fluctuations, changes over time, etc. In this case, it is most important to understand the temperature directly below the single crystal that is being pulled. Furthermore, when pulling a Si single crystal, the temperature of the melt is 1500 to 1600°.
The temperature will be around C. On the other hand, a thermocouple is used to measure the temperature of the melt when pulling a single crystal. A structure that does not cause contamination of the liquid or deformation of itself is desired.

[Conventional technology]

FIG. 4 is a schematic side cross-sectional view showing the pulled state of a Si single crystal by the CZ method. In the figure, 50 is a carbon heater, 51 is a carbon crucible, 52 is a quartz crucible, 53 is an St melt, 5
4 is a shaft for rotating a quartz crucible (carbon crucible), 5
5 is a Si single crystal, 56 is a seed crystal, 57 is a crystal clamper,
58 is a crystal pulling wire, mI is a pulling direction arrow, m2
indicates an arrow indicating clockwise rotation, and 1Y13 indicates an arrow indicating counterclockwise rotation.

When pulling the Si single crystal 55 using this method, first, polycrystalline Si is placed in a quartz crucible 52, and then heated by a carbon heater 50 through a carbon crucible 51 by direct current heating, for example, while rotating in a clockwise direction m2.
The polycrystalline Si is heated to about 0''C and melted to form a Si melt 53 at a predetermined temperature.The atmosphere is an inert atmosphere such as argon.Then, the crystal pulling wire is lowered to remove the seed crystal. 55 is immersed in the Si melt 53, it is rotated in the counterclockwise direction m and then gradually pulled up in the ml direction at a predetermined speed, so that the Si single crystal 55 is sequentially grown in a columnar shape at the tip of the seed crystal 56. In this growth, the most effective temperature measurement part for controlling the crystal growth state is the region A.Also, when polycrystalline St is melted, large Si crystal grains that are not melted are located in the upper part of the quartz crucible 52. 59 may remain.

On the other hand, as shown in FIG. 5, which shows an axial cross section (a) and a cross section perpendicular to the axis, the thermocouple that has been widely used in the past has a long thermocouple wire 60 that also serves as an aggregate (beam). It had a linear structure in which the wire was inserted into a wire insertion hole 62 of a straight insulating tube 61 and then inserted into a straight quartz protection tube 63 to be enclosed therein.

Therefore, even if this thermocouple is inserted diagonally as shown by the chain line 64 in FIG. When Si crystal grains 59 are attached to the upper part of the quartz crucible 52, the 81 crystal grains 59 obstruct the thermocouples near the side wall of the crucible 52, as shown by the chain line 64 in the figure. There was a problem in that the temperature of the melt 53 in the area could not be measured.

Therefore, as shown in the schematic cross section in the axial direction in FIG.
An L-shaped electrocouple (a) enclosed in a J-shaped quartz protection tube 263 or a J-shaped electrocouple (b) enclosed in a J-shaped quartz protection tube 263 was prototyped.
An attempt was also made to make it possible to measure the melt temperature directly under the i single crystal and under the Si crystal grains (60 is a thermocouple wire).

However, in these conventional curved couplers, the insulating tube 161 is segmented and does not function as an aggregate (beam). When immersed in the melt for a long time, the quartz protection tube 163, 263, etc. softens and St
Because the buoyant force exerted by the melt gradually deforms it upward, there is a problem in that it becomes impossible to measure the temperature of a fixed location over a long period of time.

[Problems to be Solved by the Invention] When pulling a semiconductor single crystal, it is possible to remove the melt directly below the single crystal or in a certain area near the side wall of the crucible where crystal grains tend to adhere to the top, without contaminating the semiconductor melt. It is necessary to measure the liquid temperature over a long period of time, but as mentioned above, with conventional thermocouples, this measurement is almost impossible due to structural inadequacies or thermal deformation.

Therefore, in order to make the above measurement possible, the present invention provides a thermocouple that has at least a bent tip, does not deform even in high-temperature semiconductor melt, and does not cause η staining of the melt. purpose.

[Means for Solving the Problem] The above problem is solved by an insulating tube having at least the part inserted into the object to be measured having a single arc shape into which a thermocouple element wire is inserted, and an insulating tube having the same radius as the insulating tube. This problem is solved by the thermocouple according to the present invention, which is constituted by a quartz protection tube containing an arc-shaped insulating tube having an arc shape and into which the thermocouple element wire is inserted.

[For production]

That is, in the present invention, the insulating tube into which the thermocouple element wire is inserted and the quartz protection tube into which the insulating tube is inserted are formed into an arc shape having the same radius, and are bent into an arc shape with an integral structure without being segmented. To easily insert a curved insulating tube from the end to the tip of a quartz protection tube bent into an arc shape. As a result, an integral insulating tube that has an extremely high softening point and does not deform at the temperature of the semiconductor melt exists as a beam inside the quartz protective tube, allowing the temperature of the melt to be measured. The buoyancy inside the thermocouple prevents it from deforming.

As a result, during crystal pulling growth, the bent shape allows measurement of the temperature of the melt directly below the single crystal and near the side walls of the crucible, where crystal grains tend to adhere to the upper part, while being enclosed in a protective tube that does not contaminate the melt. Provided is a thermocouple which has the following properties and does not undergo deformation during melt temperature measurement.

〔Example] The present invention will be specifically explained below with reference to illustrated embodiments.

FIG. 1 is a schematic axial cross-sectional view (a) and a schematic cross-sectional view perpendicular to the axis of an embodiment of the present invention, and FIG. 2 is a schematic diagram of a melt temperature measurement state according to an embodiment of the present invention. (a) shows the measurement state directly below the pulled single crystal, (b) shows the measurement state of the region near the side wall of the crucible below the crystal grain, and FIG. 3 is a schematic axial cross-sectional view of another example of the present invention.

Identical objects are indicated by the same reference numerals throughout the figures.

The thermocouple according to the present invention has a complete arc shape from the tip to the end, as shown in FIGS. 1(a) and Cb), the radius r of the arc is 20 to 200 mm, and the opening of the arc is The angle θ is 90 degrees, the inner diameter is 3.5 mm, and the wall thickness is 0.5 m.
m, an arc-shaped quartz protection tube 1 with one end (tip) closed, and an external shape 3III inserted into this protection tube 1
An arc-shaped insulating tube 2 having two wire insertion holes 3A and 3B with a diameter of about 1ffII11 and a platinum wire with a diameter of about 0.5 mm inserted into the wire insertion holes 3A and 3B of this insulating tube 2. - Thermocouple wire 4 made of platinum/rhodium or tungsten/tungsten/rhenium.

Note that since the arc-shaped quartz protection tube 1 and the arc-shaped insulating tube 2 are completely arc-shaped and have the same arc radius, insertion of the arc-shaped insulating tube 2 into the arc-shaped quartz protection tube 1 is is easy.

Furthermore, when the thermocouple wire 4 is hard and has poor flexibility, such as tungsten-tungsten-rhenium, the thermocouple wire 4 is also formed in advance into an arc shape with the same radius.

FIG. 2(a) shows the temperature of the Si melt 53 in the area A near the bottom directly below the Si single crystal 55 that is being pulled up during the pulling of the Si single crystal using the fully arcuate thermocouple 5 of this embodiment. 6 is a thermocouple clamper, 7 is a protective guide tube for the thermocouple wire, 50 is a carbon heater, 51
52 is a carbon crucible, 52 is a quartz crucible, 54 is a rotating shaft, 56 is a seed crystal, 57 is a crystal clamper, and 58 is a crystal pulling wire.

In addition, FIG. 2 rb> shows a quartz crucible located below Si crystal grains 59 that are attached to the upper part of the side wall of the quartz crucible 52 without being completely melted and are rotating together with the quartz crucible 52 due to the perfectly circular thermocouple 5. 52 shows a state in which the temperature of the Si melt 53 in the region ^2 near the side wall is being measured, and the symbols other than the above indicate the same objects as in FIG. 2(a).

As shown in FIGS. 2(a) and 2), the fully arcuate thermocouple 5 according to the present invention can measure the temperature of the melt in the region hidden under the Si single crystal 55 or the Si crystal grains 59. is easily done. Moreover, as shown in FIG. 1, since the arc-shaped insulating tube 2 exists as an aggregate (beam) inside the thermocouple 5, the arc-shaped quartz protection tube 1 is exposed to the high temperature of the Si melt 53. Even when an attempt is made to deform, the deformation is suppressed by the aggregate function of the insulating tube 2. Therefore, long-term measurement of the -tail region can be performed with high accuracy.

FIG. 3 shows another embodiment in which the above-described fully arcuate thermocouple 5 is provided with a linear support portion 10 consisting of a linear insulating tube 8 having a wire insertion hole (not shown) and a linear quartz protection tube 9. It is. In this structure, the thermocouple wire 4 of the complete arc-shaped thermocouple 5 is left long 7, the wire 4 is inserted into a straight insulating tube 8, and the arc-shaped insulating tube 2 and the straight insulating tube 8 are connected. After the joint is fixed, for example, by caulking the molybdenum (Mo) vibrator 11, the straight quartz protection tube 9 is placed over the straight insulating tube 8, and the joint between the arcuate quartz protection tube 1 and the straight quartz protection tube 9 is fixed. It is formed by fixing by welding (12 is a welded part) or the like.

In this structure, the thermocouple is supported by the linear support part 10, but as described above, the arc-shaped insulating tube 2 which has the function of an aggregate and the linear insulating tube 8 which has the function of an aggregate. Since the Mo pipe 11 is firmly fixed by caulking or the like, there is no possibility that the part inserted into the melt will be deformed and floated when measuring the melt temperature, and the measurement position will not change.

It should be noted that the structure of this embodiment is better than the above-mentioned complete arc shape.
It is easier to support and handle in practical use.

〔Effect of the invention〕

As explained above, according to the present invention, there is no contamination of the semiconductor melt contained in the quartz protection tube, and from the top surface, such as directly below the bottom surface of the single crystal being pulled up or from the bottom of granular deposits, etc. Provided is a thermocouple that can easily measure the temperature of the melt in a hidden region, and that is not deformed by the temperature of the melt, so that it can measure a fixed location with high precision over a long period of time. Therefore, the present invention is effective in improving the quality of semiconductor single crystals pulled by the CZ method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, in which (a) is an axial cross-sectional view, (b) is a cross-sectional view perpendicular to the axis, and FIG. 2 is a melt temperature according to an embodiment of the present invention. A schematic diagram of the measurement state, (a
) is directly below the single crystal, (1)) near the side wall of the crucible, FIG. 3 is a schematic axial cross-sectional view of another embodiment of the present invention, and FIG. 4 is a schematic cross-section of a Si single crystal pulled by the CZ method. Figure 5 is a schematic diagram of a conventional straight thermocouple, (a) is a cross-sectional view in the axial direction, (b) is a cross-sectional view in the direction perpendicular to the axis, and Figure 6 is an axial cross-sectional view of a conventional bent thermocouple. In the schematic directional cross-sectional views, (a) is an L-shape, and (b) is a J-shape. In the figure, 1 is an arcuate quartz protection tube, 2 is an arcuate insulating tube, 3A and 3B are thermocouple wire insertion holes, and 4 is a thermocouple wire. (α〕m direction cross section 'o) A section in the direction of (to) the axis I
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Claims (1)

[Scope of Claims] An insulated tube in which at least a portion inserted into the object to be measured has an arc shape into which a thermocouple wire is inserted, and an arc shape with the same radius as the insulated tube, 1. A thermocouple comprising: a quartz protection tube enclosing an arc-shaped insulating tube into which the thermocouple wire is inserted;