JPH0696479B2 - Single crystal pulling device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a single crystal pulling apparatus including a cooling cylinder for cooling a single crystal being pulled.

"Prior Art" As an example of a single crystal pulling apparatus of this type, Japanese Patent Laid-Open No. 61-68389
FIG. 5 shows a silicon single crystal pulling apparatus proposed in the publication.

In the figure, reference numeral 1 is a furnace body. In the furnace body 1, a quartz crucible 2 holding a molten silicon Y is fixed to an upper end of a rotary shaft 4 via a graphite susceptor 3. Further, a heater 5 and a heat retaining tube 6 are arranged around the crucible 2, and a pulling mechanism (not shown) is provided above the crucible 2 and a seed holding tool in which a seed crystal 8 is fixed by a pulling wire 7. 9 can be moved up and down and rotated.

Further, a cooling cylinder 10 is concentrically arranged around the pulled single crystal T with a gap, and is vertically fixed through the upper wall of the furnace body 1. The cooling cylinder 10 has a cylindrical shape, and a refrigerant passage (not shown) for passing cooling water or the like is formed inside thereof. Then, Ar gas is supplied into the furnace body 1 from the upper end of the cooling cylinder 10.

According to this apparatus, radiant heat to the single crystal T being pulled by the cooling cylinder 10 can be prevented, the single crystal T can be cooled, and the pulling rate can be increased.

[Problems to be Solved by the Invention] However, in the above apparatus, when it is attempted to further improve the cooling efficiency of the single crystal T to improve the productivity, the inner diameter of the cooling cylinder is reduced to reduce the distance from the single crystal. It must be made small, and there are problems that the single crystal T and the cooling cylinder 10 interfere with each other, and the flow of Ar gas deteriorates.

In addition, the present applicants have proposed in Japanese Patent Application No. 63-145260 a method for pulling up a silicon single crystal in which stacking faults are less likely to occur during high temperature processing in the semiconductor device process. This method
The silicon single crystal pulled from the molten metal is characterized by controlling the cooling temperature so as to pass through a temperature range of 850 to 1050 ° C with a residence time of 140 minutes or less. It has been found that the number of stacking faults generated after the heat treatment is small. Therefore, also from this point, it is earnestly desired to enhance the single crystal cooling effect by the cooling cylinder.

Therefore, the present inventors tried various experiments in order to improve the cooling effect by the cooling cylinder, and as a result, when a large number of uneven portions were formed on the inner surface of the cooling cylinder to increase the inner area, the cooling effect was improved more than expected. We have come to the knowledge that it is possible.

"Means for Solving the Problems" The present invention has been made to solve the above problems, and is characterized in that a concavo-convex portion is formed on the inner surface of the cooling cylinder to increase the inner area. The uneven portion may be a protrusion or a groove formed in the inner surface of the cooling cylinder at equal intervals in the circumferential direction and extending in the axial direction.

[Operation] According to this device, the unevenness is formed to increase the inner area of the cooling cylinder, thereby increasing the absorption rate of the heat rays emitted from the single crystal, and the heat exchange efficiency between the cooling cylinder and the atmosphere gas, Also, the heat exchange efficiency between the atmosphere gas and the single crystal is increased, and the cooling effect of the single crystal is improved.

"Embodiment" FIG. 1 shows a first embodiment of a single crystal pulling apparatus according to the present invention. The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

In this device, a cooling cylinder 20 is fixed through the upper wall of the furnace body 20.
A large number (in this case, 8) of protrusions (uneven portions) 21 ... That extend from the upper end to the lower end are formed on the inner surface of the plate at equal intervals in the circumferential direction. It is desirable that the projections 21 have an obtuse triangular shape in cross section, and the projection amount thereof is about 5 to 80% of the distance between the inner wall surface of the cooling cylinder 20 and the single crystal T. If it is smaller than that, the effect of increasing the inner area is small, and conversely if it is larger, the thermal effect of the ridges 21 on the single crystal T becomes too large, which may cause adverse effects such as uneven cooling. Further, as the number of the protrusions 21 increases, the cooling efficiency improves, but at the same time, the manufacturing cost also increases. Therefore, at least the pulled silicon single crystal
Care should be taken so that the residence time at 850-1050 ° C is 140 minutes or less.

The cooling cylinder 20 has a hollow structure in which an outer cylinder made of Mo, SUS, etc. and an inner cylinder made of the same material having a ridge are overlapped to form a uniform gap and both ends are sealed, for example, as shown in FIG. As shown in, the inside of the space is partitioned by partitions 22A and 22B, and a refrigerant passage 24 is formed over the whole. In the refrigerant passage 24, cooling water is circulated through a pair of supply pipes 23 fixed to both upper sides of the cooling cylinder 20, and a supply pipe (not shown) such as Ar gas is provided at the upper end of the cooling cylinder 20. Airtightly connected. Note that FIG. 3 is only an example of the refrigerant passage 24, and the refrigerant passage may be formed in a shape such as a double spiral shape.

In the single crystal pulling apparatus having the above structure, the cooling cylinder 20
Since the inner area is widened by forming the ridges 21 on the inner surface of the, the absorption rate of the heat ray radiated from the single crystal T is high, and the heat exchange efficiency between the cooling cylinder and the atmospheric gas, and
Both the heat exchange efficiency between the Ar gas and the single crystal T is improved, the cooling efficiency of the single crystal T is remarkably increased as compared with the conventional apparatus, and the productivity of the single crystal can be increased.

Further, if used in the production of silicon single crystal as described above, the pulled single crystal can be efficiently cooled, so that the residence time at 850 to 1050 ° C. of the single crystal can be easily reduced to 140 minutes or less, and the semiconductor It is possible to obtain an excellent single crystal in which stacking faults are less likely to occur even after the high temperature treatment in the device process.

Further, in this example, since the protrusions 21 extending in the vertical direction are formed as the concavo-convex portion, the action of adjusting the flow of Ar gas flowing in the cooling cylinder 20 is obtained, and the gas swirls in the cooling cylinder 20. The effect of preventing the impurities from adhering in the cooling cylinder 20 is high without winding and staying.

It should be noted that, instead of forming the protrusions 21 extending in the vertical direction on the cooling cylinder 20 as in the above-described embodiment, if necessary, a groove in the vertical direction, a large number of protrusions or grooves extending in the horizontal direction, or a spiral shape. It is also possible to form a ridge or groove, a large number of independent recesses or protrusions, or to fix a small heat exchange fin on the inner surface.
In order to increase the heat ray absorption rate, it is also effective to apply a paint such as black on the inner surface of the cooling cylinder 20 or to form the inner cylinder of the cooling cylinder 20 with a black material.

Further, the present invention is not limited to silicon, but may be applied to an apparatus for manufacturing another type of semiconductor single crystal. Furthermore, instead of changing the shape of the cooling cylinder to a truncated cylinder shape, forming a window for observing the crystal growth portion in the cooling cylinder, or directly fixing the cooling cylinder to the furnace body, the furnace is inserted via the rod body. A structure in which a cooling cylinder is suspended from the upper wall of the body 1, a structure in which the cooling cylinder is supported on the upper end of the heat retaining cylinder 6 via a flange member, and an elevating mechanism is attached to the cooling cylinder to provide a furnace body 1
It is also possible to implement a configuration such that the lifting operation can be performed inside.

"Experimental Example" Next, the effect of the present invention will be demonstrated with an experimental example.

(Experiment 1) Using the apparatus shown in FIG. 1 and a conventional apparatus (see FIG. 5) having exactly the same structure and dimensions except for the cooling cylinder 20, pull-up tests of silicon single crystals were performed. The diameter of the cooling cylinder, the supply amount of cooling water, the filling amount of the silicon raw material in the crucible, the diameter of the single crystal, the pulling speed, and the position of the cooling cylinder at the time of pulling were all unified in each device. Further, the cooling cylinder of the device of the present invention has a large number of protrusions with a protrusion amount of 20 mm formed on the inner surface in the vertical direction, and the internal area thereof is twice as large as that of the conventional device. As a result of the experiment, in the device of the present invention, the pulled single crystal 850
The residence time at ~ 1050 ° C was about 50 minutes, whereas the conventional device required about 100 minutes.

Then, two obtained silicon cut out wafers from a single crystal, these wafers, 2 ° C. / min was subjected to high-temperature heat treatment for raising the temperature to 1100 ° C., the at wafer from the conventional device about 50 cm ^-2 Stacking faults were detected by the density, but no stacking faults were detected in the wafer obtained by the apparatus of the present invention.

(Experiment 2) Next, the correlation between the size of the inner area of the cooling cylinder and the single crystal cooling effect was investigated.

A ridge extending in the axial direction (projection amount: 20 mm) on the inner peripheral surface of a cooling cylinder made of Mo, SUS with an internal diameter of 200 mm and a height of 100 mm that incorporates a refrigerant passage.
Several types of cooling cylinders having different inner areas were formed by forming a large number of them, and each of them was mounted on a pulling device to pull a silicon single crystal. On the other hand, as a comparative example,
A cooling cylinder (internal area S = 3140 cm ² ) of the same size without protrusions was used. The supply amount of cooling water, the filling amount of silicon raw material, the diameter of the single crystal, the pulling rate, and the position of the cooling cylinder during pulling were all unified.

The results of measuring the residence time required for the single crystal being pulled to pass through the temperature range of 850 to 1050 ° C are shown in Fig. 4.
As is clear from this graph, the internal area of the cooling cylinder and the residence time have a substantially inversely proportional relationship, confirming the effectiveness of the present invention.

"Effects of the Invention" As described above, the single crystal pulling apparatus according to the present invention has a wide inner area in which the ridge is formed on the inner surface of the cooling cylinder, so that the absorption of heat rays emitted from the single crystal is absorbed. As the rate increases, both the heat exchange efficiency between the cooling cylinder and the atmosphere gas and the heat exchange efficiency between the atmosphere gas and the single crystal are improved,
It is possible to increase the cooling efficiency of the single crystal, increase the growth rate of the single crystal, and improve the productivity as compared with the conventional apparatus.

Further, for example, when used in the production of silicon single crystal, it is easy to shorten the residence time of the pulled single crystal at 850 to 1050 ° C to 140 minutes or less, and stacking faults even after high-temperature treatment in the semiconductor device process. It is possible to produce an excellent single crystal in which is less likely to occur.

Further, when the protrusions extending in the vertical direction are formed as the uneven portions, the effect of adjusting the flow of the atmospheric gas flowing in the cooling cylinder can be obtained, and the effect of eliminating impurities is high.

[Brief description of drawings]

1 is a longitudinal sectional view showing an embodiment of a single crystal pulling apparatus according to the present invention, FIGS. 2 and 3 are plan and side views showing a cooling cylinder of the apparatus, and FIG. 5 is a graph showing the results of the experimental example of FIG. On the other hand, FIG. 5 is a longitudinal sectional view showing an example of a conventional single crystal pulling apparatus. Y: Silicon melt, T: Single crystal, 1 ... Furnace body, 2 ... Crucible, 20 ... Cooling cylinder, 21 ... Ridge (uneven portion), 23 ... Refrigerant supply pipe, 24 ... Refrigerant Road.

Claims (2)

[Claims] 1. A crucible for holding a molten metal, a pulling mechanism for pulling while raising a single crystal from the molten metal in the crucible, and a cooling cylinder concentrically arranged around the single crystal being pulled. A crystal pulling apparatus, wherein a concavo-convex portion is formed on the inner surface of the cooling cylinder. 2. The single crystal pulling apparatus according to claim 1, wherein the uneven portion is a plurality of protrusions or grooves formed in the inner surface of the cooling cylinder at equal intervals in the circumferential direction and extending in the axial direction. .