JPH01317188A - Production of single crystal of semiconductor and device therefor - Google Patents

Abstract

PURPOSE:To increase growth rate of single crystal pulled up by covering upper parts from an outer crucible to the inside of an inner crucible with a heat insulating plate and maintaining temperature of liquid level of semiconductor melt in the outer crucible higher than that of liquid level of semiconductor melt in the inner crucible. CONSTITUTION:A double crucible 1 consisting of an outer crucible 2 and an inner crucible 3 having a flow hole 4 at the bottom is set in a graphite crucible 7 vertically removably and rotatably supported on a pedestal 8 and semiconductor lump blended with a donor or acceptor impurities is put in the crucible 1. Then a heat insulating plate 12 consisting of a disc flange 13 having a hole at the central part and a flannel-shaped part or cylindrical part 14 is arranged at the upper part of the crucible 1 in such a way that the cylindrical part 14 is set close to the upper part of inner wall of the crucible 3. Then the semiconductor lump is heated and melted by heaters 9 and 10, temperature of liquid level of semiconductor melt between the crucible 3 and the crucible 2 is maintained higher than that of liquid level of semiconductor melt 5 in the crucible 2 and single crystal 6 of semiconductor is pulled up by seed crystal 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for manufacturing a semiconductor single crystal using a double crucible.

[Prior Art] As is well known, single-crystal semiconductor materials are used to manufacture various semiconductor devices, but since the characteristics of semiconductor devices are sensitive to the crystal structure, it is difficult to manufacture semiconductor single crystals. Crystal integrity is the primary requirement. For this reason, various methods for manufacturing semiconductor single crystals have been proposed in the past, and among them, the Czochralski method is widely used because it allows easy growth of single crystals. In this method, crystals are grown around a seed crystal from a molten semiconductor raw material in an inert gas atmosphere under reduced pressure, normal pressure, or pressurized. It is used when manufacturing crystals.

In manufacturing such semiconductor single crystals, impurities are added to obtain the desired resistivity, but in the Czochralski method described above, impurities change in the crucible as the crystal grows due to segregation. Therefore, the concentration distribution of impurities in the growth direction changes accordingly, making it impossible to obtain a large single crystal with a uniform concentration distribution. In order to improve these problems, a method of manufacturing a semiconductor single crystal using, for example, a double-structured crystal has been proposed.

As shown in FIG. 6, in this method, as the grown semiconductor single crystal 6 is pulled up, it is connected to the inner crucible 3 and the outer side through the communication hole 4 provided at the bottom of the inner crucible 3 or the lower part of the side wall. The melt (containing impurities with the same concentration as that taken into the single crystal 6 being pulled) flows unilaterally into the inner crucible 3. The impurity concentration within 3 is kept constant regardless of the growth of the single crystal.

In this way, according to the method of manufacturing a semiconductor single crystal using a double rutsuho, the impurity concentration within the single crystal can be made uniform, and the presence of the inner rutsuho 3 can reduce the heat of the melt. Since convection is reduced, it becomes possible to obtain a single crystal 6 of uniform quality. Furthermore, when manufacturing silicon single crystals, for example, in response to the decrease in raw material melt accompanying the growth of the single crystal,
By growing the single crystal while lowering the inner crucible 3 so that the depth of the internal melt remains constant, the oxygen concentration taken into the silicon single crystal can be made uniform.

[Problems to be Solved by the Invention] When the double-structure crucible as described above is directly applied to a Czochralski method apparatus, the following problems occur.

That is, since the peripheral wall of the inner Luppo 3 is exposed from the melt surface, heat is removed from the inner Luppor 3 by radiation, and the melt temperature drops rapidly near the inner Luppor 3. (4th
(see figure). Therefore, abnormal solidification called freezing occurs from the peripheral wall of the inner crucible 3, which inhibits the growth of single crystals.

In addition, to prevent freezing, the outer crucible 2
When a large amount of heat is input from the peripheral wall of the molten metal, the temperature of the melt near the center of the inner Ruppo 3, where crystal growth is performed, also rises, resulting in extremely slow single crystal growth rate and a decrease in productivity. This not only causes problems, but also has a negative impact on quality.

[Purpose of the Invention] The present invention has been made to solve the above-mentioned problems, and there is no fear of freezing when producing a semiconductor single crystal using a double-structured crucible, and moreover, it can be pulled easily. The object of the present invention is to obtain a method and apparatus capable of manufacturing a semiconductor single crystal with uniform directional quality.

[Means for Solving the Problems] The present invention has a double-structured crucible in which an inner crucible having a downward flow hole is disposed within an outer crucible, and a semiconductor melt placed in the crucible. In a method for producing a semiconductor single crystal by pulling up a liquid, the upper part from the outer crucible to at least the inside of the inner crucible is covered with a heat insulating plate, whereby the semiconductor melt between the outer crucible and the inner crucible is A method for producing a semiconductor single crystal, wherein the semiconductor single crystal is pulled from the inner crucible while maintaining the temperature of the surface higher than the temperature of the surface of the semiconductor melt in the inner crucible.

and a semiconductor single crystal manufacturing apparatus for carrying out this method, which includes a heat insulating plate provided above a double-structured crucible to cover from the outer crucible to at least the inside of the inner crucible. In addition, below the double-structured crucible,
The present invention provides an apparatus for manufacturing a semiconductor single crystal, which is provided with a heater that is controlled independently of the heater provided on the side of the double-structured melting hole.

[Operation] The seed crystal dropped into the melt of the double melt is gradually pulled up to grow a semiconductor single crystal. At this time, the center of the inner crucible is maintained at approximately a predetermined temperature by the heat insulating plate, and the temperature increases toward the outside. Therefore, since the vicinity of the peripheral wall of the outer crucible is at a high temperature, there is no risk of freezing. As the single crystal is pulled, the melt between the inner crucible and the outer crucible gradually flows in through the flow holes, so the amount of melt and impurity concentration in the inner crucible are maintained almost constant. Ru.

Embodiment of the Invention FIG. 1 is a sectional view schematically showing the main parts of an embodiment of the invention. In the figure, 1 is a double-structure crucible (hereinafter referred to as a double crucible) composed of an outer crucible 2 and an inner crucible 3, and the graphite crucible is supported on a pedestal 8 so as to be able to move up and down and rotate. It is set within 7. There is a communication hole 4 at the bottom of the inner melting hole 3 (bottom or bottom of the side wall).
are provided so that the melt 5 can flow through the flow holes 4. In the example, the outer crucible 2
The diameter of the crucible 3 is 50 cm, the diameter of the inner crucible 3 is 25 am, and the communication holes 4 are provided in two places, both of which have a diameter of 50 cm.
It was ++ua.

9.10 is a heater such as a resistance heating element installed outside the graphite crucible 7, which is configured to be independently controllable, and melts the raw material charged into the double crucible 1. , the raw material melt 5 is maintained at a predetermined temperature. 11 is a hot zone insulation material surrounding the heaters 9 and 10.

Reference numeral 12 denotes a heat insulating plate, for example, as shown in FIGS. 2 and 3, a disk-shaped flange 13 with a hole in the center is provided.
and a funnel-shaped part or cylindrical part (hereinafter referred to as the cylindrical part) 14 aligned with this hole and integrally fixed to the flange 13. It is arranged so as to be located close to the upper part of the inner wall of the crucible 3, and the flange I3 is fixed to the hot zone heat insulating material 12. The heat insulating plate 12 is made of graphite, and its outer surface is coated with quartz glass to prevent contamination.

Next, the present invention will be explained in detail with reference to an example in which a silicon single crystal is manufactured using the apparatus configured as described above. First, a polycrystalline silicon mass doped with donor or acceptor impurities was charged into double melt 1 and heated and melted using heaters 9 and 10. At this time, the liquid level of the silicon melt in the inner crucible 3 and the outer crucible 2 are kept at the same level, and the lower end of the cylindrical part 14 of the heat insulating plate 12 is lower than the liquid level of the silicon melt. It's slightly above.

Next, the wire 16 to which the seed crystal 15 with the <100> crystal orientation was attached was lowered to blend with the silicon melt 5 to perform narrowing. The narrowing conditions are 3nun in diameter,
The growth rate was about 2.4 to 3.0 mm/m+n.

After that, when the diameter of the silicon single crystal 6 was expanded to 15 cm and a constant diameter single crystal was pulled, the growth rate was 0.5 cm.
It was in the range of ~1.0 mm/m+n.

FIG. 4 is a diagram showing the results of measuring the surface temperature of the silicon melt in the double crucible 1 with and without the heat insulating plate 12, and the vertical axis represents the temperature of the melt surface. , the horizontal axis indicates the diametrical position of the double crucible. As shown in the figure, if there is a heat insulating plate 12, the double joint is in the center of 1 (
The liquid level of the silicon melt in the silicon single crystal 6 growth area) is maintained at a predetermined temperature, and exhibits a temperature gradient in which the temperature increases toward the outside. Therefore, there is no possibility that freezing will occur near the peripheral wall of the inner crucible 3.

On the other hand, when there is no heat insulating plate 12, the temperature of the surface of the silicon melt in the inner crucible 3 is maintained at approximately a predetermined temperature, but the temperature drops rapidly near the peripheral wall of the inner crucible 3. ing. Therefore, it is clear that freezing occurs from this part.

As is clear from the above measurement results, according to the present invention, no freezing occurred from the walls of the inner crucible 3 or other parts during the silicon polycrystal manufacturing process, and the silicon single crystal could be pulled normally. .

In addition, in this embodiment, two systems of heaters 9 and 10 that can be controlled independently are provided, so the control range of the heaters according to the thermal environment is expanded, and the double melt is Not only was it possible to precisely control the temperature distribution, but also the heater 10 could heat the double crucible 1 from below, making it possible to improve power efficiency by about 2%.

In addition, the heater may be installed only on the side of the double roof.
Alternatively, they may be provided independently on the sides and below.

FIG. 5 is a sectional view schematically showing another embodiment of the present invention. The present invention has a heat insulating plate 12 above a double crucible 1 in which a cylindrical inner crucible 3a having a flow hole 4 is disposed inside an outer crucible 2, and its functions and effects. is the first
This is almost the same as the embodiment shown in the figure.

In the above-mentioned embodiments, the case where a silicon single crystal is manufactured according to the present invention was exemplified, but it goes without saying that the present invention can also be applied to the manufacture of other semiconductors.

[Effects of the Invention] As is clear from the above description, the present invention prevents heat removal from the crucible peripheral wall by disposing a heat insulating plate above the double-structured crucible, and increases the temperature at the melt surface. Since a gradient is provided, there is no risk of freezing, and the single crystal can be pulled at an appropriate growth rate.

Further, according to the present invention, since the heat insulating plate blocks radiant heat applied to the pulled single crystal from the melt surface, heater, etc., cooling of the pulled single crystal is promoted, the growth rate is accelerated, and productivity is improved. Effects such as reduction in manufacturing costs can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention, and FIGS. 2 and 3 show embodiments of a heat insulating plate which is a main part of the present invention, and (a) is a perspective view, and FIG. (b) is a sectional view. Fig. 4 is a diagram showing the liquid surface temperature of silicon melt with and without a heat insulating plate, Fig. 5 is a sectional view schematically showing another embodiment of the present invention, and Fig. 6 1 is a cross-sectional view showing an example of a semiconductor manufacturing apparatus using a conventional double-structured crucible. 1. La+double crucible, 2: Outer crucible, 3°3a:
Inner crucible, 4: Distribution hole, 6: Semiconductor single crystal, 7: Graphite crucible, 9, 10: Heater.

Claims (3)

[Claims] (1) It has a double-structured crucible in which an inner crucible with a flow hole at the bottom is disposed inside an outer crucible, and a semiconductor single crystal is produced by pulling up the semiconductor melt placed in the crucible. In the method, the upper part of the outer crucible to at least the inside of the inner crucible is covered with a heat insulating plate, thereby controlling the temperature of the semiconductor melt surface between the outer crucible and the inner crucible to the temperature in the inner crucible. Maintained at a higher temperature than the surface of the semiconductor melt,
A method for producing a semiconductor single crystal, comprising pulling the semiconductor single crystal from the inner crucible. (2) A semiconductor melt placed in a double-structured crucible in which an inner crucible having a flow hole at the bottom is disposed inside an outer crucible is heated by a heater provided on the side of the crucible;
The apparatus for producing a semiconductor crystal by pulling up a semiconductor melt from the inner crucible is characterized in that a heat insulating plate is provided above the double-structured crucible to cover from the outer crucible to at least the inside of the inner crucible. Semiconductor single crystal manufacturing equipment. (3) A semiconductor single crystal according to claim 2, characterized in that a heater is provided below the double-structured crucible and is controlled independently of a heater provided on the side of the double-structured crucible. manufacturing equipment.