JPS6033297A - Pulling device for single crystal semiconductor - Google Patents

Abstract

PURPOSE:To widen the range of elements to be prepared and to reduce ununiformity of concn. of minute impurities by changing the direction of magnetic field impressed on molten starting material for semiconductor in a crucible by changing the direction of current to be fed to a magnetic field impressing means. CONSTITUTION:When electric current is fed in the same direction to superconductive magnets 12, 13, magnetic field in the oblique direction is impressed to molten silicon 9, and both horizontal component and perpendicular component of convection in the molten silicon 9 are retarded. Therefore, the concn. of impurities (and concn. of oxygen) in the single crystal silicon 10 are made relatively low, simultaneously, the ununiformity of the concn. of minute impurities is reduced. Further, horizontal component of the convection in the molten silicon 9 is chiefly retarded if current is passed through the superconductive magnet 12, 13 in the reverse direction, but the retarding effect for the perpendicular component is small. Accordingly, the concn. of impurities (and concn. of oxygen) in the single crystal silicon 10 are made relatively high, and simultaneously, the ununiformity of concn. of minute impurities are made extremely small.

Description

[Detailed description of the invention] The present invention relates to improvements in single crystal semiconductor pulling equipment.

Single crystal semiconductors used for manufacturing semiconductor devices are mainly manufactured by the Czochralski method (CZ method). Conventionally, a single crystal semiconductor pulling apparatus as shown in Fig. M1 has been used in this CZ method.

That is, numeral 1 in the figure is a chamber whose top and bottom are open. A rotatable support rod 2 is inserted into the lower opening of the chamber 1, and a graphite protector 3 is supported on the support rod 2 to protect the quartz g4'z. A cylindrical heater 5 and a heat retaining tube 6 are sequentially arranged around the outer periphery of the protector 3. Further, a chain 7, for example, is suspended from the upper opening of the chamber 1, and holds a seed crystal 8.

In the C2 method using the above-mentioned pulling device, for example, when manufacturing single crystal silicon, a silicon raw material is put into a crucible 4, the silicon raw material is melted by a heater 5, and a seed crystal is added to this molten silicon 9. Soak 8, Ruth? By pulling up the chain 7 while rotating the seed crystal 4 and the seed crystal 8 in opposite directions, the crystalline silicon 10 is pulled up.

By the way, during pulling of single crystal silicon, forced convection and thermal convection occur in the molten silicon 9 in the crucible 4, and the temperature distribution, impurity concentration, and oxygen concentration of the molten silicon 9 near the crystal growth field Ffij become non-uniform. It has become.

For this reason, the pulled single crystal silicon 1o has poor uniformity in resistivity distribution and oxygen concentration distribution in both the growth direction and the radial direction, making it difficult to supply high-quality wafers for ultra-large scale integrated circuits. Met.

Therefore, there is a method in which two electromagnets with different polarities are placed facing each other at positions corresponding to both sides of Ruth 4, and a horizontal magnetic field is applied to the molten silicon 9. (hereinafter referred to as vertical M
Convection in the molten silicon 9 (abbreviated as CZ) is suppressed to make the physical properties of single crystal silicon uniform.

In the horizontal MCZ described above, it is possible to suppress the mainly vertical component of the convection in the bath molten silicon 9, and it is possible to make the impurity concentration and oxygen concentration of single crystal silicon uniform to some extent, but these values You can only get something low. In addition, in the vertical MCZ described above, it is possible to suppress the mainly horizontal component of convection in the molten silicon 9, and to make the temperature distribution near the crystal growth interface, the impurity distribution, etc. uniform, and the impurity of the single crystal silicon Although it is possible to make the concentration and oxygen concentration fairly uniform, only high values of these values can be obtained. Therefore, wafers processed from single crystal silicon obtained by horizontal MCZ or vertical MCZ can only be used to manufacture devices for limited purposes.

The present invention has been made in view of the above circumstances, and is capable of manufacturing a single crystal semiconductor that can be manufactured in a wide range of devices and that can manufacture high quality single crystal semiconductors with little non-uniformity and zero degree of micro impurities. We try to provide all the above equipment.

That is, in the single crystal semiconductor pulling apparatus of the present invention, two semicircular arc-shaped magnetic field applying means are arranged at positions corresponding to the outer periphery of the screw, and the direction of the current flowing through these magnetic field applying means is changed. This method is characterized by arbitrarily changing the direction of the magnetic field applied to the molten semiconductor raw material in the crucible.

In this way, by arbitrarily changing the direction of the magnetic field applied to the molten semiconductor raw material, it is possible to arbitrarily change the way convection is suppressed, so the impurity concentration in the single crystal semiconductor can be controlled over a wide range. Moreover, the inconsistency of the fine impurity concentration lW can be completely reduced.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 5. Incidentally, the same members as those of the conventional lifting device shown in FIG. 1 will be designated by the same numbers and their explanation will be omitted.

As shown in FIGS. 2 and 3, a Holling-shaped liquid helium tank 1 is disposed around the outer periphery of the chamber 1, and inside this liquid helium tank 11 there are two semicircular arc-shaped superconducting Magnets 12.13 are arranged. Liquid helium is supplied to the liquid helium tank 11 from a liquid helium refrigerator 14 . Said superconducting magnet, t12
．． 13 means that a straight line current flows, and a circle M is placed around it.
It is designed to generate an i-field.

The pulling of single crystal silicon 1o using the above-mentioned pulling device is as follows:
The operation is substantially the same as the conventional apparatus, except that a current is passed through the superelectric ζ magnets 12 and 13 to apply a magnetic field to the molten silicon 9, and a substantially direct current is passed through the heater 5.

At this time, as shown in Fig. 4, the superconducting magnet 12.13
When a current is passed in the same direction, two superconducting magnets 12.
The direction of the magnetic field synthesized by 13 is as shown by the broken line in the figure.

In addition, as shown in Fig. 5, when current is passed through the superconducting magnets 12.13 in opposite directions, the two superconducting magnets 12.1
The direction of the magnetic field synthesized by 3 is different from that in the M%4 diagram, as shown by the broken line in the figure. The magnetic field thus applied is applied almost uniformly to any position of the molten silicon 9.

According to the above-mentioned pulling device, when a current is applied to the superconducting magnets 12 and 13 in the same direction as shown in FIG. Both the horizontal and vertical components of can be suppressed. Therefore, the impurity concentration (and oxygen concentration) in the single crystal silicon 10 can be made relatively low, and the non-uniformity of the minute impurity concentration can be made considerably small.

Furthermore, when current is passed in the opposite direction through the superconducting magnets 12 and 13 as shown in FIG. 5, it is possible to suppress mainly the horizontal component of the convection in the molten silicon 9, which has the effect of suppressing the vertical component. is small. Therefore, single crystal silicon 1
The impurity concentration (and oxygen concentration) in zero can be made relatively high, and the non-uniformity of the minute impurity concentration can be made extremely small.

In fact, single-crystal silicon is pulled using a normal CZ, a horizontal MCZ, a vertical MCZ, and the pulling apparatus of the above embodiment, and the control range of its impurity concentration (specific low resistance value), non-uniformity of minute impurity concentration, and oxygen concentration are As shown in the table below, the control range of impurity concentration (resistivity) and oxygen concentration is wide when using the pulling device of the above example, and the non-uniformity of minute impurity concentration is reduced. was confirmed to be small.

Note that the pulling device of the present invention is not limited to the structure shown in the above embodiment, and as shown in FIGS. Make the mechanism so that it can move, and change the height of the superconducting magnet 12'l13'. A magnetic field may be applied to the molten silicon 9 within 4. Note that FIG. M6 shows the case where currents 'f and ηL are applied to the superconducting magnets 12' and 13' in the same direction, and FIG. 7 shows the case where the currents are applied to the superconducting magnets 12' and 13' in opposite directions.

If the heights of the superconducting magnets 12' and 13' can be changed in this way, the superconducting magnets 12', 13',
In addition to changing the direction of the current flowing through 13', these 1
Since the direction of the magnetic field applied to the molten silicon 9 can be changed by changing the δ value, the impurity concentration can be more easily controlled.

In addition, although the above description has been made regarding the case of manufacturing single crystal silicon, it goes without saying that the present invention is similarly applicable to the case of manufacturing single crystal tm of GaAs+ or the like.

As detailed above, according to the single crystal semiconductor pulling apparatus of the present invention, it is possible to widen the control range of 1 lilJ of the impurity concentration of a single crystal semiconductor, and moreover, it has remarkable effects such as being able to reduce the non-uniformity of the minute impurity concentration. It is something that plays.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional single crystal semiconductor pulling device, FIG. 2 is a sectional view of a single crystal semiconductor pulling device in an embodiment of the present invention, FIG. 3 is a schematic plan view of the same device, and FIG. 4 is a sectional view of a conventional single crystal semiconductor pulling device. and FIG. 5 are explanatory diagrams showing the direction of the magnetic field when the same apparatus is used, and FIGS. 6 and 7 are explanatory diagrams showing the direction of the magnetic field when the same apparatus is used, respectively. FIG. 2 is an explanatory diagram showing the direction of a magnetic field. DESCRIPTION OF SYMBOLS 1... Chamber, 2... Support rod, 3... Protector, 4... Ludde, 5... Heater, 6... Heat insulation cylinder,
7... Chain, 8... Seed crystal, 9... Molten silicon, 10... Single crystal silicon, 11.11'...
Liquid helium tank, 12, 12', 13, 13
'...Superconducting magnet, 14...Liquid helium refrigerator. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A single crystal is rotatably supported in a chamber, and a seed crystal suspended rotatably from above the crucible is immersed in the molten semiconductor raw material in the crucible, and the seed crystal is pulled up. In the manufacturing equipment, two semicircular arc-shaped magnetic field applying means ft are arranged at positions corresponding to the outer periphery of the sill tube, and by changing the direction of the current flowing through these magnetic field applying means, the molten semiconductor raw material in the silt is heated. A single crystal semiconductor pulling device characterized by arbitrarily changing the direction of an applied magnetic field.