JP2621069B2 - Method for producing semiconductor silicon single crystal by FZ method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal of an FZ method in which a raw material polycrystal is partially heated and melted by using a high-frequency induction heating coil and the melting zone is moved to grow a single crystal. In particular, the present invention relates to a method for manufacturing a silicon single crystal rod having a uniform electric resistivity in a cross section of the single crystal rod.

[0002]

2. Description of the Related Art Conventionally, a rod-shaped raw material polycrystal is held on an upper axis, and a single crystal seed having a small diameter is held on a lower axis. One end of the polycrystal is melted by a high frequency induction heating coil and fused to the seed crystal. After the seeding, the apparatus for producing a rod-shaped semiconductor single crystal while zone melting the semiconductor rod while rotating the polycrystal in the opposite direction while dislocation-free by the seed drawing and relatively moving in the axial direction is an FZ method semiconductor single. Known as a crystal manufacturing apparatus.

In this apparatus, since it is necessary to melt the raw material polycrystal to the core in a short time in a narrow area, it is necessary to be able to apply an electric field concentrated on the zone melting area of the semiconductor rod. In order to stably grow a single crystal without a variation in impurities in the semiconductor after melting, and to suppress thermal distortion, it is necessary to gently radiate heat at the growth start end side of the single crystal growth interface in contact with the floating zone. is there.

[0004] Further, the above-mentioned dispersion of impurities is eliminated,
It is considered good to efficiently stir the melting zone in order to make the electrical resistivity in the cross section uniform, and it is conceivable to rotate the growing silicon single crystal at high speed and forcibly stir. Since the zone moves to the outer peripheral part by centrifugal force or supports the weight of the crystal rod by the narrowed part formed at the lower end of the single crystal rod, it cannot withstand high-speed rotation, and the growing single crystal rod collapses. This measure cannot be taken because of inconvenient phenomena such as inconvenience.

In order to alleviate the problems of the prior art, the inventor of the present invention has proposed a first single-turn induction heating coil having an inner diameter smaller than the outer diameter of a polycrystal and a first coil having a larger inner diameter than the first coil. A second induction heating coil having an inner diameter of at least the inner edge side of which faces the growth start end side peripheral portion of the single crystal growth interface, and performs zone melting of the raw material polycrystal by the first coil. In addition, the second coil heats the peripheral edge of the single crystal growth starting end while controlling the heat release rate, and facilitates zone melting and single crystal growth efficiently while reducing variation in impurity distribution. Has already proposed an FZ method semiconductor single crystal manufacturing apparatus capable of manufacturing a large-diameter and high-quality single crystal. (JP-A-63-29188)
No. 7)

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided an FZ method capable of reducing a variation in electric resistance distribution in a cross section of a single crystal rod of a product by using the FZ method semiconductor single crystal manufacturing apparatus.
It is an object of the present invention to provide a method for manufacturing a semiconductor silicon single crystal by a method.

[0007]

In order to solve the above-mentioned problems, a method for producing a semiconductor silicon single crystal by the FZ method according to the present invention comprises a first heating coil located inside and a second heating coil located outside. And the central axis of the first heating coil and the central axis of the raw material polycrystal are coaxial, and the central axis of the second heating coil and the central axis of the single crystal are arranged coaxially, and the diameter of the single crystal Thus, the rotation speed of the single crystal and the eccentricity of the first heating coil and the second heating coil are selected.

That is, in the FZ method semiconductor single crystal manufacturing apparatus, as a result of pursuing the single crystal manufacturing conditions in more detail in order to reduce the variation of the electric resistivity distribution in the cross section of the single crystal rod, it is preferable that The first heating coil located and the second heating coil located outside are provided eccentrically to each other, and furthermore, the central axis of the first heating coil and the central axis of the raw material polycrystal are arranged coaxially, and It has been found that it is better to arrange the central axis and the central axis of the single crystal coaxially.

Further, it is proposed that adjusting the rotation speed of the single crystal rod and the amount of eccentricity of the first and second heating coils according to the diameter of the single crystal is advantageous for achieving the object.

At this time, when the diameter of the single crystal is about 2.5 ", the eccentricity is 6 to 10 with respect to the rotation speed of the single crystal of 8 to 30 times / min.
When the diameter of the single crystal is 12 mm and the diameter of the single crystal is about 4.0 ″, the eccentricity is 4 to 14 with respect to the rotation speed of the single crystal 3 to 12 times / min.
When the diameter of the single crystal is about 5 "and the eccentricity is 3 to 16 mm with respect to the rotation rate of the single crystal of 2 to 6 times / minute, the electric resistance in the cross section of the single crystal rod becomes the most uniform. .

[0011]

In the FZ method semiconductor single crystal manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. 63-291887 and drawings, the first coil melts the floating zone of the raw material polycrystal, while the second coil starts the single crystal growth. The inner peripheral edge of the single crystal growth interface is gently heated by confronting the inner peripheral edge with the peripheral edge, and the temperature difference between the single crystal growth interface core portion and the outer portion is suppressed as much as possible. This has the effect of reducing the variation in the impurity distribution in the crystal rod cross section, that is, the variation in the electrical resistivity distribution.

However, under normal conditions, that is, under the condition that the first coil and the second coil are coaxial and the raw material polycrystal and the single crystal rod are also coaxial with them, the electric resistivity distribution in the cross section of the single crystal rod becomes Relatively large, not always satisfactory. Decentering the second coil with respect to the first coil,
Accordingly, even when the single crystal rod is moved to maintain the coaxial condition between the second coil and the single crystal, there are optimal conditions for the rotation speed and the amount of eccentricity of the single crystal rod according to the diameter of the single crystal. The present inventors have been able to elucidate the results of the research and have reached the present invention.

The agitation of the floating melting zone by the FZ method is based on the natural convection of the density difference due to the temperature difference, the convection of the surface tension based on the difference of the surface tension, and the rotation speed difference between the raw material polycrystalline rod and the single crystal rod. Without experimentation, it was not possible to determine which element would be effective in stirring the above-mentioned melting zone due to entanglement of extremely complex elements such as agitation, centrifugal stirring by rotation of a single crystal rod, and stirring by eccentricity. Not predictable. The centrifugal force is expected to have an effect on the stirring, which means that the diameter of the single crystal rod is also a factor of the stirring.

The present invention relates to an FZ in which the above complex elements are entangled.
In the method single crystal manufacturing apparatus, the impurity distribution in the cross section of the single crystal rod, that is, the electrical resistivity distribution and the relationship between the various elements were carried out in detail, the diameter of the single crystal rod of the present invention, the same rotation speed,
It has been found that the eccentricity of the first coil and the second coil is maintained in a special numerical range, so that the optimum condition can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an FZ method single crystal manufacturing apparatus used in the method of the present invention will be schematically described below with reference to the accompanying drawings.

FIG. 1 is a top view showing the arrangement of the first coil 4 and the second coil 6 when the method of the present invention is performed in the FZ single crystal manufacturing apparatus 2. FIG. 2 is a side view of FIG. FIG. 3 is an explanatory diagram showing the relationship between the eccentric positions of the first coil 4 and the second coil 6 and the eccentric positions of the raw material polycrystal 8 and the single crystal 10. The deviation between the central axis 4a of the first coil 4 and the central axis 6a of the second coil 6 is the amount of eccentricity w. 8a is the central axis of the raw material polycrystal, and 10a is the central axis of the single crystal. 12 is an electrode.

An example will be described in which the above-described apparatus is used to carry out various changes in the relationship among the diameter of the single crystal, the rotation speed of the single crystal, and the eccentricity of the first heating coil and the second heating coil. .

Experimental Example 1 A wafer having a thickness of 300 μm was cut from a predetermined position from a silicon single crystal rod having a diameter of 2.5 ″ into a cut plane, and the electrical resistivity ρ at all points was set to 4 at a pitch of 2 mm in an arbitrary orthogonal direction. The maximum value ρ was set to ρmax and the minimum value ρ was set to ρmin, and the in-plane electric resistance variation rate was defined by the following equation.

[0019]

Table 1 shows the relationship between the rotational speed (rpm), the amount of eccentricity (mm) and the RRG (%) when the silicon single crystal rod was manufactured by the FZ method.

[0021]

[Table 1]

From the results shown in Table 1, the conditions for obtaining a good RRG when the diameter is 2.5 "are as follows.
m, the eccentricity was confirmed to be 6 to 12 mm. The criteria for determining the quality of the RRG is 1% or less and 1%.
6% or more was rejected.

Experimental Example 2 An experiment was performed on a silicon single crystal rod having a diameter of 4 ″ in the same manner as in Experimental Example 1, and the results are shown in Table 2.

[0024]

[Table 2]

From the results shown in Table 2, it was confirmed that the conditions for obtaining a good RRG in the case of a 4 "aperture were a rotational speed of 3 to 12 rpm and an eccentricity of 4 to 14 mm.
The criteria for determining the quality of RRG is 17% or less and 17%.
The above was rejected.

Experimental Example 3 An experiment was carried out on a silicon single crystal rod having a diameter of 5 ″ in the same manner as in Experimental Example 1, and the results are shown in Table 3.

[0027]

[Table 3]

From the results shown in Table 3, it was confirmed that the conditions for obtaining a good RRG in the case of a diameter of 5 ″ were a rotation speed of 2 to 6 rpm and an eccentricity of 3 to 16 mm.
The criterion for determining the quality of RG was 17% or less as good and 17% or more as bad.

Example 1 At a rotation speed of 3 rpm, the eccentricity was 9 mm (using the double coil shown in FIGS. 1 and 2, the center of the single crystal and the polycrystal were shifted by 9 mm, and simultaneously the first coil and the second coil were also 9 mm) It shifts.)
A silicon single crystal rod having a diameter of 5 ″ was manufactured, and an electric resistance value ρ was measured at an interval of 2 mm in an arbitrary orthogonal direction in a cut plane of a wafer having a thickness of 300 μm from a predetermined position,
One example of a profile plotted against the distance in the circumferential direction from the center of the wafer is shown in FIG. RRG is 14.
It was 91%.

Comparative Example 1 In the same apparatus as in the example, only the first coil was installed.
A silicon single crystal rod having a diameter of 5 ″ was manufactured at a rotation speed of 3 rpm and an eccentricity of 9 mm (a deviation between the center of a single crystal and a polycrystal was 9 mm). The measurement was made and a profile was created in the same manner as in Fig. 4, and shown in Fig. 5. The RRG was 19.42%.

[0031]

As described above, according to the method for producing a semiconductor silicon single crystal by the FZ method of the present invention, it is possible to reduce the variation of the electric resistance distribution in the cross section of the produced silicon single crystal rod. To play.

[Brief description of the drawings]

FIG. 1 is a top view showing an arrangement of a first coil and a second coil when the method of the present invention is performed.

FIG. 2 is a side view of FIG.

FIG. 3 is an explanatory diagram showing a relationship between eccentric positions of a first coil and a second coil and eccentric positions of a raw material polycrystal and a single crystal.

FIG. 4 is a graph showing an example of a profile in which the electric resistance value of a silicon wafer manufactured by the method of the present invention is plotted with respect to the distance in the circumferential direction from the center of the wafer.

FIG. 5 is a graph showing one example of a profile in which electric resistance values of a silicon wafer manufactured by a conventional method are plotted with respect to a distance in a circumferential direction from a center of the wafer.

[Explanation of symbols]

 2 FZ method single crystal manufacturing apparatus 4 First coil 4a Central axis of first coil 6 Second coil 6a Central axis of second coil 8 Raw material polycrystal 8a Central axis of raw material polycrystal 10 Single crystal 10a Central axis of single crystal

Claims (2)

(57) [Claims] In a method of manufacturing a semiconductor single crystal by an FZ method in which a silicon single crystal is partially heated and melted by using a high-frequency induction heating coil and a single crystal is grown by moving a melting zone thereof, A first heating coil is located, and a second heating coil is located on the outside, the central axis of the first heating coil and the central axis of the raw material polycrystal are made coaxial, and the central axis of the second heating coil is simply A semiconductor silicon according to the FZ method, wherein the central axis of the crystal is arranged coaxially, and the rotation speed of the single crystal and the amount of eccentricity of the first heating coil and the second heating coil are selected according to the diameter of the single crystal. Single crystal production method. 2. The diameter of the single crystal, the rotation speed of the single crystal,
2. The FZ according to claim 1, wherein the relationship between the eccentricity of the first heating coil and the eccentricity of the second heating coil is set as follows.
A method for producing a semiconductor silicon single crystal by a method. Diameter Rotation speed rpm Eccentricity mm 2.5 "8 to 30 6 to 12 4.0" 3 to 12 4 to 14 5.0 "2 to 6 3 to 16