JP2949571B2 - Single crystal growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single crystal growth apparatus, and more particularly to a single crystal growth apparatus for growing a semiconductor single crystal such as germanium or silicon.

[0002]

2. Description of the Related Art There are various methods for growing a single crystal, one of which is the Czochralski method (hereinafter referred to as CZ method). FIG. 4 is a cross-sectional view schematically showing a single crystal growth apparatus used in the conventional CZ method, and in the figure, 31 indicates a crucible.

The crucible 31 includes a bottomed cylindrical inner holding container 31a made of quartz, and a bottomed cylindrical outer holding container 31b fitted to the outside of the inner holding container 31a. The crucible 31 is supported by a support shaft 39 that rotates at a predetermined speed in the direction of the arrow in the figure. Outside the crucible 31 is a heater 32 of resistance heating type,
Outside the heater 32, a heat retaining cylinder 42 for promoting heat transfer to the crucible 31 is arranged concentrically. In the crucible 31, a melt 33 of a single crystal raw material melted by the heater 32 is provided. It is designed to be filled.

A lifting shaft 34 made of a lifting rod or a wire is suspended from the center axis of the crucible 31.
The seed crystal 35 attached to the tip of the pulling shaft 34 via a seed crystal holding jig 34 </ b> A is brought into contact with the surface of the melt 33, and the pulling shaft 34 is coaxial with the support shaft 39 in the same direction or in the opposite direction. By pulling up while rotating at a predetermined speed, the melt 33 is solidified and the single crystal 36 is grown.

FIG. 5 is a partially enlarged front view showing a part of a lifting rod as a lifting shaft.

In the drawing, reference numeral 34a denotes a pulling rod having a diameter of about 66 mm, and the pulling rod 34a forms a pulling shaft. A seed crystal holding jig 34A is attached to a lower end of the pulling rod 34a, and a seed crystal 35 is attached to a lower end of the seed crystal holding jig 34A.

In the single crystal growth apparatus equipped with the pulling rod type pulling shaft, the pulling rod 34a is vertically moved vertically, so that the single crystal 36 is pulled while the single crystal 36 is pulled and the single crystal 36 is taken out. The lateral deflection of the crystal 36 can be almost eliminated.

However, in some cases, shear stress is applied to the single crystal 36 due to the occurrence of torsional vibration or the like. In this case, the shear stress tends to concentrate on the neck portion 36a of the single crystal 36, and the neck portion 36a breaks and the single crystal 36 breaks. There is a possibility that the crystal 36 will fall.

Further, since the verticality of the lifting rod 34a depends on the mechanical precision, precision of the lifting rod 34a support portion is required to obtain the verticality.

FIG. 6 is a partially enlarged front view showing a part of a wire as a lifting shaft.

In the figure, reference numeral 34b denotes a wire having a diameter of about 4 mm, and a seed crystal holding jig 34A is attached to the lower end of the wire 34b.

In the single crystal growing apparatus equipped with the wire-type pulling shaft, the shear stress due to the torsional vibration or the like is absorbed by the wire 34b and hardly acts on the single crystal 36, and the verticality of the wire 34b is mechanical. Since there is no dependence on the precision of the wire 34b, no extreme precision is required when the wire 34b is installed.

[0013]

However, in the above-mentioned wire type single crystal growing apparatus, when the single crystal 36 is shaken, it is difficult to suppress the swing, and there is a risk that the single crystal 36 may fall. This is particularly dangerous when the single crystal 36 to be pulled is large.

In addition, it is necessary to increase the diameter of the wire 34b as the size of the single crystal 36 increases, and in this case, the winding habit in the drum becomes remarkable, and the verticality of the wire 34b is hindered. There was a problem that a case might arise.

Further, due to the structure in which the wire 34b is wound up by a drum, the deterioration of the wire 34b is unavoidable, and it is necessary to periodically replace the wire 34b with a new one. There has been a problem that the single crystal to be pulled may be adversely affected and the product yield may be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and prevents the swinging of a single crystal even when a large single crystal is pulled, and does not increase the number of times of pulling shaft replacement. An object of the present invention is to provide a single crystal growth apparatus capable of safely growing a single crystal without lowering the product yield while maintaining verticality.

[0017]

In order to achieve the above object, a single crystal growth apparatus according to the present invention has a wire interposed between a pulling rod for pulling a single crystal and a seed crystal holding jig. It is characterized by having.

According to the single crystal growing apparatus having the above structure, it is possible to suppress the torsional vibration from acting on the single crystal by the wire interposed between the pulling rod and the seed crystal holding jig. The load due to the shear stress acting on the neck portion of the single crystal is greatly reduced as compared with the pulling shaft composed of a rod, and the safety is greatly improved.

Further, since the basic part of the pulling shaft is constituted by a pulling rod and its wire length is very short as compared with a conventional pulling shaft made of a wire, the single crystal does not oscillate. Since there is no need to perform winding by a drum, the winding habit does not occur on the pulling shaft and the verticality of the pulling shaft is not hindered, and the wire hardly deteriorates.

Further, in the single crystal growth apparatus according to the present invention, a wire is interposed between a pulling rod for pulling a single crystal and a seed crystal holding jig, and a cylindrical guide is provided around the wire. It is characterized by:

According to the single crystal growth apparatus having the above structure, since the wire is substantially covered by the cylindrical guide, even if a force causing a large swing to the single crystal is applied, the wire is restricted by the cylindrical guide, Even if a minute amount of dust is generated, it is possible to prevent the dust from adversely affecting the single crystal.

Therefore, even when a large single crystal is pulled, the single crystal does not sway and the single crystal can be grown safely without lowering the product yield while maintaining the verticality of the pulling shaft. Can be done.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a single crystal growth apparatus according to an embodiment will be described with reference to the drawings. Components having the same functions as in the related art are denoted by the same reference numerals.

<Embodiment 1> FIG. 1 is an enlarged partial cross-sectional view showing a part of a pulling shaft constituting a single crystal growing apparatus according to a first embodiment. In FIG. 1, reference numeral 14 denotes a pulling shaft. The seed crystal holding jig 3 is provided at the lower end of the pulling shaft 14.
4A is connected, and a seed crystal 35 is attached to the lower end of the seed crystal holding jig 34A. Lift shaft 14
Is formed by a pull-up bar 14a, and a wire 14b is interposed between the center of the bottom surface of the pull-up bar 14a and the center of the upper surface of the seed crystal holding jig 34A. The lifting shaft 14 including the lifting rod 14a and the wire 14b
Is composed. Other configurations are the same as those of the single crystal growth apparatus shown in FIG.

The lifting rod 14a is made of SUS, molybdenum or the like and has a diameter of 30 to 300 mm and a length of 1.5 to 1.5 mm.
It is desirable to have a rod shape of about 4 m.
It is desirable that b has a diameter of about 1 to 5 mm and a length of about 0.03 to 1 m formed of tungsten, molybdenum, or the like. The length of the wire 14b is determined by the size of the single crystal 36 to be pulled, the thickness and strength of the wire 14b, and the like.

According to the single crystal growing apparatus thus configured, the torsional vibration can be absorbed by the wire 14b interposed between the pulling rod 14a and the seed crystal holding jig 34A. As a result, the shear stress acting on the neck portion 36 is greatly reduced, and safety can be greatly improved.

The basic portion of the lifting shaft 14 is constituted by a lifting rod 14a, and the conventional wire 34b
Since the wire length is very short as compared with the pulling shaft 34 made of, the single crystal 36 does not shake and there is no need to wind up by a drum.
The winding habit does not occur on the lifting shaft 14 and the verticality of the lifting shaft 14 is not hindered, and the wire 14b hardly deteriorates.

In the first embodiment, the wire 14
b shows one configuration interposed between the lifting rod 14a and the seed crystal holding jig 34A. However, the present invention is not limited to this, and in another embodiment, the lifting rod 14a is A plurality of wires 14b may be interposed between the seed crystal holding jig 34A.

<Second Preferred Embodiment> FIG. 2 is an enlarged partial sectional view showing a part of a pulling shaft constituting a single crystal growing apparatus according to a second preferred embodiment. Note that components having the same functions as those of the single crystal growth apparatus according to the first embodiment are denoted by the same reference numerals.

In the drawing, reference numeral 24 denotes a lifting shaft. The upper portion of the lifting shaft 24 is constituted by a lifting rod 14a.
Central portion of bottom surface of pull-up rod 14a and seed crystal holding jig 34A
A wire 14b is interposed between the upper portion and the central portion of the upper surface. An outer cylindrical guide 14c is attached so as to surround the wire 14b from the periphery of the bottom surface of the lifting rod 14a toward the periphery of the upper surface of the seed crystal holding jig 34A.
Pull-up rod 1 from the bottom periphery of seed crystal holding jig 34A
An inner cylindrical guide 14d is attached so as to surround the wire 14b toward the periphery of the upper surface of 4a. A gap 15a having a predetermined size is provided between the seed crystal holding jig 34A and the outer cylindrical guide 14c.
A gap 15b of a predetermined size is provided between the inner cylindrical guide 4d and the inner cylindrical guide 14d. These lifting rods 14a,
The lifting shaft 24 includes the wire 14b, the outer cylindrical guide 14c, and the inner cylindrical guide 14d. Other configurations are the same as those of the single crystal growth apparatus shown in FIG.

Outer cylindrical guide 14c, inner cylindrical guide 1
4d is an outer diameter of 5 formed of SUS, molybdenum, or the like.
~ 300mm, inner diameter 3 ~ 280mm, length 0.03 ~ 1
m is desirable.

By setting the gaps 15a and 15b to about 0.3 to 10 mm, it is desirable that the verticality of the wire 14b be maintained and a state in which the wire 14b can freely move to some extent is guaranteed.

According to the single crystal growing apparatus thus configured, since the wire 14b is substantially covered by the outer cylindrical guide 14c and the inner cylindrical guide 14d, the single crystal 36 is liable to be largely shaken. Even if a force is applied, it is regulated by the outer cylindrical guide 14c and the inner cylindrical guide 14d, and even if a minute amount of dust is generated, it is possible to prevent the dust from adversely affecting the single crystal 36.

Therefore, even when the large single crystal 36 is pulled, the single crystal can be safely removed without lowering the product yield while maintaining the verticality of the pulling shaft 24 without causing the single crystal 36 to sway. Can grow.

[0035]

[Examples and Comparative Examples]

<Embodiment> In the embodiment, the lifting shaft 24 shown in FIG. 2 was manufactured under the following conditions.

Wire 14b: Tungsten, diameter 0.
A wire pulling rod 14a having an outer diameter of 3.75 mmφ and a length of 0.20 m made by further twisting 19 15 mm wires with 19 strands: SUS, diameter 66 mm, length 3.
5m Outer cylindrical guide 14c: SUS, outer diameter 66mm, inner diameter 62mm, length 0.19m gap 15a: 10mm Inner cylindrical guide 14d: SUS, outer diameter 60mm, inner diameter 56mm, length 0.19m gap 15b: The length of the 10 mm wire 14b was determined by the following calculation.

First, for example, when the radius (R) is 0.15
[M], the moment of inertia (I) of a silicon single crystal having a length (h) of 0.2 [m] is

[0038]

I = γπR ⁴ h / 2g [kgf · s ² · m] Here, γ is the density of the silicon single crystal and is 23
00 [kg / m ³ ], g is 9.8 [m / s] in gravitational acceleration
² ]. Therefore,

[0039]

## EQU2 ## I = 3.73 × 10 ⁻² [kgf · s ² · m] Next, the torsional rigidity (k) of the wire is

[0040]

K = Gπr ⁴ / 2LT [kgf · m] Here, G is a transverse elastic modulus of 1.35 × 10 ¹⁰ [k
gf / m ³ ], and r is a wire radius of 1.875 × 10
^-3 [m], L is wire length [m], T is torsion (torsio
nability number) is about 700. Therefore,

[0041]

K = 3.74 × 10 ⁻⁴ L ⁻¹ [kgf · m] Moment of inertia (I) of the above silicon single crystal
And when the torsional rigidity (k) of the wire is used, the torsional vibration cycle (t [s]) is

[0042]

## EQU5 ## Since t = 2π (I / k) ^1/2 [s], Equations 2 and 4 are substituted into Equation 5 to obtain:

[0043]

## EQU6 ## t = 62.7 × L ^1/2 [s]

FIG. 3 is a graph showing the relationship between the wire length (L [m]) and the torsional vibration period (t [s]) obtained by equation (6).

As is apparent from FIG. 3, since the torsional vibration period (t) increases as the wire length (L) increases, the shear stress on the single crystal 36 due to the torsional vibration period increases as the wire length increases. Influence is reduced.

Actually, the problem during the growth of a single crystal is a torsional oscillation period of several seconds or less, which is 10 seconds or less. Therefore, it is considered that the length of the wire 14b needs to be 0.03 m or more. Can be Therefore, in the embodiment, the length of the wire 14b is set to 0.2 m.

Using the single crystal growth apparatus according to the above embodiment,
The operation of growing a single crystal 36 having a diameter of 300 mm, a length of 1.5 m, and a total weight of about 250 kg was performed 20 times using 300 kg of polycrystalline silicon as a single crystal raw material, and observation was performed.

As a result of the above experiment, during all the 20 operations, no torsional vibration, single crystal vibration, etc. were observed during the pulling of the single crystal and at the time of taking out the single crystal. Also,
No damage to the wire 14b was observed even after 20 lifting operations.

<Comparative Example 1> In Comparative Example 1, the pulling rod type pulling shaft shown in FIG. 5 was manufactured under the following conditions.

Lifting rod 34a: SUS, diameter 66m
m, length 3.5 m Using the single crystal growth apparatus equipped with the pulling rod 34 a according to the comparative example 1, the single crystal 3 was used in the same manner as in the example.
6 was grown and observed.

As a result of the above experiment, during all the 20 operations, a torsional vibration having a period of about 2 to 3 seconds occurs during the pulling of a single crystal having a single crystal length of about 0.5 m,
In the six pulling operations out of 20 times, the single crystal 36 was broken from the neck and dropped.

Comparative Example 2 In Comparative Example 2, the wire-type lifting shaft shown in FIG. 6 was manufactured under the following conditions.

Wire 34b: made of tungsten, diameter 3.
Using a single crystal growth apparatus equipped with the wire 34b according to Comparative Example 2 having a length of 75 mm and a length of 3.5 m, a single crystal 36 was grown and observed in the same manner as in the example.

As a result of the above experiment, in seven pulling operations out of 20 times, remarkable single crystal fluctuation occurred during the pulling, and the pulling was interrupted because control became difficult. In addition, the single crystal was shaken when the single crystal was taken out in the four pulling operations out of 20 times, and the single crystal 36 and the chamber came into contact with each other, and the single crystal 36 dropped in the two pulling operations out of four times. Further, after the 18th pulling operation, polysingle crystallization was performed at the time when the single crystal length was 0.5 m or less. In addition, the wire 34b 20 times after the lifting operation
As a result, several strands were broken at several tens of places.

As is apparent from the above results, the load acting on the neck can be greatly reduced in the single crystal growth apparatus according to the embodiment as compared with the single crystal growth apparatus according to the comparative example. Could be greatly improved. Moreover, even a large single crystal could be grown stably, and the product yield could be significantly improved.

[Brief description of the drawings]

FIG. 1 is an enlarged partial cross-sectional view showing a lifting shaft according to an embodiment of the present invention.

FIG. 2 is an enlarged partial sectional view showing a lifting shaft according to another embodiment.

FIG. 3 is a graph showing a relationship between a wire length and a torsional vibration cycle.

FIG. 4 is a schematic cross-sectional view showing a conventional single crystal growth apparatus using the CZ method.

FIG. 5 is a partially enlarged front view showing a lifting rod type lifting shaft.

FIG. 6 is a partially enlarged front view showing a wire-type lifting shaft.

[Description of Signs] 14a Pull-up rod 14b Wire 34A Seed crystal holding jig

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C30B 1/00-35/00

Claims (2)

(57) [Claims] 1. A single crystal growth apparatus, wherein a wire is interposed between a pulling rod for pulling a single crystal and a seed crystal holding jig. 2. The single crystal growth apparatus according to claim 1, wherein a cylindrical guide is provided around the wire.