JPH09235192A - Single crystal ingot low in oxygen concentration and lifting of single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low oxygen concentration single crystal ingot small in the oxygen concentration and having an approximately uniform oxygen concen tration distribution in the growth axis direction, and to provide a single crystal- lifting method for lifting the ingot. SOLUTION: This low oxygen concentration single crystal ingot has an oxygen content concentration of 0.5-1.0×10<18> atoms/cc [when a conversion coefficient (fc) is 4.81 by an IR absorption spectroscopy; hereinafter similarly) and an oxygen concentration distribution of the central value [(maximum oxygen concentration + minimum oxygen concentration)/2]±0.05 atoms/cc in the growth axis direction in the ingot having a growth length of >=1000mm. The characteristics of this method for lifting the single crystal comprises rotating an outer crucible at a rotation speed of 0.05-5rpm, preferably, 0.1-3rpm, and the semiconductor single crystal ingot at a rotation speed of 8-25rpm, preferably 10-15rpm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a single crystal pulling method for pulling a semiconductor single crystal ingot from a semiconductor melt stored by using a crucible having a double structure, and a low oxygen concentration single crystal ingot pulled by this method. Regarding

[0002]

2. Description of the Related Art Conventionally, the CZ method is known as a method for growing a semiconductor single crystal ingot such as silicon (Si) or gallium arsenide (GaAs). That is, this C
In the Z method, a seed crystal is immersed in a semiconductor melt in a crucible in an airtight container, and a semiconductor single crystal ingot is grown with the seed crystal as a nucleus.

However, in the conventional CZ method, turbulent flow due to thermal convection is generated in the semiconductor melt, which increases temperature fluctuations at the solid-liquid interface and promotes remelting and resolidifying phenomena, resulting in a semiconductor single crystal. There are problems such as causing crystal defects in the ingot and causing non-uniform distribution of impurity concentration distribution and oxygen concentration distribution. FIG. 4 is a graph showing an oxygen concentration distribution in the growth axis direction of a 6 ″ φ single crystal grown by the CZ method, and FIG. 5 is an 8 ″ φ single crystal similarly grown by the CZ method.
It is a graph which shows the oxygen concentration of the growth axis direction of a single crystal.

A so-called magnetic field application method (MCZ method) has been developed in which a magnetic field is applied to a semiconductor melt to suppress convection of the melt and suppress temperature fluctuations near the surface of the melt due to convection. However, in the MCZ method, since the ratio of the crucible-semiconductor melt contact area to the semiconductor melt free surface area changes, there is a problem that a non-uniform oxygen concentration distribution occurs in the growth axis direction.

In order to keep the ratio of the crucible-semiconductor melt contact area and the semiconductor melt free surface area substantially constant, the continuous charge type magnetic field applied CZ method (hereinafter referred to as CMC) using a double crucible.
It is abbreviated as Z method. ) Has been proposed. In this CMCZ method, a semiconductor melt is stored in an outer crucible provided inside an airtight container, and an inner crucible that is a cylindrical partition is placed inside the outer crucible to form a double crucible. In this method, a raw material is supplied between the crucible and the inner crucible, a magnetic field is applied to the semiconductor melt in the outer crucible from the outside of the airtight container, and the semiconductor single crystal ingot is pulled up from the inner region of the inner crucible.

[0006]

[Problems to be Solved by the Invention] However, CMC
Even in the Z method, the oxygen concentration distribution may not be uniform in the growth axis direction depending on pulling conditions.

The present invention has been made in view of the above circumstances, and a low oxygen concentration single crystal ingot having a low oxygen concentration and a substantially uniform oxygen concentration distribution in the growth axis direction, and a single crystal for pulling the same. It is an object to provide a crystal pulling method.

[0008]

A low oxygen concentration single crystal ingot according to claim 1 of the present invention has an ingot crystal length of 1
At 000 mm or more, the oxygen content is 0.5 to 1.
In the range of 0 × 10 ¹⁸ atoms / cc (the same applies hereafter when the conversion coefficient f _c = 4.81 in infrared absorption spectroscopy), the oxygen concentration distribution in the growth axis direction has a central value ((oxygen concentration Maximum value + minimum value) / 2) of ± 0.05a
It is toms / cc.

In the method for pulling a single crystal according to the second aspect of the present invention, the semiconductor melt is stored in an outer crucible provided inside an airtight container, and the inner crucible, which is a cylindrical partition, is placed in the outer crucible. To form a double crucible, supply the raw material between the outer crucible and the inner crucible, apply a magnetic field to the semiconductor melt in the outer crucible from the outside of the airtight container, the outer crucible. In the single crystal pulling method of rotating and pulling the semiconductor single crystal ingot from the inner region of the inner crucible by rotating around the growth axis direction, the rotation speed of the outer crucible is 0.05 to 5 rpm, and the semiconductor single crystal ingot is rotated. The rotation speed of is set to 8 to 25 rpm.

A single crystal pulling method according to a third aspect of the present invention is the single crystal pulling method according to the second aspect, wherein the rotation speed of the outer crucible is 0.1 to 3 rpm, and the semiconductor single crystal ingot is rotated. It is characterized in that the speed is 10 to 15 rpm.

[0011]

By rotating the outer crucible and the semiconductor single crystal ingot, the oxygen concentration in the ingot can be kept low and the oxygen concentration can be kept uniform.

The rotation speed of the outer crucible is 0.05 rpm or more because if the rotation speed is less than that, the single crystallization rate decreases, and the rotation speed of the outer crucible is 5 rpm or less.
This is because if it exceeds that, the uniformity of oxygen concentration cannot be maintained.

The rotation speed of the semiconductor single crystal ingot is 8r.
If it is less than pm, the in-plane distribution of the oxygen concentration becomes worse if it is less than pm, and if the rotation speed of the semiconductor single crystal ingot is 25 rpm or less, the rate of single crystallization decreases if it exceeds it. Is.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A silicon single crystal pulling method according to an embodiment of the present invention will be described below.

The single crystal pulling apparatus 1 used in the present single crystal pulling method has, as shown in FIG.
A double crucible 3, a heater 4, and a raw material supply pipe 5 are arranged. The double crucible 3 is formed of a substantially hemispherical outer crucible 11 made of quartz and an inner crucible 12 made of quartz which is a cylindrical partition provided in the outer crucible 11, and a side wall of the inner crucible 12. A communication portion 12a that communicates the outer region and the inner region of the inner crucible 12 is formed in the lower portion.

The double crucible 3 is mounted on a susceptor 15 on a shaft 14 which is vertically erected in the lower center of the chamber 2 and rotates about the axis of the shaft 14 in a horizontal plane at a predetermined rotation speed described later. It is designed to be driven. In the double crucible 3, a semiconductor melt (raw material for a semiconductor single crystal that has been heated and melted) 21 is stored. The heater 4 heats and melts the semiconductor raw material in the outer crucible 11 and, at the same time, melts the semiconductor melt 2
It is for keeping 1 warm. The heater 4 is arranged so as to surround the susceptor 15 and the double crucible 3, and an electromagnet 6 that gives a magnetic field to the semiconductor melt 21 in the outer crucible 11 is arranged outside the heater 4.

The raw material supply pipe 5 is for continuously supplying the granular raw material 22 to the semiconductor melt 21 on the liquid surface 23 of the semiconductor melt 21 between the outer crucible 11 and the inner crucible 12. is there. Examples of the raw material to be charged from the raw material supply pipe 5 include polycrystalline silicon ingots crushed by a crusher or the like into flakes, or polycrystalline silicon deposited in a granular form from a gas raw material by a thermal decomposition method. Granules and the like, and if necessary, additional elements called dopants such as boron (B) and phosphorus (P) are further added. The same applies to the case of gallium arsenide, in which case the additive element is zinc (Zn), silicon (Si), or the like.

An upper part of the chamfer 2 is provided with a pulling mechanism and an inlet for introducing an inert gas such as argon gas (Ar) into the chamfer 2. The pulling wire 24, which is a part of the pulling mechanism, is configured to move up and down while rotating at a predetermined rotation speed described below above the double crucible. A seed crystal 25 of a semiconductor single crystal is attached to the tip of the pulling wire 24 via a chuck. And
The seed crystal 25 is immersed in the semiconductor melt 21 in the inner region of the inner crucible 12 and then raised, and the semiconductor single crystals 26 sequentially grown with the seed crystal 25 as a starting point are argon gas (Ar).
Etc. in an inert gas atmosphere.

The raw material supply pipe 5 is charged with the raw material from the upper end,
The material is discharged from the lower end opening 5a, the upper end side is supported and hung down, and the lower end opening 5a is located at a position closer to the peripheral wall of the outer crucible 11. The raw material supply pipe 5 is composed of a quartz pipe having a rectangular cross section from the viewpoint of preventing contamination and workability.

As described above, the shaft 14 is driven to rotate, whereby the outer crucible 11 is rotated in the horizontal plane, and the pulling wire 24 is rotated about its axis. The rotation directions of the shaft 14 and the pulling wire 24 are opposite to each other. Here, the rotation speed of the outer crucible 11 is 0.05 to 5 rpm, and the rotation speed of the pulling wire 24, that is, the semiconductor single crystal ingot 26 is 8 rpm.
~ 25 rpm. Preferably, the outer crucible 1
The rotation speed of 1 is 0.1 to 3 rpm, and the rotation speed of the semiconductor single crystal ingot is 10 to 15 rpm.

As a result, by rotating the outer crucible 11 and the semiconductor single crystal ingot 26, the oxygen concentration in the ingot can be suppressed low and the oxygen concentration can be kept uniform. The rotation speed of the outer crucible is 0.0
It is 5 rpm or more because if it is less than that, the single crystallization rate is lowered, and the rotation speed of the outer crucible is 5 rpm or less because if it exceeds that, the uniformity of oxygen concentration cannot be maintained. . Further, the reason why the rotation speed of the semiconductor single crystal ingot is 8 rpm or more is that the in-plane distribution of the oxygen concentration becomes worse below that, and the rotation speed of the semiconductor single crystal ingot is 25 rpm or less. This is because the single crystallization rate decreases if it exceeds.

[0022]

EXAMPLE A method for pulling a silicon single crystal according to an example of the present invention will be described.

FIG. 1 shows the oxygen concentration distribution in the growth axis direction of a 6 ″ φ silicon single crystal ingot pulled by the single crystal pulling method of one embodiment of the present invention. In FIG. ◯ indicates Example 2, and □ indicates a comparative example.

In Example 1, the rotation speed of the outer crucible 11 was 0.5 rpm, the rotation speed of the semiconductor single crystal ingot 26 was 12 rpm, and the applied magnetic field was 0.3 t.
esla, the internal pressure in the closed container is 10 torr, and the argon gas flow rate is 30 to 60 l / min.

In the second embodiment, the rotation speed of the outer crucible 11 is 2
rpm, the rotation speed of the semiconductor single crystal ingot 26 is 12
rpm, the applied magnetic field is 0.3 tesla, the internal pressure in the closed container is 10 torr, and the argon gas flow rate is 30 to 60 l / min.

In the comparative example, the rotation speed of the outer crucible 11 is 8r.
pm, the rotation speed of the semiconductor single crystal ingot 26 is 12 r
pm, the applied magnetic field is 0.3 tesla, the internal pressure in the closed container is 10 torr, and the argon gas flow rate is 80 l / min.

FIG. 2 shows crystal lengths of the semiconductor single crystal ingot obtained in Example 2 of 200 mm, 1000 mm, 1
The oxygen concentration distribution of a cross section of 800 mm is shown. OR in the figure
G indicates the oxygen concentration fluctuation rate in the radial direction, and is ((O
Represented by _{C -O P) / O C)} × 100. O _C is the oxygen concentration at the center of the wafer, and O _P is the oxygen concentration 5 mm from the wafer edge.

1 and 2, according to Examples 1 and 2, when the crystal length of the semiconductor single crystal ingot is 1000 mm or more, the oxygen content is 0.5 to 1.0 × 10 ¹⁸ a.
Within the range of toms / cc, the oxygen concentration distribution in the growth axis direction is the central value ((maximum oxygen concentration + minimum value) / 2)
It can be seen that it is ± 0.05 atoms / cc. That is, it is found that the oxygen content is low in the crystal length direction and the uniformity of the concentration is maintained.

FIG. 3 is a graph showing the relationship between the strength of the magnetic field and the oxygen concentration, showing the results of experiments conducted under the conditions of 6 "φ crystal, outer crucible rotation speed of 5 rpm, and crystal rotation speed of 12 rpm. According to Fig. 3, 0.3 tes
If a magnetic field of la or more is applied, the oxygen concentration becomes 1.0 × 10
^It can be seen that it becomes ¹⁸ atoms / cc or less.

[0030]

As described above, according to the low oxygen concentration single crystal ingot of the present invention, the low oxygen concentration single crystal ingot according to claim 1 of the present invention has an ingot crystal length of 1
At 000 mm or more, the oxygen content is 0.5 to 1.
Within the range of 0 × 10 ¹⁸ atoms / cc, the oxygen concentration distribution in the growth axis direction is ± 0.05 atoms / cc with respect to the central value ((maximum value of oxygen concentration + minimum value) / 2).

In the method for pulling a single crystal according to claim 2, the semiconductor melt is stored in an outer crucible provided inside an airtight container,
A double crucible is formed by placing an inner crucible, which is a cylindrical partition, in this outer crucible, supplying a raw material between the outer crucible and the inner crucible, and from the outside of the hermetic container to the inside of the outer crucible. Applying a magnetic field to the semiconductor melt, while rotating the outer crucible, in the single crystal pulling method of pulling the semiconductor single crystal ingot from the inner region of the inner crucible while rotating around the axial direction, in the outer crucible, Rotation speed is 0.
Since the rotation speed of the semiconductor single crystal ingot was set to 05 to 5 rpm and the rotation speed of the semiconductor single crystal ingot was set to 8 to 25 rpm, the rotation of the outer crucible and the semiconductor single crystal ingot caused the forced convection in the semiconductor melt in a direction to cancel the natural convection. While keeping the oxygen concentration in the crystal ingot low,
It is possible to ensure the uniformity of oxygen concentration.

A single crystal pulling method according to a third aspect of the present invention is the single crystal pulling method according to the second aspect, wherein the rotation speed of the outer crucible is 0.1 to 3 rpm and the semiconductor single crystal ingot is rotated. Since the speed is 10 to 15 rpm,
The controllability of the oxygen concentration can be further enhanced.

[Brief description of drawings]

FIG. 1 is a graph showing an oxygen concentration distribution in the growth axis direction of an example of the present invention.

FIG. 2 is a graph showing an oxygen concentration distribution in a radial direction of a single crystal according to an example of the present invention.

FIG. 3 is a graph showing the relationship between magnetic field strength and oxygen concentration.

FIG. 4 is a graph showing an oxygen concentration distribution of a single crystal by a conventional CZ method.

FIG. 5 is a graph showing an oxygen concentration distribution of a single crystal by a conventional CZ method.

FIG. 6 is a schematic view showing a single crystal pulling apparatus to which the single crystal pulling method of the present invention is applied.

[Explanation of symbols]

 2 Champa (airtight container) 3 Double crucible 4 Heater 5 Raw material supply pipe 6 Electromagnet 11 Outer crucible 12 Inner crucible 12a Communication part 14 Shaft 15 Susceptor 21 Semiconductor melt 24 Pulling wire 26 Semiconductor single crystal ingot

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisashi Furuya 1-5-1, Otemachi, Chiyoda-ku, Tokyo Sanritsu Material Silicon Co., Ltd. (72) Inventor Michio Kita 1-297 Kitabukuro-cho, Omiya-shi, Saitama Address Mitsubishi Materials Corporation, Research Institute

Claims (3)

[Claims] 1. An ingot having a crystal length of 1000 mm or more and an oxygen concentration of 0.5 to 1.0 × 10 ¹⁸ ato.
ms / cc (conversion coefficient f _c = in infrared absorption spectroscopy
The same applies to the case of 4.81), and the oxygen concentration distribution in the growth axis direction is ± 0.05 atoms / cc with respect to the central value ((maximum oxygen concentration + minimum value) / 2).
A low-oxygen concentration single crystal ingot characterized by: 2. A semiconductor melt is stored in an outer crucible provided inside an airtight container, and an inner crucible, which is a cylindrical partition, is placed inside the outer crucible to form a double crucible. A raw material is supplied between the crucible and the inner crucible, a magnetic field is applied to the semiconductor melt in the outer crucible from the outside of the airtight container, while rotating the outer crucible, the semiconductor single unit is supplied from the inner region of the inner crucible. In the single crystal pulling-up method of pulling the crystal ingot while rotating it around the growth axis direction, the rotation speed of the outer crucible is 0.05 to 5 rpm, and the rotation speed of the semiconductor single crystal ingot is 8 to 25 rpm. Method for pulling single crystal. 3. The rotation speed of the outer crucible is 0.1 to 3r.
pm and the rotation speed of the semiconductor single crystal ingot is 10 to 10.
The single crystal pulling method according to claim 2, wherein the method is 15 rpm.