JPH05294784A - Single crystal growth device - Google Patents

Abstract

(57) [Summary] [Construction] A single crystal growth apparatus in which a cylindrical heat insulating material 17 is arranged around a heat shield jig 19 having an inverted truncated cone shape. [Effect] Since the heat insulating material 17 is disposed around the heat shielding jig 19, the temperature of the heat shielding jig 19 can be raised, and the position where SiO cools and adheres to the heat shielding jig 19. Can be removed above the outside of the crucible 1. Therefore, it is possible to suppress SiO from falling into the crucible 1, and it is possible to obtain a single crystal in which DF breakage is suppressed and crystal defects are small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal growth apparatus for growing a silicon single crystal used as a semiconductor material, for example.

[0002]

2. Description of the Related Art There are various methods for growing a crystal, one of which is the Czochralski method (hereinafter referred to as the CZ method). FIG. 6 is a schematic cross-sectional view of a crystal growth apparatus used in the CZ method, in which 1 indicates a crucible. The crucible 1 is composed of an inner layer container 1a and an outer layer container 1b, and a bottomed cylindrical quartz outer layer holding container 1b is fitted on the outer side of the quartz inner layer container 1a. Has been done. The crucible 1 is supported by a support shaft 7, and the support shaft 7 rotates in the direction of the arrow in the drawing at a predetermined speed and moves up and down. A heater 2 is arranged in a concentric cylindrical shape outside the crucible 1, and heat insulating cylinders 3 and 4 made of graphite are arranged in a concentric cylindrical shape outside the heater 2. Crucible 1
The crystallization raw material charged inside is melted by the heater 2 to form a melt 13 and is filled in the crucible 1. On the central axis of the crucible 1, a pulling shaft 5 made of wire or the like is provided.
The pull-up shaft 5 is adapted to rotate at a predetermined speed in the same or opposite direction to the rotation direction of the support shaft 7.
A seed crystal 6 is attached to the lower end of the pull-up shaft 5, and the melt 1
3 is solidified to grow the single crystal 12a.

Generally, in order to adjust the electric resistance and electric conductivity type of the single crystal 12a, impurities are often added to the melt 13 in advance (hereinafter referred to as doping). During the growth of the single crystal 12a, the single crystal 12a and the melt 1
When the impurity concentration in the single crystal 12a is C _S and the impurity concentration in the melt 13 is C _{L at} the interface where 3 and 3 contact, C _S / C _L (Ke: effective segregation coefficient) is the same as that of the melt 13 It is known to take a value peculiar to impurities. For example, when silicon (hereinafter referred to as Si) is doped with a phosphorus impurity, the Ke is 0.35 (“Si single crystal and doping” P35: Maruzen). Therefore, in the CZ method, as the single crystal 12a is pulled up, the melt 13
The impurity concentration in the inside is concentrated, and accordingly, the impurity concentration in the single crystal 12a pulled up gradually increases. Therefore, the impurities in the single crystal 12a segregate along the crystal pulling direction, and as a result, there is a problem in that the electrical characteristics in the single crystal 12a become nonuniform along the crystal growth direction.

A melt layer method is known as a method of growing a crystal while suppressing the segregation of the impurities. As shown in FIG. 7, the melting layer method is performed by melting only the upper portion of the crystallization raw material in the crucible 1 having the same structure as that shown in FIG. A melt 13 layer is formed on the bottom, and a solid layer 14 is formed on the bottom.
This is a method of growing the single crystal 12b by controlling the volume of the melt 13 layer so that the impurity concentration in 3 is always constant.

[0005] inner container 1a in the CZ method and a melt layer method is formed by SiO _2, oxygen of the SiO ₂ was eluted in the melt 13, most of which dissolved out oxygen is turned SiO Evaporates from the surface of the melt 13, but some oxygen dissolves in the single crystals 12a and 12b. Generally, the oxygen concentration in the single crystals 12a and 12b is adjusted by changing the rotational speeds of the crucible 1 and the pulling shaft 5, and in the CZ method, it is 12 to 17 × 10 ¹⁷ depending on the purpose of use.
An oxygen concentration of about / cm ³ is included.

However, in the above-mentioned melt layer method, since the solid layer 14 is provided, the amount of the melt liquid 13 is reduced, and the melt liquid 1
The area where 3 contacts the inner layer container 1a is reduced to about half of that in the CZ method. Therefore, the melt layer method has a problem that the supply amount of oxygen itself to the melt 13 is small and it is difficult to obtain the single crystal 12b having a high oxygen concentration.

Single crystal having a high oxygen concentration by the melt layer method 1
As a method for growing 2b, the present applicant has previously proposed a method using a heat shield jig (Japanese Patent Application No. 3-46347).
issue). FIG. 8 is a schematic cross-sectional view showing a main part of a crystal growth apparatus used in the above method, in which 1 indicates a crucible. A pulling shaft 5 is arranged on the central axis of the crucible 1, and a single crystal 12b is formed at the lower end of the pulling shaft 5. Further, an inverted truncated cone-shaped heat shield jig 19 is arranged above the crucible 1 concentrically with the crucible 1, and the lower end portion 19 a of the jig is arranged near the upper surface of the melt 13. When the single crystal 12b is grown using the above apparatus, the radiant heat radiated by the crucible 1 heated by the heater 2 is cut off by the heat shield jig 19, and the jig lower end portion 19a is formed.
In the region from the center to the central axis (indicated by A in the figure, hereinafter referred to as A region), the temperature of the surface of the melt 13 is reduced, and evaporation of SiO from the melt 13 is suppressed, resulting in a high oxygen concentration. A single crystal 12 having is obtained.

Another method (Japanese Patent Publication No. 57-40119) using a heat shield jig having an inverted truncated cone shape has been proposed. In this method, the pulling rate of a single crystal is increased,
It is also intended to prevent the condensate attached to the pulling zone and the refilling device from falling and causing crystal defects.

[0009]

In the single crystal growth apparatus using the heat shield jig 19 shown in FIG. 8 as well, the region from the jig lower end portion 19a to the inner wall of the crucible (indicated by B in the figure. In the region), the surface of the melt 13 is at a high temperature, and some oxygen becomes SiO and evaporates from the surface of the melt 13. Further, as shown in FIG. 8, argon gas (hereinafter referred to as Ar) flows into the single crystal growth apparatus from the upper part of the apparatus and flows in the path indicated by the arrow. Therefore, the SiO evaporated from the surface of the melt 13 is carried by the Ar and cooled in the middle to be powdery, and a part of the powder adheres to the lower surface of the inverted truncated cone of the heat shield jig 19. When the SiO adheres to the area B of the heat shield jig 19 and then falls into the crucible 1 and enters the melt 13, it mixes into the pulled single crystal 12b and makes that portion polycrystalline.
Causes F (Dislocation Free) outage. as a result,
The single crystal 12b mixed with SiO has many defects such as crystal grain boundaries and dislocations, which makes it unusable for devices.

Further, in the crystal growth apparatus using the heat shield jig described in the above publication, the heat shield jig suppresses the condensate attached to the pulling zone and the refilling device from dropping into the crucible. However, as in the case shown in FIG. 8, there is a problem that it is impossible to prevent SiO from adhering to the lower surface of the inverted truncated cone of the heat shield jig and dropping into the crucible.

The present invention has been made in view of the above problems, and in a single crystal growth apparatus using a heat shield jig, when pulling a single crystal, S attached to the heat shield jig is pulled.
It is an object of the present invention to provide a single crystal growth apparatus capable of suppressing DF breakage due to iO falling into a melt.

[0012]

In order to achieve the above object, a single crystal growth apparatus according to the present invention comprises a crucible containing a raw material and a heater arranged around the crucible,
In a single crystal growth apparatus in which an inverted frustoconical heat shield jig whose tip portion is located above and above the melt surface in the crucible is provided, a cylindrical heat insulating material is provided around the heat shield jig. Is provided.

[0013]

In the apparatus shown in FIG. 8, the powdery Si
If O adheres to the inner diameter outside portion (indicated by C in the figure, hereinafter referred to as C region) of the inner layer container 1a in the heat shielding jig 19, the SiO is prevented from falling into the crucible 1. ..

On the other hand, regarding the temperature at which SiO sublimes,
It is empirically known that the temperature is around 1000 ° C. Therefore, the temperature of the B region of the heat shield jig 19 is 1000 ° C.
If kept above, it is possible to prevent the powdery SiO from adhering to the region B of the heat shield jig 19, and thus the SiO crucible 1
It is suppressed that it falls inside.

To raise the temperature of the heat shield jig 19, various methods such as increasing the heater power can be considered. However, when the heater power is increased, the temperature of the melt 13 rises, a predetermined crystal diameter cannot be obtained, and there is a possibility that the single crystal cannot be grown.
It is necessary that the crystal growth conditions near the interface of 2b are not significantly changed.

The heat shield jig 19 dissipates heat mainly from the furnace wall 2.
By heat transfer to 0 and Ar. Therefore, it is considered that the temperature of the heat shield jig 19 can be increased by reducing the heat radiation to the furnace wall 20 by providing a heat insulating structure near the jig support portion 19b.

Therefore, a heat insulating material was arranged around the jig supporting portion 19b, and heat transfer analysis was conducted on the influence on the temperature of the heat shielding jig. FIG. 2 is a schematic partial cross-sectional view showing the device used for the heat transfer analysis, and shows only the right half from the center line of the device. In the figure, 19 is a heat shield jig,
The heat shield jig 19 is made of graphite in an inverted truncated cone shape, and its dimensions are 240 m inside diameter of the jig lower end portion 19a.
m, inner diameter of upper end 420 mm, height 350 mm, thickness 1
It is 0 mm. A heat insulating material 17 is provided around the jig supporting portion 19b.
And the heat insulating material 17 is made of carbon felt in a cylindrical shape, and the dimensions are 800 mm in diameter and 120 mm in thickness, and the height is 80, 160, 240 mm.
3 types are used respectively.

FIG. 3 shows the use of the above apparatus for heat transfer analysis,
It is a graph which shows the result of having compared the temperature distribution of the heat-shielding jig 19 by changing the height of the heat insulating material 17, the height of the heat insulating material 17 is 80 mm in the figure, the triangle mark is 160 mm, and the square mark is 240 mm. The case of each is shown.

As is apparent from FIG. 3, the heat shield jig 1
The temperature of 9 is higher as it is closer to the jig lower end portion 19a, and when the heat insulating material 17 is raised, the temperature range of 1000 ° C. or higher is expanded toward the upper end of the heat shielding jig 19 (B region to C region). ..

According to the single crystal growth apparatus of the present invention, since the cylindrical heat insulating material is arranged around the heat shield jig, heat radiation of the heat shield jig is suppressed, and B in the heat shield jig is suppressed. It is suppressed that the temperature of the area rises and SiO is attached to the area B of the heat shield jig, and as a result, the SiO is prevented from falling into the crucible.

[0021]

EXAMPLES AND COMPARATIVE EXAMPLES Examples and comparative examples of a single crystal growth apparatus according to the present invention will be described below with reference to the drawings. It should be noted that the same reference numerals are given to the components having the same functions as those of the conventional example.

FIG. 1 is a cross-sectional view showing a single crystal growth apparatus according to an embodiment, in which 1 is a crucible. The crucible 1 is composed of an inner layer container 1a and an outer layer container 1b,
A bottomed cylindrical quartz outer layer holding container 1b is fitted on the outside of a bottomed cylindrical quartz inner layer container 1a. The crucible 1 is supported by a support shaft 7, and the support shaft 7 is configured to rotate at a predetermined speed in the direction of the arrow in the drawing and to move up and down. A heater 2 is arranged in a concentric cylindrical shape outside the crucible 1, and a graphite heat insulating cylinder 3 is arranged in a concentric cylindrical shape outside the heater 2. Above the crucible 1, a heat shield jig 19 having an inverted truncated cone shape (made of graphite, the jig lower end portion 19a has an inner diameter of 240 mm, and the upper end portion has an inner diameter of 420 mm).
mm, height 350 mm, thickness 10 mm) are provided, and the jig lower end portion 19a of the heat shield jig 19 is the melt 13
It is located near the top of the surface. In addition, the jig support portion 19
Around the b, a cylindrical heat insulating material 17 (made of carbon felt, diameter 800 mm, thickness 120 mm, height 160 m
m) is provided. A predetermined weight of the crystal raw material charged in the crucible 1 is melted only by the heater 2,
The volume of the melt 13 layer is controlled so that the concentration of the impurities is always a predetermined value. A pull-up shaft 5 made of a wire or the like is arranged on the central axis of the crucible 1, and the pull-up shaft 5 is rotated at a predetermined speed in the same direction as or opposite to the rotation direction of the support shaft 7, and at the lower end of the pull-up shaft 5. Is equipped with a seed crystal (not shown) and melts the seed crystal 1
The molten liquid 13 is solidified by bringing the melt 13 into contact with the surface of the single crystal 3 and pulling it while rotating the pulling shaft 5.
It is designed to grow 2b.

Polycrystalline silicon was melted by using the above-mentioned single crystal growth apparatus or the single crystal growth apparatus shown in FIG. 8 as a comparative example, and phosphorus having a Ke of 0.35 with respect to the raw material was used as an impurity. Pull up the crystal by the layer method,
Fifty batches of single crystals 12b each having a length of 1200 mm were grown. Table 1 shows the pulling conditions.

[0024]

[Table 1]

FIG. 4 shows the single crystal 1 when DF breakage occurred when the single crystal growth apparatus of the present example and the comparative example were used.
It is a bar graph showing the length of 2b and its frequency, where the dotted marks indicate the examples and the shaded marks indicate the comparative examples. As is clear from FIG. 4, the frequency of DF breakage was 34 batches when the device according to the comparative example was used, but decreased to 9 batches when the device according to the example was used.

FIG. 5 is a result of observing the heat shielding jig 19 in the example and the comparative example after completion of pulling the single crystal, and shows the relationship between the position where SiO adheres to the heat shielding jig 19 and the position of the crucible 1. It is a schematic partial cross-sectional view showing.
As is clear from FIG. 5, in the case of the comparative example, SiO adheres to the upper inside (region B) of the inner layer container 1a, but in the case of the example, it adheres to the upper outside (region C) of the inner layer container 1a. ..

As is clear from this result, by insulating the heat shield jig 19, the temperature of the heat shield jig 19 rises and the position where SiO adheres to the heat shield jig 19 is C.
It was confirmed that the SiO was prevented from falling out of the region, and thus the SiO fell into the crucible 1 to prevent DF breakage.

The heat insulating material 17 has a heat insulating effect and can be made of any material as long as it does not pollute the apparatus, such as ceramic wool, which hinders observation inside the furnace. It was confirmed that the larger the height, the better as long as it is within the range, and that a cylindrical shape is preferable in order to make the temperature distribution in the apparatus uniform.

[0029]

As described in detail above, in the single crystal growth apparatus according to the present invention, since the heat insulating material is arranged around the heat shielding jig, the temperature of the heat shielding jig is It is possible to prevent the position where the SiO rises and adheres to the heat shielding jig from being dislocated outside the upper part of the crucible and thus the SiO falls into the crucible, and to prevent the DF breakage.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an embodiment of a crystal growth apparatus according to the present invention.

FIG. 2 is a schematic partial cross-sectional view showing an apparatus used for heat transfer analysis according to the present invention.

FIG. 3 is a graph showing a temperature distribution of a heat shield jig with a change in height of a heat insulating material.

FIG. 4 is a bar graph showing the single crystal length and the frequency when DF breakage occurs in the case of using the single crystal growth apparatus according to the example and the comparative example.

FIG. 5 is a schematic partial cross-sectional view showing the relationship between the position where SiO is attached to the heat shield jig and the position of the crucible when the single crystal growth apparatuses according to the example and the comparative example are used.

FIG. 6 is a schematic cross-sectional view showing a main part of a single crystal growth apparatus used in a conventional CZ method.

FIG. 7 is a schematic cross-sectional view showing a main part of a single crystal growth apparatus used in a conventional melt layer method.

FIG. 8 is a schematic sectional view showing a main part of a single crystal growth apparatus using a heat shield jig.

[Explanation of symbols]

 1 Crucible 2 Heater 13 Melt Liquid 17 Heat Insulating Material 19 Heat Shield Jig 19a Jig Lower End

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Kubo 4-53-3 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. (72) Inventor Shuichi Inami 4-chome, Kitahama, Chuo-ku, Osaka City, Osaka Prefecture No. 5 33 Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1. An inverted frustoconical thermal shield having a crucible containing a raw material, a heater disposed around the crucible, and the like, the lower end of which is located in the vicinity of and above the melt surface in the crucible. A single crystal growing apparatus in which a tool is provided, wherein a cylindrical heat insulating material is provided around the heat shielding jig.