JP3518565B2 - Melting method of polycrystalline silicon - 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 melting polycrystalline silicon when growing a silicon single crystal by the Czochralski method (CZ method). More specifically, a lump or a granular material made of polycrystalline silicon is put in a crucible,
The present invention relates to a method for melting polycrystalline silicon in which a crucible is heated to melt its lumps or particles.

[0002]

2. Description of the Related Art Conventionally, a Czochralski method (hereinafter referred to as CZ method) for growing a high-purity silicon single crystal for a semiconductor from a silicon melt in a crucible is known as a method for growing a silicon single crystal. In this method, the seed crystal is brought into contact with the silicon melt, the seed crystal is pulled up to form a seed throttle part from the silicon melt, and then the crystal is gradually grown to the diameter of the target silicon rod and grown. Thus, it is possible to obtain a dislocation-free single crystal ingot having a necessary plane direction. The silicon melt is melted in the crucible, and the crucible is heated by the heater.

However, the melting temperature of polycrystalline silicon is about 14
The temperature is 00 ° C., and it takes a relatively long time to completely melt the lumps or particles filled in the crucible.
In particular, a relatively large amount of silicon melt is required with the increase in the diameter and length of the single crystal to be pulled today, and the time for melting this polycrystalline silicon causes a problem of lower efficiency in the silicon single crystal ingot growing process. Was there. In order to solve this point, there has been proposed a device in which an infrared reflection plate is provided in the upper part of the crucible except for the passing part of the pulled silicon single crystal ingot (for example, Japanese Patent Publication No. 57-4).
0119, Japanese Patent Publication 6-33218). In these devices, the crucible surrounded by the infrared reflecting plate can be efficiently heated by the heater, and the melting time of the lumps or granules of polycrystalline silicon placed in the crucible can be shortened.

[0004]

However, in the above-mentioned apparatus, since the infrared reflecting plate is not provided at the passage portion of the single crystal ingot to be pulled up, lumps or granules are generated by the emission of heat from the passage portion. There was a problem that the melting time could not be sufficiently shortened. Further, when the infrared reflection plate is provided up to the entire upper part of the crucible, the infrared reflection plate interferes with the pulling up of the single crystal ingot, so that the reflection plate is removed after the lumps or particles are melted. There was still a problem that had to be solved, because it was necessary to take it out from the furnace body, and the labor of taking out the reflector was increased. An object of the present invention is to provide a method for melting polycrystalline silicon, which can easily and further shorten the melting time of a lump or granular material made of polycrystalline silicon.

[0005]

According to the present invention, as shown in FIGS. 1 to 6, lumps or grains 2 made of polycrystalline silicon are used.
No. 4 is put in the crucible 17, and the crucible 17 is heated to melt the lumps or particles 24. Its characteristic configuration is that one or more silicon wafers 26, 36, 46 are provided on or above the lumps or particles 24 made of polycrystalline silicon in the crucible 17.
Is to place. As shown in FIG. 4 or FIG.
Alternatively, two or more silicon wafers 36, 46 are formed with hooking holes 36a, 46a at their centers, and seed crystals 21, 31 made of a silicon single crystal suspended above the crucible 17 are formed.
Locking portions 21a and 31a are formed at the tips of the locking holes 21a and 31a of the silicon wafers 36 and 46, respectively.
It is also possible to hold the silicon wafers 36 and 46 horizontally so as to cover a part of the opening of the crucible 17 above the crucible 17 by hooking onto the a and 31a.

The silicon wafers 26, 36, 46 are preferably mirror-polished or mirror-etched wafers. Mirror-polished or mirror-etched wafers are preferred silicon wafers 2
This is because the reflectance of the surfaces of 6, 36 and 46 is improved,
The reflectance is the ratio of infrared rays reflected by the surface, and the sum of the absorptance indicating the rate of absorption of infrared rays into the object and the transmittance indicating the rate of transmission of infrared rays is 1, that is, 1. Is to have. Therefore, when the reflectance is improved, the amount of infrared rays reflected by the surface of the object is large.

The silicon wafer 26 placed on the upper surface of the lumps or particles 24 made of polycrystalline silicon is preferably melted together with the lumps or particles made of polycrystalline silicon. Further, the silicon wafers 36 and 46 hooked at the tips of the seed crystals 21 and 31 may be obtained by melting a lump or a granular material made of polycrystalline silicon into a silicon melt, and then melting the melt in the melt. preferable. By melting the silicon wafers 26, 36, 46 in the silicon melt, the work of taking out from the furnace body in a later step becomes unnecessary. A silicon wafer 2 containing the same dopant as the dopant contained in the silicon single crystal ingot grown by the silicon wafers 26, 36, and 46.
When the content in 6, 36, 46 is set to an amount necessary to bring the above silicon single crystal ingot to a required dopant concentration or less, the dopant which has been conventionally set in the crucible together with polycrystalline silicon is added. The need can be eliminated or reduced.

[0008]

The silicon wafers 26, 36 and 46 are arranged on the upper surface or above the lumps or particles 24. The crucible 17 is heated by the heat of the heater 13 arranged around the crucible 17.
Agglomerates or particles made of polycrystalline silicon from around
Melting of 4 begins. As shown by the solid arrows in FIGS. 1 and 3, the diffusion of heat released from the upper surface of the crucible 17 of the polycrystalline silicon, which has started melting, is caused by diffusion of the silicon wafers 26, 3
6, 46 prevent and reflect this heat towards the lumps or particles 24. If the infrared reflecting plate 23 is provided in the upper part of the crucible 17 excluding the passage part of the silicon single crystal ingot to be pulled up, as shown in FIG. 6, the diffusion of heat emitted from the upper surface of the crucible 17 where melting has started can be prevented. 26, 36, 46 and prevent more effectively.

The reflectance of the silicon wafers 26, 36, 46 is improved or a plurality of silicon wafers 26, 3 are provided.
By stacking 6, 46, infrared rays and the like emitted from the upper surface of the crucible 17 are reflected again in the crucible 17, so that the amount of heat diffusion prevention per unit area of the silicon wafers 26, 36, 46 is improved. The reflected infrared rays heat the polycrystalline silicon. Silicon wafer 26, 36, 4
6 is melted together with the lumps or granules 24, or is melted in the melt after the lumps or granules 24 are melted, thereby eliminating the need to take out the silicon wafers 26, 36, 46 from the furnace body. Become. Silicon wafer 26,
By including the dopant in 36 and 46, it becomes unnecessary to add another dopant into the crucible, or the amount to be added can be reduced.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. <Example 1> As shown in FIG. 6, in a growth apparatus for growing a single crystal from a silicon melt by the CZ method, a furnace body 1 was used.
A heat insulating material 12 and a heater 13 are arranged concentrically with the furnace body 11 inside 1, and a bottomed cylindrical quartz crucible 17 is fitted to a graphite susceptor 16 fixed to the upper end of a rotary shaft 14 at the center of the furnace body 11. Are combined. A rotating / pulling mechanism 18 is provided above the furnace body 11, and a seed crystal 21 is arranged above the crucible 17 in a holder 19 a suspended from the rotating / pulling mechanism 18 via a wire 19. The rotation / pulling mechanism 18 pulls up the high-purity silicon single crystal ingot grown from the seed crystal 21 while rotating it to grow the high-purity silicon single crystal ingot at the lower end of the seed crystal 21. At the upper edge of the heat insulating material 12, a disk-shaped infrared reflecting plate 23 is arranged inwardly so as to surround the upper portions of the crucible 17 and the heater 13, and the infrared reflecting plate 23 is provided.
A hole 23a slightly larger than the outer shape of the pulled single crystal ingot is provided at the center of the pulled single crystal ingot so as not to contact the pulled single crystal ingot. As shown in FIGS. 1 and 2, in this example, a plurality of silicon wafers 26 are arranged on the upper surface of the granular material 24 made of polycrystalline silicon in the crucible 17. The silicon wafer 26 has a thickness of 1.0 mm and a diameter of 200 mm, and the surface in contact with the granular material 24 is mirror-etched. Sixteen silicon wafers are used on the upper surface of the granular material 24 so as to cover the entire upper surface of the crucible 17 as much as possible.

<Embodiment 2> As shown in FIGS. 3 and 4,
In this example, a hook hole 36a is formed in the center of one silicon wafer 36, and the tip of a square columnar seed crystal 21 made of a silicon single crystal suspended above a crucible 17 of the same size and size as in Example 1. An engaging portion 21a is formed on the silicon wafer 36, and the hooking hole 36a of the silicon wafer 36 is hooked on the engaging portion 21a to horizontally hold the silicon wafer 36 so as to cover a part of the opening of the crucible 17 above the crucible 17. To do. The dimensions of the silicon wafer 36 are the same as those of the silicon wafer 26 of the first embodiment, and the surface facing the crucible 17 is mirror-etched. <Embodiment 3> As shown in FIG. 5, in this embodiment, three seed crystals 31 in the shape of a rectangular column made of a silicon single crystal suspended above a crucible 17 of the same shape and size as in Embodiment 1 are provided with three pieces at the tip. The locking portion 31a is formed, and the hooking holes 46a of the three silicon wafers 46 are formed at the tip of the seed crystal 31.
3 silicon wafers 46 so as to cover a part of the opening of the crucible 17 above the crucible 17 by being hooked on the crucible 17.
Hold horizontally. The dimensions of the silicon wafer 46 are the same as those of the silicon wafer 26 of the first embodiment.
The surface facing to is mirror-etched.

Comparative Example 1 A crucible 17 having the same shape and size as in Example 1 was charged with the same granular material 24 made of polycrystalline silicon as in Example 1, and a silicon wafer was placed above or above it. Without heater 17 and crucible 17
Was heated to melt the granules 24. <Comparative Test> Crucible 17 of Examples 1 to 3 and Comparative Example 1
Then, 100 kg of the granular material 24 made of polycrystalline silicon was put into the container, and the crucible 17 was heated by a heater to measure the time until the granular material 24 was melted. The results are shown in Table 1.

[0013]

[Table 1]

As is clear from Table 1, the time until the granules 24 of Examples 1 to 3 melt is shorter than that of Comparative Example 1 by 1 to 2 hours. Especially granular material 24
In Example 1, which was arranged so as to cover the silicon wafer 26 on the upper surface of the above, it could be melted in about two-thirds of the melting time of Comparative Example 1. It is considered that this is because the heat of the heater 13 was effectively used by the silicon wafers 26, 36 and 46 as the heat of melting the particulate matter 24.

[0015]

As described above, according to the present invention, it is simple to dispose one or more silicon wafers on the upper surface or above the lumps or particles of polycrystalline silicon in the crucible. Depending on the method, the melting time of the agglomerates or granules can be further shortened. Further, it is not necessary to remove the silicon wafer together with the lumps or granules, or after melting the lumps or granules into a silicon melt and then melting the silicon melt in the melt to remove them from the furnace body. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a crucible showing an arrangement state of a silicon wafer according to a first embodiment of the present invention.

FIG. 2 is a view of the crucible viewed from above.

FIG. 3 is a diagram corresponding to FIG. 1 and showing a second embodiment of the present invention.

FIG. 4 is a perspective view showing a state where the silicon wafer is hooked on a seed crystal.

FIG. 5 is a sectional view showing a state in which a silicon wafer of Example 3 of the present invention is hooked on a seed crystal.

FIG. 6 is a schematic cross-sectional view of a single crystal growth apparatus by the CZ method.

[Explanation of symbols]

11 furnace body 12 Insulation 13 Heater 14 rotation axis 16 Graphite susceptor 17 crucibles 18 rotation and pulling mechanism 19 wires 21,31 seed crystals 21a, 31a Locking part 23 Infrared reflector 24 Agglomerates or granules 26, 36, 46 Silicon wafer 36a, 46a Hook holes

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-283693 (JP, A) JP-A-3-193694 (JP, A) Actually open Sho 64-26377 (JP, U) Actually open 6- 42967 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (6)

(57) [Claims] 1. A polycrystalline silicon in which a lump or granular material (24) made of polycrystalline silicon is placed in a crucible (17) and the crucible (17) is heated to melt the lump or granular material (24). In the melting method of (1), one or more silicon wafers (26) are arranged on or above the lumps or particles (24) made of polycrystalline silicon in the crucible (17). Method of melting crystalline silicon. 2. One or more silicon wafers (36,
A hook hole (36a, 46a) is formed in the center of the 46) and a seed crystal (2) made of a silicon single crystal suspended above the crucible (17).
Locking parts (21a, 31a) are formed at the tips of (1, 31), and the hooking holes (36a, 46a) of the silicon wafers (36, 46) are fitted to the locking parts (21
The silicon wafer (36, 46) is held horizontally so as to cover a part of the opening of the crucible (17) above the crucible (17) by being hooked on (a, 31a). Method for melting polycrystalline silicon. 3. The method for melting polycrystalline silicon according to claim 1, wherein the silicon wafer (26, 36, 46) is a mirror-polished or mirror-etched wafer. 4. The silicon wafer (26) is melted together with lumps or particles of polycrystalline silicon.
Alternatively, the method for melting polycrystalline silicon according to Item 3. 5. The polycrystal according to claim 2, wherein a lump or granular material made of polycrystalline silicon is melted to form a silicon melt, and then the silicon wafer (36, 46) is melted in the melt. How to melt silicon. 6. The silicon wafer (26,36,46) containing the same dopant as the dopant contained in the silicon single crystal ingot grown by the silicon wafer (26,36,46).
The method for melting polycrystalline silicon according to claim 4 or 5, wherein the content of the dopant in the polycrystalline silicon ingot is an amount necessary to bring the silicon single crystal ingot to a required dopant concentration or less.