JPH0450192A - Apparatus for pulling up silicon single crystal substance - Google Patents

Abstract

PURPOSE:To reduce the carbon or oxygen content and prevent the dislocation from being induced in a single crystal substance by covering the upper part of a melting zone in a raw material melt with a covering unit. CONSTITUTION:The interior of a heating chamber (2a) in a chamber 2 is provided with a crucible 3 of U-shaped cross section composed of a crucible (3b), made of graphite and supported by a pan 5 and a crucible (3a) made of quartz. The interior of the crucible (3a) is divided into a melting zone (9a) and a solidifying zone (9b) with an annular partition wall 8 and the upper area of the zone (9a) is covered with a covering unit 22 composed of a substrate part (22a) supported by a heat insulating material 21 and a rectifying projecting part (22b). Polycrystal silicon powder is fed from a nozzle 12 into the zone (9b) of the crucible (3a) and melted. An inert gas is simultaneously made to flow down from the upper part into the chamber (2a), passed from the upper part of the zone (9a) over the partition wall 8 into a space (S) between the projecting part (22b) and the melt and then discharged from a clearance between the crucible (3a) and the heater 4. A seed crystal 16 attached to a chuck 15 of a up wire 14 is subsequently pulled up to grow a silicon single crystal (C).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a pulling device for pulling silicon single crystals by the Czochralski method (CZ method), particularly in one using a double crucible.

(Prior art) As a method for manufacturing single crystals of silicon, germanium, gallium arsenide, etc., the Czochralski method (CZ method), in which crystals are grown and pulled from a raw material melt in a crucible, is widely used. It is.

Furthermore, nowadays, impurities are added for the purpose of making a single crystal body have a predetermined resistivity or reducing the dislocation density in the crystal body. However, in the CZ method, the impurity concentration in the crucible changes as the crystal grows due to segregation, and the impurity concentration distribution in the growth direction also changes accordingly, making it difficult to develop a large single crystal with a uniform concentration distribution. There is a problem that it cannot be done.

As measures to improve this point, recently, a multi-strand growth method, a dopant evaporation method, a double crucible method, etc. have been proposed.

FIG. 3 is a cross-sectional view schematically showing a single crystal pulling apparatus for the double crucible method.

This pulling device 1 has a chamber 2 consisting of a heating chamber part 2a and a pulling chamber part 2b, and a crucible 3 and a cylindrical heater 4 surrounding the crucible 3 are installed in the heating chamber part a. It is being

The crucible 3 of this example is a quartz crucible 3a whose outer periphery is protected by covering it with a graphite crucible 3b. At the bottom of the graphite crucible 3b, a rotating shaft 7 of a drive unit 6 is attached via a tray 5, and a ring-shaped partition wall 8 is provided in the quartz crucible 3a. The quartz crucible 3a divides the raw material melt 9 into a melting zone 9a and a solidification zone 9b.
It is divided into two parts.

Note that a communication port O is provided at the lower end of this partition wall 8, and both zones 9a and 9b are communicated with each other. A raw material is supplied to the melting zone 9a from a raw material supply device 11 through a nozzle 12. In addition, in the figure, the code "13" is the pulling drive part, "
14" is a pulling wire, and "15" is a chuck.

In order to grow a silicon single crystal C using this apparatus 1, first, a predetermined amount of raw materials such as polycrystalline silicon and dopants added as necessary are loaded into a quartz crucible 3a, and heated by a heater 4. The raw material melt 9 is formed by heating and melting. Then, the seed crystal 16 attached to the tip of the pulling wire 14 is immersed in the raw material melt ltMQ, and pulled out while rotating the quartz crucible 3a and the seed crystal 16 relative to each other, and the lower end of the seed crystal 16 is pulled out. A silicon single crystal C is grown.

However, this device 1 has the following problems.

■ Raw material 17i in quartz crucible 3a! l! Silicon monooxide (sin) evaporated from lfkg condenses and falls on the wall of the chamber 2, reaches the growth interface of the silicon single crystal, and becomes a crystal white dislocation. After that, dance! - The sharp polycrystalline silicon powder reaches the interface of the raw material melt 9 and polycrystallizes the single crystal C. (2) When the heater 4 is a graphite heater, this heater
As is clear from the reaction formula 2C0SiO-+CO+SiC, -carbon oxide is produced, but when this CO enters the raw material melt 9, the single crystal C becomes high-carbon. There are problems such as concentration and deterioration of quality.

Therefore, when pulling the silicon single crystal C, an inert gas such as argon gas G is drawn down into the pulling chamber 2, and this argon gas G is carried along to remove evaporated substances from the system through the exhaust passage 17. is being discharged.

(Problem to be Solved by the Invention) However, in the conventional double crucible method for pulling single crystals, the argon gas G flowing down from above flows along the silicon single crystal C to be pulled, and the raw material melts. Since it is directed laterally at the surface of the liquid 9, silicon monoxide evaporated from the coagulation zone 9b, floating powder polycrystalline silicon, or carbon monoxide generated by the above reaction (hereinafter simply referred to as evaporates), etc. , it will definitely be ejected towards the side.

However, as shown in FIG. 4, this argon gas G causes a vortex in the upper part of the melting zone 9a beyond the partition wall 8 that partitions the melting zone 9a and the solidification zone 9b. There is a possibility that evaporated matter and the like will be taken in and stagnate, and will be taken in again into the melt 9 at a certain rate. As a result, the silicon single crystal C undergoes U dislocation, and the carbon and oxygen concentrations in the crystal increase, resulting in a significant deterioration in quality.

Furthermore, in the conventional pulling device 1, as is clear from FIG.
When flowing into the heating chamber section 2a from the side b, the argon gas G is not in a sufficiently rectified state, and flows down while generating a vortex at the shoulder section A of the heating chamber section 2a. In this part of the vortex, the argon gas G substantially remains, and some of the evaporated matter, etc., remains in this shoulder region A or adheres to the inner circumferential wall, and this condenses and drips. Then, there is a possibility that the above-mentioned white dislocation may occur.

Furthermore, in the conventional pulling device 1, since the internal space of the heating chamber part 2a is relatively large, the heat dissipated from the raw material melt 9 is large, and the heating heater required to form the raw material melt 9 is large. 4. I use one with a large heat capacity. As a result, the wall surface temperature of the quartz crucible 3a heated by the heater 4 increases, the amount of oxygen eluted from the quartz crucible 3a increases, and the oxygen content of the silicon single crystal C obtained increases. Become.

The present invention has been made in view of the problems of the prior art described in -1-, and aims to reduce the carbon content or oxygen a content of a silicon single crystal produced by the CZ method, thereby increasing the whiteness of the crystal. An object of the present invention is to provide a silicon single crystal pulling device capable of stably growing a high quality silicon single crystal without dislocations.

(Means for solving problems)! - The present invention for achieving the above objectives includes:
A double crucible in which the raw material melt is divided into a melting zone and a solidification zone by a partition wall, and a heater for heating this double crucible are provided, and an inert gas is flowed from one side toward the crucible in the dish. , a silicon single crystal drawing device for removing evaporated matter from the raw material melt in the crucible, characterized in that a cover is provided to cover the upper region of the melting zone. This is a crystal pulling device.

The cover of the present invention includes a substrate portion provided to cover two regions of the melting zone, and a distal end portion of the substrate portion, which covers an inner circumferential wall of the crucible, an outer circumferential wall of the partition wall, and the melting zone. This is a silicon single crystal pulling device characterized by having a rectifying protrusion protruding into a space defined by a raw material melt surface.

(Function) In the present invention configured as described above, the inert gas flowing down from the top of the crucible flows laterally on the surface of the raw material melt along the silicon single crystal being pulled. Later, it flows over the partition wall that partitions the melting zone and the solidification zone, but at this time, it is rectified by the cover, so that it does not create vortices in the two parts of the melting zone or stagnate in the part 212. Evaporated matter, powdered polycrystalline silicon, carbon oxide, etc. are sent to this inert gas and discharged laterally to the anchor.

The cover also prevents an increase in the amount of oxygen eluted from the quartz crucible due to the influence of evaporated matter remaining in the shoulder portion of the heating chamber or the increase in the temperature of the raw material melt.

Therefore, as a whole, high carbonization, high oxygen content, and G dislocation of the silicon single crystal are prevented, and a stable silicon single crystal with good quality can be grown.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is an overall sectional view showing one embodiment of the present invention, and FIG. 2 is an enlarged sectional explanatory view of the main parts of FIG. 1. The same members as those shown in FIGS. , and some explanations are omitted.

4. The silicon single crystal pulling apparatus 20 of this embodiment has a chamber consisting of a large-diameter heating chamber section 2a and a small-diameter pulling chamber section 2b provided coaxially with the heating chamber section 2a. It has 2. A crucible 3 having a U-shaped cross section and supported by a graphite malt plate 5 is provided in the heating chamber part a, and the crucible 3 is protected by covering the outer periphery of the quartz crucible 3a with a graphite crucible 3b. There is. This crucible 3 is connected to a rotating shaft 7 and rotated by a drive device 6. A heater 4 is provided around the crucible 3 to melt the raw material contained in the quartz crucible 3a. The heater 4 can be of various types, such as one using a resistance heating method or one using an induction heating method, but when applied to a large continuous heating device, a resistance heating heater is used in consideration of economic efficiency. It is preferable.

A nozzle 12 from a raw material supply device (not shown) faces the quartz crucible 3a, and the raw material is supplied from this nozzle 12.

A heat insulating plate 21 is provided around the outer periphery of the heater 4- to prevent unnecessary heat from being transmitted to the chamber 2. Note that the heater 4 may be provided not only on the side of the crucible 3, but also a bottom heater 4a as in the illustrated embodiment, and both may be used in combination.

In particular, in this embodiment, a double crucible is used in which the interior of the quartz crucible 3a is partitioned into a melting zone 9a and a solidification zone 9b by an annular partition wall 8, and a cover 22 is provided on the quartz crucible 3a. There is.

This cover 22 covers the upper region of the melting zone 9a,
Any type of argon gas G flowing over the partition wall 8 may be used as long as it can be rectified without creating a vortex, but in this embodiment, it is supported by the heat insulating plate 21 and covers the upper region of the melting zone 9a. The substrate portion 22a provided as shown in FIG.
and a rectifying protrusion 2 provided at the tip of this substrate portion 22a.
2b.

The substrate portion 22a is a flat plate extending beyond the heater 4 and the melting zone 9a of the crucible 3 to near the partition wall 8, and the rectifying protrusion 22b is a flat plate extending beyond the melting zone 9a of the heater 4 and the crucible 3.
It projects into a space S defined by the inner wall of the partition wall 8, the outer peripheral wall of the partition wall 8, and the upper surface of the raw material melt of the melting zone 9a, and has a shape with a curved tip. This rectifying protrusion 22b
By forming the argon gas G, the vortex generated when the argon gas G crosses the partition wall 8 at the upper part of the melting zone 9a is canceled out, and the argon gas G flows smoothly.

Note that the rectifying protrusion 22b is arranged so that the droplets of powdered polycrystalline silicon added from the raw material supply device into the crucible 3 are arranged in the space S.
When considering the point of smooth outflow from LΦ:, it has been found that it is preferable to form the tip of the curved surface so that it is spaced about 50 mm from the liquid surface of the raw material melt 9.

Next, the effect will be explained.

First, a predetermined amount of polycrystalline silicon and a dopant to be added to it as needed are transferred from a raw material supply device to a quartz crucible 3.
a, and the heaters 4 and 4a are operated to melt it.

When starting the lifting work, argon gas G is blown into the heating chamber part a and the heating chamber part 2a is
into a reduced pressure argon atmosphere or a normal pressure argon atmosphere.

Next, a seed crystal 16 with a fixed surface orientation is attached to the chuck 15 of the pulling wire 14, and the pulling drive unit 13 is operated to lower the seed crystal 16 until its lower end is immersed in the raw material melt 9.

At the initial stage of pulling, the diameter of the silicon single crystal C is narrowed by setting the pulling speed fast and/or increasing the temperature of the raw material melt, and dislocations are expelled to the silicon single crystal surface. Translocate. Subsequently, the pulling speed and/or
Alternatively, by lowering the temperature of the raw material melt, a silicon single crystal C having a desired diameter is grown. In this case, while rotating the quartz crucible 3a etc. by the drive device 6,
It is preferable to also rotate the pulling wire 14 to stir the raw material melt 9 and equalize the temperature.

Note that while the pulling operation is being performed, the raw material is supplied from the raw material supply device to the quartz crucible 3a, and thereby the liquid level of the raw material melt 9 is always kept constant.

During this pulling, a part of the argon gas G flows along the silicon single crystal C, reaches the upper surface of the raw material melt 9 of the crucible 3, sends away evaporated matter, etc., and makes a U-turn.

As shown in FIG. 2, this argon gas G crosses the partition wall 8 and is divided into two surfaces: the inner wall of the quartz crucible 3a, the outer peripheral wall of the partition wall 8, and the raw material melt in the melting zone 9a. It flows into the space S.

In this case, the argon gas G is prevented from generating a vortex by the rectifying protrusion 22b, and flows down along the rectifying protrusion 22b. In addition, the argon gas G flowing in this space S also transports evaporated matter on the upper surface of the raw material melt in the melting zone 9a, is discharged from between the quartz crucible 3a and the heater 4, and is discharged from the discharge passage 17. Exhausted from the system.

Therefore, the evaporated matter etc. do not stay in the upper part of the melting zone 9a, and are reliably sent outside by the argon gas G. and G rearrangement are prevented.

Moreover, since this cover 22 covers the -L part of the raw material melt, it prevents heat radiation from the crucible 3, prevents the crucible 3 from becoming unnecessarily high in temperature, and prevents the crucible 3 from becoming unnecessarily high in temperature. An increase in the amount of oxygen eluted from the quartz crucible 3a is also prevented.

-1- The cover 22 of the embodiment described above is composed of a base plate portion 22a and a rectifying protrusion 22b, but the present invention is not limited to this embodiment, and may be modified in various ways. I can do it. For example, this cover 22 may not necessarily include the substrate portion 22a depending on the case, and the melting zone 9
The upper region of a may be covered to prevent eddies from occurring, or the substrate portion 22a and the rectifying protrusion 22b may be formed separately or integrally. Further, depending on the case, a part of the substrate portion 22a may be curved to prevent the argon gas G flowing over the partition wall 8 from generating a vortex.

(Effects of the Invention) As described above, in the present invention, when manufacturing a silicon single crystal by the CZ method, evaporated matter etc. do not stay in the upper region of the crucible, so silicon single crystals caused by this evaporated matter etc. High carbonization, high oxygen content, and dislocation of the crystal are prevented,
It is possible to grow stable silicon single crystals of good quality.

[Brief explanation of the drawing]

Fig. 1 is an overall sectional view showing an embodiment of the present invention, Fig. 2 is an explanatory sectional view showing the main parts of Fig. 1, and Fig. 3 is a sectional view showing a conventional silicon single crystal pulling device. , FIG. 4 is a cross-sectional explanatory view showing the main part of FIG. 3. 2...Chamber, 3...Double crucible, 8
...Partition wall, 9...Raw material melt, 9a...
- Melting zone, 9b... Solidification zone, 4.4a
... Heater, 22 ... Cover, 22a ... Substrate part, C ... Silicon single crystal, S ... Space part. 22b... rectifying protrusion, G... inert gas,

Claims (1)

[Claims] 1) The raw material melt (9) is placed in the chamber (2) through the partition wall (8).
A double crucible (3) partitioned into a melting zone (9a) and a solidification zone (9b) by
), an inert gas (G) is flowed down from above toward the crucible (3) to remove evaporated matter from the raw material melt (9), etc. In the apparatus, a cover (22) covering an upper region of the melting zone (9a) is provided.
) A device for pulling a silicon single crystal. 2) The cover (22) is provided on a substrate portion (22a) provided to cover the upper region of the melting zone (9a) and at the tip of the substrate portion (22a), and is provided on the tip of the substrate portion (22a), and
), the outer peripheral wall of the partition wall (8) and the melting zone (9a
2. The apparatus for pulling a silicon single crystal according to claim 1, further comprising a rectifying protrusion (22b) projecting into the space (S) defined by the upper surface of the raw material melt. .