JPH09175885A - Single crystal pull-up apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress the deterioration of the members in a furnace and the adhesion of bubbles on an inner crucible, etc., in a single crystal pull-up process. SOLUTION: This single crystal pull-up process is constituted in such a manner that semiconductor melt is held in a double layered crucible constructed by an outer crucible placed in a closed container and an inner crucible of a cylindrical partitioning body placed in the outer crucible, and a semiconductor single crystal is pulled up from the semiconductor melt in the inner crucible. In the state where the inner crucible 12 is separated from the outer crucible 11, a semiconductor raw material is melted in the outer crucible 11 and the semiconductor melt 21 is held in it. After the raw material has melted, the inner crucible is placed in the outer crucible to construct the double layered crucible. Thereafter, a magnetic field is applied on the semiconductor melt from the outside of the outer crucible to suppress the convection current of the semiconductor melt. In the state where the magnetic field is applied by a magnetic field-applying process, the semiconductor melt is adjusted at a temperature suitable for crystal growth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal pulling method for pulling a semiconductor single crystal from a semiconductor melt stored by using a double-structured crucible.

[0002]

2. Description of the Related Art Conventionally, the CZ method is known as one of the methods for growing a semiconductor single crystal such as silicon (Si) or gallium arsenide (GaAs). This CZ method has a large diameter,
It is a method used for the growth of various semiconductor crystals because it has characteristics such that a high-purity single crystal can be easily obtained without dislocations or with very few lattice defects.

In recent years, with the demand for a single crystal having a large diameter, high purity, and uniform oxygen concentration and impurity concentration, the CZ
The method has been variously improved and put to practical use. As one of the improved CZ methods, a continuous charge type magnetic field application CZ method using a so-called double crucible (hereinafter, abbreviated as CMCZ method) has been proposed. This method suppresses convection in the semiconductor melt by applying a magnetic field to the semiconductor melt in the crucible from the outside, and can control a single crystal with good controllability of oxygen concentration and good single crystallization rate. In addition, the raw material can be continuously supplied between the outer crucible and the inner crucible to easily obtain a long semiconductor single crystal. Therefore, it is said to be one of the most excellent methods for obtaining a large-diameter and long semiconductor single crystal.

FIG. 2 shows an example of a silicon single crystal pulling apparatus using the CMCZ method described in Japanese Patent Laid-Open No. 4-305091. This single crystal pulling apparatus 1 is
In the chamber 2 which is a hollow airtight container, the double crucible 3,
A heater 4 and a raw material supply device 5 are arranged respectively, and a magnet 6 is arranged outside the chamber 2.

The double crucible 3 is made of substantially hemispherical quartz (SiO 2).
₂ ) an outer crucible 11 and, as shown in FIG. 4, quartz (S) which is a cylindrical partition body provided in the outer crucible 11.
The inner crucible 12 made of iO ₂ ) is provided on the side wall of the inner crucible 12 between the inner crucible 12 and the outer crucible 11 (raw material melting region) and the inner crucible 12 (crystal growth region). A plurality of communication holes 13 that communicate with each other are formed.

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 has a predetermined angular velocity on a horizontal plane about the axis of the shaft 14. It is designed to rotate.
A semiconductor melt (raw material for a semiconductor single crystal that has been heated and melted) 21 is stored in the double crucible 3.

The heater 4 heats and melts the semiconductor raw material in the crucible and keeps the temperature of the generated semiconductor melt 21, and normally resistance heating is used. The raw material supply device 5 continuously feeds a predetermined amount of semiconductor raw material 22 onto the surface of the semiconductor melt 21 between the outer crucible 11 and the inner crucible 12.

The magnet 6 applies a magnetic field from the outside of the double crucible 3 to the semiconductor melt 21 in the double crucible 3, whereby the Lorentz force generated in the semiconductor melt 21 causes the semiconductor melt 21 to move. Control of convection, control of oxygen concentration, suppression of liquid level vibration, etc. are performed.

Raw material 2 supplied from the raw material supply device 5
As 2, the ingot of polycrystalline silicon is crushed by a crusher or the like to form flakes, or the granular particles of polycrystalline silicon deposited by a thermal decomposition method from a gas raw material are preferably used, If necessary, boron (B) (when making p-type silicon single crystal) or phosphorus (P)
An additional element called a dopant such as (for forming an n-type silicon single crystal) is further supplied. The same applies to gallium arsenide (GaAs). In this case, the additive element is zinc (Zn) or silicon (Si).

By the single crystal pulling apparatus 1 described above, the seed crystal 2 is attached to the pulling shaft 24 arranged above the inner crucible 12 and axially.
5 is suspended, and the seed crystal 25 is placed above the semiconductor melt 21.
The semiconductor single crystal 26 is grown using the as a nucleus.

By the way, in the conventional method for pulling a single crystal, as described in JP-A-63-303894, the outer crucible 11 is used in the previous step of growing the single crystal.
After a polycrystalline raw material such as a polycrystalline silicon mass is melted in advance to store the semiconductor melt 21, a constant magnetic field is applied to the semiconductor melt 2 in the outer crucible 11 by the magnet 6 to suppress its convection ( The flow rate is reduced to about 1/10), and the temperature of the semiconductor melt 21 in the outer crucible 11 is adjusted by the heater 4. After adjusting the temperature of the semiconductor melt 21, the inner crucible 12 arranged above the outer crucible 11 is placed in the outer crucible 11 to form the double crucible 3.

The double crucible 3 is formed after the raw material is melted in this manner. The raw material in the outer crucible 11 is heated by the heater 4 to obtain the semiconductor melt 21 by completely melting the raw material. This is because it is necessary to heat at a high temperature to the above temperature, and at this time, if the inner crucible 12 is placed in the outer crucible 11 in advance, large thermal deformation will occur in the inner crucible 12.

Therefore, after the raw material is completely melted, the heating by the heater 4 is weakened to some extent, and then the inner crucible 12 is heated.
By placing the on the outer crucible 11, high temperature heating at the time of melting the initial raw material is avoided and deformation of the inner crucible 12 is suppressed.

Further, the semiconductor melt 21 in the previous step
The temperature is adjusted as follows. [Raw Material Melting Step] First, by the heater 4 in order to completely melt the raw material in the outer crucible 11 to form the semiconductor melt 21, for example, in the case of a silicon raw material, the center liquid of the outer crucible 11 with respect to the melting point 1420 ° C. The vicinity of the surface 23 is heated to a high temperature of about 1470 ° C. At this time, FIG.
As shown by the solid line, the distribution of the melt temperature in the radial direction on the liquid surface of the outer crucible 11 is high in the vicinity of the outer periphery of the outer crucible 11 in the high temperature state and is low in the vicinity of the central liquid surface 23.

[Magnetic field applying step] When the magnetic field is applied to the semiconductor melt 21 by the magnet 6 after the raw material is completely melted, the thermal convection of the semiconductor melt 21 is suppressed and the stirring effect is deteriorated. Distribution (dotted line in the figure)
When the output of the heater 4 is constant, the value becomes higher near the outer periphery of the outer crucible 11 and, conversely, becomes lower near the central liquid level 23. Note that the magnetic field is not applied during the raw material melting step because the temperature of the melt near the central liquid level 23 decreases with the application of the magnetic field, so that the floating raw material near the central liquid level 23 is not sufficiently melted. This is because it is necessary to raise the output of the heater 4 to heat it and adjust the temperature near the central liquid surface 23 to the temperature before applying the magnetic field.

[Double Crucible Forming Step] Further, when the inner crucible 12 is placed inside the outer crucible 11 to form the double crucible 3 in a magnetic field applied state, the lower part of the inner crucible 12 contacts the semiconductor melt 21. Then, the semiconductor melt 2 is moved by the inner crucible 12.
There is a possibility that the heat of No. 1 will be absorbed and a local temperature drop will occur, and crystal growth will start in the lower part of the inner crucible 12. Therefore, it is necessary to further increase the output of the heater 4 and heat it to a sufficiently high temperature (one-dot chain line in the figure) at which crystal growth does not occur even if the temperature decreases due to heat absorption of the inner crucible 12.

After forming the double crucible, the output of the heater 4 is lowered and the melt temperature is lowered to a temperature suitable for crystal growth (two-dot chain line in the figure), and the process proceeds to the crystal growth step at a stable point.

[0018]

However, the above-mentioned single crystal pulling method has the following problems. That is, as described above, when the inner crucible is placed,
A high output of the heater 4 is required to prevent the temperature from decreasing, and accompanying this, excessive heating is applied to the internal members of the furnace for a long period of time, which causes these early deterioration.

On the other hand, when the inner crucible 12 is put into the semiconductor melt 21, if convection is remarkably generated, it is difficult for a gas (bubbles) such as argon, which is an atmospheric gas, to adhere to the inner crucible 12, but the magnetic field is previously set. If the convection is suppressed by the above, the effect of suppressing the adhesion of the gas is reduced.

The present invention has been made in view of the above-mentioned problems, and effectively suppresses the deterioration of furnace internal members, the adhesion of gas to the inner crucible, and the like, and stabilizes a long, large-diameter single crystal. The purpose is to provide a way to pull up.

[0021]

The present invention has the following features to attain the object mentioned above. That is, in the apparatus for pulling a single crystal according to claim 1, a semiconductor is provided in a double crucible formed by an outer crucible provided inside an airtight container and an inner crucible that is a cylindrical partition member arranged in the outer crucible. In a single crystal pulling method for storing a melt and pulling a semiconductor single crystal from the semiconductor melt in the inner crucible, the inner crucible and the outer crucible are separated, and the semiconductor raw material put in the outer crucible is melted. A raw material melting step of storing a semiconductor melt, and a double crucible forming step of forming a double crucible by placing the inner crucible in the outer crucible after the raw material melting step,
After the double crucible forming step, a magnetic field applying step for suppressing convection of the semiconductor melt by applying a magnetic field to the semiconductor melt from the outside of the outer crucible, and a magnetic field applied by the magnetic field applying step. A temperature adjusting step of adjusting the semiconductor melt to a crystal growth temperature.

In this single crystal pulling method, after the raw material melting step, the inner crucible is placed in the outer crucible, the magnetic field is applied to the semiconductor melt, and the melt temperature is adjusted in this state. When the inner crucible is placed, since the semiconductor melt is in a high temperature state sufficiently higher than the melting point after the raw material melting step, even if a local temperature decrease of the semiconductor melt occurs due to heat absorption of the inner crucible, it is sufficiently higher than the melting point. The temperature is maintained, crystal growth does not start in the lower part of the inner crucible, the output of the heater does not need to be further increased, and excessive heating is not applied to the furnace internal member. Further, since the magnetic field is not yet applied, thermal convection remarkably occurs, the gas attached to the inner crucible is easily separated, and the evaporation of the gas contained in the semiconductor melt from the liquid surface is promoted. .

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A method for growing a silicon single crystal in one embodiment of the method for pulling a single crystal according to the present invention will be described below with reference to FIGS. 1 and 2.

[Initial Raw Material Melting Step] First, a predetermined amount of the polycrystalline raw material of the polycrystalline silicon mass is put into the outer crucible 11,
The inside of the chamber 2 is evacuated by a vacuum pump or the like to be in a vacuum state.
Further, while introducing an inert gas such as argon (Ar) into the chamber 2 and rotating the shaft 14 on a horizontal plane at a predetermined angular velocity about the axis, the outer crucible 11 is rotated at a predetermined angular velocity, The heater 4 is energized to heat the polycrystalline raw material in the outer crucible 11 to a temperature equal to or higher than the single crystal growth temperature to completely melt the raw material. That is, the temperature near the central liquid surface 23 of the semiconductor melt 21 is heated to about 1470 ° C. with respect to 1420 ° C. which is the melting point of silicon. At this time, the temperature distribution of the semiconductor melt 21 in the radial direction of the outer crucible 11 is low near the central liquid level 23 and high near the outer periphery of the outer crucible 11 as shown by the solid line A in FIG.

[Double Crucible Forming Step] After the raw material is completely melted, the inner crucible 12 arranged with the same axis line above the outer crucible 11 is placed in the semiconductor melt 21, and the double crucible 3 is formed. To form. In addition, without changing the output of the heater 4,
Heating is performed with the same output as in the initial raw material melting step. At this time, since the semiconductor melt 21 is in a high temperature state sufficiently higher than the melting point after the raw material melting step, even if the temperature of the semiconductor melt 21 is locally lowered due to heat absorption of the inner crucible 12, the temperature is sufficiently higher than the melting point. Is maintained, crystal growth does not start in the lower part of the inner crucible 12, and there is no need to further increase the output of the heater 4, so that excessive heating is not applied to the furnace internal member.

Further, since the magnetic field is not yet applied, the thermal convection of the semiconductor melt 21 remarkably occurs, the gas attached to the inner crucible 12 is easily released, and the semiconductor melt 2
The evaporation of the gas contained in 1 from the liquid surface is promoted.

[Magnetic field applying step] After the double crucible 3 is formed, the magnet 6 is energized to apply a predetermined magnetic field to the semiconductor melt 21.
To suppress convection of the semiconductor melt 21. At this time, the temperature distribution of the semiconductor melt 21 is lower (1450 ° C.) near the central liquid level 23 as compared with the raw material melting step,
The vicinity of the outer periphery of the outer crucible 11 becomes higher (dashed line B in the figure).

[Temperature Adjustment Step] Further, after the magnetic field application step, the output of the heater 4 is slightly lowered to adjust the vicinity of the central liquid surface 23 of the semiconductor melt 21 to the single crystal growth temperature (1440 ° C.) (in the figure). Two-dot chain line C).

[Single Crystal Growth Step] After the melt temperature in the vicinity of the central liquid surface 23 is stabilized at the single crystal growth temperature, the seed crystal 25 suspended by the pulling shaft 24 is adapted to the semiconductor melt 21. A semiconductor single crystal 26 is grown using the seed crystal 25 as a nucleus. Here, after the seed crystal is made dislocation-free, the diameter of this single crystal is gradually increased to a semiconductor single crystal 26 having a predetermined diameter.

In this single crystal growing step, the granular silicon raw material 22 is continuously charged (if necessary, a dopant is added) according to the growth amount (pulling amount) of the semiconductor single crystal 26, and this is added. The supplied raw material 22 is the inner crucible 12
Is melted outside and is continuously supplied into the inner crucible 12 through the communication hole 13. As described above, it is possible to grow a good quality long large diameter semiconductor single crystal 26.

[0031]

As described above, according to the present invention, after the raw material melting step, the inner crucible is placed in the outer crucible, and then the magnetic field is applied to the semiconductor melt. Since the temperature is adjusted, since the semiconductor melt is in a sufficiently high temperature state when the inner crucible is placed, crystal growth does not start at the lower part of the inner crucible, and unnecessary crystal growth can be prevented. In addition, since it is not necessary to increase the output of the heater above the raw material melting step, deterioration of furnace internal members due to heating is suppressed, so that it is possible to prolong the replacement period of the members and reduce costs such as equipment costs. it can. Furthermore, since the inner crucible is placed before the magnetic field is applied, it is possible to suppress the adhesion of gas to the inner crucible due to active thermal convection of the semiconductor melt.

[Brief description of the drawings]

FIG. 1 is a graph showing a temperature distribution of a semiconductor melt in a radial direction inside an outer crucible in one mode of a single crystal pulling method according to the present invention.

FIG. 2 is a cross-sectional view of a single crystal pulling apparatus used for one mode of the single crystal pulling method according to the present invention.

FIG. 3 is a perspective view showing an inner crucible of a single crystal pulling apparatus used for one mode of a single crystal pulling method according to the present invention.

FIG. 4 is a graph showing a temperature distribution of a semiconductor melt in a radial direction inside an outer crucible in a conventional example of a single crystal pulling method according to the present invention.

[Explanation of symbols]

 1 Single Crystal Pulling Device 3 Double Crucible 4 Heater 6 Magnet 11 Outer Crucible 12 Inner Crucible 21 Semiconductor Melt 22 Raw Material

 ─────────────────────────────────────────────────── ─── 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 (1)

[Claims] 1. A semiconductor melt is stored in a double crucible formed by an outer crucible provided inside an airtight container and an inner crucible that is a cylindrical partitioning body arranged in the outer crucible, and the inner crucible is stored. In a single crystal pulling method for pulling a semiconductor single crystal from a semiconductor melt inside, a crucible is separated from an inner crucible, and a semiconductor raw material put in the outer crucible is melted to melt the raw material and melt the raw material. A step of forming a double crucible by placing the inner crucible in the outer crucible after the raw material melting step, and a step of forming a double crucible after the double melting step. A magnetic field applying step of applying a magnetic field to the semiconductor melt from one side to suppress convection of the semiconductor melt, and a temperature adjustment for adjusting the semiconductor melt to a crystal growth temperature while applying a magnetic field in the magnetic field applying step. To have a process Single crystal pulling method comprising.