JP3126530B2 - Method and apparatus for producing single crystal - 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 and an apparatus for producing a single crystal used as a material of a single crystal substrate for producing a semiconductor circuit, and more particularly to a heater, a crucible and the like while ensuring the quality of the single crystal. It is also possible to extend the life of the component parts.

[0002]

2. Description of the Related Art In the field of semiconductor manufacturing, the Czochralski method (CZ method) has been generally used as a method for growing a silicon single crystal. As an example of an apparatus using this method, for example, an apparatus as shown in FIGS. 5 and 6 can be exemplified.

[0003] Both of these apparatuses 1a and 1b mainly include a heating chamber 2a in which a structure for melting silicon is accommodated.
And a pull-up chamber 2b for accommodating a silicon crystal S to be pulled up. In the heating chamber 2a, a crucible 3 and a heater arranged so as to surround mainly the side surface of the crucible 3 4 are provided. The crucible 3 contains silicon melted by the heater 4. The crucible 3 is supported by a driving device (not shown) so as to be rotatable and vertically movable by a rotating shaft 5. During the crystal pulling, the crucible 3 is rotated at a predetermined speed by the driving device and is raised by the liquid level drop. . Usually, the crucible 3 comprises a quartz crucible 3a and a graphite crucible 3b for protecting the quartz crucible 3a. A heat insulating material 6 is arranged on the outer periphery of the heater 4, that is, on the side of the heating chamber 2 a. The heat insulating material 6 prevents heat from the heater 4 from escaping to the outside of the heating chamber 2a.

On the other hand, a pulling wire 7 is provided in the pulling chamber 2b and penetrated through the top wall, and a chuck 9 for holding a seed crystal 8 is provided at the lower end of the pulling wire 7.
Is provided. The upper end of the pulling wire 7 is wound around a wire hoist 10 so as to pull up the silicon crystal S at a predetermined speed.

In the chamber 2, for example, argon (Ar) is introduced through a gas inlet 11 formed in the pulling chamber 2 b.
An inert gas such as a gas is introduced, sucked by a vacuum pump (not shown), flows through the heating chamber 2a, and is exhausted from the gas outlets 12a and 12b. Thus, chamber 2
Ar gas flows through the chamber 2 because S generated in the chamber 2 due to the melting of silicon due to the heating of the heater 4.
This is for preventing impurity contamination and dislocation of the silicon crystal body S by preventing iO gas and CO gas from being mixed into the silicon melt. In the apparatus 1a shown in FIG. 5, the gas outlet 12a is connected to the heater 4 at the bottom of the heating chamber 2a.
It is provided immediately below (this is called A type),
In the apparatus 1b shown in FIG. 6, a gas outlet 12b is provided between the peripheral edge of the bottom of the heating chamber 2a and a position immediately below the heat insulating material 6 (this is referred to as a B type). Therefore,
In the type A apparatus 1a, as shown by the arrow in FIG.
The Ar gas flowing from the gas inlet 11 is mainly supplied to the crucible 3.
Exhausted from the gas outlet 12a through the space between the heater 4 and the heater 4 and between the heater 4 and the heat insulating material 6,
In the B type device 1b, as shown by the arrow in FIG.
The Ar gas that has flowed into the chamber 2 passes mainly between the heat insulating material 6 and the inner wall of the heating chamber 2a, and the gas exhaust port 12b
It will be exhausted from.

[0006]

As described above, there are roughly two types of formation positions of the gas outlets, the A type and the B type, and the flow of Ar gas differs depending on each type. Each type has its advantages and disadvantages. Conventionally, it has been selectively fixed to either the A type or the B type depending on the design concept.

That is, in the case of the A type, the Ar gas flowing from the gas inlet 11 flows down along the crucible 3 and the heater 4 almost straight regardless of the position of the crucible 3, so that the gas flow is not so large. There is an advantage that the SiO gas and the CO gas in the chamber 2 can be efficiently and smoothly exhausted without being disturbed. On the other hand, since the SiO gas in the gas flow comes into contact with the heater 4 and the crucible 3, the members 3 and 4 made of carbon react with the SiO gas and the heater 4 and the like are worn out, and the life of the heater 4 and the like is reduced. In addition to the disadvantage that the gas flow is reduced, the gas flow passes near the heater 4 and is heated to increase the exhaust temperature, which may cause damage to valves and O-rings of the exhaust pipe system.

On the other hand, in the case of the B type, the Ar gas flowing from the gas inlet 11 mainly flows down between the heat insulating material 6 and the inner wall of the chamber 2 a, and flows along the crucible 3 and the heater 4. Since there is almost no flow, the exhausted SiO gas and CO gas do not make much contact with the heater 4 and the crucible 3, so that the heater 4 and the crucible 3 have a long service life. Since the air does not flow directly through the heat insulating material 6 and is not directly heated by the heater 4, the exhaust temperature is relatively low, so that there is little risk of damaging the exhaust pipe system. However, on the other hand, there is turbulence in the gas flow as shown by the dotted line in the figure,
In the vicinity of the upper portion of the crucible 3, stagnation occurs in which Ar gas hardly flows. In such stagnation, SiO gas or CO gas stays. There is a possibility that impurity contamination or dislocation of crystal S may be caused. This disadvantage becomes more remarkable because the lower the position of the crucible 3 with respect to the heat insulating material 6, the greater the turbulence of the gas flow and the more pronounced the stagnation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and prevents impurity contamination and dislocation of a silicon crystal to maintain its quality.
It is an object of the present invention to provide a method and apparatus for manufacturing a single crystal body capable of preventing wear of a heater or a crucible and damage to an exhaust pipe system as much as possible and extending the life of components.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a seed crystal is brought into contact with a melt that melts in a crucible that can be raised and lowered, and the seed crystal is gradually pulled up in an inert gas atmosphere. In the method for producing a single crystal by growing a single crystal, by forming a flow of an inert gas flowing down along the crucible and a heater arranged on the outer periphery when the position of the crucible is relatively low, When the position of the crucible is relatively high, a flow of an inert gas flowing between the heat insulating material disposed on the outer periphery of the heater and the inner wall of the chamber is formed.

[0011] Further, the crucible has a crucible for accommodating the melt in the chamber and a heater arranged on the outer periphery of the crucible to heat the crucible, and flows through an inert gas inlet provided in an upper part of the chamber. In a single crystal manufacturing apparatus for pulling up and growing a single crystal from a melt in the crucible while causing an inert gas to flow down in the direction of the crucible, heat insulation is provided on the outer periphery of the heater to block heat from the heater. In addition to disposing the material, first and second inert gas discharge ports are respectively provided inside and outside the heat insulating material below the chamber, and the first and second inert gas discharge ports are switched. It is characterized by having switching means.

[0012]

When the crucible is manufactured by the above-described process and the position of the crucible is relatively low, and therefore the turbulence of the inert gas flow is likely to occur, the inert gas introduced into the chamber is substantially straightened. Since the gas flows down along the heater and the inert gas flow is not disturbed, the efficiency of the exhaust gas is increased, the SiO gas and the CO gas are smoothly exhausted, and the quality is secured. In addition, when the position of the crucible is relatively high, and thus the turbulence of the inert gas flow is unlikely to occur in the first place, the inert gas flows down between the heat insulating material and the inner wall of the chamber. Contact with the crucible and the heater is avoided, the degree of wear of the heater and the like is reduced, and the exhaust temperature is reduced because the heater is not directly heated. Therefore, the deterioration of the equipment becomes slower as a whole, and the life is extended.

Further, with the above-described configuration, the first inert gas outlet and the second inert gas outlet are switched by the switching means, so that the flow of the inert gas is optimized according to the relative position of the crucible. It will be able to be in a state.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an apparatus for manufacturing a single crystal according to an embodiment of the present invention, FIG. 2 is an operation flowchart of a control device of the embodiment, and FIG. 3 is a gas flow state when the crucible position is low according to the embodiment. FIG. 4 is a view showing a gas flow state when the crucible position is high according to the same embodiment.
Note that members common to the members in FIGS. 5 and 6 are denoted by the same reference numerals.

The single crystal manufacturing apparatus 20 has a member for melting silicon, a mechanism for pulling up crystallized silicon, and the like. The member for melting silicon is accommodated in the heating chamber 2a. The mechanism for pulling up the silicon single crystal is provided by a separation mechanism 13 from the heating chamber 2a.
The pulling chamber 2b is provided inside and outside of the pulling chamber 2b which can be separated.

A crucible 3 for accommodating molten silicon is provided in the heating chamber 2a. The crucible 3 is supported by a driving device 21 by a rotating shaft 5 so as to be rotatable and vertically movable. The driving device 21 raises the crucible 3 by an amount corresponding to the lowering of the liquid level to compensate for the lowering of the liquid level due to the pulling of the silicon single crystal S, and constantly rotates the crucible 3 at a predetermined rotational speed for stirring the silicon melt. Rotate with. The rotating shaft 5 penetrates through the heating chamber 2a, but is held by a special bearing (not shown) in order to keep the inside and outside of the chamber 2 airtight and to use it under extremely poor temperature conditions. The crucible 3 is composed of a quartz crucible 3a and a graphite crucible 3b for protecting the same as in the prior art.

A heater 4 for melting silicon is arranged on the side wall of the crucible 3 so as to surround the periphery thereof. Outside the heater 4, a heat insulating material 6 for preventing heat from the heater 4 from being directly radiated to the heating chamber 2 a is provided so as to surround the periphery thereof. This heat insulating material 6 is attached to an annular support portion 22. The support portion 22 is made of a material having a very large thermal resistivity. The support portion 22 completely blocks the radial flow of Ar gas under the heat insulating material 6. As a result, irrespective of which gas outlet is switched to which gas outlet will be described later, the turbulence of the gas flow in the chamber 2 can be minimized.

One end of the pulling chamber 2b is attached to the wire hoisting machine 10, and a pulling wire 7 is provided which is suspended through the top wall of the pulling chamber 2b. And a chuck 9 for holding the seed crystal 8. Wire hoisting machine 10
The silicon single crystal body S that gradually grows on the lower end side of the seed crystal 8 is pulled up according to the growth rate or the like, and at the same time, is constantly rotated in the direction opposite to the rotation direction of the crucible 3.

In the chamber 2, as described above, the silicon in the chamber 2 is melted by the heating of the heater 4 to melt the silicon.
Ar gas is circulated in order to prevent the SiO gas and CO gas generated inside the silicon melt from being mixed into the silicon melt. For this reason, the pulling chamber 2 b is not allowed to introduce Ar gas into the chamber 2. A gas inlet 11 is formed as an active gas inlet, and in this embodiment, a first inert gas outlet is provided at the bottom of the heating chamber 2a on the inside and outside of the support 22 with reference to the support 22. A first gas outlet 23 and a second gas outlet 24 as a second inert gas outlet are formed. The first gas outlet 23 and the second gas outlet 24 correspond to conventional A type and B type gas outlets, respectively. The first gas outlet 23 and the second gas outlet 24 are each connected to the branch pipe 2.
The branch pipes 25 and 26 are connected to a main pipe 28 via a switching valve 27 as switching means. The main pipe 28 is provided with a pressure control valve 29 for adjusting the pressure of the gas flow to be exhausted, and a vacuum pump 30. The exhaust pipe 31 includes the main pipe 28 and branch pipes 25 and 26. Therefore, the Ar gas introduced into the chamber 2 from the gas inlet 11 is drawn by the vacuum pump 30 and flows through the heating chamber 2 a, and depending on the position of the switching valve 27, the Ar gas is discharged from the first gas outlet 23 or the second gas outlet 23. The gas is exhausted from the gas outlet 24 and exhausted through the exhaust pipe 31.

Further, in this embodiment, a control device 32 is provided to automatically control the device 20. The control device 32 includes a drive device 21, a switching valve 27, a pressure control valve 2
9, a vacuum pump 30 and the like are connected, and various sensors necessary for control are connected. This control device 32
Calculates and processes signals from various sensors,
1. Comprehensively control the switching valve 27, the pressure control valve 29, the vacuum pump 30, and the like. Among them, regarding the control of the switching valve 27, the control device 32 switches the switching valve 27 to the first gas outlet 23 or the second gas outlet 24 according to the relative position of the crucible 3 with respect to the heat insulating material 6. . In particular,
As will be described later, when the position of the crucible 3 is “low”, the first gas discharge port 23 and the exhaust pipe 31 are communicated, and the crucible 3
Is high, the control is performed such that the second gas outlet 24 and the exhaust pipe 31 communicate with each other. This is because when the position of the crucible 3 is relatively low, turbulence in the gas flow is likely to occur and problems in quality are likely to occur.
It should be emphasized that the SiO gas and CO gas generated in the chamber 2 are smoothly discharged to ensure the quality, and from this viewpoint, the Ar gas is discharged from the crucible 3 as in the case of the conventional A type. Flowing between the heater and the heater 4 is C
It is preferable in terms of smooth discharge of O gas and the like. On the other hand, when the position of the crucible 3 is relatively high, the turbulence of the gas flow does not occur so much, and the stagnation of the Ar gas, which causes poor quality, is unlikely to occur. Even if Ar gas is flowed between the heat insulating material 6 and the inner wall of the heating chamber 2a, it is possible to maintain a certain level or more of quality. Therefore, at this time, rather than reducing the life of the heater 4 and the crucible 3 and increasing the exhaust gas temperature, the flow of Ar gas such as the conventional B type is sacrificed. This is more preferable in terms of extending the life of the heater 4 and the crucible 3 and lowering the exhaust temperature.

In this embodiment, "high" or "low" of the position of the crucible 3 is "high" when the upper end of the quartz crucible 3a is above the upper end of the heat insulating material 6, and "low" when it is not. Is defined. Further, the position of the crucible 3 is detected by a position detection sensor such as an encoder attached to a motor in the driving device 21.

Next, the operation of the apparatus of the present invention configured as described above and the method of the present invention realized by the apparatus will be described.

First, in manufacturing a silicon single crystal, the pulling chamber 2b is separated from the heating chamber 2a by a separation mechanism, and a crude silicon crystal as a raw material and a very small amount of impurities are charged into a crucible 3 to be separated. The pulling chamber 2b is attached to the heating chamber 2a by the mechanism 13. In this state, the heater 2a is heated to wait for the silicon in the crucible 3 to be melted. When the silicon is in a molten state, the wire hoisting machine 10 is operated to lower the pulling wire 7 and the seed crystal 8 attached to the chuck 9
Is in contact with the silicon melt surface. In this state,
When the silicon crystal starts growing on the seed crystal 8, the wire hoist 10 is pulled up at a predetermined speed, and the silicon crystal S is grown as shown in FIG. In this process, the control device 32 switches the switching valve 27 to the first gas outlet 23 side or the second gas outlet 24 side in accordance with the position of the crucible 3 to control the flow of the Ar gas flowing through the chamber 2. Control the route.

That is, as shown in the flowchart of FIG. 2, the control device 32 inputs a signal of a position detection sensor (not shown) to detect the position of the crucible 3 (S1), and the position of the crucible 3 is determined according to the above definition. It is determined whether it is "low" (S2).

As a result of this judgment, when the position of the crucible 3 is "low" (that is, the upper end of the quartz crucible 3a is
Specifically, for example, at the time of initial melting when the silicon in the crucible 3 has started to melt, or when pulling up a low-acid material having a low oxygen content in silicon, for example. The switching valve 27 is set to the first gas outlet 23 side, and the Ar gas flow in the chamber 2 is set to the first
The gas is exhausted from the gas outlet 23 (S3). At this time, the Ar gas flowing from the gas inlet 11 flows between the crucible 3 and the heater 4 and between the heater 4 and the heat insulating material 6 as shown in FIG. The gas passes through the first gas outlet 23 and is discharged. As described above, since the exhaust efficiency at this time is high, the SiO gas and the CO gas generated in the chamber 2 can be quickly and smoothly exhausted to the outside of the chamber 2, and the impurity contamination of the silicon crystal S and the presence of Dislocation can be prevented and excellent quality can be ensured.

On the other hand, when the position of the crucible 3 is “high” as a result of the determination in step 2 (that is, when the upper end of the quartz crucible 3a is higher than the upper end of the heat insulating material 6), specifically, for example, When the growth of the crystal S progresses and the amount of its pulling is large, the switching valve 27 is connected to the second gas outlet 24.
Then, the Ar gas flow in the chamber 2 is exhausted from the second gas outlet (S4). Such switching can be allowed, as described above, in the crucible 3.
When the position is "high", the gas flow is not greatly disturbed in the first place due to the height relationship with the heat insulating material 6, and the exhaust efficiency above a certain level is achieved. Therefore, the quality is ensured. This is because there is no need to attach importance to. At this time, Ar flowing from the gas inlet 11
As in the case of the conventional B type, the gas is discharged from the second gas outlet 24 through between the heat insulating material 6 and the inner wall of the heating chamber 2a as shown in FIG. Therefore, as described above, the exhausted SiO gas and CO gas do not come into contact with the crucible 3 and the heater 4 so much that the wear of the crucible 3 and the heater 4 is reduced, and their life is extended. Since the flow is not directly heated by the heater 4, the exhaust gas temperature is reduced, the damage to the exhaust pipe system is reduced, and the life thereof is improved.

As described above, the route of the gas flow in the chamber 2 is controlled to an optimum state according to the position of the crucible 3, so that the advantages of the conventional A-type apparatus 1a and the B-type apparatus 1b are different. As a whole, the crucible 3 and the heater 4,
In addition, the life of the exhaust pipe 31 system can be improved.

In order to support this, the device 2 of the present embodiment
0 and the carbon concentration when using the method (solidification ratio 0.8
), An experiment was performed to compare the life of the heater 4 (the time until the resistivity changes by 5%) and the exhaust temperature (the temperature of the exhaust pipe) with the conventional technology (A type and B type). The results are as shown in Table 1 below.

[0029]

[Table 1]

As can be seen from the above results, when the method of the present invention is carried out using the apparatus 20 of the present invention, results such as a decrease in carbon concentration, a prolongation of heater life, and a decrease in exhaust gas temperature are obtained. It is possible to extend the life of the components of the apparatus while maintaining the quality of the crystal.

In this embodiment, the switching valve 27 is switched by automatic control. However, the present invention is not limited to this. The switching valve 27 may be manually operated according to the situation.

In this embodiment, the crucible 3 is "high".
Although "low" is defined by the relationship between the upper end of the quartz crucible 3a and the upper end of the heat insulating material 6, it is a matter of course that the present invention is not limited to this. The switching timing may be any reference as long as the above-described effects can be obtained.

[0033]

As described above, according to the present invention, since the flow of the inert gas in the chamber is optimized according to the relative position of the crucible, it is possible to extend the life of the parts of the apparatus while maintaining the quality. it can.

Further, since the inert gas discharge ports are provided in two lines and switched by the switching valve, the flow of the inert gas in the chamber can be freely switched.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for producing a single crystal according to one embodiment of the present invention.

FIG. 2 is an operation flowchart of the control device of the embodiment.

FIG. 3 is a diagram showing a gas flow when the crucible position is low according to the embodiment.

FIG. 4 is a diagram showing a gas flow when the crucible position is high.

FIG. 5 is a schematic configuration diagram showing an example of a conventional device.

FIG. 6 is a schematic configuration diagram showing another example of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 ... Chamber 2a ... Heating chamber 2b ... Pulling-up chamber 3 ... Crucible 4 ... Heater 6 ... Heat insulation material 8 ... Seed crystal 11 ... Gas inlet 22 ... Supporting part 23 ... 1st gas outlet (1st inert gas outlet) 24) second gas outlet (second inert gas outlet) 27 switching valve (switching means) 31 exhaust pipe 32 control device

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-87687 (JP, A) JP-A-1-282183 (JP, A) JP-A-2-1722884 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (2)

(57) [Claims] A method for producing a single crystal, wherein a single crystal is grown by bringing a seed crystal into contact with a melt that is melted in a crucible that can be raised and lowered, and gradually pulling the seed crystal in an inert gas atmosphere. When the position of the crucible is relatively low, a flow of an inert gas flowing down along the crucible and the heater arranged on the outer periphery is formed. When the position of the crucible is relatively high, the flow of the heater A method for producing a single crystal, wherein a flow of an inert gas flowing down between a heat insulating material disposed on an outer periphery and an inner wall of a chamber is formed. 2. A crucible for accommodating a melt in a chamber, and a heater disposed on the outer periphery of the crucible and heating the crucible, and flows through an inert gas inlet provided at an upper portion of the chamber. In a single crystal manufacturing apparatus for pulling up and growing a single crystal from a melt in the crucible while causing an inert gas to flow down in the crucible direction, heat insulation is provided around an outer periphery of the heater to block heat from the heater. In addition to disposing the material, first and second inert gas discharge ports are respectively provided inside and outside the heat insulating material below the chamber, and the first and second inert gas discharge ports are switched. An apparatus for producing a single crystal, comprising switching means.