JP2007254165A - Single crystal pulling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal pulling device that can suppress adverse influences of SiO gas generating from a silicon melt on a heat generating part of a heater and can achieve improvement in a life time of the heater and high quality of a single crystal. <P>SOLUTION: The device is equipped with a first gas supply means 13, 14, 17 to supply inert gas G from above a crucible 3, a second gas supply means 15, 16, 17 to supply inert gas G from below a heater 4, and an air discharging means 19 disposed above the heater 4 to discharge the inert gas G through a discharge port 18 to the outside of a furnace 2, wherein the inert gas G supplied by the first gas supply means 13, 14, 17 is introduced from above the crucible 3 into the crucible and discharged through the discharge port 18 above the heater 4, while the inert gas G supplied by the second gas supply means 15, 16, 17 flows upward between the heater 4 and the crucible 3 and discharged through the discharge port 18 above the heater 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a single crystal pulling apparatus that pulls up a single crystal while growing it by the Czochralski method (hereinafter referred to as “CZ method”).

  The CZ method is widely used for the growth of silicon single crystals. In this method, the seed crystal is brought into contact with the surface of the silicon melt contained in the crucible, the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. In this way, a single crystal is formed.

  As shown in FIG. 3, in the pulling method using the conventional CZ method, first, raw silicon is loaded into a quartz glass crucible 51 and heated by a heater 52 to obtain a silicon melt M. Thereafter, the seed crystal P attached to the pulling wire 50 is brought into contact with the silicon melt M to pull up the silicon crystal C.

  In general, prior to the start of pulling, after the temperature of the silicon melt M is stabilized, as shown in FIG. 4, necking is performed in which the seed crystal P is brought into contact with the silicon melt M to dissolve the tip of the seed crystal P. Necking is an indispensable process for removing dislocations generated in a silicon single crystal due to thermal shock generated by contact between the seed crystal P and the silicon melt M. The neck portion P1 is formed by this necking. The neck portion P1 is generally required to have a diameter of 3 to 4 mm and a length of 30 to 40 mm or more.

In addition, as a process after the start of pulling, after necking is completed, a crown process for expanding the crystal to the diameter of the straight body part, a straight body process for growing a single crystal as a product, and a single crystal diameter after the straight body process are gradually reduced. The tail process is performed.
A method for producing a silicon single crystal using this CZ method is described in, for example, Patent Document 1.

  By the way, in the single crystal growth step, SiO gas is generated from the silicon melt M melted in the crucible 51. If the SiO gas condenses and solidifies on the side surface of the furnace body, it may fall into the crucible 51 and be mixed. In this case, there is a problem that the single crystal C is dislocated and its growth is hindered.

  Accordingly, in order to exhaust the SiO gas generated from the silicon melt M to the outside of the furnace body, the furnace body in which the crucible 51 is accommodated is conventionally an inert gas from the top to the bottom as shown in FIG. A gas flow of Ar gas G is formed.

That is, Ar gas G supplied from above the crucible 51 flows toward the silicon melt M through the radiation shield 53 for shielding radiant heat, and is then led out of the crucible along the outside of the radiation shield 53. The The Ar gas led out of the crucible flows downward between the crucible 51 and the heater 52 and is exhausted from an exhaust port 54 provided on the bottom surface of the furnace body.
According to the gas flow thus formed, since the Ar gas G passes over the surface of the silicon melt M, the SiO gas generated from the melt M can be exhausted out of the furnace body together with the Ar gas G. .
JP-A-2005-97049

Conventionally, as described above, the SiO gas generated from the silicon melt M flows between the heater 52 and the crucible 51 together with the Ar gas G by the gas flow of the Ar gas G formed in the furnace body. Exhausted out of the furnace body.
However, since the heater 52 generates heat at, for example, 1500 ° C. or more during single crystal growth, the SiO gas flowing together with the Ar gas and the carbon forming the heat generating portion of the heater 52 may chemically react and the carbon may be eroded. was there. That is, there is a problem in that the heater heat generating portion is thinned and is further changed to SiC to shorten the life of the heater 52.

Further, when the heater heat generating portion is thinned, there is a problem that the oxygen concentration in the single crystal fluctuates due to fluctuations in the heater heat generation distribution over time, causing variations.
In addition, CO gas is generated by the reaction between carbon and SiO gas, and this is taken into the single crystal, increasing the carbon concentration in the single crystal and causing quality deterioration.

  The present invention has been made under the circumstances as described above. In the single crystal pulling apparatus, the adverse effect of the SiO gas generated from the silicon melt on the heater heating portion is suppressed, and the life of the heater is improved. An object of the present invention is to provide a single crystal pulling apparatus capable of realizing high quality crystal.

  In order to solve the above-described problems, a single crystal pulling apparatus according to the present invention includes a crucible in a furnace body and a heater provided around the crucible, and raw silicon in the crucible is heated by the heater. In a single crystal pulling apparatus that melts a single crystal from the crucible by the Czochralski method, a first gas supply means for supplying an inert gas from above the crucible, and an inert gas from below the heater A second gas supply means for supplying gas; and an exhaust means for exhausting the inert gas from the furnace through an exhaust port provided above the heater, and the exhaust gas supplied by the first gas supply means. The active gas is introduced into the crucible from above the crucible and exhausted from the exhaust port above the heater, and the inert gas supplied by the second gas supply means is connected to the heater and the front gas. Characterized in that is exhausted from the exhaust port of the heater upward flows between the crucible upward.

  By comprising in this way, a gas flow can be formed so that the inert gas with SiO gas generated from the silicon melt may not contact the heater. Therefore, it is possible to suppress the adverse effect of the SiO gas on the heater heat generating part, improve the life of the heater, and improve the quality of the single crystal.

In addition, an upper portion and a lower portion are provided so as to surround the periphery of the single crystal, and a radiation shield that shields radiant heat to the single crystal is provided. It is desirable to be placed between the molten liquid surface.
By providing the radiation shield in this way, the flow of the inert gas supplied from above by the first gas supply means can be rectified, and the SiO gas generated from the silicon melt can be efficiently exhausted. .

Further, it is desirable that the flow rate of the inert gas supplied by the first gas supply means is at least twice the flow rate of the inert gas supplied by the second gas supply means.
By controlling the flow rate of the inert gas in this way, it is possible to suppress the occurrence of turbulent flow due to collision of the respective gas flows.

  According to the present invention, in a single crystal pulling apparatus, the adverse effect of the SiO gas generated from the silicon melt on the heater heat generating part can be suppressed, and the life of the heater can be improved and the quality of the single crystal can be improved. A crystal pulling apparatus can be obtained.

Embodiments of a single crystal pulling apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a single crystal pulling apparatus 1 according to the present invention.
This single crystal pulling apparatus 1 includes a furnace body 2 formed by superposing a pull chamber 2b on a cylindrical main chamber 2a, a quartz glass crucible 3 provided in the furnace body 2, and a quartz glass crucible 3 A heater 4 for melting the loaded semiconductor raw material (raw material silicon) M and a pulling mechanism 5 for pulling up the single crystal C to be grown are provided. The pulling mechanism 5 includes a winding mechanism 5a driven by a motor and a pulling wire 5b wound up by the winding mechanism 5a, and a seed crystal P is attached to the tip of the wire 5b.

Further, in the main chamber 2a, an upper portion and a lower portion are formed so as to surround the periphery of the single crystal C above and in the vicinity of the quartz glass crucible 3, and an extra portion from the heater 4 or the like is added to the growing single crystal C. A radiation shield 6 is provided to prevent radiant heat from being applied.
The lower end of the shield is positioned between the silicon melt surface and the crucible upper end in the crucible 3 in order to rectify the gas flow in the furnace body 2, and the distance dimension between the melt surface ( The gap) is set to a predetermined distance according to desired characteristics of the single crystal to be grown.
Further, a heat insulating material 20 for improving the thermal efficiency is provided between the heater 4 and the main chamber 2a.

Further, an inert gas first supply port 13 for supplying Ar gas, which is an inert gas, into the furnace body 2 is provided at the upper portion of the pull chamber 2b.
An Ar gas source 17 is connected to the inert gas first supply port 13 via a valve 14 so that Ar gas is introduced into the furnace body 2 from above the pull chamber 2b by opening the valve 14. Has been made. That is, the first gas supply means is constituted by the inert gas first supply port 13, the valve 14, and the Ar gas source 17.

Further, on the peripheral surface of the main chamber 2 a below the heater 4, a plurality of inert gas second supply ports 15 for supplying Ar gas G into the furnace body 2, similarly to the inert gas first supply port 13. Are evenly provided along the circumferential surface of the chamber.
An Ar gas source 17 is connected to the inert gas second supply port 15 via a valve 16, and Ar gas is introduced into the furnace body 2 from the lower part of the main chamber 2 a by opening the valve 16. It is made like that. That is, the second gas supply means is constituted by the inert gas second supply port 15, the valve 16, and the Ar gas source 17.

Further, the peripheral surface of the main chamber 2 a above the heater 4 is provided with a plurality of exhaust ports 18 evenly along the peripheral surface of the chamber, and an exhaust pump 19 as an exhaust means is connected to the exhaust port 18. Yes.
That is, when the exhaust pump 19 is driven and the valves 14 and 16 are opened, Ar gas G is supplied into the furnace body 2 from the inert gas first supply port 13 and the inert gas second supply port 15, Each gas flow is formed and exhausted from the exhaust port 18.

  The gas flow rate from the inert gas first supply port 13 is adjusted by controlling the degree of opening and closing of the valve 14 and the suction strength of the exhaust pump 19, and the gas flow rate from the inert gas second supply port 15 is adjusted. The adjustment is made by controlling the degree of opening and closing of the valve 16 and the suction strength of the exhaust pump 19.

  As shown in FIG. 1, the single crystal pulling apparatus 1 includes a heater control unit 9 that controls the amount of power supplied to the heater 4 that controls the temperature of the silicon melt M, and a motor 10 that rotates the quartz glass crucible 3. And a motor control unit 10a for controlling the rotational speed of the motor 10. Furthermore, a lifting device 11 for controlling the height of the quartz glass crucible 3, a lifting device control unit 11a for controlling the lifting device 11, a wire reel rotating device control unit 12 for controlling the pulling speed and the number of rotations of the grown crystal, It has. These control units 9, 10a, 11a, 12 and the valves 14, 16 and the exhaust pump 19 are connected to an arithmetic control device 8b of the computer 8.

In the single crystal pulling apparatus 1 configured as described above, the raw material silicon M is first loaded into the quartz glass crucible 3, and based on the program stored in the storage device 8a of the computer 8, the crystal growth process is performed as follows. Is started.
First, the heater control unit 9 is operated according to a command from the arithmetic and control unit 8b to heat the heater 4, and the raw material silicon M of the quartz glass crucible 3 is melted.

Further, the valves 14 and 16 are opened by a command from the arithmetic and control unit 8b, and the exhaust pump 16 is driven to form an Ar gas flow in the furnace body 2.
Further, the motor control unit 10a, the lifting device control unit 11a, and the wire reel rotation device control unit 12 are operated by the command of the arithmetic control device 8b, the quartz glass crucible 3 is rotated, and the winding mechanism 5a is operated. Then the wire 5b is lowered. Then, the seed crystal P attached to the wire 5b is brought into contact with the silicon melt M, and necking for melting the tip of the seed crystal P is performed to form the neck portion P1.

  Thereafter, the pulling conditions are adjusted by parameters of the power supplied to the heater 4 and the single crystal pulling speed (usually a speed of several millimeters per minute) according to the command of the arithmetic control device 8b, and the crown process, the straight body process, the tail part A single crystal pulling step such as a step is sequentially performed.

In this single crystal pulling step, the Ar gas flow is formed as shown in FIG.
That is, Ar gas G introduced from the inert gas first supply port 13 is introduced into the crucible 3 from above the radiation shield 6, passes over the surface of the silicon melt M, and then generated from the melt M. It is led out of the crucible 3 along the outer side of the radiation shield 6 with the SiO gas which does.
Here, as described above, the lower end of the radiation shield 6 is positioned between the silicon melt surface and the upper end of the crucible, and therefore the Ar gas G supplied from the inert gas first supply port 13. The flow is rectified and the SiO gas is efficiently led out of the crucible 3.
The Ar gas G led out of the crucible 3 (with SiO gas) is exhausted from the exhaust port 18 provided above the crucible 3 and the heater 4.

  The Ar gas G introduced from the inert gas second supply port 15 flows upward between the crucible 3 and the heater 4 and is exhausted from the exhaust port 18. That is, a gas flow is formed between the crucible 3 and the heater 4 upward from below, so that the SiO gas generated from the silicon melt M does not come into contact with the heater 4.

  The flow rate of Ar gas G introduced downward from the inert gas first supply port 13 at the top of the furnace body 2 is introduced upward from the inert gas second supply port 15 at the bottom of the furnace body 2. By setting the flow rate of Ar gas G to be twice or more, generation of turbulent flow due to collision of the respective gas flows can be suppressed.

  As described above, according to the embodiment of the present invention, it is possible to form a gas flow so that the Ar gas G accompanied by the SiO gas generated from the silicon melt does not contact the heater 4. Therefore, it is possible to suppress the adverse effect of the SiO gas on the heater heat generating part, improve the life of the heater, and improve the quality of the single crystal.

  Next, the single crystal pulling apparatus according to the present invention will be further described based on examples. In this example, the effect was verified by actually performing an experiment using the single crystal pulling apparatus having the configuration described in the above embodiment.

In this experiment, a silicon single crystal having a diameter of 12 inches was grown in a crucible having an inner diameter of 32 inches, and the thickness reduction of the heater was verified.
In addition, the gas flow rate supplied from above the radiation shield into the crucible was set to three times the gas flow rate supplied from below the heater.

The result of this experiment is shown in the graph of FIG. As shown in this graph, it is confirmed that the heater thinning amount is reduced to about one-sixth of the result of the comparative example performed by the conventional configuration, and the life of the heater is improved. It was.
In addition, the variation in oxygen concentration of the manufactured single crystal was reduced, and a decrease in the carbon concentration in the single crystal was confirmed.

  From the experimental results of the above examples, by using the single crystal pulling apparatus of the present invention, the adverse effect on the heater heat generating part due to the SiO gas generated from the silicon melt is suppressed, the life of the heater is improved, the high single crystal is increased. It was confirmed that quality could be realized.

  The present invention relates to a single crystal pulling apparatus that pulls a single crystal by the Czochralski method, and is suitably used in the semiconductor manufacturing industry and the like.

FIG. 1 is a block diagram schematically showing the configuration of a single crystal pulling apparatus according to the present invention. FIG. 2 is a view showing a gas flow of an inert gas in the furnace of the single crystal pulling apparatus of FIG. FIG. 3 is a diagram for explaining a pulling method using the conventional CZ method. FIG. 4 is a diagram for explaining formation of a neck portion in a pulling method using a conventional CZ method. FIG. 5 is a diagram showing a gas flow of an inert gas in a conventional furnace body. FIG. 6 is a graph showing the results of the example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Furnace body 2a Main chamber 2b Pull chamber 3 Quartz glass crucible (crucible)
4 Heater 5 Pulling Mechanism 6 Radiation Shield 8 Computer 8a Storage Device 8b Arithmetic Storage Device 13 Inert Gas First Supply Port (First Gas Supply Means)
14 Valve (first gas supply means)
15 Inert gas second supply port (second gas supply means)
16 valve (second gas supply means)
17 Ar gas supply source (first gas supply means, second gas supply means)
18 Exhaust port 19 Exhaust pump (exhaust means)
C single crystal G Ar gas (inert gas)
M Raw material silicon, Silicon melt P Seed crystal P1 Neck

Claims (3)

A single crystal puller comprising a crucible in the furnace body and a heater provided around the crucible, melting the raw silicon in the crucible by heating the heater, and pulling the single crystal from the crucible by the Czochralski method. In the upper device,
A first gas supply means for supplying an inert gas from above the crucible, a second gas supply means for supplying an inert gas from below the heater, and an exhaust port provided above the heater. An exhaust means for exhausting the active gas out of the furnace body,
The inert gas supplied by the first gas supply means is introduced into the crucible from above the crucible, exhausted from the exhaust port above the heater, and supplied by the second gas supply means. The single crystal pulling apparatus, wherein the inert gas flows upward between the heater and the crucible and is exhausted from the exhaust port above the heater. An upper part and a lower part are formed so as to surround the periphery of the single crystal, and includes a radiation shield that shields radiation heat to the single crystal,
2. The single crystal pulling apparatus according to claim 1, wherein the lower end of the radiation shield is installed in the crucible so as to be positioned between the upper end of the crucible and the silicon melt surface.   The flow rate of the inert gas supplied from the first gas supply means is at least twice the flow rate of the inert gas supplied from the second gas supply means. The single crystal pulling apparatus according to claim 2.

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