JPH09202686A - Apparatus for producing single crystal and production of single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both a production apparatus suitable for pulling up a single crystal having neither dislocation nor carbon contamination, excellent in low-carbon concentration characteristics, without impairing a precise control of oxygen concentration in the single crystal, by straightening an inert gas flow in the apparatus and a method for producing the single crystal. SOLUTION: (1) In this apparatus 1 for producing a single crystal equipped with a crucible 2 for housing a melt, a heater 3 for heating the melt, a pulling up means for growing the single crystal, a radiant heat shielding screen 8 for enclosing the circumference of a pulling up zone of the single crystal, a metal chamber 9 for housing these members and a means for supplying an inert gas, a straightening inner cylinder 21 to be laid outside the crucible 2 and inside or outside of the heater 3 and a means 22 for supplying the inert gas to a space formed by the straightening inner cylinder and the metal chamber are installed to give the objective apparatus for producing the single crystal. In this method for producing the single crystal by a Czochralski method using this production apparatus, the straightening inner cylinder is installed outside the crucible and inside or outside the heater and the inner gas is newly supplied to the space formed by the straightening inner cylinder and the metal chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a single crystal for semiconductors such as silicon and a method for producing a single crystal using the apparatus. More specifically, the present invention eliminates carbon contamination from graphite parts and reduces carbon concentration. The present invention provides a manufacturing apparatus and a manufacturing method suitable for manufacturing a single crystal having excellent characteristics without dislocation.

[0002]

Single crystal produced by the Prior Art Czochralski method, in order to foster Te pulled from a silicon melt in the quartz crucible, the grown crystals more oxygen eluted from crucible quartz (SiO ₂₎ Contains. For this reason, IC and L
The SI manufacturing process is characterized in that slip and warp are less likely to occur even if it is repeatedly subjected to heat treatment.
Furthermore, the oxygen precipitates inside also have a function of forming a high-density defect layer by heat treatment at around 1000 ° C. and reducing impurities existing in the surface region of the wafer (so-called intrinsic gettering). Due to such characteristics, the Czochralski method is widely used as an industrial mass production method for single crystals for semiconductors.

In pulling a single crystal by the Czochralski method, the pulling speed is closely related to the temperature gradient in the pulling direction of the pulled single crystal, and the pulling speed is increased by increasing the temperature gradient. You can For this reason, in the case of industrial mass production, a screen is placed so as to surround the circumference of the single crystal to be pulled, the radiant heat from the crucible, the heater and the melt is blocked, and the temperature in the pulling direction of the single crystal is increased. A method of increasing the gradient is adopted.

FIG. 4 is a vertical sectional view of an apparatus for manufacturing a silicon single crystal by the Czochralski method by disposing a radiant heat blocking screen (hereinafter, simply referred to as "radiant screen"). Usually, the crucible 2 used for producing a silicon single crystal has a double structure, and is composed of an inner quartz crucible 2a and an outer graphite crucible 2b. A heater 3 made of graphite is provided outside the crucible 2, and a silicon melt 4 melted by the heater is contained in the crucible 2. A pulling wire 5 is used as a pulling means for pulling a single crystal, and a seed crystal 6 is attached to the tip thereof. The lower end of the seed crystal 6 is brought into contact with the surface of the melt 4 and pulled up to grow the single crystal 7 at the lower end. At this time, a radiation screen 8 is arranged on the melt 4 so as to surround the silicon single crystal. Radiant heat from the heater 3 and the melt 4 is blocked by the radiant screen 8,
The temperature gradient of the pulled single crystal 7 becomes large. These parts and members are housed in the metal chamber 9 and constitute the single crystal manufacturing apparatus 1 as a whole.

During the pulling of the single crystal, a high-purity argon gas is constantly supplied as an inert gas from the central portion above the metal chamber 9, and a gas flow 31 (indicated by an arrow in the figure).
Is formed. The gas stream 31 is generated by the reaction of silicon monoxide (SiO 2) evaporated from the surface of the silicon melt 4 stored in the crucible and this silicon monoxide with a high temperature graphite member such as the heater 3 or the graphite crucible 2b. Along with carbon monoxide (CO) and the like, it flows downward through the inner and outer peripheral surfaces of the heater 3 and is discharged from the discharge port 10. At this time, turbulent flow, stagnation, that is, stagnation or swirling of the gas flow is likely to occur at a portion (for example, a portion A in the figure) where the gas flow extremely changes in the metal chamber.

When turbulence or retention occurs in the argon gas flow 31 formed in the metal chamber 9, or when the argon gas flow is insufficient, silicon monoxide (SiO) precipitates radiate. It adheres to the lower surface of the screen 8 and the side surface of the metal chamber 9 in the form of layers or blocks. The fine particles or lumps of precipitated silicon monoxide fall on the surface of the melt 4, and are taken into the crystal growth interface, causing dislocations in the crystal. Also, carbon monoxide (CO) is not properly discharged, stays in the metal chamber and contaminates the silicon melt, mixes in the single crystal to increase the carbon concentration, and causes crystal defects in the single crystal. It becomes a factor to induce.

As a countermeasure for these problems, a method of increasing the flow rate of argon gas to increase the gas flow velocity is conceivable, but there is a certain limit to the increase of gas flow rate. Generally, the flow velocity Vg of the argon gas depends on the gas supply pressure Pg, the gas flow rate Qg, the gas passage space cross-sectional area Ag, and the furnace pressure Pf, and is represented by the following equation (A).

Vg = (Qg / Ag) × (Pg / Pf) (A) The action of discharging silicon monoxide or carbon monoxide by increasing the flow rate Qg of the argon gas to accelerate the gas flow rate Vg. Is exerted, it is possible to prevent these from being mixed in the melt 4. However, regarding the oxygen concentration of the single crystal, in order to effectively perform the above-mentioned intrinsic gettering, it is necessary to precisely control the oxygen concentration in the single crystal within a certain range. It is strongly affected by the gas distribution. That is, in FIG.
When the gas flow rate Qg is increased, the flow velocity Vg in the gap between the lower end of the radiant screen 8 and the surface of the melt 4 also increases, and at the same time, the partial velocity difference in the circumferential direction increases, so that the surface temperature of the melt 4 increases. Further, the convection in the melt 4 is changed, and it becomes difficult to precisely control the oxygen concentration in the crystal within the above-mentioned fixed range with good reproducibility.

Further, if the gas flow rate Qg is increased above a certain flow rate, the flow velocity Vg in the gap between the lower end of the radiant screen 8 and the surface of the melt 4 becomes too high, causing vibration on the surface of the melt 4. In some cases, a dislocation-free single crystal cannot be pulled up. From this point,
To adopt a method of increasing the flow rate Qg of argon gas in order to sufficiently discharge silicon monoxide and carbon monoxide,
There are certain restrictions on the assumption that oxygen concentration control and dislocation-free pulling required for a semiconductor single crystal are ensured.

[0010]

As described above, the conventional apparatus and method for producing a single crystal are capable of precisely controlling the oxygen concentration in the crystal, which is required for a single crystal for a semiconductor.
The problem is that it is difficult to produce low-carbon-concentration single crystals by sufficiently discharging silicon monoxide and carbon monoxide generated in the furnace, preventing dislocation-free pulling of crystals and carbon contamination from graphite parts. Had.

In view of this problem, the present invention rectifies the flow of an argon gas to obtain a low carbon concentration characteristic without dislocation and without impairing the precise controllability of the oxygen concentration in the crystal. An object of the present invention is to provide a manufacturing apparatus and a manufacturing method suitable for pulling an excellent single crystal.

[0012]

SUMMARY OF THE INVENTION The gist of the present invention is a silicon single crystal manufacturing apparatus of the following (1) and a single crystal manufacturing method of the following (2) using the apparatus.

(1) As shown in FIG. 1, a crucible 2 for containing a raw material melt of a single crystal to be grown, a heater 3 for heating the melt, and a seed crystal on the surface of the melt 4 in the crucible. 6, a pulling means 5 for growing a single crystal by contacting with each other, a radiant heat shielding screen 8 surrounding the pulling area of the single crystal, a metal chamber 9 for accommodating each member, and an inert gas from above the metal chamber. In a single crystal manufacturing apparatus 1 including a means for supplying gas, a rectifying inner cylinder 21 arranged outside the crucible and inside or outside the heater, and the rectifying inner cylinder and the metal chamber are formed. A device for producing a single crystal, characterized in that a means for newly supplying an inert gas to the space is provided.

However, FIG. 1 shows a case where the rectifying inner cylinder 21 is arranged inside the heater 3.

(2) A crucible for containing a raw material melt of a single crystal to be grown, a heater for heating the melt, and a puller for growing a single crystal by bringing a seed crystal into contact with the surface of the melt in the crucible A manufacturing apparatus comprising: a means, a radiant heat shielding screen surrounding a pulling region of a single crystal, a metal chamber for accommodating each member, and a means for supplying an inert gas from the upper part of the metal chamber are used. In the method for producing a single crystal by the Czochralski method, a rectifying inner cylinder is arranged outside the crucible and inside or outside the heater, and a new inert space is formed in a space formed by the rectifying inner cylinder and the metal chamber. A method for producing a single crystal, which comprises supplying a gas.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A single crystal production apparatus and a production method of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view showing a single crystal production apparatus of the present invention. Reference numeral 2 in the figure is a crucible, which has a double structure including a quartz crucible 2a on the inner side and a graphite crucible 2b on the outer side, and is installed on the crucible support shaft 2c. The metal chamber 9 constituting the appearance of the manufacturing apparatus 1 is a cylindrical vacuum container arranged around the pulling axis of the single crystal, and the crucible 2 is arranged at the central position thereof, and the crucible 2 is surrounded on the outer periphery thereof. A heater 3 for heating the melt 4 in the crucible is provided.
On the other hand, above the crucible 2, a pulling means 5 (for example, a pulling wire) is vertically rotatably and vertically provided from the center of the upper part of the metal chamber 9, and a seed crystal 6 is attached to the lower end thereof. The seed crystal 6 rises while being rotated by the pulling means 5, and the single crystal 7 grows at the lower end portion which is the contact surface with the melt 4.

At this time, in order to accelerate the pulling speed of the single crystal and promote efficient growth, the radiation screen 8 is arranged above the crucible 2 and surrounding the single crystal to be pulled, and the crucible is provided. 2, the radiant heat applied to the single crystal from the heater 3 and the melt 4 is blocked. Further, high-purity argon gas is constantly supplied from the upper part of the metal chamber 9 for adjusting the atmosphere of the metal chamber 9 and for discharging the precipitate. The supplied argon gas constitutes the gas flow 31, and as described above, a portion of the metal chamber 9 where the gas flow 31 changes extremely, for example, the radiation screen 8
At the lower portion of the gas and the upper portion of the crucible 2 and the heater 3, turbulent flow such as stagnation or swirl or retention is likely to occur in the gas flow 31.

In the present invention, in order to prevent the above-mentioned turbulent flow or retention of the gas flow 31, a thin-walled cylindrical rectifying inner cylinder 21 is arranged outside the crucible 2 and inside or outside the heater 3. Argon gas is newly supplied to the space formed by the rectifying inner cylinder 21 and the metal chamber 9.
It was decided to provide means for supplying through 22. By adopting such a configuration, it is possible to prevent turbulent flow and retention of the gas flow that are likely to occur at the above-mentioned portion.

FIG. 2 is a perspective view showing the structure of the rectifying inner cylinder. The upper side and the lower side of the rectifying inner cylinder are both main suction ports 23 supplied from the upper part of the metal chamber and serving as passage holes for the gas flow 31. An auxiliary suction port 24 is provided. The rectification inner cylinder 21 employed in the present invention has a cylindrical shape, and is arranged so as to be located outside the crucible 2 and inside or outside the heater 3, so that the rectification inner cylinder 21 and the metal chamber 9 are disposed.
A space is formed from and. That is, an annular space is formed on the outer circumference of the crucible 2.

Argon gas is newly supplied from the gas supply port 22 to the above space to form a gas flow 32 descending toward the discharge port 10. As long as the gas flow 32 secures a constant flow velocity, suction force is generated through the main suction port 23 and the auxiliary suction port 24. Therefore, the gas flow 31 supplied from the upper part of the metal chamber 9 in FIG. 1 and passing through the gap between the lower end of the radiation screen 8 and the surface of the molten liquid 4 passes through the main suction port 23 by the suction force of the gas flow 32. And is sucked into the space formed by the rectifying inner cylinder 21 and the metal chamber 9.

The gas flow 31 which is not sucked by the main suction port 23 but descends along the straightening inner cylinder is sucked from the sub suction port 24 and discharged from the discharge port 10.

Due to the suction action of the gas flow 32, it is possible to avoid the turbulent flow and retention of the gas flow 31 which are likely to occur in the lower portion of the radiation screen 8 without changing the gas flow 31 on the surface of the melt 4. Therefore, by disposing the rectifying inner cylinder shown in FIG. 2, a single crystal excellent in characteristics of low carbon concentration without dislocation and without carbon contamination is produced without impairing the precision controllability of oxygen concentration in the crystal. can do. Further, in the present invention, the rectifying inner cylinder 21 may be arranged inside or outside the heater 3, but in order to completely prevent carbon contamination from the graphite heater, it is arranged inside the heater 3. desirable.

The rectifying inner cylinder employed in the present invention is preferably made of graphite, and the surface thereof is desirably coated with silicon carbide (SiC). The reason why the rectifying inner cylinder is made of graphite is that it can be manufactured with high purity and there is little risk of contamination of the pulled crystal by heavy metals or the like. Further, if the surface is coated with silicon carbide (SiC), gas release from the pores of the graphite member is prevented, and reaction between silicon monoxide evaporated from the surface of the melt 5 and the graphite member is also prevented. be able to.

The argon gas used in the present invention may be supplied by any of the commonly used means. Liquid argon is used as a raw material and is supplied into the metal chamber after gasification.

[0026]

EXAMPLES The effects of the present invention will be specifically described based on examples.

(Inventive Example) A large-sized single crystal having a diameter of 8 inches was pulled by using the single-crystal manufacturing apparatus shown in FIG. A 22-inch (559 mm) outer diameter crucible was used to pull up an 8-inch diameter single crystal. The conditions were an initial charge of 100 kg, a pulling rate of 0.8 mm, a crystal rotation of 18 rpm, and a crucible rotation of 8 rpm to 16 rpm.
A single crystal having a weight of 95 kg was grown. At this time, the flow rate of argon gas in the metal chamber is always 10 to 50 liters.
It was supplied under the condition of / min.

The rectifying inner cylinder arranged in the apparatus has an outer diameter of 570 mm,
It had a cylindrical shape with a height of 700 mm and a thickness of 10 mm, and was arranged concentrically with the pulling shaft so as to be located outside the crucible and inside the heater. Further, in the space formed by the rectifying inner cylinder and the metal chamber, the flow rate of argon gas is 20 to 100 liter / m 2.
Supplied under in condition.

Comparative Example For comparison, a single crystal manufacturing apparatus shown in FIG. 4 was used to pull up a heavy single crystal having a diameter of 8 inches. The pulling conditions at this time were the same as in the case of the present invention, and the argon gas was supplied into the apparatus at a flow rate of 10 to 50 l / min from the upper part of the metal chamber.

(Comparison Results) FIG. 3 is a diagram showing distributions of oxygen concentration and carbon concentration in the single crystals pulled by the examples of the present invention and the comparative examples. The crystal solidification rate in the figure indicates the weight of the pulled single crystal / initial charge weight, and the crystal solidification rate 0 represents the top part of the crystal, and the closer the crystal solidification rate is to 1.0, the closer to the bottom part of the crystal. Is represented.

As is clear from FIG. 3, the oxygen concentration shows almost the same distribution in the present invention and the comparative example. This indicates that there was no difference in the amount of oxygen evaporated on the surface of the molten liquid. On the other hand, regarding the carbon concentration, in the comparative example, the concentration is remarkably increased with the increase of the crystal solidification rate, whereas in the present invention example, the concentration is low over the entire length of the single crystal, which shows excellent low carbon concentration characteristics. ing. Further, it has been confirmed that in the present invention example, the dislocation-free pulling is improved by about 20% as compared with the comparative example.

Further, as a comprehensive judgment method of oxygen concentration distribution, carbon concentration distribution and content of metal impurities in the single crystal, the lifetime of the pulled single crystal is measured by the micro PCD method (P type 4.5 to 6.0 Ωcm). Measured by
The result is 510.2 μsec in the comparative example, while
It is 615.5 μsec in the example of the present invention, and it can be seen that the example of the present invention exhibits excellent characteristics.

[0033]

According to the apparatus and method for producing a single crystal of the present invention, the flow of the inert gas in the pulling region of the single crystal is rectified without impairing the precision controllability of the oxygen concentration in the crystal. It is possible to produce a single crystal that is dislocation-free and has excellent characteristics of low carbon concentration without carbon contamination.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a single crystal manufacturing apparatus of the present invention.

FIG. 2 is a perspective view showing a structure of a straightening inner cylinder used in the present invention.

FIG. 3 is a diagram showing distributions of oxygen concentration and carbon concentration in pulled single crystals in Examples of the present invention and Comparative Examples.

FIG. 4 is a vertical cross-sectional view of a conventional single crystal manufacturing apparatus that is provided with a radiation screen and that manufactures a silicon single crystal by the Czochralski method.

[Explanation of symbols]

1 ... Single crystal manufacturing apparatus 2 ... Crucible, 2a ... Quartz crucible, 2b ... Graphite crucible, 2c
... crucible support shaft 3 ... heater, 4 ... melt, 5 ... pulling means (pulling wire) 6 ... seed crystal, 7 ... single crystal, 8 ... radiation screen,
9 ... Metal chamber 10 ... Discharge port 21 ... Straightening inner cylinder, 22 ... Gas supply port, 23 ... Main suction port,
24 ... Sub suction port 31, 32 ... Gas flow

Claims (2)

[Claims] 1. A crucible for containing a raw material melt of a single crystal to be grown, a heater for heating the melt, and a pulling means for growing a single crystal by bringing a seed crystal into contact with the surface of the melt in the crucible. And a radiant heat shielding screen surrounding the periphery of the pulling region of the single crystal, a metal chamber accommodating each member, and a single crystal manufacturing apparatus comprising means for supplying an inert gas from the upper part of the metal chamber, A rectifying inner cylinder arranged outside the crucible and inside or outside the heater, and means for newly supplying an inert gas to a space formed by the rectifying inner cylinder and the metal chamber are provided. A single crystal manufacturing apparatus characterized by the above. 2. A crucible for containing a raw material melt of a single crystal to be grown, a heater for heating the melt, and a pulling means for growing a single crystal by bringing a seed crystal into contact with the surface of the melt in the crucible. , A radiant heat shielding screen surrounding the pulling region of the single crystal, a metal chamber accommodating each of the members, and means for supplying an inert gas from the upper part of the metal chamber. In the method for producing a single crystal by the Larsky method, a rectifying inner cylinder is arranged outside the crucible and inside or outside the heater, and a new inert gas is newly provided in a space formed by the rectifying inner cylinder and the metal chamber. A method for producing a single crystal, which comprises: