JP2952733B2 - Silicon single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a semiconductor single crystal by the Czochralski method, and a silicon for controlling the concentration of oxygen contained in the single crystal by blowing an inert gas onto a solid-liquid interface when pulling the single crystal. The present invention relates to a method for producing a single crystal.

[0002]

2. Description of the Related Art A Czochralski method (hereinafter referred to as a CZ method) for pulling a columnar single crystal from a raw material melt in a crucible is used as one of the methods for manufacturing a silicon single crystal which is a basic material of a semiconductor integrated circuit. Have been. In the CZ method, a high-purity polycrystalline silicon is filled in a quartz crucible installed in a main chamber of a single crystal manufacturing apparatus, and the polycrystalline silicon is heated and melted by a heater provided on the outer periphery of the crucible. The attached seed crystal is immersed in the melt, and while rotating the seed chuck and the crucible in the same or opposite directions, the seed chuck is pulled up at a seed moving speed of 2 mm / min or less industrially to grow a silicon single crystal. In such a silicon single crystal pulling step, silicon oxide (SiOx; x
= 1-2) and amorphous silicon evaporates. These vapors are cooled at the inner wall of the upper chamber of the water-cooled pulling furnace or at the upper end of the crucible, and are precipitated in a powdery or acicular shape, and often fall to the surface of the melt during the pulling process to inhibit single crystallization. In addition, heavy metal vapor mainly generated from the graphite crucible also contaminates the melt.

In pulling a single crystal by the CZ method,
By placing a radiation screen made of a metal material or a material having a metal surface that can reflect infrared rays above the crucible, single crystallization can be promoted, pulling speed can be increased, and carbon in the single crystal can be increased. It is known that the concentration is reduced (see Japanese Patent Publication No. 57-40119).
In addition, by pulling the single crystal through a multi-layered tapered body composed of a heat-resistant heat insulating material surface layer coaxially surrounding the pulled single crystal, silicon oxide is prevented from being precipitated and radiant heat from the silicon melt surface and the crucible wall surface is prevented. It is known that the single crystal is cooled by an argon gas flowing inside the tapered tubular body to increase the pulling speed (see JP-A-62-138384). Others
By providing a radiant screen of an inverted conical adiabatic multilayer structure surrounding the pulled single crystal above the crucible, it is possible to prevent silicon oxide evaporated from the silicon melt surface from depositing in the CZ furnace and falling onto the melt surface. It is known to prevent this (see JP-A-62-138386).

[0004]

When a radiant screen capable of reflecting infrared rays, a radiant screen having a heat insulating multilayer structure, or a tapered tubular body having a multilayer structure is installed above a crucible, single crystallization is promoted and pulling up is performed. This has the effect of increasing the speed and suppressing the carbon concentration in the single crystal. However, it is not possible to completely suppress silicon oxide and amorphous silicon evaporating from the melt surface, or heavy metal vapor generated from the graphite crucible, and silicon oxide, amorphous silicon, heavy metal, and graphite deposited on the inner wall of the upper chamber or on the radiation screen. It is also impossible to prevent a problem that dust such as falls on the melt surface and hinders single crystallization. Further, a silicon single crystal manufactured using a conventional single crystal manufacturing apparatus has a large variation in the oxygen concentration in the axial direction of the ingot and has poor reproducibility. The present invention has been made in view of the above-mentioned conventional problems, and promotes single crystallization by preventing the dust such as the silicon oxide and heavy metal from falling onto the melt surface, and at the same time promotes the axis of the single crystal ingot. It is an object of the present invention to provide a silicon single crystal manufacturing apparatus capable of making the oxygen concentration in the direction uniform.

[0005]

In order to achieve the above object, a method for manufacturing a silicon single crystal according to the present invention comprises a step of immersing a seed crystal in a melt in a crucible and pulling the seed crystal around the lower periphery of the silicon single crystal and pulling the gas. A method for producing a silicon single crystal, comprising: an annular gas injection pipe provided with a blowout hole, wherein an inert gas is injected from the gas blowout hole during pulling up of the silicon single crystal to produce a silicon single crystal. A method is used in which the amount of oxygen generated from the melt surface is indirectly controlled by controlling the injection amount of the inert gas to be sprayed toward the liquid surface while controlling the injection amount toward the liquid surface.

[0006]

According to the above arrangement, the amount of oxygen generated from the melt surface is indirectly controlled by controlling the injection amount of the inert gas injected toward the melt surface. Therefore, the oxygen concentration in the melt is controlled, and the oxygen concentration in the single crystal to be pulled is indirectly controlled. That is,
The oxygen concentration in the axial direction of the single crystal ingot is made uniform.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a silicon single crystal manufacturing apparatus and a manufacturing method according to the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of a silicon single crystal manufacturing apparatus, and FIG. 2 is an enlarged partial cross-sectional view of a portion P in FIG. In these figures, 1 is a main chamber, 1a is an upper chamber, and a quartz crucible 3 is fitted to a graphite crucible 2 installed in the main chamber 1, and a silicon melt 4 stored in the quartz crucible 3 Silicon single crystal 5
Has been raised. 6 is a crucible shaft, 7 is a graphite heater, and 8 is a heat insulating cylinder.

The gas injection tube 9 is a tungsten tube surrounding the silicon single crystal 5 concentrically, and its cross section is shown in FIG.
It is square as shown in FIG. A plurality of gas blowing holes 9a, which open toward the outer periphery of the silicon single crystal 5, are formed in the inner peripheral surface of the gas injection pipe 9 at equal pitches in the radial direction, and the gas blowing holes obliquely downward are formed on the lower surface. 9b and downward gas blowing holes 9c are respectively formed on the circumference at equal pitches. The radial gas discharge holes 9a are directed to the outer periphery of the single crystal 5, the obliquely downward gas discharge holes 9b are directed to the solid-liquid interface between the single crystal 5 and the silicon melt 4, and the downward gas discharge holes 9c. Is silicon melt 4
Are gas blowing holes for blowing an inert gas to the surface of each. The lower end of at least two gas supply pipes 10 made of tungsten is connected to the upper surface of the gas injection pipe 9, and the upper end of the gas supply pipe 10 is opened to the outside at the upper part of the upper chamber 1 a and connected to an inert gas pipe (not shown). It is connected. The gas supply pipe 10 is a gas injection pipe 9
And has a function of fixing the gas injection pipe 9 at a predetermined position, and a lower surface of the gas injection pipe 9
The gas supply pipe 10 is fixed at a position where the distance h from the surface of the silicon melt 4 is 10 to 20 mm. In this embodiment, the cross section of the gas injection pipe 9 is square, but the present invention is not limited to this, and the cross section may be circular or rectangular. Alternatively, the radial gas blowing holes 9a may be provided slightly upward from the horizontal, and the downward gas blowing holes 9c may be provided slightly outward. Further, the upper end of the gas supply pipe 10 may not be fixed to the upper chamber 1a, but may be movable up and down together with the gas injection pipe 9.

Next, a method for manufacturing a silicon single crystal using the apparatus for manufacturing a silicon single crystal provided with the gas injection pipe 9 will be described, particularly a method for controlling the oxygen concentration. In pulling up the silicon single crystal, an argon gas is introduced into the furnace as an inert gas from above the upper chamber 1a, and at the same time, an argon gas is also introduced into the gas injection pipe 9 via the gas supply pipe 10. At this time, the flow rate of the argon gas introduced into the gas injection pipe 9 is, for example, about ３ of the flow rate of the argon gas introduced from above the upper chamber 1a.
It is. The argon gas blown toward the solid-liquid interface from the gas blowing holes 9b of the gas injection pipe 9 flows upward along the silicon single crystal 5 from the solid-liquid interface, and flows from the silicon single crystal 5 to the quartz crucible 3. And a flow toward the inner wall of the body. The argon gas blown out from the gas blow-out hole 9a of the gas injection pipe 9 was
And a flow rising along the silicon single crystal 5 is formed, and the argon gas blown out from the gas blowing holes 9c is blown onto the surface of the melt 4 and then flows toward the inner wall of the quartz crucible 3. . Thus, the gas injection pipe 9
Since a fresh inert gas is always supplied to the solid-liquid interface and the silicon single crystal 5 and its surroundings from each gas blowing hole of
It is possible to eliminate dust such as silicon oxide and heavy metals that fall toward the melt surface from above or from the side of the solid-liquid interface, and to prevent dust from adhering to the silicon single crystal 5, the gas injection pipe 9 and the gas supply pipe 10. To prevent.

By adjusting the flow rate of the argon gas introduced into the gas injection pipe 9 through the gas supply pipe 10, the argon gas blown out from the gas blowing holes 9 b and 9 c and flowing along the surface of the silicon melt 4. The flow rate changes. And the silicon melt 4
The amount of oxygen generated from the surface can be controlled. This is based on controlling the oxygen partial pressure and the degree of vacuum at the gas-liquid interface near the silicon melt. Silicon melt 4
Controlling the amount of oxygen generated from the surface of the melt 4
The oxygen concentration in the silicon single crystal can be controlled, and the oxygen concentration in the silicon single crystal is indirectly controlled. The ratio between the flow rate of the argon gas introduced into the gas injection pipe 9 and the flow rate of the argon gas introduced from above the upper chamber 1a, the amount of adjustment of the flow rate of the argon gas introduced into the gas injection pipe 9, and the adjustment timing are determined by the single crystal manufacturing apparatus. It shall be determined individually based on specifications, required quality of single crystal, etc.

The above gas injection tube was attached to a single crystal manufacturing apparatus, and a silicon single crystal having a diameter of 6 inches was pulled up. The diameter of the quartz crucible used at this time is 16 inches, and the charge amount of the silicon nugget is 45 kg. The distance between the melt surface and the lower surface of the gas injection tube was set to 20 mm, and the pressure in the pulling furnace was maintained at 10 mbar. 3 from the top of the pull chamber
An argon gas of 0 liter / min was introduced, and an argon gas of 10 liter / min was introduced into the gas supply pipe. In this manner, a silicon single crystal having a length of 800 mm was obtained. The oxygen concentration of this single crystal was lower by 1.0 × 10 ¹⁷ atoms / cc than when the gas injection tube was not mounted. The difference in oxygen concentration between the top side and the bottom side of the single crystal was 1.5 × 10 ¹⁷ atoms / cc.

In the above method, the silicon single crystal was pulled by changing the flow rate of the argon gas blown from the gas injection tube. That is, the flow rate of the argon gas in the initial stage of the pulling was 10 liter / min, and the flow rate was gradually reduced to 3 liter / min in the latter stage of the pulling. The difference in oxygen concentration between the top side and the bottom side of the obtained single crystal was 0.8 × 10 ¹⁷ atoms / cc, and a substantially uniform oxygen concentration distribution could be obtained in the axial direction.

As described above, according to this embodiment, C
In a silicon single crystal manufacturing apparatus using the Z method, an inert gas injection mechanism is provided at and near the solid-liquid interface, and the inert gas is directly blown onto the solid-liquid interface, the melt surface, and the outer peripheral surface of the single crystal when pulling the single crystal. Therefore, it is possible to prevent silicon oxide and heavy metals from adhering to the outer surface of the single crystal, and to discharge these impurity gases near the outer surface of the single crystal to the outside of the chamber. Accordingly, since dust such as silicon oxide and heavy metal that falls onto the melt surface from the upper inner wall of the upper chamber or the graphite crucible can be eliminated, polycrystallization, which has been a problem, can be prevented.
A single crystal can be manufactured efficiently. Further, since the cooling of the growing single crystal can be accelerated, the production efficiency of the silicon single crystal can be industrially improved. Further, according to the present embodiment, since the oxygen concentration in the melt can be controlled, it is possible to produce a high-quality silicon single crystal having a uniform oxygen concentration.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of a silicon single crystal manufacturing apparatus provided with a gas injection tube.

FIG. 2 is an enlarged partial sectional view of a part P in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main chamber 1a Upper chamber 4 Silicon melt 5 Silicon single crystal 9 Gas injection pipe 9a, 9b, 9c Gas blowing hole 10 Gas supply pipe

Claims (1)

(57) [Claims] 1. A has a melt seed crystal silicon pulled by immersing single crystals annular gas injection pipe provided with a lower periphery of the surrounds and the gas blow openings in the crucible, a gas during the pulling of the silicon single crystal Silicon single crystal manufacturing method to produce silicon single crystal by injecting inert gas from blow-out hole
In the method , the amount of oxygen generated from the melt surface is indirectly controlled by injecting the inert gas toward the melt surface and controlling the amount of the inert gas injected toward the melt surface. A method for producing a silicon single crystal.