JP2021088483A - Apparatus and method for manufacturing single crystal - Google Patents

Abstract

To provide an apparatus and method for manufacturing a single crystal by a FZ method, capable of uniformizing the in-plane distribution of resistivity of the single crystal as much as possible while stably installing a dopant supply pipe.SOLUTION: An apparatus 1 for manufacturing a single crystal comprises: an upper shaft 11 for rotatably and elevatably supporting a raw material rod 2; a lower shaft 13 for coaxially arranged with the upper shaft 11 and for rotatably and elevatably supporting a seed crystal 3 arranged below the raw material rod 2; an induction heating coil 20 for heating the raw material rod 2 to form a molten zone 5; and a dopant supply pipe 31 installed on the upper surface side of the induction heating coil 20 and for supplying a dopant gas to the molten zone 5. The induction heating coil 20 includes an opening penetrating from the upper surface to the lower surface, and the tip of the dopant supply pipe 31 is inserted into the opening.SELECTED DRAWING: Figure 1

Description

The present invention relates to a single crystal manufacturing apparatus and a method for producing a single crystal by the FZ method (Floating Zone method), and more particularly to an apparatus and method for adding a dopant to a silicon single crystal.

The FZ method is known as a method for producing a silicon single crystal. In the FZ method, a part of a raw material rod made of polycrystalline silicon is heated by an induction heating coil to generate a melting zone, and the raw material rod and the seed crystal located above and below the melting zone are gradually lowered. , A method of growing a large single crystal above a seed crystal. Unlike the CZ method (Czochralski) method, the FZ method does not use a quartz crucible, so that a single crystal having a very low oxygen concentration can be produced.

As a method of adding a dopant to a silicon single crystal, a method of spraying a gas containing a dopant on a melting zone to add the dopant is known. _{For example, Patent Document 1 describes that Ar-based PH 3} gas is blown from a nozzle for blowing a dopant gas provided above the induction heating coil toward the neck of the melting zone.

Further, Patent Documents 2 and 3 describe that in the method for producing a single crystal by the FZ method, a dopant gas is blown from a doping nozzle arranged below the induction heating coil toward the melting zone on the single crystal side. There is.

Japanese Unexamined Patent Publication No. 2011-88758 JP-A-2015-229612 Japanese Unexamined Patent Publication No. 2011-225451

In the method for producing a silicon single crystal by the FZ method, uniformization of the in-plane distribution of the resistivity of the single crystal is one of the important issues. When the dopant gas is supplied toward the neck portion of the fusion zone as in Patent Document 1, the dopant concentration in the outer peripheral portion of the silicon single crystal becomes low, and the resistivity in the outer peripheral portion of the single crystal becomes low. It was found that there is a problem that it tends to be high.

On the other hand, when the dopant gas is supplied to the melting zone from the dopant supply pipe arranged below the induction heating coil and outside the single crystal as in Patent Document 2, it always goes to the melting zone located at the outermost periphery of the single crystal. Only the dopant supply by the flow can be realized, and the dopant distribution in the single crystal plane cannot be adjusted arbitrarily. Moreover, in the supply form as in Patent Document 2, there is a problem that the amount of dopant discharged as it is without being incorporated into the melting zone increases, which leads to an increase in manufacturing cost.

Further, Patent Document 3 shows an example in which a dopant supply tube is installed in the space between the induction heating coil and the single crystal, but the gap between the induction heating coil and the single crystal is narrow, and the doping nozzle is stabilized in this gap. It is difficult to install the dopant supply pipe, and the dopant supply pipe may come into contact with the melting zone. If the dopant supply tube comes into contact with the melting zone, the single crystal growth itself cannot be performed.

Therefore, an object of the present invention is to provide a single crystal manufacturing apparatus and a single crystal manufacturing method capable of making the in-plane distribution of the resistivity of a single crystal as uniform as possible while stably installing a dopant supply tube. There is.

In order to solve the above problems, the single crystal manufacturing apparatus according to the present invention is an apparatus used for producing a single crystal by the FZ method, and includes an upper shaft that rotatably and vertically supports the raw material rod, and the upper shaft. A lower shaft that is coaxially arranged and rotatably and vertically supports a seed crystal arranged below the raw material rod, an induction heating coil that heats the raw material rod to generate a melting zone, and an induction heating coil. The induction heating coil is provided on the upper surface side and includes a dopant supply pipe that supplies the dopant gas to the melting zone, the induction heating coil has an opening that penetrates from the upper surface to the lower surface, and the tip portion of the dopant supply pipe is the said. It is characterized by being inserted into the opening.

Further, in the method for producing a single crystal according to the present invention, the raw material rod is heated by an induction heating coil to form a melting zone, and the raw material rod and the single crystal located above and below the melting zone are lowered to form the melting zone. A method for producing a single crystal by the FZ method for growing a single crystal, which comprises blowing a dopant gas from the upper surface side of the induction heating coil toward the melting zone located on the lower surface side of the induction heating coil. ..

According to the present invention, the dopant can be supplied to the single crystal side melting portion of the melting zone located below the induction heating coil. Since the dopant introduced from the melting portion on the single crystal side diffuses toward the central portion, it is possible to produce a single crystal having a uniform in-plane distribution of resistivity while increasing the dopant concentration on the outer peripheral portion of the single crystal. Further, since the dopant supply pipe is installed on the upper surface side of the induction heating coil, the dopant supply pipe can be stably installed, and the dopant gas can be supplied downward from above the melting portion on the single crystal side. ..

In the present invention, the tip of the dopant supply tube is preferably arranged directly above the region of 0.7R or more and 1R or less (where R is the maximum radius of the single crystal) from the center of the single crystal. It is preferable to supply the dopant gas toward the melting zone existing in the region of 0.7R or more and 1R or less from the center of the single crystal. Thereby, the resistivity distribution in the single crystal plane can be sufficiently made uniform.

In the method for producing a single crystal according to the present invention, it is preferable to blow a dopant gas onto the molten zone through a slit extending from the inner opening of the induction heating coil to the outermost periphery. In this way, by using the slit of the induction heating coil, it is possible to configure the tip of the dopant supply tube to penetrate the induction heating coil without preparing a dedicated opening.

According to the present invention, there is provided a single crystal manufacturing apparatus and a single crystal manufacturing method by the FZ method capable of making the in-plane distribution of the resistivity of a single crystal as uniform as possible while stably installing a dopant supply tube. can do.

FIG. 1 is a schematic view showing a configuration of a single crystal manufacturing apparatus according to an embodiment of the present invention. Figure 2 is a diagram showing in detail an example of the configuration of the induction heating coil and a dopant feed pipe, (a) is a plan view, (b) is a sectional view taken along the X ₁ -X ₁ line in (a) is a side view seen from an arrow _{X 0} direction (c) is (a). Figure 3 is a diagram showing in detail another example of the configuration of the induction heating coil and a dopant feed pipe, (a) is a plan view, the (b) along the X ₁ -X ₁ line in (a) It is a sectional view. FIG. 4 is a diagram showing the maximum deviation of the in-plane distribution of the resistivity of the wafer sample according to the examples of the present invention and the comparative example. FIG. 5 is a graph showing the resistivity distribution in the surface of the silicon wafer ((resistivity measurement value-resistivity target value) / resistivity target value), (a) is a comparative example, and (b) is an example of the present invention. Are shown respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view showing a configuration of a single crystal manufacturing apparatus according to an embodiment of the present invention.

As shown in FIG. 1, this single crystal manufacturing apparatus 1 is an apparatus for growing a silicon single crystal by the FZ method, and has an upper shaft 11 that rotatably and vertically supports the raw material rod 2 and an upper shaft. A raw material feeding mechanism 12 that rotates the raw material rod 2 together with 11 and feeds it downward, and a lower shaft 13 that is coaxially arranged with the upper shaft 11 and supports the seed crystal 3 arranged below the raw material rod 2 so as to be rotatable and elevating. The crystal feeding mechanism 14 that rotates the seed crystal 3 together with the lower shaft 13 and sends it downward, and the tapered portion 4a of the silicon single crystal 4 that has grown in size due to the progress of crystal growth, abuts on the tapered portion 4a to support the weight of the silicon single crystal 4. Supplying a dopant that supplies a dopant to the single crystal weight holder 17, the induction heating coil 20 that heats the lower end of the raw material rod 2, and the fusion zone 5 (silicon melt) between the raw material rod 2 and the silicon single crystal 4. It has a device 30 and.

The raw material rod 2 is made of high-purity polycrystalline silicon obtained by purifying a silicon raw material such as monosilane, and the upper end portion of the raw material rod 2 is attached to the lower end portion of the upper shaft 11 via the raw material holder 15. The lower end of the seed crystal 3 is attached to the upper end of the lower shaft 13 via the seed crystal holder 16. Usually, the maximum diameter of the raw material rod 2 is smaller than the maximum diameter of the silicon single crystal 4.

The induction heating coil 20 is a high-frequency coil that surrounds the raw material rod 2 or the melting zone 5. By applying a high frequency voltage to the induction heating coil 20, a part of the raw material rod 2 is induced to be heated to form a melting zone 5. After the seed crystal 3 is fused to the molten zone 5 thus generated, the silicon single crystal 4 can be grown from the molten zone 5 by lowering the raw material rod 2 and the silicon single crystal 4 while rotating them.

The dopant supply device 30 has a dopant supply pipe 31 that blows a dopant gas onto the melting zone 5. As shown in the figure, the melting zone 5 is located below the induction heating coil 20, the raw material side melting portion 5a located above the induction heating coil 20, the neck portion 5b located inside the inner opening of the induction heating coil 20, and the induction heating coil 20. The single crystal side melting portion 5c is provided, and the dopant supply pipe 31 blows the dopant gas onto the single crystal side melting portion 5c. The amount of dopant supplied to the melting zone 5 is adjusted by changing the concentration of the dopant gas. In order to stably control the supply amount of the dopant, it is preferable to keep the flow rate of the dopant gas constant and adjust only the concentration of the dopant gas.

The dopant supply pipe 31 is an elongated pipe made of quartz glass. The dopant supply pipe 31 according to the present embodiment is a substantially L-shaped pipe, and has a downward tip portion that is bent at a substantially right angle after extending in a substantially horizontal direction along the upper surface of the induction heating coil 20. There is. The tip of the dopant supply pipe 31 penetrates the induction heating coil 20 and projects below the lower surface thereof, and is configured so that the dopant gas can be sprayed on the outer peripheral portion of the single crystal side melting portion 5c. (See FIG. 1). The tip of the dopant supply tube 31 is provided apart from the single crystal side melting portion 5c, and is preferably within a region of 0.7R or more and 1R or less from the center of the silicon single crystal 4 in a plan view (however, R is simple). The maximum radius of the crystal), more preferably 0.8R or more and 0.95R or less.

Figure 2 is a diagram showing in detail an example of the configuration of the induction heating coil 20 and the dopant feed pipe 31, (a) is a plan view, the (b) along the X ₁ -X ₁ line in (a) sectional view, a side view seen from an arrow _{X 0} direction (c) is (a).

As shown in FIGS. 2A to 2C, the induction heating coil 20 includes a coil conductor 21 made of a substantially annular conductor plate and a pair of terminal electrodes 22 for applying a high frequency voltage to the coil conductor 21. It has 22 and. The coil conductor 21 is mainly made of copper or silver, and the pair of terminal electrodes 22 and 22 are connected to an AC power supply (not shown).

In the coil conductor 21, an inner opening 23 is formed in the center of the disk-shaped conductor, and a part of the annular conductor is divided in the circumferential direction by a slit 24 extending in the radial direction from the inner opening 23. .. The slit 24 is arranged between the pair of terminal electrodes 22 and 22 that are close to each other in the circumferential direction, and divides the connection position of the pair of terminal electrodes 22 and 22 in the circumferential direction. The outer diameter of the coil conductor 21 is larger than the diameter of the raw material rod 2 and the silicon single crystal 4 (diameter of the straight body portion 4b), and the inner diameter of the coil conductor 21 (diameter of the inner opening 23) is larger than the diameter of the raw material rod 2 and the silicon single crystal. It is smaller than the diameter of 4.

The dopant supply pipe 31 has a straight portion 31a extending in a substantially horizontal direction along the upper surface of the induction heating coil 20, and a downward tip portion 31b in which the tip portion of the straight portion 31a is bent at a substantially right angle. .. It is preferable that the straight portion 31a of the dopant supply pipe 31 extends in a direction different from the extending direction (X direction) of the slit 24 in a plan view. By doing so, the dopant supply pipe 31 can be stably installed on the upper surface of the induction heating coil 20.

Further, by providing the dopant supply pipe 31 by using the slit 24 provided in the induction heating coil 20 as an opening, the downward dopant supply pipe 31 can be installed without providing a dedicated opening. The tip portion 31b of the dopant supply pipe 31 reaches the lower surface side from the upper surface side of the induction heating coil 20 through the slit 24, and projects downward from the lower surface side. By spraying the dopant gas from above to below the outer peripheral portion (shoulder portion) of the single crystal side melting portion 5c, the dopant gas is easily taken into the single crystal side melting portion 5c, so that the dopant gas is easily taken into the single crystal side melting portion 5c. The amount of dopant incorporated can be increased.

It is preferable that the slit 24 of the induction heating coil 20 is filled with an insulating member 25 for preventing electric discharge. In this case, the slit 24 can be used as an opening by not providing the insulating member 25 at the insertion position of the dopant supply pipe 31 and leaving a part of the slit 24 extending in the radial direction as an opening. Further, the insulating member 25 can be used as a positioning member and a fixing member of the dopant supply pipe 31. For convenience of explanation, the insulating member 25 is not shown in FIG. 2 (c).

Since the distance between the induction heating coil 20 and the single crystal side melting portion 5c is narrow, it is very difficult to arrange the dopant supply pipe 31 on the lower surface side of the induction heating coil 20 as in the conventional case. It is difficult to install the dopant supply pipe 31 on the upper surface side of the induction heating coil 20, but since the size (diameter) of the raw material rod 2 is smaller than that of the silicon single crystal 4, the dopant is located near the outer periphery of the induction heating coil 20. The supply pipe 31 can be installed, whereby the dopant can be locally supplied to the single crystal side molten portion 5c.

Figure 3 is a diagram showing in detail another example of the configuration of the induction heating coil 20 and the dopant feed pipe 31, (a) is a plan view, (b) the _X 1 -X ₁ line in (a) It is a cross-sectional view along.

As shown in FIGS. 3A and 3B, even if the induction heating coil 20 is provided with a dedicated opening 26 for penetrating the tip portion 31b of the dopant supply pipe 31 separately from the slit 24. Good. Even with such a configuration, the dopant gas can be sprayed on the single crystal side melting portion 5c while arranging the dopant supply pipe 31 above the induction heating coil 20.

As described above, the single crystal manufacturing apparatus 1 according to the present embodiment heats the raw material rod 2 by the induction heating coil 20 to generate a melting zone 5, and is arranged downward so as to penetrate the induction heating coil 20. Since the dopant gas is sprayed onto the single crystal side melting portion 5c of the melting zone 5 by using the dopant supply pipe 31, the dopant can be uniformly distributed to every corner of the single crystal side melting portion 5c, and the silicon single crystal 4 can be uniformly distributed. It is possible to realize a uniform in-plane resistance distribution by suppressing an increase in the resistance of the outer peripheral portion. Further, since the dopant supply pipe 31 is installed on the upper surface side of the induction heating coil 20 and the tip portion 31b of the dopant supply pipe 31 is provided so as to penetrate the induction heating coil 20, the dopant supply pipe 31 is stably installed. The dopant gas can be supplied downward from above the single crystal side melting portion 5c.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. Needless to say, it is included in the range.

For example, in the above embodiment, the method for producing a silicon single crystal has been given as an example, but the present invention is not limited to the silicon single crystal, and various single crystals can be targeted.

As an example of the present invention, a dopant gas was sprayed on the outer peripheral portion of the single crystal side melting portion of the melting zone using a dopant supply pipe penetrating the induction heating coil shown in FIG. 1 to grow a silicon single crystal having a diameter of 200 mm. .. Specifically, the dopant gas obtained by diluting the phosphine gas with argon gas was sprayed so that the outer diameter of the tip of the dopant supply tube was located 0.8R from the center of the single crystal.

As a comparative example, a dopant gas obtained by diluting phosphine gas with argon gas was sprayed from a dopant supply pipe provided on the upper side of the induction heating coil toward the neck portion of the melting zone to grow a silicon single crystal having a diameter of 200 mm. The single crystal growth conditions of the examples of the present invention and the comparative examples were the same except that the spraying mode of the dopant gas was changed.

Next, 25 silicon wafer samples were prepared by processing the silicon single crystals grown in the examples of the present invention and the comparative examples. The resistivity of the wafer sample is scanned in the radial direction, and one outer peripheral position (6 mm inward from the outermost circumference) of the wafer, one intermediate position (-R / 2), the wafer center position (C), and the other intermediate position. The resistivity at a total of 5 points was measured at the position (+ R / 2) and the other outer peripheral position of the wafer (position 6 mm inward from the outermost circumference). Then, the maximum deviation of the in-plane distribution of the resistivity of 25 wafer samples was compared. As a result, as shown in FIG. 4, it was found that the examples of the present invention tended to improve as compared with the comparative examples.

FIG. 5 is a graph showing the resistivity distribution in the surface of the silicon wafer ((resistivity measurement value-resistivity target value) / resistivity target value), (a) is a comparative example, and (b) is an example of the present invention. Are shown respectively.

The resistivity distribution of the silicon wafer according to the comparative example shown in FIG. 5 (a) shows a large increase in the resistivity at the outer peripheral portion of the wafer, whereas the resistivity distribution of the silicon wafer according to the example of the present invention shown in FIG. 5 (b) is It was confirmed that the increase in resistivity at the outer periphery of the wafer was small and the in-plane variation in resistivity was small.

1 Single crystal manufacturing equipment 2 Raw material rod 3 Seed crystal 4 Silicon single crystal 4a Tapered part 4b Straight body part 5 Melting zone 5a Raw material side melting part 5b Neck part 5c Single crystal side melting part 11 Upper shaft 12 Feeding mechanism 13 Lower shaft 14 Crystal feed mechanism 15 Raw material holder 16 Seed crystal holder 17 Single crystal weight holder 20 Inductive heating coil 21 Coil conductor 22 Terminal electrode 23 Inner opening 24 Slit 25 Insulation member 26 Opening 30 Dopant supply device 31 Dopant supply pipe 31a Straight Part 31b Nozzle part

Claims (6)

A single crystal manufacturing apparatus used for manufacturing a single crystal by the FZ method.
An upper shaft that supports the raw material rod so that it can rotate and move up and down,
A lower shaft coaxially arranged with the upper shaft and rotatably and vertically supporting a seed crystal arranged below the raw material rod,
An induction heating coil that heats the raw material rod to generate a melting zone,
A dopant supply pipe which is installed on the upper surface side of the induction heating coil and supplies a dopant gas to the melting zone is provided.
The induction heating coil has an opening that penetrates from the upper surface to the lower surface.
A single crystal manufacturing apparatus characterized in that the tip end portion of the dopant supply tube is inserted into the opening portion. The single according to claim 1, wherein the tip of the dopant supply tube is arranged directly above the region of 0.7R or more and 1R or less (where R is the maximum radius of the single crystal) from the center of the single crystal. Crystal manufacturing equipment. The single crystal manufacturing apparatus according to claim 1 or 2, wherein the opening is a slit extending from the inner opening of the induction heating coil to the outermost circumference. Production of a single crystal by the FZ method in which a raw material rod is heated by an induction heating coil to form a melting zone, and the raw material rod and the single crystal located above and below the melting zone are lowered to grow the single crystal. It ’s a method,
A method for producing a single crystal, which comprises blowing a dopant gas from the upper surface side of the induction heating coil toward the melting zone located on the lower surface side of the induction heating coil. The single crystal according to claim 4, wherein the dopant gas is supplied toward the melting zone existing in a region of 0.7R or more and 1R or less from the center of the single crystal (where R is the maximum radius of the single crystal). Manufacturing method. The method for producing a single crystal according to claim 4 or 5, wherein the dopant gas is blown onto the molten zone through a slit extending from the inner opening of the induction heating coil to the outermost periphery.

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