JPH0688864B2 - Rectifier for single crystal pulling equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used in a single crystal pulling apparatus by the CZ method, concentrically surrounding a single crystal pulled vertically upward, and an inert gas is flowed down inside. The present invention relates to a rectifying cylinder for a single crystal pulling apparatus.

[Prior Art] When pulling a Si single crystal from the Si melt in the quartz crucible by the CZ method, the reaction between the quartz crucible and the Si melt causes volatile SiO
Are generated and are deposited on the crucible edge, the Si single crystal, the pulling shaft and the chamber inner wall. The SiO deposited on the pull-up shaft that rises while rotating is scraped off by the airtight seal ring of the upper lid, drops into the melt below, and causes defects in the growing single crystal. Therefore, coaxially with the pulling shaft, a rectifying cylinder is hung in the chamber to 150 to 350 mm above the melt surface, Ar gas is allowed to flow into the rectifying cylinder from above, and SiO evaporated from the melt surface is stored in the chamber together with Ar gas. A method of discharging from the lower part has been proposed (Japanese Patent Publication No. 54-6511).

On the other hand, by attaching a collar with the lower end of this rectifying tube folded outward and upward, the vertical temperature gradient of the single crystal near the solid-liquid interface is increased to increase the crystal growth rate and Oxygen-induced defects (OISF) and swirl defects are reduced by lowering the oxygen concentration of
A method for enhancing the O 2 emission effect has been proposed. (Japanese Patent Laid-Open No. 64-
65086 publication).

Such a rectifying tube is preferably formed of graphite from the viewpoint of heat resistance, processability and cost, but it is possible to observe the shape of the Si single crystal immediately after pulling or to optically determine the diameter of the solid-liquid interface. Unable to measure, automatic diameter control and good
It hinders the growth of Si single crystals. Therefore, it is proposed in the above publication to form a window hole at the lower end of the flow straightening cylinder.

[Problems to be Solved by the Invention] However, when the window hole is formed, the flow rate of Ar gas flowing out from the lower end opening of the flow straightening cylinder is reduced, and the above effect is reduced. For example, the amount of oxygen evaporated from the surface of the melt decreases and the oxygen concentration of the Si single crystal increases. Specifically, it becomes difficult to reduce the oxygen concentration to 18 ppma or less, and it is not possible to meet the recent demands of device manufacturers who are promoting high integration. Such problems are solved by increasing the flow rate of Ar gas. However, when actually performed, it was found that this amount becomes a large amount, for example, 200 l / min, and the cost becomes high, as shown in an experimental example described later. Although it is possible to decrease the pressure in the chamber (furnace) to increase the amount of oxygen evaporated, the reaction between the quartz crucible and the Si melt becomes large and the life of the quartz crucible becomes short, resulting in high cost.

In view of such problems, an object of the present invention is to observe the shape of a single crystal without increasing the flow rate of an inert gas and without reducing the above-mentioned effects, and further, it is easy to manufacture. An object of the present invention is to provide a rectifying cylinder for a single crystal pulling device that does not significantly increase the cost.

[Means for Solving the Problem] In order to achieve this object, in a rectifying cylinder for a single crystal pulling apparatus according to the present invention, an upper end opening is connected to an upper end opening of a main chamber in which a crucible is provided. It is provided with a first graphite cylinder concentrically surrounding a single crystal pulled vertically upward and having a window formed on a lower side surface thereof, and a quartz window plate covering the window.

A specific window plate mounting structure is, for example, a second window in which an inner diameter is substantially equal to an outer diameter of the cylinder and a window hole corresponding to the window hole is formed.
The graphite cylinder is fitted into and locked in the first cylinder with the both window holes aligned, and a groove is formed in the window hole edge portion of the joint surface of the first cylinder and the second cylinder. The structure is such that the edge portion of the window plate is fitted in the groove.

In another specific window plate mounting structure, the window plate is configured by a cylinder having an outer diameter substantially equal to the inner diameter of the first cylinder, and is fitted and locked in the first cylinder. There is.

It should be noted that a graphite collar protruding outward and upward may be attached to the lower end of the flow straightening cylinder.

Also, although it is not necessary, the surface of the rectifying cylinder and this collar should be
It may be coated with SiC to make the deterioration smaller.

[Function] Since the rectifying cylinder has a window hole, the shape of the Si single crystal immediately after being pulled can be observed, the diameter can be optically measured, and a good Si single crystal can be grown. Is possible.

Since this window hole is covered with the window plate, all the inert gas flowing down in the straightening cylinder passes between the lower end of the straightening cylinder and the melt surface, and the flow rate of the inert gas does not need to be particularly large. It is possible to reduce the oxygen concentration in the single crystal, prevent SiO precipitation on the pulling shaft, etc., and increase the single crystal growth rate.

In addition, as the material of the flow straightening cylinder, one that is heat resistant and does not emit impurities is required, and ceramics and the like can be considered, but the cylinder of the main body is made of graphite that is easy to mold and is inexpensive, and only the window hole portion, that is, the necessary Since only part of the rectifying cylinder is covered with quartz, the rectifying cylinder as a whole is easy to manufacture and does not significantly increase the cost.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

(1) First Example FIG. 1 shows a use state of a rectifying cylinder for a single crystal pulling apparatus.

A sub chamber 14 is connected to the upper end opening 12 of the main chamber 10. An inlet joint 14a for supplying Ar gas is formed on the side wall of the sub chamber 14, and the main chamber 10
A discharge hole 10a for suctioning and discharging Ar gas is formed on the bottom surface of
A viewing window on the shoulder of the main chamber 10 for observing the pulled single crystal
Another viewing window (not shown) is provided opposite to 10b and the ITV for measuring the diameter of the solid-liquid interface. In this main chamber 10, a table 18 is fixed to the upper end of an elevating and lowering rotary shaft 16 which can be raised and lowered and rotated, and a graphite crucible 20 is mounted on the table 18.
Is placed, and a quartz crucible 22 is fitted in the graphite crucible 20. The circumference of the graphite crucible 20 is surrounded by a heater 24.
The periphery of is surrounded by a graphite heat insulating wall 26. When polycrystalline Si is put in the quartz crucible 22 and power is supplied to the heater 24,
Si is melted to form a melt 28.

On the other hand, a seed crystal 34 is held via a seed holder 32 at the lower end of the pulling shaft 30 which is vertically moved along the center line of the sub-chamber 14.

Further, the upper end opening of the main chamber 10 is connected to the upper end opening of a graphite elongated cylinder 40 which is the main body of the flow straightening cylinder 38. The elongated cylinder 40 is arranged concentrically with the pulling shaft 30 and vertically. The length of the long cylinder 40 is measured from the lower end of the long cylinder 40 to the melt 28
Make sure that the distance to the surface is 5 to 100 mm. The inner diameter of the long cylinder is such that the shortest distance between the inner surface of the flow straightening cylinder 38 and the surface of the single crystal 36 is 5 to 100 mm.

An observation window 40a is formed on the lower side surface of the oblong cylinder 40. At the lower end of the oblong cylinder 40, a locking portion 40b that is reduced in diameter and faces inward in the radial direction is formed.

As shown in FIG. 2, on the side surface of the graphite short cylinder 42 whose outer diameter is approximately equal to the inner diameter of the long cylinder 40, a window hole 42a having the same shape as the window hole 40a is formed.
Are formed. A groove frame 42b is formed at the edge of the window hole 42a on the outer peripheral surface of the short cylinder 42, and the edge of the quartz window plate 44 is fitted into the groove frame 42b. In this state, the short cylinder 42 is fitted into the long cylinder 40, and the short cylinder 42 is locked by the locking portion 40b of the long cylinder 40 with the window hole 42a and the window hole 40a aligned. FIG. 3 shows a cross section through the window in this locked state.

As shown in FIG. 1, a small-diameter side end of a hollow truncated cone-shaped graphite collar 46 having the same inclination as the outer peripheral surface is joined to the outer peripheral surface of the locking portion 40b.

Next, the operation of this embodiment configured as described above will be described.

The pressure inside the main chamber 10 is reduced by a vacuum pump, Ar gas is supplied from the inlet joint 14a of the sub chamber 14, and Ar gas is sucked and discharged from the discharge hole 10a of the main chamber 10. A
Adjust the amount of gas supply or exhaust to adjust the main chamber 1
Set the pressure in 0 to about 100 mbar. Next, electric power is supplied to the heater 24 to heat and melt the polycrystalline silicon in the quartz crucible 22 to form a melt 28. Then, the pulling shaft 30 is lowered to immerse the seed crystal 34 in the melt 28, and the seed crystal 34 is pulled up to grow a single crystal 36. At this time, the operator observes the single crystal 36 through the viewing window 10b of the main chamber 10 through the window plate 44 and adjusts various control amounts (corrects the automatic control amount) so that a good single crystal 36 is grown. .

On the other hand, Ar gas flows down in the rectifying cylinder 38, and all of the Ar gas is rectifying cylinder.
It is discharged from the quartz crucible 22 through the space between the lower end of 38 and the surface of the melt 28, between the outer surface of the collar 46 and the inner surface of the quartz crucible 22, and descends to be sucked and discharged through the discharge hole 10a.

Therefore, the volatile SiO produced by the reaction between the melt 28 and the quartz crucible 22 is discharged through the discharge holes 10a along with the flow of Ar gas.
Is discharged from the inner surface of the quartz crucible 22, the outer surface of the collar 46,
It is possible to prevent SiO from depositing on the single crystal 36, the seed holder 32, the pulling shaft 30, and the like. Further, since the amount of oxygen evaporated from the melt 28 is increased by the flow of Ar gas and the oxygen concentration of the single crystal 36 is lowered, oxidation-induced defects and swirl defects are reduced.

Also, since Ar gas passes so as to cover the periphery of the single crystal 36,
The single crystal 36 is cooled. Further, the collar 46 is heated by absorbing the radiant heat directly received from the melt 28 and the radiant heat reflected on the inner surface of the quartz crucible 22, but is cooled by Ar gas, so that the temperature at the lower part of the long cylinder 40 is the color. It is considerably lower than the case without 46. Therefore, the temperature gradient in the vertical direction of the single crystal 36 near the solid-liquid interface becomes large, and the growth rate of the single crystal 36 becomes large. This means that the amount of oxygen taken up per unit length of the single crystal 36 is reduced, which contributes to the reduction of the oxygen concentration of the single crystal 36.

(2) Second Embodiment FIG. 4 shows a transverse cross section of the lower end portion of the flow straightening cylinder of the second embodiment.

In this straightening cylinder, a rectangular window hole 40c narrower than that of the first embodiment is used.
Are formed on the lower side surface of the graphite long cylindrical window 40A at three locations, and correspondingly, the graphite short cylinders 42A are also provided with three rectangular window holes 42c, and the window holes 42c on the outer peripheral surface of each short cylinder 42A are formed. Groove frame 42d on the edge
And a flat rectangular quartz window plate 44A is fitted into each groove frame 42d.

In this second embodiment, since the flat window plate is used, the first
The production is easier than in the embodiment, and the rectifying cylinder can be constructed at a lower cost.

(3) Third Embodiment FIG. 5 shows a lower structure of the third embodiment of the present invention.

The long cylinder 40 has the same shape as that of the first embodiment, but instead of the short cylinder 42 and the window plate 44, a quartz cylindrical window plate 44a having an outer diameter substantially equal to the inner diameter of the long cylinder 40 is used. It is fitted and locked inside.

The third embodiment has an advantage that the window plate 44a having the same shape can be used for any shape of the window hole.

(4) Experimental Example Next, an experimental example will be described.

(A) The conditions that serve as a reference for comparison are as follows.

Ar gas flow rate: 100 l / min Main chamber 10 pressure: 100 mbar Inner diameter of rectifying cylinder 38: 200 mm Initial distance from lower end of rectifying cylinder 38 to surface of melt surface 28: 3
0 mm Area of the window hole 40a: 200 cm ² (necessary and sufficient area) No window plate 44 Diameter of the single crystal 36: 6 inch Under the above conditions, the oxygen concentration after the straight body part 10 cm of the single crystal 36 was 20 ppma. The dispersion D D of the oxygen concentration distribution in the cross section of the straight body portion was D D = 100 (C _C -C _P ) / C _C was 15%. Where C _C is the oxygen concentration at the center C _P is the oxygen concentration at a position 3 mm from the peripheral surface toward the center. Since the oxygen concentration is required to have this maximum value equal to or lower than the reference value, it is necessary to reduce the dispersion D.

(B) Of the above standard conditions, only Ar gas flow rate is 200 l / min
When changed to, the oxygen concentration could be reduced by about 1.5 ppma. However, the dispersion D was deteriorated to 20%.

(C) Under the standard conditions of (A) above, when the window plate is attached to the window hole and the other conditions are the same, the oxygen concentration is about 3 ppma.
Could be lowered. The dispersion D is 13%,
Slightly improved.

[Effects of the Invention] As described above, in the rectifying cylinder for a single crystal pulling apparatus according to the present invention, the lower end portion is provided with the window hole and the window hole is covered with the window plate, so that the rectifying tube flows down. All of the inert gas passes between the lower end of the rectifying cylinder and the melt surface, and SiO can be prevented from precipitating on the pulling shaft, etc. without increasing the flow rate of the inert gas, and single crystal growth can be prevented. It is possible to increase the speed and further reduce the oxidation-induced defects and swirl defects.The cylinder of the main body is made of graphite which is easy to mold and is inexpensive, and only the window hole portion, that is, only the necessary portion is made of quartz. Since it is covered with, the rectifying cylinder as a whole has an excellent effect that it is easy to manufacture and the cost is not significantly increased.

[Brief description of drawings]

1 to 3 relate to a first embodiment of a rectifying cylinder for a single crystal pulling apparatus according to the present invention, FIG. 1 is a schematic vertical sectional view showing a condition of use of the rectifying cylinder, and FIG. 2 is a rectifying cylinder. FIG. 3 is an exploded perspective view showing the lower structure of FIG. 3, and FIG. 3 is a sectional view taken along line III-III in the assembled state of FIG. FIG. 4 is a cross-sectional view showing the lower structure of the flow straightening cylinder according to the second embodiment of the present invention. FIG. 5 is an exploded perspective view showing the lower structure of the flow straightening cylinder according to the third embodiment of the present invention. In the figure, 10 is a main chamber 12, an opening 14 is a subchamber 22, a quartz crucible 28 is a melt 30, a pulling shaft 36 is a single crystal 38, a rectifying cylinder 40 is a graphite elongated cylinder 40a, 40c, 42a, 42c is a window. Holes 42 and 42A are graphite short cylinders 42b and 42d are groove frames 44, 44A and 44B are quartz window plates 46 are graphite collars.

Claims (3)

[Claims] 1. A main chamber (10) having a crucible (22) internally provided with an upper end opening (12) connected to the upper end opening to concentrically surround a single crystal (36) pulled vertically upward.
A first graphite cylinder (40, 40A) having window holes (40a, 40c) formed on the lower side surface, and a quartz window plate (44, 44A, 44B) covering the window hole. A rectifying cylinder for a single crystal pulling device. 2. A second graphite cylinder (42, 42A) having an outer diameter substantially equal to the inner diameter of the cylinder and having window holes (42a, 42c) corresponding to the window holes (40a, 40c). , The both window holes are aligned with each other and fitted and locked in the first cylinder (40, 40A), and the groove (42b, 42b, at the edge of the window hole of the joint surface of the first cylinder and the second cylinder). 42d) is formed, and the window plate (44, 44A) is formed in the groove.
The rectifying cylinder for a single crystal pulling apparatus according to claim 1, wherein an edge portion of the single crystal pulling apparatus is fitted. 3. The window plate (44B) is a cylinder having an inner diameter substantially equal to the outer shape of the first cylinder (40), and the window plate (44B) is fitted and locked in the first cylinder so as to close the window hole (40a). The rectifying cylinder for a single crystal pulling apparatus according to claim 1, which is covered.