JPH10273384A - Apparatus for pulling single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for pulling a single crystal so as to afford an always stable holding state even when the objective cross-sectional shape of the dislocation-free crystal at the holding position is any one. SOLUTION: This apparatus for pulling a single crystal comprises tip members 3 of holding means 1, occupying regions thereof brought into contact with the surface of the crystal when holding the crystal and provided with each metal 4 having the lower melting point than about the ambient temperature when holding the crystal and each metallic layer 6 manifesting the flexibility at the temperature for covering the metal 4 in the apparatus for pulling the single crystal according to the Czochralski process in order to hold the dislocation-free crystal part after achieving the dislocation-free state by the Dash neck method with the holding means 1 and grow the single crystal while pulling up the single crystal with a driving means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulling apparatus used for pulling a single crystal of silicon or the like during growth, and more particularly to a pulling apparatus for a large diameter semiconductor single crystal pulling furnace.

[0002]

2. Description of the Related Art As one method of manufacturing a silicon crystal used as a semiconductor crystal, for example, there is a so-called CZ (Czochralski) method of manufacturing by pulling a single crystal. This is to heat and melt the bulk polycrystalline silicon in a crucible in an inert gas chamber furnace, and after contacting the seed single crystal with this molten silicon, while cooling,
The seed crystal is slowly raised while rotating, and once grown under the seed crystal, the crystal is squeezed narrowly (seeding) to cause dislocations to cross the crystal side surface to form a dislocation-free region (dash neck method). This is a method in which dislocation single crystals are pulled up and grown.

A single crystal pulling apparatus has been used for pulling a single crystal. This device mainly has a configuration in which a wire having a fixed attachment portion for a seed crystal at its lower end is wound while rotating in the axial direction thereof.

[0004]

In recent years, as the size of a semiconductor device increases with an increase in the amount of integrated circuits, the diameter of a single crystal tends to increase in order to increase the efficiency of manufacturing the semiconductor device. Therefore, the weight of the pulled single crystal is also increased.
However, in the pulling of the seed crystal portion by the wire of the pulling device as described above, there is a limit in the load resistance, and it is impossible to pull a heavy single crystal.

Therefore, a head is formed by expanding the diameter above the single crystal below the seed crystal and then reducing the diameter, and a plurality of catcher arms for engaging and holding the constricted portion under the head are formed at equal angular intervals. A device having a lifting shaft having a shape has been considered. In this method, a plurality of catcher arms are closed and clamped to each other to grip a constricted portion at the upper portion of the single crystal.

The grasping of the constricted portion by such a catcher arm is usually performed by the following operation.
That is, while maintaining the relative position of the catcher arm relative to the single crystal head constant, while maintaining the pulling of the single crystal wire at a predetermined rising speed, the catcher arm is
Close in a relative positional relationship such that the tip faces a lower position than the contact position on the constricted portion predetermined to be clamped in advance, and after the closed state, raise the catcher arm's rising speed faster than the rising speed of the single crystal. As a result, the constricted portion is caught at the predetermined contact position at the tip of the catcher arm, and an engaged / nipped state is obtained.

However, in the gripping of the constricted portion of the single crystal by such a catcher arm, the cross-sectional shape of the constricted portion varies widely for each single crystal, for example, crystal habit lines protruding at substantially equal intervals appear. Therefore, the initial contact state of each catcher arm tip with respect to the constricted portion is often non-uniform because of the point contact of each arm tip.

For example, when catching a constricted portion, some of the plurality of catcher arms are clamped in a state where they hit the protruding portion of the crystal habit line, and the ends of the other catcher arms float from the constricted portion. Due to the unstable pinching state, the constriction was loose between the catcher arms during the catching of the constriction and during the subsequent pulling operation, and it was on the ridge of the crystal habit line. The tip position of the catcher arm may shift from the raised portion to a lower flat portion.

[0009] Shock to the entire single crystal due to rattling and slipping due to the non-symmetrical cross-sectional shape of the constricted portion, such as the bulging of the habit line generated during the catching or pulling operation, is caused by the single crystal. This adversely affects the growth of GaN and hinders the production of good large-diameter single crystals.

In view of the above problems, the present invention provides a single crystal pulling apparatus which can always obtain a stable gripping state regardless of the cross-sectional shape of a target gripping position of a dislocation-free crystal. For the purpose of providing.

[0011]

In order to achieve the above object, a single crystal pulling apparatus according to the first aspect of the present invention comprises:
A single crystal pulling apparatus by the Czochralski method of holding a dislocation-free crystal portion after achieving dislocation-free by a dash neck method and continuing crystal growth, a holding means for holding a dislocation-free crystal, and the crystal Driving means for moving the gripping means in a state in which the crystal is gripped in the pulling direction, the gripping means having a tip member occupying an area in contact with the surface of the crystal when the crystal is gripped, The member is provided with a metal having a melting point lower than the vicinity temperature at the time of holding the crystal, and a metal layer covering the metal and exhibiting flexibility at the temperature.

In the single crystal pulling apparatus according to the second aspect of the present invention, in the single crystal pulling apparatus according to the first aspect, the tip member includes aluminum and a stainless steel layer covering the aluminum. Things.

According to the present invention, there is provided a single crystal in which a dislocation-free crystal after achieving dislocation-free by the dash neck method is gripped by gripping means, and a single crystal is grown while pulling up the gripping means in this crystal gripping state by driving means. It is a lifting device. Note that dislocation-free by the dash neck method here means dash (D
ash), which is based on a dislocation-free growth method. After a seed single crystal is brought into contact with molten silicon, the crystal is squeezed from the seed crystal once to narrow (seed squeezing) and grow so that dislocations cross the side of the crystal. This forms a dislocation-free region.

Further, the gripping means according to the present invention may further comprise: a metal having a melting point lower than a peripheral temperature at the time of gripping the crystal in a region contacting the crystal surface when gripping the crystal; And a metal layer exhibiting flexibility.

In such a configuration of the present invention, at the time when the crystal is to be gripped by the gripping means, the coating metal layer of the tip member is flexible and the metal in the coating metal layer is semi-solid. It is in a fixed state. Therefore, when the tip member of the holding means catches and holds the single crystal, the tip member comes into contact with the crystal to absorb a shock like a cushion, and the contact portion with the crystal is held by the holding pressure of the holding means. The contact surface is formed by deforming to a shape corresponding to the shape of the surface.

[0016] Therefore, the contact by the tip member is a surface contact by the contact surface changed into a shape corresponding to the shape of the opposing crystal surface regardless of the shape of the crystal surface. The holding state becomes much more stable than in the case of point contact.

Further, as the pulling of the single crystal in the gripping state by the surface contact progresses, the ambient temperature at the crystal contact portion of the tip member gradually decreases with the pulling, and the coating metal becomes inflexible accordingly. Since the metal in it solidifies and the contact surface shape of the tip member is fixed, even if the pulling weight increases, the grip strength also increases,
The single crystal can be pulled well in a stable holding state.

The coating metal may be any metal that exhibits flexibility at the ambient temperature when the crystal is gripped.
The metal to be coated only needs to have a melting point lower than the vicinity temperature at the time of holding the crystal, that is, a metal having a melting point close to but slightly lower than that in the coating metal.

For example, if the temperature around the holding portion when holding the crystal is around 800 ° C., the tip member has a structure in which aluminum having a melting point around 700 ° C. is coated with stainless steel. Things.

The thickness of the coated metal of the tip member according to the present invention is required to be flexible at the time of holding the crystal and to be exposed by the load action at that time to expose the metal therein. It is necessary to set it to a sufficient thickness so that there is no gap.

As the gripping means of the present invention, for example, a configuration basically including a plurality of catcher arms as in the related art can be used. What is necessary is just to provide the tip member of this invention in the lower end of each catcher arm. In this case, the device can be designed by attaching the tip member to the lower end of the existing catcher arm by using an appropriate attachment means, so that the device design is simple. Of course, the tip member of the present invention may be configured to be detachable and replaceable.

The holding position of the holding means of the present invention may be any position of the single crystal which grows after the dislocation-free state is achieved. Since it is determined according to the diameter of the crystal, a desired single crystal holding position and its diameter are set in advance. Of course, similarly to the conventional case, the head may be formed by expanding and reducing the diameter of the single crystal after achieving the dislocation-free state, and the constricted portion under the head may be sandwiched.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of an embodiment of the present invention, a single crystal pulling apparatus having a structure in which a tip member coated with stainless steel and having a plurality of catcher arms as gripping means will be described below. Is shown in FIG. In the present embodiment, a case will be described as an example where a single crystal head is formed after dislocation-free under a seed crystal is achieved and a constricted portion under the head is gripped.

First, one manufacturing process of the tip member used in the present embodiment will be described below. As shown in FIG.
5-5mm, inner diameter 10mm, length 50mm-100mm
The inside of the stainless steel pipe 5 having a degree of single sealing is prepared (a).
The thickness of the stainless steel pipe 5 is such that when a heavy pressure equivalent to 1 to 2 times the crystal weight at the time of catching the constricted portion described below is applied to the side of the pipe 5, the bending of the side reaches the opposite side. Set the thickness so that the pipe strength is obtained.

A rod-shaped aluminum 4 having a length substantially equal to the inner diameter of the stainless steel pipe 5 and having a length of 30 mm to 50 mm is inserted into one side of the stainless steel pipe 5 (b). Furthermore, after inserting a stainless steel rod 6 filling this space into the space behind the aluminum 4 in the stainless steel pipe 5, the open end in the stainless steel pipe is welded (welded portion 7) (c) to form the tip member 3. . The reason why the stainless steel rod 6 is inserted behind the aluminum 4 is to prevent the influence of heating when welding the open end on the aluminum 4.

The tip member 3 is formed in a shape corresponding to the method of engagement with the lower end of the catcher arm to be attached. The stainless steel rod 6 can be used particularly as an engagement portion. Therefore, the handling is simpler than the case where the aluminum 4 is simply sealed in the stainless steel pipe 5.

In this embodiment, FIGS. 1A and 1B
As shown in FIG. 5, the tip member 3 is formed into a substantially U-shape, and a mounting hole 10 is provided on a side surface below the arm of the catcher arm 1 to be described later. The distal end member 3 was attached to the catcher arm 1 by bringing the aluminum 4 insertion region into contact with the side and making the welded portion 7 side (stainless steel rod 6 region) penetrate the attachment hole 10.

As shown in FIG. 1, after the seed crystal 14 is brought into contact with the molten silicon in the crucible 20, the pulling device pulls up the wire 11 with a hoisting device (not shown) and sets a predetermined rotation speed. This is for a semiconductor single crystal pulling furnace by the Czochralski method in which a single crystal is grown under the seed crystal 14 by slowly raising the seed crystal 14 while rotating the wire 11 around the axis. This apparatus forms a constricted portion 16 of a head portion 15 composed of an enlarged diameter portion and a reduced diameter portion on a single crystal grown below a seed crystal 14, and then connects the constricted portion 16 to the lower end of three or more catcher arms. The portion is held in the radial direction to advance the crystal pulling.

In the lifting apparatus, as described above, three or more catcher arms 1 each having the tip member 3 attached to the lower end 2 are suspended at the upper end thereof so as to be arranged at equal angular intervals. (Grip means) 13 is pivotally supported to be openable and closable. The opening and closing of each catcher arm 1 is performed by the rotation control of each of the upper ends of the hanging portions 13 around the pivots.

The suspending portion 13 includes the wire 11 coaxially and moves in the axial direction by a driving device (driving means) (not shown) without mechanically interfering with the pulling of the seed crystal 14 of the wire 11. Is what is done. Along with the axial movement of the suspension unit 13 by the driving device, the catcher arms 1 are simultaneously moved in the crystal pulling direction.

The single crystal pulling operation in the large diameter semiconductor single crystal pulling furnace of the pulling apparatus having the above-described configuration will be described below. First, as an initial arrangement, each catcher arm 1
Is held in the open state by the driving device. In this initial arrangement, the hoisting device is controlled to bring the seed crystal 14 held by the carbon seed chuck 12 at the lower end of the wire 11 into contact with the molten silicon (melt rotation speed 0.1 to 15 rpm) in the crucible 20. Let it.

Thereafter, while the pulling wire 11 is rotated in the axial direction at a predetermined rotational speed of about 10 rpm, the hoisting device is simultaneously controlled to raise the seed crystal 14 to a predetermined ascending speed of about 3.0 m.
The wire 11 is pulled up so as to rise at m / min. By this rise, a dislocation-free single crystal having a diameter of about 5 mm grows at the lower end of the seed crystal 14.

Next, the diameter of the single crystal is increased by controlling the hoisting device to reduce the ascending speed to about 0.5 mm / min. After the diameter is increased to about 50 mm, the rate of rise is set to about 1.0 mm / min, and the diameter of the single crystal is reduced. The single crystal head 15 is formed by the above operation. After the diameter of the single crystal is reduced to about 30 mm, the hoisting device is further controlled to reduce the rising speed to about 0.5 mm / min to increase the diameter of the single crystal. As the diameter increases, a constricted portion 16 is formed below the head 15. In practice, such single crystal diameter control is performed by, for example, measuring the diameter of the single crystal over time using a light reflection method or the like, and controlling the driving of each driving device based on the data. It is performed by a computer or the like using a program for adjusting the ascending and rotating speeds, that is, a so-called automatic diameter control system.

After the constricted portion 16 is formed, the hanging portion 13 is driven by controlling the driving systems so that the single crystal pulling is continued while maintaining the predetermined rising speed by the diameter control system. Move the catcher arm 1 to the closed state. At this time, the relative position of each catcher arm 1 with respect to the single crystal is such that the position of the lower end 2 of the catcher arm (and the tip member 3) facing the single crystal in the closed state is the lower end of each catcher arm of the constricted portion 16. 2 is a position below a contact position determined to be sandwiched. Accordingly, the relative distance between the distal end members 3 of the lower ends 2 of the catcher arms corresponds to the diameter of the constricted portion 16 at the predetermined contact position, and has a slight gap with respect to the surface of the opposing constricted portion 16.

The surrounding temperature of the lower end portion 2 of the catcher arm at the time of the closed state is around 800.degree. Accordingly, in the distal end member 3, the aluminum 4 having a melting point of about 700 ° C. in the inside becomes a semi-molten state due to heat transfer from the periphery through the stainless steel pipe 5.

Next, the moving speed of the hanging portion 13 in the upper axis direction by the driving device is increased, and the moving speed of the catcher arm 1 in the closed state with respect to the liquid surface in the crucible 20 in the upper axis direction is increased. The rising speed of the part 15 with respect to the liquid level in the crucible 20 is increased. By this speed control, the tip member 3 of the lower end portion 2 of each catcher arm in the closed state moves the single crystal head 1
5 and moves in the upward direction, and comes into contact with a predetermined contact position of the constricted portion 16. That is, each tip member 3
When viewed from above, the single crystal head 15 relatively moves downward so as to drop, and catches the constricted portion 16 at the predetermined contact position.

At this time, since the stainless steel layer (the wall of the stainless steel pipe 5) of the tip member 3 has flexibility and the aluminum 4 inside is in a semi-molten state, the tip member 3 It bends under the action of a load and absorbs its impact. Immediately thereafter, the constricted portion 1 of the tip member 3
The contact portion with 6 is deformed into a shape according to the shape of the surface of the constricted portion 16 by the gripping pressure, and comes into surface contact, calms down, and a stable gripping state is obtained.

When a stable gripping state due to such surface contact is obtained, the driving device controls the movement of the suspension portion 13 in the upper axial direction so that the pulling at a predetermined rotation and ascending speed is continued. The crystal pulling operation is proceeded. As the pulling work progresses, the pulling weight of the single crystal increases,
At the same time, each catcher arm 1 also rises and the temperature around the lower end 2 decreases, so that the aluminum 4 of the tip member 3 solidifies and the shape of the contact surface corresponding to the surface of the constricted portion 16 of the tip member 3 is fixed. Thus, the gripping strength of the contact surface of the tip member 3 also increases.

As described above, according to the present lifting device, regardless of the shape of the constricted portion, the tip member 3 absorbs the impact of the catch when catching, and the contact portion has the constricted portion. Not only the contact surface shape according to the surface shape, but also the gripping by this surface contact becomes stronger as the gripping and pulling of the single crystal progresses, so even when pulling a large diameter semiconductor single crystal, a stable gripping state is always maintained Good pulling work can be performed.

In the above-described embodiment, the tip member is formed by forming a rod-like member using a stainless steel pipe into a substantially U-shape. However, the present invention is not limited to this. The shape may be appropriately designed according to the metal used and the mounting method.

Further, the holding means of the present invention is not limited to the structure comprising the catcher arm as shown in the above embodiment, but is a mechanism capable of mechanically grasping and pulling a single crystal. As long as the tip member can be provided in the contact region with the crystal, it can be widely used.

Further, in the above embodiment, the single crystal head is formed immediately after dislocation-free under the seed crystal, and the constricted portion under this head is used as the gripping position. However, the present invention is not limited to this. Alternatively, the pinching may be performed when the diameter of the single crystal further increases.

[0043]

As described above, according to the present invention, even in pulling a large-diameter single crystal, a stable gripping state can always be obtained in accordance with the shape of the target gripping position of the dislocation-free crystal. There is an effect that it can be performed.

[Brief description of the drawings]

1A and 1B are explanatory views showing a holding device according to an embodiment of the present invention, wherein FIG. 1A is a schematic configuration diagram of the device, and FIG. 1B is a partially enlarged view of the vicinity of a lower end of a catcher arm in FIG. .

FIGS. 2A to 2C are explanatory diagrams illustrating an example of a manufacturing process of a tip member used in the holding device of FIG. 1; FIGS.

[Explanation of symbols]

 1: Catcher arm 2: (Catcher arm) lower end 3: Tip member 4: Aluminum 5: Stainless steel pipe 6: Stainless steel rod 7: Welded part 10: Mounting hole 11: Wire 12: Seed chuck 14: Seed crystal 15: Single crystal Head 16: Constricted part

Claims (2)

[Claims] An apparatus for pulling a single crystal by the Czochralski method, in which a dislocation-free crystal portion after achieving a dislocation-free crystal by a dash neck method and crystal growth is continued to hold a dislocation-free crystal portion, is provided. Means, and a driving means for moving the gripping means in a state of gripping the crystal in the pulling direction, wherein the gripping means includes a tip member occupying an area in contact with a surface of the crystal when gripping the crystal. The tip member includes a metal having a melting point lower than the vicinity temperature at the time of gripping the crystal, and a metal layer covering the metal and exhibiting flexibility at the temperature. Single crystal pulling device. 2. The single crystal pulling apparatus according to claim 1, wherein the tip member includes aluminum and a stainless steel layer covering the aluminum.