JPH09255484A - Supporting member for crucible for pulling single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supporting member capable of cooling the bottom of a crucible to a fixed temperature. SOLUTION: This supporting member 4 is equipped with a main body 5 of a crucible pan provided with a recessed part at the center on the top of a disc and a revolving shaft 6 fitted to the center on the under surface of the crucible pan 5. A hollow disc cooling plate 7 having a thickness dimension smaller than that of the recessed part of the main body is engaged with the recessed part of the main body 5 of the crucible pan. The bowl-shaped bottom of a crucible 1 engaged with a hollow formed by the cooling plate 7 and the peripheral part of the main body 5 of the crucible pan enclosing the cooling plate. Two flow channels 10 for passing a cooling medium such as a silicone oil or water are installed in the direction of the shaft length of the revolving shaft 6. The tops of the flow channels 10 are opened through the main body 5 of the crucible pan and connected to the cooling plate 7. The cooling medium at a fixed temperature is sent from one flow channel 10 to the cooling plate 7 and the medium raised in temperature through the cooling plate 7 is discharged from the other flow channel 10.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to DLCZ (Doubl
The present invention relates to a support member for supporting a crucible used for pulling a single crystal by the e-Layered Czochralski method.

[0002]

2. Description of the Related Art FIG. 3 is a schematic side sectional view showing an essential part of an apparatus used for pulling a single crystal by a DLCZ method and a conventional crucible supporting member. In the crucible 1 into which the raw materials are charged, a graphite outer container 3 having a similar shape to the inner container 2 is fitted onto a quartz inner container 2 in which a lower portion of a cylindrical straight body is provided with a bowl-shaped lower portion. The crucible 1 is rotated by a support member 24 made of graphite having substantially the same thermal conductivity as that of the outer container 3 and is moved up and down. The supporting member 24 is provided with a crucible tray 25 having a recess formed in the center of the upper surface of the disc, and a rotary shaft 26 attached to the center of the lower surface of the crucible tray 25. The crucible 1 has its bottom at the bottom of the crucible tray 25. It is fitted in the recess and is detachably placed on the crucible tray 25.

On the outside of the crucible 1, a resistance-heating type cylindrical heater 13 is arranged concentrically with the crucible 1. Also, crucible 1
A rod-shaped or wire-shaped pull-up shaft 14 is arranged on the central axis of, and a seed crystal 15 is attached to the lower end of the pull-up shaft 14.

In order to pull a single crystal by the DLCZ method with such an apparatus, after the raw material charged into the crucible 1 is melted by the heater 13 to form a molten liquid, the power of the heater 13 is reduced and the crucible 1 is heated. A solid layer S is grown from the bottom to a predetermined height to form two layers, a solid layer S and a melt layer L.
When the formation of the two layers is completed, the power of the heater 13 is increased to bring the seed crystal 15 attached to the lower end of the pulling shaft 14 into contact with the surface of the melt layer, so that the pulling shaft 14 and the rotating shaft 26 move in opposite directions. The single crystal 16 is placed below the seed crystal 15 by pulling up the pulling shaft 14 at a predetermined speed while rotating.
Grow. Then, as the melt liquid layer L is decreased by pulling up the single crystal 16, the supporting member 24 raises the crucible 1 to keep the surface height of the melt liquid layer substantially constant, and
By melting the solid layer S, the concentrations of oxygen and dopant in the melt layer L are kept constant, and a single crystal 16 of uniform quality in the length direction is obtained.

[0005]

However, the conventional supporting member has the following problems. FIG. 4 is an explanatory diagram for explaining heat conduction in the crucible during pulling a single crystal. The heat Q _h given from the heater 13 to the crucible 1 is conducted to the outer container 3 and the inner container 2 and is given to the molten liquid layer L, but a part of the heat is conducted to the lower part of the bowl in the wall of the outer container 3. Heat Q
_w . At the bottom of the outer container 3, this heat Q _w and heater
While heat from 13 is given, from the bottom of the outer container 3,
Heat Q _e due to radiation and heat due to conduction to the support member are released from the peripheral surface of the outer container 3.

As a result of analysis of these heat quantities by the inventor,
It was found that the balance between the amount of heat radiated from the lower portion of the outer container 3 and the amount of heat input to the lower portion of the outer container 23 was poor, and there was excessive heat input Q _m from the lower portion of the outer container 3 to the solid layer S. This heat input Q
_{In the} step of forming the two layers of the solid layer S and the melt layer L by _m , the growth of the solid layer S is hindered, and it takes a long time to obtain the solid layer S having a required height. There was a problem of low efficiency. Further, during the pulling up, the solid layer S is excessively melted by the heat input Q _m ,
Since the single crystal 16 disappears at an earlier stage than the completion of the pulling, the concentration of oxygen and the dopant in the melt layer L increases with the pulling of the single crystal 16, and the concentration is uniform over the entire length in the length direction. There was a problem that it was difficult to obtain a single crystal 16 of various qualities.

By the way, in Japanese Patent Publication No. 54-4711, heat from the crucible is conducted to the weight sensor provided at the lower end of the rotary shaft for measuring the weight of the crucible and the molten liquid. In order to prevent the detection accuracy of the weight sensor from deteriorating, the lower end of the rotary shaft and its vicinity and the weight sensor are immersed in silicone oil, and water is allowed to flow through the cooling pipe arranged in the silicone oil. Discloses a device for cooling a rotating shaft and a weight sensor.

It is possible to apply such a device to improve the balance between the amount of heat radiated from the lower portion of the outer container and the amount of heat input to the lower portion of the outer container. However, when the present inventor conducted heat transfer analysis, the amount of heat released from the lower portion of the outer container hardly changed even when immersed in silicone oil not only near the lower end of the rotating shaft but also above it. The result was that the balance of payments was not improved.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a crucible tray of a supporting member having a crucible tray on which the crucible is placed and a rotary shaft vertically extending from the crucible tray. The purpose of the present invention is to provide a support member capable of cooling the bottom of the crucible to a required temperature by providing the cooling plate.

[0010]

A supporting member for a crucible for pulling a single crystal according to a first aspect of the present invention comprises a crucible tray and a rotary shaft vertically provided on the crucible tray, and includes a melt layer of a raw material and a solid layer. In a supporting member for supporting a crucible used for pulling a single crystal in coexistence on the crucible pan, a cooling plate is provided on the crucible pan.

The supporting member for the crucible for pulling a single crystal according to the second invention is characterized in that, in the first invention, a circulation path for circulating a cooling medium is formed inside the cooling plate.

In the supporting member of the crucible for pulling a single crystal of the present invention, the bottom of the crucible is cooled down to the required temperature because the bottom of the crucible is forcibly cooled by the cooling plate provided on the crucible tray on which the crucible is placed. Then, in the two-layer formation stage of the solid layer and the melt layer, the solid layer grows to a predetermined height in a short time. Further, during pulling of the single crystal, excessive melting of the solid layer is prevented, the solid layer exists until the end of pulling the single crystal, and a single crystal of uniform quality is obtained over the entire length in the axial direction. To be

A circulation path is formed inside the cooling plate,
A cooling medium such as silicon oil or water is passed through the circulation path to cool the bottom of the crucible. The degree of cooling is adjusted by the flow rate or temperature of the cooling medium.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic side sectional view showing a main part of an apparatus used for pulling a single crystal by the DLCZ method and a supporting member according to the present invention. A crucible 1 for feeding raw materials is arranged in a metal chamber 19. In the crucible 1, a quartz outer container 3 having a bowl-shaped lower portion at the lower end of a cylindrical body is fitted with a graphite outer container 3 having a similar shape to the inner container 2. The crucible 1 is supported by a support member 4. On the outside of the crucible 1, a resistance heating type tubular heater 13 is arranged concentrically with the crucible 1.
13 is housed in a heat insulating container 18 having holes of a predetermined diameter formed on the top and bottom. A rod-shaped or wire-shaped pulling shaft 14 is arranged on the central axis of the crucible 1, and a seed crystal 15 is attached to the lower end of the pulling shaft 14.

The support member 4 is provided with a crucible tray main body 5 having a recess formed in the center of the upper surface of the disc, and a rotary shaft 6 attached to the center of the lower surface of the crucible tray main body 5. A hollow disk-shaped cooling plate 7 having a thickness smaller than the depth of the recess is fitted in the recess of the crucible saucer main body 5, and the cooling plate 7 and the peripheral portion of the crucible saucer main body 5 surrounding the cooling plate 7 are fitted together. The bowl-shaped bottom of the crucible 1 is fitted into the formed recess. The crucible tray body 5 and the rotary shaft 6 are made of graphite having substantially the same thermal conductivity as the outer container 3 of the crucible 1, and the cooling plate 7 is made of metal such as aluminum. The rotary shaft 6 is fixed to a rotary elevating device 40 that performs rotational drive and elevating drive, and the drive of the rotary elevating device 40 causes the support member 4 to rise while rotating the crucible 1.

In order to pull a single crystal by the DLCZ method with such an apparatus, after the raw material charged into the crucible 1 is melted by the heater 13 to form a molten liquid, the power of the heater 13 is reduced and the crucible 1 is heated. A solid layer S is grown from the bottom to a predetermined height to form two layers, a solid layer S and a melt layer L.
When the formation of the two layers is completed, the power of the heater 13 is increased so that the seed crystal 15 attached to the lower end of the pulling shaft 14 is brought into contact with the surface of the melt layer L, and the pulling shaft 14 and the supporting member 4 are moved in opposite directions. While pulling the rotation shaft,
By pulling up 14 the single crystal 16 is grown below the seed crystal 15. Then, as the melt liquid layer L is reduced by pulling up the single crystal 16, the crucible 1 is supported by the support member 4.
To keep the height of the surface of the melt liquid layer L substantially constant, and by melting the solid layer S to keep the concentration of oxygen and dopant in the melt liquid layer L constant, etc. A quality single crystal 16 is obtained.

Inside the rotary shaft 6, there are two passages 10, 10 through which a cooling medium such as silicone oil or water flows in and out,
It is provided in the axial direction of the rotary shaft 6, and the upper ends of the flow passages 10 and 10 penetrate the crucible tray body 5 and are connected to the cooling plate 7.
Two holes communicating with the flow passages 10, 10 are formed in the peripheral surface near the lower end of the rotary shaft 6 at a distance in the axial direction of the rotary shaft 6, and these holes are formed in the rotary shaft 6. A tubular joint member 30 is externally fitted so as to cover the. On the inner peripheral surface of the joint member 30, annular grooves 31, 31 through which the cooling medium flows are formed at positions corresponding to the above-mentioned two holes, and the leakage of the cooling medium is prevented O Rings 32, 32 are attached near the upper and lower ends of the joint member 30. The cooling medium is introduced into the one groove 31 of the joint member 30 from the tank 35 provided with the cooling device by the pump P, and the heated cooling medium is discharged from the other groove 31 to the tank 35 via the cooling plate 7. It has become.

FIG. 2 is a II-II of the cooling plate 7 shown in FIG.
It is an expanded sectional view by a line. Two holes 7a, 7a are formed in the vicinity of the center of the cooling plate 7 having a circular plan view.
The above-mentioned communication channels 10 and 10 (see FIG. 1) are connected to a and 7a, respectively. Inside the cooling plate 7, a plurality of baffle plates 8,
.. are provided, and the baffle plates 8, 8, ... Circulate the cooling medium flowing in from one hole 7a while meandering in the circumferential direction of the cooling plate 7 and flowing out from the other hole 7a. A passage 9 is formed.

Then, a cooling medium is circulated in the circulation passage 9 to cool the bottom of the crucible 1 placed on the cooling plate 7 to a required temperature. This prevents excessive melting of the solid layer S, and in the two-layer formation stage of the solid layer S and the melt liquid layer L, the solid layer S grows to a predetermined height in a short time. Further, during the pulling of the single crystal 16, the solid layer S is prevented from being excessively melted, the solid layer S exists until the end of the pulling of the single crystal 16, and the solid layer S has a uniform quality over the entire length in the axial direction. A single crystal 16 can be obtained.

[0020]

EXAMPLES Next, the results of comparison tests will be described. The following Table 1 shows the results of the comparative test.

[0021]

[Table 1]

In Table 1, the comparative example shows a case where the crucible tray is not provided with a cooling plate. On the other hand, in Example 1, as shown in FIG. 1, when the cooling plate was provided in the crucible tray and water was circulated at 40 liters / minute in the circulation path in the cooling plate,
Example 2 shows a case where water is circulated to the circulation path at 60 liters / minute, and Example 3 shows a case where water is circulated to the circulation path at 80 liters / minute. In addition, after filling the crucible with the raw material and melting it with the heater power of 75 kw, the heater power was lowered to 65 kw and the crucible was lowered by 60 mm to form the solid layer, and the initial solid layer was formed 7 hours after the solid layer was formed. Was measured, and the thickness of the initial solid layer of Comparative Example was used as a reference, and the amount of increase from the reference was used as the initial solid layer thickness. Then, after forming the initial solid layer, the seed crystal was immersed in the melt layer, the single crystal was pulled up under the conditions of the following Table 2, and the length of the single crystal when the solid layer disappeared was measured.
The target single crystal length under the conditions shown in Table 2 is 1300 m.
m.

[0023]

[Table 2]

As is clear from Table 1, the initial solid layer thickness increases as the flow rate of water circulated through the cooling plate increases. Then, when the flow rate is 80 liters / minute (Example 3), the initial solid layer is increased by 70 mm as compared with the comparative example, whereby the length of the single crystal pulled up from the solid layer becomes the target single crystal length. The single crystal could be pulled up by the DLCZ method over the entire length of the target single crystal length.

[0025]

As described above in detail, in the supporting member for the crucible for pulling a single crystal according to the present invention, since the bottom of the crucible is cooled by the cooling plate, two layers of a solid layer and a melt layer are formed. In the stage, the solid layer grows to a predetermined height in a short time. Also, during pulling of the single crystal, excessive melting of the solid layer is prevented, the solid layer exists until the end of pulling the single crystal, and a single crystal of uniform quality is obtained over the entire length in the length direction. That is, the present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view showing a main part of an apparatus used for pulling a single crystal by a DLCZ method and a supporting member according to the present invention.

FIG. 2 is an enlarged cross-sectional view taken along line II-II of the cooling plate shown in FIG.

FIG. 3 is a schematic side sectional view showing a main part of an apparatus used for pulling a single crystal by a DLCZ method and a conventional crucible supporting member.

FIG. 4 is an explanatory diagram illustrating heat conduction in a crucible during pulling of a single crystal.

[Explanation of symbols]

 1 crucible 2 inner container 3 outer container 4 support member 5 crucible saucer body 6 rotating shaft 7 cooling plate 8 baffle plate L molten liquid layer S solid layer

Claims (2)

[Claims] 1. A crucible tray comprising a crucible tray and a rotary shaft extending vertically from the crucible tray, and a crucible used for pulling a single crystal by coexisting a molten layer and a solid layer of a raw material is supported on the crucible tray. A supporting member for a crucible for pulling a single crystal, wherein the crucible tray is provided with a cooling plate. 2. A supporting member for a crucible for pulling a single crystal according to claim 1, wherein a circulation path for circulating a cooling medium is formed inside the cooling plate.