JP2740239B2 - How to pull a crystal - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a crucible which is arranged in a vacuum chamber and which can be heated by the heat rays of a heating body, and which is provided on a melt and moves crystals upward from the surface of the melt. The melt in the crucible under a reduced pressure protective gas or vacuum using a pull-up member that pulls up towards and a supply tube that after-loads the charge from the rear charging device into the crucible during the lifting operation. And a method for pulling a crystal from a crystal.

2. Description of the Related Art Known methods or devices for pulling crystals are usually
The melting crucible is filled with the required amount of molten material, for example silicon granules, in addition to the required doping material (for example boron, antimony or phosphorus) before evacuating the container surrounding the melting crucible. It has already been proposed to reload silicon granules during the rod pull-up operation (DE-OS2821481),
In this case, the granules are post-filled through a heated quartz glass tube which is immersed in the silicon melt from the outside through the exhaust bell wall and the outer part of the device.

It is also known to arrange a supply device for silicon granules outside the container (EP 0 170 856), in which case the outlet pipe of the supply device is connected to a cylindrical tank partially filled with granules. A metering disk that is driven by a motor and rotates is arranged in this tank. The metering disc has a recess, which is filled with granules when the disc is charged with the amount of granules stored on one side of the tank. The disc then carries the received granules in front of one end of the outlet tube, whereby the granules can slide through the outlet tube into the melting crucible. The cylindrical tank is also connected to a second tank in which the granules are stored via a connecting piece to which a lock gate valve is connected. A manually operable piston then transports the granules to the connecting piece when the valve is opened, and thus to the tank with the metering disc.

In the end, a conventional device for continuously feeding molten material to the melting crucible when pulling crystals in a vacuum vessel, i.e. a closable tank, a lock gate valve, and one tank open to the melting crucible According to the device (P3737051.0) with an outflow pipe connected to the tank, the first tank has an inner lining corresponding to the tank shape, a hopper-shaped section, and a cylindrical section connected to the section. An outlet is provided, in which case the outlet can be moved via a lock gate valve into the connecting piece of the second tank provided with the granule transporter, the granule transporter itself being evacuated It opens into the upper region of the melting crucible via an outlet tube penetrating the vessel wall.

It has been found that with such a device, particularly in the area of the bath surface of the crucible insert, particularly after a short period of operation, particularly high wear occurs on the crucible edge. The crucible material is particularly strongly affected by the melt at this point, which results in the formation of annular gaps or grooves in the inner surface of the crucible insert, whereby the useful life of this expensive part of the device is significantly reduced. I will.

It is therefore an object of the present invention to provide a method suitable for reducing such wear phenomena on the inner wall of the crucible insert and significantly extending the useful life of the crucible insert.

In order to achieve this object, the method according to the invention provides, in a method of the type described at the outset, a minimum amount of melt in relation to the amount of melt present in the crucible in each case. After being consumed, the melt material is post-charged to a higher fill above the target amount, and the melt surface is raised and lowered uniformly around a specified level in the crucible during the crystal pulling operation. ,
In addition, at this time, the crucible is simultaneously moved up and down by the elevating device in relation to the amount of the melt at that time, so that the distance between the surface of the melt and the lid for fixing the position of the container is kept constant. .

By employing the method according to the invention, the width of the contact line between the melt surface and the inner wall of the crucible insert is defined while maintaining the absolute height position of the melt surface constant. Can be moved up and down, so that the wear phenomenon on the inner wall, which has been a problem in the past, can be reduced, and the useful life of the crucible insert can be significantly extended.

Embodiment Next, an embodiment of the present invention will be described with reference to the drawings.

The device shown in FIG. 1 is mounted on a double-walled container 4, which is mounted on a double-walled container bottom plate 3 of the device frame and forms a vacuum chamber 52, and is arranged in this container 4. A supporting tube 5 supported on the container bottom plate 3, a heat insulator 6 surrounding the supporting tube, a ring-shaped tank 7 held by the supporting tube 5, a graphite felt plate 8 supported in the tank, Two power supply bodies 9 that work to supply power to the bottom heating body 10 held on the tank 7 and are held on the container bottom plate 3;
Another two power feeders 11 held by the container bottom plate 3, a tension jaw 12 screwed to each of the power feeders, and an end face heating body or a cylindrical portion heating body 13 supported by the tension jaws 12.
A melting crucible 14, a hot-wire preventing tube 15 supported by the tank 7 and provided with a heat insulator 16 on the side, a cover plate 17 supported by the hot-wire preventing tube, and an upper end face of the cover plate. And a through-hole 19 also provided in the cover plate 17 and provided with a protective glass 21.
A through hole 20 having a notch 22, a supply pipe 23 for the charging material, a filling hopper 24 passing through the cover plates 17, 17a, and a rotatable and operable to hold a crucible support pin 26. And a crucible shaft 25 that can be raised and lowered.

The bottom heating element 10 held by the two power supply elements 9 comprises two heating element feet 31 arranged opposite one another and two winding elements 2 connected to the two heating element feet and each having a meandering shape.
And one heating coil 33 (only one of which is shown in the drawing). The heating coils 33 together form an opening 35 in the center of the bottom heater 10 and a crucible support pin 26 extending through this opening. This support pin is rigidly connected at its upper end to the support crucible 14, via which the crucible insert 28 is moved up and down and rotated together with the support crucible 14. Edge heating body 13
Consists of a circular ring-shaped flat part 38 with a radially extending slit 36 and a hollow cylindrical side part 39. This hollow cylindrical part 39 has two opposite
One of the two parts has a downwardly extending heating element foot 40, each of which is associated with a notch 41 provided in both clamping jaws 12 held by the power supply 11. I agree. End face heating body at both notches 41 of tensioning jaw 12
13 trapezoidal cutouts 41 to ensure reliable current transfer
An additional wedge 42 is pushed into the.

The heat ray prevention tube 15 has four rectangular notches 43, 43a,..., And these notches are uniformly distributed over the entire circumference of the heat ray prevention tube 15 and are provided at the edge of the heat ray prevention tube. Are located. Through these cutouts 43, 43a,.., The tensioning jaws 12 extend on the one hand and the heating element feet 31 of the bottom heating element 10 extend on the other hand.
Further, the heat ray prevention tube 15 has a hole 45 extending obliquely,
This hole is aligned with the protective glass 21 of the cover plates 17, 17a and the protective glass 46 of the tube piece 47 fixed to the wall of the container 4. Another opening 98 provided in the side wall of the heat ray prevention tube
Allows unimpeded gas flow from the upper section to the lower section of the interior of the container 4. The container 4 further has a collar 48 in the area of its lid portion 4a, which collar is
Allow the penetration of Furthermore, a second tube piece 50 provided with a sight glass 51 and a third tube piece 63 provided with a sight glass 64 are provided in the lid portion 4 a of the container 4.

A bottom heater 10 having a meandering slit is screwed to the second power supply 9 via a graphite nut 27. The bottom heater 10 has the task of heating the crucibles 14, 28 or the melt from the lower end surface. A second heating element 13 configured as a pot-shaped heating element is fixed to the two additional power supplies 11 via a clamping jaw 12.
Heating the upper end surface improves the melting of the continuously supplied charge. The end face heating body 13 may be coated with SiC in the case of a silicon melt. With this configuration, it is possible to prevent the graphite particles from dropping into the melt and generating carbon and impurities. Further, the reaction between SiO and graphite (2C + SiO → SiC + CO) can be avoided. The dashed argon gas flow is
It is guided downwardly through the opening 98 through the central opening 53, past the melt, bypassing the crucible 14 via 48, and withdrawn through the tube piece 60.

Located in the center of the heating device is a graphite crucible 14 into which a crucible 28 made of a material that does not react with the melt is inserted. To assure bath sedation during loading during lifting operation,
An additional ring of material which also does not react with the melt
29 is inserted into the crucible 29. The lower end of the ring 29 is provided with a plurality of cutouts 30 through which the molten charge can flow into the center of the crucible insert 28. Heat insulation around both heating elements 10 and 13
8, 16 and 18 are provided. The heat insulator comprises a graphite felt plate 8 supported on the tank 7 and a side heat insulator 16 which is formed as a cylinder and which is inserted into the heat ray prevention tube 15. And a circular ring-shaped heat insulator 18 on the upper end face side. The upper cover plates 17, 17a are supported on the cylindrical inner surface of the container 4 together with the heat insulator 18.

A guide tube 32 is fixed to the lid portion 4a of the container 4 near a collar 48 through which a lifting member 49 is passed, and a rod 34 is supported on the guide tube so as to be slidable in the longitudinal direction. Is configured as a threaded spindle 37. The screw spindle is engaged with a drive shaft 57 driven by the motor and transmission unit 54. At the crucible-side end (lower end) of the rod 34, a chuck 58 is provided, in which a thin rod 56 made of a highly doped material is provided with a notch 22 of the through hole 20 and a slit 36. Tightened to match.

In order to keep the composition of the melt constant, the highly doped thin rod 56 can be moved vertically downward into the melt using the motor and transmission unit 54 and upward from the melt. It is possible to advance. When the rod 56 is immersed in the bath of the melt, the dipped end of the rod 56 melts, whereby the composition of the melt is adjusted and kept constant.

The filling state of the melt in the crucible insert 28
Monitored by a device consisting of 65 (laser light sources). In this case, the transmitter is mounted on a tube 63 provided with a viewing glass 64, the measuring beam of which is directed at the melt surface 55. The reflection of the measuring beam (for example a laser beam) is then received by a pulse receiver 68 (laser receiver) mounted on a tube 66 and evaluated in an electric switching circuit or program controller 74. The device is now
A signal corresponding to the instantaneous melting state is generated and this signal can be sent to a granule conveyor or a vibration device in the lower tank 76.

The melt in the region of the melt surface 55 acts strongly on the quartz crucible insert 28 in the region of the melt surface within a relatively short operating time, in order to avoid that the crucible insert becomes unusable. In order for the molten material to be inserted after the supply pipe
Performed from the rear insertion device 72 via 23 and the filling hopper 24,
In this case, the melt surface 55 is first lowered to a small value below the target level and then filled to a small value above the target level. In other words, the melt material is the crucible insert
The melt charge at 28 is post-charged such that it remains alternately somewhat above or below the target level for a defined time.
To achieve this effect, the rear charging device 72 is electrically controlled via a program which is processed by an electric switching circuit 74 in connection with the signals from the devices 63-68. The rear charging device itself is an upper tank 75 containing the granular charge.
And a supply pipe provided with a vibrating device or a transporter to supply the charged material.
23 and the associated operating device 76 which is connected to a pipe piece connecting the two tanks 75, 76 to one another
And a lock gate valve 71 provided with (This type of rear loading device is disclosed in the prior patent application P3737051.0
Detailed description).

Further, the crucible shaft 25 can be shifted vertically.
It has a collar 86 for this purpose. The crucible shaft 25 is supported by a roller bearing 87 of a pressing member 88 with its collar, and the pressing member is guided in the hole 89 so as to be movable in the direction of arrow A. The pressing member 88 itself is supported by a piston 90 of the hydraulic cylinder 83, and the hydraulic cylinder 83 is connected to a pressure conduit.
The solenoid valve 82 and the hydraulic pump 81 configured as a multi-port switching control valve are connected via 91 and 92. solenoid valve
82 is controllable via a signal line 85, whereby the piston 90 moves the crucible shaft 25 together with the crucible support pin 26, the crucible 14 and the crucible insert 28 together with the pressure medium pumped by the hydraulic pump 81 into the pressure line 91. Via hydraulic cylinder 83
Up or down, depending on whether it is fed into or discharged into the pressure medium storage tank 84 via the return conduit 93. As soon as the melt surface 55 begins to descend, the crucible
14, 28 are lifted by the pressure build-up in hydraulic cylinder 83, and this operation continues until the melt surface reaches its target level again. Therefore, when rear charging is performed, the crucibles 14, 28 must be lowered. In this manner, the crucible can be constantly and uniformly moved up and down, and as a result, premature wear of the crucible insert 28 can be prevented.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an apparatus for performing the method according to the present invention. 3 ... container bottom plate, 4, 4a ... container, 5 ... support tube, 6, 16, 1
8 ... heat insulator, 7 ... tank, 8 ... graphite felt plate, 9, 11 ... feeder, 10 ... bottom heating body, 12 ... tension jaw, 13 ... end face heating body, 14 ... Supporting crucible, 15…
… Heat-prevention tube, 17,17a …… Cover plate, 19,20 ……
Through-hole, 21: Protective glass, 22: Notch, 23: Supply pipe, 24: Filling hopper, 25: Crucible shaft, 26: Crucible support pin, 27: Graphite nut, 28: Crucible Insert, 29 …… Ring, 30 …… Notch, 31 …… Heating body foot, 32 …… Guide tube, 33 …… Heating tube, 34 …… Rod, 35
…… Aperture, 36 …… Slit, 37 …… Screw spindle, 38
... heating element, 39 ... side part, 40 ... heating body foot, 41 ...
… Notch, 42 …… Wedge, 43, 43a …… Notch, 45 ……
Holes, 46,51,64,67 …… Peep glass, 47,50,60,63,66 ……
Tube piece, 48 ... Collar, 49 ... Pulling member, 52 ... Vacuum chamber, 53 ... Opening, 54 ... Motor / transmission unit, 55
…… Molten surface, 56 …… Rod, 57 …… Drive shaft, 58 ……
Chuck, 59: heating element, 61: crystal, 62: supply device, 65: transmitter, 68: receiver, 70: operating device, 71
… Lock gate valve, 72… Rear charging device, 73… Crucible rim, 74… Switching circuit, 75, 76… Tank, 77-79…
Signal conductor, 80 …… Lower frame, 81 …… Hydraulic pump, 82
…… Electromagnetic valve, 83… Hydraulic cylinder, 84… Pressure medium storage tank, 85 …… Signal wire, 86 …… Flange, 87 …… Roller bearing, 88 …… Pressing member, 89 …… Hole, 90 …… Piston, 91,9
2 …… Pressure conduit, 93… Return conduit, 98 …… Opening

Claims (1)

(57) [Claims] 1. A crucible (14, 28) arranged in a vacuum chamber (52) and capable of being heated by the heat rays of a heating body (10, 59).
And a pulling member (4) provided on the melt and pulling the crystal (61) upward from the melt surface (55).
9) and a supply pipe (23) for post-filling the charging material from the rear charging device (72) into the crucible (14, 28) during the lifting operation, under reduced pressure protective gas or vacuum. In the crucible (1
4. A method of pulling crystals (61) from the melt in (4,28), wherein the amount of melt is consumed to a minimum in relation to the amount of melt each time present in the crucible (14,28). After
The melt material is post-charged to a higher filling volume than the target volume, so that the melt surface (55) is evenly centered around the defined level in the crucible (14,28) during the crystal pulling operation. The crucible (14, 28) is moved up and down at the same time and at the same time and in relation to the amount of the melt at that time, by means of a lifting device (81-84) to move the crucible (14, 28) up and down.
5. A method for pulling a crystal, characterized in that the distance between the container (4) and the fixed lid part (4a) of the container (4) is kept constant.