DE102008035439A1 - Device for breeding crystals from electroconductive melts, comprises breeding chamber having a vertical chamber wall and a chamber base, and a crucible and a heating unit, which are arranged in the breeding chamber - Google Patents

Abstract

The device comprises breeding chamber (5) having a vertical chamber wall and a chamber base. In the breeding chamber, a crucible containing electroconductive melts (7), and a heating unit (1) surrounding the crucible are arranged. The heating unit is implemented as multiple-coil arrangement of coils arranged one above the other and used to simultaneously generate a magnetic gliding field. Current feeds are arranged to the coils and are electrically connected with current supply devices arranged external of the breeding chamber. The device comprises breeding chamber (5) having a vertical chamber wall and a chamber base. In the breeding chamber, a crucible containing electroconductive melts (7), and a heating unit (1) surrounding the crucible are arranged. The heating unit is implemented as multiple-coil arrangement of coils arranged one above the other and used to simultaneously generate a magnetic gliding field. Current feeds are arranged to the coils and are electrically connected with current supply devices arranged external of the breeding chamber. The current feeds are connected with current guiding elements that are led through the vertical chamber wall of the breeding chamber. The current feeds are arranged horizontal between the coils and the chamber wall. The current feeds are connected with three hollow cylinders arranged around the heating unit. The hollow cylinders are connected with the current guiding elements that are brought through the chamber base of the breeding chamber. The current guiding elements are electrically connected over flow lines external of the breeding chamber with the current supply device. The hollow cylinders are made from graphite. An area surrounded by coil windings (9) has any geometric form. The heating unit comprises two stabilizing elements on the coil windings. The stabilizing elements are arranged as cylindrical rods with nut-shaped notch and two plates. The stabilizing elements are arranged coaxially along the coil external side. The nut-shaped notch grips in the coil windings of the coil or the plates lie between the coil windings. The coil windings are arranged spiral or cascade shaped manner. The winding cross-section of the coil winding has any geometric form.

Description

The The invention relates to a device for producing crystals from electrically conductive melts.

For a favorable influence on crystallization processes, it is known to use magnetic fields which dampen the harmful convection instabilities of the melt or intensify intermixing, whereby a reduced degree of contamination is incorporated into the crystallizing phase (cf. DTJ Hurle, Handbook of Crystal Growth, Vols. 2a-b, Elsevier, North Holland 1994 or K.-Th. Wilke, J. Bohr, Crystal Growth, H. Deutsch-Thun, Frankfurt a. M. 1988 ). For this purpose, usually the magnetic coils are mounted outside the culture chamber. In order to achieve the desired Lorentz forces in the melt, however, must flow in such outer coils very high currents, because on the one hand the distance of the coil to the crucible is large and because on the other hand, the container wall has a shielding effect on magnetic fields.

Therefore, devices for the production of crystals are known in which the current flowing in the heater is used simultaneously to generate non-stationary magnetic fields (see. Rudolph, J. Crystal Growth 310 (2008) 1298 ). There are heater arrangements which generate a magnetic rotating field ( DE 3750382 T2 ) and there are also heater arrangements that simultaneously generate a magnetic traveling field ( DE 102007020239 A1 ). The aim of these heater arrangements is to produce not only the thermal effect but also forces in the melt, which can have different effects. With the help of a magnetic rotating field one can set the melt in rotation in order to achieve a better mixing. With a magnetic traveling field one can also achieve a better mixing of the melt or one can also generate Lorentz forces in the melt in such a way that the natural convection is suppressed by counteracting the buoyancy forces.

In DE 10349339 A1 a graphite heater is proposed, which consists of 3 partial heaters, which are connected in delta connection. Due to the phase-shifted currents in the sub-coils, a magnetic traveling field is generated, which in turn causes Lorentz forces in the melt. In 1 of the DE 10349339 A1 you can see that the vertical power supply leads close to the heater down. Numerical models of such a heater magnet arrangement result in a significant disadvantage as a strong asymmetry of the coupled Lorentz force distributions (see. H. Kasyanov et al., J. Crystal Growth 310 (2008) 1540 ). Also in Scripture DE 102007020239 A1 a device is described as a Mehrheizeranordnung for generating a traveling magnetic field, which has a plurality of vertical power supply lines, which also run unfavorably close to the coil assembly here.

For the generation of advantageous rotationally symmetric traveling magnetic fields only the current flowing in the coil is important. Of the generates current flowing in the power supply lines Inhomogeneities in the magnetic field, which are also in an inhomogeneous Defeat the distribution of forces. In breeding procedures, where neither the breeding vessel nor the crystal rotates in the vertical gradient freeze method (VGF method), Bridgman method, heat exchanger method or block solidification method, are both the buoyancy (due to hotter zones in the melt near the stoker), as well as Lorentz forces crucial for the shape of the phase boundary. One strives here for the most even possible form of the phase boundary to minimize stresses in the crystal. A flat phase boundary is also particularly in the edge region of the crucible for the Production of single crystals important here to the emergence of To prevent polycrystalline growth. These are strictly rotationally symmetric Magnetic fields required.

The in the prior art, inter alia, in DE 102007020239 A1 used vertically, ie along the coil outer sides arranged power supply leads to inhomogeneities of the magnetic field and thus to an inhomogeneous distribution of Lorentz forces within the melt. The shape of the phase boundary can thereby deviate greatly from the planar shape.

in the The prior art also angular power supply but with horizontal and vertical sections an enlarged clearance (inner diameter) of the boiler and require a complicated geometry of the insulation body.

task The invention is an apparatus for producing crystals to provide from electrically conductive melts, with the unwanted Induction currents are prevented in the melt and which improves the quality of the crystals to be produced becomes.

The Task is solved with a device with the features of claim 1.

Thus, the apparatus according to the invention for growing crystals of electrically conductive melts, with a growth chamber having a vertical chamber wall and a chamber bottom, in the growth chamber, a crucible containing the melt and a surrounding the crucible Heating device are arranged, which is designed as a multi-coil arrangement of superimposed coils having a plurality of coil windings and the simultaneous generation of a traveling magnetic field, are arranged on the power supply leads, which are electrically connected to a power supply device arranged outside the cultivation, characterized in that the Power supply lines are connected to current feedthrough elements which are guided through the vertical chamber wall of the cultivation chamber, wherein the power supply lines are arranged horizontally between the coils and the chamber wall, or the power supply lines are connected to one another, arranged around the heater hollow cylinders, the hollow cylinder connected to current feedthrough elements are, which are passed through the chamber bottom of the culture chamber.

The Invention offers two solutions, unwanted To prevent inhomogeneities in the magnetic field: the first Solution provides that the power supplies as formed substantially horizontally arranged busbars are in this arrangement, namely horizontally over Current passage elements led out of the breeding chamber become. Vertical power supply sections exist in this solution variant within the culture chamber no more. When carrying out the power supply with only horizontal power supply sections an induction of currents resulting from the current flow of additional vertical power supply sections come as they are known in the art, and which lead to asymmetries in the flow generated by the coil heater would, prevented. The power supply exist made of high temperature resistant material, preferably graphite or made of carbon fiber composite material (CFC).

at the second solution are the power supplies off horizontal (horizontal) and vertical power supply sections educated. The vertical sections have a special design: They are designed according to the invention as a hollow cylinder. This embodiment serves the purpose of symmetrizing the magnetic Traveling fields. To several power supply for To guarantee the coil segments are hollow cylinders with different Diameters inserted into each other, but without each other electrically to contact. The advantage of such a supply line modification is not only a perfect rotational symmetry and a reduced electrical resistance but also saving additional thermal insulation bodies, since such supplies Configuration at the same time advantageous thermal insulation quality exhibit.

The Arrangement of a hollow cylinder as a vertical power supply section has the following further advantage: Inside the hollow cylinder (room the inner diameter) no magnetic field is generated. Therefore around the heater only that generated by the coils Magnetic field effective.

to Generation of magnetic traveling fields is a coil arrangement of at least two coils.

The inventive device can in those Crystal growing systems are used, which after the vertical Bridgman or gradient freeze method, but also after the Kyropolus and Heat Exchanger method and the blocker solidification method work. This device is suitable both for breeding Single crystals as well as for the production of polycrystalline semiconductor material suitable.

Further advantageous embodiments of the invention Device are included in the subclaims.

In A preferred embodiment of the invention provides that the current feedthrough elements outside the breeding chamber over Power lines electrically connected to the power supply device are. The power supplies are inventively until led to the chamber wall of the breeding chamber, where they are contacted with current feedthrough elements. The current feedthrough elements are guided through the vertical chamber wall. They persist preferably made of copper and are mostly water cooled, to dissipate the heat losses at high currents. They are surrounded by an insulating material, so they face each other the culture chamber are isolated. In addition to the function, To conduct the electric current, they also have the function, the Interior of the breeding chamber opposite the environment seal. Outside the breeding chamber are the power supply via power lines with the Energy supply device connected. The power lines are designed as a copper cable. The magnetic effect of the copper Power lines on the melt is because of the shielding effect the metallic growth chamber negligible.

In the other solution variant, the hollow cylinder for Breeding chamber floor led, where they are with current feedthrough elements are contacted, who have the same structure and the same Function as the horizontally led out power supply fulfill.

A next preferred embodiment of the invention provides that the hollow cylinder of Gra phit are formed. The hollow cylinders are preferably made of graphite or other high temperature resistant material.

In Another preferred embodiment of the invention is characterized characterized in that at least three hollow cylinders are provided.

A Another preferred embodiment of the invention provides that a area enclosed by the coil turns any has geometric shape.

The Heating device can be formed from cylindrical coils be, at the area enclosed by the coil turns area therefore forming a circle. There are also more geometric designs the heater conceivable. For example, the heater from heating segments with quadrangular heating coils or oval shaped ones Heating windings exist or any other configuration exhibit.

In a next preferred embodiment of the invention is provided that the heater stabilizing elements has at the coil turns.

By the attachment of the stabilizing elements will collapse the mechanically unstable Heizerwindungen avoided and another Parameters for influencing the thermal and the magnetic Field, namely varying or constant distances between the individual turns, given.

A Another preferred embodiment of the invention provides that the Stabilizing elements as cylindrical rods with at least a groove-shaped notch are designed. A functional one Design of the stabilizing elements is that these as cylindrical rods with groove-shaped notches are formed.

A next preferred embodiment of the invention provides that the stabilizing elements as cylindrical rods are configured with at least two platelets.

In this further advantageous embodiment of Stabilizing elements are the stabilizing elements as cylindrical Formed bars with platelets contained therein.

In a further preferred embodiment of the invention is provided in that the stabilizing elements are coaxial along the coil outside are arranged, wherein the groove-shaped notches in the coil turns of the coils grip or the platelets lie between the coil turns.

The Stabilizing elements ensure that over the entire length of the heater or a coil length the winding pitch mechanically stable and constant or stable and expanding or decreasing to set a temperature gradient is held.

A next preferred embodiment of the invention provides that at least two stabilizing elements are present. The Coil windings of the heater are by the attachment of supported at least two stabilizing elements, the are preferably arranged at a certain distance.

A Another preferred embodiment of the invention provides that the Coil turns spiral or stepped are designed.

The spiral or step ascending current paths, the the coils of the heater from pure graphite form, have a specific winding cross-section and certain winding distances on that on current flow of certain strength on the one hand the melting temperature of the respective breeding substance reached or exceeded up to about 100 ° C and on the other hand with the same amperage but more optimized Phase shift (phase angle) and frequency of the alternating current magnetic traveling field generated with such Lorentz forces which opposes the convection-induced buoyancy in the melt is, this reverses or reverses or the convection flow in the melt is rectified and reinforced.

In another preferred embodiment of the invention is provided, that a winding cross-section of the coil turns any has geometric shape. The cross section of the coil turns can be round, oval, square or any other geometry.

The Invention will be hereinafter in an embodiment and explained in more detail by means of drawings.

It demonstrate

1 a schematic representation of a crystal growing plant according to the invention viewed in cross-section,

2 a section of the crystal growing plant after 1 in plan view,

3I a schematic representation of stabilizing elements with groove-shaped Einkerbun gene,

3I a schematic representation of the stabilizing elements with groove-shaped notches and the adjacent coil turns,

3III a schematic representation of the stabilizing elements with platelets,

4 a further schematic representation of a crystal growing plant in cross section,

5 another illustration of the crystal growing plant after 4 and

6 another section of the crystal growing plant after 4 in perspective view.

In 1 the schematic representation of a crystal growing plant according to the invention is shown in cross-section.

In a breeding chamber 5 there is a crucible 6 that a melt 7 contains. The crucible 6 is from a heater 1 surround. Shown is also one from the melt 7 solidified crystal 8th ,

The heater 1 is made of three superimposed coil 1a . 1b . 1c built up. The three coil turns 9 the coils 1a . 1b . 1c have a winding cross-section Q. The spools 1a . 1b . 1c each have a coil length L _a , L _b , L _c .

At the coils 1a . 1b . 1c are electrically conductive power supply 4a . 4b . 4c . 4d . 4e . 4f , The power supply lines 4a . 4b . 4c . 4d . 4e . 4f are up to the chamber wall 14 the breeding chamber 5 where they are with the current feedthrough elements 2a . 2 B . 2c . 2d . 2e . 2f are contacted. The current feedthrough elements 2a . 2 B . 2c . 2d . 2e . 2f are made of copper and are through the breeding chamber 5 guided. Outside the breeding chamber 5 are they over power lines 16a . 16b . 16c . 16d . 16e . 16f with a power supply device 11 electrically connected.

1 also shows the on the heater 9 attached stabilizing elements 3a . 3b . 3c ,

2 shows a section of the crystal growing plant 1 in plan view. Shown is a heater 1 within the breeding chamber 5 is arranged. At the (not visible in this representation) coils 1a . 1b . 1c the heater 1 are power supplies 4a . 4b . 4c . 4d . 4e . 4f appropriate. These are about fasteners 17a . 17b . 17c . 17d . 17e . 17f in the form of carbon fiber composite (CFC) screws with the coils 1a . 1b . 1c the heater 1 connected. The power supply lines 4a . 4b . 4c . 4d . 4e . 4f are at the other end with current feedthrough elements 2a . 2 B . 2c . 2d . 2e . 2f connected. The connection is made via fastening means 18a . 18b . 18c . 18d . 18e . 18f in the form of molybdenum screws. The current feedthrough elements 2a . 2 B . 2c . 2d . 2e . 2f are through the vertical chamber wall 14 guided. This will be the power supplies 4a . 4b . 4c . 4d . 4e . 4f horizontally from the chamber wall 14 the breeding chamber 5 led, so that within the breeding chamber 5 there are no vertical power supply sections.

2 also shows the arrangement of the stabilizing elements 3a . 3b . 3c at the heater 1 at an angle of 120 ° each between the (not visible here) coil turns 9 arranged.

3I to 3III show various embodiments of the stabilizing elements 3a . 3b . 3c in a schematic representation.

The stabilizing elements 3a . 3b . 3c consist of high-temperature ceramic and support the mechanical stability of the heater 1 , They provide equidistant or variable winding distances.

So will in 3I the schematic representation of the stabilizing elements 3a . 3b . 3c with groove-shaped notches 12 shown. The groove-shaped notches 12 have such dimensions, they in the coil turns 9 the coils 1a . 1b . 1c fit. The stabilizing elements 3a . 3b . 3c act as spacer rods between the turns.

3II shows how the coil turns 9 the coils 1a . 1c 1c in the groove-shaped notches 24 the stabilizing elements 3a . 3b . 3c . 3d to grab.

3III shows another embodiment of the stabilizing elements 3a . 3b . 3c in the form of platelets 10 made of corundum, which are pushed onto a cylindrical rod. Alternatively, the groove-shaped notches 14 through these tiles 10 be pushed from appropriate material on the rods and placed between the turns. These tiles 10 may have the same but also different thicknesses and thus also allow a variation of the winding distances. A fixation of the platelets 10 through the stabilizing elements 3a . 3b . 3c is necessary around, by the vibration of the heater 1 triggered movement, limit.

4 shows a further schematic representation of a crystal growing plant in cross section. Shown are those around the heater 1 arranged vertical power supply sections, here as a graphite hollow cylinder 13a . 13b . 13c . 13d . 13e . 13f are executed. The graphite hollow cylinder 13a . 13b . 13c . 13d . 13e . 13f are placed inside each other and around the heater 1 arranged around.

In 4 is shown as each coil connection of the three superimposed coils 1a . 1b . 1c via a separate hollow cylindrical power supply, the graphite hollow cylinders 13a . 13b . 13c . 13d . 13e . 13f is powered. The connection between the coils 1a . 1b . 1c and the graphite hollow cylinders 13a . 13b . 13c . 13d . 13e . 13f via the horizontal power supply 4a . 4b . 4c . 4d . 4e . 4f , The graphite hollow cylinder 13a . 13b . 13c . 13d . 13e . 13f are up to the bottom of the chamber 15 the breeding chamber 5 where they are with the current feedthrough elements 2a . 2 B . 2c . 2d . 2e . 2f to contact. The current feedthrough elements 2a . 2 B . 2c . 2d . 2e . 2f are through the chamber floor 15 and over the existing copper cables power lines 16a . 16b . 16c . 16d . 16e . 16f outside the breeding chamber 5 with the power supply device 11 electrically connected.

5 shows a further illustration of the crystal growing plant 4 , In contrast to 4 is in 5 shown as the three coils 1a . 1b . 1c each with a coil end with a common graphite hollow cylinder 13g via the horizontal power supply lines 4g . 4g ₁ and 4g ₂ are connected. The other coil end of the coils 1a . 1b . 1c is in each case with the graphite hollow cylinders 13a . 13b and 13c via the horizontal power supply lines 4a . 4b and 4c connected. If 120 ° deviating phase shifts should be adjustable, the common graphite hollow cylinder 13g and thus the common vertical power supply section 13g in the chamber floor 15 with a current feedthrough element 2g be connected, in turn, with a reference potential of the power supply device 11 via a common power line 16g connected is. The other graphite hollow cylinders 13a . 13b . 13c are in the chamber floor 15 the breeding chamber 5 also with current feedthrough elements 2a . 2 B . 2c contacted.

6 shows a further section of the crystal growing plant 4 in perspective view.

They can be recognized within the breeding chamber 5 nested graphite hollow cylinder 13a . 13b . 13c . 13d . 13e . 13f as they concentric around the coils 1a . 1b . 1c the heater 1 are arranged around. For the sake of clarity, only one of the horizontal power supply lines 4a that with the coil 1a and the hollow cylinder 13a is connected and the arrangement of the stabilizing elements 3a . 3b . 3c on the coils 1a . 1b . 1c ,

1

heater

1a

Kitchen sink

1b

Kitchen sink

1c

Kitchen sink

2a

Current through element

2 B

Current through element

2c

Current through element

2d

Current through element

2e

Current through element

2f

Current through element

3a

stabilizing element

3b

stabilizing element

3c

stabilizing element

3d

stabilizing element

4a

power supply

4b

power supply

4c

power supply

4d

power supply

4e

power supply

4f

power supply

5

growing chamber

6

crucible

7

melt

8th

crystal

9

turn; coil turn

10

Tile

11

Power supply means

12

grooved notch

13a

Graphite hollow cylinder

13b

Graphite hollow cylinder

13c

Graphite hollow cylinder

13d

Graphite hollow cylinder

13e

Graphite hollow cylinder

13f

Graphite hollow cylinder

13g

Graphite hollow cylinder

14

(vertical) chamber wall

15

chamber floor

16a

power line

16b

power line

16c

power line

16d

power line

16e

power line

16f

power line

16g

power line

17a

fastener

17b

fastener

17b

fastener

17c

fastener

17d

fastener

17e

fastener

17f

fastener

18a

fastener

18b

fastener

18c

fastener

18d

fastener

18e

fastener

18f

fastener

L _a

coil length

L _b

coil length

L _c

coil length

Q

winding cross

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3750382 T2 [0003]
• - DE 102007020239 A1 [0003, 0004, 0006]
• - DE 10349339 A1 [0004, 0004]

Cited non-patent literature

• - DTJ Hurle, Handbook of Crystal Growth, Vols. 2a-b, Elsevier, North Holland 1994 [0002]
• - K.-Th. Wilke, J. Bohr, Crystal Growth, H. Deutsch-Thun, Frankfurt a. M. 1988 [0002]
• - Rudolph, J. Crystal Growth 310 (2008) 1298 [0003]
• - H. Kasyanov et al., J. Crystal Growth 310 (2008) 1540 [0004]

Claims (12)

Apparatus for growing crystals of electrically conductive melts ( 7 ), with a growth chamber ( 5 ), which has a vertical chamber wall ( 14 ) and a chamber floor ( 15 ), in the culture chamber ( 5 ) a melt ( 7 ) contained crucible ( 6 ) and a crucible ( 6 ) surrounding heating device ( 1 ) arranged as a multi-coil arrangement of superimposed coils ( 1a . 1b . 1c ) with several coil turns ( 9 ) is carried out and which serves for the simultaneous generation of a traveling magnetic field, at the coils ( 1a . 1b . 1c ) Power supplies ( 4a . 4b . 4c . 4d . 4e . 4f . 4g ) are arranged with one outside the culture chamber ( 5 ) arranged power supply device ( 11 ) are electrically connected, characterized in that the power supply lines ( 4a . 4b . 4c . 4d . 4e . 4f . 4g ) with current feedthrough elements ( 2a . 2 B . 2c . 2d . 2e . 2f . 2g ), which pass through the vertical chamber wall ( 14 ) of the culture chamber ( 5 ) are guided, wherein the power supply ( 4a . 4b . 4c . 4d . 4e . 4f . 4g ) horizontally between the coils ( 1a . 1b . 1c ) and the chamber wall ( 14 ), or the power supply lines ( 4a . 4b . 4c . 4d . 4e . 4f . 4g ) with one another in order to connect the heating device ( 1 ) arranged around hollow cylinders ( 13a . 13b . 13c . 13d . 13e . 13f . 13g ), the hollow cylinders ( 13a . 13b . 13c . 13d . 13e . 13f . 13g ) with current feedthrough elements ( 2a . 2 B . 2c . 2d . 2e . 2f . 2g ), which pass through the chamber floor ( 15 ) of the culture chamber ( 5 ) are guided. Device according to claim 1, characterized in that the current feedthrough elements ( 2a . 2 B . 2c . 2d . 2e . 2f ) outside the culture chamber ( 5 ) via power lines ( 16a . 16b . 16c . 16d . 16e . 16f ) with the power supply device ( 11 ) are electrically connected. Apparatus according to claim 1, characterized in that the hollow cylinder ( 13a . 13b . 13c . 13d . 13e . 13f ) are formed from graphite. Device according to claim 1 or 3, characterized in that at least three hollow cylinders ( 13a . 13b . 13c . 13d . 13e . 13f ) are provided. Device according to one of claims 1 to 4, characterized in that one of the coil turns ( 9 ) enclosed surface has any geometric shape. Device according to claim 1, characterized in that the heating device ( 1 ) Stabilizing elements ( 3a . 3b . 3c ) on the coil turns ( 9 ) having. Device according to claim 6, characterized in that the stabilizing elements ( 3a . 3b . 3c ) as cylindrical rods with at least one groove-shaped notch ( 12 ) are configured. Device according to claim 6 or 7, characterized in that the stabilizing elements ( 3a . 3b . 3c ) as cylindrical rods with at least two platelets ( 10 ) are configured. Apparatus according to claim 6 to 8, characterized in that the stabilizing elements ( 3a . 3b . 3c ) are arranged coaxially along the coil outer side, wherein the groove-shaped notches ( 14 ) in the coil turns ( 9 ) of the coils ( 1a . 1b . 1c ) or the tiles ( 10 ) between the coil turns ( 9 ) lie. Device according to one of claims 6 to 9, characterized in that at least two stabilizing elements ( 3a . 3b . 3c ) available. Device according to one of claims 1 to 10, characterized in that the coil turns ( 9 ) are configured spiral or stepped. Device according to one of claims 1 to 11, characterized in that a winding cross-section (Q) of the coil turns ( 9 ) has any geometric shape.