HK1117575A - Method and device for producing oriented solidified blocks made of semi-conductor material - Google Patents

Description

Method and device for producing directionally solidified blocks from semiconductor material

Technical Field

The invention relates to a method for producing directionally solidified blocks from semiconductor material, wherein a melt contained in a crucible is heated at least from above in a process chamber for directionally solidifying, while making full use of the crystallization.

The invention further relates to a device for producing directionally solidified blocks from semiconductor material, comprising a crucible in which the melt is contained, and a heat shield surrounding the crucible at least from above and from the sides, the heat shield being spaced apart from the crucible at least above the crucible, and comprising at least one heating device arranged above the crucible.

Background

In the methods and devices according to the prior art for producing directionally solidified blocks of semiconductor material, in particular for directionally solidified silicon, the melt contained in the crucible is heated either from the side or from the bottom. The advantage of heating from above is that a good horizontal energy distribution can be achieved, resulting in a desired horizontal phase boundary upon solidification. However, the disadvantage is that the heating element is directly in the vapor stream of the semiconductor material which remains in the liquid state during solidification and therefore reacts with the semiconductor material, for example silicon. In the case of the graphite heating elements which are customary in accordance with the prior art, this leads to rapid aging and also to a change in the electrical resistance with corresponding consequences.

Disclosure of Invention

The object of the invention is to provide a method and a device for producing directionally solidified masses, i.e. a device for carrying out a crystallization process, in particular to avoid the heating element from being aged by the influence of metal vapors, and furthermore to provide the possibility of heating the melt unambiguously and reproducibly.

This object is achieved by a method for producing directionally solidified blocks from semiconductor material, in which a melt contained in a crucible is directionally solidified in a process chamber and is heated at least from above with full use of the crystallization, characterized in that the heating of the crucible is effected indirectly from above via an upper heating chamber which is separated from the process chamber.

In terms of apparatus, this object is achieved by an apparatus for producing directionally solidified masses from semiconductor material, having a crucible in which the melt is held and having a thermal insulation surrounding the crucible at least from above and from the sides, which thermal insulation is at a distance from the crucible at least above the crucible, and having at least one heating device arranged above the crucible, characterized in that the region of the interior of the thermal insulation above the crucible is divided by a partition into a process chamber and an upper heating chamber above it, in which heating chamber at least one heating element is arranged.

The method and the device are characterized in that no direct contact occurs between the metal vapor discharged from the metal melt and the heating element.

The method is preferably carried out in such a way that the crucible is passed at least from above through the upper heating chamber and the process chamber for directional solidification and is heated with full use of the crystallization, without the upper heating element being damaged.

In particular, in combination with the device according to the invention, the method is carried out in that the upper heating device is separated in a gas-tight manner by a partition above the crucible, i.e. above the melt, so that the metal vapors, for example silicon vapors, rising from the heated melt are kept away from the active heating element.

According to a preferred measure, the gas formed above the melt in the process chamber is removed in such a way that it does not enter the heating chamber.

In addition, to achieve the desired aim, the spacers are preferably placed on the frame; such a frame surrounds the crucible laterally at a distance. Such a frame should be made of insulating material and form an intermediate insulating wall in connection with the external insulation, i.e. the external insulation surrounds the intermediate insulating wall forming the gap at a distance.

The crucible is supported on a support plate which, in a further embodiment of the device, has a bead as a base part on its edge region; the support plate is substantially hermetically sealed with respect to the intermediate heat insulating body by means of this crimping of the base plate.

The entire crucible is placed in a vacuum chamber using an insulator.

The frame, which laterally surrounds the base plate of the crucible support plate, simultaneously forms the receiving trough or a part of the receiving trough for the melt which may flow out of the crucible. For such a receiving channel, the frame, which laterally surrounds the crucible, may constitute the side walls of the receiving channel. Further, the bottom of the receiving groove may be constituted by a crucible supporting plate fitted into the bottom plate.

The base plate is preferably composed of graphite or a combination of graphite plates and/or graphite films. Advantageously, the side walls of the receiving groove consist of silicon-absorbing graphite felt.

The base plate has an opening or a perforation as a heat-conducting window in the projection of the geometrically horizontal melt level.

In order to prevent the melt or the melt vapors from escaping from the interior of the device, the gap should be formed as a labyrinth step, through which silicon can flow out or escape.

The support structure on which the crucible or the support plate supporting the crucible is supported can at the same time be provided as a gas supply channel. For this purpose, at least one support beam is preferably provided, which has gas discharge openings, for example nozzle openings, on its surface facing the bottom of the crucible, through which cooling gas can be supplied to the bottom of the crucible floor or support plate. The heated cooling gas is preferably recirculated in a circuit through a heat exchanger, cooled and pumped back to the support beam.

Below the crucible bottom, specifically below the support beam, a lower active heating element and a cooling plate with cooling coils located therebelow are arranged at a distance, so that the crucible can be heated and cooled efficiently from below, in particular under the interaction of the chamber with the heating element arranged in the upper heating chamber.

Finally, side vents are provided which can pass through the outer insulator side walls and the intermediate insulator.

Drawings

Further details and features of the invention emerge from the following description of an embodiment of the invention with the aid of the sole figure, which shows a device according to the invention in a schematic sectional view.

Detailed Description

The apparatus shown in the drawing is used for producing directionally solidified blocks from semiconductor material, in particular directionally solidified blocks of silicon melt. The apparatus has a crucible 1 which is surrounded from above and from the side by an external thermal insulation 2. The external insulator 2 is spaced apart from the side wall and the upper face of the crucible 1.

The crucible 1 and the external thermal insulation 2 are arranged in a vacuum chamber 3 and are held therein by a support beam 4, which is described in more detail below.

The crucible 1 is filled with a partition 5 which divides the space above the crucible 1 into a process chamber 6 and an upper heating chamber 7. An active heating element 8 is arranged horizontally distributed in the upper heating chamber 7 between the partition 5 and the upper covering of the insulation 2. The intermediate heat-insulating body 10, which forms a frame and is arranged at a distance from the side wall of the crucible 1 on the one hand and the external heat-insulating body 2 on the other hand, forms a gap between the partition walls 5 and the external heat-insulating body.

The upper heating chamber 7 is substantially hermetically closed with respect to the process chamber 6 by means of a partition 5.

The crucible 1 is supported on a support plate 9 which at the same time forms the bottom surface of the external thermal insulation 2. As can be seen from the figures, the support plate 9 is enclosed in a so-called base plate 11, which substantially hermetically seals the support plate 9 in its edge region with respect to the intermediate heat insulation body 10.

In the upper region of the device, a tubular blowing duct 12 is provided which passes through the partition 5 and the upper cover of the external thermal insulation 2 and ends with its other end in the interior of the vacuum chamber 3.

The above-mentioned intermediate heat insulator 10 is used in combination with the bottom plate 11 and the crucible supporting plate 9 as a receiving groove for the melt that may flow out of the crucible 1. The base plate 11 can consist of graphite or of a combination of graphite plates and/or graphite films, for example, coated in a suitable manner. The side walls of the receiving channel, i.e. the intermediate heat insulating body 10 in this embodiment, may be made of silicon-absorbent graphite felt.

Although not visible in the sectional view of the drawing, the base plate 11 has a perforation, which is designated by the reference numeral 13, as a heat-conducting window in the projection of the geometrically horizontal melt level.

It should be noted that all gaps through which silicon or molten metal in the crucible 1 can flow out are constructed as labyrinth steps, and that the gaps are successively filled with molten metal as it flows out of the bath, the molten metal gradually solidifying by the released heat and then reliably closing the gaps.

The support beam 4 is tubular and is used as a gas transmission channel; for this purpose, a tubular end 14 leads to the outside through the wall of the vacuum chamber 3 on the right in the figure and is connected to a gas feed line 15. On the side of the support beam 4 facing the crucible bottom, there are nozzle openings 16 through which the cooling gas above the tubular support beam 4 can flow onto the bottom side of the support plate 4 and thus onto the floor of the crucible 1. The cooling gas flows back in circulation from a cooling gas discharge 17 in the direction of the flow arrow 18 through a heat exchanger 19 and a cooling gas circulation pump 20.

A lower active heating 21 is arranged below and at a distance from the support beam 4. Located below the heating elements 21 is a cooling plate 22, the cooling plate 22 having cooling coils 23 arranged on the underside, which coils, with the supply of a corresponding coolant, can effectively cool the lower region of the arrangement.

Through the upper heating element 8, the lower heating element 23, the gas supply channel above the support beam 4 and the lower cooling plate 22, a directional solidification of the melt can be achieved by corresponding heating and cooling.

In order to exhaust the process chamber 6 effectively, an exhaust opening 24 is provided in the lower region between the wall of the crucible 1 and the intermediate heat insulator 10, which opening into the outer space delimited by the vacuum chamber 3.

Claims (28)

1. Method for producing directionally solidified blocks from semiconductor material, in which a melt contained in a crucible is heated at least from above in a process chamber for the directional solidification while making full use of the crystallization, characterized in that the heating of the crucible is carried out indirectly from above via an upper heating chamber which is separated from the process chamber.

2. The method of claim 1, wherein the upper heating chamber and the process chamber for directional solidification are heated at least from above while making full use of the crystallization.

3. Device for producing directionally solidified masses from semiconductor material, comprising a crucible containing a melt and an insulating body surrounding the crucible at least from above and from the sides, which insulating body is at a distance from the crucible at least above the crucible, and comprising at least one heating device arranged above the crucible, characterized in that the region of the interior of the insulating body (2) above the crucible (1) is divided by a partition (5) into a process chamber (6) and an upper heating chamber (7) located above it, in which at least one heating element (8) is arranged.

4. The device according to claim 3, wherein the upper heating chamber (7) is substantially hermetically sealed from the process chamber (6) by means of a partition (5).

5. The device according to claim 3 or 4, wherein the crucible (1) is supported on a support plate (9).

6. The device as claimed in one of claims 3 to 5, wherein the partition (5) is located on a frame (10), the frame (10) surrounding the crucible (1) at a distance from the side.

7. The device according to claim 6, wherein the frame is formed of an insulating material forming the intermediate insulating wall (10).

8. Device according to one of claims 3 to 7, wherein the frame (10) is arranged at a distance from the heat insulation (2) forming the interspace.

9. The device as claimed in claim 5, wherein the crucible support plate (9) is enclosed in a base plate (11).

10. The device according to claim 9, wherein the base plate (11) is made of graphite.

11. The device according to claim 9, wherein the base plate (11) is formed by a combination of graphite plates and/or graphite films.

12. The device according to claim 9, wherein the edge region of the base plate (11) seals the carrier plate (9) substantially in a gas-tight manner with respect to the frame (10).

13. The device as claimed in one of claims 3 to 12, wherein a blow-off feed channel (12) leads out of the upper region of the process chamber (6).

14. The device as claimed in claim 13, wherein the blowing air supply duct (12) passes through the partition (5).

15. The apparatus as claimed in one of claims 3 to 14, wherein the crucible (1) is arranged in the vacuum chamber (3) by means of a thermal insulation.

16. The device as claimed in claims 14 and 15, wherein the blow-off feed duct (12) connects the process chamber (6) directly to the vacuum chamber (3).

17. The device as claimed in claim 6 and claim 9, wherein the frame (10) together with the base plate (11) and the crucible support plate (9) can be simultaneously provided as a receiving trough for the outflow of the melt.

18. The device of claim 17, wherein the side walls of the receiving groove are formed by a frame (10).

19. The device as claimed in claim 17, wherein the bottom of the receiving groove is formed by a crucible support plate (9) which is inserted into the bottom plate (11).

20. The apparatus of claim 18 wherein the sidewalls of the receiving slots are comprised of silicon-imbibed graphite felt.

21. The device as claimed in claim 9, wherein the base plate (11) has perforations as heat-conducting windows in the projection of the geometrically horizontal melt level (13).

22. Apparatus according to any one of claims 3 to 21, wherein the slot is provided as a labyrinth step through which silicon can be expelled.

23. The device according to any one of claims 5 to 22, wherein the support plate (9) is supported by at least one support beam (4).

24. The device according to claim 23, wherein the support beam (4) is simultaneously provided as a gas duct (14, 16).

25. The device as claimed in claim 24, wherein the support beam (4) is provided on its side facing the crucible bottom with nozzle openings (16) through which the cooling gas is directed through the support beam (4) provided as a gas supply channel to the crucible bottom or to the bottom of the crucible support plate.

26. The device according to claim 25, wherein the cooling gas is re-cooled in a circulation by means of a heat exchanger (19) and is conveyed to the support beam (4) by means of a pump (20).

27. Apparatus according to one of claims 3 to 26, wherein a lower active heating element (21) is arranged at a distance below the support plate (9) of the crucible (1).

28. An apparatus as claimed in claim 27, wherein cooling means (22, 23) are arranged below the heating element (21).