Patent Application
20130295513
This disclosure generally relates to directional solidification furnaces and, more specifically, to susceptors for directional solidification furnaces.
Directional solidification furnaces are used to produce multi-crystalline silicon ingots. During use of the furnace, raw silicon is first placed into a crucible disposed in the furnace. The raw silicon can take the form of solid chunks, recycled polysilicon, silicon dust, or a combination thereof. The crucible is typically constructed of quartz or another suitable material that can withstand high temperatures. The crucible is a five-sided box, with a lid placed over an open top of the box. The crucible is supported by a susceptor that adds structural support and rigidity to the crucible. The susceptor usually comprises four vertical walls connected by fastening systems (e.g., nuts and bolts) and positioned atop a bottom.
The crucible and susceptor are disposed within a containment vessel that forms part of the furnace. The containment vessel seals the crucible from the outside ambient environment. The crucible and the charge are then heated to a temperature sufficient to melt the silicon. After the charge has completely melted, it is cooled at a controlled rate to achieve a directional solidification structure within the resulting ingot.
A concern in the production of multi-crystalline ingots is the strength and ease of assembly and disassembly of the susceptor. The fastening systems used in known susceptors to connect the vertical walls to each other may lack sufficient strength to prevent the walls from separating during a failure of the integrity of the crucible. Moreover, the known fastening systems are often difficult to assemble and do not permit ready disassembly of the walls of the susceptor.
This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
One aspect of the present disclosure is a susceptor for supporting a crucible in a directional solidification furnace used to melt a semiconductor material. The susceptor includes four walls and each wall has a vertical edge. An interlocking member is on each edge. The interlocking member of one wall is interlocked with the interlocking member of an adjacent wall at a corner of the susceptor. Openings are disposed through the interlocking members. The openings in the interlocking member of one wall are coaxial with the openings in the interlocking member of the adjacent wall. At least four rods are provided and each rod is disposed in the openings of the interlocking members of one of the corners of the susceptor.
Another aspect of the present disclosure is a susceptor for supporting a crucible in a furnace. The susceptor includes a first wall having a vertical edge and a second wall having a vertical edge. A first interlocking member is on the vertical edge of the first wall and a second interlocking member is on the vertical edge of the second wall. The first interlocking member is interlocked with the second interlocking member when the first wall and second wall are in an assembled configuration. Openings are disposed through the first interlocking member and the second interlocking member. Each of the openings through the first interlocking member is coaxial with each of the openings through the second interlocking member.
Yet another aspect of the present disclosure is a susceptor for supporting a crucible in a directional solidification furnace used to melt a semiconductor material. The susceptor includes a first wall having a vertical edge and an interior surface and a second wall having a vertical edge and an interior surface. When in an assembled configuration, the vertical edge of the first wall is positioned adjacent a portion of the interior surface of the second wall. A separator is positioned between the vertical edge of the first wall and the portion of the interior surface of the second wall. The separator prevents contact between the vertical edge of the first and the portion of the interior surface of the second wall when the walls are in the assembled configuration.
Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.
Like reference symbols in the various drawings indicate like elements.
The embodiments described herein generally relate to susceptors for supporting a crucible in a directional solidification furnace. An example furnace is shown schematically in
The example directional solidification furnace 50 comprises a quartz crucible 12 supported by a crucible support 13 (i.e., a susceptor), including walls 14 and a crucible base 16. Together with a lid 22, the crucible 12, walls 14 and crucible base 16 form a crucible assembly or an inner assembly 15. This inner assembly 15 may also include a heat exchanger 17 disposed beneath the crucible base 16. A lid 22 is positioned atop the crucible 12.
Heaters 18 are suitably positioned around the walls 14 and within a containment vessel 20. The heaters 18 may also be disposed above the crucible 12, and the heaters may suitably be radiant heaters. The heaters 18 apply the heat necessary to melt charge material within the crucible 12. The charge material of this embodiment is silicon, though other materials are contemplated. Side insulation 19 is disposed around the crucible 12 and may be partially opened, such as by vertical movement (shown by arrows in
Referring now to
The susceptor 100 has four vertical walls 106 (two of which are shown in the view of
An interlocking member (generally referred to as 120 and shown in
Each of the interlocking members 120 comprises tenons 122 and mortises 124 positioned between the tenons. As shown, the number of mortises 124 in the interlocking member 120 of one wall 106 is equal to the number of tenons 122 of the interlocking member of the adjacent wall. That is, the interlocking members 120 disposed on the vertical edges 108 of adjacent walls 106 have equal numbers of mortises 124 and tenons 122. In other embodiments, different types of interlocking members 120 may be used other than or in addition to the interlocking members to interlock the walls 106 of the susceptor 100, such as dovetail grooves.
As shown in
The tenons 122 of the interlocking members 120 have a thickness T and the mortises 124 have a depth D. In this embodiment, the depth D of the mortises 124 is equal to the thickness T of the tenons 122. However, in other embodiments the thickness T and depth D may differ by some amount.
In this embodiment, openings 130 are disposed through the interlocking members 120, as best shown in
Rods 140 (one of which is shown in
The rods 140 have a diameter Dr that is less than a diameter Do of the openings 130 such that the rods may pass through the openings. In one embodiment, the diameter Dr is about 7.5 mm, and the diameter Do is about 9.0 mm, so that Dr is about 1.5 mm less than the diameter Do. The rods 140 may be secured in their position shown in
In operation, the susceptor 100 is assembled by positioning walls 106 adjacent each other such that the tenons 122 of one interlocking member 120 are positioned within the mortises 124 of the interlocking member of the adjacent wall, and vice versa. The rod 140 is then inserted through the openings 130 to secure the walls 106 in the interlocked configuration. A fastening system may be used to secure the rod 140. The process is then repeated for each of the walls 106 in the susceptor 100 until all of the walls are interlocked with their respective adjacent walls.
The susceptor 100 of the embodiment of
As shown in
The separator 218 prevents or inhibits contact between the vertical edge 204 of the first wall 210 and the portion 212 of the interior surface 206 of the second wall 214 when the walls are in the assembled configuration. Thus the separator 218 prevents the vertical edge 204 of the first wall 210 from bonding to the portion 212 of the interior surface 206 of the second wall 214, e.g., during operation of the susceptor 200.
The separator 218 may be made of any suitable material, such as a fabric made of compressed fibers. One example of such a fabric is felt.
In prior systems lacking a separator, the contact between the walls or portions thereof (e.g., the vertical edge and portion of the interior surface) may have resulted in the two becoming bonded together when the susceptor was subject to elevated temperatures during use of the furnace. Such bonding made disassembly of the susceptor difficult, if not impossible.
While the invention has been described in terms of various specific embodiments, it will be recognized that the invention can be practiced with modification within the spirit and scope of the claims.
When introducing elements of the present disclosure or the embodiments thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., “top”, “bottom”, “side”, etc.) is for convenience of description and does not require any particular orientation of the item described.
As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
