CA1116985A - Capillary die - Google Patents
Capillary dieInfo
- Publication number
- CA1116985A CA1116985A CA000322467A CA322467A CA1116985A CA 1116985 A CA1116985 A CA 1116985A CA 000322467 A CA000322467 A CA 000322467A CA 322467 A CA322467 A CA 322467A CA 1116985 A CA1116985 A CA 1116985A
- Authority
- CA
- Canada
- Prior art keywords
- die
- die member
- top end
- grooves
- melt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/34—Edge-defined film-fed crystal-growth using dies or slits
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The apparatus is an improved apparatus for use in a system for growing crystalline bodies from the melt. The apparatus has a novel capillary die in which the die capillaries are defined by one or more slots or grooves formed in a side wall surface of the die.
The apparatus is an improved apparatus for use in a system for growing crystalline bodies from the melt. The apparatus has a novel capillary die in which the die capillaries are defined by one or more slots or grooves formed in a side wall surface of the die.
Description
( ~16~
This invention relates to apparatus for growing crystalline bodies from the melt and more particularly to novel capillary dies for growing crystalline bodies from the melt according to the EFG Process.
Various systems have been developed for growing crystalline bodies from the melt. The present invention pertains to an im-provement in growing crystalline bodies from a melt according to what is called the edge-defined, film-fed, growth technique (also commonly known as the EFG Process). Details of the EFG
Process are descr bed in U.S. Letters Patent No. 3,591,348 issued July 6, 1971, to Harold E. LaBelle, Jr., for Method of Growing Crystalline Materials, and U.S. Letters Patent No.
3,6~7,633, issued August 29, 1972, to Harold E. LaBelle, Jr., et al for Apparatus for Growing Crystalline Bodies from the Melt.
In the EFG Process the shape of the crystalline body is determined by the external or edge configuration of the end of a capillary forming member which for want of a better name is called a die. This process involves growth on a seed crystal from a liquid film of feed material sandwiched between the growing body and the end surface of the die, with the liquid in the film being continuously replenished from a suitable melt reservoir via one or more capillaries in the die member. Among the materials that have been grown by the EFG Process as monocrystalline bodies are alpha-alumina (sapphire), spinel, chrysoberyl, barium titanate, lithium niobate, yttrium aluminum garnet and silicon.
j ~ 69~}S
Essential requirements of the EFG Process are that the ¦crucible and die member be made of a composition that will with-¦stand the operating temperatures and will not react with the melt.
¦A1SO~ the die member must be wettable by the melt, and the die ¦member and the crucible both should be made of a r~aterial that ¦will not dissolve in the melt. By way of example, dies and cru-¦cibles conventionally used in growing monocrystalline alumina ¦bodies generally are made of molybdenum or tungsten, while in ¦growing monocrystalline silicon bodies from the melt, the dies ¦generally are made of graphite and the crucibles generally are ~made of graphite or quartz.
¦ An advantage of the EFG Process is that bodies of selected ¦shapes such as flat ribbon or round tubes can be produced ¦commencing with the simplest of seed geometries, namely, a ¦ round small diameter speed crystal. A typical prior art EFG
I .~ " ..
system comprises a crucible-die assembly in which a die member is disposed in the interior of the crucible in contact with the melt.
The die member includes a shape defining top end surface of a l configuration corresponding to that desired for the crystal ¦ to be grown. Melt is supplied t:o the die top end surface by ¦one or more die capillaries. The latter may comprise one ¦or more vertical elongate passageways of capillary dimension ¦between the top end surface of the die member and die bottom end.
¦Another form of prior art die consists of two concentric cylin-¦drical sleeves which are spaced from one another and held in con-centri~ rel tion by suitable ~ ns as~ ior exarple~ by a plurality Il ( l~ C,~
of spacers in the form of small diameter wires or rods of capil-lary dimension, e.g. in the manner shown in Fig. 2 of U.S. Letterc Patent No. 3687633, issued August 29, 1972 to Harold E. LaBelle, ~r. and Charles J. Cronan. Further details of these and other conventional EFG dies are given in U.S. Letters Patent No.
3687633. Ideal growth conditions call for all areas of the die top end surface to be at the same temperature. However, in a conventional capillary die interior areas of the die top end surface may be 20C or more higher in temperature than the outside edges of the die top end surface. Two factors are at work:- (1) the capillaries normally terminate in the interior areas of the die top end surface and therefore it is these interior areas which are being continually heated by fresh melt, and (2) the die outer edges are susceptible to increased cooling by radiation. These temperature differences can cause difficulties during seeding. For example, if a seed crystal is brought into engagement with the die adjacent the die top end outer edge, the temperature of the die at this point may not be high enough to melt the seed. On the other hand, increasiny the temperature of the melt so as to raise the tempera-ture of the die top outer edges sufficiently to melt the seed may result in a temperature adjacent the die top end central regions which is too high for proper growth conditions.
Moreover, in the case of growinq silicon from a graphite die, the relatively cooler die outer edges may permit silicon carbide particles to precipitate out during growth.
Should this occur the die may flood and crystal growth will thus be interrupted.
The primary object of the present invention is thus to provide an improved apparatus for growing crystalline bodies from the melt.
Another object is to provide a novel capillary die for growing crystalline bodies from the melt by the EEG
Process whereby the aforesaid problems of die seedina and/or die flooding may be reduced.
Described briefly, the present invention consists of an apparatus for use in a system for growing crystalline bodies of selected shape from a melt wherein the melt is derived from a crucible by a capillary die member, and the crystalline body is grown from a liquid/solid growth inter-face at the top end of the capillary die member, the apparatus comprising an improved capillary die member having a top end, a bottom end, at least one exterior side wall surface of the capillary die member extending between the top and bottom ends, and a plurality of capillaries in the form of a plurality of grooves of capillary dimension formed in the exterior side wall surface of the die member, the grooves terminating at select locations along the top end of the die member so that melt can be drawn from the crucible to the top end via the groovefi as the crystalline body is grown from the liquid/solid growth interface at the top end of the die member.
rw/ - 5 -( 111~
Other features and many of the attendant advantages of this invention are set forth or rendered obvious by the following detailed description which is to be taken together with the accompanying drawings wherein like numerals depict like parts, and wherein:
Fig. 1 is a sectional view in elevation, of a crystal growing apparatus with certain parts represented schematically, and illustrating a preferred form of capillary die in accordance with the present invention;
Fig. 2 is an end view of the die of Fig. l;
Fig. 3 is a top plan view, on a greatly enlarged scale of the die of Fig. l;
Fig. 4 is a top plan view, on a greatly enlarged scale, showing a second form of die in accordance with the present invention; and Fig. 5 is a top plan~view, on a greatly enlarged scale, showing a third form of die in accordance with the present invention.
Capillary dies may be made in accordance with the present invention for use in producing monocrystalline bodies of a variety of shapes. However, the invention is particularly dapted for forming dies for producing relatively thin, wide flat silicon ribbons by the EFG Process, and the following escription is directed to this preferred embodiment of this invention. ~lowever, one skilled in the art will know the appro-priate selection of materials which will permit the die and cruci-ble combinations described in the following description to be used :` ( 1~6~1~5 to grow crystalline bodies of other congruently melting materials that solidiEy in identifiable crystal lattices.
The invention is also applicable to growth of other materials such as eutectic compositions.
Figs. 1-3 show a preferred form of capillary die for growing silicon ribbon in accordance with the present invention.
The illustrated capillary die comprises a solid graphite block 20 including a generally rectangular horizontal bottom surface 22, a pair of vertically oriented parallel end surfaces 24 and 26, op-positely inclined side surfaces 28 and 30 and a die top surface 32 Die top surface ~2 is of a size and shape corresponding substan-tially to the cross-section of ribbon to be grown. For example, for growing ribbon approximately 3 inches wide and 0.005 inches thick the die top surface 32 should measure 3 inches by 0.005 inches.
As seen particularly in Fig. 2 block 20 is tapered so that the die bottom surface 22 is larger in plan than the die top surface 32. Tapering the die in this manner is preferred since it provides a die which has greater structural stability and reduces the likelihood of accldentally in,juring the top surface during formation of the capillaries hereinafter described. This consideration is particularly improtant in the case of dies which are designed for,growing especially thin crystals, e.g. 0.005 inch thick silicon ribbons. Tapering the die in this manner also has the advantage of permitting the die capillaries to draw melt from a greater area of melt as will become clear from the description following.
. _._ 11 Il , 1~6~5 An unique f eature and particular advantage of the present invention is the manner in which the die capillaries are formed Referring in particular to Figs. l and 3, the die capillaries comprise a plurality of shallow grooves or slots 36 formed in the die side surfaces 28 and 30. Each slot 36 is of suitable size and shape for acting as a capillary. For example, the slots 36 illustrated in the Figs. 1-3 embodiment of the invention are generally triangular in cross section, have an apex angle of about 60 and an apex depth of approximately l/64 inch. Such slots are suitable for functioning as a capillar ies for molten silicon. It will be understood, however, that the capillary slots may have other shapes and sizes. For example the capillary slots may comprise elongate grooves having a semi-circular cross-section of suitable dimension as shown at 36A
in Fig. 4, or the capillary slots may comprise elongate grooves having a substantially square cross-section of suitable dimension as shown at 36B in Fig. 5. For ease of manufacture the capil-lary slots preferably will have a depth which does not exceed twice their width. As seen in the drawings the capillary slots 36, 36A, 36B extend to and intersect the die top surface 32. Slots 36, 36A, 36B preferably but need not extend to and intersect the die bottom surface 22.
Although not required, it is also preferred to include a blind hole or well 40 in the die top end surface 32. Well 40 should be of sufficient size to provide a space for collection of melt, i.e. so as to provide a thermal reservoir whereby to convey heat the center of the die. One skilled in the art will also recognize that well 40 will also facilitate distribu-on of t.he melt widthwise o: the die top wa1l 32 during seeding.
1~16~8~;
The die block 20 is disposed within a quartz or graphite crucible 42. The latter is of conventional design and may includ~
for example a bottom wall 44, and a cylindrical side wall 46, which together define an interior space for containing a melt 48 of the material to be grown, i.e. silicon. As seen in Fig. 1 the die block 20 is positioned in the melt 48 so that the die bottom surface 22 including the lower ends of the capillaries 36 are disposed below the surface of the melt 48, while the die top surface 32 is above the surface of the melt. The die block 20 is retained in fixed position relative to the crucible 42 by means of suitable mounting pins 50 which extend through openings in the die block and are received in suitable openings in wall 46 of crucible 42. Alternatively the pins may be located so that they rest on the upper end surface of crucible wall 46. The die and crucible are mounted in a suitable crystal growing furnace, e.g.
a furnace of the type shown in Fig. 1 of U.S. Letters Patent No. 3,591,348 supra.
One skilled in the art will recognize that the capillary die arrangement of the present invention oEfers a number of advantages over prior art capillary dies. Fox one thing, the die may be formed in a single piece. Another advantage of the present invention derives from the fact that the die capillaries are for~ed in the outer surfaces of the die. As a result the outer edges of the die top surface are substantially at the temp-erature of the melt, thereby facilitating seeding. Moreover, the possibility of formation and accrual of silicon carbide particles in the capillaries and/or at the die upper surface is reduced.
~ 5 Furthermore, the capillaries can be made with great precision by simple machining techniques, e.g. by means of a cutting wheel or saw. This is advantageous in the case of brittle materials like graphite since there is less likelihood of S damaging the die material during formation of the capillaries.
It also is advantageious in the case of very hard die materials such as molybdenum (which is used in growing sapphire) since it is far easier to form an external groove than an internal bore of capillary size. Another advantage of the present invention is the ability to better control the temperature across the die top surface. In this-regard one skilled in the art will recognize that with a sufficient number of capillary grooves relatively closely spaced to one another, the die top surface can be rendered essentially isothermal.
The foLlowing example illustrates a preferred mode of practicing the invention~
EXAMPLE
The crucible and die arrangement shown in Figs. 1-3 is produced as follows:
A solid graphite die block 20 is formed having a rectang-ular, bottom surface 22 of dimension 0.250 by 3.0 inches, slanted rectangular side surfaces 28 and 30 of dimension 2.75 by 3.0 inches, and a top surface 32 of dimension 3 inches by 0.005 inches. This die is disposed in a 3.08 inch diameter graphite crucible 42. The die block is held in position in the crucible by graphite pins 50. The side surfaces 28 and 30 of block 20 are grooved as shown in Fig. 1 by vee-shaped grooves 36 each having an apex angle of about 60. Grooves 36 are substan-tailly parallel,to one another and are spaced, apex-to-apex, approximately 0.120 inches apart. Grooves 36 extend I
. . .
~ 16~85 between the die block bottom and top walls ~2 and 32, respectively .
The crucible is charged with substantially pure silicon and a sub-stantially monocrystalline silicon ribbon is grown according to the EFG method by drawing the ribbon from a film of melt which extends across the top wall 32 of the die and communicates with th e melt in grooves 36. The molten silicon in the crucible is main-tained at a temperature of about 40C above its melting point, while the die top surface is held at about 10C above the same melting point. Once growth has commenced, the pulling speed is held at about 3 inches per m~nute. Growth continues until substantially all the silicon within the crucible 42 is consumed.
Various changes may be made in the invention as will be obvious to one skilled in the art. For example, the die may be formed from two or more pieces which are joined together by suitable means. Capillaries also may be formed in the end ., ................. ", .
surfaces 2~ and 26 in those cases where the upper ends of side surfaces 28 and 30 are apart far enough. Moreover, the dies may be produced in a variety of shapes and sizes. Thus the die member may be made with six slanted sides so that its upper end surface is hexagonal, whereby to permit growth of hexagonal rods as is advantageous in manufacturing silicon solar cells. Each or only some of the six inclined side surfaces could have capilla~ Y
slots as above described. Still other changes will be obvious to one skilled in the art.
This invention relates to apparatus for growing crystalline bodies from the melt and more particularly to novel capillary dies for growing crystalline bodies from the melt according to the EFG Process.
Various systems have been developed for growing crystalline bodies from the melt. The present invention pertains to an im-provement in growing crystalline bodies from a melt according to what is called the edge-defined, film-fed, growth technique (also commonly known as the EFG Process). Details of the EFG
Process are descr bed in U.S. Letters Patent No. 3,591,348 issued July 6, 1971, to Harold E. LaBelle, Jr., for Method of Growing Crystalline Materials, and U.S. Letters Patent No.
3,6~7,633, issued August 29, 1972, to Harold E. LaBelle, Jr., et al for Apparatus for Growing Crystalline Bodies from the Melt.
In the EFG Process the shape of the crystalline body is determined by the external or edge configuration of the end of a capillary forming member which for want of a better name is called a die. This process involves growth on a seed crystal from a liquid film of feed material sandwiched between the growing body and the end surface of the die, with the liquid in the film being continuously replenished from a suitable melt reservoir via one or more capillaries in the die member. Among the materials that have been grown by the EFG Process as monocrystalline bodies are alpha-alumina (sapphire), spinel, chrysoberyl, barium titanate, lithium niobate, yttrium aluminum garnet and silicon.
j ~ 69~}S
Essential requirements of the EFG Process are that the ¦crucible and die member be made of a composition that will with-¦stand the operating temperatures and will not react with the melt.
¦A1SO~ the die member must be wettable by the melt, and the die ¦member and the crucible both should be made of a r~aterial that ¦will not dissolve in the melt. By way of example, dies and cru-¦cibles conventionally used in growing monocrystalline alumina ¦bodies generally are made of molybdenum or tungsten, while in ¦growing monocrystalline silicon bodies from the melt, the dies ¦generally are made of graphite and the crucibles generally are ~made of graphite or quartz.
¦ An advantage of the EFG Process is that bodies of selected ¦shapes such as flat ribbon or round tubes can be produced ¦commencing with the simplest of seed geometries, namely, a ¦ round small diameter speed crystal. A typical prior art EFG
I .~ " ..
system comprises a crucible-die assembly in which a die member is disposed in the interior of the crucible in contact with the melt.
The die member includes a shape defining top end surface of a l configuration corresponding to that desired for the crystal ¦ to be grown. Melt is supplied t:o the die top end surface by ¦one or more die capillaries. The latter may comprise one ¦or more vertical elongate passageways of capillary dimension ¦between the top end surface of the die member and die bottom end.
¦Another form of prior art die consists of two concentric cylin-¦drical sleeves which are spaced from one another and held in con-centri~ rel tion by suitable ~ ns as~ ior exarple~ by a plurality Il ( l~ C,~
of spacers in the form of small diameter wires or rods of capil-lary dimension, e.g. in the manner shown in Fig. 2 of U.S. Letterc Patent No. 3687633, issued August 29, 1972 to Harold E. LaBelle, ~r. and Charles J. Cronan. Further details of these and other conventional EFG dies are given in U.S. Letters Patent No.
3687633. Ideal growth conditions call for all areas of the die top end surface to be at the same temperature. However, in a conventional capillary die interior areas of the die top end surface may be 20C or more higher in temperature than the outside edges of the die top end surface. Two factors are at work:- (1) the capillaries normally terminate in the interior areas of the die top end surface and therefore it is these interior areas which are being continually heated by fresh melt, and (2) the die outer edges are susceptible to increased cooling by radiation. These temperature differences can cause difficulties during seeding. For example, if a seed crystal is brought into engagement with the die adjacent the die top end outer edge, the temperature of the die at this point may not be high enough to melt the seed. On the other hand, increasiny the temperature of the melt so as to raise the tempera-ture of the die top outer edges sufficiently to melt the seed may result in a temperature adjacent the die top end central regions which is too high for proper growth conditions.
Moreover, in the case of growinq silicon from a graphite die, the relatively cooler die outer edges may permit silicon carbide particles to precipitate out during growth.
Should this occur the die may flood and crystal growth will thus be interrupted.
The primary object of the present invention is thus to provide an improved apparatus for growing crystalline bodies from the melt.
Another object is to provide a novel capillary die for growing crystalline bodies from the melt by the EEG
Process whereby the aforesaid problems of die seedina and/or die flooding may be reduced.
Described briefly, the present invention consists of an apparatus for use in a system for growing crystalline bodies of selected shape from a melt wherein the melt is derived from a crucible by a capillary die member, and the crystalline body is grown from a liquid/solid growth inter-face at the top end of the capillary die member, the apparatus comprising an improved capillary die member having a top end, a bottom end, at least one exterior side wall surface of the capillary die member extending between the top and bottom ends, and a plurality of capillaries in the form of a plurality of grooves of capillary dimension formed in the exterior side wall surface of the die member, the grooves terminating at select locations along the top end of the die member so that melt can be drawn from the crucible to the top end via the groovefi as the crystalline body is grown from the liquid/solid growth interface at the top end of the die member.
rw/ - 5 -( 111~
Other features and many of the attendant advantages of this invention are set forth or rendered obvious by the following detailed description which is to be taken together with the accompanying drawings wherein like numerals depict like parts, and wherein:
Fig. 1 is a sectional view in elevation, of a crystal growing apparatus with certain parts represented schematically, and illustrating a preferred form of capillary die in accordance with the present invention;
Fig. 2 is an end view of the die of Fig. l;
Fig. 3 is a top plan view, on a greatly enlarged scale of the die of Fig. l;
Fig. 4 is a top plan view, on a greatly enlarged scale, showing a second form of die in accordance with the present invention; and Fig. 5 is a top plan~view, on a greatly enlarged scale, showing a third form of die in accordance with the present invention.
Capillary dies may be made in accordance with the present invention for use in producing monocrystalline bodies of a variety of shapes. However, the invention is particularly dapted for forming dies for producing relatively thin, wide flat silicon ribbons by the EFG Process, and the following escription is directed to this preferred embodiment of this invention. ~lowever, one skilled in the art will know the appro-priate selection of materials which will permit the die and cruci-ble combinations described in the following description to be used :` ( 1~6~1~5 to grow crystalline bodies of other congruently melting materials that solidiEy in identifiable crystal lattices.
The invention is also applicable to growth of other materials such as eutectic compositions.
Figs. 1-3 show a preferred form of capillary die for growing silicon ribbon in accordance with the present invention.
The illustrated capillary die comprises a solid graphite block 20 including a generally rectangular horizontal bottom surface 22, a pair of vertically oriented parallel end surfaces 24 and 26, op-positely inclined side surfaces 28 and 30 and a die top surface 32 Die top surface ~2 is of a size and shape corresponding substan-tially to the cross-section of ribbon to be grown. For example, for growing ribbon approximately 3 inches wide and 0.005 inches thick the die top surface 32 should measure 3 inches by 0.005 inches.
As seen particularly in Fig. 2 block 20 is tapered so that the die bottom surface 22 is larger in plan than the die top surface 32. Tapering the die in this manner is preferred since it provides a die which has greater structural stability and reduces the likelihood of accldentally in,juring the top surface during formation of the capillaries hereinafter described. This consideration is particularly improtant in the case of dies which are designed for,growing especially thin crystals, e.g. 0.005 inch thick silicon ribbons. Tapering the die in this manner also has the advantage of permitting the die capillaries to draw melt from a greater area of melt as will become clear from the description following.
. _._ 11 Il , 1~6~5 An unique f eature and particular advantage of the present invention is the manner in which the die capillaries are formed Referring in particular to Figs. l and 3, the die capillaries comprise a plurality of shallow grooves or slots 36 formed in the die side surfaces 28 and 30. Each slot 36 is of suitable size and shape for acting as a capillary. For example, the slots 36 illustrated in the Figs. 1-3 embodiment of the invention are generally triangular in cross section, have an apex angle of about 60 and an apex depth of approximately l/64 inch. Such slots are suitable for functioning as a capillar ies for molten silicon. It will be understood, however, that the capillary slots may have other shapes and sizes. For example the capillary slots may comprise elongate grooves having a semi-circular cross-section of suitable dimension as shown at 36A
in Fig. 4, or the capillary slots may comprise elongate grooves having a substantially square cross-section of suitable dimension as shown at 36B in Fig. 5. For ease of manufacture the capil-lary slots preferably will have a depth which does not exceed twice their width. As seen in the drawings the capillary slots 36, 36A, 36B extend to and intersect the die top surface 32. Slots 36, 36A, 36B preferably but need not extend to and intersect the die bottom surface 22.
Although not required, it is also preferred to include a blind hole or well 40 in the die top end surface 32. Well 40 should be of sufficient size to provide a space for collection of melt, i.e. so as to provide a thermal reservoir whereby to convey heat the center of the die. One skilled in the art will also recognize that well 40 will also facilitate distribu-on of t.he melt widthwise o: the die top wa1l 32 during seeding.
1~16~8~;
The die block 20 is disposed within a quartz or graphite crucible 42. The latter is of conventional design and may includ~
for example a bottom wall 44, and a cylindrical side wall 46, which together define an interior space for containing a melt 48 of the material to be grown, i.e. silicon. As seen in Fig. 1 the die block 20 is positioned in the melt 48 so that the die bottom surface 22 including the lower ends of the capillaries 36 are disposed below the surface of the melt 48, while the die top surface 32 is above the surface of the melt. The die block 20 is retained in fixed position relative to the crucible 42 by means of suitable mounting pins 50 which extend through openings in the die block and are received in suitable openings in wall 46 of crucible 42. Alternatively the pins may be located so that they rest on the upper end surface of crucible wall 46. The die and crucible are mounted in a suitable crystal growing furnace, e.g.
a furnace of the type shown in Fig. 1 of U.S. Letters Patent No. 3,591,348 supra.
One skilled in the art will recognize that the capillary die arrangement of the present invention oEfers a number of advantages over prior art capillary dies. Fox one thing, the die may be formed in a single piece. Another advantage of the present invention derives from the fact that the die capillaries are for~ed in the outer surfaces of the die. As a result the outer edges of the die top surface are substantially at the temp-erature of the melt, thereby facilitating seeding. Moreover, the possibility of formation and accrual of silicon carbide particles in the capillaries and/or at the die upper surface is reduced.
~ 5 Furthermore, the capillaries can be made with great precision by simple machining techniques, e.g. by means of a cutting wheel or saw. This is advantageous in the case of brittle materials like graphite since there is less likelihood of S damaging the die material during formation of the capillaries.
It also is advantageious in the case of very hard die materials such as molybdenum (which is used in growing sapphire) since it is far easier to form an external groove than an internal bore of capillary size. Another advantage of the present invention is the ability to better control the temperature across the die top surface. In this-regard one skilled in the art will recognize that with a sufficient number of capillary grooves relatively closely spaced to one another, the die top surface can be rendered essentially isothermal.
The foLlowing example illustrates a preferred mode of practicing the invention~
EXAMPLE
The crucible and die arrangement shown in Figs. 1-3 is produced as follows:
A solid graphite die block 20 is formed having a rectang-ular, bottom surface 22 of dimension 0.250 by 3.0 inches, slanted rectangular side surfaces 28 and 30 of dimension 2.75 by 3.0 inches, and a top surface 32 of dimension 3 inches by 0.005 inches. This die is disposed in a 3.08 inch diameter graphite crucible 42. The die block is held in position in the crucible by graphite pins 50. The side surfaces 28 and 30 of block 20 are grooved as shown in Fig. 1 by vee-shaped grooves 36 each having an apex angle of about 60. Grooves 36 are substan-tailly parallel,to one another and are spaced, apex-to-apex, approximately 0.120 inches apart. Grooves 36 extend I
. . .
~ 16~85 between the die block bottom and top walls ~2 and 32, respectively .
The crucible is charged with substantially pure silicon and a sub-stantially monocrystalline silicon ribbon is grown according to the EFG method by drawing the ribbon from a film of melt which extends across the top wall 32 of the die and communicates with th e melt in grooves 36. The molten silicon in the crucible is main-tained at a temperature of about 40C above its melting point, while the die top surface is held at about 10C above the same melting point. Once growth has commenced, the pulling speed is held at about 3 inches per m~nute. Growth continues until substantially all the silicon within the crucible 42 is consumed.
Various changes may be made in the invention as will be obvious to one skilled in the art. For example, the die may be formed from two or more pieces which are joined together by suitable means. Capillaries also may be formed in the end ., ................. ", .
surfaces 2~ and 26 in those cases where the upper ends of side surfaces 28 and 30 are apart far enough. Moreover, the dies may be produced in a variety of shapes and sizes. Thus the die member may be made with six slanted sides so that its upper end surface is hexagonal, whereby to permit growth of hexagonal rods as is advantageous in manufacturing silicon solar cells. Each or only some of the six inclined side surfaces could have capilla~ Y
slots as above described. Still other changes will be obvious to one skilled in the art.
Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for use in a system for growing cystalline bodies of selected shape from a melt wherein said melt is derived from a crucible by a capillary die member, and said crystalline body is grown from a liquid/solid growth interface at the top end of said capillary die member, said apparatus comprising an improved capillary die member having a top end, a bottom end, at least one exterior side wall surface of said capillary die member extending between said top and bottom ends, and a plurality of capillaries in the form of a plurality of grooves of capillary dimension formed in said exterior side wall surface of said die member, said grooves terminating at select locations along the top end of said die member so that melt can be drawn from said crucible to said top end via said grooves as said crystalline body is grown from said liquid/solid growth inter-face at the top end of said die member.
2. Apparatus according to claim 1, wherein said die member is a single integrally-formed member.
3. Apparatus according to claim 1 including a cavity formed in the top end of said die member for collecting melt as said crystalline body is grown from said liquid/solid growth interface at said top end.
4. Apparatus according to claim 3, wherein said grooves extend substantially from said bottom end to said top end.
5. Apparatus according to claim 1, wherein said bottom end is larger in plan view than said top end.
6. Apparatus according to claim 5, wherein said die top end comprises a relatively narrow, elongated rectangle in plan view.
7. Apparatus according to claim 1 for use is a system for growing crystalline bodies of silicon, wherein said die member is formed of graphite.
8. Apparatus according to claim 6 further including a crucible and means for supporting said die member with respect to said crucible.
9. Apparatus according to claim 1 wherein said die member comprises a tapered block having rectangular top and bottom ends, said bottom end being larger in plan view than said top end.
10. Apparatus according to claim 1, wherein said member includes at least two side wall surfaces, each including a plurality of said grooves.
11. Apparatus according to claim 8, wherein said die member includes at least two holes extending through said member and said means for supporting said die member with respect to said crucible comprises at least two pins extendable through the respective holes in said die member and supportable by said crucible.
12. Apparatus according to claim 1, wherein said grooves are each triangular in cross-section.
13. Apparatus according to claim 12, wherein the apex angle of each said groove is approximately 60°.
14. Apparatus according to claim 1, wherein said grooves are each substantially semi-circular in cross-section.
15. Apparatus according to claim 1, wherein said grooves are each substantially square in cross-section.
16. Apparatus according to claim 1, wherein the depth of each of said grooves is less than twice the width of said groove.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US89949778A | 1978-04-24 | 1978-04-24 | |
| US899,497 | 1978-04-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116985A true CA1116985A (en) | 1982-01-26 |
Family
ID=25411088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000322467A Expired CA1116985A (en) | 1978-04-24 | 1979-02-28 | Capillary die |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS6033799B2 (en) |
| AU (1) | AU527424B2 (en) |
| CA (1) | CA1116985A (en) |
| DE (1) | DE2916389A1 (en) |
| FR (1) | FR2424060A1 (en) |
| GB (1) | GB2019243B (en) |
| IL (1) | IL56786A (en) |
| IN (1) | IN151094B (en) |
| NL (1) | NL7902358A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3366718D1 (en) * | 1983-02-09 | 1986-11-13 | Commissariat Energie Atomique | Method of producing plates of metallic or semiconducting material by moulding without direct contact with the walls of the mould |
| WO2003033780A1 (en) * | 2001-10-16 | 2003-04-24 | Utar Scientific Inc. | Method of growing piezoelectric lanthanide gallium crystals |
| JP7436978B2 (en) * | 2019-10-28 | 2024-02-22 | Ａｇｃ株式会社 | Single crystal ingot, crystal growth die, and method for manufacturing single crystal |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1577413A (en) * | 1976-03-17 | 1980-10-22 | Metals Research Ltd | Growth of crystalline material |
-
1979
- 1979-02-28 CA CA000322467A patent/CA1116985A/en not_active Expired
- 1979-02-28 IN IN143/DEL/79A patent/IN151094B/en unknown
- 1979-03-05 IL IL5678679A patent/IL56786A/en unknown
- 1979-03-07 AU AU44871/79A patent/AU527424B2/en not_active Ceased
- 1979-03-12 GB GB7908542A patent/GB2019243B/en not_active Expired
- 1979-03-26 NL NL7902358A patent/NL7902358A/en not_active Application Discontinuation
- 1979-04-20 JP JP4890179A patent/JPS6033799B2/en not_active Expired
- 1979-04-23 FR FR7910233A patent/FR2424060A1/en active Granted
- 1979-04-23 DE DE19792916389 patent/DE2916389A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| AU4487179A (en) | 1979-11-01 |
| GB2019243A (en) | 1979-10-31 |
| NL7902358A (en) | 1979-10-26 |
| JPS6033799B2 (en) | 1985-08-05 |
| FR2424060B1 (en) | 1984-08-24 |
| DE2916389A1 (en) | 1979-10-31 |
| GB2019243B (en) | 1982-06-16 |
| JPS54142180A (en) | 1979-11-06 |
| FR2424060A1 (en) | 1979-11-23 |
| IN151094B (en) | 1983-02-19 |
| IL56786A (en) | 1981-10-30 |
| AU527424B2 (en) | 1983-03-03 |
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