Apparatus and method of use for casting system with independent melting and solidification

• US 20110158887A1
• Filed: 08/21/2009
• Published: 06/30/2011
• Est. Priority Date: 08/27/2008
• Status: Abandoned Application

• Current Assignee: AMG Idealcast Solar Corporation
• Original Assignee: AMG Idealcast Solar Corporation
• Inventors: Dey, Soham, Wu, Bei, Clark, Roger F., Stoddard, Nathan G., Cliber, James A., Stark, Douglas L.
• Application Number:
  US13/061,081
• Publication Number:
  US 20110158887A1
• Time in Patent Office: Days
• US Class Current: 423/348
• CPC Class Codes: C30B 11/001 Continuous growth
• CPC Class Codes: C30B 11/003 Heating or cooling of the melt or the crystallised material
• CPC Class Codes: C30B 11/007 Mechanisms for moving either the charge or the heater
• CPC Class Codes: C30B 11/04 adding crystallising materials or reactants forming it in situ to the melt
• CPC Class Codes: C30B 15/02 adding crystallising materials or reactants forming it in situ to the melt
• CPC Class Codes: C30B 15/20 Controlling or regulating controlling or regulating in general G05
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: C30B 35/00 Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
• CPC Class Codes: C30B 35/005 Transport systems

Abstract

This invention relates to a two or three-stage apparatus and method of use to produce high purity silicon, such as for use in solar panels and/or photovoltaics. The device of this invention includes a melting apparatus with a delivery device, a holding apparatus with a tipping or transfer mechanism, and at least one solidification apparatus for receiving a molten feedstock. The optimized designs of individual apparatuses function efficiently in combination to produce high purity silicon.

Claims

1. A melting apparatus suitable for producing high purity silicon, the apparatus comprising:

a heat source for melting a solid feedstock;

a delivery device for supplying the solid feedstock to the heat source; and

a catch pan for receiving a molten feedstock from the heat source and flowing the molten feedstock to a holding apparatus for further processing.

2. The apparatus of claim 1, wherein surfaces for contacting the solid feedstock or the molten feedstock comprise high purity components.

3. The apparatus of claim 1, wherein the melting apparatus operates substantially continuously.

4. The apparatus of claim 1, wherein the heat source comprises a slotted platform.

5. The apparatus of claim 1, wherein the heat source comprises a flat or a contoured hearth.

6. The apparatus of claim 5, wherein the heat source comprises a plurality of rods in a generally parallel configuration.

7. The apparatus of claim 6, wherein the rods comprise a protective cover.

8. The apparatus of claim 1, wherein the heat source comprises silicon carbide or graphite.

9. The apparatus of claim 1, wherein the delivery device comprises a fork disposed at an end of an elongated member, the fork comprises a plurality of generally parallel tines for supporting the solid feedstock.

10. The apparatus of claim 9, further comprising a spacing of the tines for passing between one or more slots in the heat source.

11. The apparatus of claim 9, wherein the fork is movable between a first position for loading the solid feedstock and a second position for delivering the solid feedstock to the heat source.

12. The apparatus of claim 11, wherein the fork is movable to an intermediate position for heating the solid feedstock above ambient temperature.

13. The apparatus of claim 1, wherein the delivery device is selected from one of the group consisting of a walking beam, a rotating tube, a rotary feeder, a vibratory feeder, a chute and door mechanism, a moving tray, a pushing bar, and combinations thereof.

14. The apparatus of claim 1, further comprising an inert gas supply for displacing contaminants from the apparatus.

15. The apparatus of claim 1, wherein the delivery device comprises an environmental lock.

16. The apparatus of claim 1, wherein the catch pan comprises a sloped bottom for draining the molten feedstock.

17. The apparatus of claim 1, wherein the catch pan comprises a baffle or a weir.

18. The apparatus of claim 1, wherein the catch pan comprises a pour spout, a trough, a siphon tube, a plunger or combinations thereof.

19. The apparatus of claim 1, wherein the heat source comprises a heater disposed with respect to a top of slot openings.

20. A method of melting a solid feedstock suitable for producing high purity silicon, the method comprising:

providing a solid feedstock;

supplying the solid feedstock with a delivery device to a heat source;

melting the solid feedstock with the heat source; and

receiving a molten feedstock from the heat source in a catch pan for flowing the molten feedstock to further processing or staging.

21. The method of claim 20, wherein the supplying comprises:

placing one or more pieces of the solid feedstock on a fork at a first position;

moving the fork by an elongated member to a second position with respect to the heat source, wherein the fork is disposed at an end of the elongated member;

lowering tines of the fork into one or more slots of the heat source to place the solid feedstock on fingers of the heat source; and

withdrawing the fork from the heat source.

22. The method of claim 21, wherein the moving comprises passing through an environmental lock.

23. The method of claim 21, further comprising loading the fork with a robot under an inert atmosphere connected with respect to a hot zone.

24. The method of claim 21, further comprising warming the solid feedstock to above ambient temperature in an intermediate position.

25. The method of claim 20, further comprising flowing an inert gas to prevent impurities.

26. The method of claim 20, wherein the delivery device is selected from one of the group consisting of a walking beam, a rotating tube, a rotary feeder, a vibratory feeder, a chute and door mechanism, a moving tray, a pushing bar, and combinations thereof.

27. The method of claim 20, wherein the melting comprises using resistance heaters, induction heaters, or combinations thereof.

28. The method of claim 20, wherein the melting comprises contacting the solid feedstock with a plurality of rods and flowing the molten feedstock through at least one slot.

29. The method of claim 20, wherein the receiving comprises flowing down an incline.

30. The method of claim 20, wherein the receiving comprises flowing the molten feedstock with respect to a baffle, a weir, or combinations thereof to stop a piece of floating unmelted feedstock.

31. The method of claim 20, wherein the receiving comprises flowing the molten feedstock with respect to a spill-over barrier to exclude sinking particles or contaminants.

32. The method of claim 20, further comprising transferring the molten feedstock from the catch pan to a holding vessel.

33. The method of claim 32, wherein the transferring comprises flowing through a pour spout, a siphon tube, a plunger, a trough or combinations thereof.

34. A holding apparatus suitable for producing high purity silicon, the apparatus comprising:

a holding vessel with an outlet for receiving a molten feedstock;

at least one heater; and

a transfer or a tipping mechanism for flowing the molten feedstock to further processing or staging.

35. The apparatus of claim 34, wherein the holding vessel comprises fused silica.

36. The apparatus of claim 34, wherein the outlet comprises a funnel, a spout, a trough, or port through a wall of the holding vessel.

37. The apparatus of claim 34, wherein the holding vessel comprises:

a first end having a depth and a second end having an increased depth; and

a lid.

38. The apparatus of claim 34, further comprising inert gas supply.

39. The apparatus of claim 34, wherein the tipping mechanism comprises a first fixed leg and a second adjustable leg to change a height of an end of the holding vessel.

40. The apparatus of claim 34, further comprising a spout, a funnel, a trough or combinations thereof to transfer a molten feedstock from the holding vessel to a solidification apparatus.

41. The apparatus of claim 34, wherein the apparatus comprises a portable device movable between locations and comprises flexible or quick connections for utilities.

42. The apparatus of claim 34, further comprising a dopant source.

43. The apparatus of claim 34, further comprising a support for the holding vessel, wherein the support comprises carbon-carbon.

44. A method of using a holding apparatus suitable for producing high purity silicon, the method comprising:

receiving a molten feedstock into a holding vessel

maintaining the molten feedstock at or above a feedstock melting point; and

transferring the molten feedstock through an outlet.

45. The method of claim 44, wherein the maintaining comprises superheating the molten feedstock.

46. The method of claim 44, wherein the receiving occurs on a generally continuous basis and the transferring occurs on a generally periodic basis.

47. The method of claim 44, wherein the transferring comprises tilting the holding vessel with a tipping mechanism.

48. The method of claim 44, further comprising flowing an inert gas to remove contaminants from the holding apparatus.

49. A solidification apparatus suitable for producing high purity silicon, the apparatus comprising:

a crucible or vessel for receiving a molten feedstock from a trough;

at least one heater; and

at least one heat sink.

50. The apparatus of claim 49, further comprising a vacuum-tight interlock dock/undock.

51. The apparatus of claim 49, wherein the crucible or vessel comprises a trough for decanting impurity laden material during solidification.

52. The apparatus of claim 49, further comprising a decanting device to tilt the crucible or vessel during solidification.

53. The apparatus of claim 49, further comprising at least one seed crystal disposed with respect to an interior surface of the crucible or vessel.

54. The apparatus of claim 49, further comprising a melt detection system.

55. The apparatus of claim 49, wherein the apparatus comprises a portable device movable between locations and comprises flexible or quick connections for utilities.

56. The apparatus of claim 49, wherein the at least one heater comprises a top heater and a bottom heater.

57. The apparatus of claim 56, further comprising at least one side heater.

58. The apparatus of claim 49, wherein the apparatus comprises a dopant source.

59. The apparatus of claim 49, wherein the heat sink comprises a metallic plate disposed with respect to a bottom of the crucible.

60. The apparatus of claim 49, further comprising a vacuum source and an inert gas supply.

61. A method of solidifying a molten feedstock suitable for producing high purity silicon, the method comprising:

providing a molten feedstock;

receiving the molten feedstock in a crucible;

providing heat to the molten feedstock with a heater to control a temperature within the crucible; and

cooling the molten feedstock from a bottom or at least one side to crystallize the molten feedstock.

62. The method of claim 61, wherein the receiving comprises vacuum-tight, atmosphere controlled linking of the apparatus with a holding vessel while flowing molten feedstock therebetween.

63. The method of claim 61, further comprising moving a solidifying apparatus from a holding apparatus or melting apparatus to a location for solidification.

64. The method of claim 61, further comprising doping the molten feedstock with a dopant.

65. The method of claim 61, further comprising orienting a solidified product with seed crystals.

66. The method of claim 61, wherein the solidified product is selected from the group consisting of multicrystalline silicon, monocrystalline silicon, near monocrystalline silicon, geometric multicrystalline silicon, and combinations thereof.

67. The method of claim 61, further comprising placing seed crystals at least substantially to cover a bottom or at least one side of the crucible.

68. The method of claim 61, further comprising placing seed crystals at least substantially to cover a bottom and all internal sides of the crucible.

69. An apparatus suitable for producing high purity silicon, the apparatus comprising:

a melting apparatus for melting a solid feedstock to a molten feedstock;

a holding apparatus for receiving the molten feedstock from the melting apparatus; and

at least one solidification apparatus for solidifying the molten feedstock into a solid product.

70. The apparatus of claim 69, wherein the melting apparatus comprises a fork delivery device for placing the solid feedstock over a slot in a heat source.

71. The apparatus of claim 69, wherein the holding apparatus comprises a holding vessel and a tipping mechanism.

72. The apparatus of claim 69, further comprising an inert gas supply for displacing contaminants from the apparatus.

73. The apparatus of claim 72, wherein fresh inert gas sweeps across a surface of silicon in exposed areas before exhausts from the apparatus.

74. The apparatus of claim 69, wherein each solidification apparatus comprises a crucible, a heater and a heat sink.

75. The apparatus of claim 69, wherein the melting apparatus and the holding apparatus combine in a single unit.

76. The apparatus of claim 69, wherein at least one of the melting apparatus, the holding apparatus, or the at least one solidification apparatus comprises a portable device movable between locations and comprises flexible or quick connections for utilities.

77. The apparatus of claim 69, wherein more than one melting apparatus supplies molten feedstock to the same holding apparatus.

78. The apparatus of claim 69, wherein at least five solidification apparatuses are filled from the same holding apparatus.

79. The apparatus of claim 69, wherein the melting apparatus operates in a generally continuous mode, the holding apparatus operates in a generally semi-batch mode, and the solidification apparatus operates in a generally batch mode.

80. The apparatus of claim 69, wherein each solidification apparatus moves with respect to the melting apparatus or the holding apparatus.

81. The apparatus of claim 69, where each solidification apparatus remains generally fixed and the melting apparatus or the holding apparatus move to supply each solidification apparatus.

82. The apparatus of claim 69, wherein the melting apparatus, the holding apparatus and the each solidification apparatus comprise a different device from others devices.

83. The apparatus of claim 69, wherein a volume of a holding vessel in the holding apparatus exceeds a volume of a crucible in the solidification apparatus.

84. The apparatus of claim 69, wherein each solidification apparatus is disposed generally radially with respect to the melting apparatus or the holding apparatus.

85. The apparatus of claim 69, wherein each solidification apparatus is disposed generally linearly with respect to the melting apparatus or the holding apparatus.

86. The apparatus of claim 69, further comprising a carbon-fiber composite catch receptacle for containing spills of the molten feedstock.

87. A method suitable for producing high purity silicon, the method comprising:

providing a solid feedstock;

loading the solid feedstock into a melting apparatus;

melting the solid feedstock in the melting apparatus to a molten feedstock;

transferring the molten feedstock to a holding apparatus;

flowing the molten feedstock into a solidification apparatus from the holding apparatus; and

solidifying the molten feedstock to a solid product in a crucible of the solidification apparatus.

88. The method of claim 87, further comprising flowing an inert gas through at least one of the melting apparatus, the holding apparatus or the solidification apparatus.

89. The method of claim 87, wherein the flowing occurs through an atmosphere controlled interlock between the holding apparatus and the solidification apparatus.

90. The method of claim 87, further comprising moving the solidification apparatus to allow a second solidification apparatus to receive molten feedstock.

91. The method of claim 87, further comprising moving at least one of the melting apparatus or the holding apparatus with respect to a plurality of solidification apparatuses.

92. The method of claim 91, wherein the moving at least one of the melting apparatus or the holding apparatus comprises generally rotating to a plurality of radially disposed solidification apparatuses.

93. The method of claim 91, wherein the moving at least one of the melting apparatus or the holding apparatus comprises generally locating with respect to a plurality of generally linearly disposed solidification apparatuses.

94. The method of claim 87, further comprising making utility connections between a utility supply and the melting apparatus, the holding apparatus or the solidification apparatus.

95. The method of claim 87, further comprising removing impurities from a crucible by decanting a top molten remainder.

96. The method of claim 87, further comprising moving the apparatus on at least two rails while powering at least one of the melting apparatus, the holding apparatus, or the solidification apparatus with a third rail.

97. A high purity silicon ingot made by a three-stage method, the method comprising:

providing a solid feedstock comprising silicon;

loading the solid feedstock into a melting apparatus;

melting the solid feedstock in the melting apparatus to a molten feedstock;

transferring the molten feedstock to a holding apparatus;

flowing the molten feedstock into a solidification apparatus from the holding apparatus; and

solidifying the molten feedstock to a solid product in a crucible of the solidification apparatus.

98. The ingot of claim 97, wherein the method excludes drawing or rotating silicon.

99. The ingot of claim 97, wherein the ingot comprises primarily silicon selected from the group consisting of multicrystalline silicon, monocrystalline silicon, near monocrystalline silicon, geometric multicrystalline silicon, and combinations thereof.

100. The ingot of claim 97, wherein the ingot is substantially free from radially distributed defects.

101. The ingot of claim 97, wherein the ingot comprises a carbon concentration of about 2×

10¹⁶ atoms/cm³ to about 5×

10¹⁷ atoms/cm³, an oxygen concentration not exceeding 7×

10¹⁷ atoms/cm³, and a nitrogen concentration of at least 1×

10¹⁵ atoms/cm³.