Method and apparatus for growing a ribbon crystal with localized cooling

1. A method of growing a ribbon crystal, the method comprising:

providing a cooling apparatus;

passing at least two strings through a molten material to produce a partially formed ribbon crystal having an end section and a middle section, the end section including one of the at least two strings, the one string and middle section defining a given portion of the partially formed ribbon crystal; and

convectively cooling the given portion of the partially formed ribbon crystal with the cooling apparatus to control the thickness of the given portion.

2. The method as defined by claim 1 wherein convectively cooling comprises causing the thickness of the given portion to be greater than the thickness of the middle section.

3. The method as defined by claim 1 wherein the partially formed ribbon crystal forms an interface with the molten material, wherein convectively cooling comprises varying the convection cooling to vary the location of the interface, the given portion having a thickness that is a function of the location of the interface.

4. The method as defined by claim 1 wherein convectively cooling comprises directing a fluid stream toward the given portion.

5. The method as defined by claim 4 wherein a fluid delivery apparatus directs the fluid stream to strike the given portion, the fluid stream contacting a second portion of the partially formed ribbon crystal after contacting the given portion, the fluid stream cooling the second portion.

6. The method as defined by claim 4 wherein a fluid delivery apparatus directs the fluid stream toward the given portion, the fluid delivery apparatus radiatively cooling the given portion.

7. The method as defined by claim 1 wherein the partially formed ribbon crystal forms an interface with the molten material, further wherein convectively cooling comprises directing a stream of gas to contact a specific location of the given portion, the specific location being spaced from the interface.

8. The method as defined by claim 1 wherein the partially formed ribbon crystal has a ribbon width, the given portion having a width that is no greater than about half the ribbon width.

9. A method of growing ribbon crystal, the method comprising:

providing a crucible containing molten material;

passing at least two strings through the molten material to produce a partially formed ribbon crystal; and

directing a fluid to a given portion of the partially formed ribbon crystal, the fluid convectively cooling the given portion to control the thickness of the given portion.

10. The method as defined by claim 9 wherein the partially formed ribbon crystal has an edge generally defined by one of the strings, the partially formed ribbon crystal also having an inward portion spaced from the edge, the given portion being between the edge and the inward portion, directing comprising causing the thickness of the given portion to be greater than the thickness of the inward portion.

11. The method as defined by claim 9 wherein directing comprises providing a jet that directs the fluid to the given portion, the jet radiatively cooling the given portion.

12. The method as defined by claim 11 wherein the jet directs the fluid stream to strike the given portion, the fluid stream contacting a second portion of the partially formed ribbon crystal after contacting the given portion, the fluid stream cooling the second portion.

13. The method as defined by claim 9 wherein the fluid comprises a gas blown from a jet toward the given portion, the gas being at a temperature of between about 100-400 degrees C.

14. The method as defined by claim 9 wherein the partially formed ribbon crystal forms an interface with the molten material, further wherein the fluid contacts a specific location of the given portion, the specific location being spaced from the interface.

15. An apparatus for forming a ribbon crystal, the ribbon crystal having an end section and a middle section, the end section including a string, the string and middle section defining a given portion of the partially formed ribbon crystal, the apparatus comprising:

a crucible for containing molten material, the crucible forming a string hole for passing string through the molten material for growing the ribbon crystal; and

a gas jet having an outlet port facing inwardly for directing a gas generally inwardly toward the given portion of the growing ribbon crystal to control the thickness of the given portion.

16. The apparatus as defined by claim 15 wherein the gas jet comprises a radiatively cooling material.

17. The apparatus as defined by claim 16 wherein the radiatively cooling material comprises graphite.

18. The apparatus as defined by claim 15 wherein the gas jet is horizontally spaced from the crucible.

19. The apparatus as defined by claim 15 further comprising a second gas jet, the first gas jet directing gas in a first direction, the second gas jet directing gas in a second direction, the first and second directions being different directions and generally parallel.

20. The apparatus as defined by claim 19 wherein the first gas jet and second gas jet produce respective gas streams that are generally coaxial.

21. The apparatus as defined by claim 15 further comprising a string through the string hole and a growing ribbon crystal.