Weir for improved crystal growth in a continuous Czochralski process
View Patent ↗An apparatus for growing ingots by the Czochralski method includes a growth chamber defining an enclosure configured to circulate a purge gas about the growing ingot and a crucible provided in the growth chamber configured to hold the molten silicon. A weir is supported in the crucible and is configured to separate the molten silicon into an inner growth region surrounding the melt/crystal interface from an outer region configured to receive the crystalline feedstock. The weir comprises at least one sidewall extending vertically and a cap extending substantially perpendicularly to the sidewall.
1. An apparatus for growing an ingot by the Czochralski method, the ingot being grown from a melt/crystal interface in a quantity of molten silicon replenished by crystalline feedstock, the apparatus comprising:
a growth chamber defining an enclosure configured to circulate a purge gas about the growing ingot;
a crucible provided in the growth chamber configured to hold the molten silicon;
a weir mounted in the crucible and configured to separate the molten silicon into an inner growth region surrounding the melt/crystal interface from an outer region configured to receive the crystalline feedstock, the weir having a T-shaped cross-section and including at least one sidewall extending vertically and a cap extending substantially perpendicularly to the sidewall in a direction radially inward from the sidewall, wherein the cap and the sidewall define a modified flow region located radially inward from the sidewall and extending from the molten silicon to a top of the sidewall, wherein the sidewall prevents radial outward gas flow from the modified flow region.
2. The apparatus according to claim 1 , wherein the cap extends substantially perpendicular to the sidewall in a direction radially outward from the at least one sidewall.
3. The apparatus according to claim 1 , further comprising a second weir mounted in the crucible and having at least one sidewall extending vertically, the second weir located radially outward from the weir.
4. The apparatus according to claim 3 , wherein the weir has a lower height than the second weir.
5. The apparatus according to claim 1 , further comprising a second weir mounted in the crucible and having at least one sidewall extending vertically, the second weir located radially inward from the weir.
6. The apparatus according to claim 1 , wherein the weir is fabricated from quartz.
7. The apparatus according to claim 1 , further comprising at least one heater for heating the crucible.
8. A method for continuous Czochralski crystal growing wherein one or more crystal ingots are pulled in a growth chamber from a melt/crystal interface defined in a crucible containing molten crystalline material that is replenished by feedstock, the method comprising:
separating the molten crystalline material into an inner growth region surrounding the melt/crystal interface and an outer region for receiving the feedstock using a weir having a T-shaped cross-section;
flowing an inert gas in contact with the weir and the melt such that the weir prevents radial outward flow of the inert gas below a top of the weir and a partial pressure of a silicon monoxide gas released from the melt is increased at a radial inner maximum weir erosion point.
9. The method according to claim 8 , wherein the weir includes a cap, and the inert gas is directed in a manner to flow under the cap.
10. The method according to claim 8 , wherein flowing the inert gas includes flowing Argon gas.
11. The method according to claim 8 , further comprising heating the crucible using at least one heater in proximity to the crucible.
12. The method according to claim 8 , further comprising manipulating pressure within the chamber to evacuate the silicon monoxide gas.
13. The method according to claim 12 , wherein manipulating pressure includes using a vacuum device.
14. The method according to claim 8 , wherein the maximum weir erosion point is a point along the melt/crystal interface.
15. A system for growing ingots by the Czochralski method, the ingots being drawn from a melt/crystal interface in a quantity of molten silicon replenished by crystalline feedstock, the apparatus comprising:
a growth chamber defining an enclosure configured to circulate a purge gas about the growing ingot;
a crucible provided in the growth chamber configured to hold the molten silicon;
a feed supply for supplying the crystalline feedstock;
a heater for heating the crystalline feedstock and the molten silicon; and
a weir supported in the crucible, and configured to separate the molten silicon into an inner growth region surrounding the melt/crystal interface from an outer region configured to receive the crystalline feedstock, the weir having a T-shaped cross-section and comprising at least one sidewall extending vertically and a cap extending substantially perpendicularly to the sidewall, wherein the cap and the sidewall define a modified flow region extending from the molten silicon to a top of the sidewall, wherein the sidewall prevents radial outward gas flow from the modified flow region.
16. The system according to claim 15 , wherein the cap extends substantially perpendicular to the sidewall in a direction radially inward from the at least one sidewall.
17. The system according to claim 15 , wherein the cap extends substantially perpendicular to the sidewall in a direction radially inward from the at least one sidewall, and substantially perpendicular to the sidewall in a direction radially outward from the at least one sidewall.
18. The system according to claim 15 , further comprising a second weir mounted in the crucible and having at least one sidewall extending vertically, the second weir located radially outward from the weir.
19. The system according to claim 18 , wherein the weir has a lower height than the second weir.
20. The system according to claim 15 , wherein the weir includes quartz.