US 11,668,020 B2
Systems and methods for production of low oxygen content silicon
Gaurab Samanta, Brentwood, MO (US); Parthiv Daggolu, Creve Coeur, MO (US); Sumeet Bhagavat, St. Charles, MO (US); Soubir Basak, Chandler, AZ (US); and Nan Zhang, O'Fallon, MO (US)
Assigned to GlobalWafers Co., Ltd., Hsinchu (TW)
Filed by GlobalWafers Co., Ltd., Hsinchu (TW)
Filed on Jul. 20, 2021, as Appl. No. 17/380,393.
Application 17/380,393 is a continuation of application No. 16/916,577, filed on Jun. 30, 2020, granted, now 11,136,691.
Application 16/916,577 is a continuation of application No. 15/780,520, granted, now 10,745,823, issued on Aug. 18, 2020, previously published as PCT/US2016/064448, filed on Dec. 1, 2016.
Claims priority of provisional application 62/263,355, filed on Dec. 4, 2015.
Prior Publication US 2021/0348298 A1, Nov. 11, 2021
Int. Cl. C30B 15/20 (2006.01); C30B 29/06 (2006.01); C30B 15/30 (2006.01); C30B 15/10 (2006.01); C30B 30/04 (2006.01)
CPC C30B 15/20 (2013.01) [C30B 15/10 (2013.01); C30B 15/30 (2013.01); C30B 15/305 (2013.01); C30B 29/06 (2013.01); C30B 30/04 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A method for producing a silicon ingot, the method comprising:
withdrawing a seed crystal from a melt comprising an amount of melted silicon in a crucible to form the silicon ingot, the crucible enclosed in a vacuum chamber containing a cusped magnetic field; and
regulating at least one process parameter, wherein regulating the at least one process parameter comprises regulating a magnetic field strength, wherein the at least one process parameter is regulated in at least two stages, the at least two stages comprising:
a first stage corresponding to formation of the silicon ingot up to an intermediate ingot length; and
a second stage corresponding to formation of the silicon ingot from the intermediate ingot length to the total ingot length;
wherein regulating the magnetic field strength during the first stage comprises regulating, during the first stage, the magnetic field strength to a strength between 0.02 and 0.05 Tesla at an edge of the silicon ingot at a melt-solid interface, and regulating the magnetic field strength to a strength between 0.05 and 0.12 Tesla at a wall of the crucible; and
wherein regulating the magnetic field strength during the second stage comprises:
increasing the magnetic field strength at the edge of the silicon ingot at the melt-solid interface relative to the first stage, wherein, during the second stage, the magnetic field strength is between 0.03 and 0.075 Tesla at the edge of the silicon ingot at the melt-solid interface, and
increasing the magnetic field strength at the wall of the crucible relative to the first stage, wherein, during the second stage, the magnetic field strength is between 0.075 and 0.18 Tesla at the wall of the crucible.