Method for controlling oxygen content of silicon crystals using a combination of cusp magnetic field and crystal and crucible rotation rates
US5178720A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 14, 1991 |
| Grant date | Jan 12, 1993 |
| Priority date | — |
| Expiry date | Aug 14, 2011 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC30B15/30
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A Czocharalski method for producing silicon rods wherein a single crystal silicon rod is pulled from a silicon melt contained in a coaxial crucible. In the method, the rod and crucible are rotated in opposite directions about their axes, the rotation rate of the rod being greater than the rotation rate of the crucible as the rod is grown. The rotation rate of the crucible is increased as the length of the rod increases. A magnetic field that is substantially rotationally symmetrical about the axis of the rod is imposed upon the silicon melt until a fraction of the silicon melt is solidified, the magnetic field having components which perpendicularly intersect the bottom and side walls of the crucible and a component which perpendicularly intersects the surface of the silicon melt. The average magnetic component which perpendicularly intersects the molten silicon surface is about zero, and the intensity of the magnetic field component which perpendicularly intersects the bottom and side walls of the crucible is decreased as the fraction of silicon melt solidified increases.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.