Method for growing a silicon crystal substrate from a melt by directing a flow of molten silicon around a baffle structure
View Patent ↗An apparatus for growing a silicon crystal substrate comprising a heat source, an anisotropic thermal load leveling component, a crucible, and a cold plate component is disclosed. The anisotropic thermal load leveling component possesses a high thermal conductivity and may be positioned atop the heat source to be operative to even-out temperature and heat flux variations emanating from the heat source. The crucible may be operative to contain molten silicon in which the top surface of the molten silicon may be defined as a growth interface. The crucible may be substantially surrounded by the anisotropic thermal load leveling component. The cold plate component may be positioned above the crucible to be operative with the anisotropic thermal load leveling component and heat source to maintain a uniform heat flux at the growth surface of the molten silicon.
1. A method of growing a silicon crystal substrate comprising:
filling a crucible with molten silicon in which a portion of the top surface of the molten silicon defines a growth surface;
heating the crucible using a heat source;
regulating the heat from the heat source incident on a surface of the crucible via a passive thermal load leveling anisotropic material disposed between the heat source and the crucible;
maintaining a uniform heat flux at the growth surface of the molten silicon by cooling an area above the growth surface; and
with a pump disposed within the crucible, directing a flow of the molten silicon around a baffle structure extending from an interior wall of the crucible and submerged within the molten silicon, wherein the flow is directed over and along a top surface of the baffle structure in a first direction and under and along a bottom surface of the baffle structure in a second direction opposite the first direction.
2. The method of claim 1 further comprising pulling the growing silicon crystal substrate at a constant pull rate away from the crucible.
3. The method of claim 2 further comprising:
measuring a thickness of the silicon crystal substrate; and
determining if the measured thickness of the silicon substrate is within acceptable tolerance values.
4. The method of claim 3 further comprising modifying an amount of heat from the heat source incident on the surface of the crucible if the measured thickness of the silicon substrate is not within the acceptable tolerance values.
5. The method of claim 3 further comprising modifying a rate of cooling the area above the growth surface if the measured thickness of the silicon substrate is not within the acceptable tolerance values.
6. The method of claim 3 further comprising modifying the pull rate away from the crucible if the measured thickness of the silicon substrate is not within the acceptable tolerance values.
7. The method of claim 3 further comprising modifying the filling of the crucible with an amount of molten silicon if the measured thickness of the silicon substrate is not within the acceptable tolerance values.
8. The method of claim 1 further comprising pumping the molten silicon about a baffle structure positioned within the crucible.
9. The method of claim 1 wherein the passive thermal load leveling anisotropic material is comprised of pyrolytic graphite.