High throughput chemical vapor deposition electrode
Processes and systems to fabricate high throughput, low cost tubular polysilicon feed rods, which can be used as direct feedstock to grow a crystalline silicon material, are disclosed. In an example, a chemical vapor deposition (CVD) process includes depositing polysilicon on a tubular electrode to form a tubular polysilicon feed rod. The tubular polysilicon feed rod may be melted in a float zone process to grow the single-crystalline silicon material.
1. An electrode for chemical vapor deposition of polysilicon, comprising:
a core tube having a conductive wall around a lumen, wherein the lumen extends between a first end and a second end of the core tube to carry a liquid cooling agent through the electrode; and
a barrier film around the conductive wall, wherein the barrier film includes a metal diffusion barrier material, and wherein the barrier film has an undulating outer surface while the lumen is linear and is circular from a cross-sectional view.
2. The electrode of claim 1 , wherein the barrier film includes an inner barrier film layer covering the conductive wall, and an outer barrier film layer covering the inner barrier film layer.
3. The electrode of claim 2 , wherein the inner barrier film layer includes the metal diffusion barrier material, and wherein the outer barrier film layer includes a second metal diffusion barrier material.
4. The electrode of claim 3 , wherein the metal diffusion barrier material includes a first coefficient of thermal expansion, wherein the second metal diffusion barrier material includes a second coefficient of thermal expansion, and wherein the first coefficient of thermal expansion is different than the second coefficient of thermal expansion by less than 20%.
5. The electrode of claim 3 further comprising an intermediate barrier film layer between the inner barrier film layer and the outer barrier film layer, wherein the metal diffusion barrier material includes a first coefficient of thermal expansion, wherein the second metal diffusion barrier material includes a second coefficient of thermal expansion, and wherein the first coefficient of thermal expansion is different than the second coefficient of thermal expansion by more than 20%.
6. An electrode for chemical vapor deposition of polysilicon, comprising:
a core tube having a conductive wall around a lumen, wherein the lumen extends between a first end and a second end of the core tube to carry a liquid cooling agent through the electrode; and
a barrier film around the conductive wall, wherein the barrier film includes an undulating outer surface while the lumen is linear and is circular from a cross-sectional view.
7. The electrode of claim 6 , wherein the core tube includes a fin extending radially outward from a central axis of the lumen, and wherein the fin includes a peak between a plurality of valleys, the peak having a respective radial separation from the central axis greater than respective radial separations of the valleys from the central axis.
8. The electrode of claim 7 , wherein the undulating outer surface extends over the fin in a peripheral direction around the central axis and includes a curvilinear cross-sectional outer edge.
9. The electrode of claim 7 , wherein the undulating outer surface extends over the fin in a peripheral direction around the central axis and includes a rectilinear cross-sectional outer edge.
10. The electrode of claim 7 , wherein the radial separation between the peak and the central axis varies between the first end and the second end of the core tube such that the electrode includes an axial undulation.
11. The electrode of claim 7 , wherein the fin extends helically around the central axis between the first end and the second end of the core tube such that the electrode includes a thread.