DIFFUSION FURNACES EMPLOYING ULTRA LOW MASS TRANSPORT SYSTEMS AND METHODS OF WAFER RAPID DIFFUSION PROCESSING

摘要

Multi-zone, solar cell diffusion furnaces having a plurality of radiant element (SiC) or/and high intensity IR lamp heated process zones, including baffle, ramp-up, firing, soaking and cooling zone(s). The transport of solar cell wafers, e.g., silicon, selenium, germanium or gallium-based solar cell wafers, through the furnace is implemented by use of an ultra low-mass, wafer transport system comprising laterally spaced shielded metal bands or chains carrying non-rotating alumina tubes suspended on wires between them. The wafers rest on raised circumferential standoffs spaced laterally along the alumina tubes, which reduces contamination. The bands or chains are driven synchronously at ultra-low tension by a pin drive roller or sprocket at either the inlet or outlet end of the furnace, with appropriate tensioning systems disposed in the return path. The high intensity IR flux rapidly photo-radiation conditions the wafers so that diffusion occurs 3X faster than conventional high-mass thermal furnaces. Fig. 8