The emitter diffusion process is performed in a variety of ways. In this case a phosphorous containing coating is applied to the surface. The wafers are then put in a belt furnace to diffuse a small amount of phosphorous into the silicon surface.
Loading the phosphorous coating. The trend in production lines is to have as much automation as possible and to move the wafers through the lines on a belt. The loading and unloading of cassettes is a major source of yield loss.
Wafers moving from the diffusion coating furnace to the high temperature diffusion furnace. The diffusion coating is clear so the wafer do not look markedly different from the previous video
The wafers travel through the diffusion furnace for roughly an hour.
Finally the wafers are loaded into a centrifuge for a final rinse and spin dry.
After the diffusion process the wafers are loaded back into casettes for an acid etch to remove the diffusion glass.