Phosphorous Diffusion is widely used in the manufacture of solar cells. Silicon wafers are doped with small amounts of phosphorous to create the n-junction of the solar cell. This process is accomplished by depositing phosphorous vapor or coating on top of a silicon substrate. It is then fired at temperatures between 800°C and 1000°C to drive the phosphorous into the silicon, thus, creating the n-junction.
This application is typically processed in either a batch tube furnace or an in-line continuous furnace. The in-line approach offers far greater throughput opportunity than the batch process, as well as superior uniformity, lower wafer breakage and shorter process times. Detailed Cost of Ownership models have shown that in-line diffusion can deliver per wafer costs of as low as one third the cost of a batch diffusion furnace.
BTU’s integrated Meridian™ In-Line Diffusion System combines a quartz lined diffusion furnace with a dual-sided phosphorous coater and wafer dryer. The Meridian™ can be configured to process up to 1,500 wafers per hour. Excellent thermal uniformity of ± 2°C or better produces very predictable and repeatable sheet resistance values, configurable from 40 to 100 ohms/sq and higher. This range covers not only the requirements of today’s cell designs but also the shallow emitters needed for next generation solar cell designs, including selective emitter cells. Quartz lining insures tight atmosphere control required to maintain proper phosphorus drive-in. The Meridian™ phosphorus coater features highly reliable nozzle-less spray technology.