Hot-Wall, Parallel-Plate PECVD Reactors

The two reactors just described are parallel plate reactors. However, they are also cold wall reactors. In other words, the electrode holding the wafers is hot, but all other surfaces exposed to the plasma are cold, or at least not heated. This is done to minimize the deposition on other surfaces so that down time for cleaning can be kept as short as possible. 

Multiple reactangular electrodes are arranged so that they fit down the length of a tube and are alternately powered by a 400-kHz power supply. The electrodes are fabricated of graphite. A major attraction of the hot wall system is the large wafer load that can be run (i.e., 84 4-inch wafers) at onetime. This is offset to some extent by the fact that the electrode structure cools off each time wafers are unloaded, and the time needed to reheat upon insertion into the furnace detracts from wafer throughput. 

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