Pumpdown base pressure

These sources of gases and vapors determine the lowest pressure (base pressure) that can be reached in a given time (pumpdown time), the gas/vapor (contaminant) species in the system at any time, and how fast the chamber pressure rises after the pumping is stopped i.e., the leakup rate or leak-back rate . Figure 3.6 shows a typical pumpdown curve with fast, slow, and very slow leakup rates after the pumping system has been isolated. 

Base pressure (vacuum technology) The specified pressure at which the system begins the next sequence in processing. See also Pumpdown time Ultimate pressure. 

Duty cycle (process) The ratio of the time of the processing sequence, such as pumpdown to a base pressure in the total process cycle time or actual sputtering time per voltage cycle in pulse power sputtering, to the process cycle time of interest. 

Pumpdown time The time for a vacuum system to reach a specified pressure such as the Base pressure. 

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