Patent ID: 8469650

Claim:
A method of controlling pressure in a wafer transfer system, the method comprising: maintaining a housing of the wafer transfer system under a first pressure; sensing whether a wafer container is present on a loadport, which is operably connected to the housing; varying an interior pressure condition of the housing from the first pressure to a second pressure, when the wafer container is sensed on the loadport, by operating a variable exhaust unit in the housing to move from a first position providing a relatively low rate of exhaust to a second position providing a relatively high rate of exhaust, and increasing a speed of a variable speed fan in the housing from a first speed to a second speed, the variable exhaust unit and the variable speed fan facing each other; sensing whether the wafer container is removed from the loadport; and returning the housing to the first pressure, when the wafer container is removed from the loadport, by operating the variable exhaust unit to move from the second position to the first position and decreasing the speed of the variable speed fan from the second speed to the first speed, wherein the first pressure and the second pressure are greater than a pressure in a clean room surrounding the housing.