Abstract: An evacuation system for removing corrosive gas from a process tube during processing of semiconductor wafers. An aspirator is used for an initial pump down of the process tube to approximately 200 TORR. The aspirator has no moving parts and does not react to the corrosive gas. The aspirator is controlled by a control circuit which utilizes a series of relays to open a ball valve and start the aspirator. After 200 TORR is reached, the aspirator is shut off, the ball valve is closed and a high vacuum pump is utilized to complete the evacuation. Because the vacuum pump is exposed to a reduced volume of corrosive gas, its lifetime is correspondingly increased.