| 摘要 |
A valve body is provided with a gas feed passage having an inlet and an outlet, a tank chamber, and a branch passage having a first portion connected between the gas feed passage and the tank chamber and an outlet extending from the tank chamber to a side of the valve body. A first valve is mounted on the valve body and selectively opens and closes the gas feed passage at a point downstream of the junction of the branch passage with the gas feed passage. A second valve is mounted on the valve body and selectively opens and closes the branch passage at a point between the tank chamber and the junction of the branch passage and the gas feed passage. A vacuum pump is provided to evacuate the tank chamber. When the first valve is open and the second valve is closed, gas may flow from an inlet pipe, through the gas feed passage and the first valve to a semiconductor process chamber. When the first valve is closed and the second valve is opened, residual gas in piping upstream of the inlet is evacuated through the branch passage and the second valve by the vacuum in the tank chamber. The first valve isolates the process chamber while the residual gas is being evacuated from the upstream piping.
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