Shutoff-opening device

A shutoff-opening device in a gas supply section of semiconductor manufacturing equipment, comprising:

• a first on-off valve, which supplies a process gas, disposed on a front end of the shutoff-opening device;
• a second on-off valve, which supplies a purge gas, adjacent to a rear side of the first on-off valve;
• and
• a passage block supporting the first on-off valve and the second on-off valve on a top surface of the passage block, wherein
• each of the first on-off valve and the second on-off valve is a two-port valve, and
• the passage block is provided with:
• a first on-off valve-corresponding inflow passage which is directly open to an exterior of the passage block via a first on-off valve-corresponding communicating passage, through which the process gas flows,
• a first on-off valve-corresponding outflow passage which is directly open to the exterior of the passage block,
• a second on-off valve-corresponding inflow passage which is directly open to the exterior of the passage block, and
• a second on-off valve-corresponding outflow passage directly connected to a communicating passage,
• the second on-off valve-corresponding outflow passage is in communication with the first on-off valve-corresponding outflow passage directly via a the communicating passage formed in the passage block without passing through an inside of the first on-off valve, and
• an orifice gasket having a through hole diameter which is smaller than a diameter of the second on-off valve-corresponding outflow passage and a diameter of the communicating passage, the orifice gasket forming a throttling portion connected between the second on-off valve-corresponding outflow passage and the communicating passage, to prevent backflow from the communicating passage to the second on-off valve-corresponding outflow passage.