Device for generating gas curtain for deflecting contaminating substances in extreme UV-mask metrological system, has nozzle with nozzle section, where pressure of supersonic-gas flow is not larger than specific percent of ambient pressure

摘要

The device (20) has a gas nozzle (22) comprising a nozzle opening (22a) for discharging gas flow for generating a gas curtain (21). The gas nozzle generates a subsonic-gas flow (23a). The gas nozzle has a nozzle section with a flow cross-section extended towards the nozzle opening for generating supersonic-gas flow, where static pressure of the supersonic-gas flow is not larger than 50 percent of ambient pressure during discharging of the gas flow from the nozzle opening. The nozzle opening ends into a tube-shaped housing (25), and a collecting opening (24a) is formed at a wall area (25b). The gas flow contains gas e.g. hydrogen, helium, nitrogen, argon, neon, krypton, xenon or oxygen. Independent claims are also included for the following: (1) a gas nozzle for generating supersonic-gas flow (2) an extreme UV-lithographic system.