Gaseous extreme-ultraviolet spectral purity filters and optical systems comprising same

An EUV optical system, comprising:

• an optical system situated and configured to receive a beam of EUV light from a source;
• and
• a gaseous spectral-purity filter (SPF) situated between the source and the optical system, or within the optical system, such that the beam passes through the SPF as the beam propagates from the source through the optical system, the gaseous SPF serving to enrich the beam, downstream of the SPF compared to upstream of the SPF, in a desired EUV wavelength as the beam passes through the gaseous SPF;
• the gaseous SPF comprising a first gas-discharge means, a stream of SPF gas discharged from the first gas-discharge means, a second gas-discharge means situated relative to the first gas-discharge means, and a stream of sheath gas discharged from the second gas-discharge means so as to envelop the stream of SPF gas.

An EUV optical system, comprising:

• an optical system situated and configured to receive a beam of EUV light from a source;
• and
• a first spectral-purity filter (SPF) situated between the source and the optical system, or within the optical system, the first SPF being a gaseous SPF;
• and
• a second SPF situated downstream of the first SPF,
• wherein the beam passes through the first and second SPFs as the beam propagates from the source through the optical system, the first and second SPFs serving to enrich the beam, downstream of the SPEs compared to upstream of the SPFs, in a desired EUV wavelength as the beam passes through the first and second SPFs.

A gaseous spectral-purity-filter (SPF) apparatus for placement between an EUV source and an optical element, the apparatus comprising:

• a gas-discharge portion situated and configured to release a stream of SPF gas into a propagation pathway of a beam of EUV light from the EUV source, such that the beam from the EUV source passes through the stream of SPF gas to the optical element, the SPF gas being transmissive for a desired wavelength of EUV light in the beam while blocking at least some other wavelengths in the beam;
• and
• a gas-collection portion situated relative to the gas-discharge portion and configured to collect the SPF gas from the stream after the beam has passed through the stream of SPF gas;
• the gas-discharge portion comprising a nozzle assembly from which the stream of SPF gas is discharged, and the nozzle assembly comprising an SPF-gas-discharge nozzle and a sheath-gas-discharge nozzle, the sheath-gas-discharge nozzle being configured to release a stream of sheath gas as the SPF-gas-discharge nozzle releases the stream of SPF gas.

An illumination-optical system for EUV lithography, comprising:

• an EUV source situated and configured to produce a beam of EUV-containing light;
• a first EUV-reflective optical element situated downstream of the EUV source;
• and
• a gaseous spectral-purity filter (SPF) situated between the EUV source and the first EUV-reflective optical element, the gaseous SPF being configured to produce a stream of SPF gas through which the beam from the EUV source passes as the beam propagates to the first EUV-reflective optical element, the gaseous SPF being formulated and configured to enrich the beam in at least one desired EUV wavelength as the beam passes through the SPF.

An EUV lithography system, comprising:

• an illumination-optical system situated and configured to receive a beam of EUV light from a source and to direct the beam for lithographic imaging;
• and
• a gaseous spectral-purity filter (SPF) situated between the source and the illumination-optical system or within the illumination-optical system, the gaseous SPF being configured to produce a stream of SPF gas through which the beam passes and being formulated and configured to enrich the beam in at least one desired EUV wavelength as the beam passes through the SPF;
• the gaseous SPF comprising a first gas-discharge device and a stream of SPF gas discharged from the first gas-discharge device, the stream of SPF gas comprising ZrCl4 gas, B5H11 gas, or a mixture thereof;
• and
• the gaseous SPF further comprising a second gas-discharge device situated relative to the first gas-discharge device and a stream of sheath gas discharged from the second gas-discharge device so as to envelop the stream of SPF gas.

A source of EUV light, comprising:

• a generating device that generates EUV-containing light;
• and
• a gaseous spectral-purity filter (SPF) situated downstream of the generating device, the gaseous SPF being configured to produce a stream of SPF gas through which the EUV-containing light passes as the EUV-containing light propagates downstream of the generating device, the gaseous SPF being formulated and configured to enrich the EUV-containing light in at least one desired EUV wavelength as said light passes through the SPF;
• the gaseous SPF comprising a first gas-discharge device and a stream of SPF gas discharged from the first gas-discharge device, the stream of SPF gas comprising ZrCl4 gas, B5H11 gas, or a mixture thereof;
• and
• the gaseous SPF further comprising a second gas-discharge device situated relative to the first gas-discharge device, and a stream of sheath gas discharged from the second gas-discharge device so as to envelop the stream of SPF gas.

A method for producing a beam of EUV light that is enriched with respect to a desired wavelength of EUV radiation, comprising:

• producing a beam of electromagnetic radiation comprising EUV light;
• discharging a stream of spectral-purity-filter (SPF) gas and a stream of sheath gas enveloping the stream of SPF gas, the SPF gas being transmissive to a desired wavelength of EUV radiation and non-transmissive to an undesired wavelength of electromagnetic radiation, the stream of SPF gas comprising ZrCl4 gas, B5H11 gas, or a mixture thereof;
• and
• passing the beam through the enveloped stream of SPF gas.