Method and Apparatus for Generating Illuminating Radiation

A method for generating an illuminating radiation beam in a higher harmonic generation radiation source, comprising:

• providing a driving radiation beam, the radiation beam comprising a plurality of radiation pulses, for generating the illuminating radiation beam;
• splitting the driving radiation beam into first plurality of driving radiation pulses and a second plurality of driving radiation pulses;
• controlling a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation beam;
• and
• controlling a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation beam.

A method for an inspection apparatus, comprising:

• providing a first plurality of driving radiation pulses;
• providing a second plurality of driving radiation pulses;
• combining the first and second plurality of output pulses into an illuminating radiation beam;
• and
• using the illuminating radiation beam to determine at least one characteristic of a target:
• wherein the providing the first plurality of radiation pulses comprises controlling a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation;
• and
• wherein the providing a second plurality of radiation pulses comprises controlling a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation.

A method of manufacturing devices, comprising:

• forming device features and metrology targets on a series of substrates by a lithographic process;
• measuring properties of the metrology targets on one or more processed substrates by a method comprising:
• providing a first plurality of driving radiation pulses;
• providing a second plurality of driving radiation pulses;
• combining the first and second plurality of output pulses into an illuminating radiation beam;
• and
• using the illuminating radiation beam to determine at least one characteristic of the metrology targets, wherein:
• the providing the first plurality of radiation pulses comprises controlling a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation;
• and
• the providing a second plurality of radiation pulses comprises controlling a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation
• wherein the measured properties are used to adjust parameters of the lithographic process for the processing of further substrates.

A computer program product comprising machine-readable instructions for causing a processor to perform operations comprising:

• providing a driving radiation beam, the radiation beam comprising a plurality of radiation pulses, for generating the illuminating radiation beam;
• splitting the driving radiation beam into first plurality of driving radiation pulses and a second plurality of driving radiation pulses;
• controlling a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation beam;
• and
• controlling a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation beam.

A computer program product comprising machine-readable instructions for causing a processor to perform operations comprising:

• providing a first plurality of driving radiation pulses;
• providing a second plurality of driving radiation pulses;
• combining the first and second plurality of output pulses into an illuminating radiation beam;
• and
• using the illuminating radiation beam to determine at least one characteristic of a target;
• wherein the providing the first plurality of radiation pulses comprises controlling a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation;
• and
• wherein the providing a second plurality of radiation pulses comprises controlling a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation.

A lithographic system comprising:

• an illumination optical system arranged to illuminate a pattern;
• a projection optical system arranged to project an image of the pattern onto a substrate;
• and
• an inspection apparatus configured to:
• provide a driving radiation beam, the radiation beam comprising a plurality of radiation pulses, for generating the illuminating radiation beam;
• split the driving radiation beam into first plurality of driving radiation pulses and a second plurality of driving radiation pulses;
• control a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation beam;
• and
• control a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation beam;
• wherein the lithographic system is arranged to use one or more parameters calculated by the inspection apparatus in applying the pattern to further substrates.

A lithographic system comprising:

• an illumination optical system arranged to illuminate a pattern;
• a projection optical system arranged to project an image of the pattern onto a substrate;
• and
• an inspection apparatus configured to:
• provide a first plurality of driving radiation pulses;
• provide a second plurality of driving radiation pulses;
• combine the first and second plurality of output pulses into an illuminating radiation beam;
• and
• use the illuminating radiation beam to determine at least one characteristic of a target:
• wherein the providing the first plurality of radiation pulses comprises controlling a first controllable characteristic of the first plurality of radiation pulses to control a first portion of an output wavelength spectrum of the illuminating radiation;
• and
• wherein the providing a second plurality of radiation pulses comprises controlling a second controllable characteristic of the second plurality of radiation pulses to control a second portion of the output wavelength spectrum of the illuminating radiation.