Method and apparatus for wavelength calibration

A method for calibrating the absolute wavelength of spectral emission of a narrow emission ArF-excimer laser system including a wavelength calibration system including a wavelength calibration module filled with a gas having a plurality of optical inter-level transitions within the broadband emission spectrum of said excimer laser, comprising the steps of:

• providing a narrowed band output laser beam from said ArF-excimer laser system around 193 nm;
• controlling the laser system with a microprocessor unit;
• directing said output beam through the gas filling the wavelength calibration module;
• tuning the narrowed emission within the broadband emission spectrum;
• detecting the plurality of inter-level transitions of the gas when the narrowed emission is tuned within the broadband emission spectrum;
• and
• calibratign the absolute wavelength of the narrowed emission.

A wavelength calibration system for measuring an absolute wavelength of a narrowed spectral emission of an excimer or molecular fluorine laser including a discharge chamber and a resonator, comprising:

• a gas-filled module;
• means for controlling the laser;
• means for generating said narrowed spectral emission having a bandwidth of less than 1 pm;
• means for directing said narrowed emission through said module;
• means for wavelength running said narrowed emission with a broadband excimer laser emission spectrum;
• means for detecting a plurality of lines of optical absorption of said narrowed emission by the gas within the module, when said narrowed emission is directed through said module and tuned within said broadband spectrum;
• and
• means for calibrating the absolute wavelength of said narrowed emission.

A narrow band excimer laser system including an excimer laser chamber and optical resonator, a spectral narrowing and tuning unit that produces a narrowed spectral emission having a bandwidth of less than 1 pm within a range of a broadband emission spectrum of said laser, a microprocessor unit for controlling the laser system, and a detection and control unit for relative wavelength detection, control and tuning, the improvement comprising:

• providing a gas-filled module containing a photoabsorbing gas having a plurality of absorption lines within the broadband emission spectrum of said excimer laser, wherein the gas-filled module contains a species selected from The group consisting of arsenic carbon, germanium, iron, hydrocarbons, halogenized hydrocarbons, carbon-contaminate inert gases, oxygen and platinum
• detecting said plurality of absorption lines for wavelength calibration and tuning of said narrowed emission within said broadband spectrum;
• and
• calibrating the absolute wavelength of the narrowed emission.

A method for determining the absolute wavelength of spectral emission of a narrow band excimer or molecular fluorine laser system including a wavelength calibration system including a gas-filled module having a photoabsorbing, medium therein, said photoabsorbing medium having a plurality of optical absorption lines within the broadband emission spectrum of said laser system, comprising the steps of:

• providing a narrow band output laser beam from said laser system having a bandwidth of less than 1 pm;
• directing said output beam through the photo-absorbing medium of the gas-filled module;
• detecting the plurality of optical absorption lines when the narrowed emission is tuned within the broadband emission spectrum;
• and
• calibrating The absolute wavelength of the narrow emission.

An excimer laser system generating a narrow band output beam of a known wavelength and having a bandwidth of less than 1 pm comprising:

• an optical element for tuning the wavelength of the narrow band output bean having a bandwidth of less than 1 pm the laser;
• a resonator;
• a module filled with a gas having multiple optical transition lines for optically interacting with a portion of the beam in a narrow band within a broadband emission spectrum of said excimer laser;
• a detection unit for measuring the effects of the interaction of the multiple lines of the gas with the beam portion as the wavelength of the narrow band output beam is scanned;
• and
• a processor for calibrating the wavelength of the narrow band output beam based on the measured effects of the interaction of the multiple lines of the gas with the output beam.

A method for calibrating the absolute wavelength of spectral emission of a narrow emission laser including a wavelength calibration unit filled with a gas having a plurality of optical inter-level transitions within the emission spectrum of said laser, comprising the steps of:

• providing a narrowed band output laser beam from said laser having a bandwidth of less than 1 pm;
• directing said output beam through the gas filling the wavelength calibration unit;
• scanning the narrowed emission within the emission spectrum of the laser;
• detecting the plurality of optical inter-level transitions of the gas when the narrowed emission is scanned within the emission spectrum of the laser;
• and
• calibrating the absolute wavelength of the narrowed emission based on the detected inter-level transitions.

A method for determining the absolute wavelength of a narrowed spectral emission of a narrow band laser system including a wavelength calibration system including a module filled with a medium including a photoabsorbing gas having a plurality of optical absorption lines within the emission spectrum of said laser, comprising the steps of:

• providing a narrow band output laser beam from said laser system;
• controlling the laser system with a microprocessor unit
• directing said output bean through said medium including said photoabsorbing gas;
• detecting the plurality of optical absorption lines when the narrowed emission is tuned within the emission spectrum of the laser;
• and
• calibrating the absolute wavelength of the narrowed emission.