Method and system for controlling narrow-band oscillation excimer laser

A system for controlling a narrow-band oscillation excimer laser, comprising:

• a laser chamber filled with a laser gas;
• electrodes disposed within said laser chamber for exciting the laser gas within said laser chamber;
• at least two wavelength selective elements disposed in an optical path passing through said laser chamber in series therewith and having respectively controllable selection frequency bands;
• center-wavelength control means for controlling the selection frequency bands of said at least two wavelength selective elements to set a center wavelength of an output laser beam of said laser at a desired value;
• overlapping means for controllably overlapping the selection frequency bands of said at least two wavelength selective elements to set a power of said output laser beam at its maximum;
• power control means for controlling a voltage to be applied to said electrodes to set the power of said output laser beam to be substantially constant;
• detection means for detecting when the voltage to be applied to said electrodes exceeds a predetermined value and providing a detection output;
• partial gas replacement means for performing partial gas replacement over the laser gas within said laser chamber according to the detection output of said detection means;
• first mode setting means for setting a first control mode to set a control period of said power control means to be longer than a control period of said overlapping control means;
• second mode setting means for setting a second control mode to set the control period of said power control means to be substantially equal to the control period of said overlapping control means;
• and
• control means for controlling said center-wavelength control means, overlapping means and power control means in the second mode set by said second mode setting means at least for a predetermined time after said partial gas replacement means causes start of the partial gas replacement, and thereafter for controlling said center-wavelength control means, overlapping means and power control means in the first mode set by said first mode setting means.

A system for controlling a narrow-band oscillation excimer laser comprising:

• a laser chamber filled with a laser gas;
• electrodes disposed within said laser chamber for exciting the laser gas within said laser chamber;
• at least two wavelength selective elements disposed in an optical path passing through said laser chamber in series there with and having respectively controllable selection frequency bands;
• center-wavelength control means for controlling the selection frequency bands of said at least two wavelength selective elements to set a center wavelength of an output laser beam of said laser at a desired value;
• overlapping means for controllably overlapping the selection frequency bands of said at least two wavelength selective elements to set a power of said output laser beam at its maximum;
• power control means for controlling a voltage to be applied to said electrodes to set the power of said output laser beam to be substantially constant;
• detection means for detecting when the voltage to be applied to said electrodes exceeds a predetermined value;
• partial gas replacement means for performing partial gas replacement over the laser gas within said laser chamber according to the detection output of said detection means;
• first mode setting means for setting a first control mode to set a control period of said power control means to be longer than a control period of said overlapping control means;
• second mode setting means for setting a second control mode to inhibit overlapping control of said overlapping control means during execution of power control by aid power control means;
• and
• control means for controlling said center-wavelength control means, overlapping means and power control means in the second mode set by said second mode setting means at least for a predetermined time after said partial gas replacement means causes start of the partial gas replacement, and thereafter for controlling said center-wavelength control means, overlapping means and power control means in the first mode set by said first mode setting means.

A method for controlling a narrow-band oscillation excimer laser including:

• a laser chamber filled with a laser gas;
• at least two wavelength selective elements disposed in an optical path passing through said laser chamber in series with said optical path and having respectively controllable selection frequency bands;
• center-wavelength control means for controlling the selection frequency bands of said at least two wavelength selective elements to set a center wavelength of an output laser beam of said laser at a desired value;
• and
• overlapping means for controllably overlapping the selection frequency bands of said at least two wavelength selective elements to set a power of said output laser beam at its maximum level;
• said method comprising the steps of:
• carrying out overlapping control with said overlapping means only at the time of starting said narrow-band oscillation excimer laser;
• and
• carrying out center wavelength control with said center-wavelength control means after completion of said overlapping control.

A system for controlling a narrow-band oscillation excimer laser comprising:

• a laser chamber filled with a laser gas;
• at least two wavelength selective elements disposed in an optical path passing through said laser chamber in series with said optical path and having respectively controllable selection frequency bands;
• center-wavelength control means for controlling the selection frequency bands of said at least two wavelength selective elements to set a center wavelength of an output laser beam of said laser at a desired value;
• overlapping means for controllably overlapping the selection frequency bands of said at least two wavelengths selective elements to set a power of said output laser beam at its maximum level;
• and
• control means for controlling the overlapping control based on said overlapping means to be carried out only at the time of starting said excimer laser and for controlling the carrying out of center wavelength control based on said center-wavelength control means after completion of said overlapping control.