Gas laser apparatus for lithography

Abstract

The present invention relates to a long pulse gas laser apparatus for lithography further improved in the laser oscillation efficiency and stability increased by addition of xenon gas. A gas laser apparatus for lithography has a pair of discharge electrodes 2 provided in a laser chamber 1 and emits laser beam having a laser pulse width (T is ) of not less than 40 ns by exciting a laser gas sealed in the laser chamber 1 by electric discharge between the pair of discharge electrodes 2, the laser gas containing xenon in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio. The laser gas has been heated at least when the laser beam is emitted.

What we claim is:  
     
         1 . A gas laser apparatus for lithography having a pair of discharge electrodes for excitation provided in a laser chamber having a laser gas sealed therein and emitting laser beam having a laser pulse width (T is ) of not less than 40 ns, 
 wherein a temperature of the laser gas before addition of xenon is not less than 35° C., and xenon is added to the laser gas at not less than 35° C. in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio.    
     
     
         2 . A gas laser apparatus for lithography according to  claim 1 , wherein the temperature of the laser gas before addition of xenon is not less than 40° C., and xenon is added to the laser gas in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio.  
     
     
         3 . A gas laser apparatus for lithography according to  claim 1 , wherein the temperature of the laser gas before addition of xenon is not less than 45° C., and xenon is added to the laser gas in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio.  
     
     
         4 . A gas laser apparatus for lithography having a pair of discharge electrodes for excitation provided in a laser chamber having a laser gas sealed therein and emitting laser beam having a laser pulse width (T is ) of not less than 40 ns, 
 wherein a temperature of the laser chamber is raised to not less than 35° C. by heating, and thereafter, a laser gas containing xenon in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio is sealed in the laser chamber.    
     
     
         5 . A gas laser apparatus for lithography according to  claim 4 , wherein the temperature of the laser chamber is raised to not less than 40° C. by heating.  
     
     
         6 . A gas laser apparatus for lithography according to  claim 4 , wherein the temperature of the laser chamber is raised to not less than 45° C. by heating.  
     
     
         7 . A gas laser apparatus for lithography having a pair of discharge electrodes for excitation provided in a laser chamber having a laser gas sealed therein and emitting laser beam having a laser pulse width (T is ) of not less than 40 ns, 
 wherein xenon is added to said laser gas in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio, and a temperature of the laser gas after addition of the xenon is not less than 35° C.    
     
     
         8 . A gas laser apparatus for lithography according to  claim 7 , wherein the temperature of the laser gas after addition of the xenon is not less than 40° C.  
     
     
         9 . A gas laser apparatus for lithography according to  claim 7 , wherein the temperature of the laser gas after addition of the xenon is not less than 45° C.  
     
     
         10 . A gas laser apparatus for lithography having a pair of discharge electrodes provided in a laser chamber and emitting laser beam having a laser pulse width (T is ) of not less than 40 ns by exciting a laser gas sealed in said laser chamber by electric discharge between said pair of discharge electrodes, said laser gas containing xenon in an amount not less than 2 ppm and not more than 100 ppm in partial pressure ratio, 
 wherein said laser gas has been heated at least when said laser beam is emitted.    
     
     
         11 . A gas laser apparatus for lithography according to  claim 10 , further having preionization means for preionizing said laser gas.  
     
     
         12 . A gas laser apparatus for lithography according to  claim 10  or  11 , wherein said laser gas has been heated to not less than 35° C. when said laser beam is emitted.  
     
     
         13 . A gas laser apparatus for lithography according to  claim 10  or  11 , wherein said laser gas has been heated to not less than 40° C. when said laser beam is emitted.  
     
     
         14 . A gas laser apparatus for lithography according to  claim 10  or  11 , wherein said laser gas has been heated to not less than 45° C. when said laser beam is emitted.  
     
     
         15 . A gas laser apparatus for lithography according to any one of  claims 1  to  14 , which is arranged to perform a laser oscillating operation by a first half-cycle of a discharge oscillating current waveform of one pulse in which a polarity is reversed, together with at least two half-cycles subsequent to the first half-cycle.  
     
     
         16 . A gas laser apparatus for lithography according to any one of  claims 1  to  15 , which is on e selected from a KrF excimer laser apparatus, an ArF excimer laser apparatus, and a fluorine laser apparatus.