Pulse-width extending optical systems, projection-exposure apparatus comprising same, and manufacturing methods using same

Abstract

This invention pertains to systems for extending the pulse length of pulsed sources of optical radiation. These systems reduce peak optical pulse power without reducing average optical power. The pulse-width extending systems split optical pulses into pulse portions, introduce relative delays among the pulse portions, and then redirect the pulse portions (or portions thereof) along a common axis. Such pulse-width extending systems are especially useful in projection-exposure apparatus for the manufacture of semiconductor devices where short wavelength, high power optical sources tend to damage optical components.

What is claimed is:  
     
         1 . A light source apparatus comprising: 
 a light source unit supplying a light pulse having a wavelength not more than 193 nm; and    a pulse-width extending optical system arranged in an optical path of the light pulse supplied from the light source unit, which extends a duration of the light pulse supplied from the light source unit while decreasing a peak power of the light pulse, the pulse-width extending optical system including an optical surface having a multi-layer coating to divide the light pulse into at least two light pulses.    
     
     
         2 . A light source apparatus according to  claim 1 , wherein the pulse-width extending optical system comprises a beam dividing member to divide the light pulse into multiple pulse portions, and a beam deflecting system disposed to direct at least one of the pulse portions to the beam dividing member, 
 wherein the beam dividing member includes the optical surface having the multi-layer coating.    
     
     
         3 . A light source apparatus according to  claim 2 , wherein the beam deflecting system comprises a relay optical system to form an image of the optical surface on the optical surface.  
     
     
         4 . A light source apparatus according to  claim 2 , wherein the beam deflecting system comprises a relay optical system disposed to produce a magnification of about +1 or −1.  
     
     
         5 . A light source apparatus according to  claim 1 , wherein the pulse-width extending optical system comprises a relay optical system to form an image of the optical surface on the optical surface.  
     
     
         6 . A light source apparatus according to  claim 1 , wherein the pulse-width extending optical system comprises a relay optical system disposed to produce a magnification of about +1 or −1.  
     
     
         7 . A light source apparatus according to  claim 1 , wherein the light source unit comprises an excimer laser source.  
     
     
         8 . A light source apparatus according to  claim 1 , wherein the pulse-width extending optical system provides a pulse length of at least 3 m with respect to the divided pulse portions.  
     
     
         9 . A light source apparatus comprising: 
 a light source unit supplying a light pulse having a wavelength not more than 193 nm; and    a pulse-width extending optical system arranged in an optical path of the light pulse supplied from the light source unit, which extends a duration of the light pulse supplied from the light source unit while decreasing a peak power of the light pulse, the pulse-width extending optical system including a polarizing beam splitter to divide the light pulse into at least two light pulses.    
     
     
         10 . A light source apparatus according to  claim 9 , wherein: 
 the pulse-width extending optical system further comprises a beam converting member changing a polarized beam condition and at least one reflecting member.    
     
     
         11 . A light source apparatus according to  claim 9 , wherein the pulse-width extending optical system further comprises a beam deflecting system disposed to direct at least one of the pulse portions to the polarizing beam splitter, 
 wherein the polarizing beam splitter includes an optical dividing surface having a multi-layer coating.    
     
     
         12 . A light source apparatus according to  claim 11 , wherein the beam deflecting system comprises a relay optical system to form an image of the optical dividing surface on the optical dividing surface.  
     
     
         13 . A light source apparatus according to  claim 11 , wherein the beam deflecting system comprises a relay optical system disposed to produce a magnification of about +1 or −1.  
     
     
         14 . A light source apparatus according to  claim 9 , wherein the pulse-width extending optical system comprises a relay optical system to form an image of an optical surface on the optical surface.  
     
     
         15 . A light source apparatus according to  claim 9 , wherein the pulse-width extending optical system comprises a relay optical system disposed to produce a magnification of about +1 or −1.  
     
     
         16 . A light source apparatus according to  claim 9 , wherein the light source unit comprises an excimer laser source.  
     
     
         17 . A light source apparatus according to  claim 9 , wherein the pulse-width extending optical system provides a pulse length of at least 3 m with respect to the divided pulse portions.  
     
     
         18 . A light source apparatus comprising: 
 a light source unit supplying a light pulse having a wavelength not more than 193 nm; and    a pulse-width extending optical system arranged in an optical path of the light pulse supplied from the light source unit, which extends a duration of the light pulse supplied from the light source unit while decreasing a peak power of the light pulse, the pulse-width extending optical system including a beam converting member changing a polarized beam condition.    
     
     
         19 . A light source apparatus according to  claim 18 , wherein the beam converting member includes a half wavelength plate.  
     
     
         20 . A light source apparatus according to  claim 18 , wherein the light source unit comprises an excimer laser source.  
     
     
         21 . A light source apparatus according to  claim 18 , wherein the pulse-width extending optical system provides a pulse length of at least 3 m with respect to divided pulse portions.  
     
     
         22 . A light source apparatus comprising: 
 a light source unit supplying a light pulse having a wavelength not more than 193 nm; and    a pulse-width extending optical system arranged in an optical path of the light pulse supplied from the light source unit, which extends a duration of the light pulse supplied from the light source unit while decreasing a peak power of the light pulse, the pulse-width extending optical system including a light split member having a light split surface with a reflectance R such that 29.3%<R<50% or a transmittance T such that 29.3%<T<50%.    
     
     
         23 . A light source apparatus according to  claim 22 , wherein the pulse-width extending optical system comprises a beam dividing member to divide the light pulse into multiple pulse portions, and a beam deflecting system disposed to direct at least one of the pulse portions to the beam dividing member, 
 wherein the beam dividing member includes the light split surface having a multi-layer coating.    
     
     
         24 . A light source apparatus according to  claim 23 , wherein the beam deflecting system comprises a relay optical system to form an image of the light split surface on the light split surface.  
     
     
         25 . A light source apparatus according to  claim 23 , wherein the beam deflecting system comprises a relay optical system disposed to produce a magnification of about +1 or −1.  
     
     
         26 . A light source apparatus according to  claim 22 , wherein the pulse-width extending optical system comprises a relay optical system to form an image of the light split surface on the light split surface.  
     
     
         27 . A light source apparatus according to  claim 22 , wherein the pulse-width extending optical system comprises a relay optical system disposed to produce a magnification of about +1 or −1.  
     
     
         28 . A light source apparatus according to  claim 22 , wherein the light source unit comprises an excimer laser source.  
     
     
         29 . A light source apparatus according to  claim 22 , wherein the pulse-width extending optical system provides a pulse length of at least 3 m with respect to divided pulse portions.