Single crystal calcium fluoride for photolithography

Abstract

A calcium fluoride single crystal for photolithography, wherein a critical resolved shear stress (τ c ) in a <1 1 0> direction on a {0 0 1 } plane of the calcium fluoride single crystal is approximately equal to or larger than a shear stress (τ) expressed by τ=1.5E−2·exp(3E3·T −1 ), where r is shear stress (MPa) and T is average temperature (K) of the calcium fluoride.

1 - 9 . (canceled)  
   
   
       10 . A calcium fluoride single crystal for photolithography, wherein a critical resolved shear stress (τ c ) in a <1 1 0> direction on a {0 0 1} plane of the calcium fluoride single crystal is approximately equal to or larger than a shear stress (τ) expressed by τ=1.5E−2·exp(3E3·T −1 ), where τ is shear stress (MPa) and T is average temperature (K) of the calcium fluoride.  
   
   
       11 . A calcium fluoride single crystal according to  claim 10 , wherein said calcium fluoride single crystal for photolithography has a diameter having Φ300 mm or larger and is used for a specific wavelength band less than 160 nm.  
   
   
       12 . A calcium fluoride single crystal according to  claim 10 , comprising one or more types of additional elements with a concentration of 20 ppm or larger.  
   
   
       13 . A calcium fluoride single crystal according to  claim 12 , wherein the additional elements include strontium having a concentration of 20 to 600 ppm.  
   
   
       14 - 21 . (canceled)