Crystallization method and crystallization apparatus

Abstract

A crystallization method includes the steps of melting a crystallized material in a crucible by heating, and growing a crystal by cooling and coagulating the melted material, wherein said melting step includes introducing a predetermined gas into the melted material.

1 . A crystallization method comprising the steps of: 
 melting a crystallized material in a crucible by heating; and    growing a crystal by cooling and coagulating the melted material,    wherein said melting step includes introducing a predetermined gas into the melted material.    
   
   
       2 . A crystallization method according to  claim 1 , wherein said crystallized material is a calcium fluoride with an added scavenger, and the gas that introduced into the melted fluorite is an inert gas.  
   
   
       3 . A crystallization method according to  claim 2 , wherein said inert gas is a helium gas.  
   
   
       4 . A crystallization method according to  claim 2 , wherein said crystallized material is a single crystal that does not have a grain boundary.  
   
   
       5 . An optical element made of a single crystal, said single crystal being manufactured by a crystallization method that includes: 
 melting a crystallized material in a crucible by heating; and    growing a crystal by cooling and coagulating the melted material,    wherein said melting step includes introducing a predetermined gas into the melted material, and    wherein said crystallized material is a calcium fluoride with an added scavenger, and the gas that introduced into the melted fluorite is an inert gas.    
   
   
       6 . An exposure apparatus comprising: 
 a light source;    an illumination optical system for guiding a light from the light source to a reticle; and    a projection optical system for guiding the light from the reticle to a wafer that is placed on a wafer stage,    wherein said illumination optical system or the projection optical system includes an optical element, and    wherein said optical element is made of a single crystal, said single crystal being manufactured by a crystallization method that includes:    melting a crystallized material in a crucible by heating; and    growing a crystal by cooling and coagulating the melted material,    wherein said melting step includes introducing a predetermined gas into the melted material, and    wherein said crystallized material is a calcium fluoride with an added scavenger, and the gas that introduced into the melted fluorite is an inert gas.    
   
   
       7 . A crystallization method according to  claim 1 , wherein said crystallized material is a lithium tantalate crystal or a lithium niobic acid, and the gas introduced into the melted lithium tantalate crystal or the lithium niobic acid is an oxygen or inert gas.  
   
   
       8 . A crystallization method according to  claim 7 , wherein said inert gas is a helium gas.  
   
   
       9 . A crystallization apparatus comprising: 
 a crucible arranged in a predetermined temperature distribution, and houses a melted crystallized material; and    a gas introducing part for introducing a gas into the melted crystallized material,    wherein the crystallization apparatus coagulates the melted crystallized material in one direction by changing the temperature distribution relatively to the crucible.    
   
   
       10 . A crystallization apparatus comprising: 
 a crucible heated at a predetermined temperature which houses a melted crystallized material; and    a gas introducing part for introducing a gas into the melted crystallized material,    wherein the crystallization apparatus grows a crystal by lifting a member that contacts with the melted crystallized material.    
   
   
       11 . A crystallization apparatus according to claims  9  or  10 , wherein the gas is an inert gas.