News Article
Corning Has Received A US Patent For A Calcium Fluoride (CaF2) Lens Blank
Corning has received a US patent for a calcium fluoride (CaF2) lens blank
for 193nm and 157nm microlithography systems. The company says it can use
the technique to produce blanks consisting of multiple adjoining abutting
subgrains with low boundary angles.
At 157nm, the blank has an internal absorption coefficient of less than
0.0022/cm (base 10). For 193nm applications, the coefficient is less than
0.000431/cm. Birefringence is less than 5nm/cm.
The method includes forming a fluoride crystalline melt, crystallising the
melt into a fluoride crystalline member preferably with a large dimension -
greater than or equal to 200mm - and annealing the fluoride crystalline
member. The method further includes qualifying the annealed fluoride
crystalline member to provide a fluoride crystalline optical lithography
lens element blank.
0.0022/cm (base 10). For 193nm applications, the coefficient is less than
0.000431/cm. Birefringence is less than 5nm/cm.
The method includes forming a fluoride crystalline melt, crystallising the
melt into a fluoride crystalline member preferably with a large dimension -
greater than or equal to 200mm - and annealing the fluoride crystalline
member. The method further includes qualifying the annealed fluoride
crystalline member to provide a fluoride crystalline optical lithography
lens element blank.
