Patent ID: 7276219

Claim:
A lithography excimer laser optical element blank optical fluoride crystal with increased far-ultraviolet transmission, said optical fluoride crystal including barium fluoride, said optical fluoride crystal including barium fluoride formed from a molten optical fluoride melt including barium fluoride, said optical fluoride crystal including barium fluoride having an increased far-ultraviolet transmission with an internal transmission at 157 mm≧99.3%/cm; and said optical fluoride crystal having a plurality of crystalline subgrains, each of said subgrains having a crystalline subgrain structure, said optical fluoride crystal including at least a first subgrain structure and a second subgrain structure, said second subgrain structure adjacent and abutting said first subgrain structure at a first defect boundary formed by a plurality of dislocation defects, said boundary dislocation defects having an adjacent first subgrain-second subgrain boundary angle, said first subgrain-second subgrain boundary angle less than two minutes.