Nikon Corporation

Kazuo Kimura

Tsutomu Mizugaki

Shuuichi Takano

Shigeru Sakuma

A manufacturing method for a single crystal of calcium fluoride by which it is possible to obtain a single crystal of calcium fluoride with adequately small double refraction, which can be used in optical systems for photolithography, and in particular, a single crystal of calcium fluoride with a large diameter (&oslash;200 mm or larger) having superior optical properties, which can be used for photolithography with a wavelength of 250 nm or less. A manufacturing method for a single crystal of calcium fluoride, having its optical properties improved through an annealing process in which a single crystal of calcium fluoride is contained in a sealable container, and said container is sealed and vacuumed, followed by, a process of heating with a heater arranged external to said container so that the temperature inside said container is raised to a first temperature, which is lower than the melting point of said single crystal of calcium fluoride, a process by which the temperature inside said container is maintained at said first temperature for a designated period of time, and a process by which the temperature inside said container is lowered to room temperature, wherein, the maximum temperature of the annealing process is set to be a first temperature within the range of 1020 to 1150&deg; C. Also provided is a manufacturing method for a single crystal of calcium fluoride having its optical properties improved through an annealing process such that, its maximum temperature during the thermal process is set to a first temperature which is within the range of 1020 to 1150&deg; C., and which is maintained for a designated period of time, and its cooling speed for reaching a second temperature, which is in the range of (or around) 600 to 800&deg; C., from said first temperature is set to be 1.2&deg; C./hour or less, or its cooling speed for reaching a second temperature, which is in the range of (or around) 700 to 900&deg; C., from said first temperature is set to be 1.2&deg; C./hour or less.

Manufacturing method for calcium fluoride and calcium fluoride for photolithography

A manufacturing method for a single crystal of calcium fluoride by which it is possible to obtain a single crystal of calcium fluoride with adequately small double refraction, which can be used in optical systems for photolithography, and in particular, a single crystal of calcium fluoride with a large diameter (&oslash; 200 mm or larger) having superior optical properties, which can be used for photolithography with a wavelength of 250 nm or less. A manufacturing method for a single crystal of calcium fluoride, having its optical properties improved through an annealing process in which a single crystal of calcium fluoride is contained in a sealable container, and said container is sealed and vacuumed, followed by, a process of heating with a heater arranged external to said container so that the temperature inside said container is raised to a first temperature, which is lower than the melting point of said single crystal of calcium fluoride, a process by which the temperature inside said container is maintained at said first temperature for a designated period of time, and a process by which the temperature inside said container is lowered to room temperature, wherein, the maximum temperature of the annealing process is set to be a first temperature within the range of 1020 to 1150&deg; C. Also provided is a manufacturing method for a single crystal of calcium fluoride having its optical properties improved through an annealing process such that, its maximum temperature during the thermal process is set to a first temperature which is within the range of 1020 to 1150&deg; C., and which is maintained for a designated period of time, and its cooling speed for reaching a second temperature, which is in the range of (or around) 600 to 800&deg; C., from said first temperature is set to be 1.2&deg; C./hour or less, or its cooling speed for reaching a second temperature, which is in the range of (or around) 700 to 900&deg; C., from said first temperature is set to be 1.2&deg; C./hour or less.

A manufacturing method for a single crystal of calcium fluoride includes the steps of degassing calcium fluoride powder particles to desorb impurities from surfaces of the calcium fluoride powder particles, preprocessing the degassed calcium fluoride powder particles by fusing the degassed calcium fluoride powder particles in a crucible to obtain a preprocessed product, and re-fusing the preprocessed product in a crucible to grow a single crystal of calcium fluoride.

Growing community of inventors

Machida, Japan

Kazuo Kimura