Kyocera Corporation

Nikon Corporation

Yoshihisa Sechi

Hiroshi Aida

Shoji Kohsaka

Yutaka Hayashi

Low thermal expansion ceramics contains a cordierite crystal phase, wherein a phase of a crystalline compound containing at least one element selected from the group consisting of an alkaline earth element other than Mg, a rare earth element, Ga and In, is precipitated in the grain boundaries of said crystal phase, said ceramics has a relative density of not smaller than 95%, a coefficient of thermal expansion of not larger than 1&#xd7;10/&#xb0; C. at 10 to 40&#xb0; C., and a Young's modulus of not smaller than 130 GPa. That is, the ceramics has a small coefficient of thermal expansion, is deformed very little depending upon a change in the temperature, has a very high Young's modulus and is highly rigid and is resistance against external force such as vibration. Accordingly, the ceramics is very useful as a member for supporting a wafer or an optical system is a lithography apparatus that forms high resolution circuit patterns on a silicon wafer.

Ceramic sintered product and process for producing the same

Low thermal expansion ceramics contains a cordierite crystal phase, wherein a phase of a crystalline compound containing at least one element selected from the group consisting of an alkaline earth element other than Mg, a rare earth element, Ga and In, is precipitated in the grain boundaries of said crystal phase, said ceramics has a relative density of not smaller than 95%, a coefficient of thermal expansion of not larger than 1&times;10,/&deg; C. at 10 to 40&deg; C., and a Young's modulus of not smaller than 130 GPa. That is, the ceramics has a small coefficient of thermal expansion, is deformed very little depending upon a change in the temperature, has a very high Young's modulus and is highly rigid and is resistance against external force such as vibration. Accordingly, the ceramics is very useful as a member for supporting a wafer or an optical system is a lithography apparatus that forms high resolution circuit patterns on a silicon wafer.

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Kokubu, Japan

Yoshihisa Sechi