CERAMIC PART FOR SEMICONDUCTOR PRODUCTION DEVICE

PROBLEM TO BE SOLVED: To improve durability by using the translucent polycrystal comprising Y, Al and 0 in a specific composition. SOLUTION: The translucent polycrystalline ceramics expressed by the molecular formula, Y3Al5O12 has the following characteristics. The highly transmitted spectra show transmissivity nearly equal to the theoretical transmissivity in the range from ultraviolet region to infrared region. The strength obtained at the room temp. is kept up to about 1,400 deg.C. The ceramics is constituted of uniform and fine crystalline particles, wherein no amorphous phase presents at crystalline interface of particles, thereby there is almost free from formation of foreign matters. As the hardness is high, wear rate in etching is low. Thermal etching at the high temp. of 1,300 deg.C does not reduce the transmissivity. With respect to forming sides, it is possible to form the ceramics by slip casting and thereby the ceramics is easily formed by near net shaping. As the electric resistance is high, the ceramics can be used as a member which is required to be insulative. Further, as the ceramics has high purity, it is preferably used as members used in a vacuum chamber, provided in a semiconductor production device, which fabricates circuits or forms films or the like on a Si wafer at high temp. or in plasma.