Patent ID: 7586734

Claim:
An electrostatic chuck comprising: a plate-like member having a pair of main surfaces, one of the main surfaces serving as a wafer mounting surface; and an electrostatic attraction electrode provided on the other main surface of the plate-like member or inside of the plate-like member, the plate-like member comprising at least one gas introducing through-hole formed so as to penetrate through the plate-like member, a gas flow passage for communicating with the through-hole, being formed between a plurality of protrusions disposed at distance from each other on the mounting surface, and a ring-shaped wall formed along the periphery of the plate-like member, wherein each of the protrusions has a planar configuration comprising four sides and four arced corners connecting the four sides, and all the protrusions are disposed substantially evenly on the mounting surface, wherein the plate-like member is made of a dielectric material containing aluminum nitride as a main component, mean distance between the electrode and the wafer mounting surface is 0.015 cm or more, the product of the mean distance and specific volume resistivity of the dielectric layer sandwiched by the mounting surface and the electrode is in a range from 1×10 7 to 5×10 16 Ω·cm 2 , mean grain size of aluminum nitride used in forming the dielectric layer is in a range from 1 to 20 μm and an open porosity in the dielectric layer is 1% or less.