Alumina-based sintered body and electrostatic chuck
In an alumina-based sintered body containing alumina (Al 2 O 3 ) as a main component and containing magnesia (MgO) whose content with respect to a content of the alumina is 0.00 mol %<MgO≤0.20 mol %, a density is 3.96 g/cm 3 or greater, and a standard deviation of grain sizes of alumina crystal grains is smaller than 4.0 μm.
1 . An alumina-based sintered body containing alumina (Al 2 O 3 ) as a main component and containing magnesia (MgO) whose content with respect to a content of the alumina is 0.00 mol % <MgO≤0.20 mol %, wherein
a density is 3.96 g/cm 3 or greater, and a standard deviation of grain sizes of alumina crystal grains is smaller than 4.0 μm, a presence quantity of voids is 0.050 pieces/μm 2 or less, and
when the voids are divided into first voids which are voids present at crystal grain boundaries and second voids which are voids present in crystal grains, a ratio of a presence quantity of the second voids to the presence quantity of the voids is 20% or greater.
2 . The alumina-based sintered body in accordance with claim 1 , wherein a dielectric breakdown voltage is 200 kV/mm or greater.
3 . The alumina-based sintered body in accordance with claim 1 , wherein
a surface roughness Sa of a surface irradiated with plasma for 40 minutes is 50 nm or smaller.
4 . An electrostatic chuck at which a target object is retained, the electrostatic chuck comprising:
a plate-shaped member having a first surface at which the target object is retained, a second surface opposite to the first surface, and a chuck electrode formed either at the second surface or inside the plate-shaped member; and
a base member provided on the second surface side of the plate-shaped member and having a cooling function, wherein
the first surface of the plate-shaped member is formed of the alumina-based sintered body in accordance with claim 1 .
5 . The electrostatic chuck in accordance with claim 4 , wherein
the plate-shaped member has
a gas flow path which has an opening at the first surface and into which gas is introduced from the second surface side, and
a seal band portion continuously formed on the first surface along an outer edge of the plate-shaped member, and
the opening of the gas flow path is formed on an inner side relative to the seal band portion.
6 . An alumina-based sintered body containing alumina (Al 2 O 3 ) as a main component, wherein
a presence quantity of voids is 0.050 pieces/μm 2 or less, and
when the voids are divided into first voids which are voids present at crystal grain boundaries and second voids which are voids present in crystal grains, a ratio of a presence quantity of the second voids to the presence quantity of the voids is 20% or greater.
7 . The alumina-based sintered body in accordance with claim 2 , wherein
a surface roughness Sa of a surface irradiated with plasma for 40 minutes is 50 nm or smaller.
8 . An electrostatic chuck at which a target object is retained, the electrostatic chuck comprising:
a plate-shaped member having a first surface at which the target object is retained, a second surface opposite to the first surface, and a chuck electrode formed either at the second surface or inside the plate-shaped member; and
a base member provided on the second surface side of the plate-shaped member and having a cooling function, wherein
the first surface of the plate-shaped member is formed of the alumina-based sintered body in accordance with claim 2 .
9 . An electrostatic chuck at which a target object is retained, the electrostatic chuck comprising:
a plate-shaped member having a first surface at which the target object is retained, a second surface opposite to the first surface, and a chuck electrode formed either at the second surface or inside the plate-shaped member; and
a base member provided on the second surface side of the plate-shaped member and having a cooling function, wherein
the first surface of the plate-shaped member is formed of the alumina-based sintered body in accordance with claim 3 .
10 . An alumina-based sintered body containing alumina (Al 2 O 3 ) as a main component and containing magnesia (MgO) whose content with respect to a content of the alumina is 0.00 mol % <MgO≤0.20 mol %, wherein
a density is 3.96 g/cm 3 or greater,
a standard deviation of grain sizes of alumina crystal grains is smaller than 4.0 μm, and
a dielectric breakdown voltage is 200 kV/mm or greater.