Electrostatic chuck which reduces arc discharge

1. An electrostatic chuck, comprising:

a ceramic dielectric substrate having a first major surface placing a suction object and a second major surface on an opposite side to the first major surface;

a base plate supporting the ceramic dielectric substrate and including a gas introduction path; and

a first porous part provided at a position between the base plate and the first major surface of the ceramic dielectric substrate and being opposite to the gas introduction path,

the ceramic dielectric substrate including a first hole part positioned between the first major surface and the first porous part,

at least one of the ceramic dielectric substrate or the first porous part including a second hole part positioned between the first hole part and the first porous part, and

in a second direction perpendicular to a first direction from the base plate toward the ceramic dielectric substrate, a dimension of the second hole part being smaller than a dimension of the first porous part and larger than a dimension of the first hole part.

2. The electrostatic chuck according to claim 1 , wherein the second hole part is provided in the ceramic dielectric substrate.

3. The electrostatic chuck according to claim 1 , wherein the second hole part is provided in the first porous part.

4. The electrostatic chuck according to claim 1 , wherein

the ceramic dielectric substrate further includes at least one groove communicating with the first hole part and opening to the first major surface, and

a dimension of the second hole part is smaller than a dimension of the groove in the first direction.

5. The electrostatic chuck according to claim 1 , further comprising:

an adhesion part provided between the ceramic dielectric substrate and the base plate,

a dimension of the second hole part being smaller than a dimension of the adhesion part in the first direction.

6. The electrostatic chuck according to claim 1 , further comprising:

a second porous part provided between the first porous part and the gas introduction path and including a plurality of pores,

an average value of diameters of the plurality of pores provided in the second porous part being larger than an average value of diameters of the plurality of pores provided in the first porous part.

7. The electrostatic chuck according to claim 6 , wherein

the plurality of pores provided in the second porous part is more dispersed three dimensionally than the plurality of pores provided in the first porous part, and

a ratio of pores piercing in the first direction is larger in the first porous part than the second porous part.

8. The electrostatic chuck according to claim 1 , further comprising:

a second porous part provided between the first porous part and the gas introduction path and including a plurality of pores,

fluctuation of diameters of a plurality of pores provided in the first porous part being smaller than fluctuation of diameters of the plurality of pores provided in the second porous part.

9. The electrostatic chuck according to claim 1 , further comprising:

a second porous part provided between the first porous part and the gas introduction path, wherein

a plurality of pores provided in the second porous part are more dispersed three dimensionally than a plurality of pores provided in the first porous part, and

a ratio of pores piercing in the first direction is larger in the first porous part than the second porous part.

10. The electrostatic chuck according to claim 1 , wherein

the first porous part and the ceramic dielectric substrate include aluminum oxide as a main component, and

a purity of aluminum oxide of the ceramic dielectric substrate is higher than a purity of aluminum oxide of the first porous part.

11. The electrostatic chuck according to claim 1 , wherein

the first porous part includes a plurality of sparse portions and a dense portion, the sparse portions including a plurality of pores including a first pore and a second pore, the dense portion having a density higher than a density of the sparse portions,

each of the plurality of sparse portions extends in the first direction,

the dense portion is positioned between the plurality of sparse portions,

the sparse portions include a wall part provided between the first pore and the second pore, and

a minimum value of a dimension of the wall part is smaller than a minimum value of a dimension of the dense portion in the second direction.

12. The electrostatic chuck according to claim 11 , wherein

a dimension of the plurality of pores provided in each of the plurality of sparse portions is smaller than a dimension of the dense portion in the second direction.

13. The electrostatic chuck according to claim 11 , wherein

an aspect ratio of the plurality of pores provided in each of the plurality of sparse portions is not less than 30 and not more than 1000.

14. The electrostatic chuck according to claim 11 , wherein

a dimension of the plurality of pores provided in each of the plurality of sparse portions is not less than 1 micrometer and not more than 20 micrometers in the second direction.

15. The electrostatic chuck according to claim 11 , wherein

when viewed along the first direction, the first pore is positioned at a center portion of the sparse portions, and

a number of pores of the plurality of pores adjacent to the first pore and surrounding the first pore is 6.