AC-driven electrostatic chuck
According to an aspect of an embodiment of the invention, there is provided an AC-driven electrostatic chuck including: a dielectric substrate including protrusions formed on a major surface on a side of mounting a clamped object, and a bottom surface part formed around the protrusions; and an electrode provided on the dielectric substrate, the electrode including a plurality of electrode elements spaced from each other, the plurality of electrode elements being enabled to be applied with an AC voltage of mutually different phases, respectively, and the protrusions being arranged on the major surface with a prescribed spacing depending on shape of the plurality of electrode elements. The AC-driven electrostatic chuck is capable of suppressing local damage to part of the protrusions provided on the mounting surface side.
1. An AC-driven electrostatic chuck comprising:
a dielectric substrate having a major surface which is configured to support thereon an object which is to be electrostatically clamped by the chuck, the major surface having a bottom part and a plurality of protrusions which extend upwardly from the bottom part; and
an electrode provided in the dielectric substrate,
the electrode including a plurality of electrode elements spaced from each other with gaps therebetween,
the plurality of electrode elements being configured to be applied with an AC voltage of mutually different phases, respectively, and
the plurality of protrusions being arranged on the major surface with a prescribed spacing therebetween based on each shape of the plurality of electrode elements such that the protrusions are at positions only on a projection image of the electrode elements obtained by projecting each shape of the plurality of electrode elements on the major surface.
2. The chuck according to claim 1 , wherein
the plurality of protrusions are at positions not located on center lines of the electrode elements of the projection image.
3. The chuck according to claim 2 , wherein the plurality of protrusions are at positions symmetric with respect to the center lines of the electrode elements of the projection image.
4. The chuck according to claim 1 , wherein
the plurality of protrusions are at positions symmetric with respect to center lines of the gaps between the electrode elements of the projection image.
5. The chuck according to claim 1 , wherein
the plurality of protrusions exist are on center lines of the electrode elements of the projection image.
6. The chuck according to claim 5 , wherein the protrusions arranged on an outer peripheral part of the major surface are arranged at positions of the projection image of the electrode elements selectively shifted toward an outer periphery of the major surface, while the plurality of protrusions arranged on a central part of the major surface are not, as viewed perpendicularly to the major surface.
7. The chuck according to claim 5 , wherein the electrode elements are arranged in tracks separated from each other in a radial direction of the electrode, and the protrusions arranged on the track second from an outermost periphery of the major surface as viewed perpendicularly to the major surface are arranged at positions of the projection image of the electrode elements selectively shifted toward the outermost periphery of the major surface, while the plurality of protrusions arranged on other than the second track from the outermost periphery are not, as viewed perpendicularly to the major surface.
8. The chuck according to claim 1 , wherein spacing between adjacent ones of the plurality of protrusions arranged on a central part of the major surface is narrower than spacing between adjacent ones of the plurality of protrusions arranged on an outer peripheral part of the major surface.
9. The chuck according to claim 1 , wherein the gaps between adjacent ones of the plurality of electrode elements arranged on a central part of the major surface have narrower width than that of the gaps between adjacent ones of the plurality of electrode elements arranged on an outer peripheral part of the major surface.
10. The chuck according to claim 1 , wherein a ratio of area of top surfaces of the plurality of protrusions arranged on a central part of the major surface to total area of the major surface is higher than a ratio of area of top surfaces of the plurality of protrusions arranged on an outer peripheral part of the major surface to the total area of the major surface as viewed perpendicularly to the major surface.
11. The chuck according to claim 1 , wherein each diameter of the protrusions arranged on an outer peripheral part of the major surface is equal to or larger than each diameter of the protrusions arranged on a central part of the major surface.
12. The chuck according to claim 1 , wherein the plurality of electrode elements are configured to be applied with an AC voltage of three mutually different phases.
13. The chuck according to claim 1 , wherein the plurality of electrode elements are configured to be applied with an AC voltage having a frequency of 0.1-500 Hz.
14. An AC-driven electrostatic chuck comprising:
a dielectric substrate having a major surface which is configured to support thereon an object which is to be electrostatically clamped by the chuck without any intervening conductor, the major surface having a bottom part and a plurality of protrusions which extend upwardly from the bottom part; and
an electrode provided in the dielectric substrate,
the electrode including a plurality of electrode elements spaced from each other with gaps therebetween,
the plurality of electrode elements being configured to be applied with an AC voltage of mutually different phases, respectively, and
the plurality of protrusions being arranged on the major surface with a prescribed spacing therebetween based on each shape of the plurality of electrode elements such that the protrusions are at positions not located on a projection image of the electrode elements obtained by projecting each shape of the plurality of electrode elements on the major surface.
15. The chuck according to claim 14 , wherein
the plurality of protrusions are at positions not located on center lines of the gaps between the electrode elements of the projection image.
16. The chuck according to claim 15 , wherein the plurality of protrusions are at positions symmetric with respect to the center lines of the gaps between the electrode elements of the projection image.
17. The chuck according to claim 14 , wherein
the plurality of protrusions are at positions located on center lines of the gaps between the electrode elements of the projection image.
18. The chuck according to claim 17 , wherein the protrusions arranged on an outer peripheral part of the major surface are arranged at positions of the projection image of the electrode elements selectively shifted toward an outer periphery of the major surface, while the plurality of protrusions arranged on a central part of the major surface are not, as viewed perpendicularly to the major surface.
19. The chuck according to claim 17 , wherein the electrode elements are arranged in tracks separated from each other in a radial direction of the electrode, and the protrusions arranged on the track second from an outermost periphery of the major surface as viewed perpendicularly to the major surface are arranged at positions of the projection image of the electrode elements selectively shifted toward the outermost periphery of the major surface, while the plurality of protrusions arranged on other than the second track from the outermost periphery are not, as viewed perpendicularly to the major surface.
20. The chuck according to claim 14 , wherein spacing between adjacent ones of the plurality of protrusions arranged on a central part of the major surface is narrower than spacing between adjacent ones of the plurality of protrusions arranged on an outer peripheral part of the major surface.
21. The chuck according to claim 14 , wherein spacing between adjacent ones of the plurality of electrode elements arranged on a central part of the major surface is narrower than spacing between adjacent ones of the plurality of electrode elements arranged on an outer peripheral part of the major surface.
22. The chuck according to claim 14 , wherein a ratio of area of top surfaces of the plurality of protrusions arranged on a central part of the major surface to total area of the major surface is higher than a ratio of area of top surfaces of the plurality of protrusions arranged on an outer peripheral part of the major surface to the total area of the major surface as viewed perpendicularly to the major surface.
23. The chuck according to claim 14 , wherein each diameter of the protrusions arranged on an outer peripheral part of the major surface is equal to or larger than each diameter of the protrusions arranged on a central part of the major surface.
24. The chuck according to claim 14 , wherein the plurality of electrode elements are configured to be applied with an AC voltage of three mutually different phases.
25. The chuck according to claim 14 , wherein the plurality of electrode elements are configured to be applied with an AC voltage having a frequency of 0.1-500 Hz.