Electrostatic chuck and method for manufacturing the same
An electrostatic chuck includes a first ceramic member disk-shaped and having an annular step surface outside a circular wafer holding surface thereof, the annular step surface being at a lower level than the wafer holding surface, the first ceramic member having a volume resistivity that allows Coulomb force to be exerted; a first electrode embedded in the first ceramic member at a position facing the wafer holding surface; a second electrode disposed on the annular step surface of the first ceramic member, the second electrode being independent of the first electrode; and a second ceramic member having an annular shape and configured to cover the annular step surface having the second electrode thereon, the second ceramic member having a volume resistivity that allows Johnsen-Rahbek force to be exerted, wherein an upper surface of the second ceramic member is a focus ring holding surface on which a focus ring is placed.
1. An electrostatic chuck comprising:
a first ceramic member disk-shaped and having an annular step surface outside a circular wafer holding surface thereof, the annular step surface being at a lower level than the wafer holding surface, the first ceramic member having a volume resistivity that allows Coulomb force to be exerted;
a first electrode embedded in the first ceramic member at a position facing the wafer holding surface;
a second electrode disposed on the annular step surface of the first ceramic member, the second electrode being independent of the first electrode; and
a second ceramic member having an annular shape and configured to cover the annular step surface having the second electrode thereon, the second ceramic member having a volume resistivity that allows Johnsen-Rahbek force to be exerted,
wherein an upper surface of the second ceramic member is a focus ring holding surface on which a focus ring is placed.
2. The electrostatic chuck according to claim 1 , wherein the second ceramic member is formed by coating or thermal spraying.
3. The electrostatic chuck according to claim 1 , wherein the volume resistivity of the first ceramic member is greater than or equal to 1×10 15 Ωcm at an operating temperature; and
the volume resistivity of the second ceramic member is greater than or equal to 1×10 8 Ωcm and less than or equal to 1×10 13 Ωcm at the operating temperature.
4. The electrostatic chuck according to claim 1 , wherein the second ceramic member is made of ceramic doped with a group IV element in the periodic table.
5. The electrostatic chuck according to claim 1 , wherein variation in thickness of the second ceramic member is not greater than 0.5 mm.
6. The electrostatic chuck according to claim 1 , wherein the second electrode is a bipolar electrode.
7. The electrostatic chuck according to claim 1 , wherein the annular step surface of the first ceramic member has an annular recessed groove U-shaped in cross-section;
the second electrode is disposed on a bottom surface of the annular recessed groove; and
the second ceramic member covers the bottom surface of the annular recessed groove having the second electrode thereon, and a surface of the second ceramic member is flush with an upper face of the annular step surface.
8. A method for manufacturing the electrostatic chuck according to claim 1 , the method comprising the steps of:
(a) preparing the first ceramic member having the first electrode embedded therein;
(b) forming the second electrode on the annular step surface of the first ceramic member by printing or coating; and
(c) forming the second ceramic member on the annular step surface by coating or thermal spraying, the annular step surface having the second electrode formed thereon.