Electrostatic chuck
In accordance with an embodiment of the invention, there is provided an electrostatic chuck comprising an electrode, and a surface layer activated by a voltage in the electrode to form an electric charge to electrostatically clamp a substrate to the electrostatic chuck. The surface layer includes a plurality of protrusions extending to a height above portions of the surface layer surrounding the protrusions to support the substrate upon the protrusions during electrostatic clamping of the substrate. The protrusions are substantially equally spaced across the surface layer as measured by a center to center distance between pairs of neighboring protrusions.
1. An electrostatic chuck comprising:
an electrode; and
a surface layer activated by a voltage in the electrode to form an electric charge to electrostatically clamp a substrate to the electrostatic chuck, the surface layer including:
(i) a dielectric comprising a bulk resistivity greater than about 10 12 ohm-cm;
(ii) a plurality of protrusions extending to a height above portions of the surface layer surrounding the protrusions to support the substrate upon the protrusions during electrostatic clamping of the substrate, the protrusions being substantially equally spaced across the surface layer as measured by a center to center distance between pairs of neighboring protrusions, the protrusions comprising a low stress material having an internal compressive film stress less than about 450 MPa and comprising an overcoating of diamond like carbon; and
(iii) a charge control surface layer coating overlying the dielectric and comprising a thickness in the range of from about 0.1 microns to about 10 microns and a surface resistivity in the range of from about 1×10 8 ohms/square to about 1×10 11 ohms/square, the charge control surface layer comprising a surface coating layer comprising portions of the surface layer surrounding the protrusions, above which the protrusions extend.
2. The electrostatic chuck of claim 1 , wherein the protrusions are arranged in a trigonal pattern.
3. The electrostatic chuck of claim 1 , wherein greater than about 75% of a top area of each of the protrusions contacts the substrate during the electrostatic clamping.
4. The electrostatic chuck of claim 1 , wherein the low stress material comprises at least one of an amorphous dielectric material and a polycrystalline dielectric material.
5. The electrostatic chuck of claim 1 , wherein the protrusions comprise a dielectric material, wherein the dielectric material is silicon, an alloy of silicon, silicon carbide, or non-stoichiometric silicon carbide.
6. The electrostatic chuck of claim 1 , wherein the protrusions comprise a dielectric material, wherein the dielectric material is alumina or aluminum nitride.
7. The electrostatic chuck of claim 1 , wherein the protrusions comprise a compliant dielectric material.
8. The electrostatic chuck of claim 1 , wherein a contact area of the protrusions with the substrate comprises from about 1% to about 10% of a total area of the electrostatic chuck.
9. The electrostatic chuck of claim 1 , wherein the center to center distance between pairs of neighboring protrusions is less than about 8 millimeters.