Electrostatic chuck with photo-patternable soft protrusion contact surface
View Patent ↗In accordance with an embodiment of the invention, there is provided a soft protrusion structure for an electrostatic chuck, which offers a non-abrasive contact surface for wafers, workpieces or other substrates, while also having improved manufacturability and compatibility with grounded surface platen designs. The soft protrusion structure comprises a photo-patternable polymer.
1. An electrostatic chuck comprising:
a surface layer activated by a voltage in an electrode to form an electric charge to electrostatically clamp a substrate to the electrostatic chuck, the surface layer including a plurality of hard-baked photo-patterned polymer protrusions comprising a hard-baked photo-patterned polymer and a charge control layer to which the plurality of hard-baked photo-patterned polymer protrusions adhere, the plurality of hard-baked photo-patterned polymer protrusions extending to a height above portions of the charge control layer surrounding the plurality of hard-baked photo-patterned polymer protrusions to support the substrate upon the plurality of hard-baked photo-patterned polymer protrusions during electrostatic clamping of the substrate.
2. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer comprises a polymer that, prior to baking, is photo-patternable, and liquid at room temperature.
3. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer comprises a polymer that, prior to baking, is photo-patternable, and solid at room temperature.
4. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer comprises an epoxy based polymer that, prior to baking, is photo-patternable.
5. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer comprises at least one of a polyimide based polymer and a benzocyclobutene based polymer, the hard-baked photo-patternable polymer being a polymer that, prior to baking, is photo-patternable.
6. An electrostatic chuck according to claim 1 , wherein the charge control layer comprises silicon carbide.
7. An electrostatic chuck according to claim 1 , wherein the charge control layer comprises diamond like carbon.
8. An electrostatic chuck according to claim 1 , wherein the charge control layer comprises a surface resistivity of between about 10 8 ohms per square to about 10 11 ohms per square.
9. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer protrusions comprise a height of between about 3 microns and about 12 microns.
10. An electrostatic chuck according to claim 1 , further comprising a gas seal ring comprising a hard-baked photo-patterned polymer.
11. An electrostatic chuck according to claim 1 , wherein the plurality of hard-baked polymer protrusions comprise a surface roughness of between about 0.02 μm and about 0.05 μm.
12. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer comprises a material having a tensile strength of greater than about 70 megapascals (MPa).
13. An electrostatic chuck according to claim 1 , wherein the hard-baked photo-patterned polymer comprises a material having a Young's modulus of less than about 3.5 gigapascals (GPa).
14. An electrostatic chuck according to claim 1 , further comprising a conductive path covering at least a portion of a workpiece-contacting surface of a gas seal ring of the electrostatic chuck, the conductive path comprising at least a portion of an electrical path to ground.
15. An electrostatic chuck according to claim 14 , wherein the hard-baked photo-patterned polymer comprises a polymer that, prior to baking, is photo-patternable, and liquid at room temperature, and wherein the charge control layer comprises a surface resistivity of between about 10 8 ohms per square to about 10 11 ohms per square.
16. A method of manufacturing an electrostatic chuck, the method comprising:
exposing a photo-patternable polymer, on a surface of the electrostatic chuck, to light through a mask, the electrostatic chuck comprising a charge control layer underlying at least a portion of the photo-patternable polymer;
removing areas of the surface of the electrostatic chuck based on a pattern of exposure of the surface to the light through the mask, thereby forming a plurality of polymer protrusions on the surface of the electrostatic chuck, the plurality of polymer protrusions adhering to the charge control layer and extending to a height above portions of the charge control layer surrounding the plurality of polymer protrusions, and
hard-baking the plurality of polymer protrusions to form a plurality of protrusion comprising hard-baked photo-patterned polymer.
17. A method according to claim 16 , comprising laminating a polymer sheet including the photo-patternable polymer over at least a portion of the charge control layer.
18. A method according to claim 16 , comprising spraying a liquid polymer including the photo-patternable polymer over at least a portion of the charge control layer.
19. A method according to claim 16 , wherein the plurality of protrusions comprising hard-baked photo-patterned polymer comprises a material having a tensile strength of greater than about 70 megapascals (MPa) and having a Young's modulus of less than about 3.5 gigapascals (GPa).
20. A method according to claim 16 , further comprising covering at least a portion of a workpiece-contacting surface of a gas seal ring of the electrostatic chuck with a conductive, path, the conductive path comprising at least a portion of an electrical path to ground.