Apparatus for improving temperature uniformity of a workpiece
View Patent ↗An apparatus and method for improving the temperature uniformity of a workpiece during processing is disclosed. The apparatus includes a ring heater assembly disposed along the outer circumference of the platen. The ring heater assembly includes heating elements disposed therein or thereon, where these heating elements create heat, which serves to warm the outer edge of the workpiece. In some embodiments, the ring heater assembly extends beyond the edge of the workpiece and may be exposed to the ion beam.
1. A workpiece holding and heating apparatus, comprising:
a platen;
a base supporting the platen;
a ring heater assembly surrounding an outer circumference of the platen, the ring heater assembly comprising a protective shield on a top surface and a plurality of heating elements disposed beneath the protective shield, each heating element disposed in a respective ring heater; the plurality of ring heaters forming an annular ring;
a plurality of mounting frames, each in contact with the base, to hold the ring heater assembly in place;
a plurality of blocks attached to an underside of the ring heater assembly, each block disposed between two adjacent ring heaters so as to support the two adjacent ring heaters;
a plurality of flexures extending outward from each mounting frame and connecting to a respective one of the plurality of blocks used to support the ring heater assembly, wherein the plurality of flexures are curved and extend outward and upward from the mounting frame past the outer circumference of the platen, and wherein the base is not disposed beneath the ring heater assembly and the plurality of flexures provides the only mechanical support for the ring heater assembly; and
electrical conduits, different from the flexures, to provide power to the ring heater assembly.
2. The apparatus of claim 1 , wherein each heating element is encased in the protective shield.
3. The apparatus of claim 2 , wherein the protective shield is a ceramic material.
4. The apparatus of claim 1 , further comprising a power supply in communication with the ring heater assembly.
5. The apparatus of claim 4 , further comprising a temperature sensor disposed near the top surface of the ring heater assembly, wherein the power supply controls an output based on feedback from the temperature sensor.
6. The apparatus of claim 4 , wherein the power supply regulates an output based on a desired temperature.
7. The apparatus of claim 1 , wherein the base comprises receptacles disposed about a perimeter of the base, wherein the plurality of mounting frames mates to the base using the receptacles.
8. The apparatus of claim 1 , wherein the flexures attach to the block using a threaded connection.
9. The apparatus of claim 1 , wherein the flexures comprise tubes.
10. The apparatus of claim 1 , wherein the electrical conduits are disposed in one of the plurality of flexures.
11. The apparatus of claim 1 , further comprising a heat shield disposed beneath the ring heater assembly.
12. The apparatus of claim 1 , wherein the platen is heated.
13. The apparatus of claim 12 , wherein the platen comprises a plurality of conduits terminating at a upper surface of the platen to supply back side gas to a volume between the platen and a workpiece disposed on the platen.
14. The apparatus of claim 1 , wherein the blocks are metal and brazed to the ring heaters.
15. The apparatus of claim 1 , wherein the ring heaters are graphite, and the blocks are attached to the ring heaters using threaded hardware.
16. The apparatus of claim 1 , wherein the blocks are clamped around a machined feature disposed on the bottom of the ring heaters.
17. The apparatus of claim 1 , wherein there are at least three ring heaters.