Emissivity profile control for thermal uniformity
A substrate for processing in a heating system is disclosed. The substrate includes a bottom portion for absorbing heat from a radiating heat source, the bottom portion having a first region having a first emissivity and a second region having a second emissivity less than the first emissivity. The first region and the second region promote thermal uniformity of the substrate by compensating for thermal non-uniformity of the radiating heat source.
1. A susceptor for heating a substrate in an induction heating system, said susceptor having a top surface for transmitting heat to the substrate, the top surface having multiple regions including at least a first region having a first emissivity and a second region having a second emissivity different than the first emissivity
wherein the second region has a thin film coating deposited thereon;
wherein the first region comprises a graphite material; and
wherein the thin film coating comprises a metallic material selected from the group consisting of silver, copper, or molybdenum.
2. The susceptor of claim 1 , wherein the first region and the second region promote uniform thermal transmission across the top surface of the susceptor, the uniform thermal transmission defined by a temperature variation in the substrate of less than approximately 100 K when heated by the susceptor to a temperature range of 1000 k to 2000 K.
3. The susceptor of claim 1 , wherein the surface roughness of the second region is less than the surface roughness of the first region.
4. The susceptor of claim 1 , wherein the first region and the second region are radially symmetric.
5. The susceptor of claim 1 , wherein the induction heating system includes an RF coil formed as a planar spiral, the first emissivity of the first region and the second emissivity of the second region compensating for non-uniform inductive heating of the susceptor by the RF coil.
6. A method for heating a substrate in an induction heating system, comprising:
disposing a substrate above a susceptor;
inductively heating the susceptor, the inductive heating providing non-uniform heating of the susceptor;
compensating for the non-uniform heating of the susceptor to provide substantially uniform heating of the substrate, the compensating comprising performing one of variably absorbing heat at a bottom surface of the substrate or variably transmitting heat of the susceptor at a top surface of the susceptor;
wherein variably absorbing heat at the bottom surface of the substrate includes absorbing heat through a first bottom surface portion having a first emissivity and absorbing heat through a second bottom surface portion having a second emissivity less than the first emissivity.
7. The method of claim 6 , wherein the second bottom surface portion comprises an annular ring surrounding the first bottom surface portion.
8. The method of claim 6 ,
wherein variably transmitting heat of the susceptor at the top surface of the susceptor includes transmitting heat through a first top surface portion having a first emissivity and transmitting heat through a second top surface portion having a second emissivity less than the first emissivity.
9. The method of claim 8 , wherein the second top surface portion comprises an annular ring surrounding the first top surface portion.
10. The method of claim 6 , wherein the substantially uniform heating of the substrate is defined by a temperature variation of less than approximately 100 K when the substrate is heated to a temperature range of approximately 1000 K to 2000 K.
11. The method of claim 6 , wherein inductively heating the susceptor includes applying a current to an RF coil.