Thermal diffuser for a semiconductor wafer holder
An electrostatic chuck is formed by depositing a diffuser layer onto an electrostatic puck and removing areas of the diffuser layer to form discrete diffuser segments separated by gaps. The discrete diffuser segments may define continuous concentric rings, discontinuous concentric rings, or a combination of continuous concentric rings and discontinuous concentric rings. The discrete diffuser segments are separated from each other by forming at least one trench in the diffuser layer. The trench may extend partially through the diffuser layer, completely through the diffuser layer to the electrostatic puck, or have a first portion that extends partially through the diffuser layer and a second portion that extends completely through the diffuser layer. Also, the trench can have a constant width or have a variable width.
1. An electrostatic chuck formed by a process comprising:
depositing a diffuser layer onto an electrostatic puck;
removing areas of the diffuser layer to form discrete diffuser segments separated by gaps;
bonding the electrostatic puck to a heater, wherein the diffuser layer is disposed between the electrostatic puck and the heater; and
bonding the heater to a cold plate,
wherein the discrete diffuser segments are made of the same material and are configured to allow a desired thermal gradient to be maintained between the discrete diffuser segments during heating of a target on the electrostatic puck.
2. The electrostatic chuck according to claim 1 , wherein the discrete diffuser segments define continuous concentric rings.
3. The electrostatic chuck according to claim 1 , wherein the discrete diffuser segments define discontinuous concentric rings.
4. The electrostatic chuck according to claim 1 , wherein the discrete diffuser segments define a combination of continuous concentric rings and discontinuous concentric rings.
5. The electrostatic chuck according to claim 1 , wherein the discrete diffuser segments are separated by forming at least one trench in the diffuser layer.
6. The electrostatic chuck according to claim 5 , wherein the at least one trench extends partially through the diffuser layer.
7. The electrostatic chuck according to claim 5 , wherein the at least one trench extends completely through the diffuser layer to the electrostatic puck.
8. The electrostatic chuck according to claim 5 , wherein the at least one trench extends partially through and completely through the diffuser layer to the electrostatic puck to define a variable depth.
9. The electrostatic chuck according to claim 5 , wherein the at least one trench defines a variable width.
10. The electrostatic chuck according to claim 5 , wherein the at least one trench is formed by a process selected from the group consisting of acid etching, laser cutting and machining.
11. The electrostatic chuck according to claim 1 , wherein the electrostatic puck is a ceramic material.
12. The electrostatic chuck according to claim 1 , wherein the heater comprises at least two heating zones and the diffuser rings are axially aligned with the at least two heating zones such that the at least two heating zones are thermally decoupled from each other.
13. The electrostatic chuck according to claim 1 , wherein the heater comprises an outer heating zone and an inner heating zone, and the diffuser rings are axially aligned with the outer heating zone and the inner heating zone to thermally decouple the outer heater zone from the inner heating zone such that a desired thermal gradient is maintained between the outer heater zone and the inner heating zone during heating of a target on the electrostatic puck.
14. The electrostatic chuck according to claim 1 , wherein the diffuser layer is formed from a material selected from the group consisting of aluminum, molybdenum, tungsten, nickel, zinc, silicon, and alloys thereof.
15. The electrostatic chuck according to claim 1 , wherein the diffuser layer is formed by cold spraying aluminum directly onto the electrostatic puck.
16. The electrostatic chuck according to claim 1 , wherein the heating layer is selected from the group consisting of a foil heater, a layered heater, and a damascene heater.
17. The electrostatic chuck according to claim 1 , wherein the heater is a polyimide heater.
18. The electrostatic chuck according to claim 17 , wherein the electrostatic puck is bonded to the polyimide heater with an elastomer.
19. The electrostatic chuck according to claim 17 further comprising a base plate, wherein the polyimide heater is bonded to the base plate with an elastomer.
20. The electrostatic chuck according to claim 1 , wherein the diffuser layer is an aluminum diffuser layer with a thickness of less than 0.040 inches (1.02 mm).
21. An electrostatic chuck formed by a process comprising:
depositing a diffuser layer onto an electrostatic puck;
cutting at least one trench in the diffuser layer and forming at least two diffuser rings arranged concentrically on the electrostatic puck and defining predetermined intervals with spacing in a radial direction;
bonding the electrostatic puck to a polyimide heater comprising at least two heating zones, wherein the at least two diffuser rings are disposed between the electrostatic ceramic puck and the polyimide heater; and
bonding the polyimide heater to a base plate,
wherein the at least two diffuser rings are made of the same material and are axially aligned with the at least two heating zones to thermally decouple the at least two heating zones such that a desired thermal gradient is maintained between the at least two diffuser rings during heating of a target on the electrostatic puck.
22. The electrostatic chuck according to claim 21 , wherein the at least two heating zones comprise an outer heating zone and an inner heating zone, and a desired thermal gradient is maintained between the outer heater zone and the inner heating zone during heating of the target on the electrostatic ceramic puck.
23. The electrostatic chuck according to claim 21 , wherein the electrostatic puck is bonded to the polyimide heater with a first elastomer layer and the polyimide heater is bonded to the base plate with a second elastomer layer.
24. The electrostatic chuck according to claim 21 , wherein the diffuser layer is deposited onto the electrostatic puck by cold spraying aluminum directly onto the electrostatic puck, and the diffuser layer has a thickness of less than 0.040 inches (1.02 mm).
25. A method of providing heat to a target part comprising:
attaching the target part to a chuck comprising an electrostatic puck bonded to a heater with at least two heating zones, wherein at least two diffuser rings formed from a diffuser layer bonded to the electrostatic ceramic puck are disposed between the electrostatic ceramic puck and the heater, the at least two diffuser rings arranged concentrically on the electrostatic ceramic puck and defining predetermined intervals with spacing in a radial direction; and
energizing the heater such that heat is transferred from the at least two heating zones to the target part, wherein the at least two diffuser rings are made of the same material and thermally decouple the at least two heating zones such that a desired thermal gradient is maintained between the at least two heating zones during heating of the target part.
26. The method according to claim 25 , wherein the heater is a polyimide heater and the at least two diffuser rings are bonded to the polyimide heater with a first elastomer layer and the polyimide heater is bonded to a base plate with a second elastomer layer.
27. The method according to claim 26 , wherein the polyimide heater comprises a heating layer, a dielectric layer and a routing layer, and the first elastomer layered is disposed between the at least two diffuser rings and the dielectric layer and the second elastomer layer is disposed between the routing layer and the base plate.