Method and apparatus for reducing thermal gradients within a substrate support

A method and apparatus for reducing the thermal gradients within substrate support such as a ceramic wafer support pedestal. Specifically, the present invention is a heater controller that limits the amount of power that is applied to a resistive heater embedded within a ceramic pedestal. The heater controller comprises the necessary circuitry for limiting the amount of power applied to one or more zones with respect to a single other zone. Said heater controller also contains the necessary circuitry to detect faulty or misconnected wires between heater controller and the zones to be heated.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 depicts a cross-sectional view of a ceramic pedestal containing a resistive heater that is connected to a heater controller in accordance with the present invention;

FIG. 2 depicts a top view of the resistive heater as seen along lines

2—

2 of FIG. 1;

FIG. 3 depicts a schematic view of a system for controlling power and current to a ceramic heater in accordance with the present invention;

FIG. 4 depicts a graph of power vs. temperature for a resistive heater that is controlled in accordance with the present invention;

FIG. 5 depicts a detailed view of a system controller for controlling the system of the subject invention; and

FIG. 6 depicts a series of steps of a method for controlling power and current in accordance with the present invention.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

1. Apparatus for controlling thermal gradients generated within more than one zone of a substrate support pedestal in a semiconductor process system comprising:

2. The apparatus of claim 1 wherein said pedestal further comprises a resistive heater having more than one coil, each of said more than one zone corresponding to said more than one coil.

3. The apparatus of claim 2 wherein the zone control module controls the amount of power provided to said more than one coil.

4. The apparatus of claim 1 wherein the heater controller further comprises a phase angle control module connected to the zone control module.

5. The apparatus of claim 2 wherein the heater controller further comprises a wire detection circuit connected to the zone control module.

6. The apparatus of claim 5 wherein the wire detection circuit evaluates the status of one or more connections between the heater controller and the heater.

7. The apparatus of claim 6, wherein said status of said one or more connections is selected from the group consisting of all connections properly connected to all coils, one or more connections inverted with respect to the coils, one or more connections not transmitting power from the heater controller to one or more coils, one or more connections transmitting power from the heater controller to one or more coils at an inappropriate time, one or more connections short-circuited and one or more connections open-circuited.

8. The apparatus of claim 1 wherein the substrate support pedestal is a ceramic pedestal and each of said more than one zone has a resistive heater.

9. A method of reducing thermal gradients within a substrate support pedestal in a semiconductor process system having more than one zone, the method comprising the steps of:

10. The method of claim 9 wherein step (a) further comprises applying 100% of the power produced by a heater controller connected to said substrate support pedestal.

11. The method of claim 10 wherein step (b) further comprises determining if an electrical connection between said substrate support pedestal and said heater controller is properly connected.

12. The method of claim 11 wherein if said electrical connector is not properly connected, a powerdown and recheck of said connector is performed.

13. The method of claim 9 wherein step (c) further comprises raising the temperature of the substrate support pedestal to a temperature of approximately 550° C.

14. The method of claim 10 wherein step (d) further comprises applying 100% power to a first outer zone of the substrate support pedestal and applying 50% of said power to a second inner zone of said substrate support pedestal.

15. The method of claim 9 wherein said substrate support pedestal is a ceramic electrostatic chuck.

16. In a system for controlling a substrate support having more than one temperature controllable zones, a computer readable medium in a general purpose computer system that operates as a special purpose controller when executing a zoned temperature control program for said substrate support to perform a process comprising the steps of: