Methods and apparatus for controlling temperature of a multi-zone heater in an process chamber

A method of controlling a multi-zone heater disposed in a substrate support, the multi-zone heater having a first zone and a second zone, the method comprising:

• measuring a current drawn by the first zone at a first time;
• measuring a voltage drawn by the first zone at the first time;
• calculating the resistance of the first zone based upon the measured current and voltage drawn by the first zone at the first time;
• determining a temperature of the first zone based upon a predetermined relationship between the resistance and the temperature of the first zone;
• and
• adjusting the temperature of the first zone in response to the temperature determination,
• wherein the first zone is an outer zone and the second zone is an inner zone disposed within the outer zone, wherein the first zone is heated to a desired temperature before the second zone is heated, and wherein a thermocouple is coupled to the second zone to measure the temperature of the second zone.

A method of controlling a multi-zone heater disposed in a substrate support, the multi-zone heater having a first zone and a second zone, the method comprising:

• measuring a current drawn by the first zone at a first time;
• measuring a voltage drawn by the first zone at the first time;
• calculating the resistance of the first zone based upon the measured current and voltage drawn by the first zone at the first time;
• determining a temperature of the first zone based upon a predetermined relationship between the resistance and the temperature of the first zone;
• adjusting the temperature of the first zone in response to the temperature determination;
• measuring the temperature of the second zone;
• and
• adjusting the temperature of the second zone in response to the measurement,
• wherein the first zone is an outer zone and the second zone is an inner zone disposed within the outer zone, wherein the first zone is heated to a desired temperature before the second zone is heated, wherein a thermocouple is coupled to the second zone to measure the temperature of the second zone, and wherein calculating the resistance of the first zone, determining a temperature of the first zone and adjusting the temperature of the first zone occurs at a second time that is within about 100 ms of the first time.