High Efficiency High Accuracy Heater Driver

Abstract

A thermal process chamber having a lamp driver circuit that includes two transistors and two diodes is described. The thermal process chamber includes a plurality of halogen lamps, the lamp driver, a temperature sensor that measures wafer temperature, a temperature controller connected to the temperature sensor and to the lamp driver, the temperature controller providing control signals to the lamp driver that are functions of the wafer temperature and a desired temperature. The lamp driver includes two transistors that are controlled by the control signals so that the power factor of the power supplied to the plurality of halogen lamps is in the range of 0.9 to 1.

We claim: 
     
         1 . A method of controlling a thermal process chamber that processes a wafer, comprising:
 sensing a temperature of the wafer;   determining a desired temperature; and   generating a first control signal and a second control signal with a temperature controller in accordance with the temperature of the wafer and the desired temperature, the first control signal turning a first switch on and off a plurality of times per half cycle of AC power supplied to the temperature controller, the second control signal turning a second switch on and off a plurality of times per half cycle of AC power supplied to the temperature controller, and the first and second switch supplying power to a plurality of halogen lamps.   
     
     
         2 . The method of  claim 1 , wherein the first switch and the second switch are turned on at different times. 
     
     
         3 . The method of  claim 1 , wherein the first switch is turned on while the second switch is turned off. 
     
     
         4 . The method of  claim 3 , wherein the first switch is turned off while the second switch is turned on. 
     
     
         5 . The method of  claim 4 , wherein the first control signal and the second control signals are pulsed versions of the AC power. 
     
     
         6 . The method of  claim 5 , wherein a power factor of the power supplied to the plurality of halogen lamps is between 0.9 and 1. 
     
     
         7 . The method of  claim 6 , wherein the first switch and the second switch are transistors. 
     
     
         8 . The method of  claim 5 , wherein the first switch and the second switch are selected from the group consisting of MOSFET transistors, bipolar transistors and insulated gate bipolar transistors. 
     
     
         9 . The method of  claim 1 , wherein the first switch and the second switch are zones of halogen lamps.