Apparatus and method for determining wafer temperature using pyrometry

A method for controlling a RTP reactor in processing a semiconductor wafer, the RTP reactor having at least one heating element heating the wafer through a window, and a wafer pyrometer assembly adapted for measuring the wafer temperature through the window and producing wafer pyrometer measurements, the method comprising the steps of:

• mounting a window pyrometer assembly in said RTP reactor adapted for measuring the window temperature and producing window pyrometer measurements;
• loading a thermocouple wafer in said RTP reactor, said thermocouple wafer being adapted for producing true wafer temperatures;
• calibrating the wafer pyrometer assembly and producing first wafer pyrometer measurements, first true wafer temperatures, and first window pyrometer measurements for a predetermined range of first true wafer temperature measurements;
• compiling a wafer pyrometer calibration table indexable by said first wafer pyrometer measurements to access corresponding said first true wafer temperatures, and window pyrometer measurements;
• calibrating the window pyrometer assembly and producing second wafer pyrometer measurements, second true wafer temperatures, and second window pyrometer measurements for a predetermined number of thermal cycles;
• compiling a window pyrometer calibration table indexable by a window pyrometer offset to access a corresponding window temperature error factor, said window temperature error factors and window pyrometer offsets being computed from said second true wafer temperatures, second window pyrometer measurements, and by accessing said wafer pyrometer calibration table;
• removing said thermocouple wafer and loading a wafer for processing;
• executing a predetermined wafer processing heating sequence;
• collecting wafer pyrometer measurements and window pyrometer measurements;
• computing a corrected wafer temperature by accessing data stored in said wafer pyrometer calibration table and said window pyrometer calibration table;
• and
• controlling said heating element in response to said computed corrected wafer temperature.

Apparatus for controlling a RTP reactor, the RTP reactor having at least one heating element controllably heating a wafer through a window, and a wafer pyrometer assembly producing at least one wafer pyrometer measurement, comprising:

• a window pyrometer assembly mounted in the RTP reactor adapted for measuring the temperature of the window and producing a window pyrometer measurement;
• a window temperature compensation module receiving said wafer and window pyrometer measurements during wafer processing, said window temperature compensation module computing a corrected wafer temperature in response thereto;
• and
• a heating element controller receiving said computed corrected wafer temperature and generating heating lamp control signals in response thereto for controlling said heating element.

A method for controlling the temperature of at least one wafer being processed in a reactor chamber, the temperature of the wafer being modified by a heating system, the heating system being separated from the wafer by a window, the method comprising the steps of:

• executing a prescribed wafer temperature schedule for processing the wafer;
• remotely measuring the temperature of the wafer;
• measuring the temperature of the window;
• computing a corrected wafer temperature by using the measured wafer and window temperatures, and accessing a temperature calibration table;
• and
• controlling the hating system in response to the computed corrected wafer temperature and the prescribed wafer temperature schedule.