Monitoring witness structures for temperature control in RTP systems

A method for thermally processing an object in a thermal processing chamber, the method comprising:

• placing an object to be processed in a thermal processing chamber containing a witness structure, the thermal processing chamber being in association with a measurement device, wherein the measurement device has previously monitored a property of the witness structure over a time interval to produce stored data, and wherein the measurement device comprises either a light pipe embedded in the body of the witness structure or a pyrometer;
• performing a processing cycle, including directing radiant energy into the chamber via a heating system, wherein the heating system is controllable so as to direct energy to a plurality of zones of the object to be processed;
• and
• during the process cycle:
• observing a property of the witness structure using the measurement device,
• comparing the property of the witness structure observed to the stored data produced by the measurement device over the time interval;
• deducing the thermal response of the witness structure based on the comparison of the property of the witness structure observed to the stored data produced by the measurement device over the time interval,
• determining the amount of radiant energy incident on the witness structure based on the thermal response of the witness structure,
• making a control decision based on the amount of radiant energy determined to be incident on the witness structure, and
• changing the amount of radiant energy directed into the chamber and applied to a zone of the object relative to another zone of the object to thereby adjust a temperature distribution across the object if warranted by the control decision.