Patent ID: 7921802

Claim:
A wafer manufacturing apparatus comprising: a susceptor including a support for a wafer, the wafer including a topside and a bottom side; at least one optical fiber connected to the susceptor so that radiation from the bottom side of the wafer can be monitored; an optical signal measurer coupled to the at least one optical fiber, the optical signal measurer generating an electrical signal responsive to the radiation measured from the bottom side of the wafer; and a control system that is configured to maintain a deposition temperature of the wafer by calibrating the optical signal measurer by measuring a temperature of the susceptor at a first gas pressure; determining a signal level of the electrical signal when the measured temperature of the susceptor is at the deposition temperature, and by keeping, during a subsequent deposition cycle at a second gas pressure that is less than the first gas pressure, the electrical signal constant at the determined signal level.