Application of Emissivity Compensated Pyrometry for Temperature Measurement and Control During Compound Semiconductors Manufacturing

Deposition processes for many Compound Semiconductors Devices (such as InGaAsP/InP infrared laser diodes or InGaP/GaAs heterojunction bipolar transistors) are extremely temperature sensitive with temperature windows as small as 2 °C to 3 °C. Requirements for process temperature repeatability can be less than ± 0.25 °C at temperatures in the range ∼ 650 °C to 750 °C which significantly exceed typical requirements for the silicon industry. While temperature control is a vital requirement for growing reproducible structures, wafer temperatures can deviate significantly from those measured by conventional techniques such as close proximity thermocouples or optical pyrometers. Elements (such as susceptor, wafer carrier and gaps filled by low pressure gas) located between the thermocouple and the wafer lead to measurement errors, particularly when the environment of the chamber changes such as during gas switching. Optical pyrometer measurements may have an error up to 100 °C due to emissivity oscillations duri...