Simultaneous measurement of CH₄ concentration and temperature distributions in a semiconductor process chamber

Methane (CH₄) concentration and temperature distributions were measured in a semiconductor process chamber using computed tomography-tunable diode laser spectroscopy (CT-TDLAS). A semiconductor chamber was designed with 32 laser-paths to collect the infrared spectrum of CH₄ with tunable diode laser absorption spectroscopy. Absorptions at wavelength of 1628.1 nm and 1653.7 nm were used to reconstruct CH₄ concentration and temperature distributions using computed tomography (CT) calculations. The validity of our CT algorithm for concentration and temperature distributions was checked using computer fluid dynamics. Concentration and temperature distributions were generated by injecting CH₄ with different concentrations (5% or 10%) into the four inlet ports and setting different temperatures (25 °C or 125 °C) for four heater blocks on the susceptor. The pressure in the chamber was fixed at 760 Torr. The measured distributions showed high concentrations around the port set at 10% and high temperatures around the heater blocks set at 125 °C, as expected. When all blocks were set at 125 °C, CH₄ temperature around one heater block was higher than others. The temperatures were confirmed with the thermocouples when CH₄ was streamed at the same conditions.