摘要： We measured methane (CH4) concentration distribution in a semiconductor process chamber by using the computed tomography-tunable diode laser spectroscopy (CT-TDLAS). We designed the CT-TDLAS measurement system with a 32-laser-path. The CH4 concentration distribution was measured by the CT-TDLAS based on the 32 absorption spectra which were collected by scanning the laser wavelength around the CH4 absorption peak of 1653.7 nm. We checked linearity of the measurement, validity of the algorithm, and resolution of the computed tomography (CT) reconstructed distribution. In the algorithm check, we measured a simple concentration distribution generated in a ?ve-fold concentric cylinder. Next, we designed a semiconductor process chamber in which the 32-laser-path was installed. After quantitative evaluations of the CT reconstructed distributions by comparing the simulated results of computational ?uid dynamics, we actually measured the CH4 concentration distribution in the chamber when we streamed 10% CH4 from one of four inlet ports and nitrogen from other three ports into the chamber. The measured distributions were obviously different in accordance with the CH4 inlet location, although all the inlet ports were located cyclic-symmetrically. Those results indicated that the ?ow impedances of the four exhaust holes on the susceptor were different depending their locations.