In Situ Measurement and Analysis of Low Pressure Gas Concentration Distribution Using 70-dB SNR 1,000 Frame-Per-Second Absorption Imaging System

We are developing a 70-dB SNR 1,000 frame-per-second absorption imaging system, and it enables us to visualize gas concentration distribution and its dynamic behavior in a chamber for semiconductor manufacturing. In the steady-state gas flow condition, the spectrometry of NO2 gas shows a good linear relationship between the absorbance and the partial pressure above approximately 0.1 Pa with the system. Such low partial pressure measurement enables the visualization of beginning of jet out of $\text{NO}_{2}/\text{Ar}$ mixed gases from a nozzle. Furthermore, 1,000 frame-per-second imaging enables analyses of the gas velocity distribution and its width.