Abstract

In the Plasma Dry Etching process used in semiconductor manufacturing, trace amounts of moisture in process gases can cause equipment corrosion, and interference with surface reactions, becoming a major factor in reducing device yield. However, spectroscopic methods such as Fourier-Transform Infrared Spectroscopy (FTIR), Non-Dispersive Infrared Spectroscopy (NDIR) have the limitation that accurate quantification of moisture becomes difficult when complex spectral overlaps occur among gas components. In this study for etching gases in which moisture detection is difficult using spectroscopic analysis methods, a technique was developed to quantitatively analyze trace amounts of moisture by applying the Karl Fischer Coulometric method. 10 μmol/mol moisture standard gas certified by the Korea Research Institute of Standards and Science was mixed and injected with semiconductor etching gases, after which the moisture content was measured under various flow rate conditions to derive a calibration curve. Subsequently, the detection limit (D.L.) was determined based on the intercept variation of the straight line obtained from injecting only standard gas. As a result, moisture at the μmol/mol level was detected in CHF3 and C4F8 gases, and it was observed that the measurement precision and reproducibility tended to improve as the gas flow rate increased. This suggests that the Karl Fischer Coulometric method can complement the limitations of conventional spectroscopic techniques and serve as an effective alternative for measuring trace moisture in high-purity semiconductor gases applications. This study is expected to contribute to improving process stability and yield by enhancing the accuracy of moisture control in etching gases.

Graphical Abstract