Surface analysis for selective SiO2 etching by reflectance photoelastic modulated fourier transform infrared spectroscopy

Photoelastic modulated fourier transform infrared (PEM FTIR) spectroscopy h as been used to study the bonding structure and compositions of fluorocarbo n films generated during etching with CHF3/CO surface wave plasma (SWP). Th e C=C (stretching vibration mode at 1600 cm(-1)), C-C (940 cm(-1)), C-F (10 32, 1164, 1260,1291 cm(-1)), =C-H (780 cm(-1)) and C=O (1790 cm(-1)) peaks on the polymer films were identified using reflectance PEM FTIR. In additio n to the peak assignment, the C-F spectra were fitted to three peaks-1280, 1250, 1200 cm(-1), with Gaussian splitting, respectively. Comparing the etc hing results with the variation of FTIR spectra, it was found that the sele ctivity of SiO2 to poly-Si and photoresist with CO mixing ratio to CHF3 is correlated to the area ratio of [C=C]/[C-F] and [C=C]/[C=O]. The XPS result was also compared to reflectance PEM FTIR data to reveal the availability of reflectance REM FTIR application. It was confirmed that there existed a good agreement between PEM FTIR and XPS data. When we integrated all the re sults from PEM FTIR, XPS and optical emission spectroscopy (OES), we found that the element of the C=C bond on the polymer surface played an important role as an etch inhibitor. The reflectance PEM FTIR measurement on the etc hed surface is considered to lead to an understanding the properties of pol ymer films generated during oxide etching.