TRG-OES Measurements of Electron Temperatures During Fluorocarbon Plasma Etching of SiO sub 2 Damage Test Wafers

We report measurements of electron temperatures (T sub e ) during the etching of silicon dioxide damage tester wafers. The high-density plasma feed gases consisted of a mixture of C sub 2 F sub 6 , C sub 4 F sub 8 , Ar, and Ne. T sub e was measured by trace rare gases optical emission spectroscopy. Full emission spectra were recorded with a CCD array detector spectrometer every 0.5s during the full etching process (including stabilization and cleaning steps) for a batch of 44 wafers (22 damage testers and 22 blank Si wafers). Measurements were made as a function of selected variables such as the Ar-to-Ne carrier gas ratio, pressure, and total gas flowrate. As expected, T sub e increased with the fraction of added Ne, but exhibited an unusual pressure dependence, decreasing with decreasing pressure below ~30 mTorr.