Quartz Crystal Microbalance Studies of the Plasma-Assisted Etching of Polyimide and Tungsten Thin Films

The etching of polyimide thin films and tungsten thin films has been studied as a function of bias voltage using two quartz crystal microbalances (QCM) installed in a low pressure 13.56 MHz rf plasma system.One of the QCM's is biased (rf bias was used for the polyimide films; de bias was used for the tungsten films) and the other QCM is unbiased.In this way, the influence of energetic positive ion bombardment on etching can be studied.The etching of polyimide is studied in CF4-O2 glow discharges whereas CF4-H2 gas mixtures were used in the etching of tungsten.In the tungsten etching studies, the surfaces were vacuum-transferred to an Auger electron spectrometer for surface analysis.