Behavior of fluorocarbon species near temperature controlled and radio frequency biased metal plate in C4F8 plasma

Abstract

Variations of fluorocarbon species were investigated in the vicinity of metal stage that was installed in C4F8 inductively coupled plasma system with the parameters such as temperature of the stage, distance from the stage, gas residence time, and rf bias voltage applied to the stage. Quadrupole mass analyzer and appearance mass spectrometry have been used for the measurement of fluorocarbon ions, radicals. Densities of all radicals increased with the increase of stage temperature and the decrease of the gap distance between stage and detection point. On the other side, the concentrations of fluorocarbon ions decreased slightly when the stage temperature went down. It has been investigated that the density variation of the radicals dependent on the stage temperature could be controlled with gas residence time. It is considered that the balance between pumping loss rate and surface loss rate has a responsibility for the residence time effects on radical density variations. Finally, constant amounts of radicals were desorbed from the stage along with discharge time when we applied rf bias to the stage. All of the experimental results suggest that dielectric etching chamber should be designed on the basis of the understanding on plasma–wall interaction.