Measurements of time varying plasma potential, temperature, and density in a 13.56 MHz radio‐frequency discharge

Argon plasma measurements were conducted in a commercial capacitively coupled etcher operating at 400 mTorr with 60‐W coupled power at 13.56 MHz. Time varying floating potential was measured using a capacitively coupled probe which uses a capacitive voltage divider and a field effect transistor buffer amplifier. Average floating potential was obtained from a high‐input‐impedance Langmuir probe. The floating potential was found to be sinusoidal, [21 sin(wt)−4]V±1.5 V, with a maximum of 17±1.5 V and a minimum of −25±1.5 V. From these data and the use of a low‐input‐impedance Langmuir probe, a calibrated instantaneous I–V characteristic is used to obtain plasma potential and electron temperature. Plasma potential was found to be sinusoidal, [21 sin(wt)+30]V±1.6 V, with a maximum of 51±1.6 V and a minimum of 9±1.6 V. Electron temperatures were 6.58±0.19 eV at maximum plasma potential and 6.49±0.19 eV at minimum plasma potential. The electron density for this experiment was determined to be 1.48±0.83×1010 elec...