A method for measuring plasma parameters and dielectric film thickness by analyzing transient voltages for deposition plasma processing monitoring

Abstract

An electrical method is proposed to measure the dielectric lm thickness, electron temperature, and plasma density for deposition plasmas. In this method, a square voltage is applied to a at probe coated with a dielectric lm, and the transient voltage of a series capacitor connected to the probe is measured. The thickness of the dielectric lm is obtained from the transient voltage because the applied voltage is divided across the dielectric lm and the series capacitor. The deposited dielectric lm causes a change in transient voltage of the series capacitor. A circuit model with a nonlinear sheath, a series capacitor, and the dielectric lms is suggested to obtain plasma density and electron temperature. The time response of transient voltage is related to plasma density, electron temperature and total capacitance of the series capacitor and the dielectric lm. Two square voltages with different amplitudes were applied to measure plasma density and electron temperature. Experiments were conducted in inductively coupled plasma. Various capacitors were used to replace the dielectric lms, and a at probe coated with Al 2 O 3 was used to verify the measurement of dielectric lm thickness, showing the high accuracy of our method. In addition, the electron temperature from our method is in good agreement with that from electron energy distribution functions, and the plasma density is in good agreement with that from orbital motion limited theory. Therefore, this method would be useful for monitoring plasma parameters and deposited lm thickness in industrial plasma processing.

Improvement of the floating probe method for ion density and electron temperature measurement without compensation due to voltage reduction across the sheath

“…Hwang et al measured the electron temperature using the floating potential difference by applying AC voltage to the probe tip and the ion density using the first harmonic current [7]. In recent work, we suggested the method of applying the square voltages to the probe tip and analysed the transient voltage of the capacitor connected in series to the probe for obtaining the electron temperature and ion density [8,9].…”