To improve the photoresist (PR) etching in inductively coupled plasma (ICP) without the use of bias power, an impedance control unit is connected in series to the bias electrode of the ICP. This impedance control unit consists of an inductor and a variable capacitor to control the impedance of the bias electrode. With the series resonance of the sheath capacitance and inductance of the bias electrode impedance, the current flowing through the bias electrode increases dramatically, resulting in a higher voltage across the sheath and larger ion energy loss. The effect of series resonance on the decrease of electron density, as observed by a Langmuir probe, is illustrated by a global power balance model. As the capacitance approaches the series resonance condition, the larger ion energy leads to an enhanced PR etch rate, and the more uniform profile of the radio frequency plasma potential results in more uniform distributions of ion energy and PR etch rate. Additionally, the variation of the radio frequency plasma potential profile is attributed to the enhanced capacitive electrical field in the ICP. These variation are analysed using an electromagnetic simulation.

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.

Electron energy distribution functions (EEDFs) are measured with varying radio-frequency (RF) power in an oxygen inductive discharge. At a pressure of 10 mTorr, the EEDF has a Maxwellian distribution, and the low-energy (1–5 eV) electron temperature, Te,low, monotonically decreases with RF power. However, at a pressure of 100 mTorr, Te,low increases at low RF power (80–150 W) and decreases at high RF power (150–300 W), and the EEDF has a Druyvesteyn-like distribution. These changes in Te,low are attributed to electron attachment and detachment reactions, which are the main creation and loss reactions of negative ions. To investigate this relationship between Te,low and collisional reactions, the reaction coefficients of several reactions are calculated, and the electronegativity (α) is measured with varying RF power. The EEDF is modified by electron attachment and detachment reactions, which lead to a change in Te,low; this modification of EEDF is supported by calculated reaction coefficients and measured α.

The floating probe method (FPM) applicable for processing plasma diagnostics was developed for the measurement of ion density and electron temperature (J. Appl. Phys. 101 033305). When an AC voltage is applied to a floating probe, harmonic currents are generated due to the nonlinearity of the sheath. The electron temperature and ion density are obtained using the harmonic currents and the voltage across the sheath. However, in the FPM, when the sensing resistance becomes similar to the sheath resistance, iterative calculations must be performed to compensate for the voltage reduction across the sheath due to the sensing resistor. In this paper, the voltage across a DC blocking capacitor is measured to directly obtain the voltage across the sheath. Therefore, it is not necessary to compensate for the voltage reduction across the sheath through iterative calculations. The electron temperature was increasingly overestimated as the capacity of the DC blocking capacitor became smaller. This overestimation was caused by the capacitive load effect and was compensated for using a correction for the second harmonic current. The measured electron temperature and ion density were compared with those from electron energy distribution functions (EEDFs) in an inductively coupled plasma, and they were in good agreement.

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