Curling probe measurement of a large-volume pulsed plasma with surface magnetic confinement

Abstract

A curling probe (CP) based on microwave resonance is applied to the measurement of electron density in a pulsed DC glow discharge under surface magnetic confinement (SMC) provided by a number of permanent magnets on a chamber wall. Owing to the SMC effects, a 1 m scale large-volume plasma is generated by a relatively low voltage (~1 kV) at low pressure (~1 Pa) in various gases (Ar, CH 4 , and C 2 H 2 ). Temporal variation of the electron density is measured for pulse frequency f = 0.5-25 kHz for various discharge-on times (T ON ) with a high resolution time (~0.2 µs), using the on-point mode. In general, the electron density starts to increase at time t = 0 after turn-on of the discharge voltage, reaches peak density at t = T ON , and then decreases after turn-off. The peak electron density is observed to increase with the pulse frequency f for constant T ON owing to the residual plasma. This dependence is successfully formulated using a semi-empirical model. The spatio-temporal evolution of the cathode sheath in the pulsed discharge is revealed by a 1 m long movable CP. The measured thickness of the high-voltage cathode fall in a steady state coincides with the value of the so-called Child-Langmuir sheath.

The curling probe: A numerical and experimental study. Application to the electron density measurements in an ECR plasma thruster

“…The hairpin has been since revisited, with dc-biased version proposed in an unpublished work [12], and different coupling modes and operating modes [13]. The length of the antenna arm, which depends on the working frequency, limits the spatial resolution and can disturb the measurements [14].…”

“…Recently, the curling probe has been applied to the characterization of reactive plasmas for industrial processing [14,[19][20][21], where LP measurements were found to be difficult to use [19]. Time-resolved measurements of the electron density have been performed in a pulsed DC discharge in various gases under surface magnetic confinement [14]. Densities as low as 10 9 cm −3 have been measured with a 100 mm-long and 16 mm in diameter CP coated with Alumina (Al 2 O 3 ).…”

Recent innovations in microwave probes for reactive plasma diagnostics

“…This technique was successfully applied to the measurement of electron density in a pulsed DC glow discharge under surface magnetic confinement (SMC). 45) Owing to the SMC effects, a 1 m scale large-volume plasma is generated by a relatively low voltage (∼1 kV) at low pressure (∼1 Pa) in various gases (Ar, CH 4 and C 2 H 2 ). Figure 34 presents (a) the cross-section of the grounded discharge chamber with the cathode and a movable CP and (b) the discharge voltage applied to the cathode with measuring times (τ = 50 and 400 μs) and (c) radial distributions of electron density measured at τ = 50 and 400 μs.…”

Progress and perspectives in dry processes for leading-edge manufacturing of devices: toward intelligent processes and virtual product development

“…170 reported applications of process metrology based on optical critical dimension (CD) integrated metrology for gate etching. The gate CD variation was reduced by [129][130][131][132][133] feedforward or closed-loop feedforward/feedback control. The wafer stage temperature and etching time were used as the controllable variables.…”