Transient plasma potential in pulsed dual frequency inductively coupled plasmas and effect of substrate biasing

Mishra, Anurag; Yeom, Geun Young

doi:10.1063/1.4961940

Cited by 3 publications

(1 citation statement)

References 38 publications

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“…In the investigations of pulsed discharge, the time evolution curve of plasma parameters (electron density, electron temperature, and relative light intensity) often has the phenomenon of overshoot at the initial pulse, [11][12][13][14][15] i.e., they first increase to maximum and then drops to a stable value. Sirse et al [16] observed overshoot phenomenon during pulse off when measuring electron density in oxygen plasma, and established a qualitative model to explain the variation trend of negative ion density and temperature.…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal measurements of overshoot phenomenon in pulsed inductively coupled discharge*

Lv¹,

Gao²,

Zhang³

et al. 2021

Chinese Phys. B

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Pulse inductively coupled plasma has been widely used in the microelectronics industry, but the existence of overshoot phenomenon may affect the uniformity of plasma and generate high-energy ions, which could damage the chip. The overshoot phenomenon at various spatial locations in pulsed inductively coupled Ar and Ar/CF4 discharges is studied in this work. The electron density, effective electron temperature, relative light intensity, and electron energy probability function (EEPF) are measured by using a time-resolved Langmuir probe and an optical probe, as a function of axial and radial locations. At the initial stage of pulse, both electron density and relative light intensity exhibit overshoot phenomenon, i.e., they first increase to a peak value and then decrease to a convergent value. The overshoot phenomenon gradually decays, when the probe moves away from the coils. Meanwhile, a delay appears in the variation of the electron densities, and the effective electron temperature decreases, which may be related to the reduced strength of electric field at a distance, and the consequent fewer high-energy electrons, inducing limited ionization and excitation rate. The overshoot phenomenon gradually disappears and the electron density decreases, when the probe moves away from reactor centre. In Ar/CF4 discharge, the overshoot phenomenon of electron density is weaker than that in the Ar discharge, and the plasma reaches a steady density within a much shorter time, which is probably due to the more ionization channels and lower ionization thresholds in the Ar/CF4 plasma.

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Section: Introductionmentioning

confidence: 99%

Spatio-temporal measurements of overshoot phenomenon in pulsed inductively coupled discharge*

Lv¹,

Gao²,

Zhang³

et al. 2021

Chinese Phys. B

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Modulating power delivery in a pulsed ICP discharge via the incorporation of negative feedback mechanisms

Smith

Nam

Bae

et al. 2021

Journal of Applied Physics

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Inductively coupled plasmas driven by pulsed RF power have been used by the semiconductor industry for decades as they offer numerous advantages compared to continuous mode discharges. Current state-of-the-art global models characterize the plasma under conditions where power delivery is user defined and typically constant. This work details the development of an integrated global plasma-circuit model, which couples a transient plasma model with a broader circuit model that captures the behavior of the power delivery system. The transient response of electron density ne and the magnitude of the delivered and reflected power is captured for the duration of a pulse event. The plasma model incorporates negative feedback mechanisms that enhance the magnitude of reflected power in the early ON-cycle. These feedback mechanisms include a skin depth-dependent derivation of plasma impedance and a generalized electron energy distribution function. These mechanisms decrease the rate of power delivery and dnedt in the early power on cycle. Data taken in the global plasma-circuit model was benchmarked to hairpin probe measurements that were taken on the NC state’s inductively coupled argon oxygen system. Experimental data were taken using a working gas of high purity argon at pressures ranging from 2.67 to 6.67 Pa, and center point electron densities were measured in the range of 109–1010cm−3.

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Diagnosis of capacitively coupled plasma driven by pulse-modulated 27.12 MHz by using an emissive probe

Zhou¹,

Cao²,

Xiao–Ping³

et al. 2020

Acta Phys. Sin.

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There are several methods of diagnosing the capacitively coupled plasma, such as microwave resonance probe, Langmuir probe, etc, but methods like microwave resonance probe are mainly used for determining the electron density. Moreover, in the diagnosing of plasma potential, the emissive probe has a higher accuracy than the traditional electrostatic probes, and it can directly monitor the potential in real time. However, in the existing work, emissive probe is mostly applied to the diagnosis of plasmas with high density or plasmas modulated by pulsed dual frequency (one of the radio frequency sources is modulated), the experiments on the emissive probe diagonising plasma excited by a pulsed single frequency are quite rare. In this paper, the temporal evolution of the plasma potential and electron temperature with input power and pressure in a pulsed 27.12 MHz capacitively coupled argon plasma are investigated by using an emissive probe operated in floating point mode. The plasma potential is obtained by measuring emissive probe potential under a strongly heated condition, while the electron temperature is estimated from the potential difference between the emissive probe under strongly heating and cold conditions. The measurements show that as the pulse is on, the plasma potential will rise rapidly and become saturated within 300 μs due to the requirement for neutrality condition; while the pulse is off, the plasma potential undergoes a rapid decline and then stabilizes. An overshoot for the electron temperature occurs as the onset of the pulse, because of the influence of radio frequency electric field and residual electrons from the last pulse; during the pulse-off time, rapid loss of high-energy electrons causes the electron temperature to rapidly drops to 0.45 eV within 300 μs, then it rises slightly, which is related to the electrons emitted by the probe. The plasma potential basically has a linear dependence on the change of input power and pressure for the pulse-on and pulse-off time; and the input power has a greater influence on the difference between the overshoot electron temperature and the steady state electron temperature during the pulse-on time. Corresponding explanations are given for the temporal evolution of plasma potential and electron temperature in different pulse stages and under different discharge conditions.

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Transient plasma potential in pulsed dual frequency inductively coupled plasmas and effect of substrate biasing

Cited by 3 publications

References 38 publications

Spatio-temporal measurements of overshoot phenomenon in pulsed inductively coupled discharge*

Spatio-temporal measurements of overshoot phenomenon in pulsed inductively coupled discharge*

Modulating power delivery in a pulsed ICP discharge via the incorporation of negative feedback mechanisms

Diagnosis of capacitively coupled plasma driven by pulse-modulated 27.12 MHz by using an emissive probe

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