A novel <i>ex situ</i> diagnostic technique for characterizing harmonics in radio frequency discharges

Rawat, Arti; Ganguli, A.; Narayanan, R.; Tarey, R. D.

doi:10.1063/5.0009015

Cited by 3 publications

(1 citation statement)

References 29 publications

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“…Invasive methods involve physical contact with the plasma, such as with a Langmuir probe, which can limit its application [ 32 , 36 , 37 , 38 ]. Recently, noninvasive methods, such as directional coupler, have been studied and applied to investigate plasma processes [ 33 , 39 , 40 , 41 ]. These methods do not require physical contact with plasma and can provide information on harmonics without affecting plasma distribution.…”

Section: Introductionmentioning

confidence: 99%

Diagnosing Time-Varying Harmonics in Low-k Oxide Thin Film (SiOF) Deposition by Using HDP CVD

Park

Liu

Lee

et al. 2023

Sensors

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This study identified time-varying harmonic characteristics in a high-density plasma (HDP) chemical vapor deposition (CVD) chamber by depositing low-k oxide (SiOF). The characteristics of harmonics are caused by the nonlinear Lorentz force and the nonlinear nature of the sheath. In this study, a noninvasive directional coupler was used to collect harmonic power in the forward and reverse directions, which were low frequency (LF) and high bias radio frequency (RF). The intensity of the 2nd and 3rd harmonics responded to the LF power, pressure, and gas flow rate introduced for plasma generation. Meanwhile, the intensity of the 6th harmonic responded to the oxygen fraction in the transition step. The intensity of the 7th (forward) and 10th (in reverse) harmonic of the bias RF power depended on the underlying layers (silicon rich oxide (SRO) and undoped silicate glass (USG)) and the deposition of the SiOF layer. In particular, the 10th (reverse) harmonic of the bias RF power was identified using electrodynamics in a double capacitor model of the plasma sheath and the deposited dielectric material. The plasma-induced electronic charging effect on the deposited film resulted in the time-varying characteristic of the 10th harmonic (in reverse) of the bias RF power. The wafer-to-wafer consistency and stability of the time-varying characteristic were investigated. The findings of this study can be applied to in situ diagnosis of SiOF thin film deposition and optimization of the deposition process.

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Section: Introductionmentioning

confidence: 99%

Diagnosing Time-Varying Harmonics in Low-k Oxide Thin Film (SiOF) Deposition by Using HDP CVD

Park

Liu

Lee

et al. 2023

Sensors

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A joint calibration technique for improving measurement accuracy of voltage and current probes during synchronous operation for RF-based plasma devices

Mahreen

Ganguli

Prakash

et al. 2022

Review of Scientific Instruments

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This paper presents a joint calibration scheme for voltage (V) and current (I) probes that helps accurately resolve the voltage–current phase differences even when the difference is very close to 90°. The latter has been a major issue with V–I probes when used with miniature RF plasma devices such as the atmospheric pressure plasma jet (APPJ). Since the impedance of such miniature devices is predominantly capacitive, the phase difference between the voltage and current signals is very nearly 90°. It turns out, however, that when V–I probes are used with such devices without joint calibration, these frequently yield phase shifts over 90°. Also, since the power absorption is proportional to the resistive part of the impedance, it becomes very sensitive to the phase difference when it is close to [Formula: see text]. Thus, it is important to be able to accurately resolve the phases. Post-calibration, V–I probes would be indispensable for the electrical characterization of APPJs for determining the average RF power P av, plasma impedance Z p, etc. Typical post-calibration V–I data yield Z p [Formula: see text] 93.6 − j 1139 Ω (81.5 − j 1173 Ω) at P av [Formula: see text] ([Formula: see text] for helium (argon) gas.

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A new J.E probe for measurement of spatial profiles of power absorption in RF produced plasma

Rawat

Ganguli

Narayanan

et al. 2023

Review of Scientific Instruments

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This paper reports an indigenously developed probe for the measurement of spatial profiles of the absorbed/generated RF power density Pabs (W/m3) in RF discharges. The technique utilizes a calibrated current (J) probe based on the Rogowski coil principle and an electric field (E) probe based on capacitive coupling, both integrated into a single probe called the J.E probe. Various aspects of the probe, such as its design, fabrication, calibration, and limitations, were resolved before it was used for obtaining axial profiles of RF power absorption/generation. Also presented are the first experimental results for the absorbed power density profiles at the fundamental (13.56 MHz) and harmonic (27.12 MHz) along the length of a capacitively coupled discharge. The axial scans between the powered and grounded electrode were taken at different argon gas pressures (10–800 mTorr) at a fixed RF power of 10 W. Detailed analysis of the results shows that even for systems with large electrode gaps, i.e., plasmas with long bulk plasma regions, practically all the fundamental power is absorbed in a narrow edge region near the powered electrode, irrespective of the pressure. Absorption is high near the RF electrode since the RF fields peak in this region. Another important conclusion is that stochastic absorption of the fundamental and harmonic generation proceeds fairly efficiently in the vicinity of the powered electrode even at high pressures. It may be mentioned that the probe technique introduced here is the first of its kind, and although there is considerable scope for miniaturization, it has, nonetheless, provided some key insights into the nature of RF power absorption in capacitive discharges.

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A novel ex situ diagnostic technique for characterizing harmonics in radio frequency discharges

Cited by 3 publications

References 29 publications

Diagnosing Time-Varying Harmonics in Low-k Oxide Thin Film (SiOF) Deposition by Using HDP CVD

Diagnosing Time-Varying Harmonics in Low-k Oxide Thin Film (SiOF) Deposition by Using HDP CVD

A joint calibration technique for improving measurement accuracy of voltage and current probes during synchronous operation for RF-based plasma devices

A new J.E probe for measurement of spatial profiles of power absorption in RF produced plasma

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