Capacitive Radio Frequency Research Articles

The preliminary study of etching characteristics of atmospheric pressure trifluoromethane plasma jet etching

Abstract The capacitive coupling radio frequency atmospheric pressure plasma jet for silicon etching, through the carrier gas carrying trifluoromethane gas, varying the gas flow rate for plasma etching. It finds the impact of varying gas flow rates on plasma etching and analyzes the resulting two-dimensional and three-dimensional surface topographies using surface profilometer. Experimental findings indicate that at a trifluoromethane flow rate of 250 sccm and a working distance of 6 mm, the etching rate achieves 38.7 μm/min. Notably, the research emphasizes the crucial role of trifluoromethane (CHF3) gas in plasma etching, highlighting its fluorocarbon ratio and chemical structure as primary factors influencing the etching process on monocrystalline silicon. Ultimately, the study proposes a methodology involving trifluoromethane gas for silicon wafer etching, enabling the transformation of micro-patterns onto crystalline silicon using a mask. This research contributes valuable insights into optimizing plasma etching techniques for microfabrication processes in semiconductor technology.

Effect of capacitive radiofrequency on adipose tissue of the abdominal region

Objectives: To evaluate histological changes in the adipose tissue after capacitive radiofrequency (RF) stimulation (thermotherapy). Methods: This is a case series study (n=5). The volunteers received in the right infraumbilical abdominal region a single application of capacitive RF (BTL-6000 TR-Therapy Pro®), with a frequency of 480 to 520KHz, power of 150 W for 10 minutes (2 minutes per head area, 50mm in diameter). The epidermal temperature was above 40°C, and, the left side was used as control. After 30 days, an average, tissue sample was collected for histological analysis and stained with hematoxylin and eosin. Statistical analysis was performed using the SPSS program (version 20), with a significance level of 95%, and the adipocyte count was performed using Image J®. This study was registered with the XXXX Ethics Committee n. 3,461,688, Jul/12/19 and, the number of clinical trial registration was NCT04182542. Results: The number of adipocytes on the treated side was 41.2 ± 2.0 per field and, in the control side was 36.6 ± 2.0 per field, with a significant difference (p=0.009), because of the size of adipocytes being smaller on the side treated. Conclusion: Radiofrequency can lead to morphological changes in adipocytes in the abdominal region with an important reduction in their size.

Short-term effects of 448 kilohertz radiofrequency stimulation on plantar fascia measured by quantitative ultrasound elastography and thermography on active healthy subjects: an open controlled clinical trial

Objective: This study is an open clinical trial. The aim of this study was to show the changes that occur in the viscoelastic properties of the plantar fascia (twenty healthy volunteers) measured by SEL and the changes in the plantar fascia temperature measured by thermography after the application of a 448 kHz capacitive resistive monopolar radiofrequency (CRMR) in active healthy subjects immediately after treatment and at the 1-week follow-up. Methods: Furthermore, to analyze if an intervention with 448 kHz CRMR in the plantar fascia of the dominant lower limb produces a thermal response in the plantar fascia of the non-dominant lower limb. The final objective was to analyze the level of association between the viscoelastic properties of the PF and the temperature before and after the intervention with 448 kHz CRMR. Results: Our results showed that a temperature change, which was measured by thermography, occurred in the plantar fascia after a single intervention (T0-T1) and at the 1-week follow up (T1-T2). Conclusion: However, no changes were found in the viscoelastic properties of the plantar fascia after the intervention or at the 1-week follow up. This is the first study to investigate changes in both plantar fascia viscoelastic properties and in plantar fascia temperature after a radiofrequency intervention.

Effects of high-frequency hyperthermia on the elastic modulus of the lumbar muscle in female athletes with low back pain: A randomized crossover trial.

To investigate the effects of capacitive and resistive monopolar radiofrequency (CRMF) on the shear elastic modulus of the multifidus and erector spinae muscles in female athletes with low back pain (LBP) and a history of LBP. Randomized crossover trial. Academic institution. Twenty female university athletes with LBP or a history of LBP were included. All participants received CRMF, hotpack, and sham (CRMF without power) in a random order on the right side of the lumbar region. More than 2 days were allocated between the experiments to eliminate any residual effects. The shear elastic moduli of the right multifidus and erector spinae were evaluated in the prone (rest) position while sitting with 35° trunk flexion (stretched) using shear wave ultrasound imaging equipment. The moduli were measured before, immediately after, and 30 minutes after the intervention. Repeated-measures 2-way analysis of variance and post hoc analysis showed that the moduli of the CRMF group were significantly lower than those of the sham group in the stretched position immediately after intervention (P = .045). This difference diminished 30 minutes after the intervention (P = .920). CRMF can be used to reduce the shear elastic modulus of the multifidus muscle in the short term. Further studies are warranted to determine how to provide longer effects. None.

Advancement of Langmuir probe-based laser photo-detachment technique for negative ion density measurement in a high-power helicon plasma source.

In the pursuit of precise diagnostics for measuring negative ion density in a helicon plasma source (HPS), a new approach utilizing a radio frequency (RF) broadband transformer-based Langmuir probe is developed specifically for laser photo-detachment (LPD) analysis. This inductively coupled LPD technique is useful for high power RF systems in which capacitive RF noise is in the same scale as the pulsed photo-detachment signal. The signal acquired by this transformer-based probe is compared against the conventional Langmuir probe-based LPD technique, revealing a remarkable enhancement in signal fidelity through an improved signal-to-noise ratio (SNR) achieved by the RF broadband transformer methodology. In addition, the localized hydrogen negative ion density measurements obtained through this probe are harmoniously aligned with the line-averaged negative ion density derived from the cavity ringdown spectroscopy (CRDS) technique. These concurrence measurements highlight the RF broadband transformer-based approach's accuracy in capturing localized negative ion density during helicon mode operation in an HPS setup. Furthermore, the correlation of negative ion density values with RF input exhibits a consistent trend in tandem with background plasma density. Notably, both CRDS and LPD measurements ascertain negative ion densities ranging from ∼5 to 6×1016m-3 under an RF power of 500-700W and a pressure of 8 × 10-3mbar, all under the influence of a 55G axial magnetic field. These specific parameters represent the optimal operational configuration for effective negative ion production with the present experimental HPS setup. Due to its better SNR, the RF broadband transformer-based Langmuir probe emerges as a useful tool for LPD diagnostics, particularly in the presence of pervasive RF noise.

Vasodilatory Peripheral Response and Pain Levels following Radiofrequency Stressor Application in Women with Fibromyalgia.

Fibromyalgia (FM) is a syndrome of unknown pathogenesis that presents, among other symptoms, chronic widespread musculoskeletal pain. This study aims to analyze the effects of radiofrequency on core body temperature and the peripheral temperature of the dorsal surfaces and palms of the hands and its association with pain levels in patients with FM. A case-control observational study was conducted with a total of twenty-nine women diagnosed with FM and seventeen healthy women. Capacitive monopolar radiofrequency was applied to the palms of the hands using the Biotronic Advance Develops device. Peripheral hand temperature was analyzed using a thermographic camera, and core body temperature was analyzed with an infrared scanner. Pressure pain thresholds (PPTs) and electrical pain were recorded with an algometer and a Pain Matcher device, respectively. A significant decrease was observed in women with FM in pain electrical threshold (95% CI [0.01-3.56], p = 0.049), electrical pain (95% CI [2.87-10.43], p = 0.002), dominant supraspinatus PPT (95% CI [0.04-0.52], p = 0.023), non-dominant supraspinatus PPT (95% CI [0.03-0.60], p = 0.029), and non-dominant tibial PPT (95% CI [0.05-0.89], p = 0.031). Women with FM have increased hypersensitivity to pain as well as increased peripheral temperature after exposure to a thermal stimulus, such as radiofrequency, which could indicate disorders of their neurovascular response.

Loss of subcutaneous fat in 20 patients, both sexes, using a second-generation TECAR device of 1.240 Watts and results analyzed with magnetic resonance.

Body contouring and abdominal fat loss without surgery are increasingly used technique. In a study in pigs, it is noted that both capacitive and resistive radiofrequency stimulation reduced subcutaneous fat. One human study demonstrated a loss of 2.90 cm in waist diameter. Second-generation TECAR (Acronym for Transfer Electric Capacitive and Resistive) device with 4 channels, 200 cm2 work area per channel, and high power (1240 W), regulates body energy input by measuring absorption in the body and adjusting the power for 80 min at 50°C. To evaluate the loss of subcutaneous fat, this magnitude was measured in grams and centimeters throughout the abdomen by MRI before and after each treatment. We have studied 25 patients, 13 women and 12 men with a mean age of 49 years. All patients had their waist diameter measured and an MRI performed before and after 10 continuous sessions except Saturday and Sunday, over 2 weeks. Additionally, a lipid profile was performed on the same day of the study and at the end of it. The study was approved by the Ethics Committee. Waist diameter decreased by 5.5 cm, these differences being statistically significant (p = 0.000). Subcutaneous fat measured by MRI in cm decreased by 784 cm (p = 0.000). In grams, it decreased 808.7 g (p = 0.000). In the lipid profile, all the values decreased, but they were not statistically significant. The use of this second generation of TECAR equipment at 1 MHz decreases the waist diameter by more than 5 cm and leads to the loss of more than 800 grams of subcutaneous fat in 12 days. It is a method without risks or side effects, well tolerated, and an alternative for those patients who do not want to go to the operating room.

Similarity laws for two-dimensional simulations of low-pressure capacitively coupled radio-frequency discharges

Similarity laws (SLs) for low-pressure capacitive radio-frequency plasmas are generalized from one- to two-dimensional (2D) frameworks based on kinetic particle-in-cell simulations. Fundamental discharge parameters, such as the 2D distributions of electron densities and electric fields, are examined to assess the applicability of SLs to such discharges. The discharge characteristics are found to remain invariant when external control parameters are changed according to SLs. Even under conditions where nonlinear electron resonance heating caused by the self-excitation of the plasma series resonance due to the geometric reactor asymmetry plays an important role, the electron kinetics are shown to be invariant. Moreover, the validity of SLs for the ion dynamics is demonstrated. The results advance the applicability of SLs to a 2D cylindrical reactor geometry with azimuthal symmetry, indicating broad application prospects in practice.

Ultrabroadband (DC–80 GHz) RF MEMS DC/capacitive load shunt switch

AbstractThis study presents the design and fabrication of a novel direct current (DC)/capacitive radio frequency (RF) Micro‐Electro‐Mechanical Systems (MEMS) switch in the ultrabroadband range from DC to 80 GHz. This proposed RF MEMS switch consists of two arms, with one arm providing a DC loading state (), whereas the second arm provides a capacitive loading state () to the ground when pull‐in voltage is applied. Insertion loss less than 1.85 dB and return loss better than 10 dB are achieved in the OFF state () from DC to 80 GHz (no pull‐in voltage is applied). Due to the novel design topology, this switch can act as a DC‐only switch (0–17 GHz) that provides isolation better than 25 dB during the state. A capacitive‐only switch (48–80 GHz) provides isolation better than 17 dB. This proposed structure can act as either DC(S1) or a capacitive () switch (17–48 GHz) and provides isolation better than 10 dB in either state. This proposed switch finds its best application in reconfigurable circuits like phase shifters due to switching between DC and capacitive loading during the On state from 17 to 48 GHz. The proposed switch's measured pull‐in and lift‐off voltages are 3.5 and 2.85 V, respectively.

Transition in radio frequency gas breakdown with a transverse magnetic field

This paper presents the quantification of gas breakdown voltages in low-pressure argon capacitive radio frequency (rf) discharges in the presence of an external transverse magnetic field via fully kinetic particle-in-cell/Monte Carlo collision simulations. It is found that as the magnetic field increases, the left branch of the breakdown curve, a double-valued rf breakdown voltage regime, shifts toward a lower-pressure region. A split of the breakdown curve into lower and upper branches occurs when the external magnetic field rises to a critical value. The observed abrupt transition of rf breakdown behaviors can be understood based on the electron kinetics behaviors, with the consideration of the enhanced ionization and electron confinement induced by drift motions. An improved analytical model is developed, which can estimate the critical magnetic field required for the occurrence of the transition.

Similarity-based scaling networks for capacitive radio frequency discharge plasmas

We demonstrate similarity-based scaling networks for capacitive radio frequency (RF) plasmas, which extensively correlate discharge characteristics under varied conditions, incorporating the transition from original to similarity states. Based on fully kinetic particle-in-cell simulations, similar RF discharges in argon are demonstrated with three external control parameters (gas pressure, gap distance, and driving frequency) simultaneously tuned. A complete set of scaling pathways regarding fundamental discharge parameters is obtained, from which each plasma state finds its neighboring node with only one control parameter tuned. The results from this study provide a promising strategy for plasma multi-parameter mapping, enabling effective cross-comparisons, prediction, and manipulation of RF discharge plasmas.

Parallel Contactless Transmission of Power and Rotor Temperature of Electrical Machines via Magnetically-Coupled Resonance and Capacitive Radio Frequency

Over-temperature of the rotor may cause a series of insulation deterioration of electrical machines. In severe cases, it can lead to insulation failure and even faults, such as broken rotor bars and end ring fracture. The temperature online monitoring can effectively avoid the aforementioned insulation failure; however, the conventional temperature measurement by embedded sensors is difficult to utilize due to the power and data transmission of sensors at the rotor side. This paper proposes a contactless strategy to supply power and send rotor temperature data between the stator and rotor sides of electrical machines. With the proposed method, contactless power transfer is realized by means of magnetically-coupled resonance, while the data signal is transferred by capacitive radio frequency (RF) technology. An experimental prototype was developed and installed on a 22-kW induction motor. The results show that the embedded sensors are contactless powered effectively. At the same time clear temperature data signal can be received on the stator side without filtering, and rotor temperature can be monitored in real-time accurately.

Resonant electron confinement and sheath expansion heating in magnetized capacitive oxygen discharges

In weakly magnetized capacitive radio frequency (RF) plasmas electrons accelerated into the plasma bulk by the expanding RF boundary sheath at one electrode can be returned to this electrode due to their gyromotion around an externally applied magnetic field oriented parallel to the electrodes. If the driving frequency and magnetic field are chosen so that the electron cyclotron frequency, ω ce, equals half of the driving RF, ω rf, such energetic beam electrons will be returned to the sheath during its expansion phase and, thus, will be confined and heated resonantly. This magnetized RF sheath resonance (MRSR) effect is studied based on kinetic particle-in-cell simulations in weakly magnetized capacitively coupled oxygen plasmas. In comparison with electropositive argon plasmas, this resonance mechanism is found to be affected strongly by the electronegativity of oxygen discharges. In the unmagnetized case, low-pressure capacitive oxygen discharges operate in an electropositive mode, where nonlinear high-frequency sheath oscillations play an important role similar to previous observations in electropositive discharges with low electron densities. If the resonance condition is fulfilled (), the discharge efficiency is enhanced due to the MRSR effects, resulting in an increase in plasma density. Our numerical results demonstrate that this resonance effect is particularly efficient at low pressure and low electronegativity. However, in strongly electronegative discharges, the time it takes a typical resonant electron to return to the expanding sheath edge is found to be affected by drift and ambipolar electric fields in the plasma bulk, which cause a deviation from the resonance condition, resulting in a reduction of this type of resonance effect.

Scale-invariant resonance characteristics in magnetized capacitive radio frequency plasmas

Resonance mechanisms have been found to be essential for the generation of high-density rf plasmas at low pressures, in which electrons can be continuously accelerated through multiple interactions with the oscillating rf sheaths. In this work, we report the scale-invariant resonance mechanisms, such as bounce resonance heating and plasma series resonance, in low-pressure capacitive rf plasmas in the presence of an external magnetic field. The generation conditions for the resonance mechanisms are determined via fully kinetic simulations. It is found that the resonance dynamical properties of single-frequency plasmas (e.g., a double-peak electron density vs magnetic field curve) can be exactly replicated at different scales when three combined control parameters, i.e., the reduced gap distance pd (pressure × distance), reduced driving frequency f/p (frequency divided by pressure), and reduced magnetic field B/p (magnetic field divided by pressure), are kept constant. The similarity relations for the electron density and electron power absorption in magnetized rf plasmas are numerically confirmed. Furthermore, the similarity and scale-invariant resonance characteristics are elucidated through the scaling of the Boltzmann equation with collisional terms for weakly ionized rf plasmas with a magnetic field, which is proven to be theoretically exact.

Research of Electromagnetic Parameters of the Radio-Frequency Micromechanical Switch Designed for Operation in 5G Transceiver Systems

This article presents the results of an experimental study of the electromagnetic parameters (scattering parameters) of a manufactured experimental sample of a capacitive single-pole single-throw radio-frequency micromechanical switch with an electrostatic activation mechanism designed to operate in the transceiver radio-modules of 5G mobile networks in the frequency range NR FR1, namely at a central resonant electrical frequency of 3,6 GHz. The effective operating frequency range of the developed and manufactured experimental sample of a radio-frequency micromechanical switch is the S-frequency range. The basis for the development of the presented experimental sample is the developed methodology for designing capacitive radio-frequency micromechanical switches with an electrostatic activation mechanism.

Electron dynamics in planar radio frequency magnetron plasmas: III. Comparison of experimental investigations of power absorption dynamics to simulation results

In magnetized capacitively coupled radio-frequency (RF) discharges operated at low pressure the influence of the magnetic flux density on discharge properties has been studied recently both by experimental investigations and in simulations. It was found that the magnetic asymmetry effect allows for a control of the DC self-bias and the ion energy distribution by tuning the magnetic field strength. In this study, we focus on experimental investigations of the electron power absorption dynamics in the presence of a magnetron-like magnetic field configuration in a low pressure capacitive RF discharge operated in argon. Phase resolved optical emission spectroscopy measurements provide insights into the electron dynamics on a nanosecond-timescale. The magnetic flux density and the neutral gas pressure are found to strongly alter these dynamics. For specific conditions energetic electrons are efficiently trapped by the magnetic field in a region close to the powered electrode, serving as the target surface. Depending on the magnetic field strength an electric field reversal is observed that leads to a further acceleration of electrons during the sheath collapse. These findings are supported by two-dimensional particle in cell simulations that yield deeper insights into the discharge dynamics.

Impact of TECAR therapy on post-natal rectus diastasis: A randomized trial

Background. Rectus diastasis is a common problem affecting postpartum mothers. It decreases the integrity as well as functional strength of the abdominal wall, and causes low back pain and pelvic instability Objective. To examine how TECAR therapy (monopolar capacitive resistance radiofrequency of 448 KHz) affects rectus diastasis in postpartum women. Design. A prospective randomized controlled trial. Setting. Outpatient physical therapy clinic, Kafr El Sheikh University. Methods. Forty postnatal women having diastasis recti abdominis (DRA) > 2.5 cm were recruited and randomized into two equal groups; the control group received a program of selected abdominal exercises and low caloric diet of 1200 kcal/ day for 4 weeks, and the study group received the same control group interventions in addition to TECAR application. DRA degree was the primary outcome, while weight and body mass index measures were the secondary outcomes. All variables were measured at the baseline and after 4 weeks of the intervention by rectus diastasis test, abdominal ultrasonography, and calibrated weight scale. Results. Analysis showed a significant reduction (P < .05) in weight, body mass index, rectus diastasis test, and ultrasound measures in both groups in favor of the study group Conclusion. Using TECAR with a standard program of abdominal exercises and low caloric diet has more beneficial effects on postnatal DRA than practicing the exercise program alone with the low-calorie diet.

Effect of monopolar capacitive resistive radiofrequency in treating stress urinary incontinence: A pilot randomized control trial.

To assess the effectiveness of 448 kHz monopolar capacitive resistive radiofrequency (MCRR) in the treatment of females with stress urinary incontinence (SUI). Forty females with SUI complaints were separated randomly into two equal groups. Group A with 20 females received the MCRR therapy for 20 min and performed pelvic floor exercises for 20 min. Group B with 20 females received placebo treatment by applying the same application as in Group A without emitting any waves for 20 min, three times a week, for 4 weeks. The patients in both groups were instructed to pause the treatment during their menstruation; the patients were instructed to maintain home pelvic floor exercises. Both groups were assessed by a perineometer that was used to assess the strength of the pelvic floor muscles (PFM), the visual analogue scale (VAS), and the Incontinence Symptom Severity Index to assess the frequency of urinary incontinence symptoms as described by each patient before treatment and after 4 weeks of treatment. There was a significant reduction (p < 0.05) in VAS and the Incontinence Symptom Severity Index and a significant increase in the strength of the PFM in both groups post-treatment compared with the pre-treatment. Regarding between-subject effects, there was a significant difference in VAS, the Incontinence Symptom Severity Index, and the perineometer between both groups (p < 0.05), and this significant improvement favored Group A. MCRR and pelvic floor exercises are more effective methods for the treatment of SUI than just pelvic floor exercises of females with SUI. ClinicalTrials.gov. Identifier: NCT04612205.

A collisional global sheath – Bulk model of argon plasma for semiconductor scale manufacturing

Plasma processes enhance the high-quality, semiconductor fabrication employed in large-scale industries. A crucial element in this process are the many gases that generate different reactive species at low temperatures. Capacitive plasma discharge radio frequency CCPs play a major role in semiconductor scale fabrication. The analysis of nonlinear dynamics in CCPs are complicated even under simple approaches. Therefore, we study self consistent collision fluid model, particle in cell simulation PIC, step approximation and finally the global model to find the accurate solution of merging plasma sheath -bulk region. For this purpose we study the self consistent collisional fluid model to find the accurate charge–voltage distribution V(Q) which controls the nonlinear dynamics of CCPs. The results against the PIC simulations and the more elaborate model step approximation is accomplished with higher accuracy. Consequently, the cubic polynomial formula V(Q) are applied in the global model. Accurate analytical global sheath-bulk calculations of the higher harmonic effect-exhibiting average power distributions, bulk potentials, and currents are obtained. This study provides an effective solution of collision regime for any arbitrary plasma reactor designs, including single-frequency and double frequency CCPs. Moreover, we used the argon gas as a good example in our study for a good ion etching. Finally, we can assist in achieving effective results that are consistent with experimental data and in large-scale applications in the semiconductor sector.

Radiosensitization effect of radiofrequency hyperthermia in the presence of PEGylated-gold nanoparticles on the MCF-7 breast cancer cells under 6 MeV electron irradiation.

The purpose of the study was to investigate the radiosensitization effect of radiofrequency (RF) hyperthermia in combination with PEGylated gold nanoparticles (PEG-GNPs) on MCF-7 breast cancer cells under electron beam radiotherapy (EBRT) based on the clonogenic assay. The cell death of MCF-7 breast cancer cells treated with 13.56 MHz capacitive RF hyperthermia (power: 150W) for 2, 5, 10, and 15 min combined with 6 MeV EBRT, with a dose of 2 Gy, was evaluated in the presence of 20 nm PEG-GNPs with a low nontoxic concentration (20 mg/l). All the treatment groups were incubated for 14 days. Thereafter, survival fractions and viability of the cells were calculated and analyzed against the control group. The presence of PEG-GNPs inside the MCF-7 cancer cells during electron irradiation decreased cell survival significantly (16.7%) compared to irradiated cells without GNPs. Applying hyperthermia before electron irradiation with a capacitive RF system decreased cell survival by about 53.7%, while hyperthermia without irradiation did not show any significant effect on cell survival. Combining the hyperthermia with the presence of PEG-GNPs in the cells decreased the cell survival by about 67% at the electron irradiation, showing their additive radiosensitization effect. Low nontoxic concentration of 20 nm PEG-GNPs increases the radiosensitization effect of combining 6 MeV EBRT and RF hyperthermia on MCF-7 cancer cells. Combining hyperthermia with PEG-GNPs in electron radiotherapy could be an appropriate method for enhancing radiotherapy effectiveness on cancerous cells which can be studied on different cells and electron energies in future research.