Simulations of hybrid direct current radiofrequency (dc/rf) capacitively coupled plasmas

Abstract

Effects of applying a high negative direct current (dc) voltage in argon capacitive coupled plasmas on the flux of secondary electrons (SEs) to a radiofrequency (rf) biased electrode and plasma uniformity were investigated using particle-in-cell Monte Carlo collision simulation and results were compared with experimental results. High energy SEs originating at electrodes with high negative dc voltage due to ion-impact as well as electron-impact were accelerated out of the sheath through the sheath voltage drop. These SEs gain energy equal to the applied dc voltage and either travel to the wafer electrode where they are lost (dumped) or are trapped between electrodes depending on the voltage on bottom electrode. Trapping and dumping of ballistic electrons depends on the magnitudes of the voltages (dc and rf) applied to each electrode. High energy SEs alter the electron energy distribution function at the wafer, high energy electron flux to the wafer and the plasma density profile. With the application of negative dc voltage, wafer receives high energy electron flux with energies up to applied dc voltage. For the range of conditions examined in this paper, the plasma density increases with the application of the negative dc voltage due to ionization by trapping of high energy SEs. The electrons that originate at the negative dc electrode minimize the impact of enhanced radial electric fields at the rf electrode edge allowing dc/rf plasmas to be center peaked even at low (13.56 MHz) rf frequencies.

Enhanced NO2 Gas Sensing Performance of Multigate Pt/AlGaN/GaN High Electron Mobility Transistors

“…20 Achieving NO 2 sensing in the lower detection limits of <10 ppm is necessary for deploying the sensors for air quality monitoring. Among the published results, 4,15,21,22 a lower detection limit of NO 2 in the range of 0.5-10 ppm with enhanced sensing response was achieved in our recent results using Pt/AlGaN/GaN HEMT based gas sensors with interdigitated electrodes. 4 In this paper, we have extended our work and demonstrate NO 2 sensing for concentrations as low as 0.05 ppm (50 ppb).…”

“…Among the published results, 4,15,21,22 a lower detection limit of NO 2 in the range of 0.5-10 ppm with enhanced sensing response was achieved in our recent results using Pt/AlGaN/GaN HEMT based gas sensors with interdigitated electrodes. 4 In this paper, we have extended our work and demonstrate NO 2 sensing for concentrations as low as 0.05 ppm (50 ppb). The dimension of the Pt functionalization layer (gate) is an important parameter in gas sensing.…”

“…Hence, the detection of low-level NO 2 concentration in air quality monitoring is necessary. 4 Various metal oxide semiconductors, polymers, and electrochemical cell based NO 2 gas sensors have been reported, and their advantages and shortcoming were reviewed. [5][6][7][8][9][10][11][12][13][14] Among various gas sensors, GaN based sensors are gaining momentum due to their unique properties, such as a wide bandgap that allows high thermal resistance and the ability to withstand harsh chemicals, gaseous and corrosive environments.…”

Science-based, data-driven developments in plasma processing for material synthesis and device-integration technologies

“…High-energy secondary electrons altered the electron energy distribution function (EEDF) at the wafer, high-energy electron flux to the wafer and the plasma density profile. 102) Inelastic dissociation processes under consideration of the vibrational states were reported. [103][104][105] Simulations of atmospheric pressure plasma at the nonequilibrium phase were reviewed by Tochikubo.…”

Numerical characterization of dual-frequency capacitively coupled plasmas modulated by electron beam injection

“…Modulation schemes to control the characteristic parameters of CCP mainly include dual-frequency (DF) or multi-frequency CCP [1,[5][6][7][8][9][10][11][12][13], hybrid CCP [14][15][16][17][18], external magnetic fields [19,20], electron beam (EB) injection CCP [21][22][23][24][25][26][27][28][29], and ion beam injection [30]. Recently, EB-driven approaches have gained considerable attention.…”