Atomic layer etching (ALE), a cyclic process of surface modification and removal of the modified layer, is an emerging damage-less etching technology for semiconductor fabrication with a feature size of less than 10 nm. Among the plasma sources, inductively coupled plasma (ICP) can be a candidate for ALE, but there is a lack of research linking discharge physics to the ALE process. In this study, we comprehensively investigated the discharge physics of ICPs with a radio frequency (RF) bias and Ar/C4F6 mixture to be considered for the ALE process. Detailed studies on the discharge physics were conducted in each step of ALE (i.e., modification step, removal step) as well as the whole cycle as follows: (1) In the general ALE cycle, plasma properties dependent on the chamber geometry and the discharge mode of the ICP were analyzed; (2) in the modification step, a plasma instability with molecular gas was observed. The timescale for molecular gas removal was also investigated; (3) in the removal step, changes in plasma characteristics with the RF bias power were studied. Based on measurements of these plasma physical parameters, the discharge condition for ALE was optimized. ALE was performed on various thin films, including a-Si, poly c-Si, SiO2, and Si3N4. For each thin film, thicknesses of 0.5–2.0 nm were etched per cycle, as in quasi-ALE. Finally, ALE was performed on a patterned wafer, and the etch thickness of 0.6 nm per cycle and fine etch profile were obtained.

We developed a self-consistent global simulator of solenoidal-type inductively coupled plasma discharges and observed the effect of the radio-frequency (rf) bias power on the plasma density and the electron temperature. We numerically solved a set of spatially averaged fluid equations for charged particles, neutrals, and radicals. Absorbed power by electrons is determined by using an analytic electron heating model including the anomalous skin effect. To analyze the effects of rf bias power on the plasma properties, our model also combines the electron heating and global transport modules with an rf sheath module in a self-consistent manner. The simulation results are compared with numerical results by using the commercial software package CFD-ACE þ (ESI group) and experimental measurements by using a wave cutoff probe and a single Langmuir probe. V

We report the integral elastic, differential, momentum transfer, dissociative electron attachment and electronic and rotational excitation cross sections for the lowenergy electron impact on beryllium dihydride (BeH2) computed using the Quantemol-N interface for driving the UK molecular R-matrix code. The energy of the projectile electron is in the range 0.1-10 eV. The effect of multichannel coupling is investigated by calculating the cross sections with various target models by increasing the number of target states in the trial wavefunction of the entire scattering system. The cross sections converge for the calculation with more than 15-target states. The vertical excitation energies calculated with the present model give excellent agreement with the EOM-CCSD calculations. Collisional frequencies are determined using the momentum transfer cross section for a Maxwell-Boltzmann distribution. From the collisional frequency, the transport properties such as mean free path, diffusivity and mobility are calculated for the temperature range of 100 to 500000 K. The cross section data and transport properties reported in this article are important for fusion plasma.

The ion energy and angular distributions (IEADs) arriving at substrates strongly affect the etching rates in plasma etching processes. In order to determine the IEADs accurately, it is important to obtain the characteristics of radio frequency (rf) sheaths with multicomponent plasmas. However, very few studies have been conducted on an rf sheath model for multiple ion species including negative ions over the past few decades. Therefore, in this work, we extended previous semi-analytic collisionless rf sheath models for electronegative plasmas. The extended model was based on the previously developed models, and an equivalent circuit model was used to determine the sheath characteristics. Also, we obtained the IEADs using the rf sheath model and an analytic model for evaluation of the ion angular distribution functions. We observed that the developed model was in good agreement with the experimental results and the one-dimensional dynamics model. Also, we found that negative ion species could affect the characteristics of rf sheaths, hence negative ion species should be considered to obtain more accurate IEADs.

Two independent methods, namely, Binary-encounter Bethe (BEB) and complex scattering potential-ionization contribution (CSP-ic) methods, are employed to calculate the total ionization cross section (Qion) for cyclic organic molecules from ionization threshold to 5 keV for which there is a paucity of data in the literature. The Qion calculated with the (BEB/ωB97X) combination is found to give good agreement with the experimental results, the CSP-ic method, and the Qion calculated from Irikura orbital energies. The Qion for most of the targets are calculated for the first time over such a wide energy range. Hence, to check the consistency and reliability of the present data, we have also computed the static polarizability for all the targets and the variation of maximum ionization cross section (Qion,max) with polarizability is studied. A linear relationship is observed between these quantities indicating the consistency and reliability of the present Qion data. The targets studied are important for industrial applications, radiation biology, and astrophysics.