Hee-Woon Cheong

Improvement of uniformity in a weakly magnetized inductively coupled plasma

Magnetic fields are applied to inductively coupled plasma (ICP) to achieve high plasma densities using electromagnets. If the magnetic fields are set up such that the magnitude of magnetic flux density on the substrate decreases with both radial and axial distances from the substrates center (here after referred to as M-ICP-A), the plasma density increases by 237% compared with that for ICP although the non-uniformity of the plasma density for M-ICP-A (11.1%) is higher than that for ICP (10.9%). As the rate of decrease in the magnitude of magnetic flux density on the substrate increases both radially and axially, the non-uniformity in the plasma density increases further. The increase in the non-uniformity for M-ICP-A was confirmed to arise from the flute instability. To suppress the flute instability, we arranged the magnitude of magnetic flux density on the substrate to increase with increasing distance from the substrate center both radially and axially (here after referred to as M-ICP-V). In this configuration, plasma fluctuations were not observed, hence the plasma density non-uniformity was lowered to 8.1%, although the measured plasma density was higher than that for M-ICP-A. The oxide etch-rate non-uniformity in M-ICP-V (2.5%) was also lower than that for ICP (5.2%) or that for M-ICP-A (21.4%).

Low-k material damage during photoresist ashing process

The change of –OH and –CH3 component ratios in Fourier transform-infrared analysis of low-k materials during photoresist (PR) ashing processes were compared to assess the differences in the damages to low-k materials in a reactive ion etch (RIE) chamber and a magnetized-inductively coupled plasma (M-ICP) chamber. In M-ICP, the PR ashing rate was 28.1% higher than that of RIE, but the low-k material damage in M-ICP decreased when typical ashing conditions were used in each machine. The dependences of low-k material damage and PR ashing rate on the pressure, source power, and bias power in the M-ICP chamber were studied. We measured the ion energy distributions using an ion energy analyzer from which the flux could be also obtained. We found that the PR ashing rate increased as the ion flux increased, while the low-k material damage also increased as the ion flux and the incident ion energy increased. However, as the pressure decreased, the ion flux increased dramatically and the ion energy decreased. As a result, the PR ashing rate could be high and the low-k material damage low.

A study on reactive ion etching lag of a high aspect ratio contact hole in a magnetized inductively coupled plasma

Reactive ion etching lag (RIE lag) characteristics of a high aspect ratio contact hole in a magnetized inductively coupled plasma (M-ICP) etcher were investigated. The dependence of RIE lag on various process parameters, such as neutral gas pressure, magnetic flux density, bias power, bias frequency, and source power were investigated. It was confirmed that RIE lag could be reduced by properly adjusting these variables. Furthermore, the application of a magnetic field to the ICP etcher was helpful to increase the oxide etch rate and oxide-to-amorphous carbon layer selectivity.

Increased light extraction efficiency from top-emitting organic light-emitting diodes employing a mask-free plasma-etched stochastic polymer surface

Top-emitting organic light-emitting diodes(TEOLEDs) are drawing interest as future devices for both high-quality display and lighting. However, the currentTEOLEDs have external quantum efficiencies of approximately 20%, which still need improvement. To attain high device efficiencies in TEOLEDs, waveguide and surface plasmon polariton modes should be minimised. Many efforts have been made using nano- or micrometre-scale periodic gratings to extract the confined photons. However, significant angular distortion or colour shifts occur as the Bragg condition calls for. Here, an effective method is demonstrated for enhancing the light extraction efficiency from TEOLEDs employing a mask-free plasma-etched polymer surface with stochastically distributed nano-hemispheres. TEOLEDs with the stochastic polymer surface allowed us to achieve a device efficiency enhancement up to 1.55-fold relative to conventional devices without introducing spectral changes and angular emission distortion, unlike periodic grating-embedded devices. Because of the independence of the improvement from the particular emission wavelengths, the proposed TEOLEDs are attractive and practical for use in full colour and white lighting as well as display applications.

Technology and Policy Strategies in the Era of CPS (Cyber Physical System) and Automated Driving

Abstract Humanity is witnessing the next generation industrial revolution, so-called the fourth industrial revolution. In the fourth industrial revolution era, the high level of ICTs (Information and Communication Technologies) such as AI (Artificial Intelligence), IoT (Internet of Things), big data, cloud system will be converged and pervaded throughout the society which may lead to innovative changes in our life. Especially, CPS (Cyber Physical System) and automated driving are two of the most representative keywords of the fourth industrial revolution. In this paper, high-tech and policy strategies for SMEs (Small- and Medium-sized Enterprises) in Korea in the era of CPS and automated driving were investigated.

Design of highly efficient RGB top-emitting organic light-emitting diodes using finite element method simulations.

In this paper, we present finite element method simulations of top-emitting organic light-emitting diodes for designing optimized red, green, and blue full-color device structures. The OLED structures in the simulation are used to evaluate the device parameters, such as the outcoupling efficiency, electroluminescence spectra, and angular emission characteristics on organic layers with varying thickness and different cathodes. The numerical study also extracts these parameters for nano-structured devices. By observing the agreement between the simulated and measured data precisely, our simulations show capability of predicting the fabricated device results.

Particle formation and its control in dual frequency plasma etching reactors

The behavior of a particle cloud in plasma etching reactors at the moment when radio frequency (RF) power changes, that is, turning off and transition steps, was observed using the laser-light-scattering method. Two types of reactors, dual-frequency capacitively coupled plasma (CCP) and the hybrid CCP/inductively coupled plasma (ICP), were set up for experiments. In the hybrid CCP/ICP reactor (hereafter ICP reactor), the position and shape of the cloud were strongly dependent on the RF frequency. The particle cloud becomes larger and approaches the electrode as the RF frequency increases. By turning the lower frequency power off later with a small delay time, the particle cloud is made to move away from the electrode. Maintaining lower frequency RF power only was also helpful to reduce the particle cloud size during this transition step. In the ICP reactor, a sufficient bias power is necessary to make a particle trap appear. A similar particle cloud to that in the CCP reactor was observed around the sheat...

Study on spatial distribution of plasma parameters in a magnetized inductively coupled plasma

Spatial distributions of various plasma parameters such as plasma density, electron temperature, and radical density in an inductively coupled plasma (ICP) and a magnetized inductively coupled plasma (M-ICP) were investigated and compared. Electron temperature in between the rf window and the substrate holder of M-ICP was higher than that of ICP, whereas the one just above the substrate holder of M-ICP was similar to that of ICP when a weak (<8 G) magnetic field was employed. As a result, radical densities in M-ICP were higher than those in ICP and the etch rate of oxide in M-ICP was faster than that in ICP without severe electron charging in 90 nm high aspect ratio contact hole etch.