B. J. Park

Low angle forward reflected neutral beam source and its applications

As one of the many nano-device fabrication techniques employed in the semiconductor industry, neutral beams are being examined using various methods to solve possible charge-related problems that occur during device processing. This review introduces a neutral beam generated by surface neutralization of an ion beam using a low angle forward reflection technique and explains its application to various areas such as surface treatments and etching. The neutralization efficiency of an ion beam using a low angle forward reflection technique was approximately 99.7%. When a metal-oxide-semiconductor device was etched using a reactive neutral beam, it was confirmed that charge-related problems such as aspect-ratio-dependent etching and gate oxide charging could be removed using reactive neutral beam etching instead of conventional reactive ion etching. Neutral beams can be beneficial to other devices such as the III-V device and field emission device.

X-ray photoelectron spectroscopic study of Ge2Sb2Te5 etched by fluorocarbon inductively coupled plasmas

X-ray photoelectron spectroscopy was used to determine the level of surface fluorination damage of Ge2Sb2Te5 (GST) etched by fluorocarbon gases at different F/C ratios. When blank GST was etched, the gas with a higher F/C ratio produced a thinner C–F polymer on the etched surface but fluorinated Ge, Sb, and Te compounds were observed in the remaining GST. When the sidewall of the etched GST features was investigated, a thicker fluorinated layer was observed on the GST sidewall etched by the higher F/C ratio gas, indicating more fluorination due to the difficulty in preventing F diffusion into the GST through the thinner C–F layer.

A novel damage-free high-k etch technique using neutral beam-assisted atomic layer etching (NBALE) for sub-32nm technology node low power metal gate/high-k dielectric CMOSFETs

For the first time, a novel damage-free neutral beam-assisted atomic etching process has successfully demonstrated the removal of the residual high-k dielectric layer after gate patterning. Due to its neutralized atomic flux and chemical reaction, high etch selectivity is observed to improve device performance and reliability. This process should significantly enhance high-k/metal gate manufacturability.

Precise Depth Control and Low-Damage Atomic-Layer Etching of HfO2 using BCl3 and Ar Neutral Beam

The etch characteristics of HfO 2 by atomic-layer etching (ALET) were investigated using a BCl 3 /Ar neutral beam. The effect of ALET on surface modification and etch-depth control was also examined. Self-limited etching of HfO 2 could be obtained using BCl 3 ALET. This was attributed to the absorption of BCl 3 by the Langmuir isotherm during the absorption stage and the vaporization of hafnium-chlorides/boron oxychlorides formed on the surface during the desorption stage. In addition, the surface composition of HfO 2 was not altered by etching during ALET.

Effects of Axial Magnetic Field on Neutral Beam Etching by Low-Angle Forward-Reflected Neutral Beam Method

A low axial magnetic field was applied to an inductively coupled plasma (ICP) ion source used to generate a neutral beam for a low-angle forward-reflected neutral (LAFRN) beam system, and its effects on the ICP ion source and the features of Si and SiO2 etching using the LAFRN beam system for SF6 gas were investigated. As a result of applying a low axial magnetic field of approximately 20 G, a significant increase in SF3+ ion flux extracted from the source was observed among the various reactive ions generated using SF6 gas, and the etch rates of Si and SiO2 using a neutral beam formed by the magnetically enhanced SF6 ICP source were also increased. The application of the low axial magnetic field also improved the etch uniformity of the neutral beam etching system.

Effect of neutral beam etching of p-GaN on the GaN device characteristics

GaN materials were etched using a CF4-based neutral beam, and its etch damage characteristics were compared with those etched with a CF4-based inductively coupled plasma (ICP). Photoluminescence data showed that the neutral beam etched GaN materials show fewer defects on the surface compared to the GaN materials etched by ICP. Also, the current–voltage characteristics of GaN light emitting diodes fabricated with p-GaN etched by the neutral beam showed less damage compared to those fabricated with p-GaN by the ICP. When a photonic crystal-like structure having 2-μm-diameter microlens array was formed using the neutral beam etching on the p-GaN of the GaN device, an increase of 20% in the optical emission intensity could be observed without significantly increasing the forward voltage (0.7V).

Selective growth of nanometre scale structures with high resolution using thermal energy in AFM lithography

We report the effect of applied thermal energy in the fabrication of protruded nanostructures on tantalum (Ta) thin films using atomic force microscope (AFM) lithography and the fabrication of nanopatterns of Ta thin films by a dry etching process of protruded tantalum oxide (Ta2O5). Oxidized nanostructures with a high aspect ratio were successfully fabricated at high temperature by applying thermal energy. The lithographic speed of fabrication of protruded nanostructures was dramatically improved by the enhancement of electron transfer depending on the applied thermal energy and directional diffusion of OH− ions depending on the increase of temperature. Nanopatterns of Ta with a high angle slope (over 80°) were fabricated by selective dry etching of Ta2O5.

Improvement of surface roughness in silicon-on-insulator wafer fabrication using a neutral beam etching

Silicon-on-insulator (SOI) wafers were etched by an energetic chlorine neutral beam obtained by the low-angle forward reflection of an ion beam, and the surface roughness of the etched wafers was compared with that of the SOI wafers etched by an energetic chlorine ion beam. When the ion beam was used to etch the silicon layer of the SOI wafers, the surface roughness was not significantly changed even though the use of higher ion bombardment energy slightly decreased the surface roughness of the SOI wafer. However, when the chlorine neutral beam was used instead of the chlorine ion beam having a similar beam energy, the surface roughness of the SOI wafer was significantly improved compared with that etched by the chlorine ion beam. By etching about 150?nm silicon from the SOI wafer having a 300?nm-thick top silicon layer with the chlorine neutral beam at the energy of 500?eV, the rms surface roughness of 1.5?? could be obtained with the etch rate of about 750???min?1.

Effect of Fluorine Ion/Neutral-Beam Irradiation on Ohmic Contact Formation to n-Type GaN

The effect of fluorine neutral/ion-beam irradiation to an n-type GaN surface on the ohmic contact property of a Ti/Al/Au multilayer scheme was investigated. The contact formed after a fluorine neutral-beam treatment showed lower contact resistivity than that formed without the treatment and that formed after a fluorine ion-beam treatment. The irradiation of the fluorine neutral beam is believed to create nitrogen vacancies at the surface region of n-GaN due to the preferential removal of nitrogen, which acts as a donor impurity. In addition, the GaN surface treated by the fluorine neutral beam showed less GaF x formation and smaller surface damage compared to the surface treated by the fluorine ion beam. This resulted in lower ohmic contact resistivity. After annealing at temperatures above 600°C, the contact formed after the fluorine neutral-beam treatment exhibited an excellent linear current-voltage characteristic.

Nanostructures Fabrication on Ta Thin Film Using Atomic Force Microscope Lithography

ABSTRACT Atomic force microscope (AFM) lithography based on localized current injection was carried out for fabricating nanostructures of metal oxide on tantalum (Ta). Fabricated nanopatterns of tantalum oxide (Ta2O5) were selectively etched by magnetically enhanced inductively coupled plasma (MEICP) etching system. Nanopatterns of Ta with feature size in the range of a few tens-hundreds nm were successfully fabricated.