K. S. Min

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.

Removal of Anodic Aluminum Oxide Barrier Layer on Silicon Substrate by using Cl2/BCl3 Neutral Beam Etching

The barrier layer of anodic aluminum oxide (AAO) formed on the silicon substrate was etched with Cl 2 /BCl 3 gas mixtures by a neutral beam and the results were compared with the AAO etched by an ion beam. The etch rate of AAO itself was increased with the increase of BCl 3 in Cl 2 /BCl 3 up to 60% in the gas mixture. And, the etching of AAO itself was related to the Cl radical density in the plasma and the formation of volatile BO x Cl y on the AAO surface for both the neutral beam etching and the ion beam etching. The AAO itself could be etched by both the neutral beam and the ion beam in all Cl 2 /BCl 3 gas mixtures. However, the barrier layer of the AAO located near the bottom of the AAO pore could not be etched using the ion beam etching due to the charging of the nanometer size AAO pore similar to the case of conventional reactive ion etching. Using the neutral beam etching, the barrier layer of AAO pore could be successfully etched with BCl 3 -rich BCl 3 /Cl 2 gas mixtures by removing the barrier layer without charging the AAO pore and by the forming volatile BO x Cl y .

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).

Formation of High Flux Parallel Neutral Beam Using a Three Grid System of Ion Beam during Low Angle Forward Reflection of Ions

The energy and the flux of the ion gun with a three-grid system was compared with those of the ion gun with a two-grid system and the characteristics of the neutral beam sources composed of the ion guns with different grid systems and a reflector for the low angle reflection of the ions were investigated. By using the three-grid system instead of the two-grid system and by applying higher negative voltage to the 2nd grid, a higher ion flux without changing the ion energy could be obtained for the ion gun of the neutral beam source. The three-grid ion gun system generated higher neutral beam fluxes compared to the two-grid ion gun system. This result was confirmed by measuring the etch rates of Si and GaAs with Ar and fluorine neutral beam. Also, using the neutral beam source with the three-grid ion gun, 35nm-width Si patterns could be etched vertically by CF4 gas indicating the formation of a parallel neutral beam.

Influence of Impurities in SiC Powder on High Quality SiC Crystal Growth

SiC powders having different purities were prepared by carbothermal reduction under different conditions from traditional process and SiC single crystals were grown by the PVT method from the powders. After crystal growth, boule was cut to wafers and they were polished for chemical and defect analyses. Total impurities including Al, B and Ti which were derived from powders decreased remarkably during crystal growth. The formation of defects including micropipe and dislocations such as TED, TSD and BPD was strongly influenced by impurity content. The effect of impurity seemed to be negligible at below 1ppm level for MPD. On the other hand, dislocations continuously decreased even more when higher purity SiC powder below 1ppm level was used.

Novel damage-free high-k removal for sub-32nm metal gate/high-k LSTP CMOSFETs using neutral beam-assisted atomic layer etching

Metal gate/high-k LSTP CMOSFETs for sub-32nm technology was demonstrated using a novel-damage free neutral beam-assisted atomic etching process. Due to its neutralized atomic flux and chemical reaction, it had a high etch selectivity, oxygen concentration control and improved device performance /reliability. NBALE is a key process for reducing GIDL and Ioff control which is a key factor for LSTP.