Ik Hyun Park

INVESTIGATION ON ETCH CHARACTERISTICS OF GESBTE THIN FILMS FOR PHASE-CHANGE MEMORY

ABSTRACT Inductively coupled plasma reactive ion etching of GeSbTe (GST) thin films with a photoresist mask was carried out in a Cl2/Ar gas. The monotonous increase in etch rate with increasing Cl2 concentration indicates that the etching of GST films obeys the reactive ion etching mechanism. The etch rates increased with increasing coil rf power and dc-bias voltage. The etch profiles was improved with decreasing coil rf power and dc-bias voltage and gas pressure gave little influence on the etch profile. The x-ray photoelectron spectroscopy analysis reveals that the rate limiting step in GST etching study is the etching of Te. Anisotropic etching of GST films was achieved using a Cl2/Ar chemistry at the optimized etch conditions.

Shape Change of Self-Organized NbOx Nanopillar Arrays by High Density Plasma Etching

The fabrication of nanostructures using self-organized niobium oxide nanopillars was investigated by high-density plasma reactive ion etching in a Cl2/Ar gas. Etch rates and etch profiles of niobium oxide pillars were examined by varying etch parameters. We confirmed that several nanostructures, such as nanotip and nanodot arrays, could be fabricated over large areas using optimal anodizing and etching conditions. The mechanism of forming different nanostructures were classified into two groups, isotropic and anisotropic etch mechanisms. It is expected that a novel technique proposed in this study offers a simple and cost-effective method for fabricating nanostructures from various material systems.

ETCH CHARACTERISTICS OF COFESIB MAGNETIC FILMS USING INDUCTIVELY COUPLED PLASMA REACTIVE ION ETCHING FOR MAGNETIC RANDOM ACCESS MEMORY

ABSTRACT Inductively coupled plasma reactive ion etching of CoFeSiB magnetic thin films was studied in a Cl2/O2/Ar gas mix. The etch rate, etch selectivity and etch profile of this magnetic film were examined on varying gas concentration, coil rf power, gas pressure and dc-bias voltage. As the Cl2 gas increased, the etch rate monotonously decreased and etch residues decreased but etch slope was slanted. The use of the TiN hard mask gave rise to high selectivity of CoFeSiB to the TiN mask due to large decrease in etch rate of TiN in Cl2/O2/Ar gas mix. The addition of O2 into the gas mix led to the anisotropic etching of CoFeSiB films without the etch residues.

ELECTRICAL CHARACTERIZATION OF NICKEL OXIDE THIN FILMS DEPOSITED BY REACTIVE SPUTTERING FOR MEMORY APPLICATIONS

ABSTRACT This paper describes a study of the deposition of nickel oxide (NiO) thin film and its switching properties. The NiO films were deposited by dc reactive magnetron sputtering in an Ar/O2 mix at room temperature on Pt/Ti/SiO2/Si substrates. The effects of O2 concentration on the deposition rate, crystal structure, microstructure and electrical properties of films were investigated. As the O2 concentration increased, the deposition rate of NiO films gradually decreased. Film crystallinity and microstructure improved with increasing O2 content but became poorer at O2 concentrations over 40%. NiO films deposited at 12% O2 exhibited good switching properties applicable to the memory device.

FORMATION OF Si NANOSTRUCTURES USING DRY ETCHING WITH SELF-ORGANIZED METAL OXIDE NANOPILLAR MASKS

ABSTRACT In this study, a novel method is being proposed for the formation of nanostructures, utilizing the electrochemical anodization of Al/metal layers and high density plasma etching. Self-assembled metal oxide pillars formed by anodizing Al/metal layers were employed as an etching mask for nanostructure formation. Once the shape and size of the metal oxide pillars have been determined, the shape and size of the Si dots are dependent on the etching conditions such as etching gas, coil power, and dc-bias. The etch characteristics of Si film and metal oxide pillars were investigated with regard to etch rate, selectivity and profile. Highly ordered Si nanodot arrays were fabricated on a wafer using optimized etching conditions.

METAL-INSULATOR TRANSITIONS IN POLYCRYSTALLINE VOx THIN FILMS

ABSTRACT Metal-insulator transition properties in polycrystalline VOx thin films, which were deposited using rf magnetron sputtering with a vanadium target on Pt/Ti/SiO2/Si substrates, were studied in terms of structural and electrical characteristics. The phase change of VOx thin films by annealing was confirmed from amorphous VOx films to mixed crystalline phases containing V2O3,VO2,V6O13, and V2O5. The metal-insulator transition of VOx thin films was observed by current-voltage measurement as a function of top-electrode area and the temperature. It was demonstrated that the VOx thin films can be applied to memory devices employing the transition from a high-resistance (off) insulating state to a low-resistance (on) metallic state.