Yang-Do Kim

Remote plasma enhanced atomic layer deposition of TIN thin films using metalorganic precursor

TiN films were deposited by remote plasma enhanced atomic layer deposition (PEALD) method using tetrakis-dimethyl-amino-titanium precursor and hydrogen, hydrogen/nitrogen mixture, and nitrogen plasmas. Remote PEALD method showed a relatively wide temperature window compared to that of conventional ALD process due to the increased reactivity of reactant gas. TiN films showed significantly lower impurity contents than those of the films deposited by other methods such as plasma enhanced chemical vapor deposition, metalorganic chemical vapor deposition, and conventional ALD using the same precursor. TiN films deposited using N2 plasma showed better characteristics than the films deposited using H2 and H2/N2 mixture plasmas. TiN films deposited by remote PEALD at 250 °C showed the resistivity value as low as about 300 μΩ cm and exhibited excellent conformal step coverage on 0.25-μm-wide and 2.5-μm-deep contact hole structure.

Characteristics of ZrO2 gate dielectric deposited using Zr t–butoxide and Zr(NEt2)4 precursors by plasma enhanced atomic layer deposition method

Scaling down of the microelectronic devices feature size is demanding high-quality ultra thin high-k gate dielectric as a potential replacement for SiO2 gate dielectric. Among the high-k materials, ZrO2 is considered as a potential alternative to SiO2 gate dielectric below 2 nm due to its thermodynamical stability as well as excellent electrical properties. For these reasons, we investigated ZrO2 films prepared by the normal atomic layer deposition (ALD) and plasma enhanced ALD (PEALD) techniques using Zr t–butoxide and Zr(NEt2)4 metal organic precursors. This study showed that ZrO2 films deposited by the PEALD method showed generally improved film qualities with relatively low-leakage current, negligible hysteresis, and low-carbon incorporation compared to those of the films deposited by the conventional ALD method. Also, ZrO2 films deposited using Zr(NEt2)4 precursor showed better film qualities than those of films deposited using Zr t–butoxide. Especially, ZrO2 films deposited using Zr(NEt2)4 with oxyg...

Study on the characteristics of TiAlN thin film deposited by atomic layer deposition method

The microstructural characteristics and electrical and chemical properties of TiAlN films deposited by the atomic layer deposition (ALD) method were investigated. The growth rate of TiAlN film was measured to be 1.67 A/cycle. TiAlN film deposited by ALD has a B1(NaCl) structure with a lattice parameter of 4.20 A. The chlorine content in TiAlN film was below the detection limit of Auger electron spectroscopy. TiAlN film showed the columnar structure with a resistivity of about 400 μΩ cm. The sheet resistance increased abruptly after annealing at 650 °C due to the formation of a high resistivity Cu-silicide phase at the interface between the TiAlN and Si substrate. The failure of the ALD TiAlN barrier layer was observed by an etch-pit test after annealing at 600 °C for 1 h. TiAlN films deposited by the ALD method exhibited excellent film properties and improved barrier characteristics compared to other chemical vapor deposition methods.

ZrO2 Gate Dielectric Deposited by Plasma-Enhanced Atomic Layer Deposition Method.

Zirconium oxide (ZrO2) films were investigated as a potential replacement for a silicon dioxide (SiO2) gate dielectric and were successfully deposited by the atomic layer deposition (ALD) method using zirconium t-butoxide and oxygen as the Zr precursor and reactant gas, respectively. ZrO2 films exhibited a relatively smooth surface and interface layer, and a stoichiometric structure. The ZrO2 films deposited with the oxygen plasma state showed higher growth rate with lower carbon content than the films deposited with the oxygen gas phase. The leakage currents of the films deposited with the oxygen gas phase and oxygen plasma state were about 3.7×10-7 and 2.7×10-8 A/cm2 at the gate bias voltage of -1.0 V with calculated equivalent oxide thicknesses of about 2.85 and 3.31 nm, respectively. The calculated interface state densities were 1.16×1011 and 5.52×1012 eV-1 cm-2 for the films deposited with the oxygen gas phase and oxygen plasma state, respectively. ZrO2 films deposited with the oxygen plasma state showed generally improved film quality compared to the films deposited with the oxygen gas phase. This study demonstrated the possible application of the plasma-enhanced ALD technique for high-quality ZrO2 gate dielectric thin film deposition.

Advantages of using Ti-mesh type electrodes for flexible dye-sensitized solar cells

We used Ti meshes for both the photoanodes and counter electrodes of dye-sensitized solar cells (DSSCs) to improve the flexibility and conductivity of the electrodes. These mesh type electrodes showed good transparency and high bendability when subjected to an external force. We demonstrated the advantages of cells using such electrodes compared to traditional transparent conducting oxide based electrodes and back side illuminated DSSCs, such as low sheet resistance, elevated photo-induced current and enhanced sunlight utilization. Nanotube layers of different thicknesses were investigated to determine their effect on the photovoltaic parameters of the cell. The overall efficiency of the best cells was approximately 5.3% under standard air mass 1.5 global (AM 1.5 G) solar conditions. Furthermore, the DSSCs showed an efficiency of approximately 3.15% due to the all Ti-mesh type electrodes even after illumination from the back side.

Low temperature remote plasma cleaning of the fluorocarbon and polymerized residues formed during contact hole dry etching

We investigated the remote oxygen and hydrogen plasma cleaning to remove reactive ion etching (RIE) induced fluorocarbon and polymerized residues formed during the dry etching of the contact hole. After the RIE process, RIE induced fluorinated surface and/or fluorocarbon formation with a very homogeneous spatial distribution at several tens of A depth from the surface was observed. The photoresist films before and after the RIE process showed a similar ashing behavior. Ashing rate generally increased with increasing the process temperature and plasma power. X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis showed that the carbon and fluorine associated contamination can be effectively removed by oxygen plasma but it left a small amount of carbon residue and sacrificial silicon oxide. Hydrogen plasma cleaning was necessarily required to remove the residual carbon contaminants formed on the silicon surface after oxygen plasma ashing. Two step cleaning, oxygen plasma ashing with an intentionally left very thin photoresist layer and subsequent hydrogen plasma cleaning, is a very effective cleaning process to remove residual carbon and polymer without forming a SiO2 layer. This article presents the systematic evaluation of the remote oxygen and hydrogen plasma cleaning of RIE induced polymer residues.We investigated the remote oxygen and hydrogen plasma cleaning to remove reactive ion etching (RIE) induced fluorocarbon and polymerized residues formed during the dry etching of the contact hole. After the RIE process, RIE induced fluorinated surface and/or fluorocarbon formation with a very homogeneous spatial distribution at several tens of A depth from the surface was observed. The photoresist films before and after the RIE process showed a similar ashing behavior. Ashing rate generally increased with increasing the process temperature and plasma power. X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis showed that the carbon and fluorine associated contamination can be effectively removed by oxygen plasma but it left a small amount of carbon residue and sacrificial silicon oxide. Hydrogen plasma cleaning was necessarily required to remove the residual carbon contaminants formed on the silicon surface after oxygen plasma ashing. Two step cleaning, oxygen plasma ashing with an in...

Barrier Characteristics of ZrN Films Deposited by Remote Plasma-Enhanced Atomic Layer Deposition Using Tetrakis(diethylamino)zirconium Precursor

The barrier characteristics of ZrN films deposited by remote plasma-enhanced atomic layer deposition (PEALD) using Zr[NEt2]4 [tetrakis(diethylamino)zirconium, TDEAZ] and N2 remote plasma have been investigated using various deposition parameters, such as temperature, plasma power, and processing pressure. The optimized processing temperature, plasma power, and pressure were 300 °C, 200 W, and 1 Torr, respectively. ZrN films deposited by remote PEALD using TDEAZ and N2 remote plasma showed a carbon content of about 6 at. %. The resistivity of ZrN films was about 400 µΩcm. The barrier characteristics of Cu/ZrN/Si samples have been investigated by X-ray diffraction (XRD) analysis, Auger electron spectroscopy (AES), and etch-pit test after annealing in vacuum for 1 h in the temperature range of 500–700 °C with an interval of 50 °C. The structure of ZrN films remained amorphous up to 550 °C and crystallized after annealing above 600 °C. The barrier characteristics of ZrN films remained up to 550 °C. ZrN films deposited by remote PEALD are believed to be applicable as barriers for Cu metallization in a semiconductor process.

Microstructure Effect on the High-Temperature Oxidation Resistance of Ti–Si–N Coating Layers

The oxidation behaviors of Ti–Si–N coating layers were investigated in terms of Si content and their characteristic microstructures. The Ti–Si–N films were characterized as composites of fine TiN crystallites and amorphous Si3N4 phase. The continuity of amorphous Si3N4 phase, i.e., the degree of encapsulation of TiN crystallites by amorphous Si3N4 phase, was an important key factor governing the oxidation behavior of Ti–Si–N coating layers. In the case of Ti–Si–N coating layers containing 4 at.% Si, TiN crystallites were not fully surrounded by the amorphous Si3N4 phase due to the insufficient amount of Si3N4 and the relatively large TiN crystallites size. Hence, the Ti–Si–N coating layers contained 4 at.% Si fast oxidized through TiN crystallites above 600°C. However, Ti–Si–N coating layers containing the Si content above 10 at.% showed much improved oxidation resistance even above 800°C because it had the finer TiN crystallites, and these TiN crystallites were fully surrounded by amorphous Si3N4 phase. The oxidation rate dependence on the Si content, and in particular the microstructure of Ti–Si–N film as derived from Si content, was systematically studied in this work.

Magneto-Mechano-Electric (MME) Energy Harvesting Properties of Piezoelectric Macro-fiber Composite/Ni Magnetoelectric Generator

Abstract Asymmetric and symmetric magnetoelectric (ME) laminates structures of piezoelectric macro-fiber composite (MFC)/nickel (Ni) were fabricated and investigated their ME and magneto-mechano-electric (MME) energy harvesting responses to an applied magnetic/mechanical stimulations. Both the structures strongly revealed the dependence of ME voltage coefficient (αME) on applied magnetic field directions with an important feature of a zero-bias field ME response. This is much more beneficial for designing the magnetic field sensors. The fabricated MFC/Ni structures exhibited good energy harvesting response to applied simultaneous magnetic/mechanical vibrations of lab magnetic stirrer. The electric power was successfully harnessed from magneto-mechanical stimulations; the resulting potential and power were up to ~20 Vp–p and ~6 μW respectively, which are quite enough power to light a commercial red LED with traditional rectifier circuit and capacitor. Hence, the present MFC/Ni ME generators provide their future feasibility having self-biasing feature for designing the magnetic field sensors as well as for powering small consumer electronic devices and wireless sensor network systems by exploiting mechanical/magnetic stimulations from surrounding.

The Influence of Dehydrogenation Speed on the Microstructure and Magnetic Properties of Nd-Fe-B Magnets Prepared by HDDR Process

The influence regarding the dehydrogenation speed, at the desorption-recombination state during the hydrogenation-disproportionation-desorption-recombination (HDDR) process, on the microstructure and magnetic properties of Nd-Fe-B magnetic powders has been studied. Strip cast Nd-Fe-B-based alloys were subjected to the HDDR process after the homogenization heat treatment. During the desorption-recombination stage, both the pumping speed and time of hydrogen were systematically changed in order to control the speed of the desorption-recombination reaction. The magnetic properties of HDDR powders were improved as the pumping speed of hydrogen at the desorption-recombination stage was decreased. The lower pumping speed resulted in a smaller grain size and higher DoA. The coercivity and the remanence of the 200-300 μm sized HDDR powder increased from 12.7 to 14.6 kOe and from 8.9 to 10.0 kG, respectively. In addition, the remanence was further increased to 11.8 kG by milling the powders down to about 25-90 μm, resulting in (BH) max of 28.8 MGOe.