Jaehyoung Koo

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.

Initial reaction of hafnium oxide deposited by remote plasma atomic layer deposition method

A remote plasma atomic layer deposition (RPALD) method has been applied to grow a hafnium oxide thin film on the Si substrate. The deposition process was monitored by in situ XPS and the as-deposited structure and chemical bonding were examined by TEM and XPS. The in situ XPS measurement showed the presence of a hafnium silicate phase at the initial stage of the RPALD process up to the 20th cycle and indicated that no hafnium silicide was formed. The initial hafnium silicate was amorphous and grew to a thickness of approximately 2nm. Based on these results and model reactions for silicate formation, we proposed an initial growth mechanism that includes adatom migration at nascent step edges. Density functional theory calculations on model compounds indicate that the hafnium silicate is thermodynamically favored over the hafnium silicide by as much as 250kJ∕mol.

Suppression of parasitic Si substrate oxidation in HfO2–ultrathin-Al2O3–Si structures prepared by atomic layer deposition

We investigated the effects of Al2O3 thickness on the suppression of parasitic substrate oxidation in HfO2–ultrathin-Al2O3–Si structures. The use of H2O as oxidizing agent in the atomic layer deposition (ALD) chemistry is considered key to preventing the formation of an SiOx interlayer during oxide deposition. An Al2O3 layer prepared with 10 cycles of atomic layer deposition (ALD, ∼0.74nm) effectively suppressed substrate oxidation during rapid thermal annealing in N2 for 10 s below 800 °C. Parasitic oxidation was observed at 600 °C for samples with only five cycles or without Al2O3. Ultrathin Al2O3 films can be relevant for the integration of HfO2 as gate dielectric in silicon technology.

A Comparison of Al2O3/HfO2 and Al2O3/ZrO2 Bilayers Deposited by the Atomic Layer Deposition Method for Potential Gate Dielectric Applications

Thin films of Al2O3/HfO2 and Al2O3/ZrO2 bilayers were investigated as potential replacements for traditional SiO2 gate dielectrics. The Al2O3 film exhibited an amorphous structure without an interfacial layer, while the HfO2 and ZrO2 films had randomly oriented polycrystalline structures with a silicate interlayer. The two gate oxides, Al2O3 and HfO2, have characteristics that are complementary to each other, and it was possible to achieve a high-k gate oxide with a low leakage current as well as large band gap characteristics using a composite of these two oxides. Leakage currents of the Al2O3, HfO2, ZrO2, Al2O3/HfO2, and Al2O3/ZrO2 films were about 4.2×10-8, 8.2×10-4, 7.5×10-5, 2.4×10-6, and 1.2×10-6 A/cm2, respectively, at a gate bias voltage of |VG-VFB|=2 V. The corresponding calculated equivalent oxide thickness (EOT) values for the Al2O3, HfO2, ZrO2, Al2O3/HfO2, and Al2O3/ZrO2 films were about 2.3, 1.8, 1.9, 1.3, and 1.4 nm, respectively. The Al2O3/HfO2 and Al2O3/ZrO2 bilayers had improved gate oxide characteristics compared to those that were composed of only Al2O3, ZrO2 or HfO2 alone.

Incorporation Effect of Thin Al2O3 Layers on ZrO2–Al2O3 Nanolaminates in a Composite Oxide–High-κ-Oxide Stack for Floating-Gate Flash Memory Devices

We demonstrate the electrical properties and reliability of ZrO2–Al2O3 nanolaminates as high-κ dielectric materials in a composite oxide–high-κ-oxide (OKO) stack for floating-gate flash memory devices with 40 nm technology nodes and beyond. The effects of incorporating thin Al2O3 layers into ZrO2 films as an inserting layer and a capping layer on the electrical properties and reliability are discussed. The incorporation of Al2O3 layers significantly improves the leakage current versus the capacitive-equivalent thickness (CET) and TDDB characteristics of the ZrO2–Al2O3 nanolaminate compared with those of the pure ZrO2 owing to the mismatch of the grain boundaries, improved resistance to silicon diffusion, and enhanced energetic-electron hardness of the high-κ film.

Atomic Layer Deposition of TiN on Si (100) and (111) Substrates

Titanium nitride (TiN) films were successfully deposited on ρ-type Si (100) and (111) substrates by atomic layer deposition (ALD) method at 450°C. In this ALD system, the TiCl 4 and NH 3 gases were supplied, separately and Ar purge gas was added between the source and reactant gases to suppress the direct reaction. The main purpose of this study is to investigate the properties of TiN film grown by ALD method. To investigate the growth mechanism, the growth model of TiN was suggested for the calculation of growth rate per cycle with Cerius program. The results of calculation by the model were compared with experimental values of the TiN film deposited by ALD method. TiN films deposited on Si (100) and (111) substrates were examined by TEM and showed the randomly oriented columnar structure. The thickness of TIN film deposited on Si(111) substrate was slightly thicker than that of TiN film deposited on Si(100) substrate. Chlorine content in both TiN films was below the detection limit of AES ( 3 and 4.98g/cm 3 . which are higher than that of the films deposited by other conventional CVD methods.

Plasma Enhanced Atomic Layer Deposition of ZrO 2 Gate Dielectric

Zirconium oxide (ZrO 2 ) films were investigated as a potential replacement for silicon dioxide gate dielectric. ZrO 2 films were deposited by both atomic layer deposition (ALD) and plasma enhanced ALD (PEALD) techniques using Zr t-butoxide and Zr(NEt 2 ) 4 as Zr precursors and oxygen as reactant gas. The XTEM images showed a randomly oriented polycrystalline structure of ZrO 2 and amorphous characteristics of the interfacial layer. The calculated dielectric constant value of the ZrO 2 films are about 10∼18 and these low values are believed due to the low dielectric constant interface layer. ZrO 2 films deposited with oxygen plasma using Zr(NEt 2 ) 4 showed the leakage current of 3.12X10 -9 A/cm 2 at the gate bias voltage of -1.0 Volt with the equivalent oxide thickness value of 1.39 nm. ZrO 2 films deposited with the oxygen plasma showed generally improved film quality with relatively low leakage current, small hysteresis and low carbon incorporation as well as the higher growth rate compared to the films deposited with the oxygen gas. Also, ZrO 2 films deposited using Zr(NEt 2 ) 4 showed relatively improved film properties compared to the films deposited using Zr t-butoxide. This study demonstrated the possible application of PEALD technique for the high quality ZrO 2 gate dielectric film deposition.