Jung Wook Lim

Characteristics of TiO2 Films Prepared by ALD With and Without Plasma

High-quality TiO 2 films were grown at 250°C by plasma-enhanced atomic layer deposition (ALD) with a mixture of O 2 and N 2 plasma for the first time. The films exhibited an improved uniformity of within ′3%, a reliable growth rate of 0.042 nm/cycle, and improved electrical properties, including dielectric constant and leakage current compared to those prepared by conventional ALD. In particular, the plasma process enhanced the rate of adsorption of precursors during the initial growth stage by generating new active functional groups and the surface roughening was suppressed.

Low-Temperature Deposition of Aluminum Oxide on Polyethersulfone Substrate Using Plasma-Enhanced Atomic Layer Deposition

Very uniform Al 2 O 3 films could be deposited on polyethersulfone (PES) by plasma-enhanced atomic layer deposition (PEALD) using O 2 as O-precursor at temperatures ranging from 90 to 150°C. Although the use of rf plasma was prone to induce bending of the plastic substrate, lowering rf power and deposition temperature could eliminate the bending of the PES substrate in PEALD of an Al 2 O 3 layer. At 100°C, Al 2 O 3 films were deposited successfully by PEALD with 0.3 s rf pulse width and 300 W, with no measurable bending of substrate and decrease of deposition rate. The etch rate of PEALD Al 2 O 3 films deposited at 100°C, was slow as a factor of 2.6 compared to that of ALD Al 2 O 3 films deposited at 100°C.

PEALD of Zirconium Oxide Using Tetrakis(ethylmethylamino)zirconium and Oxygen

Highly uniform ZrO 2 films were deposited by plasma enhanced atomic layer deposition (PEALD) using tetrakis(ethylmethylamino)zirconium (TEMAZ) and O 2 as precursors. The deposition rates were 0.14 and 0.11 nm/cycle at temperatures of 110 and 250°C, respectively. ZrO 2 films deposited at 150°C contained ∼3% nitrogen, incorporated from the Zr-precursor, which contains four amino-groups. In the absence of a plasma, a ZrO 2 film was not deposited with TEMAZ and O 2 at 150°C. The electrical characteristics including breakdown strength and permitivity were also evaluated. The permitivities for 110°C- and 200°C-ZrO 2 films were 16.1 and 26.9, respectively.

Low-voltage and high-gain pentacene inverters with plasma-enhanced atomic-layer-deposited gate dielectrics

The pentacene thin-film transistors with the plasma-enhanced atomic-layer-deposited 150nm thick Al2O3 or 120nm thick ZrO2 have been operated at gate voltages between −3 and 3V. The inverter with a ZrO2 gate dielectric shows a gain of 49 and a full swing from supply voltage (Vdd) to 0V, operating at input voltages (Vin) from 0to−1V and at Vdd of −1V. The hysteresis observed in the voltage transfer characteristic of the inverter depends on the scan range of Vin applied to the driver transistor, regardless of the Vdd applied to the load transistor.

Oxide-silicon-oxide buffer structure for ultralow temperature polycrystalline silicon thin-film transistor on plastic substrate

A novel oxide-silicon-oxide buffer structure to prevent damage to a plastic substrate in an ultralow temperature (<120/spl deg/C) polycrystalline silicon thin-film transistor (ULTPS TFT) process is presented. Specifically, an amorphous silicon film was inserted as an absorption layer into buffer oxide films. The maximum endurable laser energy was increased from 200 to 800 mJ/cm/sup 2/. The fabricated ULTPS nMOS TFT showed a performance with mobility of 30 cm/sup 2//Vs.

High-performance ultralow-temperature polycrystalline silicon TFT using sequential lateral solidification

This letter presents technologies to fabricate ultralow-temperature (< 150 /spl deg/C) polycrystalline silicon thin-film transistor (ULTPS TFT). Sequential lateral solidification is used for crystallization of RF magnetron sputter deposited amorphous silicon films resulting in a high mobility polycrystalline silicon (poly-Si) film. The gate dielectric is composed of plasma oxidation and Al/sub 2/O/sub 3/ grown by plasma-enhanced atomic layer deposition. The breakdown field on the poly-Si film was above 6.3 MV/cm. The fabricated ULTPS TFT showed excellent performance with mobility of 114 cm/sup 2//V /spl middot/ s (nMOS) and 42 cm/sup 2//V /spl middot/ s (pMOS), on/off current ratio of 4.20 /spl times/ 10/sup 6/ (nMOS) and 5.7 /spl times/ 10/sup 5/ (pMOS), small V/sub th/ of 2.6 V (nMOS) and -3.7 V (pMOS), and swing of 0.73 V/dec (nMOS) and 0.83 V/dec (pMOS).

Vanadium Dioxide Films Deposited on Amorphous SiO2- and Al2O3-Coated Si Substrates by Reactive RF-Magnetron Sputter Deposition

VO2 films showing abrupt metal–insulator transition (MIT) were fabricated on amorphous-film-coated Si wafers by reactive RF-magnetron sputter deposition using a V-metal target, and postdeposition annealing. The amorphous films were thermally grown SiO2 or Al2O3 films deposited by low-temperature plasma-enhanced atomic layer deposition. The effects of the underlayer and chamber pressure governing oxidation ambient on MIT characteristics were investigated. The MIT of VO2 films deposited at 5 mTorr on SiO2 and Al2O3 induced resistance changes of 1.3×104 and 2.3×103, respectively. The resistance change due to MIT was larger than 6.3×103 in an operating pressure range as wide as 5–25 mTorr on SiO2.

Optical AlxTi1-xOy Films Grown by Plasma Enhanced Atomic Layer Deposition

AlxTi1-xOy (ATO) films were deposited by plasma enhanced atomic layer deposition (PEALD). In the deposition, it was possible to tailor the refractive index and the thickness of films by adjusting the number of cycles used for Al2O3 and TiO2 sublayers. Because optical thickness can be controlled, ATO films will be applicable to optical filters, high reflectivity coating layers and antireflection coating layers.

High-Performance Transparent Conducting Ga-Doped ZnO Films Deposited by RF Magnetron Sputter Deposition

Ga-doped zinc oxide (GZO) films were deposited using rf magnetron sputter deposition and a Ga2O3(5 wt %)-doped ZnO ceramic target under various deposition conditions. The effects of each deposition condition on the electrical, structural, and optical properties of the GZO films were investigated to obtain a transparent conducting oxide (TCO) with a high transmittance and a low resistivity for a-Si:H thin-film solar cells. Resistivity showed a strong dependence on working pressure and rf power. The lowest resistivity of 1.9?10-4 ??cm was obtained at an rf power density of 2.47 W/cm2. The highest figure of merit for the use of TCO was achieved in the 800-nm-thick GZO film [?=2.1?10-4 ??cm, average transmittance (400?800 nm) = 92.1%] deposited at 10 mTorr and an rf power density of 1.85 W/cm2. These results indicate that the high-performance TCO fabricated in this work is suitable for use as a transparent electrode layer for thin-film solar cells.

Pentacene-thin film transistors with ZrO2 gate dielectric layers deposited by plasma-enhanced atomic layer deposition

The effect of the dielectric constant and surface roughness of gate dielectrics on the electrical performance of pentacene-thin-film transistor (TFT) was investigated using high-K ZrO 2 films deposited by plasma-enhanced atomic layer deposition. The dielectric constant of ZrO 2 (κ ZrO 2 ) was in the range of 15.6-33.0, and the surface roughness was increased with κ ZrO 2 in the presently reported devices. Threshold voltage and subthreshold swing were effectively reduced with increasing κ ZrO 2 and were remarkably low, with values of -0.42 V and 0.15 V/dec, respectively, when κ ZrO 2 = 33.0. To the contrary, the carrier mobility was determined by the surface roughness of ZrO 2 gate dielectrics.