Han-Wool Yeon

Effects of Metal Electrode on the Electrical Performance of Amorphous In-Ga-Zn-O Thin Film Transistor

Effects of metal electrode on the electrical performance of amorphous In–Ga–Zn–O (a-IGZO) thin film transistor (TFT) have been studied. Electrical performances and interface stability between Mo, Al, and Cu electrode and a-IGZO semiconductor have been investigated before and after air-annealing. No inter-diffusion and interfacial reaction has been observed between Mo and a-IGZO and the turn-on voltage of the Mo electrode TFT was 0 V after annealing. As for Al, Al oxide was formed at the interface, and the number of conduction electrons in a-IGZO increased. Thus, a negative turn-on voltage was observed after air-annealing. As for Cu, Cu diffused into a-IGZO during air-annealing and acted as an acceptor. Therefore the a-IGZO TFT with a Cu electrode had a positive turn-on voltage and sub-threshold slope increased after air-annealing. These results indicate that the transistor performance can be affected by the metal types due to inter-diffusion or interfacial reaction between metal and a-IGZO.

Enhanced conductivity of solution-processed indium tin oxide nanoparticle films by oxygen partial pressure controlled annealing

A highly conductive and transparent indium tin oxide (ITO) film was developed using a nanoparticle-based solution process through the control of oxygen partial pressure during annealing. At an oxygen partial pressure of 2.1 × 10−3 Torr, a maximum conductivity of 313 Ω−1 cm−1 was obtained: a great improvement over the conductivity of conventional ITO nanoparticle films (at this conductivity, the sheet resistance decreased to 30 Ω sq−1, and the transmittance reached 90%). By analyzing the electron concentration and mobility using Hall measurements, we determined that the main factor contributing to the enhanced conductivity is the increase in electron concentration that occurs due to the formation of oxygen vacancies under low oxygen partial pressures. However, if the oxygen partial pressure is too low, the removal of the organic ligands covering the ITO nanoparticles is incomplete, and the electron mobility is reduced. Microstructure control is also necessary for further improvement of the mobility.

Effects of film thickness and deposition rate on the diffusion barrier performance of titanium nitride in Cu-through silicon vias

The influence of morphology on the performance of TiN diffusion barriers was studied by investigating the effects of film thickness and deposition rate. Increasing the TiN film thickness was ineffective in preventing Cu migration due to the columnar growth of TiN, which left rapid diffusion paths for Cu. When the thickness of the TiN film was less than 10 nm, slowly deposited TiN films showed better Cu barrier performance than rapidly deposited TiN films due to the formation of an amorphous structure, which is an effective phase for preventing Cu migration.

Influences of semiconductor morphology on the mechanical fatigue behavior of flexible organic electronics

The influence of crystalline morphology on the mechanical fatigue of organic semiconductors (OSCs) was investigated using 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) as a crystalline OSC and poly(triarylamine) (PTAA) as an amorphous OSC. During cyclic bending, resistances of the OSCs were monitored using the transmission-line method on a metal-semiconductor-metal structure. The resistance of the TIPS-pentacene increased under fatigue damage in tensile-stress mode, but no such degradation was observed in the PTAA. Both OSCs were stable under compressive bending fatigue. The formation of intergranular cracks at the domain boundaries of the TIPS-pentacene was responsible for the degradation of its electrical properties under tensile bending fatigue.

Improvements of mechanical fatigue reliability of Cu interconnects on flexible substrates through MoTi alloy under-layer

The mechanical fatigue of Cu films and lines on flexible substrates was investigated, and an improvement in the structures through the use of a MoTi alloy under-layer was proposed. Fatigue reliability was decreased by 3-fold in lines compared with films in the tensile condition and by 6-fold in the compressive condition. Crack formation was observed to be more detrimental for lines than for films. With a MoTi under-layer, the fatigue limit was increased by 2 times that of a structure without MoTi in the tensile condition and by 15 times in the compressive bending condition. The suppression of delamination through the use of a MoTi under-layer improved the fatigue reliability under compressive bending.

Effect of pulsed electric fields on dielectric breakdown in Cu damascene interconnects

We investigated the effects of pulsed electric fields on dielectric breakdown in Cu damascene interconnects. Among the DC, unipolar, and bipolar pulse conditions that were examined, the dielectric lifetime was longest under the bipolar condition because Cu contamination was suppressed due to backward Cu migration. Under the unipolar pulse condition, the dielectric lifetime was enhanced over that under the DC condition, as the pulse frequency increased. These results suggest that the intrinsic breakdown of dielectrics, in addition to Cu contamination, significantly contributes to their reliability. The bond breakdown probability decreased as the unipolar pulse width decreased below the threshold value.