Search

In this study, the effect of rheological properties of Cu nano/micro (NP/MP)-inks with various amounts of dispersant on the print-ability and sinter-ability for flash light sintering was investigated. The rheological properties such as viscosity, viscoelasticity and thixotropic index of Cu NP/MP-inks were measured using a rheometer. The fabricated Cu NP/MP-inks were printed on polyimide substrate using a screen printing method. The 3D profile of printed Cu NP/MP-ink pattern was measured using surface profiler. In order to sinter the printed Cu NP/MP-inks, flash light sintering technique was employed. The flash light irradiation conditions (pulse power, pulse number, on-time, and off-time) were optimized to obtain the high sintering characteristic of Cu NP/MP-inks. In order to characterize the microstructures and transformation crystal phase of the sintered Cu NP/MP-inks, scanning electron microscopy, focused ion-beam and X-ray diffraction analysis were performed. From the results, the optimal sintered Cu NP/MP-ink film had a 6.16 μΩ·cm resistivity and 5B level of adhesion strength.

Transparent conducting electrodes (TCEs) are fabricated through the flash light sintering of reverse-offset printed Ag mesh patterns. Interestingly, the narrower printing lines require a higher flash light energy to obtain an equivalent sheet resistance even if the same Ag nanoparticle ink is used. The microstructural development of sintered Ag nanoparticles is also retarded with the decrease of line width after the same flash light sintering. The temperature calculation in the Ag mesh patterns clearly reveals that heat dissipation is affected by the print dimension. To improve the performance of Ag mesh TCEs with 3 μm wide lines, a preheating step comprised of multi-pulses is inserted before a main flash light sintering. The multi-pulsed flash light sintering is effective in decreasing the sample temperature and in removing the substrate damages or microstructural defects. As a result, the flash light-sintered Ag mesh TCEs shows a sheet resistance of 27 Ω/□ and an optical transmittance of 84.7% including an optical transmittance of substrate.

In this study, an intense pulsed light (IPL) process for annealing an indium-gallium-zinc-oxide (IGZO) semiconductor was conducted via flash white light combined with near-infrared (NIR) and deep-ultraviolet (DUV) drying to form a thin-film transistor (TFT). The IGZO thin-film semiconductor was fabricated using a solution-based process on a doped-silicon wafer covered with silicon dioxide. In order to optimize the IPL irradiation condition for the annealing process, the flash white light irradiation energy was varied from 70 to 130 J/cm2. Drying by NIR and DUV irradiation was employed and optimized to improve the performance of the TFT during IPL annealing. A TFT with a bottom-gate and top-contact structure was formed by depositing an aluminum electrode on the source and drain on the IPL-annealed IGZO. The electrical transfer characteristic of the TFT was measured using a parameter analyzer. The field effect mobility of the saturation regime and on/off current ratio were evaluated. Changes of the metal-oxide bonds in the IGZO thin film were analyzed using X-ray photoelectron spectroscopy to verify the effect of NIR and DUV drying and IPL annealing. Also, the distributions of the carrier concentration on the IPL-annealed IGZO were measured through a hall-effect system to deeply investigate the transition of the electrical characteristic of the TFT. From the results, it was found that the bond between oxygen and the gallium compound was activated via DUV irradiation. The NIR- and DUV-assisted IPL-annealed IGZO-based TFT showed highly enhanced electrical performance with a 7.7 cm2/V·s mobility and a 3 × 106 on/off ratio.