Abstract— Amorphous‐silicon (a‐Si:H) thin‐film transistors (TFTs) on soda‐lime glass were fabricated by using a diffusion barrier and a low‐temperature process at 200°C. The silicon nitride barrier was optimized in terms of diffusion blocking effectiveness, film adhesion, and surface finish. TFTs on soda‐lime glass achieved a saturation mobility 0.47 cm2/V‐sec, threshold voltage of 0 V, an off‐current of 7.7×10−11 A, and a sub‐threshold swing of 1.0 V/dec. From diffusion experiments, a 30,000‐hour lifetime for the TFT device at 80°C was estimated, and the robustness of the silicon nitride barrier against long‐term migration of sodium was demonstrated.

IGZO is one of the promising materials being used to make high-mobility TFTs for high-quality displays. However, a-IGZO TFTs have stability issues in addition to limited mobility (<10 cm2/V·s). AKT has made a stable a-IGZO TFT through ESL optimization and plasma treatment of the IGZO interface. AKT a-IGZO ES-TFT shows SS 0.4 ±0.1 V/dec, mobility 10 ±1.0 cm2/V·s, Von 0.25 ± 1.5V over 2200 x 2500 mm2 substrate. BTS stability range under 80oC, ±50V conditions is ~1.5V. Furthermore, another AKT MO ES-TFT shows >30 cm2/V·s mobility using multi-layer structure.

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Silicon Nitride (Si3N4), a structural ceramic, is being increasingly used for various applications such as bearings, rotors, valves, etc., due to its highly useful mechanical and physical properties. To achieve the desired close tolerance and better surface integrity for such applications, abrasive machining using diamond wheel grinding, is primarily used. Due to the extreme mechanical properties of the silicon nitride, sub-surface and surface defects like micro-cavities, micro-cracks, smeared areas and debris are formed on the ground surface of the component due to grinding. The final flexural strength of the components are jeopardized to a greater extent due these surface defects. In this research work, a novel process is developed and established to eliminate/minimize these surface defects. The process involves annealing of defects using continuous wave carbon-dioxide (CW CO2, λ = 10.6μm) laser radiation. The laser is applied as a radiation source to selectively soften and reflow the secondary non-Si3N4 phase material to fill/anneal the defects present in the surface and sub-surface. Experiments were performed at three different power densities and at a constant scanning speed in air ambient. Power densities and scanning speed were selected based on the output of the model. It is found during the investigation that the laser treatment reduces the surface roughness and increases the micro-hardness without any change in the surface stoichiometry. Also, the sub-surface and surface defects are minimized and the flexural strength, which is an important property for the related applications, is found to be increased after treatment. The detrimental influence of machining defects on the mechanical failure of the sample during the four-point bend testing was found to be significantly reduced.

Replacing the current non‐alkali glass with soda lime glass can significantly reduce the cost of the current TFT‐LCD module. One key step in manufacturing is to make TFT backplane on soda lime glass substrate. In this work, we demonstrate low temperature a‐ Si thin film transistor (TFT) at 200°C on soda lime glass. with the use of SiNx barrier to prevent sodium contamination, we show the TFT properties can be improved significantly and achieve TFT of saturation mobility 0.47cm2/Vs, threshold voltage 0V, off current 77×10−11 A, sub‐threshold swing 1.0 V/dec. We also show that our TFT device has comparable or better threshold voltage stability as compared to those made in non‐alkali glass. Finally, we show the robustness of SiNx barrier against long term sodium migration.