Low-k fluorinated epoxy hybrimer for oxide thin-film transistors passivation

Abstract

In modern times, Inter layer dielectric(ILD) of inter circuit(IC) in most electronics and display industry is working on developing the low constant materials of passivation layers. The SiO2, SiNx thin film, which is currently used as an inorganic thin film material, has a dielectric constant of 3.9 and 3.7, respectively, and have various disadvantages. The low dielectric constant interlayer dielectric reduces the parasitic capacitance, RC time delay, power consumption, etc. generated between electrodes, which make it possible to increase the device speed and integration. In particular, the low dielectric passivation layer in display device can extend the metal line transparent ITO over the gate by reducing the parasitic capacitance between the conventional ITO pixel electrode and the gate electrode. As a result, the aperture ratio of the active matrix(AM) liquid crystal display(LCD) or the AM organic light emitting diode(OLED) is increased, resulting high contrast ratio with high brightness and an advantage in terms of power consumption. Therefore, the development of a low dielectric constant thin film is considered to a key material essential for improving the electrical characteristics of the oxide TFT device, which is attracting attention as a material in future large size and high resolution displays. Materials that are studied as low-k thin film materials are classified into inorganic, organic and high porous oxidized materials. In addition, low-k materials could classified in two ways: solution process and vacuum process. First, inorganic thin film materials have excellent electrical and chemical properties such as low leakage current, high breakdown voltage and stability to organic solvents, but have a higher dielectric constant than organic and porous materials. On the other hand, organic materials have a low manufacturing cost due to low temperature and solution processes and they have a lower dielectric constant than inorganic thin films. However, due to harmful from chemicals caused breakdown voltage, need to thicker film than other materials and vulnerable to mechanical stress. High porosity materials have investigated due to its much low dielectric constant, but they have disadvantages such as low uniformity to make large scale. In recent years, siloxane based materials, whose exhibit high optical properties, relatively high thermal stability, low dielectric properties and low cost solution process fabrication method, have been investigated to various applications. In particular, the inorganic-organic hybrid material which is synthesized by sol-gel process is chemically bonded between inorganic and organic strongly on a molecular basis. So it is possible to develop the materials that improve the properites of both organic and inorganic materials such as control the dielectric constant, refractive index, surface energy by changing the type of precursor of metal alkoxide or organic group to the appropriate group or by changing the process. In this study, the fabrication and characteristics of low dielectric films for passivation layer of oxide TFT using inorganic-organic hybrimer was studed. I synthesized high condensation fluorinated epoxy-phenyl oligo-siloxane resin and fabricate the hybrimer with low-k. Synthesis process was processed by solution process at low temperauture less than $80\circ C$. Passivation layer was fabricated from fluorinated epoxy-phenyl hybrimer with low dielectric constant less than 2.9. The fabricated hybrimer passivation layer exhibits also high transparency, high thermal stability, low leakage current and improve the electrical performance including bias stability of oxide TFT.