Preparation and characterization of bulk nanoporous Sn, SnO2 AND Zn

Abstract

Extreme ultraviolet lithography (EUVL) has garnered much attention due to its potential in high-volume manufacturing (HVM) of integrated circuit (IC). This research contributes to the study of EUV source target. It has been stated that in the world of semiconductor future roadmaps, there is a need for the small-sized node on the wafer. It is essential for the source target to produce a short wavelength of 13.5 nm, which has the highest reflectivity for multicoated Mo/Si mirror, around 70%. The laser-produced plasma (LPP) method, driven by 1.06 um neodymium-doped yttrium aluminium garnet (Nd.YAG), carbon dioxide (CO2) laser is suited to achieve short wavelength target sources. Researchers around the world have been intensively searching for the most suitable source target candidate. The current EUV laser system employs liquid tin droplet, which has a weakness of generating debris. This project proposes to produce a source target of a porous nature and of low density. Creating the bulk nanoporous structure is one of the solutions to achieve a low density target, which would make an ideal low-density plasma target. Sn, SnO2 and Zn are chosen due to their potential as EUV and XUV (soft X-ray) source targets that are capable of high conversion. The method of powder metallurgy has been selected and applied in sample fabrication, where this concept has been known to adequately produce highly porous samples. Parameters involved in the bulk nanoporous sample preparation, such as time, diameter, temperature, ratio, pressure, binder selection and others, are crucial and need careful evaluation upon application. This research project is divided into two main parts, namely preparation and characterization. The parameters applied in the preparation process are expected to become the benchmark for reference in future related researches. The high-powered microscope, namely SEM, was used to analyse the characterization of porous structure. Besides that, XRD was performed in studying the phase of the samples along with unknown substances. As for analysing sample impedance, electrical impedance spectroscopy was employed. The selected parameter variation in the preparation process had influenced the result of analysis accordingly. In certain situations, the porous structure displayed a low conductive path, showing some incompatibility in electrical conductivity. The project has produced favourable results in preparing the bulk porous structure, where nanopores have been achieved. From the research, the potential of low-density porous structure has been identified to generate some ideas in overcoming the debris problem for the betterment of future device applications.