Patterning issues for the fabrication of sub-micron memory capacitors' electrodes
This paper describes some of the key issues associated with the patterning of metal electrodes of sub-micron (especially at the critical dimension (CD) of 0.15 μm) dynamic random access memory devices. Due to reactive ion etching lag, the Pt etch rate decreased drastically below the CD of 0.20 μm and thus K-th storage node electrode with the CD of 0.15 μm could not be fabricated using the Pt electrodes. Accordingly, we have proposed novel techniques to surmountly-the above difficulties. The Ru electrode cannot for the stack-type structure is introduced and alternative multischemes based on the introduction of the concave-type selfstructure upto using semi-Pt or Ru as an electrode material are outlined respectively.
High-Temperature Etching of PZT/Pt/TiN Structure by High-Density ECR Plasma
Submicron patterning technologies for the PZT/Pt/Ti/TiN/Ti structure with a spin on glass (SOG) mask were demonstrated using a high-density ECR plasma and a high substrate temperature above 300° C. A 30%-Cl2/Ar gas was used to etch a lead zirconate titanate (PZT) film. No deposits remained, which resulted in an etched profile of more than 80°. A 40%-O2/Cl2 gas was used to etch a Pt film. The etching was completely stopped at the Ti layer. 30-nm-thick deposits remained on the sidewall. They were removed after dipping in hydrochloric acid. The etched profile of a Pt film was more than 80°. The Ti/TiN/Ti layer was etched with pure Cl2 gas. The size shift from the SOG mask was less than 0.1 µ m. Interdiffusion between SOG and PZT was not detected by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM-EDX) analysis.
Science fairs as learning tool for teaching excellence
Science fairs are usually considered to be a pedagogical and cultural activity that involves the students actively. Gifted students need challenges to further develop their skills while maintaining the motivation level. Science fairs may provide the informal environment that will request and allow these students of excellence to challenge themselves by developing a scientific research project. Despite being well known in different countries, in Portugal first steps are being made on the use and implementation of science fairs as effective pedagogical tool. In this work, we will present a 4 years study that was developed on a Portuguese school with the main goal of evaluating the advantages of this informal way of teaching. The study includes an analysis of the evolution of the students’ knowledge that have participated, or visited, the different science fairs. Some advices for the implementation of these projects will be given. The motivation of the students was monitored as well as the knowledge and skills effectively improved by this activity.