The Fifth International Workshop on Physical Chemistry of Wet Etching of Semiconductors (PCWES 2006)

Abstract

The biannual Workshop on Physical Chemistry of Wet Etching of Semiconductors (PCWES) was held in Saarbrücken, Germany in June 2006 for the fifth time in its history. The event was initiated in 1998 by Miko Elwenspoek from Twente University. It is a dedicated workshop with a typical attendance of about 30 scientists with multidisciplinary backgrounds from all parts of the world working in the field. Starting off in Holten in The Netherlands in 1998, subsequent workshops have been held at Toulouse, France in 2000, Nara, Japan in 2002, and Montreal, Canada in 2004.The initial focus was upon anisotropic etching of silicon in alkaline solutions, including surface topology, modelling aspects and applications. This process has found a wide range of applications in microsystems technology (MST), i.e. in the fabrication of microelectromechanical systems (MEMS). Most prominently, it provides the technological basis for bulk micromachining. More recently, other semiconductors such as germanium, III-V compounds and, particularly, wide-bandgap materials have started to enter the field. Furthermore, electrochemical aspects have gained in importance and the formation of porous silicon has also become a considerable part of the programme. From the very beginning up to the present time there was and is a strong focus on illumination of the underlying mechanism of crystallographic anisotropy, as well as on the understanding of electrochemical and dopant-induced etch stop phenomena.The fifth workshop, presented in Saarbrücken, included a total of twenty four contributions, six of which were as posters. Five of these are included in this partial special issue of Journal of Micromechanics and Microengineering as full length papers after having undergone the standard review process.The selection of contributions starts with the first invited paper given by M Gosalvez et al, resulting from a collaboration between Nagoya University, Japan and Helsinki University of Technology, Finland. It provides an atomistic point of view on the etching of the principal crystal surfaces of silicon. The step flow process and step bunching are explained in considerable detail, as well as effects of metal impurities. Simulation aspects of this approach are discussed in the second paper, also headed by M Gosalvez. They are based on a kinetic Monte Carlo scheme.The third contribution, from Z-f Zhou et al from the Southeast University in Nanjing, China also focuses on simulation aspects of anisotropic silicon etching. It proposes a novel 3-D cellular automata approach which is capable of describing the behaviour of high index planes in an efficient way. By choosing a dynamic algorithm, the programme gains speed and uses memory efficiently.The focus of the final two papers is on photoelectrochemical aspects of etching. D H van Dorp and J J Kelly from the University of Utrecht, The Netherlands describe the photoelectrochemistry and the etching behaviour of SiC in KOH. Silicon carbide is particularly attractive for harsh environment applications, due to its high chemical inertness. Therefore it is very difficult to etch purely chemically and can only be attacked by a light-induced process.Finally, F Yang et al from the Hahn-Meitner-Institut and ISAS Institute in Berlin, Germany describe an experiment of anodic oxide formation and subsequent etch back on (111) silicon surfaces in a NH4F solution. By monitoring the photoluminescence intensity and the photovoltage amplitude, effects of interface recombination and surface charging can be observed and characterized at the different steps of preparation.In total, the five papers provide a very fine overview of current activities and areas of interest in the field of wet chemical etching of semiconductors. The next PCWES workshop will be held in Asia in 2008.