**1. Introduction**

Recent developments in nanoscience and nanotechnology were strongly supported by advances in nanofabrication. Controlled patterning of nanostructured materials has become increasingly important because of the ever-decreasing dimensions of various devices, including those used in electronics, optics, photonics, biology, electrochemistry, and electromechanics (Henzie et al., 2004; Fan et al., 2006). Today, the production of structures with typical dimension in the 1 to 100 nm range with engineered physical and chemical properties is challenging.

Different nano-fabrication techniques have been reported in the literature (Nie & Kumacheva, 2008). Recent examples include optical lithography (Cotton et al., 2009), electron beam lithography (Gonsalves et al. 2009), X-ray lithography (Im et al., 2009), laser writing (Soppera et al., 2008), scanning probe techniques (including optical near-field lithography (El Ahrach et al., 2007), pen nanolithography (Cai & Ocko, 2005), dip-pen lithography (Christman et al., 2009), nanoshaving (Seo & Borguet, 2006) and thermal scribing (Lee et al., 2008)), microcontact printing (Huh et al., 2009), micro-phase separation of block copolymers (Greater et al., 2007), dewetting (Yoon et al., 2008), nanoimprint lithography (He et al., 2009) or electrochemical nanopatterning (Jegadesan et al., 2006). The major remark is that the size of the achievable patterns is strongly dependent of the technique used and can vary between the micrometer to the sub-10 nanometre length scale. This point is a serious limitation when different length scales are needed. Furthermore, in most cases these techniques suffer from different material requirements and limited dimensions of the patterned surface.

In this context, interferometric lithography appears of high interest when periodical patterns are needed. Indeed, interferometric techniques can be considered as massively parallel nanofabrication techniques since patterns can be obtained over large area within a single exposure. Moreover, the recourse to wavelength in the Deep-UV range (DUV corresponds

Fernand Wieder1 and Vincent Roucoules1

<sup>\*</sup> Ali Dirani1,2, Fabrice Stehlin1, Hassan Ridaoui1,3, Arnaud Spangenberg1,

*<sup>1</sup>Institut de Sciences des Matériaux de Mulhouse, CNRS LRC 7228, Mulhouse, France* 

*<sup>2</sup>Université Catholique de Louvain, Division of Bio- and Soft Matter, Belgique* 

*<sup>3</sup>CEA, Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les nanomatériaux / DEHT/ LPCE, Grenoble, France* 

DUV Interferometry for Micro and Nanopatterned Surfaces 245

Interferometry in the DUV range has been enabled by the development of excimer lasers that have two main advantages: first, the use of short wavelengths is an effective way to provide the requested resolution since the period is directly proportional to the wavelength. Secondly, DUV wavelength permits direct writing via photoinduced processes provoked by high-energy photons. Examples of suitable materials for such wavelengths will be given in

On the experimental point of view, one of the difficulties for interferometry in the DUV range is due to the low coherence of available DUV lasers. As an example, typical coherence of ArF lasers is limited to a few hundreds of microns, which justifies efforts to develop

a) b)

c) Fig. 1. Example of interferometric lithography configuration: a) Talbot prism (Bourov et al., 2004), b) Lloyd setup (Raub & Brueck, 2003) and c) achromatic holographic configuration



specific experimental setup for short wavelengths (Figure 1):

the following sections.

(Yen et al., 1992)

248 nm lasers.

with immersion.

to λ<300 nm) allows producing periodic nanostructures with typical dimension down to several tens of nm.

The aim of this chapter is to review some recent works about DUV interferometric lithography nanofabrication. In the first part, a brief introduction to interferometric lithography will allow illustrating its interest and main applications. The second part will be dedicated to applications with organic materials (polymers) that have been widely used for micro and nanopatterning with such a technique. However, organic materials present some inherent limitations that have justified many efforts during the last years to developed inorganic materials prepared by sol-gel technique. This will be the topic of the third part of this chapter.
