B.A.C. Rousseeuw

Extreme UV lithography: a new laser plasma target concept and fabrication of multilayer reflection masks

Results are reported on the development of a laser plasma source and the fabrication of multilayer reflection masks for extreme ultra-violet lithography (EUVL). A new concept of a target for a laser plasma source is presented including experimental evidence of elimination of macro debris particles from the source. Concerning the fabrication of reflection masks, a new method is described involving a two-layer absorber system protecting the Mo-Si structure against etching damage.

Soft x-ray projection lithography using a high repetition rate laser-induced x-ray source for sub- 100 nanometer lithography processes

Abstract In this paper we present the status of a joint development programme on soft x-ray projection lithography (SXPL) integrating work on high brightness laser plasma sources, fabrication of multilayer x-ray mirrors, and patterning of reflection masks. We are in the process of optimization of a laser-plasma x-ray source and measured the conversion-efficiency of laser light into x-rays. Furthermore we present results of etching patterns in x-ray reflection masks and we discuss improved deposition techniques to produce multilayer coatings with enhanced reflectivity.

Growth and characterisation of organic multilayers on gold grown by organic molecular beam deposition

Abstract In this contribution, we discuss the growth and characterisation of molecular layers for the formation of oligo-azomethine. The substrate is Au(111) on mica. Monolayers of 4-aminothiophenol are deposited by self-assembly from solution (SAM) or by evaporation in vacuum, both techniques establishing chemisorption of the oligomer on the substrate through a covalent sulphur-gold bond. This is followed by evaporation of terephthalaldehyde in vacuum employing imine-formation (−N=C−) by condensation polymerisation as a starting sequence of an in-situ synthesis of the oligo-azomethine. In-situ ellipsometry and quartz crystal frequency measurements are used to monitor the growth. Chemical surface composition is verified by X-ray photoelectron spectroscopy. Morphology and electronic properties are examined ex-situ by scanning tunnelling microscopy. Scanning induces pit formation on the SAM films, whereas no pits are found on the evaporated films. On the SAM films, a staircase-like pattern in tunnel spectroscopy I–V curves is observed while the evaporated films show diode-like behaviour.

Fabrication and analysis of extreme ultraviolet reflection masks with patterned W/C absorber bilayers

We report on a novel procedure developed for the fabrication of reflection masks for extreme ultraviolet lithography. The procedure involves the deposition and patterning of an absorber bilayer (40 nm W and 25 nm C) on Mo/Si multilayer blanks. The C layer is used to protect the underlying Mo/Si multilayer structure during processing and repair. The pattern is written with an e-beam pattern generator into EPR resist and is transferred into the absorber bilayer with three consecutive rf etching processes. We have investigated the effect of the full mask making procedure on the multilayer reflectivity using 13 nm radiation. The procedure causes some oxidation of the top Si layer of the multilayer, an effect which is confirmed by XPS measurements. However, the method does not affect the multilayer reflectivity to within narrow tolerances. The profiles of patterns in the absorber layer are inspected with a SEM, showing patterns with a feature size of 250 nm and side wall slope angles of 80°. An indication is f...

Synthesis of siloxanes containing acid-sensitive side groups

Abstract New siloxanes with acid-sensitive substituents have been synthesized by means of hydrosilylation, starting from methylhydrosiloxanes. Details of the preparation and characterization are reported. p -t-Butoxycarbonyloxystyrene, p -t-butoxystyrene and t-butyl methacrylate turned out to be excellent reagents in these experiments. 1 H, 13 C and 29 Si nuclear magnetic resonance techniques were used for characterization. The ratio between α and β addition appears to be strongly dependent on the substituents at the vinyl group of the organic moieties.

Template patterning of YBa 2 Cu 3 O 7

Abstract We demonstrate the use of thin chromium layers to define structures in YBa 2 Cu 3 O 7 deposited by laser ablation. The chromium reacts with copper to form an insulating crystalline compound containing copper and chromium in equal amounts. Although the reaction will proceed up to approximately 1 μm into the defined pattern, the formation of a crystalline compound means that the extent of the reaction is limited by the availability of chromium. We have defined large-area, regular grids of tiny chromium pads, yielding a grid of insulating islands of approximately 600 nm in size after YBa 2 Cu 3 O 7 deposition. Electrical measurements show the influence of such a pattern on the R-T characteristics of the YBa 2 Cu 3 O 7 .

FUNCTIONALIZATION OF POLYSILSESQUIOXANES

New polysilsesquioxanes are prepared by incorporating tetrahydropyranyl moieties into silsesquioxanes. These polymers, which are soluble in organic solvents, are synthesized by means of HCl-catalysed reactions.

Growth and scanning tunneling spectroscopy of self-assembled π-conjugated oligomers

Abstract A novel technique for the fabrication of π-conjugated oligomers bonded to a substrate is presented. On a gold substrate, monolayers of small monomeric organic units are alternately deposited by self-assembly . In each deposition step, polymerization takes place at the interface between two monolayers through a condensation reaction. Chain growth is verified and analyzed by ellipsometry, gas chromatography, mass-spectrometry and X-ray photoelectron spectroscopy. The layers are also imaged by scanning tunneling microscopy (STM), and current–voltage spectra have been recorded by STM in interrupted feedback. The salient features for the oligomers, as compared to the bare gold substrate, can be explained by the presence of a thin (∼1 nm) layer of semiconductor with ∼2 eV energy barrier for tunneling electrons.

ESR study of the steric and spin density effects on the radicals derived from 4-alkoxy-2,3,5,6-tetramethylphenols

Abstract The phenoxy and cation radicals derived from 4-methoxy- (2) and 4-ethoxy-2,3,5,6-tetramethylphenol (3) have been investigated. The phenoxy radicals (PA-2, PA-3) show β-alkoxy proton splittings of 0.0 and 0.28 G, whereas the cation radicals A-2 and A-3 have β-alkoxy splittings of 2.97 and 2.65 G. These results are interpreted in terms of orthogonal alkoxy groups for the phenoxy radicals and almost coplanar alkoxy groups for the cation radicals. The conformation of the ethoxy group in the cation radical A-3 is also different from all other ethoxy groups studied to date, due to the steric effects of the two ortho methyl groups. The cation radicals A-2 and A-3 also exhibit line width alternation effects which are attributed to the restricted rotation of the hydroxyl group. Simulations of the spectra have been carried out for A-2 and A-3 in CH3NO2 and CH2Cl2CH3NO2 mixtures. An interesting solvent effect was also observed for A-2.

The Application of Phosphazene Containing Polymers as Negative Resists in Microlithography

New terpolymers containing phosphazene, epoxy and silicon moieties have been synthesized which were used as negative resists in microlithography. In addition to synthesis and characterization, lithographic properties are discussed.