We describe a table top nanofabrication system that utilizes the coherent Talbot imaging effect and a table-top soft x ray laser to implement a defect-free compact nanolithography tool. The Talbot lithography provides a robust and simple setup capable of printing periodic structures over millimeter square areas free of defects. Test structures were fabricated into metal layers showing a complete coherent extreme ultraviolet lithographic process in a table-top system.
We measured the linewidth of a λ= 46.9 nm neon-like argon capillary discharge soft x-ray laser. A wavefront division
interferometer based on a pair of dihedrons was used to resolve the laser line measuring the variation in the interference
fringe visibility for different optical path differences. We measured a relative linewidths of Δλ/λ = 3-4 10-5. No
significant re-broadening was observed when the length of the laser medium was increased beyond the saturation length
due to effects that homogenizes the line profile.
Reduced replicas of a periodic transparent mask were printed in the surface of a photoresist using Talbot effect. The
transparent mask (or Talbot mask) was composed of an array of unit tiles distributed in a square matrix. The mask was
illuminated by a coherent table top soft X-ray laser. To achieve the demagnification effect, the illumination beam was
reflected in a spherical mirror. At determined positions given by the Talbot distance reduced replicas of the mask were
obtained. The Talbot images produced smaller copies of the mask in the surface of a photoresist. Calculations based on
Kirchhoff-Fresnel theory shows a good agreement with the experimental results. The limitations for this method are
Decreasing the illumination wavelength allows to improve the spatial resolution in photon-based imaging systems and
enables a nanometer-scale spatial resolution. Due to a significant interest in nanometer-scale spatial resolution imaging
short wavelengths from extreme ultraviolet (EUV) region are often used. A few examples of various imaging techniques,
such as holography, zone plate EUV microscopy, computer generated hologram EUV reconstruction, lens-less
diffraction imaging and generalized Talbot self-imaging will be presented utilizing coherent and incoherent EUV
sources. Some of these EUV imaging techniques lead to the high spatial resolution, better than 50nm in a very short
exposure time. The techniques, presented herein, have potential to be used in actinic mask inspection for EUV
lithography, mask-less lithographic processes in the nanofabrication, in material science or biology.
A compact capillary discharge table top soft X ray laser was used for a table top photolithography tool using different
approaches: holographic printing, interferometric lithography and coherent Talbot self imaging. Large areas, of the
order of millimeter square, with periodic and arbitrary patterns were printed in a photoresist in short exposure times.
The proof of principle of the lithographic technique achieved the expected ~100 nm resolution.
The development of tabletop extreme ultraviolet (EUV) lasers opens now the possibility to realize interferometric lithography systems at EUV wavelengths that easily fit on the top of an optical table. The high degree of spatial and temporal coherence and high brightness of the compact EUV laser sources make them a good option for interferometric applications. The combination of these novel sources with interferometric lithography setups brings to the laboratory environment capabilities that so far had been restricted exclusively to large synchrotron facilities.
We report the demonstration of Extreme Ultraviolet Holographic Lithography - EUV-HL - using a compact table top extreme ultraviolet laser. The image of the computer-generated hologram (CGH) of a test pattern was projected on the surface of a sample coated with a high resolution photoresist. Features with a 140 nm pixel size were printed using for the reconstruction a highly coherent table top 46.9 nm extreme ultraviolet laser. We have demonstrated that the combination of a coherent EUV source with a nanofabricated CGH template allows for the extension of nanolithography in an extremely simple set up that requires no optics. The reconstructed image of CGH was digitized with an atomic force microscope, yielding to reconstructions that are in excellent agreement with the numerical predictions.
The volatile character of laser beam and biological media interactions causes difficulties with respect to
prediction of eventual parameters variations of the exposed medium. Accurate evaluation of the laser energy
distribution in biological media helps to forecast the results of exposure. Together with the assumption of
predetermined absorption model it constitutes very efficacious approach of the medium thermal profile estimation
which is crucial with respect to tissue welding process .