We present a method for the optimization of the illumination in soft x-ray (SXR) full-field microscopes. The method
consists of imaging a single periodic grating with a period large compared to the wavelength of the illumination and
obtaining its Fourier spectrum in two orthogonal directions. The analysis of the cut-off frequency along the two
perpendicular directions allows the identification of angled illumination, which can be corrected in-situ by using the
Fourier analysis iteratively. The ability to characterize the illumination conditions and aberrations in the EUV/SXR
microscopes with a fast and simple analysis is critical to achieve the best quality images with the highest spatial
We describe recent advances in the demonstration of table-top full field microscopes that use soft x-ray lasers for illumination. We have achieved wavelength resolution and single shot exposure operation with a very compact 46.9 nm microscope based on a desk-top size capillary discharge laser. This λ=46.9 nm microscope has been used to captured full field images of a variety of nanostructure systems and surfaces. In a separate development we have demonstrated a zone plate microscope that uses λ=13.2 nm laser illumination to image absorption defects in a extreme ultraviolet lithography (EUVL) mask in the same geometry used in a 4x demagnification EUVL stepper. Characterization of the microscope's transfer function shows it can resolve 55 nm half period patterns. With these capabilities, the λ=13.2 nm microscope is well suited for evaluation of pattern and defect printability of EUVL masks for the 22 nm node.
We present results on a table-top microscope that uses an EUV stepper geometry to capture full-field images with a halfpitch
spatial resolution of 55 nm. This microscope uses a 13.2 nm wavelength table-top laser for illumination and
acquires images of reflective masks with exposures of 20 seconds. These experiments open the path to the realization of
high resolution table-top imaging systems for actinic defect characterization.
We have demonstrated ablation of holes with diameter as small as 82 nm in polymethyl methacrylate (PMMA) by
focusing the output of a capillary discharge soft x-ay laser with a Fresnel zone plate. We also report the first
demonstration of laser induced breakdown spectroscopy with soft x-ray laser light.
Images with nanoscale resolution were obtained in both transmission and reflection modes using a full-field microscope
that is illuminated by an extremely compact λ = 46.9 nm (hν; = 26.4 eV) soft x-ray laser. The microscope was used to
image the surface of partially processed silicon semiconductor chips containing periodic patterns of polysilicon and
metal lines. To characterize the microscope, modulation transfer functions were experimentally built for three different
objective zone plates, and images with near-wavelength resolution were obtained.
We have acquired images with sub-38 nm spatial resolution using a tabletop extreme ultraviolet (EUV) imaging system operating at a wavelength of 13.2 nm, which is within the bandwidth of Mo/Si lithography mirrors This zone plate-based, full-field microscope has the power to render images in only several seconds with up to a 10,000 μm2 field of view. The ability to acquire such high-resolution images using a compact EUV plasma laser source opens many possibilities for nanotechnology, including in-house actinic inspection of EUV lithography mask blanks.
We have demonstrated imaging at soft x-ray wavelengths in transmission and reflection modes using high repetition rate table-top soft x-ray lasers. Transmission mode imaging with a resolution better than 50 nm was demonstrated using the output from a 13.9 nm Ni-like Ag laser in combination with condenser and objective Fresnel zone plate optics. Reflection mode imaging of a microelectronic chip with a resolution of 120-150 nm was demonstrated using the illumination provided by the 46.9 nm output from a compact capillary-discharge Ne-like Ar laser. This microscope combines a Schwarzschild condenser and a zone plate objective. The results demonstrate the feasibility of practical nanometer-scale microscopy with compact soft-x-ray laser sources.
We report high resolution imaging results obtained utilizing small-scale extreme ultraviolet laser sources. A compact capillary-discharge pumped Ne-like Ar laser emitting at a wavelength of 46.9 nm was used to demonstrate imaging with nanometer-scale resolution in transmission and reflection modes. We exploited the large photon fluence of this short wavelength laser to obtain high-resolution images with exposure times as short as 1-10 seconds. Images with a spatial resolution better than 140 nm were obtained using the combination of a Sc/Si multilayer coated Schwarzschild condenser and free-standing objective zone plate. Preliminary results of imaging with a 13.9 nm extreme ultraviolet laser light are also discussed.
In this work we report on the damage threshold of ion beam deposited oxide films designed for high peak power short pulse laser systems. Single layers of ZrO2, SiO2, Al2O3, TiO2, and Ta2O5 and multilayers of Al2O
3/TiO2, SiO2/Ta2O5, and SiO2/ZrO2 were grown on polished borosilicate glass substrates using ion beam sputter deposition. Deposition conditions were optimized to yield fully oxidized films as determined from x-ray photoelectron spectroscopy (XPS). Damage threshold testing was performed using an amplified Ti:Sapphire laser producing a train of 120 picosecond pulses at a wavelength of 800 nm. The laser output was focused with a lens to generate fluences ranging from 0.1 to 24 J/cm2. The highest damage threshold of 15.4 J/cm2 was measured for a single layer film of SiO2. The damage threshold of high reflectance and anti-reflection multilayer coatings fabricated for 800 nm applications was evaluated using the same procedure as for the single layer films. Highest damage thresholds of 2.5 and 3.5 J/cm2 were measured for a 6-pair ZrO2/SiO2 high reflectance coating and a 5 layer anti-reflection coating of the same materials.