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.
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.
EUV lithography has the ability to support 22 nm logic (or 32nm half pitch) node and beyond. Similar to the DUV lithographic systems, partial coherence on EUV lithographic systems can have a big impact on process latitude for critical layers. Thus, it is important to understand the effect of partial coherence on EUV imaging systems. In this paper, process windows with various illumination settings are investigated. The experiments were done using the MET station at the Advance Light Source (ALS). The exposures were targeted for 60 nm, 50 nm, and 45 nm dense features. The outer and inner sigmas of annular illumination varied from 0.2 to 0.8. In addition, dipole, C-quad, and quad illuminations were used to explore the impact of the partial coherence on the process window. Knowledge gained can then be applied to verify lithography models and aid in future tool designs.
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.