The challenge of the Integrated Circuit size reducing leads to the development of new processes for future years. In the
lithography domain, since several years, the EUV Lithography appears as a possible technique to reach the ITRS
roadmap requirements. The EUV interferometry Lithography is still nowadays an efficient way to study and improve the
EUV resist behaviors. Although the interferometer principle seems to be obvious, the optimization of its use is only
reached regarding some huge constraints. In this work accurate numerical models and experimental studies have been
developped. It shows that some undesirable effects can reduce the interference region and disturb the contrast of the
resist printed lines. The EUV light is identified as the first issue. The beam divergence of EUV light affects the contrast
quality of the fringes. The photometry computation, taking into account the optimum angular source light width is then
detailed. The second cause is the Fresnel diffraction of light due to boundaries of the grating windows. Its
superimposition with diffraction orders induces a damage of local printed interferences. This phenomenon leads to an edge disturbance of the interference fringes. The third cause addressed is the decrease of the interference area by the position of the wafer out of the focal distance. Possible shadowing effects are also shown.
EUV lithography is expected to be inserted for the 32/22 nm nodes with possible extension below.
EUV resist availability remains one of the main issues to be resolved. There is an urgent need to provide suitable tools to accelerate resist development and to achieve resolution, LER and sensitivity specifications simultaneously.
An interferometer lithography tool offers advantages regarding conventional EUV exposure tool. It allows the evaluation of resists, free from the deficiencies of optics and mask which are limiting the achieved resolution.
Traditionally, a dedicated beam line from a synchrotron, with limited access, is used as a light source in EUV interference lithography.
This paper identifies the technology locks to develop a stand alone EUV interferometer using a compact EUV source. It will describe the theoretical solutions adopted and especially look at the feasibility according to available technologies.
EUV sources available on the market have been evaluated in terms of power level, source size, spatial coherency, dose uniformity, accuracy, stability and reproducibility. According to the EUV source characteristics, several optic designs were studied (simple or double gratings). For each of these solutions, the source and collimation optic specifications have been determined.
To reduce the exposure time, a new grating technology will also be presented allowing to significantly increasing the transmission system efficiency. The optical grating designs were studied to allow multi-pitch resolution print on the same exposure without any focus adjustment.
Finally micro mechanical system supporting the gratings was studied integrating the issues due to vacuum environment, alignment capability, motion precision, automation and metrology to ensure the needed placement control between gratings and wafer. A similar study was carried out for the collimation-optics mechanical support which depends on the source characteristics.
Anti-sticking efficiency remains a key issue in nanoimprint lithography. In order to address this problem, a selfassembled
monolayer (SAM) of a fluorinated silane release agent is generally applied to the stamp surface, either in wet
or in vapour phase. We present here the study on vapour deposition of (tridecafluoro-1,1,2,2-tetrahydrooctyl)TriChloroSilane (F13-TCS) and wet and vapour deposition of a commercial product, OPTOOL DSX from Daikin. They are both fluorinated silanes used for the formation of anti-adhesive layers in nanoimprint lithography. Results will be compared in term of anti-adhesion properties and homogeneity for the obtained layers. Characterizations
are made by means of contact angle measurements, Fourier Transform Infra-Red analysis and Atomic Force Microscopy
observations. The vapour phase deposition of F13-TCS allows us to reach surface energies as low as 11mN/m without
increasing initial roughness. OPTOOL DSXTM deposition in wet phase presents comparable results, but with an
increased roughness mainly due to the deposition procedure. The durability of the formed layers was investigated as a
function of number of prints. For both materials, a significant degradation of the anti-adhesion properties occurs after
few imprinted dies.