EUV interferometry lithography
Thanks to the good knowledge of the EUV domain and the computing codes developed by the LTM, the objective is to compute and validate the calculations on the optical design and on the dimension acceptance for the interferometer developed by CEA-LETI.
Electromagnetic codes are used to assess the influence of the grating parameters on the EUV light diffracted on the order +/- 1. The diffraction efficiencies on considered orders are then computed. This study allows finding the best value of parameters such as absorber height, silicon layer thickness, surface roughness or material index to obtain the best diffraction efficiency. A measurement campaign carried out with a synchrotron source in Wisconsin (USA) allows testing the grating (built by LETI) capabilities.
Results are very promising and show that pattern prints are possible. Following figure presents 20 nm dense lines printed using EUV synchrotron illumination.
20 nm dense lines obtained by EUV
interferometer using synchrotron illumination
