Abstract
Extreme ultraviolet (EUV) lithography has being developed as a promising fabrication technology suitable for printing features with design scales of smaller than 40 nm. The optical elements used in this system require high surface accuracy of 0.1 nm rms. Moreover, substrates of the elements must be low-thermal-expansion materials because EUV light is easily absorbed in matter, accordingly converted to heat. In previous studies, we demonstrated elastic emission machining (EEM) which is well known as a non-contact machining using a fluid mixture of pure water and powder particles has sufficient figuring and smoothing capability for the fabrication of EUV optics. Following these examinations, optimum processing conditions of EEM were investigated. The relationship between the removal rate and the concentration of powder particles in the fluid mixture was tested. As a result, the removal rate was not found to be proportional to the concentration. In this study, this fact is analyzed and its cause is discussed from the viewpoint of the particle behavior. Particle behavior at the EEM processing point is evaluated using the state of the fluid flow calculated by elasthydrodynamic lubrication theory. Accordingly, the relationship between the removal rate and the particle behavior was indicated.
