Extreme-ultraviolet multilayer mirrors deposited using radio-frequency-magnetron sputtering: the influence of self-bias voltage on reflectivity and roughness
M. Putero-vuaroqueaux et B. Vidal, Extreme-ultraviolet multilayer mirrors deposited using radio-frequency-magnetron sputtering: the influence of self-bias voltage on reflectivity and roughness, J PHYS-COND, 13(18), 2001, pp. 3969-3976
Mirrors for the imaging optics of extreme-ultraviolet (EUV) lithography sys
tems require optimal reflectivity. In this paper, results on Mo/Si multilay
ers for EUV radiation are reported. The multilayers were deposited using ra
diofrequency-magnetron sputtering; during deposition the self-bias voltages
were measured, and the influence of their variation on the multilayer refl
ectivity and roughness was tested. The samples were characterized using sma
ll-grazing-angle x-ray reflectivity and their performance was evaluated by
measuring the EUV reflectivity at near-normal incidence. The results show t
hat high reflectivity (> 67%) and low roughness values (<2.5 Angstrom) can
be obtained, depending on the stability of the self-bias voltage during dep
osition.