The extreme ultraviolet (EUV) performance of Mo/Y multilayer mirrors is known to be dependent on the base pressure before deposition. In this work, Mo/Y multilayers were fabricated at non-ultrahigh vacuum system with a base pressure of 8.0 x 10(-4) Pa to 2.0 x 10(-5) Pa. The multilayer structure and corresponding EUV reflectance were measured while a maximum value of 36% was achieved at lambda = 11.3 nm (E = 110 eV). Thermal stability of the fabricated multilayer was studied by annealing the sample at different temperatures from 100 degrees C to 500 degrees C. Grazing incidence X-ray reflectance measurements and high resolution transmission electron microscopy revealed that the layered structure and its hard X-ray reflectivity were preserved although the interface area was increased at elevated temperatures. The broadened interfaces can be explained by a solid state amorphization effect. Unlike the reported results before, the multilayer period was almost constant during annealing up to 500 degrees C, indicating a better thermal stability. (C) 2015 Elsevier B.V. All rights reserved.