Internal Stresses in Mo/Y Multilayer Mirrors

Mo/Y multilayer mirrors designed to operate in the range of 9–11 nm are considered. The dependence of the internal stress of such mirrors on the molybdenum fraction is studied for the first time. It is shown that structures with zero stress are characterized by a reflection coefficient of about 6%. The experimentally obtained maximum reflection coefficient (30%) corresponds to a stress of –160 MPa. The influence of a buffer layer of boron carbide on the internal stress and reflectance factor of the Mo/Y mirrors is investigated. A Cr/Y structure is proposed for compensation of elastic deformations of the substrate in manufacturing highly reflective Mo/Y multilayer mirrors.