Compensating film stress in silicon substrates for the Lynx X-ray telescope mission concept using ion implantation

摘要

Ion implantation is used to correct figure errors resulting from film stress in thin silicon mirror substrates. The Lynx mission concept requires mirrors with extremely small figure errors and excellent X-ray reflectivity, and only a small portion of the mirror error budget may be allocated to distortion from film stress. While reducing film stress in itself is ideal, compensation of film stress may be required. In addition, compensation, in combination with other film stress reduction techniques, may allow freedom in making coatings with optimal x-ray performance while minimizing distortion. Ion implantation offers a rapid method of applying a precise stress distribution to the backside of a mirror, which may be used to compensate for a uniform or non-uniform film stress. In this paper, we demonstrate the use of ion implantation to achieve a roughly 10x reduction in deformation from film stress, and that the stress from ion implantation is stable over at least five months.