Method for forming film layer on substrate

An apparatus and a method for depositing a film layer that may have minimum contribution to overlay error after a sequence of deposition and lithographic exposure processes are provided. In one example, a method includes positioning a substrate on a substrate support in a process chamber, and flowing a deposition gas mixture comprising a silicon containing gas and a reacting gas to the process chamber through a showerhead having a convex surface facing the substrate support or a concave surface facing the substrate support in accordance with a stress profile of the substrate. A plasma is formed in the presence of the deposition gas mixture in the process chamber by applying an RF power to multiple coupling points of the showerhead that are symmetrically arranged about a center point of the showerhead. A deposition process is then performed on the substrate.