US Patent 7927960 Method of improving overlay performance in semiconductor manufacture

A method for registering a pattern on a semiconductor wafer with an oxide surface includes etching into the surface four sets of two trenches each. Each trench in a set is parallel to the other. The trenches are configured such that each set forms one side of a box shape. The trenches are overfilled with a first metal layer, the excess of which is removed so that the height of the metal is level with the height of the oxide. An overlay setting is then obtained between a photoresist mask and the filled trenches before depositing a second metal layer over the oxide and trenches. The second metal layer is coated with the photoresist according to the overlay setting.