Abstract: A method for manufacturing an interposer provides for disposing a lower insulating layer on a second surface opposite to a first surface of an interposer substrate. A first alignment key on the first surface is aligned with a first photomask. The lower insulating layer is patterned with the first photomask to form a lower circuit pattern and a second alignment key on the second surface. A lower metal layer is formed on the lower insulating layer. The second alignment key is aligned with a second photomask and a photoresist layer is patterned on the lower metal layer to expose the lower circuit pattern using the second photomask.