An apparatus comprising a substrate with multiple electronic devices. An interconnect structure formed on a first side of the substrate interconnects the electronic devices. Dummy TSVs each extend through the substrate and form an alignment mark on a second side of the substrate. Functional TSVs each extend through the substrate and electrically connect to the electronic devices. A redistribution layer (RDL) formed on the second side of the substrate interconnects ones of the dummy TSVs with ones of the functional TSVs. Step heights of the RDL over the functional TSVs are less than a predetermined value, whereas step heights of the RDL over the dummy TSVs are greater than the predetermined value.