A method for forming through silicon vias (TSVs) in a silicon substrate is disclosed. The method involves forming a silicon post as an substantially continuous annulus in a first side of a silicon substrate, removing material from an opposite side to the level of the substantially continuous annulus, removing the silicon post and replacing it with a metal material to form a metal via extending through the thickness of the substrate. The substantially continuous annulus may be interrupted by at least one tether which connects the silicon post to the silicon substrate. The tether may be formed of a thing isthmus of silicon, or some suitable insulating material.