Flared and non-flared metallized deep vias having aspect ratios of about 2 or greater are provided. Blind vias have been fabricated in silicon substrates up to a depth of about 300 microns, and flared through vias have been fabricated up to about 750 microns, the approximate thickness of a silicon substrate wafer, enabling the formation of electrical connections at either or both ends of a via. In spite of the depth and high aspect ratios attainable, the etched vias are completely filled with plated copper conductor, completing the formation of deep vias and allowing fuller use of both sides of the substrate.