A method of depositing a metallization structure (1) comprises depositing a TaN layer (4) by applying a power supply between an anode and a target in a plurality of pulses to reactively sputter Ta from the target onto the substrate (2) to form a TaN seed layer (4). A Ta layer (5) is deposited onto the TaN seed layer (4) by applying the power supply in a plurality of pulses and applying a high-frequency signal to a pedestal supporting the substrate (2) to generate a self-bias field adjacent to the substrate (2).