Plating apparatus and plating method

A method for forming a conductive structure having via plugs for use in three-dimensional packaging, comprising:

• preparing a substrate having upwardly-open via holes each having a diameter in a range of 10 μm to 20 μm and a depth of 70 μm to 150 μm, a conductive film formed on an entire surface of the substrate, including interior surfaces of the via holes, and a resist pattern formed at a predetermined position on the conductive film;
• carrying out first electroplating under first plating conditions, using the conductive film as a feeding layer, so as to fill the via holes with a first plated film to form the via plugs, the first electroplating including immersing the substrate in a first plating solution containing an additive for suppressing plating growth while stirring the first plating solution to suppress the plating growth at entrances to the via holes, an electric current in the first plating conditions is one of a constant current, a stepwise current, or a pulse current;
• after filling the via holes with the first plated film, carrying out second electroplating under second plating conditions, using the conductive film and the first plated film as a feeding layer, by immersing the substrate in a second plating solution so as to grow a second plated film on the first plated film and on a portion of the conductive film exposed in resist openings of the resist pattern until the second plated film having a flat surface is formed in the resist openings to thereby fill the via holes and resist openings without defects, the first plated film and the second plated film being composed of the same metal, an average current value in the second plating conditions being higher than an average current value in the first plating conditions;
• and
• during the second electroplating, supplying a nitrogen gas into the second plating solution facing a to-be-plated surface of the substrate.