Method for forming conductive structure, and plating apparatus and plating method

Abstract

A method can form a conductive structure, which is useful for three-dimensional packaging with via plugs, in a shorter time by shortening the conventional long plating time that is an impediment to the practical use of electroplating. The method includes forming a conductive film on an entire surface, including interior surfaces of via holes, of a substrate having the via holes formed in the surface; forming a resist pattern at a predetermined position on the conductive film; carrying out first electroplating under first plating conditions, using the conductive film as a feeding layer, thereby filling a first plated film into the via holes; and carrying out second electroplating under second plating conditions, using the conductive film and the first plated film as a feeding layer, thereby allowing a second plated film to grow on the conductive film and the first plated film, both exposed in the resist openings of the resist pattern.

1 . 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, 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 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; and   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 to thereby fill the via holes and resist openings without defects, an average current value in the second plating conditions being higher than an average current value in the first plating conditions.   
     
     
         2 . The method according to  claim 1 , wherein a composition of the second plating solution is different than a composition of the first plating solution. 
     
     
         3 . The method according to  claim 1 , wherein the upwardly-open via holes have a diameter of 10 μm to 20 μm and a depth of 70 μm to 150 μm. 
     
     
         4 . The method according to  claim 1 , wherein immersing the substrate in the first plating solution is performed while stirring the first plating solution. 
     
     
         5 . The method according to  claim 1 , wherein immersing the substrate in the second plating solution is performed until the second plated film having a flat surface is formed in the resist openings. 
     
     
         6 . The method according to  claim 1 , wherein the first plated film and the second plated film are composed of the same metal. 
     
     
         7 . The method according to  claim 1 , further comprising:
 during the second electroplating, supplying a nitrogen gas into the second plating solution facing a to-be-plated surface of the substrate.   
     
     
         8 . The method according to  claim 1 , wherein a height of the resist pattern is 5 μm to 100 μm. 
     
     
         9 . The method according to  claim 1 , wherein each of the first plated film and the second plated film is composed of copper or a copper alloy. 
     
     
         10 . The method according to  claim 1 , wherein the second electroplating is conducted until the second plated film grows to a point halfway between the surface of the first plated film and a top of the resist pattern, and then third electroplating is carried out under third plating conditions so that a third plated film grows on the second plated film. 
     
     
         11 . The method according to  claim 10 , wherein the third plated film is composed of a metal different from a metal of the first plated film and a metal of the second plated film. 
     
     
         12 . The method according to  claim 1 , wherein the first plating conditions of the first electroplating include an average current density in a range of 0.1 mA/cm 2  to 5.0 mA/cm 2 . 
     
     
         13 . The method according to  claim 12 , wherein the second plating conditions of the second electroplating include an average current density at least twice as large as an average current density of the first plating conditions of the first electroplating. 
     
     
         14 . The method according to  claim 1 , wherein the second plating conditions of the second electroplating include an average current density at least twice as large as an average current density of the first plating conditions of the first electroplating. 
     
     
         15 . The method according to  claim 1 , wherein the first electroplating under the first plating conditions is switched to the second electroplating under the second plating conditions when a surface of the first plated film filling each of the via holes has a concave shape to thereby prevent the surface of the first plated film in each of the via holes from achieving a convex shape with a raised central portion. 
     
     
         16 . The method according to  claim 1 , wherein the additive of the first plating solution includes at least one of a sulfur compound, a polymer, and a nitrogen compound.