An electroplating apparatus for plating a substrate, such as a wafer, uses a substrate holder for detachably holding the substrate. The substrate held by the substrate holder is immersed in a plating solution. When a voltage is applied between an anode and the substrate, electric current flows from the anode to the substrate through the plating solution, whereby a surface of the substrate is plated in the presence of the plating solution.
The substrate holder for use in electroplating has an electrical contact which contacts the to-be-plated surface of the substrate. The substrate holder has a sealing function to prevent intrusion of the plating solution so that during plating of the substrate, the plating solution does not come into contact with the electrical contact of the substrate holder which is immersed in the plating solution. When the substrate holder holds the substrate, a hermetic space is formed in the interior of the substrate holder, and the electrical contact is located in this hermetic space.
If the sealing performance of the substrate holder is lowered, the plating solution may intrude into the hermetic space in the substrate holder and come into contact with the electrical contact. There are several techniques for testing a sealing performance of such a substrate holder, as disclosed in Japanese Laid-open Patent Publication No. 2003-277995 and Japan Patent No. 5782398.