the back side of the substrate 10 may be protected by the substrate holder 12 the substrate holder 12 is immersed in the etching solution 16 the substrate 10 is moved preferably in a rotating fashion in the etching solution using the substrate holder 12 or the supporting structure 15 the anode 14 may be part of an electroplating apparatus the anode 14 may be connected to the negative lead of the power supply 22 through line 19 the substrate holder 12 may be connected to the positive lead of the power supply 22 through line 22 a negative potential is applied to the anode 14 and a positive potential is applied to the substrate 10 preferably a positive potential is applied to an exposed surface of the substrate 10 the potential across the substrate and anode causes current flow i e gold ions flow from the substrate to the anode etch rate is monitored and controlled with an amp meter 24 by measuring the current flow in the tank 18 after a period sufficient to etch away the seed layer of gold the power supply is turned off the substrate 10 is moved to a hot deionized 34 di 34 water and rinsed the substrate is then blow dried and inspected gap space and gold thickness are measured if the seed layer of gold is not completely etched clean the substrate is again etched in the.