Process and apparatus for electroplating microscopic features uniformly across a large substrate

A process for electroplating metal features onto a substrate having a top side including a plating surface comprising:

• providing a plating tank with a bottom, side walls, a front wall and a back wall and containing an electroplating bath with an anode at a positive voltage,
• placing a substrate to be electroplated into the electroplating bath,
• connecting surfaces to be plated to a first cathode which is at a first negative voltage,
• providing agitating means for agitating the electrolyte inside the tank, the agitating means including a paddle and suspension means for reciprocating the paddle in the plating bath along a paddle path between the front and back walls and parallel to the surfaces to be plated in very close proximity thereto with the paddle path being spaced on the order of 4 mm from the substrate,
• supporting a second cathode including a partially open screening electrode at a second negative voltage, the screening electrode being located in close proximity to the first cathode and to the substrate in juxtaposition therewith between the substrate and the paddle path, the structure of the screening electrode being selected from the group consisting of a plating mesh, an aperture plate, and an array of parallel wires, whereby the portion of the second cathode with the partially open screening electrode maintains the second cathode voltage at a substantially uniform value across the substrate, thereby dominating the electropotential in the bath across the total surface area of the substrate.

Apparatus for electroplating metal features onto a workpiece comprising a substrate having a top side including a plating surface comprising:

• a plating tank with an electroplating bath and an anode in the bath, with the anode being connected to a positive voltage,
• means for placing a substrate having plating surfaces to be electroplated in the electroplating bath,
• means for connecting the substrate to a first cathode, with the first cathode being connected to a first negative voltage,
• agitating means for agitating the electroplating bath inside the tank, the agitating means including a paddle and suspension means for reciprocating the paddle along a paddle path parallel to the plating surfaces in the plating bath,
• a second cathode connected to means for supplying a second negative voltage located between the plating surfaces and the paddle path, and
• a portion of the second cathode having openings therethrough extending across the plating surfaces of the substrate and the openings therethrough being positioned between the substrate and the anode with the second cathode being in close proximity to the substrate and juxtaposed therewith.

Apparatus for electroplating metal features onto a substrate having a top side including a plating surface comprising:

• a plating tank with a bottom, side walls, a front wall and a back wall for containing an electroplating bath,
• an anode in the bath connected to a positive voltage,
• means for placing a substrate to be electroplated into the electroplating bath,
• means for connecting surfaces to be plated to a first cathode which is connected to a first negative voltage,
• agitating means for agitating the electroplating bath inside the tank, the agitating means including a paddle and suspension means for reciprocating the paddle in the plating bath between the front and back walls along a paddle path parallel to the surfaces to be plated in very close proximity thereto,
• means for supporting a second cathode juxtaposed with the substrate, with the second cathode being positioned between the substrate and the paddle path, and with the second cathode including a partially open screening electrode selected from a plating mesh and aperture plate and parallel wires proximate to the substrate, and
• means for connecting the second cathode to a second negative voltage.

A plating apparatus, comprising:

• an electroplating tank with front and back walls
• an anode connected to a positive voltage located in the tank,
• a thief electrode located in the tank,
• means for connecting a workpiece as a first cathodes
• means for locating the workpiece behind the plane of the thief electrode and on the opposite side of the plane of the thief electrode from the anode in the tank,
• agitating means for agitating the electrolyte inside the tank, the agitating means including a paddle and suspension means for reciprocating the paddle along a paddle path in the plating bath between the front and back walls parallel to the surfaces to be plated, the paddle path being spaced on the order of 4 mm from the workpiece,
• the thief electrode including a mesh type portion connected as a second cathode above and adjacent to the workpiece with the mesh type portion being in close proximity to the workpiece and in juxtaposition therewith located between the workpiece and the paddle path, and
• the workpiece and the thief electrode including the mesh type portion being connected to at least one power supply means for supplying negative voltages.