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Rotary electroplating cell with controlled current distribution

Image Number 2 for United States Patent #4304641.

An apparatus and a method for rotary electroplating a thin metallic film having a uniform thickness and composition throughout. The apparatus includes a flow-through jet plate having nozzles of increasing size and uniformly spaced radially therethrough, or the same sized nozzles with varying radial spacing therethrough so as to provide a differential flow distribution of the plating solution that impinges on the wafer-cathode where the film is deposited. The spacing and size of the nozzles are critical to obtaining a uniform thickness. The electrical currents to the wafer and to the thieving ring are controlled by variable resistors so as to keep the electrical current to the cathode constant throughout the plating process. In a preferred embodiment the flow-through jet plate has an anode associated therewith in which the exposed area of the anode is maintained at a constant amount during the deposition. This method can simultaneously deposit with a uniform thickness and composition elements having a minimum gap or part size of 1 micrometer or less.

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