Etching process to selectively remove copper plating seed layer
Write head coils for magnetic disk systems are commonly formed through electroplating onto a seed layer in the presence of a photoresist mask. It is then necessary to remove the seed layer everywhere except under the coil itself. The present invention achieves this through etching in a solution of ammonium persulfate to which has been added the complexing agent 1,4,8,11 tetraazundecane. This suppresses the reduction of Cu++ to Cu, thereby increasing the dissolution rate of copper while decreasing that of nickel-iron. Two ways of implementing this are described&#8212;adding the complexing agent directly to the ammonium persulfate and introducing the 1,4,8,11 tetraazundecane through a dipping process that precedes conventional etching in the ammonium persulfate.
Headway Technologies, Inc.
H G H Y C G G F
H05K G11B H05K Y10T C23F G11B G11B F16B
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Wensen Jei-Wei Kochan Xuehua Si-Tuan Henry C.
Li Chang Ju Wu Lam Chang