Etching a substrate: processes – Nongaseous phase etching of substrate – Etching inorganic substrate
Patent
1998-10-02
2000-12-05
Gulakowski, Randy
Etching a substrate: processes
Nongaseous phase etching of substrate
Etching inorganic substrate
216 13, 216106, 252 795, B44C 122, C09K 1300
Patent
active
061562211
ABSTRACT:
The present invention is a persulfate etchant composition especially useful for dissolving copper during fabrication of microelectronic packages. The etchant is characterized by its ability to selectively etch copper in the presence of nickel, nickel-phosphorous and noble metal alloys therefrom. Furthermore, no deleterious galvanic etching occurs in this etchant-substrate system so that substantially no undercutting of the copper occurs. The combination of high selectivity and no undercutting allows for a simplification of the microelectronic fabrication process and significant improvements in the design features of the microelectronic package, in particular higher density circuits. The persulfate etchant composition is stabilized with acid and phosphate salts to provide a process that is stable, fast acting, environmentally acceptable, has high capacity, and can be performed at room temperature. A preferred etchant composition is 230 gm/liter sodium persulfate, 3 volume % phosphoric acid and 0.058 molar sodium phosphate dibasic.
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Plating, p. 742 (1955).
Covert, deceased Kathleen L.
Lauffer John M.
Moschak Peter A.
Ahmed Shamim
Fraley Lawrence R.
Gulakowski Randy
International Business Machines - Corporation
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