Fabrication of small gold bumps (20 ~ 1O0 ~m in size) on silicon substrates were investigated using gold sulfite plating. To improve the stability of the gold sulfite plating bath, the behavior of the decomposition procedures and evaluation of the stabilizer were also studied. It was confirmed that Au metal and Au ~+ ions were produced in the decomposed plating solution. The most effective stabilizer was 2,2'-bipyridine. This greatly improved the stability of the bath. The gold sulfite electrolyte did not attack the photoresist, and straight-walled bumps with 20 Fm in pitch and 20 ~m in height can be obtained.

Electroless silver plating using the oxidation reaction of Co (II) was investigated.Co (II) complexes with ammonia of amines were found to be an effective reducing agent for deposition. Plating reaction was promoted autocatalytically without hydrogen evolution. Deposited silver films displayed excellent optical reflection properties like those of vacuum silver deposits. However, the deposition rate gradually decreased with the reaction time since Co (II) -amine complex ions are readily self oxidized in an air atmosphere and bath life diminished. Bath life can be prolonged with the prevention of Co (II) oxidation in a nitrogen atmosphere.

No abstract

No abstract

No abstract