To improve the stability of a gold sulfite plating bath, decomposition behavior and evaluation of stabilizing agents was investigated. Stability can be improved by the inhibition of the disproportionation reaction. The most effective stabilizing agents were 2,2'-dipyridine and its derivatives. Addition of 2,2'-dipyridine did not influence the hardness of the deposit, and the stress of the deposited film was significantly decreased.
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.
Glyoxylic acid as an alternative reducing agent for electroless copper plating was investigated. Plating rates and bath stability were superior to that of the formaldehyde bath under standard conditions. The morphologies of deposited copper film were not greatly affected by ethylenediaminetetraacetic acid concentration, and mechanical properties (for instance, the ductility) of deposited films were obtained. The rate of the Cannizzaro reaction with glyoxylate ions was faster than with formaldehyde, but could be reduced by 10 to 40% using KOH instead of NaOH. It was confirmed that the uniformity of hole wall coverage was superior to that of the formaldehyde bath. Glyoxylate ions in the plating bath have no vapor pressure and showed good reducing power in the electroless copper plating. Therefore, glyoxylic acid can replace formaldehyde, and eliminate health and environmental problems resulting from generation of obnoxious fumes.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.97.58.73 Downloaded on 2014-12-15 to IP
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