Analysis of Plating Solutions Used in the Microelectronic Manufacturing Process Employing Capillary Electrophoresis

Abstract

Capillary electrophoresis (CE) is found to be suitable for determining the concentration of inorganic ions in the copper and gold plating solutions used in the semiconductor manufacturing process. Tris(hydroxymethyl) aminomethane (Tris buffer) with added pyridine dicarboxylic acid (PDC) allows the simultaneous detection of sulfate and copper ions, and adding chromate allows the separation of Cl- from the sulfate matrix. When the methods developed are applied to process chemicals, the new analytical technique agrees well with that of current standard techniques within 99.5% (±0.99). The detection limits of these inorganic ions ranged from 0.99 to 2.32 μg/mL, with relative standard deviations (n=4) ranging from 0.38% to 10.3%. A method to separate sulfite from sulfate was also developed for gold plating solutions. The optimized method successfully permits determination of sulfite and sulfate with concentrations of 4.65% (±0.43) and 4.32% (±0.37), respectively. These methods can lower production cost, raise production efficiency, and increase the chemical lifetime in the semiconductor manufacturing process through simplified process control, waste reduction, and recycling.