Thin film silver deposition by electroplating for ULSI interconnect applications

Abstract

Ag seed layers were pretreated with 1 : 1,000 diluted nitric acid cleaning solution for 60 s to obtain a clean and oxide-free Ag surface. When an applied potential was less than -800 mV in Ag electroplating, the deposition rate was over 2,000 angstrom/min and the resistivity of Ag deposit was 1.80 mu Omega.cm. But the deposit film became rougher with a negative increase in the potential, and it was also observed through measuring the double layer capacitance. The resistivity of Ag film annealed at 350 degrees C for 30 min was decreased from 1.80 mu Omega.cm to 1.67 mu Omega.cm and the agglomeration of Ag grains was not observed on the surface of the annealed Ag films. To reduce the surface roughness, thiourea was added in the electrolyte and it was decreased below 15 nm.