The investigation of electroplating deposited copper films for advanced VLSI interconnection

The characteristics of electroplating deposited (EPD) copper films after annealing are investigated by means of sheet resistance, film hardness, film stress, surface roughness, and the chemical mechanical polishing process. Films annealed at 150/spl deg/C showed very similar behavior to those annealed at room temperature for three days in many aspects, including sheet resistance, hardness, surface morphology, and CMP polish rate. Annealing at temperatures higher than 300/spl deg/C resulted in lower sheet resistance, larger grain size, and rougher surfaces, as well as better CMP performance. Atomic force microscopy showed that the surface was rougher as the annealing temperature increased. Better CMP polish rate and uniformity were obtained on fully recrystallized films. Therefore, post-EPD annealing at about 300/spl deg/C to stabilize the copper films is necessary for better CMP process performance.