IMPACT OF BATH COMPOSITION ON THE PURITY AND ROOM TEMPERATURE ANNEAL CHARACTERISTICS OF THIN COPPER FILM

摘要

Copper was electroplated using several electrolyte compositions to yield thin films with a wide range of room temperature anneal rates. Correlating the measured room temperature anneal rates to the film purity and as-plated resistivity suggests that both as-plated defect density and grain boundary pinning contribute to the measured anneal rates. Plating baths resulting in deposits with higher as plated resistivity yield films with faster anneal rates. This increased anneal rate is interpreted as being the result of higher as-deposited defect density. Plating baths yielding lower in-film impurities produced deposits that also annealed more quickly. This effect is consistent with the reduction of grain boundary pinning allowing more rapid anneal in purer deposits. Anneal rate was found to correlate with the extent of large grain growth within high aspect ratio features, with higher purity, faster annealing films exhibiting larger grains for a given anneal condition. This is relevant for both reducing line resistivity and mitigating failures caused by electromigration in integrated circuits.