COPPER ELECTROPLATING ONTO SILICON WAFERS USING HIGH-FREQUENCY ACOUSTIC STREAMING

摘要

As line widths are continuously reduced in integrated circuits, the microelectronics industry will soon need to electrodeposit Cu into deep submicron trenches. This provides processing challenges such as adequate sidewall coverage and gap fill. In order to either reduce or eliminate the use of additives, electrodeposition of Cu was investigated using an industrial electroplating tool which has been fitted with transducers for sonication at 0.7 MHz. Sonication improves mass transfer to the surface, provides improved gap fill, and affects electrodeposit properties such as surface roughness. Cu electrodeposition was investigated onto patterned 0.30-μm Si wafers onto which Ta barrier and Cu seed layers had been deposited. The deposit surface roughness and gap fill have been investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Complete gap fill without additives appears to be achieved at high sonication intensities and low current densities.