Study On Tantalumnitride Diffusion Barrier Of Copper Metallization

With the development of integrated circuits (ICs), metal copper has been areplacement for metal aluminum in high density IC manufacture. But Cu is quitemobile in Si and has poor adhesion to Si or SiO2, which could degrade theperformance of copper interconnect. Therefore, a diffusion barrier layer betweencopper interconnect and Si device is necessary.Tantalum nitride has a series of outstanding properties, such as low resistivity,high melting point, high activation energy of lattice and grain boundary diffusion,and excellent chemical stability, stable interface, which is the optimal choice ofdiffusion barrier materials. So it is very important for the reliability of copperinterconnect to conduct research on the deposition technology, the stability ofbarrier layer and the failure mechanism.In this paper, Tantalum nitride films, Tantalum films, Cu seed layers have beenprepared by reactive magnetron sputtering on Si substrates, and their structure andelectrical properties have been characterized using grazing incidence X-raydiffraction (GIXRD), atomic force microscopy (AFM), Van der Pauw four-probemethod and surface profilometer. The effect of deposition process on structure andsurface morphology of Tantalum nitride films, the diffusion barrier property indifferent high temperature conditions as well as failure mechanism of Cu/barrier/Sifilms were studied.The work can be summarized as follows:The crystal structure of TaN films which were prepared in this paper is f.c.c.and the crystal structure changed with the different processing parameters. theintensity of diffraction peaks became higher when sputtering power and substratetemperature increased, and (111) orientation became dominant with the nitrogenpartial pressure increased; The surface morphology of Tantalum nitride films had aclose relationship with sputtering power and partial pressure of nitrogen, which it isalmost no influenced by the substrate temperature. From the date, we found that theroughness of films increased with an increase of sputtering power and reduces ofnitrogen differential pressure; TaN films'sheet resistance reduced with an increaseof sputtering power ,but sheet resistance increased when partial pressure of nitrogenincrease, at the same time, temperature had little effect on the sheet resistance; The deposition rate decreased with an increase of nitrogen partial pressure whileincreased with increases of sputtering power and substrate temperature. Thenvacuum thermal annealing was performed on Cu/barrier/Si interconnection systems.At 600℃, Ta barrier failed because the formation of TaSi2 that resulted frominterface reaction at Ta/Si. But under the same temperature, there was no phaseformed in TaN barriers while the intensity of diffraction peaks became higher, andthe diffusion barrier property of TaN films still good.TaN films with good diffusion barrier property in high temperature weresuccessfully prepared by reactive magnetron sputtering and meet the requirementsof surface morphology, electrical property for diffusion barrier layer.