Preparation Of Tantalum-Ruthenium Target And Study On Tantalum-Ruthenium-Nitride Diffusion Barrier Films

With the increasing integration of microelectronic devices,the size of interconnect wires is gradually reduced to less than 10 nanometers.In order to ensure the service safety and service life of Cu interconnect wires under severe working conditions,it is urgent to develop a high-performance diffusion barrier layer to prevent the mutual diffusion between copper and silicon.In this paper,the target material of Ta-Ru alloy which is almost insoluble with Cu was prepared by vacuum hot pressing sintering method.Ta-Ru-N barrier layer was prepared on Si substrate by reactive magnetron sputtering.The phase structure,surface morphology,thickness and square resistance of the barrier layer were characterized.The thermal stability of Cu/Ta-Ru/Ta-Ru-N films and the performance of the barrier layer were analyzed.The main work is as follows:1.Ta-Ru targets of different composition ratios were prepared by hot pressing sintering process of powder metallurgy under the conditions of 1700?,20 MPa and40MPa.The results showed that with the increase of Ru content,intermetallic compounds such as TaRu,Ta₃Ru and TaRu₄appeared successively in the alloy.Increasing the sintering pressure can promote the reaction between TaRu and increase the relative density of the target.2.With the increase of Ru content,the tensile strength of the target gradually increased,while the microhardness first increased and then decreased.The reason is that the increase in density of Ru content reduced the porosity and thus increased the yield strength of the alloy.The fracture mode of Ta-Ru alloy was mainly cleavage fracture and gradually changed to intergranular fracture and ductile fracture.3.Ta-Ru-N films were prepared by reactive magnetron sputtering.When the partial pressure of nitrogen is 2:7,the film surface is the most flat and the surface quality is better.The square resistance of Ta-Ru-N film gradually increases with the increase of nitrogen flow,and the film gradually transitions to the near-insulation state.4.The barrier layer failed after the Cu/Ta-Ru-10N/Si system was anneal above700?for 30 min,and compounds such as Cu₃Si,Ta₂O₅,Ta Si₂and Ru _XSi began to appear in the Cu film,which led to bulge on the Cu film surface and significantly increased roughness.The square resistance of Cu/Ta-Ru-10N/Si system decreases first and then increases sharply with the increase of annealing temperature.Cu/Ta-Ru-10N/Si films began to fail at the temperature of 700?,indicating that Ta-Ru-10N barrier layer has good diffusion barrier performance.5.Cu/Ta-Ru/Ta-Ru-10N/Si,Cu/Ta/Ta-Ru-10N/Si and Cu/Ta-Ru/Ta-10N/Si of stack structure were deposited by reactive magnetron sputtering.The results show that Cu grows preferentially along Cu(111)orientation after annealing.Cu/Ta-Ru/Ta-Ru-10N/Si can maintain good stability under 750?,film thickness of about 34.04 nm the square resistance is low,about 0.15?/?,showed that Ta-Ru/Ta-Ru-10N stack structure diffusion barrier layer has excellent blocking performance,can effectively improve the thermal stability of Cu thin film.The Cu/Ta/Ta-Ru-10N/Si can maintain good stability under 700?,film thickness of about 30.26 nm the square resistance is lower about 0.23?/?.The Cu/Ta-Ru/Ta-10N/Si thin film under 750?can keep good thermal stability,film thickness of about 38.4 nm square resistance at 0.12?/?.The three diffusion barriers prepared in this paper can effectively prevent Cu atoms from diffusing to Si base,and can effectively improve the thermal stability of Cu films.While Cu/Ta-Ru/Ta-10N/Si has good thermal stability,it also has the lowest square resistance,which seriously affects the stability and reliability of integrated circuits.Therefore,Ta-Ru/Ta-10N is the optimal diffusion barrier layer.