Study Of IBAD Fabrication Technology Of Ta-base Diffusion Barrierfor Cu Interconnection

With the continuous development of interconnection process in integrated circuits,Cu has replaced Al and its alloys as metal interconnect materials.In order to improve the adhesion between Cu and Si-based materials and prevent the diffusion of Cu and Si,it is necessary to deposit a diffusion barrier between Cu and Si-based dielectric materials.In this paper,Ta,Ta N and Ta-Si-N films were prepared by ion beam assisted deposition(IBAD).The effect of Si content on the microstructure,electrical property and diffusion barrier property of Ta-Si-N thin film were investigated.The effect of ion/atom arrival ratio and deposition temperature on the microstructure,electrical property and diffusion barrier property of Ta N film were separately investigated.The results are as follows:(1)With the increase of Si content,the grain size of Ta N decreases gradually,the sheet resistance increases gradually.The microstructure of Ta N film after doping Si is changed from dense columnar crystals to loose equiaxed crystals.The sheet resistance of Cu/Ta N/Si system with undoped Si decreases after annealing.XRD do not find the formation of new phase.Whereas Ta Si2 and Cu3 Si phase whose resistance is very high are formed in Cu/Ta-Si-N/Si system after annealing,which cause the sheet resistance of the systemsignificantly increases.It indicates that the diffusion barrier property of Ta N filmis better than those of Ta-Si-N film.(2)When ion/atom arrivalis 4.6,Ta N(111)plane show a preferred orientation.With the increase of ion/atom arrival ratio,the degree of grain distribution in the Ta N film is gradually increased.The microstructure of Ta N filmis changed from dense columnar crystals to loose equiaxed crystals and the sheet resistance increases gradually.Ta Si2 and Cu3 Si phaseare formed in Cu/Ta/Si system after annealing.The sheet resistance dramaticlly increases.The Cu/Ta N/Si system prepared under the ion/atom arrival ratio of 18.3 has Cu3 Si phase and Ta Si2 phase after annealing for 4 h.The sheet resistancealso increasesdramaticlly.However,when ion/atom arrival ratio is in the range of 4.6 to 13.7,the sheet resistance of the prepared Cu/Ta N/Si system decreasessomewhat after annealing.XRD analysis shows thatthere is no new phase formation.The Ta N filmprepared at the appropriate ion/atom arrival ratio can effectively block the diffusion and reaction of Cu and Si.(3)The Ta N(111)crystal plane exhibits significant preferred orientation at room temperature.With the increase of deposition temperature,the degree of grain distribution in the Ta N film is gradually increased and the microstructure of the filmis changed from dense columnar crystals to loose equiaxed crystals.The deposition temperature has little effect on the sheet resistance of Ta N film.The Ta N film has the best diffusion barrier property at room temperature when the sheet resistance of Cu/Ta N/Si system decreasessomewhat after annealing.XRD results show that there is no Cu3 Si phase formation.The Cu/Ta N/Si system prepared after the deposition temperature is increased has Cu3 Si phase and Ta Si2 phase formation after annealing,which cause the sheet resistancedramaticlly increases.