Investigation On Interface Corrosion Of Barrier Layer Ru Chemical Mechanical Polishing For GLSI Multilayer Copper Interconnection

In the very large-scale integrated circuit(GLSI)stage,billions of components can be integrated on each chip.With the technology node reaching 14 nm or less,traditional barriers can no longer meet the needs of technological development.Due to its lower resistivity and good adhesion,the ruthenium(Ru)metal material can be directly electroplated with copper,effectively reduces the thickness of the barrier layer and has a higher barrier performance,so it can replace the traditional tantalum(Ta)as an excellent material for the new generation of copper interconnect diffusion barriers.Chemical mechanical polishing(CMP)is the key technology to achieve planarization of Ru-based barrier layers.In the CMP process,due to the large contact potential difference between Ru and Cu,when they contact with the slurry will cause serious galvanic corrosion,leading to interface corrosion between Cu and Ru,seriously affecting the reliability of the device.Therefore,in this paper,the theoretical and material in-depth study of the Cu/Ru interface corrosion(Ru corrosion,Cu/Ru galvanic corrosion)in Ru-based barrier CMP process is carried out.The main contents are as follows:In this paper,a weakly alkaline route based on chemical action was used.Through electrochemical experiments,the corrosion mechanism of Cu and Ru and the corrosion inhibition mechanism of Cu/Ru couple were revealed by pH,oxidant,chelating agent,active agent,and corrosion inhibitor.The results show that the pH value has a great influence on the corrosion of Cu and Ru films.The galvanic corrosion between Cu and Ru can be effectively controlled under weak alkaline conditons with a pH of 9.The pH value of the solution in the experiment is selected to be 9.Using the oxidation passivation of potassium periodate,selects the optimal concentration of 0.015mol/L to reduce the corrosion potential difference between Ru and Cu.On this basis,using the strong chelating effect of FA/O chelators,which can chelate metal ions,dissolve the passive film,and effectively reduce the corrosion potential difference between Ru and Cu.At the same time,based on the preferential adsorption mechanism,the self-developed FA/O I type nonionic surfactant was selected to obtain a good surface morphology on Cu and Ru.Finally,Ru and Cu corrosion inhibitors were studied separately,and non-toxic and tasteless ascorbic acid and 1,2,4-triazole were selected to avoid the post-CMP cleaning problem caused by BTA.The optimized alkaline barrier polishing solution was: 0.015mol/L potassium periodate,1.5ml/L FA/O II type chelating agent,5ml/L FA/O I type nonionic surface,5mM ascorbic acid,1000 ppm 1,2,4-triazole.The corrosion potential difference between Cu/Ru was reduced to 16 mV,which can effectively suppress the severe galvanic corrosion between Cu and Ru.The interface corrosion problem was solved,and the removal rates of Ru and Cu are 284?/min and 259?/min,respectively.The selection ratio was greater than 1,which is beneficial to the correction of dishing and erosion,laying a theoretical foundation for the new technology of Ru CMP.