Cu Interconnect Dual Damascene Etch Process Development And Optimization Based On Metal Hard Mask Integration Approach

With further reduce of integrated circuits interconnect feature size,,multilayer interconnect technology based on copper and low-K dielectric has becomes the inevitable choice to decrease interconnect RC delay.It has been demonstrated that the dry etch&ashing process of dual damascene technology might impact the mechanical&physicochemical properties of low-K dielectric to some extent,which will induced local increase of K inside integrated circuits,and decrease the superiority of low-K dielectric.The dual damascene dry etch process based on metal hard mask integration approach,which exists great advantages in reducing low-k material damage.However,due to the introduction of the new metal mask TiN,the C/H/O carried by photo resist of the reaction by-product is turned into a more complex by-product system containing Ti elements,which makes the whole dry etch process facing many challenges that are different from the traditional process.In this paper,for the polymer residue defects in metal hard mask dual damascene etch process,the major parameters at dry etch process are optimized by mechanisms research and experiment verification.The results show that increasing the source power,reducing the bias power and increasing the temperature of the wafer substrate can effectively reduce the total polymer concentration and improve the residual polymer residue at the bottom of the via hole.By introducing the C₄F₈ reaction gas in dry etch process,the F/C ratio in the reaction system is reduced which improve the he roughness defects at the bottom of the trench.Then the etching solution with larger process window was developed.For the fluotitanate condense defects happened after metal hard mask dual damascene etch process,the N₂ PST process after dry etch is proposed based on the defects distribution and potential formation mechanism.The experiment results show that the introduction of N₂ PST process can effectively control the fluorin degas concentration inside foup,and prevent the formation of the fluotitanate condense defect.For the copper corrosion failure happened during post dual damascene all in one etch wet clean process,the failure model is defined as photo-assistant electrochemical copper corrosion based on experiment result.Then the solution to prevent copper corrosion fail by strictly control the light condition during wet cleaning process of copper interconnect is proposed.In this paper,based on the research of the above main technical problems,the metal hard mask dual damascene all in one etch process and following wet cleaning process is developed and optimized,so that it can meet the mass production requirements on the process window and process stability.It is of great significance to understand the potential influence law and mechanism of each step in etching process,and further promote the development and application of the metal hard mask all in one etch process.