Study On The Effect Of Alkaline Cleaning Solution On Post Cleaning And Electrical Parameters Of Copper Wiring CMP

Chemical mechanical planarization(CMP)is the only technology that can achieve local and global planarization currently for multi-layer copper wiring in the preparation of giga large scale integrated circuits(GLSI).After CMP process,there will be a large amount of contaminants on the surface of the wafer,and post-CMP cleaning becomes a critical step to determine the reliability of devices.With the technology node reduction to 28 nm or 14 nm,ruthenium(Ru)and cobalt(Co)have become the new barrier materials of copper interconnection due to their better physicochemical properties.In order to reduce the resistance-capacitance(RC)delay,low-k and ultra-low-k dielectric materials are used as insulation medium,and the influence of post-CMP cleaning technology on the electrical parameters arises extensive attentions and researches,such as capacitance of insulating medium,loss of copper and leakage current.At present,the commercial post-CMP cleaning solution is still a citrate-based acidic cleaning solution.However,Ru will produce toxic gases,and copper-cobalt galvanic corrosion is extremely serious under acidic conditions.Therefore,the research on new alkaline cleaning solution with less influence on electrical parameters has become the focus of research and development of cleaning technology.In this paper,the effect of FA/O? chelating agent which is the composition of self-developed alkaline cleaning solution on the k value of Black Diamond(BD)was analyzed by mercury probe,Fourier transform infrared spectroscopy(FTIR)and atomic force microscopy(AFM).Combined with the results of metallographic microscope,the effect of alkaline cleaning solution on the k value of BD and surface contaminant removal were explored.Results showed that the alkaline cleaning solution consisting of of 150 ppm FA/O? chelating agent and 750 ppm FA/O? surfactant can effectively remove CMP residual contaminants from BD surface.After cleaning,the number of Si-CH3 bonds didn't change and the number of Si-O-Si bonds was significantly reduced on the surface of the wafer.The increase of k value was only 3.04%.In this paper,the Ultraviolet visible light photometer and electrochemical workstation were used to investigate the chelation of FA/O? chelating agent and glycine to copper ions.Combined with the results of the semiconductor electrical parameter meter,the FA/O? chelating agent had less corrosive effect on the Cu surface,the removal effect of copper ions on the wafer surface was better,and the leakage current of the wafer was smaller than glycine.The cleaning process is a key factor which affects the cleaning performance.Based on the selected alkaline cleaning solution,the effects of different cleaning parameter on the k value of BD and the removal performance of residual polishing slurry on the surface of BD and Cu wafer are investigated.The results show that there were no residuals of abrasive particles,organic substances on BD and Cu wafer surface with the cleaning process of brush gap of-0.5 mm,brushing time with deionized water for 75 s,brushing time with cleaning solution for 40 s and brush rotation speed of 200 rpm.The surface roughness of BD and Cu were 0.24 nm and 0.35 nm,respectively.The increase of k value was only 2.61%.In addition,in order to further reduce the corrosion of alkaline cleaning solution of Cu wafer surface and reduce the leakage current,1,2-benzisothiazolin-3-one(BIT)was added to the alkaline cleaning solution and the effect of BIT on reducing Cu corrosion was studied.The results showed that the the corrosion current of Cu surface was reduced by 22.39% and the static corrosion rate was reduced by 33.33% with adding 200 ppm BIT.Besides,there were no residues of abrasive particles,organic substances on Cu surface after cleaning.