Study On Galvanic Corrosion Control Of Aluminum-cobalt CMP In GLSI Prtceding Process

With the development of integrated circuit manufacturing technology according to Moore's law,the feature size is reduced 7 nm and below,and the ultra-precision processing technology of the large scale integrated circuit gate becomes more and more complex.Chemical mechanical polishing is one of the most effective methods to realize global and local planarization of aluminum/cobalt gate materials.In the polishing process,galvanic corrosion occurs between aluminum and cobalt due to the formation of galvanic cell structure due to the presence of slurry.The strength of galvanic corrosion directly determines the processing efficiency and quality of the entire gate.In this paper,a systematic theoretical and experimental study has been carried out on the problem that the galvanic corrosion strength of aluminum-cobalt gate CMP is difficult to control.The research results have important guiding significance for the subsequent research and development of gate slurry.The main results are as follows:1.Using the difference of inhibition efficiency to control aluminum-cobalt galvanic corrosion.By studying the effects of cystine,benzotriazole(BTA)and hydroxyethylcellulose on galvanic corrosion of aluminum and cobalt,it is found that cystine can react with aluminum and cobalt ions to form adsorptive complexes covering the surfaces of aluminum and cobalt.All three reagents can cause corrosion inhibition of aluminum and cobalt.However,due to the different adsorption efficiencies of aluminum and cobalt,the inhibition efficiency is different.The anode aluminum with low corrosion voltage is strongly inhibited while the cathode cobalt with high corrosion voltage is slowly inhibited.The research found that when the concentration of cystine is 1500 ppm,the dynamic and static galvanic corrosion voltages between aluminum and cobalt are reduced to 23 m V and 30 m V respectively,and the current is reduced to 2.936?Acm^-2and 0.835?Acm^-2respectively,which shows good inhibition effect.Galvanic corrosion of Al-Co was effectively controlled by different inhibition efficiency.2.Using selective adsorption to control aluminum-cobalt galvanic corrosion.By studying the effects of glycine,(2,2'-[(methyl-1H-benzotriazole-1-yl)methyl]imino]diethanol(TT-LYK)and ascorbic acid on galvanic corrosion of aluminum and cobalt,it is found that the complexes formed by the complexation reaction between glycine and aluminum and cobalt ions will be adsorbed on the surface of aluminum but not on the surface of cobalt,resulting in inhibition of aluminum corrosion and promotion of cobalt corrosion.All three reagents can adsorb aluminum or cobalt,but due to different selective adsorption of aluminum and cobalt,only one of them is inhibited or the other is promoted,and anode aluminum with low corrosion voltage is inhibited while cathode cobalt with high corrosion voltage is promoted.It was found that when glycine with a concentration of 1000 ppm was added,the dynamic and static galvanic corrosion voltages between aluminum and cobalt were reduced to 53 m V and 50 m V respectively,and the current was reduced to 3.703?Acm^-2and 7.733?Acm^-2respectively,with good inhibition effect.Galvanic corrosion of Al-Co was effectively controlled by selective adsorption.3.Controlling galvanic corrosion of aluminum-cobalt gate by using optimized slurry.By optimizing the ratio of glycine and TT-LYK;and the ratio of ascorbic acid and BTA the galvanic corrosion of aluminum-cobalt alloy was controlled effectively.It was found that the mixing of glycine and TT-LYK reduced the dynamic and static galvanic corrosion voltage between aluminum and cobalt to 10 m V and 17 m V respectively,and the galvanic corrosion current to 0.587?Acm^-2and 2.361?Acm^-2respectively,which had better effect and could meet the requirements of industrial production.