Study On The Stability Of Copper Slurry With Low Pressure And Low Abrasive Concentration For GLSI

With the development of Gita-large scale integrated circuits?GLSI?,the feature size drops down to 14 nm and even smaller,and the manufacturing process becomes more and more complex.Chemical mechanical polishing?CMP?,as one of critical manufacturing procedures of GLSI,is the most effective method to realize copper local and global planarization.Slurry is the critical factor to determine the quality of CMP,and its stability is the premise and foundation of excellent polishing performance,especially in low pressure and low abrasive weakly alkaline condition.In this paper,based on the status that few researches about stability of GLSI copper slurry were done at home and abroad and after adding hydrogen peroxide and storage for a long time it was easy to cause some problems for slurry such as gelation and delamination,the theoretical analysis and experimental researches were carried out.A new kind of relatively stable copper slurry which was applicable to the production requirements was gained,and specific results were shown as following:1.Under the condition of low pressure and low abrasive concentration,according to the stability theory of colloidal silica and DLVO theory the influence of different kinds of surfactants and pH-regulators on the stability of colloidal silica was studied from the aspect of molecular structure and ionization method.It was concluded that taking anionic surfactant of ammonium dodecyl sulfate instead of nonionic surfactant of traditional fatty alcohol-polyoxyethylene ether as surfactant,organic alkali tetraethylammonium hydroxide instead of KOH as pH regulator can solve the problems mentioned above at pH 9.0.Meanwhile,the optimal components of copper slurry was obtained.When the concentrations of silica as abrasive,glycine as complexing agent,BTA as inhibitor and H₂O₂ as oxidizing agent?30 wt%?were 1 wt%,2.5 wt%,0.02wt%and 0.6wt%,this new type slurry can be stable for at least seven days after adding hydrogen peroxide.2.3 inch copper blanket wafer and copper pattern wafer were polished by using self-developed copper slurry.The results indicated that after settling for 0 day and7 days respectively,pH,average particle size,Zeta potential,viscosity,within wafer non-uniformity?WIWNU?,copper removal rate,surface roughness and step height basically kept invariable.It indicated that the polishing performance stability of weakly alkaline copper slurry within 7 days was acceptable.It meets the industrial requirements of stability that the slurry can be stable at least for 6 hours after adding hydrogen peroxide and has a guiding significance to industrial production.