Study On CMP Slurry Prescription Of SiO₂ ILD

With the fast developing of the integrated circuit (IC) industry, the dimension of silicon wafer trends to be lager and the IC feature size becomes smaller and smaller. At the same time, the IC process becomes more complex and sophisticate. That means the surface precision of the inter-level dielectric (ILD) must be improved. For this reason, the surface planarization of ILD should be complete. But the traditional polishing technics cannot meet the request. The chemical mechanical polishing (CMP) technic is now publicly considered the best and most effective planarization technic. The CMP slurry has both the chemical erosion effects and the mechanical grinding effects on the surface being processed. But for the complexity of the CMP technic, the CMP mechanism and the function of the CMP slurry is still unknown and is asking for further research. Besides, there are still some problems that restrict the improvement of the CMP technic, such as: metal ions contamination, low dispersal quality and low material removal rate, etc.In this paper, the subject of CMP slurry prescription for SiO₂ ILD is studied. For reducing metal ions content, improving material removal rate and dispersal, the choice of slurry prescription and optimization is studied through many of theories and experiments. Meanwhile, the material removal principle and acquired productions of slurry has also been discussed. At last, the ingredient and prescription of slurry is found, and the slurry is made with well properties.Firstly, the CMP mechanism has been studied in this paper. The factors that influence the CMP quality most have been found. At the same time, the projects of selecting ingredients and optimizing prescription have been established. Secondly, the function of main ingredients of slurry has been analyzed. The single factor experiments of every ingredients of slurry have been carried out on the UNIPOL1502 lapping/polishing machine. Meanwhile, the inorganic alkali, the organic alkali, the nanometer abrasive, the surfactant and the additive have been selected, which is fit CMP of SiO₂ ILD. Basing on these selected ingredients other experiments has been carried out to improve the prescription and to find the appropriate pH value. A kind of high quality slurry has been developed through the studying of the mechanism of which the quantity of various slurry ingredients and the pH value affect the polishing effect.The paper provides a kind of systemic researching methods and a group of useful experimental statistics for improving the polishing quality of the slurry, increasing thematerial removal rate and optimizing the slurry capability. It has significant values in the reform of ELD planarization technique for ultra large-scale integration (ULSI).