Silica Nano-particle Anneal Treatment and Its Effect on Chemical Mechanical Polishing

Introduction Chemical mechanical polishing is the only one technology to obtain global planarization, which is widely applied to polish silicon, copper dual damascene structure, high/low K dielectric materials, tungsten plugs, poly-silicon gates and shallow trench isolation structure. SiO2 is widely used as abrasive for its superior properties like stability, suspension property and low viscosity There are lots of studies on silica properties. However, the detailed silica surface, inner characteristic and its effect on polishing performance are still unclear. we must also explore the silica nano-particle tiny structure difference, so we designed an experiment that we anneal the colloid silica and re-dispersed it to analyze the variety of particles properties and its influences on CMP performance. Materials The water glass was purchased from the market. KOH (90%) and H2SO4 (98%) were purchased commercially from Shanghai Aladdin Bio-Chem technology Co., Ltd. All reagents were of analytical grade and used without further purification. Method Diluted KOH or H2SO4 were added to 1 wt% annealed silica slurry to adjust pH value to 11.0. The slurry was milled in the polishing process. Arsenic doped 4 inch (100) silicon wafer was used to polish. The structural and morphological evolution of silica nano-particles induced by heat treatment are studied by scanning electron microscopy (SEM), X-Ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), differential thermal (DTA) and thermal gravimetric analysis (TGA), which disclose the external and internal structure.