Abstract: In order to get ultra-smooth glass substrate of digital compact disc (CD), 2 µm and 0.3 µm cerium dioxide slurries as well as 50 nm silica slurry are prepared respectively, and three steps chemical-mechanical polishing (CMP) of sodium-calcium glass substrate in the three slurries has been studied. Results show that during the first step polishing with 2 µm cerium dioxide slurry, a high material removal rate is reached and the average roughness Ra value of the polished surfaces can be decreased from previous 537.9 nm to 1.63 nm. In the second step CMP with 0.3 µm cerium dioxide slurry, the Ra value can be decreased to 0.73 nm. By using 50 nm silica slurry in the final CMP, the Ra value of the glass substrate surfaces can be further reduced to 0.44 nm, which is the lowest value reported to date for CD glass substrate polishing. Atom force microscopy (AFM) analysis shows that the polished surfaces are ultra-smooth without micro-defects. Based on the analyses of the mechanical and chemical effects during the glass substrate CMP, the CMP mechanism is deduced preliminarily.

Key words: Chemical mechanical polishing(CMP), Glass substrate, Slurry, Sub-nanometer scale planarization