In recent years, CMP (chemical mechanical polishing), which is performed by relatively rotating a silicon wafer and a polishing cloth while supplying a polishing liquid containing abrasive grains (e.g., silica particles) in an alkaline aqueous solution, is generally used as a method of a polishing a surface of a silicon wafer. The CMP is a composite technique of a mechanical polishing action by the abrasive grains and a chemical polishing action by the alkaline aqueous solution. It is well known that a high flatness of the surface of the silicon wafer is obtained by compositing the above two polishing actions. The CMP of the silicon wafer is typically performed by a plurality of steps from a double-side polishing step to a one-side polishing step.
The double-side polishing step is performed in order to polish the silicon wafer to a desired thickness. Specifically, a front side and a rear side of the silicon wafer are simultaneously polished with a hard polishing cloth made of polyurethane and the like at a relatively high polishing speed. This double-side polishing flattens the silicon wafer so as to decrease a fluctuation in a thickness of the polished silicon wafer and removes waviness components (e.g., nanotopography).
The one-side polishing step is performed in order to improve roughness of one of surfaces of the silicon wafer after being subjected to the double-side polishing. Specifically, the one-side polishing step is performed with a soft polishing cloth such as a suede cloth in combination with micro abrasive grains so as to reduce micro roughness of the one of surfaces of the silicon wafer (e.g., nanotopography and haze). The one-side polishing step is performed at a plurality of stages with a variation of a type of the polishing cloth, a size of the abrasive grains and an alkali concentration in the polishing liquid.
As a technique relating to the one-side polishing step in order to improve a haze of a surface of the silicon wafer, there have been disclosed: an abrasive agent used for a mirror-finish polishing of the silicon wafer, the abrasive agent containing alkaline silica, a water-soluble polymer, and a cyclic organic compound; and a method of polishing the silicon wafer using the abrasive agent (see Patent Literature 1).