Patent ID: 8083571

Claim:
A polishing apparatus comprising: a polishing surface; a top ring for holding a substrate; a vertical movement mechanism operable to move said top ring in a vertical direction; a position detector operable to detect a position of said top ring when a lower surface of said top ring or a lower surface of the substrate held by said top ring is brought into contact with said polishing surface; and a controller operable to calculate an optimal position of said top ring to polish the substrate based on the position detected by said position detector, wherein said vertical movement mechanism includes: a ball screw for moving said top ring in the vertical direction; and a servomotor for operating said ball screw, wherein said vertical movement mechanism is operable to move said top ring to the optimal position calculated by said controller, and wherein said controller controls said servomotor such that a maximum current of said servomotor is set such that a torque of said servomotor when the lower surface of said top ring or the lower surface of the substrate held by said top ring is brought into contact with said polishing surface is smaller than a torque of said servomotor during polishing after said top ring has been moved to the optimal position.