Patent ID: 7255719

Claim:
A wafer rotating device to rotate a disk-shaped wafer having a top surface, a bottom surface and a circumferential surface, the water rotating device comprising: at least three rollers rotatably provided about axes arranged at parallel intervals and disposed to clamp the wafer, wherein each of the rollers has a cylindrical surface; a rotation drive mechanism arranged to rotate and drive at least one of the rollers, wherein the cylindrical surfaces of the rollers contact only the circumferential surface of the wafer without contacting the top surface and the bottom surface of the wafer when the rotation drive mechanism is activated to rotate the wafer; a load cell disposed to detect a contact load between the cylindrical surfaces of the rollers and the circumferential surface of the wafer; an interval adjustment mechanism operatively connected to the rollers to adjust dimensions of the intervals of the rollers so that only the circumferential surface of the wafer is supported by a frictional force that is proportional to the contact load and so that the wafer is stabily held at a position in a direction of height of at least one of the cylindrical surfaces while balancing gravity and the frictional force; and a load control device that controls the interval adjustment mechanism so that the contact load detected by the load cell is maintained constant.