Measuring device for measuring film thickness of silicon wafer

A measuring device for measuring a film thickness of a silicon wafer, comprising:

• position and velocity sensors linearly arranged into a first position and velocity sensor array of position and velocity sensors in a linear array and a second position and velocity sensor array of position and velocity sensors in another linear array parallel to the linear array of the first position and velocity sensor array, both being parallel to and along a longitudinal direction, in which the first and second position and velocity sensor arrays are within a common plane and are spaced apart from each other in a lateral direction perpendicular to the longitudinal direction, the position and velocity sensors in the first position and velocity sensor array are in one-to-one correspondence with the position and velocity sensors in the second position and velocity sensor array in the lateral direction;
• an eddy current sensor disposed in a symmetrical plane perpendicular to the lateral direction and positioned at a middle position between the first position and velocity sensor array and the second position and velocity sensor array;
• a controller coupled to the position and velocity sensors and the eddy current sensor respectively for controlling measurement of the film thickness according to detection signals from the position and velocity sensors and the eddy current sensor that are obtained when the silicon wafer is translated along the longitudinal direction while being rotated,
• wherein the controller and the first and second position and velocity sensor arrays collectively detect a rotation velocity of the silicon wafer based on a time delay in sensing a notch on the silicon wafer by (1) a first position and velocity sensor in the first position and velocity sensor array and (2) a second position and velocity sensor in the second position and velocity sensor array that corresponds the first position and velocity sensor at the same longitudinal position, and
• wherein the controller and the first and second position and velocity sensor arrays collectively detect a translation velocity of the silicon wafer along the longitudinal direction based on a time delay in sensing the silicon wafer by two adjacent position and velocity sensors along in the longitudinal direction in either the first or second position and velocity sensor array.