Patent ID: 7137870

Claim:
A wafer polishing and broken platen belt sensing apparatus comprising: a polishing platen adapted to rotate a polishing pad; a motor adapted to rotate the polishing platen; a first drive pulley disposed around a driving axis of the motor; a second drive pulley disposed below the polishing platen and around a rotational axis of the polishing platen; a platen belt connecting the first drive pulley and the second drive pulley; an encoder connected to the motor and adapted to output a first square wave signal in accordance with rotational speed of the motor; a current generating unit adapted to generate a motor driving current in accordance with the first square wave signal; a photo sensor adapted to output a second square wave signal in accordance with the rotational speed of the polishing platen; and, a controller adapted to receive the motor driving current and the second square wave signal, to determine whether the polishing platen and the motor are rotating normally, and to generate an interlock signal when the polishing platen is not rotating normally.