Method and a system for evaluating the physical consumption of a polishing pad of a cmp apparatus, and cmp apparatus

Abstract

A method for evaluating the physical consumption of a polishing pad of a CMP apparatus provided with an eddy current sensor that is configured to sense a distance with a substrate on which a layer to be processed extends. The method includes: generating a magnetic field adapted to induce eddy currents in the layer; acquiring an eddy current signal generated by the layer in response to the magnetic field; calculating an average value of the eddy current signal in the initial time frame; comparing the average value with a pre-set threshold value; and determining a maintenance condition of the polishing pad based on a result of the comparison.

1 . A method for evaluating physical consumption of a polishing pad of a Chemical Mechanical Polishing (CMP) apparatus, where the CMP apparatus is provided with an eddy current sensor that is configured to sense a distance using a substrate on which a layer to be processed by the CMP apparatus extends, the method comprising:
 generating, using the eddy current sensor, a magnetic field configured to induce eddy currents in the layer during an initial time frame of CMP processing of the layer;   acquiring, using the eddy current sensor during the initial time frame, an eddy current signal generated by the layer in response to the magnetic field;   calculating an average value of the eddy current signal in the initial time frame;   comparing the average value with a pre-set threshold value; and   determining a maintenance condition of the polishing pad based on a result of the comparison.   
     
     
         2 . The method of  claim 1 , wherein the maintenance condition is a desire for replacement of the polishing pad. 
     
     
         3 . The method of  claim 1 , wherein the initial time frame is such that the eddy current signal generated by the layer during the initial time frame is saturated. 
     
     
         4 . The method of  claim 1 , wherein the initial time frame is such that the eddy current signal generated by the layer during the initial time frame is saturated and substantially time-invariant. 
     
     
         5 . The method of  claim 1 , wherein the initial time frame is such that the eddy current signal generated by the layer during the initial time frame is substantially time-invariant. 
     
     
         6 . The method of  claim 1 , wherein the initial time frame is between 0 and 70 seconds of the CMP processing of the layer. 
     
     
         7 . The method of  claim 1 , wherein the initial time frame is between 0 and 20 seconds of the CMP processing of the layer. 
     
     
         8 . The method of  claim 1 , wherein the eddy current sensor is arranged with respect to the polishing pad in such a way that the eddy current signal is a function of both a thickness of the layer and a thickness of the polishing pad. 
     
     
         9 . The method of  claim 8 , wherein the eddy current sensor is supported by, and moves with, a supporting platen over which the polishing pad is coupled. 
     
     
         10 . The method of  claim 1 , further comprising arranging the layer against the polishing pad before the initial time frame of processing of the layer by the CMP apparatus. 
     
     
         11 . A system for evaluating physical consumption of a polishing pad of a Chemical Mechanical Polishing (CMP) apparatus, the system comprising:
 an eddy current sensor configured to sense a distance using a substrate on which a layer to be processed by the CMP apparatus extends, wherein the eddy current sensor is configured to generate, during an initial time frame of CMP processing of the layer, a magnetic field configured to induce eddy currents in the layer and to acquire, during the initial time frame, an eddy current signal generated by the layer in response to the magnetic field; and   processing circuitry coupled to the eddy current sensor and configured to:
 calculate an average value of the eddy current signal in the initial time frame, 
 compare the average value with a pre-set threshold value, and 
 determine a maintenance condition of the polishing pad based on a result of the comparison. 
   
     
     
         12 . The system of  claim 11 , wherein the maintenance condition is a replacement of the polishing pad. 
     
     
         13 . The system of  claim 11 , wherein the initial time frame is such that the eddy current signal generated by the layer during the initial time frame is one of saturated and/or substantially time-invariant. 
     
     
         14 . The system of  claim 11 , wherein the initial time frame is between 0 and 70 seconds of said CMP processing of the layer. 
     
     
         15 . The system of  claim 11 , wherein the initial time frame is between 0 and 20 seconds of said CMP processing of the layer. 
     
     
         16 . The system of  claim 11 , wherein the eddy current sensor is arranged with respect to the polishing pad in such a way that the eddy current signal is a function of a thickness of the layer plus a thickness of the polishing pad. 
     
     
         17 . The system of  claim 11 , wherein the eddy current sensor is supported by, and moves with, a supporting plate over which the polishing pad is coupled. 
     
     
         18 . A CMP apparatus comprising a system according to  claim 11 . 
     
     
         19 . A chemical machine polishing (CMP) apparatus, comprising:
 a wafer carrier facing a polishing pad, the polishing pad being disposed over a supporting plate;   a wafer carried by the wafer carrier, the wafer having a top surface over which a conductive layer extends; and   an eddy current sensing device configured to induce an eddy current field in the conductive layer, and detect a change in impedance of a coil of the eddy current sensing device;   wherein the eddy current sensing device is further configured to generate, from the change in impedance, an output signal based upon a thickness of the conductive layer and a distance between the eddy current sensing device and the conductive layer, the output signal corresponding to a thickness of the polishing pad.   
     
     
         20 . The CMP apparatus of  claim 19 , wherein the eddy current sensing device is supported by, and moves with, the supporting plate. 
     
     
         21 . The CMP apparatus of  claim 19 , wherein the eddy current sensing device induces the eddy current field in the conductive layer by an alternating current flowing through the coil. 
     
     
         22 . The CMP apparatus of  claim 19 , wherein the change in the impedance indicates that a thickness of the polishing pad has reduced below a threshold level.