Method and Apparatus for Determining a Measure of a Thickness of a Polishing Pad of a Polishing Machine

Abstract

An apparatus for determining a measure of a thickness of a polishing pad of a polishing machine includes a detector and a determiner. The detector is configured to detect a position of a carrier of an element to be polished in a pressing direction while the element is pressed by the carrier in the pressing direction against the polishing pad with a defined pressure. The detector is further configured to output a signal indicative of the position of the carrier. The determiner is configured to determine the measure of the thickness of the polishing pad based on the signal indicative of the position of the carrier.

1 . An apparatus for determining a measure of a thickness of a polishing pad of a polishing machine, the apparatus comprising:
 a detector configured to detect a position of a carrier of an element to be polished in a pressing direction while the element is pressed by the carrier in the pressing direction against the polishing pad with a defined pressure and to output a signal indicative of the position of the carrier; and   a determiner configured to determine the measure of the thickness of the polishing pad based on the signal indicative of the position of the carrier.   
     
     
         2 . The apparatus of  claim 1 , wherein the determiner is configured to determine the measure of the thickness of the polishing pad by comparing the signal indicative of the position of the carrier to calibration data obtained in advance using the polishing pad of a known thickness, a predetermined pressure and a predetermined thickness of the element. 
     
     
         3 . The apparatus of  claim 2 , wherein the detector is configured to detect the position of the carrier while conditions in terms of at least one of the defined pressure, the carrier used and the element to be polished correspond to conditions during obtaining the calibration data. 
     
     
         4 . The apparatus of  claim 2 , wherein the determiner is configured to determine the measure of the thickness taking into consideration at least one of a first correction factor that depends on a difference between the defined pressure and the predetermined pressure, a second correction factor that depends on a difference between an actual thickness of an element to be polished and the predetermined thickness and a third correction factor that depends on a number and/or a position of elements pressed to the polishing pad by respective carriers in parallel. 
     
     
         5 . The apparatus of  claim 1 , wherein the detector is configured to detect the position of the carrier at a predetermined time after starting a process of polishing the element. 
     
     
         6 . The apparatus of  claim 1 , wherein the detector is configured to output a plurality of signals indicative of the position of the carrier consecutively in time, and wherein the determiner is configured to determine the measure of the thickness based on an average of the plurality of signals. 
     
     
         7 . The apparatus of  claim 1 , wherein the determiner is configured to output an alarm-signal if the determined thickness of the polishing pad falls below a threshold value. 
     
     
         8 . The apparatus of  claim 1 , wherein the detector comprises:
 a fixed signal source configured to emit an electromagnetic wave;   a reflector associated with the carrier such that the position of the carrier is coupled with a position of the reflector; and   a fixed sensor configured to obtain an angle of incidence of the electromagnetic wave reflected by the reflector;   wherein the obtained angle of incidence depends on the position of the reflector.   
     
     
         9 . The apparatus of  claim 8 , wherein the signal source is a laser. 
     
     
         10 . The apparatus of  claim 8 , wherein the reflector reflects the electromagnetic wave diffusely; and
 wherein the sensor comprises a lens and an electronic light sensor and wherein the sensor is configured to obtain the angle of incidence of the reflected electromagnetic wave by obtaining a maximum intensity of the reflected electromagnetic wave, the maximum intensity is projected to the electronic light sensor by the lens.   
     
     
         11 . The apparatus of  claim 1 , wherein the detector comprises:
 a fixed signal source configured to emit an electromagnetic wave;   a reflector associated with the carrier such that the position of the carrier is coupled with a position of the reflector; and   a fixed sensor configured to obtain a travel time of the electromagnetic wave reflected by the reflector;   wherein the obtained travel time depends on the position of the reflector.   
     
     
         12 . The apparatus of  claim 1 , wherein the detector comprises an electrical position sensor. 
     
     
         13 . An apparatus for determining a measure of a thickness of a polishing pad of a polishing machine, the apparatus comprising:
 a detector configured to detect a position of a carrier of an element to be polished in a pressing direction while the element is pressed by the carrier in the pressing direction against the polishing pad with a defined pressure, wherein the detector is configured to output a signal indicative of the position of the carrier; and   a determiner configured to determine the measure of the thickness of the polishing pad based on the signal indicative of the position of the carrier and on the basis of calibration data obtained in advance using the polishing pad of a known thickness, a predetermined pressure and a predetermined thickness of the element, wherein the determiner is configured to output an alarm-signal if the determined thickness of the polishing pad falls below a threshold value.   
     
     
         14 . The apparatus of  claim 13 , wherein the determiner is configured to determine the measure of the thickness of the polishing pad when the defined pressure is equal the predetermined pressure and/or the defined thickness of the element is equal predetermined thickness of the element. 
     
     
         15 . A polishing machine for polishing an element, the polishing machine comprising:
 a platen on which a polishing pad is to be fixed;   a carrier of the element to be polished, wherein the carrier is configured to move in a pressing direction so as to press the element in the pressing direction against the polishing pad with a defined pressure, wherein the polishing machine is configured to cause a relative movement or rotation between the element and the polishing pad in parallel with the polishing pad;   a detector configured to detect a position of the carrier while the element is pressed by the carrier in the pressing direction against the polishing pad with the defined pressure and to output a signal indicative of the position of the carrier; and   a determiner configured to determine a measure of the thickness of the polishing pad based on the signal indicative of the position of the carrier.   
     
     
         16 . The polishing machine of  claim 15 , wherein the carrier of the polishing machine is configured to press a plurality of elements against the polishing pad; or
 wherein the polishing machine comprises a plurality of carriers each configured to press an element to be polished against the polishing pad.   
     
     
         17 . The polishing machine of  claim 15 , further comprising a pressure sensor configured to determine the defined pressure. 
     
     
         18 . The polishing machine of  claim 15 , further comprising a controller configured to control the polishing machine and to provide at least one of a value of the defined pressure, a thickness of the element to be polished and a number and/or a position of elements pressed to the polishing pad by respective carriers in parallel; and
 wherein the determiner is configured to determine the measure of thickness of the polishing pad taking the at least one value in consideration.   
     
     
         19 . The polishing machine of  claim 15 , wherein the detector is an electrical or optical position sensor. 
     
     
         20 . The polishing machine of  claim 15 , further comprising one or more down force cylinders for pressing the one or more carrier against the polishing pad, wherein the detector is configured to detect a position of the down force cylinder. 
     
     
         21 . The polishing machine of  claim 15 , further comprising the polishing pad fixed on the platen. 
     
     
         22 . A method for determining a measure of a thickness of a polishing pad of a polishing machine, the method comprising:
 detecting a position of a carrier of an element to be polished in a pressing direction while the element is pressed by the carrier in the pressing direction against the polishing pad with a defined pressure;   outputting a signal indicative of the position of the carrier; and   determining the measure of the thickness of the polishing pad based on the signal indicative of the position of the carrier.   
     
     
         23 . The method of  claim 22 , further comprising obtaining calibration data in advance of using a polishing pad of known thickness and a thickness of the element; and
 wherein detecting the position of the carrier is performed while conditions in terms of at least one of the defined pressure, the carrier used and the element to be polished correspond to corresponding conditions during obtaining the calibration data.   
     
     
         24 . The method of  claim 22 , further comprising:
 obtaining calibration data in advance using a polishing pad of known thickness, a predetermined pressure and a predetermined thickness of the element; and   correcting the signal indicative of the position based on at least one of a first correction factor that depends on a difference between the defined pressure and the predetermined pressure, a second correction factor that depends on a difference between an actual thickness of an element to be polished and the predetermined thickness and a third correction factor that depends on a number and/or a position of elements pressed to the polishing pad by respective carriers in parallel.   
     
     
         25 . The method of  claim 22 , wherein detecting the position of the carrier is performed at a predetermined time after starting a process of polishing the element. 
     
     
         26 . A non-transitory computer readable medium comprising instructions, which, when executed by a processor of an apparatus for determining a measure of a thickness of a polishing pad, causes the apparatus to perform a method comprising:
 detecting a position of a carrier of an element to be polished in a pressing direction while the element is pressed by the carrier in the pressing direction against the polishing pad with a defined pressure;   outputting a signal indicative of the position of the carrier; and   determining the measure of the thickness of the polishing pad based on the signal indicative of the position of the carrier.