Polishing method and apparatus, and device fabrication method

Abstract

The present invention concerns a polishing method of keeping a polishing pad under a predetermined pressure and in contact with a polished surface of a wafer and performing polishing while rotating the wafer and the polishing pad, in which symmetry of a film on an alignment mark for alignment of the wafer is measured after an end of the polishing of the wafer or in the middle of the polishing and in which polishing thereafter is carried out by controlling rotation speeds of the wafer and polishing pad according to the symmetry of the film on the alignment mark, thus measured, whereby the film on the alignment mark of the wafer can be isotropically polished in symmetry.

What is claimed is:  
     
         1 . A polishing method comprising the steps of keeping a polishing pad under a predetermined pressure and in a state of contact with a device forming surface of a substrate and performing polishing while rotating each of said substrate and said polishing pad, 
 wherein symmetry of a film on an alignment mark for alignment of said substrate is measured after an end of the polishing of said substrate or in the middle of the polishing and wherein a rotation speed of at least either one of said substrate and said polishing pad is controlled according to the symmetry of the film on the alignment mark, thus measured.    
     
     
         2 . The polishing method according to  claim 1 , wherein control is implemented so as to change rotation speeds of said substrate and said polishing pad and equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to the end of the polishing.  
     
     
         3 . The polishing method according to  claim 1 , which comprises setting a rotation speed of said substrate, a rotation speed of said polishing pad, a polishing period, and a polishing pressure and further setting a rotation speed switching time, performing such calculation as to equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to the end of the polishing, based on these set rotation speed of said substrate, rotation speed of said polishing pad, polishing period, and rotation speed switching time, and driving said substrate and said polishing pad at respective rotation speeds based on the result of the calculation.  
     
     
         4 . The polishing method according to  claim 1 , which comprises storing a rotation speed switching time and either one or both of rotation speeds of said substrate and said polishing pad and performing such control as to equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to the end of the polishing.  
     
     
         5 . A polishing apparatus comprising driving means for rotating a substrate and driving means for rotating a polishing pad and constructed to keep the polishing pad under a predetermined pressure and in a state of contact with a device forming surface of said substrate and perform polishing while rotating each of said substrate and said polishing pad, 
 said polishing apparatus comprising measuring means for measuring symmetry of a film on an alignment mark for alignment of said substrate or an input part for inputting symmetry of a film on an alignment mark, and control means for controlling a rotation speed of at least either one of said substrate and said polishing pad according to the symmetry of the film on the alignment mark, thus measured or inputted.    
     
     
         6 . The polishing apparatus according to  claim 5 , wherein said control means performs such control as to change rotation speeds of said substrate and said polishing pad and equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to an end of the polishing.  
     
     
         7 . The polishing apparatus according to  claim 5 , wherein said control means comprises first input means for setting a rotation speed of said substrate, a rotation speed of said polishing pad, a polishing period, and a polishing pressure and second input means for setting a rotation speed switching time, and said control means further comprises an operation part for performing such calculation as to equate total numbers of rotations of said substrate and polishing pad from values inputted by said first and second input means, and a control part for driving each of said substrate and said polishing pad at respective rotation speeds based on the rotation speeds inputted by said first input means and the result of the calculation by said operation part.  
     
     
         8 . The polishing apparatus according to  claim 5 , which comprises a memory section for storing a rotation speed switching time and either one or both of rotation speeds of said substrate and said polishing pad, wherein control is implemented so as to equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to an end of the polishing.  
     
     
         9 . A device fabrication method comprising: 
 a step of forming a film covering an alignment mark for alignment of a substrate on a device forming surface of said substrate; and    a step of keeping a polishing pad under a predetermined pressure and in a state of contact with said film and performing polishing while rotating each of said substrate and polishing pad;    said device fabrication method comprising a step of measuring symmetry of the film on said alignment mark after an end of the polishing of said substrate or in the middle of the polishing and controlling a rotation speed of the substrate and/or the polishing pad according to the symmetry of the film on said alignment mark, thus measured.    
     
     
         10 . The device fabrication method according to  claim 9 , wherein control is implemented so as to change rotation speeds of said substrate and said polishing pad and equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to the end of the polishing.  
     
     
         11 . The device fabrication method according to  claim 9 , which comprises setting a rotation speed of said substrate, a rotation speed of said polishing pad, a polishing period, and a polishing pressure and further setting a rotation speed switching time, performing such calculation as to equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to the end of the polishing, based on these set rotation speed of said substrate, rotation speed of said polishing pad, polishing period, and rotation speed switching time, and driving said substrate and said polishing pad at respective rotation speeds based on the result of the calculation.  
     
     
         12 . The device fabrication method according to  claim 9 , which comprises storing a rotation speed switching time and either one or both of rotation speeds of said substrate and said polishing pad and performing such control as to equate total numbers of rotations of said substrate and said polishing pad from a start of the polishing to the end of the polishing.