Polishing method and polishing apparatus for workpiece

Abstract

A polishing method that can reduce influence of polishing liquid (e.g., slurry) on measuring of a film thickness of a workpiece and can achieve accurate measuring of the film thickness is disclosed. The polishing method includes pressing the workpiece against a polishing pad by a polishing head while polishing liquid is present on the polishing pad to polish the workpiece; during polishing of the workpiece, directing light from an optical sensor head onto the workpiece and receiving reflected light from the workpiece by the optical sensor head, the optical sensor head being disposed in the polishing table; determining a film thickness of the workpiece based on a spectrum of the reflected light; and during polishing of the workpiece, supplying cleaning liquid from a cleaning nozzle to a target position which is located just above the optical sensor head.

What is claimed is: 
     
         1 . A polishing method for a workpiece, comprising:
 supplying polishing liquid onto a polishing pad while rotating a polishing table supporting the polishing pad;   pressing the workpiece against the polishing pad by a polishing head while the polishing liquid is present on the polishing pad to polish the workpiece;   during polishing of the workpiece, directing light from an optical sensor head onto the workpiece and receiving reflected light from the workpiece by the optical sensor head, the optical sensor head being disposed in the polishing table;   determining a film thickness of the workpiece based on a spectrum of the reflected light; and   during polishing of the workpiece, supplying cleaning liquid from a cleaning nozzle to a target position which is located just above the optical sensor head, the cleaning nozzle being located above the polishing pad and located upstream of the polishing head in a rotating direction of the polishing table.   
     
     
         2 . The polishing method according to  claim 1 , wherein supplying of the cleaning liquid from the cleaning nozzle is started when the target position is upstream of the polishing head. 
     
     
         3 . The polishing method according to  claim 2 , wherein supplying of the cleaning liquid from the cleaning nozzle is stopped before the target position is moved under the polishing head. 
     
     
         4 . The polishing method according to  claim 1 , wherein the cleaning liquid is intermittently supplied from the cleaning nozzle to the target position in synchronization with rotation of the polishing table. 
     
     
         5 . The polishing method according to  claim 4 , wherein a supply time of the cleaning liquid per one rotation of the polishing table is less than half a time of one rotation of the polishing table. 
     
     
         6 . The polishing method according to  claim 1 , further comprising:
 supplying gas from a gas nozzle to the target position during polishing of the workpiece, the gas nozzle being located above the polishing pad and located upstream of the cleaning nozzle in the rotating direction of the polishing table.   
     
     
         7 . The polishing method according to  claim 6 , wherein the gas and the cleaning liquid are alternately supplied to the target position from the gas nozzle and the cleaning nozzle during one rotation of the polishing table. 
     
     
         8 . A polishing apparatus for a workpiece, comprising:
 a polishing table configured to support a polishing pad;   a table motor configured to rotate the polishing table;   a polishing-liquid supply nozzle configured to supply polishing liquid onto the polishing pad;   a polishing head configured to press the workpiece against the polishing pad to polish the workpiece while the polishing liquid is present on the polishing pad;   an optical sensor head arranged to direct light to the workpiece and receive reflected light from the workpiece during polishing of the workpiece, the optical sensor head being disposed in the polishing table;   a spectrum processing device configured to determine a film thickness of the workpiece based on a spectrum of the reflected light;   a cleaning nozzle configured to supply cleaning liquid to a target position which is located just above the optical sensor head, the cleaning nozzle being located above the polishing pad and located upstream of the polishing head in a rotating direction of the polishing table;   a cleaning-liquid supply valve coupled to the cleaning nozzle; and   a fluid supply controller configured to instruct the cleaning-liquid supply valve to supply the cleaning liquid from the cleaning nozzle to the target position during polishing of the workpiece.   
     
     
         9 . The polishing apparatus according to  claim 8 , wherein the fluid supply controller is configured to instruct the cleaning-liquid supply valve to start supplying the cleaning liquid from the cleaning nozzle when the target position is upstream of the polishing head. 
     
     
         10 . The polishing apparatus according to  claim 9 , wherein the fluid supply controller is configured to instruct the cleaning-liquid supply valve to stop supplying the cleaning liquid from the cleaning nozzle before the target position moves under the polishing head. 
     
     
         11 . The polishing apparatus according to  claim 8 , wherein the fluid supply controller is configured to instruct the cleaning-liquid supply valve to intermittently supply the cleaning liquid from the cleaning nozzle to the target position in synchronization with rotation of the polishing table. 
     
     
         12 . The polishing apparatus according to  claim 11 , wherein a supply time of the cleaning liquid per one rotation of the polishing table is less than half a time of one rotation of the polishing table. 
     
     
         13 . The polishing apparatus according to  claim 8 , further comprising:
 a gas nozzle configured to supply gas to the target position, the gas nozzle being located above the polishing pad and located upstream of the cleaning nozzle in the rotating direction of the polishing table; and   a gas supply valve coupled to the gas nozzle, the fluid supply controller being configured to control operation of the gas supply valve.   
     
     
         14 . The polishing apparatus according to  claim 13 , wherein the fluid supply controller is configured to instruct the cleaning-liquid supply valve and the gas supply valve to alternately supply the gas and the cleaning liquid from the gas nozzle and the cleaning nozzle to the target position during one rotation of the polishing table. 
     
     
         15 . The polishing apparatus according to  claim 8 , further comprising a flow-rate regulating valve configured to regulate a flow rate of the cleaning liquid supplied from the cleaning nozzle to the target position.