Wafer holder protecting wafer against electrostatic breakdown

Abstract

A wafer holder includes a mounting plate for mounting a wafer and having a plurality of fluid holes, a decompressor for absorbing the wafer toward the mounting plate while sucking air between the mounting plate and the wafer through the fluid holes, and a liquid supply unit for supplying a liquid toward the wafer to release the wafer from the wafer holder. The liquid has a specific resistance lower than the specific resistance of water.

What is claimed is:  
     
         1 . A wafer holder comprising: 
 a mounting plate for mounting thereon a wafer;    at least one fluid hole formed on said mounting plate;    a fluid exhaustion unit selectively communicating with said fluid hole for sucking fluid through said fluid hole for exhaustion; and    a liquid supply unit selectively communicating with said fluid hole for supplying a liquid through said fluid hole, said liquid having a specific resistance lower than a specific resistance of water.    
     
     
         2 . The wafer holder as defined in  claim 1 , wherein said liquid supply unit includes a regulator controlling a pressure and a flow rate of said liquid before supplying said liquid through said fluid hole.  
     
     
         3 . The wafer holder as defined in  claim 1 , wherein said liquid has a specific resistance of 0.5MΩ-cm or lower.  
     
     
         4 . The wafer holder as defined in  claim 1 , wherein said liquid is obtained by dissolving carbon dioxide into water.  
     
     
         5 . The wafer holder as defined in  claim 1 , wherein said liquid includes ammonium and water.  
     
     
         6 . The wafer holder as defined in  claim 1 , wherein said at least one fluid hole include a plurality of fluid holes.  
     
     
         7 . The wafer holder as defined in  claim 1 , wherein said fluid hole has a larger cross section as viewed toward an exit of said fluid hole on said mounting plate.  
     
     
         8 . The wafer holder as defined in  claim 1 , wherein said mounting plate includes a plurality nozzles, each of said nozzles including said plurality of fluid holes.  
     
     
         9 . The wafer holder as defined in  claim 1 , further comprising a pure water supply unit for preparing pure water, wherein said liquid and said pure water is selectively supplied through said fluid hole.  
     
     
         10 . A method for treating a wafer by using a mounting plate having a fluid hole, said method comprising the steps of: 
 absorbing the wafer to the mounting plate while sucking air between the wafer and the mounting plate through the fluid hole; and    releasing the wafer from the mounting plate while supplying a liquid having a specific resistance lower than a specific resistance of water.    
     
     
         11 . The method as defined in  claim 10 , wherein said liquid has a specific resistance of 0.5MΩ-cm or lower.  
     
     
         12 . The method as defined in  claim 10 , further comprising the step of supplying pure water through the fluid hole.  
     
     
         13 . A method for chemically-mechanically polishing a wafer by using a polishing head and an associated mounting plate having a fluid hole, said method comprising the steps of: 
 absorbing the wafer to the mounting plate while sucking air between the wafer and the mounting plate through the fluid hole;    releasing the wafer from the wafer holder while supplying a liquid having a specific resistance lower than a specific resistance of water; and    supplying pure water through the fluid hole to wash the polishing head.