Method of inflating elastic membrane of polishing head, and polishing head system

Abstract

A technique is disclosed that can allow an elastic membrane to be inflated into a desired shape when a workpiece is released from a polishing head, or when the workpiece is held on the polishing head, thereby avoiding excessive stress on the workpiece. The method includes supplying a gas into a first pressure chamber and a second pressure chamber at a first flow rate and a second flow rate regulated by a first flow-rate control valve and a second flow-rate control valve to inflate an elastic membrane of a polishing head when a polished workpiece is released from the polishing head, or when a workpiece to be polished is held on the polishing head. The first pressure chamber and the second pressure chamber are formed by the elastic membrane.

What is claimed is: 
     
         1 . A method of inflating an elastic membrane of a polishing head, comprising:
 supplying a gas into a first pressure chamber and a second pressure chamber at a first flow rate and a second flow rate regulated by a first flow-rate control valve and a second flow-rate control valve when a polished workpiece is released from the polishing head, or when a workpiece to be polished is held on the polishing head, the first pressure chamber and the second pressure chamber being formed by the elastic membrane.   
     
     
         2 . The method according to  claim 1 , wherein a volume of the first pressure chamber is larger than a volume of the second pressure chamber, and the first flow rate is higher than the second flow rate. 
     
     
         3 . The method according to  claim 1 , wherein the gas is supplied into the first pressure chamber at the first flow rate until a cumulative value of the first flow rate reaches a first target flow-rate cumulative value, and the gas is supplied into the second pressure chamber at the second flow rate until a cumulative value of the second flow rate reaches a second target flow-rate cumulative value. 
     
     
         4 . The method according to  claim 1 , further comprising:
 calculating the first flow rate by dividing a first target flow-rate cumulative value for the first pressure chamber by preset operating time; and   calculating the second flow rate by dividing a second target flow-rate cumulative value for the second pressure chamber by preset operating time.   
     
     
         5 . The method according to  claim 1 , further comprising changing at least one of the first flow rate and the second flow rate while supplying the gas into the first pressure chamber and the second pressure chamber. 
     
     
         6 . The method according to  claim 1 , further comprising:
 measuring a flow rate of the gas supplied to the first pressure chamber while polishing a workpiece with the polishing head, the flow rate being measure by the first flow-rate control valve;   calculating a polishing flow-rate cumulative value which is a cumulative value of the measured flow rate; and   determining a malfunction of the elastic membrane or a polishing abnormality of the workpiece based on a change in the polishing flow-rate cumulative value.   
     
     
         7 . A polishing-head system for polishing a workpiece, comprising:
 a polishing head having an elastic membrane forming a first pressure chamber and a second pressure chamber;   a first gas delivery line and a second gas delivery line that communicate with the first pressure chamber and the second pressure chamber, respectively;   a first flow-rate control valve and a second flow-rate control valve coupled to the first gas delivery line and the second gas delivery line, respectively; and   a system controller configured to instruct the first flow-rate control valve and the second flow-rate control valve to supply a gas into the first pressure chamber and the second pressure chamber at a first flow rate and a second flow rate when a polished workpiece is released from the polishing head, or when a workpiece to be polished is held on the polishing head.   
     
     
         8 . The polishing-head system according to  claim 7 , wherein a volume of the first pressure chamber is larger than a volume of the second pressure chamber, and the first flow rate is higher than the second flow rate. 
     
     
         9 . The polishing-head system according to  claim 7 , wherein the system controller is configured to:
 calculate a cumulative value of the first flow rate;   instruct the first flow-rate control valve to supply the gas into the first pressure chamber at the first flow rate until the cumulative value of the first flow rate reaches a first target flow-rate cumulative value;   calculate a cumulative value of the second flow rate; and   instruct the second flow-rate control valve to supply the gas into the second pressure chamber at the second flow rate until the cumulative value of the second flow rate reaches a second target flow-rate cumulative value.   
     
     
         10 . The polishing-head system according to  claim 7 , wherein the system controller is configured to:
 calculate the first flow rate by dividing a first target flow-rate cumulative value for the first pressure chamber by preset operating time; and   calculate the second flow rate by dividing a second target flow-rate cumulative value for the second pressure chamber by preset operating time.   
     
     
         11 . The polishing-head system according to  claim 7 , wherein the system controller is configured to instruct at least one of the first flow-rate control valve and the second flow-rate control valve to change at least one of the first flow rate and the second flow rate while the gas is supplied into the first pressure chamber and the second pressure chamber. 
     
     
         12 . The polishing-head system according to  claim 7 , wherein the first flow-rate control valve is configured to measure a flow rate of the gas supplied to the first pressure chamber while a workpiece is polished with the polishing head; and
 the system controller is configured to calculate a polishing flow-rate cumulative value which is a cumulative value of the measured flow rate and determine a malfunction of the elastic membrane or a polishing abnormality of the workpiece based on a change in the polishing flow-rate cumulative value.