Polishing head, polishing apparatus, and polishing method

Abstract

A polishing head includes a backing material including a suction surface facing an upper surface of a workpiece and an opposite pressing surface, a workpiece pressurization plate that is provided at a center portion of the pressing surface, and a first fluid chamber provided between the workpiece pressurization plate and the backing material. A control unit switches between front surface reference polishing in which inside of the first fluid chamber is pressurized to polish the workpiece in a state where the workpiece pressurization plate and the backing material are separated from each other, and back surface reference polishing in which the inside of the first fluid chamber is vacuumized or opened to the atmosphere and downward force is applied to the workpiece pressurization plate to polish the workpiece in a state where the workpiece pressurization plate and the backing material are in contact with each other.

What is claimed is: 
     
         1 . A polishing head that is fixed to a head shaft that is capable of vertically moving and rotating to be vertically movable and rotatable, and polishes a workpiece by holding the workpiece and rotating and pressing the workpiece against a polishing pad, the polishing head comprising:
 a backing material including a suction surface facing an upper surface of the workpiece and a pressing surface opposite to the suction surface;   a workpiece pressurization plate that is provided at a center portion of the pressing surface to be contactable with and separable from the pressing surface, and is vertically movable;   a first fluid chamber provided between the workpiece pressurization plate and the backing material; and   a first pressure adjustment mechanism that adjusts a pressure in the first fluid chamber, wherein   a control unit performs control to switch between
 front surface reference polishing in which control is performed to pressurize inside of the first fluid chamber to press the workpiece from above in a state where a lower surface of the workpiece pressurization plate and the pressing surface of the backing material are separated from each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other, and 
 back surface reference polishing in which control is performed to vacuumize or open the inside of the first fluid chamber to atmosphere and to apply downward force to the workpiece pressurization plate to press the workpiece from above in a state where the lower surface of the workpiece pressurization plate and the pressing surface of the backing material are in contact with each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other. 
   
     
     
         2 . The polishing head according to  claim 1 , further comprising:
 a retainer provided to an outer circumference portion of the suction surface; and   a retainer pressurization unit that is provided to an outer circumference portion of the pressing surface and is vertically movable, wherein   the control unit applies forces in relatively opposite vertical directions to the retainer pressurization unit and the workpiece pressurization plate,   to perform the front surface reference polishing in a state where a lower end surface of the workpiece pressurization plate is located relatively higher than a lower end surface of the retainer pressurization unit, and   to perform the back surface reference polishing in a state where the lower end surface of the workpiece pressurization plate and the lower end surface of the retainer pressurization unit are flush in a horizontal direction, or in a state where the lower end surface of the workpiece pressurization plate is located relatively lower than the lower end surface of the retainer pressurization unit.   
     
     
         3 . The polishing head according to  claim 2 , comprising a pressing part that brings the workpiece pressurization plate and the retainer pressurization unit into contact with each other for relative fixing, and
 functions, when the workpiece is polished, as a stopper that restricts movement of the workpiece pressurization plate and the retainer pressurization unit in a predetermined direction to achieve relative positional relationship.   
     
     
         4 . The polishing head according to  claim 3 , wherein a gap is formed between the retainer and the polishing pad, when the workpiece is pressed against the polishing pad in a state where the workpiece pressurization plate and the retainer pressurization unit are in contact with each other with the pressing part provided in between at a time of the back surface reference polishing. 
     
     
         5 . The polishing head according to  claim 1 , wherein
 the workpiece pressurization plate is formed by two layers including an upper plate and a lower plate,   the polishing head further comprises:
 a second fluid chamber that is provided between the upper plate and the lower plate; and 
 a second pressure adjustment mechanism that adjusts a pressure in the second fluid chamber, and 
   the lower plate includes a flow channel communicating the first fluid chamber and the second fluid chamber.   
     
     
         6 . The polishing head according to  claim 5 , wherein the flow channel is formed with the lower plate formed by a porous material. 
     
     
         7 . The polishing head according to  claim 1 , wherein the workpiece pressurization plate includes a flow channel communicating the first fluid chamber and a first flow path provided with the first pressure adjustment mechanism. 
     
     
         8 . The polishing head according to  claim 7 , wherein the flow channel is formed as a groove in the lower surface of the workpiece pressurization plate. 
     
     
         9 . The polishing head according to  claim 1 , wherein
 the workpiece pressurization plate includes a flow channel communicating the first fluid chamber and a fifth flow path provided with a fifth pressure adjustment mechanism, and   the fifth pressure adjustment mechanism is configured to be capable of vacuumizing at least the flow channel through the fifth flow path.   
     
     
         10 . The polishing head according to  claim 1 , further comprising a head base portion fixed to the head shaft, wherein
 the workpiece pressurization plate is fixed to the head base portion and configured to be vertically moved by driving of the head shaft, and   the control unit performs, at a time of the back surface reference polishing, control to apply driving force for lowering the workpiece pressurization plate via the head shaft, to apply downward force to the workpiece pressurization plate, or   the workpiece pressurization plate is suspended from or in slidably close contact with the head base portion, and configured to vertically move with a pressure in a third fluid chamber provided between the head base portion and the workpiece pressurization plate adjusted by a third pressure adjustment mechanism, and   the control unit performs control, at the time of the back surface reference polishing, to pressurize inside of the third fluid chamber, to apply downward force to the workpiece pressurization plate.   
     
     
         11 . A polishing apparatus comprising the polishing head according to  claim 1 . 
     
     
         12 . A polishing method of polishing a workpiece held and pressed against a polishing pad by a polishing head including:
 a backing material that has a suction surface facing an upper surface of the workpiece and a pressing surface opposite to the suction surface; and   a workpiece pressurization plate that is provided at a center portion of the pressing surface to be contactable with and separable from the pressing surface and is vertically movable, the method comprising switching between   front surface reference polishing in which the workpiece pressurization plate is raised to form a closed space between the workpiece pressurization plate and the backing material, and the closed space is pressurized to press the workpiece from above in a state where a lower surface of the workpiece pressurization plate and the pressing surface of the backing material are separated from each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other, and   back surface reference polishing in which the closed space is vacuumized or opened to atmosphere and downward force is applied to the workpiece pressurization plate, to press the workpiece from above in a state where the lower surface of the workpiece pressurization plate and the pressing surface of the backing material are in contact with each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other.   
     
     
         13 . The polishing method according to  claim 12 , wherein by using the polishing head further including:
 a retainer provided to an outer circumference portion of the suction surface; and   a retainer pressurization unit that is provided to an outer circumference portion of the pressing surface and is vertically movable,   in the front surface reference polishing, the retainer pressurization unit is lowered to press the polishing pad in a periphery of the workpiece by the retainer, and   in the back surface reference polishing, a gap is formed between a lower end surface of the retainer and the polishing pad.