Aug. 7, 2008  10  US 2008/0188162 Al  divided electrodes  256a to 256c.  Ring-shaped insulators  260a  to  260c  are disposed between the core  258  and the centrally› located divided electrode  256a,  between the divided elec› trode  256a  and the intermediately-located divided electrode  256b,  and between the divided electrode  256b  and the periph› erally-located divided electrode  256c,  respectively. The  divided electrodes  256a to 256c  are thus electrically insulated  from each other by the insulating plate  252  and the ring› shaped insulators  260a  to 260c.  [0140]  The divided electrodes  256a to 256c  are coupled  individually to feeding wires  266a  to 266c  extending from the  power source  254  via electrode wires  262a  to 262c  connected  respectively to the divided electrodes  256a to 256c  and  extending through an interior of the polishing table  100,  and  via electrode slip rings  264a  to 264c  mounted on a shaft  portion  100a  of the polishing table  100.  The feeding wires  266a  to 266c  extend via a variable resistance unit  270  having  variable resistors  268a  to 268c  respectively provided in the  feeding wires  266a  to 266c.  The variable resistors  268a  to  268c  are each capable of varying a value of resistance, e.g., in  a range ofO .1 to 10  Q.  A rotary connector may be used instead  of the slip rings.  [0141]  During polishing, the electric currents flowing (or  voltages to be applied) between the divided electrodes  256a  to  256c,  constituting the first electrode  256,  and a conductive  film, such as a copper film, formed on a surface of a substrate  facing the divided electrodes  256a to 256c,  can be adjusted by  individually controlling the respective variable resistors  268a  to  268c  interposed between the power source  254  and the  divided electrodes  256a to 256c.  This makes it possible to  carry out polishing of the substrate at a higher rate, with low  polishing pressure applied (i.e., in a low-polishing-pressure  area), and at a lower cost without providing plural power  sources, while ensuring uniformity of a polishing rate over  the surface of the substrate (a workpiece to be polished).  Furthermore, controlling of the variable resistors  268a  to  268c  is easier than individually controlling of plural power  sources.  [0142]  Upper surfaces of the first electrode  256,  the core  258,  and the ring-shaped insulators  260a  to 260c  lie in the  same plane, and these upper surfaces are covered with the  polishing pad  101  in their entirety. An upper surface of the  polishing pad  101  serves as a polishing surface. A film-thick› ness detection sensor (detecting section)  274,  e.g., an eddy› current sensor, is provided for measuring a thickness of a  conductive film, such as a copper film, formed on a surface of  a substrate. A base portion of the film-thickness detection  sensor (detecting section)  274  is embedded in the polishing  table  100  such that an upper end surface of the film-thickness  detection sensor  274  is flush with the upper surface of the first  electrode  256.  This film-thickness detection sensor  274  is  disposed either in the first electrode  256  with an insulator  being provided between the sensor  274  and the first electrode  256,  or in the ring-shaped insulator, so that the sensor is  electrically insulated from the first electrode  256.  A signal  from the film-thickness detection sensor  274  is sent to a  control section  280  via a sensor wire  276,  extending in the  interior of the polishing table  100,  and via a sensor slip ring  278  provided on a lower end of the shaft portion  100a  of the  polishing table  100.  The regulators  RE3  to  RE6  and the vari› able resistors  268a  to 268c  in the variable resistance unit  270  are individually controlled by an output signal from the con› trol section  280.  [0143]  A  table cover  282  is disposed so as to surround the  circumference of the polishing table  100.  A colunmar second  electrode (anode)  286,  coupled to the other pole of the power  source  254,  is supported by a support base  284  mounted on  the table cover  282.  This second electrode  286  is to supply an  electric current to the conductive film, such as the copper film  907  (see FIG.  1B),  formed on the surface of the substrate W  upon contact with the substrate W. When the polishing head  1  lowers the substrate W to bring the surface (lower surface) of  the substrate W into contact with the polishing surface of the  polishing pad  101,  a periphery of the surface (lower surface)  of the substrate Wis also brought into contact with an upper  surface of the second electrode  286.  The upper surface of the  second electrode  286  is substantially flush with the upper  surface (polishing surface) of the polishing pad  101.  The  second electrode  286  is made from an inert metal, such as Pt  or C, or a metal, such as SUS or Ti, plated with, e.g., Pt. The  second electrode  286  has a colunmar or spherical shape, and  is designed to make rotation during contact with the substrate  W The second electrode  286  is supported by the support base  284  via an elastic member so that the second electrode  286  can float. The polishing head  1  is operable to hold and press  the substrate against the polishing surface of the polishing pad  101  at polishing pressure of, e.g., not more than 70 hPa ( about  1 psi).  [0144]  In this embodiment, part of the substrate W, held by  the polishing head  1  in the polishing position, lies laterally to  the polishing table  100,  and the upper surface of the second  electrode  286  comes into contact with the lower surface of  that part of the substrate. It is possible to use a ring-shaped  second electrode, continuously extending around a circum› ference of the first electrode and insulated from the first  electrode, and to rotate the second electrode together with the  polishing table while allowing part of the second electrode to  be in contact with part of the lower surface of the substrate W  held by the polishing head  1.  The second electrode  286  may  be a pad-shaped conductive member.  [0145]  In this embodiment, the polishing pad  101  has a  large number of through-holes  1 Ola  over the surface thereof,  and is made from, for example, a foamed polyurethane resin  such as IC-1000, manufactured by Nitta Haas Inc. During  electrochemical mechanical polishing, an electric current  flows between the surface of the substrate W, coupled to the  second electrode  286,  and the first electrode  254  via an elec› trolytic solution that has flowed into the through-holes  101a.  The polishing pad  101  may have annular grooves or lattice› patterned grooves, in addition to the through-holes  101a  pro› vided over the polishing surface of the polishing pad  101  in its  entirety. If the polishing pad  101  itself is permeable to liquid,  like a PVA resin pad having continuous pores, the polishing  pad  101  may not necessarily have the through-holes.  [0146]  As shown in FIG.  4,  the electrolytic-solution supply  nozzle  102  extends in the radial direction of the polishing pad  101  and has a plurality of electrolytic-solution supply mouths  arranged at regular intervals along a length direction of the  electrolytic-solution supply nozzle  102.  [0147]  Polishing  operations  of the  electrochemical  mechanical polishing apparatus  250  having the above struc› tures will now be described. The substrate W is held on the  lower surface of the polishing head  1,  and the cylinder  111,  coupled to the polishing-head drive shaft  11,  is actuated to  press the retainer ring  3,  fixed to the lower end of the polishing  head  1,  against the polishing surface of the polishing pad  101  at predetermined pressure. Pressurized fluids with predeter-