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- 

