Aug. 7, 2008  9  US 2008/0188162 Al  fixed to the polishing-head drive shaft  11,  and driven pins (not  shown) fixed to the housing  2a.  The driving pins and the  driven pins are vertically movable relative to each other.  Accordingly, even when the head body  2  is tilted, the pins still  engage each other, with contact points of the pins being  shifted. The rotation transmitting mechanism thus securely  transmits the torque of the polishing-head drive shaft  11  to the  head body  2.  [0128]  In the space formed in the head body  2  and the  retainer ring  3  fixed integrally to the head body  2,  there are  housed an elastic pad  4  to be in contact with the substrate W,  an annular holder ring  5,  and a substantially disk-shaped  chucking plate  6  for supporting the elastic pad  4.  The elastic  pad  4  is sandwiched, at its peripheral portion, between the  holder ring  5  and the chucking plate  6  fixed to a lower end of  the holder ring  5.  The elastic pad  4  is shaped so as to cover a  lower surface of the chucking plate  6.  A space is thus formed  between the elastic pad  4  and the chucking plate  6.  [0129]  A  pressure sheet  7,  composed of an elastic mem› brane, is provided so as to stretch between the holder ring  5  and the head body  2.  One end of the pressure sheet  7  is  sandwiched between the housing  2a  and the pressure-sheet  support  2b  of the head body  2,  and another is sandwiched  between an upper end portion  Sa  and a stopper portion  Sb  of  the holder ring  5.  A pressure chamber  21  is formed inside the  head body  2.  This pressure chamber  21  is defined by the head  body  2,  the chucking plate  6,  the holder ring  5,  and the  pressure sheet  7.  The pressure chamber  21  is located above  the chucking plate  6.  As shown in FIG.  5,  a fluid passage  31,  which comprises a tube and connectors, is provided so as to  communicate with the pressure chamber  21.  The pressure  chamber  21  is coupled to the compressed air source  120  via a  regulator RE2 provided in the fluid passage  31.  The pressure  sheet  7  is made from, for example, a rubber material having  excellent strength and durability, such as ethylene-propylene  rubber (EPDM), polyurethane rubber, or silicon rubber.  [0130]  If the pressure sheet  7  is made from an elastic mate› rial, such as rubber, and is sandwiched between the retainer  ring  3  and the head body  2,  a desirable flat plane may not be  obtained in the lower surface of the retainer ring  3,  because of  elastic deformation of the elastic pressure sheet  7.  In order to  avoid such a drawback, the pressure-sheet support  2b  is sepa› rately provided, according to this embodiment, so as to sand› wich and fix the pressure sheet  7  between the housing  2a  and  the pressure-sheet support  2b  of the head body  2.  [0131]  It is possible to make the retainer ring  3  vertically  movable relative to the head body  2  or to make the retainer  ring  3  operable to press the polishing pad  101  independent of  the head body  2,  as disclosed in Japanese Patent Application  No. 8-50956 (Laid-Open Publication No. 9-168964) or Japa› nese Patent Application No. 11-294503. In such a case, the  above-described structure of fixing the pressure sheet  7  may  not necessarily be employed.  [0132]  A center bag (a central contact member)  8  and a ring  tube ( an outer contact member)  9,  which are contact members  to be in contact with the elastic pad  4,  are provided in the  space formed between the elastic pad  4  and the chucking plate  6.  As shown in FIGS.  5  and  6,  in this embodiment, the center  bag  8  is disposed on the central portion of the lower surface of  the chucking plate  6,  and the ring tube  9  is disposed outside of  the center bag  8  so as to surround the center bag  8.  The elastic  pad  4,  the center bag  8,  and the ring tube  9  are made from  rubber having excellent strength and durability, such as eth- ylene-propylene rubber (EPDM), polyurethane rubber, or  silicon rubber, as with the pressure sheet  7.  [0133]  The space formed between the chucking plate  6  and  the elastic pad  4  is divided by the center bag  8  and the ring  tube  9  into plural chambers: a pressure chamber  22  formed  between the center bag  8  and the ring tube  9;  and a pressure  chamber  23  formed outside the ring tube  9.  [0134]  The center bag  8  comprises an elastic membrane  81,  which is to be in contact with an upper surface of the elastic  pad  4,  and a center bag holder (holding member)  82  detach› ably holding the elastic membrane  81.  The center bag holder  82  has screw holes  82a  formed therein. Screws  55  are inserted  into the screw holes  82a  to thereby allow the center bag  8  to  be detachably mounted on the central portion of the lower  surface of the chucking plate  6.  Inside the center bag  8,  a  central pressure chamber  24  is defined by the elastic mem› brane  81  and the center bag holder  82.  [0135]  Similarly, the ring tube  9  comprises an elastic mem› brane  91,  which is to be in contact with the upper surface of  the elastic pad  4,  and a ring tube holder (holding member)  92  detachably holding the elastic membrane  91.  The ring tube  holder  92  has screw holes  92a  formed therein. Screws  56  are  inserted into the screw holes  92a  to thereby allow the ring  tube  9  to be detachably mounted on the lower surface of the  chucking plate  6.  Inside the ring tube  9,  an intermediate  pressure chamber  25  is defined by the elastic membrane  91  and the ring tube holder  92.  [0136]  Fluid passages  33, 34, 35,  and  36,  each including a  tube and connectors, are provided so as to communicate with  the pressure chambers  22  and  23,  the central pressure cham› ber  24,  and the intermediate pressure chamber  25,  respec› tively. The pressure chambers  22  to  25  are coupled to the  compressed air source  120  as a pressurized-fluid supply  source via regulators RE3, RE4, RES, and RE6 respectively  provided in the fluid passages  33-36.  The above-described  fluid passages  31, 33-36  are coupled to the respective regu› lators RE2-RE6 via rotary joints (not shown) provided at an  upper end of the polishing-head drive shaft  11.  [0137]  A pressurized fluid (e.g., pressurized air) is to be  supplied to the above-described pressure chambers  21-25,  or  atmospheric pressure or vacuum is to be produced in the  pressure chambers  21-25  via the fluid passages  31, 33-36.  As  shown in FIG.  4,  the pressures of pressurized fluids to be  supplied to the pressure chambers  21-25  can be adjusted by  the regulators RE2-RE6 provided in the fluid passages  31,  33-36.  The pressures in the pressure chambers  21-25  can thus  be controlled independently, or atmospheric pressure or  vacuum can be produced in the pressure chambers  21-25.  [0138]  In this manner, by changing the pressures in the  pressure chambers  21-25  independently via the regulators  RE2-RE6, the elastic pad  4  can press the substrate W against  the polishing pad  101  with pressing forces adjusted for  respective portions ( divisional areas) of the substrate W. The  pressure chambers  21-25  may be coupled to a vacuum source  121,  as desired.  [0139]  As shown in FIG.  4,  the upper surface of the polish› ing table  100  of the electrochemical mechanical polishing  apparatus  250  is covered with a disk-shaped insulating plate  252,  and a first electrode (cathode)  256,  coupled to one of  poles of a power source  254,  is disposed on an upper surface  of the insulating plate  252.  In this embodiment, the first  electrode  256  is comprised of plural (three) ring-shaped  divided electrodes  256a  to  256c  which are concentrically  arranged. A cylindrical core  258  is disposed in a center of the 