a platen for chemical mechanical polishing of a substrate includes a surface upon which a polishing pad can be placed , a support structure , and a controller . the surface has a first region and a second region and is operable to exert force against the polishing pad during polishing . the support structure is located beneath the second region and is operable to cause the second region to exert more force than the first region . the controller is operable to adjust the amount of force that is exerted by the second region .