Multi-layer sub pad for cmp processes

An apparatus comprising:

• a top pad comprising a first plurality of protrusions and a first plurality of grooves between the first plurality of protrusions;
• an anti-deformation layer underlying the top pad, wherein the anti-deformation layer has a first Poisson's ratio;
• and
• a main support layer underlying the anti-deformation layer, wherein the main support layer has a second Poisson's ratio greater than the first Poisson's ratio.

A method for polishing a wafer, comprising:

• providing a polish pad comprising:
• a top pad;
• and
• a multi-layer sub pad underlying the top pad, the multi-layer sub pad comprising at least an anti-deformation layer and a main support layer, wherein the anti-deformation layer has a first Young's modulus and a first Poisson's ratio, and the main support layer has a second Young's modulus lower than the first Young's modulus and a second Poisson's ratio greater than the first Poisson's ratio;
• placing the wafer on the top pad;
• supplying a polishing slurry to an interface between the top pad and the wafer;
• and
• moving the wafer relative to the polish pad to perform a polishing process, wherein the top pad maintains contact with the wafer during the polishing process.