Method and apparatus for controlling CMP pad surface finish

A method for improving step height performance in a CMP process for polishing semiconductor wafers, the method comprising:

• mounting a polishing pad onto a semiconductor wafer polisher and moving the polishing surface;
• reducing a roughness of the polishing surface;
• scanning a length of a polishing surface of the polishing pad and obtaining polishing surface scan data;
• determining a polishing surface flatness from the polishing surface scan data;
• and
• discontinuing roughness reduction of the polishing surface when the determined polishing surface flatness reaches a desired polishing surface flatness, wherein the polishing surface scan data comprises data containing polishing surface height measurements for points along the length of the polishing surface scanned, and wherein determining the polishing surface flatness from the polishing surface scan data comprises determining a pad flatness ratio for the polishing surface of the polishing pad, wherein the pad flatness ratio is determined according to the relationship:
• pad flatness ratio = polishing surface length - length of flat segments polishing surface scan length
• wherein the length of flat segments comprises a sum of lengths of pad surface within the polishing surface scan length, each flat segment having a length of at least 40 microns with a height deviation less than 2 microns, and the polishing surface scan length is a total length of polishing surface scanned.

A method for pre-conditioning a polishing pad to improve plurality of semiconductor wafers subsequently processed in a CMP process using the polishing pad, the method comprising:

• moving a polishing pad free of fixed abrasive particles;
• and
• flattening a polishing surface of the polishing pad with a pre-conditioning member;
• and
• applying a fluid to the polishing pad prior to flattening the polishing surface and ceasing application of any fluid when flattening the polishing surface.