recesses fig2 a through 2 b will be used for this a recess is thereby defined as any deviation of a copper surface from an ideal or totally flat or planarized copper surface these observations can be summarized as follows and are based on empirical observations of polished copper surface 1 the severity of recesses is higher in higher levels of metals as opposed to lower levels of metal that is the occurrence of recesses is for instance more severe in level 6 metal m6 than in level 3 metal m3 2 the recesses are dependent of the length of a copper interconnect line to which an overlying via interconnect is attached the longer the interconnect line the more severe the recess in the surface of the polished via and 3 the recesses are dependent on the size of the surface that is being polished a small surface area has more recesses than a larger surface area for an explanation of the above highlighted observations the following is suggested 1 higher level of copper are created in overlying layers of dielectric and are therefore less firmly anchored or supported than the lower levels of metal causing increased likelihood of vibration of the higher levels of copper 2 a shorter interconnect line to which an overlying copper via is attached is a firmer body of metal than a longer interconnect line the longer interconnect line is therefore more prone to vibrate a vibration that is transferred to the thereto connected via resulting in unstable contact between the polishing pad and the surface of the via at the time of polishing of the surface of the via and 3 a larger surface area will more uniformly contact a polishing pad than a smaller surface area resulting in more uniform polishing of the.