Investigation on Abrasive Free Copper Chemical Mechanical Planarization for Cu/low k and Cu/ultra low k interconnects

Abstract

Abrasive Free Copper Chemical Mechanical Polishing (AF-CMP) was developed for Cu/low k materials. Blanket film Cu removal rate of 6000 Å/min with very less non-uniformity of 3% achieved for polishing pressure of 1.5 psi. CMP process window and lower critical pressure were identified with pattern wafers. Material removal mechanism was studied using surface morphology of Copper blanket wafers polished using different pressure, rotation rate and slurry flow rate. Material Removal Mechanism (wear mechanism) such as Chemical wear (etching) and mechanical wear (fatigue wear, particle adhesion wear and abrasion wear) have been found. The increase of slurry flow rate and relative velocity and the decrease of pressure give the dominance of chemical wear in material removal mechanism, and vice versa. Dishing control was achieved during Cu polish using different carrier/platen speed for Cu/SiLK™ patterned wafers. The cumulative distribution of the metal line-to-line leakage current measurements of wafers shows good performance and it is comparable to abrasive process.

Chemical Mechanical Planarization: Slurry Chemistry, Materials, and Mechanisms

“…It appears that abrasive-free CMP processes may have potential benefits in terms of defectivity; however significant process development efforts may be necessary before these new processes become viable options for a manufacturable planarization process for future copper interconnects. [172][173][174]…”

Effect of Mn (II) Ion on Abrasive-Free Polishing of Hard Disk Substrate

“…Recently the application fields of AFP focus on copper damascene interconnection and achieve satisfactory results [6,7]. And with more researchers' attention on AFP technology, it is applied in other materials.…”