Study on Cu Passivation Film’s Forming Condition in HEDP Electrolyte with BTA and Chloride Ion

The influence of corrosion inhibitor BTA, chloride ion and anodic potential on the formation of copper passivation film was studied in the electrolyte of 18wt% HEDP by using Linear Sweep Voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The results show that the increase of BTA concentration contributes to the formation of surface passivation film, and the chloride ion can promote the formation of the Cu passivation film at low concentrations but break it down when its concentration exceeds a certain limit. For each electrolyte there is a threshold anodic potential maintaining good passivation: the interfacial charge transfer resistance increases with the anodic potential when it is below the threshold potential and decreases when it is above the threshold potential. Smooth surface can be obtained by ECMP at the optimal processing condition.

ECMP Enhances the Planarization Efficiency — a Phenomenon of Reverse Topography during Cu Removal

ABSTRACTPlanarization efficiency is a key parameter to evaluate the process effectiveness of CMP. When the Cu thickness was removed beyond the step height, under certain conditions, the recessed trenches become protruded, resulting in reverse topography. This reverse topography during bulk Cu removal can only be attributed to the low down force polishing, electrical driving Cu removal and Cu passivation mechanism in ECMP process. In this paper, the concept of reverse topography is introduced and the removal selectivity difference on the trench area and field area during bulk Cu removal is discussed. In ECMP, a “real” 100% planarization efficiency can be achieved when the Cu thickness removed is less than the trench step height. This new understanding in planarization efficiency sheds lights on ways to improve CMP productivity