A novel surface cleaning for copper interconnectionusing ammonium decomposed species generated by hot wire

摘要

Copper (Cu) has been the material of choice to replace aluminum alloys for sub-0.13-um multilevelinterconnection due to its lower resistivity and higher electro migration resistance [1,2]. Post chemicalmechanical polishing (CMP) cleaning is a key process for Cu CMP in dual damasceneinterconnection technology. During the post CMP cleaning, it is an important issue to minimizeorganic contamination and Cu oxidation. There are some reports to remove Cu oxide layers. Chemicalprocesses such as H2 and ammonium (NH3) plasma reduction are being investigated [3-7]. Thesemethods have the problem of the plasma damage. Lee et al. proposed Cu oxide reduction usingvacuum annealing [8]. However, it seems not suitable for the ULSI process, because theheat-treatment of 400°C is necessary. For these requirements, a novel Cu interconnection cleaningmethod using atomic hydrogen generated on a heated tungsten catalyzer was proposed [9]. It isknown that the heated tungsten catalyzer generates atomic hydrogen with high efficiency. It has beenreported that the generation of atomic hydrogen by this method is at least 10 times more efficient thanthat by the plasma method [10]. Moreover, the control of the amount of the atomic hydrogengeneration of this method is also easy. There are a lot of reports concerning ULSI process and otherapplications using atomic hydrogen, such as control of the career density of the Cu oxide [11],photoresist removal [12] and so on [13-16]. However, the atomic hydrogen has the possibility ofcausing the damage of the circumference material of the Cu interconnections. In this study weproposed a novel Cu interconnection cleaning method using NH3 decomposed species generated on aheated tungsten catalyzer instead of atomic hydrogen.