Abstract
This study is to develop NiWMoB capping layer via electroless deposition. DMAB (dimethylamine borane) was chosen as the reducing agent due to its unique ability of selective deposition on copper surface without prior activation by Pd. In this study, various film compositions were fabricated, and their performance as capping layers were studied. The deposition rate reflects the relation: NiWB>NiWMoB>NiMoB. From the relation of deposition rate and the composition of the NiWMoB film, the introduction of both W and Mo leads to parallel competition in the reaction. The SEM photos reveal that deposits comprising W induces large grain size. On the other hand, the films consisting of amounts of Mo leads to small grain size. Based on the XRD patterns, the NiMoB or NiWMoB shows better thermal stability than NiWB films since no new phase appears after heat treatment with NiMoB or NiWMoB film. The NiWMoB films have superior thermal stability compared to NiWB films, and the addition of tungsten to NiMoB suppresses the adsorption of MoO42- on the catalytic surface, shortening the operating time. Under the condition of [Na2WO4]/ [Na2MoO4] =1 ([Na2MoO4]:0.003M), the morphology of the NiWMoB film presents uniform small grain and XRD data show nanocrystalline structure and sufficient thermal stability for NiWMoB deposits, rendering it a promising candidate as capping layer. The observation of Cu diffusion was evaluated by the depth profile. The results show that high-boron sample has no Cu diffusion, but low-boron sample has a little Cu diffusion. By utilizing XPS technique, the chemical states of Mo in the NiWMoB film were found affected by the addition of W.