Abstract
We deposited electroplating copper with conventional sputtered Cu seed-layer on the diffusion barrier Ta and TaN. With various deposition recipe, from XRD, SEM and resistivity, we studied the properties of electroplated Cu film. We also developed the displacement method of Cu seed-layer on Si film with electrochemical reaction, integrated the electrolplating Cu film to fabricate MOS capacitors. From C-V, Auger and SIMS, we studied the thermal stability of the multi-layer. First, we deposited blanked electroplating copper on different diffusion barriers. At various deposition temperature and current density, we electroplated Cu films and measured the resistivity, crystal orientation, grain size of the film from four-point probe, XRD, and SEM. Secondly, we deposited Cu seed-layer with displacement reaction. With various reaction time, silicon film thickness and adhesion layer, we measured the resistivity, adhesion and grain size. Meanwhile, we fabricated the poly-silicon/Ta/SiO2/Si structure. After displacing Poly-Si with Cu seed-layer, we then deposited electroplating Cu film and made MOS capacitors. After sintering at 300。C to 500。C for 30 min, we studied the flat-band shift of the C-V (1MHz) curve and compared it to the MOS capacitors using conventional methods. We also observed the diffusion of Cu ions after sintering by Auger and SIMS depth profiles. From above study, electroplated Cu film has the best resistivity of 1.86μΩ•cm, grain size of 300A, the preferred crystal orientation of Cu(111). With two different methods fabricated Cu seed-layers, electroplated Cu deposited on diffusion barrier, both had the thermal stability of 450。C, and shown the ability of filling 0.35μm vias with aspect ratio~2.5. The technique of displacement method of Cu seed-layer has better step coverage than the conventional sputtered Cu seed-layers. The former method is cheaper than CVD Cu, we believe that the integration of new displaced Cu seed-layer and electroplated Cu film will have benefit to develop the future ULSI process.