Abstract
We used electroless copper deposition on the diffision barrier TaN with variable deposition recipy, then compared the film properties and thermal stability with electroless copper deposition on Ta and TiN. First, we deposited blanket electroless copper on Ta, TaN, and TiN. At various deposition and sintering temperature, then we measured the resistivity, crystal orientation, grain size from four-point probe, XRD, and SEM. We study the Cu film deposition with additives dipyridyl or polyethylene glycol (PEG). Dipyridyl densified copper film, and reduced the resistivity. After sintering at 200。C for 30 min, the copper film could be also hard-grained, and the resistivity could be reduced from 5% ~ 10%. Furthermore, the amount of dippyridyl could also influence grain size, and the resistivity of the film. Second, we deposited above copper on 0.35~0.5 □m via with aspect ratio~3. From SEM, the conformity of the film could be observed. The deposited Cu film with additives, dipyridyl or polyethylene glycol(PEG),could perfectly fill above vias. Third, we fabricated the Cu(electroless copper)/barrier/SiO2/Si capacitor. After sintering at 400。C/450。C for 30 min, we study the thermal stability of above capacitors with barriers Ta, TaN, and TiN from the C-V curve and SIMS. After sintering at 400。C for 30 min, we observed the flat band shift of the C-V (1MHz) curve of copper deposition on Ta, TiN, but the small change on low frequency C-V curve for TaN layer was found after sintering at 450。C for 30min. From SIMS, we did not observe for the Cu diffusion into SiO2 for the sample sintered at 400。C. From above study, electroless copper deposition on TaN has the best thermal stability(>400。C), the lowest resistivity 2.2 □Ω•cm, and the conformity of gap-filling of electroless copper is excellent for 0.35~0.5□m via with aspect ratio~3.