Step coverage and composition of Pb(Zr,Ti)O₃ capacitors prepared on sub-micron three-dimensional trench structure by metalorganic chemical vapor deposition

Pb(Zr,Ti)O₃ (PZT) films were deposited into sub-micron trench structure consisting of SiO₂/TiAlN/Ti/SiO₂/Si to investigate their thickness and composition conformality by pulsed-metalorganic chemical vapor deposition (MOCVD) using liquid delivery source-supply system. Bis(dipivaloylmethanato)lead [Pb(DPM)₂], tetrakis(1-methoxy-2-methyl- 2-propoxy)zirconium [Zr(MMP)₄] and tetrakis(1-methoxy-2-methyl-2- propoxy)titanium [Ti(MMP)₄] were used as Pb, Zr and Ti source materials, respectively. In Arrhenius plot, the slopes of the straight lines for the constituents Pb, Zr and Ti in PZT film were almost the same at a lower deposition temperature (T_d) region as well as a higher T_d one. This means the composition change in the film against the T_d can be suppressed by using Pb(DPM)₂-Zr(MMP)₄-Ti(MMP) ₄-O₂ source system. From the results of Arrhenius plot, the T_ds were fixed on 450 and 540°C as lower and higher temperatures, respectively. At both T_ds, the sidewall-bottom step coverage (SC_8-b) was approximately 70%, while the sidewall step coverage (SC_sw) reached excellent values above 90%. It is suggested that low SC_s-b value was caused by crystallization of the PZT films at the bottom of the trench because underlayer of the film at this area was not SiO₂ but crystalline TiAlN. On the other hand, no significant composition fluctuation was observed along the depth direction of the sidewall. These results mean that the film deposited at 540°C had almost the same level in terms of thickness and composition conformality as that deposited at 450°C.