The metalorganic chemical vapor deposition of very thin (<50 nm) Pb(Zr,Ti)O3 (PZT) thin films was performed for high density (>32 mega bit) ferroelectric memory devices. The growth temperatures were set between 450 and 530 °C to obtain a smooth surface morphology and prevent damage to the underlying reaction barrier layer. The average grain size of a 50-nm-thick film on a Pt electrode was about 34 nm with a size distribution (σ2) of 11 nm. These values are much smaller than the sol-gel-derived PZT films (55 and 25 nm, respectively). Very thin films with a thickness of approximately 30 nm were prepared at wafer temperatures ranging from 500 to 525 °C. Even with the very small thickness, the films showed good ferroelectric properties with a typical remanent polarization from 10 to 15 μC/cm2 and an extremely low coercive voltage of 0.3 V. However, the leakage current density was rather high resulting in nonsaturating polarization versus voltage curves. Even though good ferroelectric properties were obtained, the formation of PtxPby alloys on top of the Pt electrode was consistently observed. This precludes the reliable control of film composition and electrical performance. The adoption of an Ir electrode successfully eliminated intermetallic alloy formation and resulted in better and reproducible process control. A 50-nm-thick PZT film on an Ir/IrO2/SiO2/Si substrate also showed a reasonable ferroelectric performance.

The degradation behavior of integrated Pt/SrBi2Ta2O9/Pt capacitors caused by hydrogen impregnation during the spin-on glass (SOG)-based intermetal dielectric (IMD) process was investigated. SOG was tested as an IMD since it offers better planarity for multilevel metallization processes compared to other SiO2 deposition methods. It was found that the SOG itself does not degrade the ferroelectric performance. Deposition of an under-layer of SiOxNy by plasma-enhanced chemical vapor deposition (PECVD) using SiH4 + N2O + N2 source gases and a SiO2?x capping layer by another PECVD process using SiH4 + N2O source gases produced hydrogen as a reaction by-product. The hydrogen diffused into the SBT layer and degraded the ferroelectric performance during subsequent annealing cycles. A very thin (10 nm) Al2O3 layer grown by atomic layer deposition before the IMD process successfully blocked the impregnation of the hydrogen. Therefore, excellent ferroelectric performance of the SBT capacitors were maintained after the multilevel metallization process as well as passivation. The adoption of SOG in the IMD process greatly improved the surface flatness of the wafer resulting in a higher capacitor yield with very good uniformity in ferroelectric properties over the 8-in.-diameter wafer.

Strip-shaped diamond-tip field emitter array was fabricated by using the transfer mold technique. The sharp turn-on characteristic was observed from the current-voltage measurement of the fabricated diamond-tip field emitter array. The turn-on characteristic of the diamond-tip field emitter array was compared with that of a flat diamond film. High emission current density was obtained from the diamond-tip field emitter array. The threshold voltage of the diamond-tip field emitter array was lower than that of a flat diamond film.