Joon Seop Sim

Ferroelectric and reliability properties of metal-organic chemical vapor deposited Pb(Zr0.15Ti0.85)O3 thin films grown in the self-regulation process window

Ferroelectric reliability of Pb(Zr0.15Ti0.85)O3 films grown by metal-organic chemical vapor deposition at 570°C on an Ir electrode in the self-regulation process window [constant Pb concentration irrespective of the precursor input ratio (Pb∕(Zr+Ti), PIR)] was studied. Although the Pb composition and crystallinity of the films grown under different PIR were almost identical, the film grown under a PIR which was near the center of the process window showed the best ferroelectric performance. X-ray photoelectron spectroscopy showed that the films grown at lower and higher PIR have residual ZrO2 and metallic Pb, respectively, which resulted in reduced remanent polarization and reliability.

Characteristics of Polycrystalline SrRuO3 Thin-Film Bottom Electrodes for Metallorganic Chemical-Vapor-Deposited Pb ( Zr0.2Ti0.8 ) O3 Thin Films

In situ and ex situ crystallized polycrystalline SrRuO 3 (SRO) thin-film electrodes are fabricated by dc magnetron sputtering at a substrate temperature of 550 and 350°C, respectively, followed by postannealing for application as bottom electrodes of metallorganic chemical-vapor-deposited Pb(Zr 0.2 Ti 0.8 )O 3 (PZT) thin films. The in situ crystallized SRO electrode shows a negligible change in film composition during the subsequent annealing and works as a good electrode for the ferroelectric PZT films. However, the ex situ crystallization by postannealing largely decreases the Ru content in the SRO film and consequently the PZT film grown on top has a poor ferroelectric performance. In addition, the Zr component in the PZT film initially reacts with the excessive SrO in the electrode, resulting in a deposition of PbTiO 3 at the initial stage of the PZT deposition which largely deteriorates the ferroelectric performance. Therefore, it is crucial to have in situ crystallized SRO for a reliable electrode of a PZT capacitor.

A study of liquid delivery MOCVD of lead oxide thin films on Pt and Ir substrates

Lead oxide thin films were deposited on Pt/SiO 2 /Si and Ir/IrC 2 /SiO 2 /Si substrates by liquid delivery metallorganic chemical vapor deposition (MOCVD) at substrate temperatures ranging from 475 to 525°C using a dome-typeCVD chamber in order to understand the MOCVD behavior of ferroelectric Pb(Zr,Ti)O 3 films. The precursor and oxidant were bis-tetramethylheptanedionato-Pb dissolved in ethylcyclohexane and O 2 , respectively. The lead oxide films were nicely grown on the Pt electrode irrespective of the deposition temperature. However, the film growth on the Ir electrode was hampered by the in situ oxidation of the Ir film when the growth temperature was above 500°C. The film grown at 525°C contained metallic Pb components which may largely degrade the electrical properties of the film. A smaller oxygen flow rate reduced the oxidation of the Ir film and enhanced the lead oxide film growth with a smaller content of metallic Pb. An interesting observation was that the reactively sputtered IrO x electrodes are reduced during the lead oxide CVD process and produced similar film growth behaviors as that on Ir electrodes.

Characterization of Pb x Pt y Alloy Formation on a Pt Substrate during Liquid-Delivery MOCVD of Pb ( Zr , Ti ) O3 Thin Films

Pb x Pt y alloy formation and its influence on Pb(Zr,Ti)O 3 (PZT) film growth during liquid-delivery metallorganic chemical vapor deposition (MOCVD) of ferroelectric PZT thin films on Pt electrodes are investigated. When an excessive amount of Pb precursor and a deficient amount of oxygen are supplied during MOCVD at temperatures near 550°C, Pb diffuses along the grain boundaries into the Pt substrate, causing the formation of an alloy layer. Compared to a thicker Pt electrode (150 nm), a thinner Pt substrate (50 nm) enhances the alloy layer formation due to the higher diffusion of Pb along the more abundant Pt grain boundaries. The alloy layer enhances the Pb incorporation into the PZT film and improves the crystallization of the PZT layer on top due to better structural compatibility between PZT and the alloy. When the deposition temperature is 570°C the alloy formation is initiated in the early stage of the film deposition but undergoes thermal decomposition in the later stage (> ∼ 15 min). Therefore, a constant Pb concentration is obtained after the initial decrease for a deposition period <15 min.

Investigation of the Deposition Behavior of a Lead Oxide Thin Film on Ir Substrates by Liquid Delivery Metallorganic Chemical Vapor Deposition

Lead oxide thin films were deposited on Ir/IrO 2 /SiO 2 /Si substrates by liquid delivery metalorganic chemical vapor deposition at 525 °C in order to understand its influence on Pb-based ferroelectric film growth. The Ir substrates were variously pretreated in situ to control the surface oxidation state. Fully oxidized lead oxide films were grown on a nonoxidized Ir or fully oxidized IrO 2 surface. The lead oxide film growth on partially oxidized IrO x (x < 2) was hampered resulting in metallic Pb incorporation which may largely degrade the electrical properties of the film. IrO x oxidizes quickly consuming the supplied oxygen.

Influence of the Pt Top Electrode Annealing Procedure on the Ferroelectric Property of MOCVD Pb ( Zr0.2Ti0.8 ) O3 Thin Films

The influence of the electron-beam-evaporated Pt top electrode annealing procedure on the ferroelectric performance of metalorganic chemical vapor-deposited (MOCVD) Pb(Zr 0.2 Ti 0.8 )O 3 thin films deposited on an Ir electrode was investigated. Although the top Pt electrode was fabricated at room temperature, an interfacial reaction already occurred resulting in a Pb x Pt y alloy formation. This interfacial reaction degraded the reliability (fatigue) of the ferroelectric capacitor. Conventional furnace annealing of the Pt top electrode at temperatures ranging from 200 to 600°C further degraded the ferroelectric performance. Rapid thermal annealing at 600°C successfully suppressed the interfacial reaction and largely improved the ferroelectric performance.