Ti Buffer Layer Research Articles

Effects of Titanium Buffer Layer on Lead-Zirconate-Titanate Crystallization Processes in Sol-Gel Deposition Technique

Effects of the Ti buffer layer on crystallization processes of lead-zirconate-titanate (PZT) films by the sol-gel deposition technique were investigated. The Ti buffer layer was deposited on a Pt/TiN/SiO2/Si substrate by electron beam evaporation at the back-pressure of 1×10-11 Torr. Homogeneous crystalline PZT film of perovskite structure with fine grains were successfully obtained on the substrate with a Ti buffer layer. In contrast, a rosette-structure film which consists of large grains surrounded by a second phase was formed on a pure Pt surface. Ti existing at the interface between Pt and PZT acts as nuclei, and affects the growth of fine grains. Furthermore, leakage current density was drastically reduced from 5×10-5 A/cm2 to 6×10-9 A/cm2 at 4 V for 200-nm-thick film formed on a substrate with a buffer layer. Crystalline orientations and microstructures of PZT films were strongly dependent on the equivalent thickness of the buffer layer and there was an optimum thickness. When the equivalent thickness of the buffer layer was 2 nm, PZT showed <111>-preferred orientation and a homogeneous film structure with fine grains on the <111>-oriented Pt/SiO2/Si substrate.

Behavior of TiN and Ti Barrier Metals in Al‐Barrier‐Al Via Hole Metallization

The behavior of and Ti barrier metals in Al‐barrier‐Al via structures was investigated. When a reactive‐sputtered film is deposited onto an Al‐1 weight percent (w/o) Si‐0.5 w/o Cu surface, is formed at the interface due to the reaction of to Al, and causes an increase in via contact resistance. To suppress the increase in via contact resistance, it is crucial to interpose a Ti buffer layer at the interface. The via contact resistance of the structure increases at annealing temperatures over 450°C, since is formed at both the and interfaces. The via contact structure presents a specific low resistance after annealing above 450°C, is formed at both the Al/Ti and Ti/Al interfaces. Further, the layer can improve the electromigration performance of the interconnection which consists of a structure. The electromigration performance for various via structures also was investigated. Al/Ti/Al and via contact structures tend to increase the chain resistance before via open failure, where the dominant mechanism is the void formation originating from the migration of Al atoms in the vias rather than the via lift‐off mode. This means that Al atoms migrate easier on a layer than on a Ti layer. As a result, an Al/Ti/Al via structure is better for electromigration performance.

Roles of Buffer Layers in Epitaxial Growth of SrTiO3 Films on Silicon Substrates

Heteroepitaxial growth of SrTiO3 (STO) films with and without buffer layers on Si(100) and (111) substrates has been conducted by a focused electron beam evaporation method. It has been found that thin metallic layers such as Ti and Sr are effective for improving the quality of overgrown STO films, which is probably due to the fact that the metallic layers deoxidize the surface SiO2 layers on Si substrates. It has also been found that a Sr buffer layer is effective for obtaining fairly good epitaxial films on both Si(100) and (111) substrates, while a Ti buffer layer is effective for obtaining good electrical properties of the film and interface.

Microstructural changes of Pt/Ti electrodes in an oxygen ambient

The stability of bottom electrodes during annealing in oxidation environments is crucial for the fabrication of ferroelectric capacitors. The Pt/Ti bilayer has received attention as a promising electrode for Si-based devices. The Ti buffer layer is necessary not only to improve the adhesion of Pt to dielectrics but also to prevent the formation of Pt silicides at high temperatures. When the Pt/Ti electrodes are exposed to O2 atmosphere during heat treatment, the oxidation induced diffusion of Ti into Pt and the oxidation of Ti are observed. In spite of previous researches, the microstructural features of the Pt/Ti bilayers in oxygen ambients have not been cleared up yet. In this study, combined techniques of transmission electron microcopy(TEM), scanning electron nucroscopy(SEM), and Auger electron spectroscopy(AES) have been applied to clarify the correlation between the interdiffusion of Pt/Ti/O and the microstructural evolution.The chosen system was Pt/Ti/SiO2/Si. The electrode of 80 nm thick Pt was dc-sputter deposited on the 70 nm thick Ti adhesion layer. The Si substrate wafers were covered with 750 nm thick thermally grown oxides. Heat treatments at various temperatures were performed in an oxygen ambient for 30 min.

Magnetoresistance and Preferred Orientation in Fe–Mn/Ni–Fe/Cu/Ni–Fe Sandwiches with Various Buffer Layer Materials

Magnetoresistance effects and film structures have been investigated in [Fe–Mn/Ni–Fe/Cu/Ni–Fe/buffer layer/Si] sandwiches with various buffer layer materials. The sandwich with Nb, Ta, Ti, Zr or Hf buffer layer has strong (111) texture. Cu, Ag, Au and Cr buffer layers do not cause strong (111) texture. When the sandwich has strong (111) texture, the Ni–Fe layer neighboring the Fe–Mn antiferromagnetic layer is strongly exchange-biased by the Fe–Mn layer, and thus the sandwich shows a high magnetoresistance ratio.