Properties Of Yttria-stabilized Zirconia Thin Films Research Articles

Direct observation of leakage currents in a metal–insulator–metal capacitor using in situ transmission electron microscopy

With the acceleration of the scaling down of integrated circuits, it has become very challenging to fabricate a metal–insulator–metal (MIM) capacitor with a high capacitance density and low leakage current for nanoscale dynamic random access memory. Yttria-stabilized-zirconia (YSZ) thin films, one of the insulators in the constitution of MIM capacitors, have been reported to have various crystal structures from the monoclinic phase to the cubic phase according to different Y doping levels. The electrical characteristics depend on the crystal structure of the YSZ thin film. Here, we report the local crystallization of YSZ thin films via Joule heating and the leakage current induced during in situ transmission electron microscopy biasing tests. We studied the crystallization process and the increase in the leakage current using experimental and simulation results. It is important to understand the relationship between the crystallinity and electrical properties of YSZ thin films in MIM capacitors.

Structural and optical properties of YSZ thin films grown by PLD technique

We report on the structural and optical properties of yttria stabilized zirconia (YSZ) thin films grown by pulsed laser deposition (PLD) technique and in situ crystallized at different substrate temperatures ( T s = 400 °C, 500 °C and 600 °C). Yttria-stabilized zirconia target of ∼1 in. diameter (∼95% density) was fabricated by solid state reaction method for thin film deposition by PLD. The YSZ thin films were grown on an optically polished quartz substrates and the deposition time was 30 min for all the films. XRD analysis shows cubic crystalline phase of YSZ films with preferred orientation along 〈1 1 1〉. The surface roughness was determined by AFM for the films deposited at different substrate temperatures. The nano-sized surface roughness is found to increase with the increase of deposition temperatures. For the optical analysis, a UV–vis–NIR spectrophotometer was used and the optical band gap of ∼5.7 eV was calculated from transmittance curves.

Electrical Properties of YSZ Thin Films Deposited on Nanoporous Substrates

Thin YSZ (yttria stabilized zirconia) films having sub-micrometer thickness without gas leakage were successfully deposited on anodic nanoporous alumina substrates for low-temperature SOFCs application. By oxidation of metal thin films deposited onto the nanoporous substrates with pore size of 20 nm - 200 nm using DC magnetron sputtering at room temperature, YSZ thin films with thickness of about 30 nm - 300 nm were obtained. During oxidation at high temperature, the metal films were successfully transformed into defect-free oxide thin films and volume expansion induced from oxidation of metal resulted in dense thin films that are free from hydrogen permeation. Conductivity of YSZ thin films with different compositions could be measured at room temperature.