Control of crystalline structure and ferroelectric properties of Pb(ZrxTi/sub 1-X/)O3 films by pulsed laser deposition
We have investigated Pb(Zr/sub X/Ti/sub 1-X/)O/sub 3/ (PZT) films on Pt/SiO/sub 2//Si substrates formed by pulsed laser deposition (PLD) and subsequent rapid thermal annealing (RTA) under various growth conditions. X-ray diffraction analysis revealed that preferentially [100]-oriented perovskite PZT films with trigonal structure were formed after RTA from as-deposited films which had consisted of small grains with pyroclore structure. The degree of [100]-orientation of the PZT film increased with the oxygen partial pressure during PLD. The capacitors made from these films showed higher remnant polarization than those from randomly oriented films.
Barrier layers for realization of high capacitance density in SrTiO3 thin‐film capacitor on silicon
High dielectric constant SrTiO3 thin films were sputter deposited on barrier layers/Si substrate to fabricate a capacitor for dynamic random access memories. Dielectric constant (er) values of 140–210 were achieved for the 150‐nm‐thick SrTiO3 films using a Pt/Ti or Pt/Ta double‐layer barrier. In the Pt(50 nm)/Ti(10 nm), Pt(50 nm)/Ti(50 nm), and Pt(50 nm)/Ta(10 nm) barrier, effective er decreased by annealing in the temperature range between 450 and 550 °C, where the interdiffusion of Pt and Si was confirmed by x‐ray diffraction analysis and cross‐sectional transmission electron microscopy. In the Pt(50 nm)/Ta barrier, increase of the Ta thickness from 10 to 50 nm brought out a remarkable improvement of endurance to high‐temperature annealing. That is, in the Pt(50 nm)/Ta(50 nm) barrier, large er value (∼200) was maintained even with annealing at up to 700 °C.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.