Kensuke Kageyama

Characterization of self-patterned SrBi2Ta2O9 thin films from photo-sensitive solutions

Abstract Self-patterned SrBi2Ta2O9 thin films were successfully fabricated from photo-sensitive solutions by means of UV irradiation through photo masks. After conventional baking and wet etching the films were annealed. The photo-sensitive SrBi2Ta2O9 solutions give high resolution negative-pattern of the mask image down to 1 μm line width by deep UV irradiation at 900 mJ/cm2. The capacitor characteristics of the 210 nm thick films fabricated on the Pt/Ti/SiO2/Si substrates by this process showed 2Pr values of 17 μC/cm2, 2Ec of 89 kV/cm, and leakage current densities of 5×10−9 A/cm2 at 5 V. The films showed no fatigue after 1×1011 switching cycles.

Evaluation of Self-Patterned PbZrxTi1-xO3 Thin Film from Photosensitive Solution

Micro-patterned PZT(20/80) films were fabricated on Pt/Ti/SiO2/Si substrate from a photosensitive solution by the sol-gel process. A coated film was exposed to UV rays (365 nm) at an intensity of 570 mJ/cm2 and developed with a 1:1 mixture of 2-methoxyethanol and isopropyl alcohol. The 170-nm-thick film with a smooth surface showed Pr of 31.9 µC/cm2 and Ec of 120.8 kV/cm. Films with smoother surface morphology and better electrical properties than conventional PZT films were obtained by this process.

Preparation of Self-Patterned SrBi 2 Ta 2 O 9 Thin Films from Photo-Sensitive Solutions

Photo-sensitive SrBi 2 Ta 2 O 9 (SBT) solutions were evaluated and the patterning process flow for SBT films using the solutions was optimized. By adding a soft-bake process before UVirradiation, self-patterned SBT films were successfully prepared from the solutions and the cross sectional shape of the patterned films was improved. The photo-sensitivity of the solutions was estimated to be 900 mJ/cm 2 . The photo-reaction in the precursor gel film formed from the solution was traced by measuring IR absorption spectra. The obtained films had excellent ferroelectric properties comparable to conventional SBT films.

Effect of Metallic Oxides Containing Composite Electrodes on Crystallization and Ferroelectric Properties of Pb(Zr0.52,Ti0.48)O3 Thin Films Deposited by the Sol-Gel Method

In order to suppress polarization fatigue and decrease the leakage current of the PZT capacitor, composite electrodes consisting of MO2 (RuOx or IrOx) as an effective diffusion barrier and considerably large amounts of Pt were deposited by magnetron co-sputtering to yield heterostructured PZT capacitors, Pt/(Pt+MO2)//PZT(52/48)//(Pt+MO2)/(Pt+M)/M/Pt/Ti(Ta)/SiO2/Si(1 0 0), and the crystallinity and the orientation, the morphology of the surface and the cross section, and the composition depth profile of the PZT capacitor were examined by XRD analysis, SEM and AES, respectively, and the ferroelectric properties were measured. The results indicated that by adjusting the distribution and composition of the RuO2 phase, the polarization loss of the PZT capacitor can be suppressed to as small as 5% after polarization reversals of 109 while maintaining the effective polarization dPr = Pr* − Pr^ at 15 μC/cm2. The suppression of the polarization fatigue was found more effective with (Pt+IrO2) electroding than (Pt+RuO2) electroding. The leakage current of the PZT capacitor electroded with (Pt+MO2) was a little larger than that of the PZT capacitor with Pt electrode. The possible reason was suggested.