Hiroto Uchida

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.

Properties of a new organo silver compound for MOCVD

Abstract Trans-bis(trimethylsilyl)ethene(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)Ag(I), (BTMSE)Ag(hfac) was found to be a very promising compound for CVD Ag wiring. It is a solid at r.t. (m.p. 70°C), has a vapor pressure (10−3 Torr at r.t.) and high thermal stability, and can be used as a precursor for MOCVD. Thermal and laser CVD silver films were grown on TiN Si(100) from (BTMSE)Ag(hfac) in a quartz vacuum chamber, using thermal activation by an electric heater or photo activation through a quartz window with an excimer laser (XeCl, 308 nm). The chamber pressure was varied from 2 to 30 Torr. The evaporation temperature was kept at 80°C. Ar gas was used as the carrier with a flow rate in the evaporation cylinder varying from 50 to 200 ccm. A growth rate of 3 nm/min was achieved at 200°C, an evaporation temperature of 80°C, an argon flow rate of 100 ccm and a chamber pressure of 10 Torr. Resistivities were of the order of about 10−3 cm depending on the film morphology. With laser CVD, a growth rate of 3 nm/min was achieved by laser activation at 80°C, an evaporation temperature of 120°C, an argon flow rate of 100 ccm and a chamber pressure of 10 Torr. Resistivities were of the order of about 10−6 Ω cm depending on the film morphology. The laser CVD results were far better than the thermal CVD ones. The film morphology was finer and more evenly distributed with a faster growth rate at much lower temperatures.

Properties of A New Liquid Organo Gold Compound for MOCVD

Dimethyl(1,1,1,5,5,5-hexafluoroaminopenten-2-onato)Au(III), DMAu(hfap) was found to be very promising compound for CVD Au wiring. It is liquid at r.t. and has high vapor pressure (0.5 Torr at r.t.) and high thermal stability (dec.t. 171°C, δE=25.4Kcal/mol) and can be used as a precursor for MOCVD. CVD gold films were grown on Si(100) from DMAu(hfap) in a quartz vacuum chamber, using thermal activation by an electric heater or photo activation through quartz windows by excimer lasers(XeC1 308nm). A growth rate of 10 nm/min was achieved by thermal activation at 250 °C, (evaporation temperature of 30 °C, H2 flow rate at 100 sccm and chamber pressure of 30 Torr). Resistivities ranged between 2.8 and 5.lμΩ-cm, depending on the film morphology. The growth rate of laser CVD gold films had the tendency of increasing with decreasing the substrate temperature. This phenomenon indicates that photolysis of adsorbed species on the substrate plays an important role in film growth by laser CVD.

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.

Crystallographic orientation control for ferroelectric SBT and SBTN thin films from photosensitive mod solutions

Abstract SBT and SBTN thin film capacitors on Pt/Ti/SiO2/Si have been fabricated from photosensitive MOD solutions with the composition Sr0.8Bi2.35Ta2−xNbx (x=0.0−0.8). Films prepared by a conventional spin-on and anneal process are essentially randomly oriented, while films that received UV radiation before annealing exhibit c-axis orientation. The degree of c-axis orientation is enhanced by short pyrolysis times. Ferroelectric properties were characterized by hysteresis and pulse measurements. A higher Qsw and lower V(90%) were measured for films with random orientation in comparison with films having the same composition but c-axis preferred oriented. The c-axis orientation can be controlled by substrate pre-annealing. UV irradiated SBT and SBTN films with random orientation can be prepared on the substrates that are pre-annealed at 650°C.