Solid State Phenomena Vols. 124-126

Abstract: One of key processes in tungsten (W) CMP is to remove slurry particles inside W plug after CMP. In general, HF cleaning is well known to remove the slurry residue particles in W plugs. HF chemistry lifts off the particles by etching the plug during scrubbing and effectively removes particles. It is sometimes impossible to apply HF chemisty on W plug due to the degradation of electrical characteristics of a device. In this paper, a post W CMP cleaning process is proposed to remove residue particles without applying HF chemistry. After W CMP, recessed plugs are created, therefore they easily trap slurry particles during CMP process. These particles in recessed plug are not easy to remove by brush scrubbing when NH4OH chemistry is used for the cleaning because the brush surface can not reach the recessed area of plugs. Buffing with oxide slurry was followed by W CMP due to its high selectivity to W. The buffing polishes only oxide slightly which creates higher plug profiles than surrounding oxide. Higher profiles make the brush contact much more effectively and result in a similar particle removal efficiency even in NH4OH cleaning to that in HF brush scrubbing.

Abstract: This paper describes a micromachined piezoelectric bimorph microphone, which is built on a low stress Parylene diaphragm with high quality ZnO films. The ZnO thin film has fine grain with the average grain size less than 1
and the grain orientation is perpendicular to the substrate. The highest sensitivity of piezoelectric bimorph microphone fabricated in this study is about 0.74 mV/Pa, which is twice higher than that of an individual segmented electrode. Based upon the experimental results, we proposed the equivalent electrical circuit model of piezoelectric bimorph microphone.

Abstract: PDMS(polydimethylsiloxane) is a flexible and biocompatible material and is widely used in bio- or medical-related fields. Recently, PDMS has been used as a substrate of implantable electrodes but has exhibited limits in stable metal layer deposition and patterning. In this paper, we have developed processes for both the stable metallization of PDMS surface and the selective patterning of conductive elements. The surface treatment via the oxygen plasma ions significantly affects the adhesion of metal layers to the PDMS surface, while the other factors exhibited no significant relations. On the basis of our procedure resulted in the effective production of the stable and fine (line width: 20
) electrode patterns on the PDMS substrate. Finally, we fabricated PDMS-based flexible and implantable micro electrode for the subretinal prosthesis.

Abstract: Lead zinc niobate (PZN) added lead zirconate titanate (PZT) thick films with thickness of 5~10 μm were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0, 20 and 40 %. The as deposited film had fairly dense microstructure without any crack, and showed only a perovskite single phase formed with nano-sized grains. The as-deposited films on silicon were annealed at temperatures of 700oC, and the films deposited on sapphire were annealed at 900oC in the electrical furnace. The effects of PZN addition on the microstructural evolution were observed using FE-SEM and HR-TEM, and dielectric and ferroelectric properties of the films were characterized using impedance analyzer and Sawyer-Tower circuit, respectively. The PZN added PZT film showed poor electrical properties than pure PZT film when the films were coated on silicon substrate and annealed at 700oC, on the other hand, the PZN added PZT film showed higher remanent polarization and dielectric constant values then pure PZT film when the films were coated on sapphire and annealed at 900oC. The ferroelectric and dielectric characteristics of 20% PZN added PZT films annealed at 900oC were comparable with the values obtained from bulk ceramic specimen with same composition sintered at 1200oC.

Abstract: For low temperature cofired ceramic (LTCC) materials to achieve increase functionality, as well as low loss and moderate dielectric constant, it is essential to achieve the temperature stability of the resonant frequency. Facing several empirical approaches toward tuning the temperature coefficient of the resonant frequency (τf) through the formation of mixtures or a solid-solution between the two end members with opposite signs of τf, which result in higher dielectric loss, we took a closer look at the texture engineering that determines the anisotropic dielectric properties in barium niobate ceramics. We demonstrate the advantage of texture engineering for microwave dielectric properties including temperature stability by control of crystallographic orientation. Also, the monoclinic rare earth niobates are investigated as novel microwave dielectric materials. Furthermore, the stable τf of the rare earth niobates could be efficiently explained through the ferroelastic domain engineering related to phase transformation.

Abstract: To investigate the anisotropic dielectric properties of layer-structured bismuth-based ferroelectrics along different crystal directions, we fabricate devices along different crystal orientations using highly c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films on (001) LaAlO3 (LAO) substrates. Experimental results have shown that the dielectric properties of the BLT films are highly anisotropic along different crystal directions. The dielectric constants (1MHz at 300 K) are 358 and 160 along [100] and [110], respectively. Dielectric nonlinearity is also detected along these crystal directions. On the other hand, a much smaller dielectric constant and no detectable dielectric nonlinearity in a field range of 0-200 kV/cm are observed for films along [001] when c-axis oriented SRO is used as the bottom electrode.

Abstract: Epitaxial Pt films were grown on γ-Al2O3/Si (111) substrate by RF-magnetron sputtering. The γ-Al2O3 buffer layers were grown epitaxially using molecular beam epitaxy. The films were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) and atomic force microscopy (AFM). The results of XRD showed that high-quality Pt films were obtained at around 560°C. In addition, the Pt films exhibited a very smooth surface with the root-mean-square (rms) surface roughness is about 0.4 nm.

Abstract: The porous SSQ (silsesquioxane) films were prepared by using alkoxy silyl substituted cyclodextrin (sCD) and methyl substituted cyclodextrin (tCD) based porogen. The mechanical and electrical properties of these deposited films were investigated for the applications as low dielectric materials. The mechanical properties of porous film by using sCD are worse than those by using tCD due to its high pore interconnection length. sCD templated porous films show almost constant pore diameter as a function of porogen concentration due to strong linear polymerization of the sCD molecules through polycondensation.

Abstract: Indium tin oxide (ITO) used in many applications such as electronic and optical devices were deposited on the soda lime glass substrate by an electron beam evaporation techniques from a mixture of 90wt% of In2O3 and 10wt% of SnO2. The physical, electrical and optical properties of the ITO films were determined as a function of substrate temperature. The films deposited at 200
showed optimum properties with a strong diffraction peak having a preferred orientation along the [111] direction. Experimental results showed that sheet resistance and transmittance of the ITO film increased with an increase in substrate temperature. Surface roughness increased slightly as a function of substrate temperature because of grain growth.