Soun-Young Lee

Characterization of a modified Bosch-type process for silicon mold fabrication

We present the results of our development of a deep silicon etching technique, the modified Bosch-type process. Its feasibility was also investigated. This modified Bosch-type process is based on the well known Bosch-type process, but our modified Bosch-type process consists of the etching/passivating time, process transition step, and ion energy control. This modified Bosch-type process has been characterized with respect to ion energy, substrate temperature, and feature size. We found that the etching and deposition characteristics of passivating film were closely related to the resulting deep silicon etch profile. Up to a 40–50 μm deep silicon structure with vertical and positively sloped profiles was realized by the modified Bosch-type process, depending on a few parameters. In this work, this modified Bosch-type process was applied to silicon mold fabrication used for a structuring microarray and optical power splitter. Replication results confirm that this process is promising for achieving high-yie...

Improvement of pulse diagnostic apparatus with array sensor of magnetic tunneling junctions

To obtain the spatial feature of arterial pulse, a spatial pulse diagnostic apparatus was designed using a two-dimensional magnetoresistive sensor array. The magnetic-field distribution for the magnet array was simulated using the finite-element method. The field distribution of parallel magnet arrays was observed to be more sensitive and uniform than that of the perpendicular ones. Moreover, the spatial displacements of the magnet array coincided with the output signal of the magnetic tunneling junction sensor array.

Epitaxial C49–TiSi2 phase formation on the silicon (100)

The crystallographic characteristics of an epitaxial C49–TiSi2 island formed on the Si (100) substrate were investigated by high-resolution transmission electron microscopy (HRTEM). The analysis results clearly showed that the optimum epitaxial relationship between the C49–TiSi2 phase and the Si substrate is [001]C49//[011]Si and (010)C49//(100)Si. We found that the interfacial energy at the C49–TiSi2/Si interface is relaxed by the formation of misfit dislocations and/or atomic steps, and consequently the epitaxial C49 phase is thermally stable so it is not transformed to the C54 phase even after high-temperature annealing above 900 °C. Further, the mechanism on the formation of the epitaxial C49 phase on the Si substrate and the atomic arrangement of stacking faults lying on the C49 (020) plane are discussed through the analysis of HRTEM images.

Fabrication and Characterization of Ru Thin Films Prepared by Liquid Delivery Metal-Organic Chemical Vapor Deposition

Ruthenium thin film was obtained by the liquid delivery metal organic chemical vapor deposition method using a new Ru(C8H13O2)3 precursor for the advanced capacitor electrode in Gbit-scale dynamic random access memory. Deposition was done on a TiN barrier layer in the range of 250–400°C. The thin film characterization was performed in terms of the resistivity, change of crystal structure, surface morphology, microstructure and film purity. The resistivity depended on the impurity, grain shape and crystalline structure of the film. The minimum resistivity of 13.9 µΩcm was obtained at 400°C. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that the RuO2 phase and the silicidation are not observed and are independent of the deposition temperature. The carbon and hydrogen contaminants in the Ru film were shown to disturb the crystal preferred orientation growth. The Ru film was found to grow perpendicular to the substrate and to be the columnar structure.

Influence of Ar+ ion bombardment on the chemical states of SrBi2Ta2O9 thin films fabricated by metalorganic decomposition

The SrBi2Ta2O9 (SBT) films studied for this report were prepared by metalorganic decomposition. The SBT thin film, which belongs to a Bi-layered perovskite structure where double Ta–O octahedron layers are sandwiched between (Bi2O2)2+ layers, was analyzed to characterize chemical states using x-ray photoelectron spectroscopy during depth-profiling analysis. When sputter etching was performed on the SBT film by Ar+ ion bombardment, the chemical states of constituents in the SBT film were changed as a function of the applied Ar+ ion-beam energy. Among the constituents of the SBT film, the Sr 3d peak was changed slightly by the change of Ar+ ion-beam energies. On the other hand, the changes of Ta 4f and Bi 4f peaks obviously depended on the applied Ar+ ion-beam energies. In particular, the Bi 4f peak changed dramatically from Bi–O states to Bi metallic states by the lower Ar+ ion-beam energies than in the cases of Sr and Ta. This change of chemical states of the SBT film resulted from the preferential sputte...

Transmission Electron Microscopy Study by Chemical Delineation in Si Devices

Transmission electron microscopy for a specimen prepared by the chemical delineation technique in Si devices was carried out in order to investigate the dopant profiles of ultra-shallow junctions in various regions. The results demonstrate that the two-dimensional dopant concentration of the junctions can be delineated down to a level of ~2.0×1017 cm-3 with a differentiation of As and P dopant profiles, and can be quantitatively evaluated by comparing the observed and simulated junction profiles. Furthermore, the morphology of metastable polysilicon formed by granulating the polysilicon surface and the thickness of the SiO2–Si3N4–SiO2 dielectric film were clearly observed by stripping the filled polysilicon by the delineation technique.

Studies on the interfacial and crystallographic characteristics of Al2O3∕SiO2∕Si and ZrO2∕SiO2∕Si stacks

Interfacial and crystallographic characteristics of the Al2O3 and ZrO2 dielectric films prepared by the atomic layer chemical vapor deposition on the Si substrate were investigated at the atomic scale using the high-resolution transmission electron microscopy and the electron energy-loss spectroscopy/energy dispersive x-ray spectroscopy coupled with a field-emussion (scanning) transmission electron microscope. In the Al2O3∕SiO2∕Si stack, we could observe two interfacial layers between the Al2O3 film and the Si substrate, and identify these as an Al-rich (Al, Si)O and a Si-rich (Al, Si)O mixed layer, respectively. In the ZrO2∕SiO2∕Si stack, we could detect Zr atoms at the upper and bottom interfaces of the SiO2 film, and observe a (Zr, Si)O mixed layer at the ZrO2∕SiO2 interface. After annealing at 800°C, the crystal system of the Al2O3 film was assumed to be either the cubic (Fd3m) or the tetragonal (P4¯m2), whereas the ZrO2 film exhibited a mixed structure of the tetragonal (P4¯m2) and the monoclinic (P2...

Nanoscale analysis on interfacial reactions in Al–Si–Cu alloys and Ti underlayer films

Solid-phase reactions at the interface between sputtered Al–Si–Cu alloys and Ti films were investigated at the atomic scale by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy (EDS) coupled with a field-emission (scanning) transmission electron microscope. The analysis results showed that the interface is composed of an amorphous-like Ti–Si layer, an intermediate-crystalline layer, and a Si-dissolved TiAl3 layer containing dissolved Si TiAl3 with a crystallographic relationship with the Al film. The nanometer-scaled interlayers effectively play a role as a barrier suppressing the interdiffusion reaction of Al and Ti during annealing treatment. Further, the quantitative composition of the interlayers was revealed by the analysis of the intensity profiles obtained from EDS elemental maps.

Characterization on microstructures of tungsten/barrier metals (TiN,WNx)/silicon multilayer films

Microstructures of W/barrier metals (TiN,WNx)/Si multilayer films followed by heat treatment were precisely investigated by x-ray diffraction and high-resolution transmission electron microscopy. The analysis results showed that in the W/TiN/Si stacked film having the W (110) and (200) preferred orientations, the TiN film itself plays a role as a barrier for the reaction of W and Si, whereas in the case of the WNx barrier having the W (110) one, the amorphous SixNy layer with a thickness of a few nanometers works effectively as a barrier, which was formed during the deposition and denudation process of the WNx film. Furthermore, the nanometer-scaled interfacial reaction in the multilayer films was clearly investigated by x-ray photoelectron spectroscopy coupled with chemical etching and an energy-filtered elemental mapping technique. Based on the results, effects of barrier metals on the W preferred orientation and the interfacial reaction were crystallographically and thermodynamically discussed.

Fabrication of high precision demultiplexer using embossing technique with thermal curable polymers

Photonic devices based on polymer materials have been fabricated mainly by using conventional lithography and etch processes. However, the fabrication method through these processes is complex and expensive. We fabricated 1310∕1550nm demultiplexer using an embossing technique, which was able to reduce the fabrication cost. The mold is an elastomeric polydimethylsiloxane (PDMS) and resists used as the core and the cladding layers are ZP 51 (ChemOptics) and ZP 49 (ChemOptics), respectively, which are thermal curable polymers. The fabrication process is summarized as follows: (1) manufacturing the photoresist master by lithography process, (2) forming the PDMS mold from the master, and (3) replicating the device using the mold. There is no observation of any noticeable pattern difference between the master and the replica in microscaled dimension. In this work, we also investigated the durability of a PDMS mold for mass production and successfully fabricated the 50th replica with the same mold. The replicate...