Abstract: Copper and aluminium laminates are alternately stacked and sintered by PAS at T=743K
under different pressures. Microstructure of the cross section of the samples are characterized and
analyzed by means of Optical Microscope (OM), Scanning Electron Microscope (SEM) and Energy
Dispersive Spectroscope (EDS). The results show that the initial Al layers melted and produced
Al-rich liquid phase during sintering at T=743K, and the Al-rich liquid phase ultimately formed
complicated L layer consisting of the saturated solid solution phase Al(Cu) and the two-phase
Al2Cu-Al(Cu) eutectic when the laminates was cooled to room-temperature. The interface between
the Cu layer the L layer consists of solid solution(α), Al2Cu3(δ)and Al2Cu(θ) layer. Voids and cracks
are not found at or near the interfaces of the polished samples. The most important effect of the
pressure is to change the shapes of interfaces, which almost smooth at 10MPa but flexual at 50MPa.
Abstract: Chemical mechanical polishing (CMP) has been used as planarization process in the
fabrication of semiconductor devices. The CMP process is required to planarize the overburden film
in an interconnect process by high relative velocity between head and platen, high pressure of head
and chemical effects of an aqueous slurry. But, a variety of defects such as dishing, delamination and
metal layer peering are caused by CMP factors such as high pressure, pad bending and strong
chemical effect. The electrical energy of the electro-chemical mechanical planarization (ECMP)
dissolves copper (Cu) solid into copper ions electrochemically in an aqueous electrolyte. The
dissolved copper complex layer or passivation layer is removed by the mechanical abrasions of
polishing pad and abrasive. Therefore the ECMP process realizes low pressure processing of soft
metals to reduce defects comparing to traditional CMP process. But, if projected metal patterns were
removed and not remained on whole wafer surface in final processing stage, Cu layer could not be
removed by ECMP process.
The two-step process consists of the ECMP and the conventional CMP used in micro patterned Cu
wafers. First, the ECMP process removed several tens 'm of bulk copper on Cu patterned wafer
within shorter process time than the Cu CMP. Next, residual Cu layer was completely removed by the
Cu CMP under low pressure. Total time and process defects are extremely reduced by the two-step
Abstract: In this paper, an efficient optimum material design technique is introduced for hybrid
designing of dual-phase heat-resisting functionally graded composites. The graded region is divided
into a finite number of homogeneous material layers in order to reduce the total design variables. The
discrete optimum volume fractions are sought by making use of the interior penalty method and the
finite difference sensitivity scheme. A linear interpolation technique is adopted to make the final
optimum volume fraction distribution be continuous. The validity of the proposed optimization
technique is examined through the illustrative numerical experiment.
Abstract: The Cu20W70Cr10 composites were fabricated by two methods which are the
conventional powder metallurgy, and mechanical alloying to prepare WCr compound powders,
followed by sintering and infiltration. The erosion behavior of CuWCr composites under
breakdown was investigated. The surfaces of the composites before and after erosion and the
mechanism of arc erosion were studied by scanning electron microscopy. The results show that the
CuWCr composites prepared by mechanical alloying have superfine microstructure, uniform
composition and high density, thus result in good characteristics of diffusing arcs and arc eroding
endurance. Arc erosion zones are dispersive and uniform on the surfaces with some flat eroding pits.
The Cu20W70Cr10 composites have excellent electrical properties such as high breakdown
voltage, low chopping current and long arc life.
Abstract: Lithium niobate (LN, LiNbO3) is a kind of artificial crystal with piezoelectricity,
pyroelectricity and ferroelectricity, which has been widely used in electron components. The large
difference in thermal expansion coefficients between Si and LN causes a serious thermal stress during
the thermal-pressure bonding process. Therefore room temperature bonding would be the best
candidate to make strong and stress-free interface between Si and LN. However, room temperature
bonding requires lower surface roughness (Ra<2nm) and lower defects on the LN wafer surface than
those of thermal bonding. Chemical mechanical polishing (CMP) process helps LN to obtain the high
quality surface and thin wafer suited in room temperature bonding. The LN wafer was polished using
colloidal silica slurry, resulting in high material removal rate (MRR) and fine surface quality under
the condition of low pH, high abrasive concentration and low flow rate. The polishing mechanism of
LN was discussed by mechanical, chemical and thermal analysis.
Abstract: Silicon carbide (SiC) is a wide band gap semiconductor being developed for high
temperature, high power, and high frequency device applications. For the manufacturing of SiC to
semiconductor substrate, many researchers have studied on the subject of SiC polishing. However,
SiC faces many challenges for wafer preparation prior to epitaxial growth due to its high hardness and
remarkable chemical inertness. A smooth and defect free substrate surface is important for obtaining
good epitaxial layers. Therefore, hybrid process, chemical mechanical polishing (CMP) has been
proposed to achieve epi-ready surface.
In this paper, the material removal rate (MRR) is investigated to recognize how long the CMP
process continues to remove a damaged layer by mechanical polishing using 100 nm sized diamond,
and the authors tried to find the dependency of mechanical factors such as pressure, velocity and
abrasive concentration using single abrasive slurry (SAS). Especially, the authors tried to get an
epi-ready surface with mixed abrasive slurry (MAS). The addition of the 25nm sized diamond in
MAS provided strong synergy between mechanical and chemical effects resulting in low subsurface
damage. Through experiments with SAS and MAS, it was found that chemical effect (KOH based)
was essential and atomic-bit mechanical removal was efficient to remove residual scratches in MAS.
This paper concluded that SiC CMP mechanism was quite different from that of relatively soft
material to achieve both of high quality surface and MRR.
Abstract: The SBT(SrBi2Ta2O9) thin films with Bi2O3 buffer layer were deposited on Pt/Ti/SiO2/Si
substrate by R.F. magnetron sputtering method in order to improve the ferroelectric characteristics. In
SBT thin films, the deficiency of bismuth due to its volatility during the process results in an obvious
non stoichiometry of the films and the presence of secondary phases. Bi2O3 buffer layer was found to
be effective to achieve lower temperature crystallization and improve ferroelectric properties of SBT
thin films. Ferroelectric properties and crystallinities of SBT thin films with various substrate
temperature of Bi2O3 buffer layer were observed, using X-Ray Diffraction (XRD), Precision LC
(Radient Technologies. Inc.) and GDS (glow discharge spectrometer).
Abstract: Ti-Al-Si-N and Ti-Al-N coatings were deposited on WC-Co substrates by a DC magnetron
sputtering method. The oxidation behavior of two kinds of Ti0.75Al0.25N and Ti0.69Al0.23Si0.08N
coatings were comparatively investigated by XRD patterns and GDOES depth profiles. Si addition of
8 at.% into Ti-Al-N film modified its microstructure to a fine composite comprising, Ti-Al-N
crystallites and amorphous Si3N4, and to a smoother surface morphology. While the solid solution
Ti0.75Al0.25N film had superior oxidation resistance up to around 700°C, the composite Ti-Al-Si-N
film showed further enhanced oxidation resistance. Both Al2O3 and SiO2 layers played roles as a
barrier against oxygen diffusion for the quaternary Ti-Al-Si-N film, whereas only the Al2O3 oxide
layer formed at surface did a role for the Ti-Al-N film. The cutting performances of two coated
carbide ball-end mills were evaluated by cutting of AISI D2 cold-worked die steel (60 HRC) under
high-speed cutting condition. The tool wear and cutting temperature are discussed along with coating
Abstract: Pseudoelastic behavior of Ti-xNb-yGe alloys, where x=22~28at.% and y=0.5~2.0at.%, was
investigated by controlling martensite start temperature and phase stability of β phase. Cyclic tensile
test was carried out to display a pseudoelastic behavior at room temperature. Determination of the
martensitic transformation temperature (Ms and Mf) and reverse transformation temperature (As and
Af) of the alloys were carried out using differential scanning calorimetry (DSC). Optical microscopy,
X-ray diffraction (XRD) and DSC results revealed that Ge is stronger stabilizer of β-phase than Nb.
XRD spectra of the deformed specimens confirmed that the crystal structure of stress-induced
martensite phase is orthorhombic structured α″. It is concluded that pseudoelasticity of the present
Ti-Nb-Ge alloy is closely associated with phase stability, and metastable β-phase is better to increase
pseudoelasticity than stable one.
Abstract: This study is to examine wear properties of Ti-Nb-Si alloys under dry condition and to
investigate its wear mechanism. A ball-on-disc type wear testing machine was used to evaluate the
wear factor. Optical microstructure observation revealed that the microstructure appeared to mixture
appearance consisting of β phase and small amount of α″ martensite phase. Yield strength increased
with increasing Nb and Si content. Wear resistance of the present alloy are strongly dependent upon
yield strength and elastic modulus. Energy dispersive spectroscopy (EDS) and X-ray diffraction
(XRD) analysis confirmed the tribo-chemical reaction between the alumina ball and the present alloy
occurs due to decomposition of alumina to aluminum.