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The research of IC Cu metallization that Dr. Chang was involved with in
his early academic stage comprises the depositions of Cu and
low-dielectric-constant films. He developed an integrated
electrochemical process for the deposition of Cu films with much
improved electrical properties and step coverage, during which the
atomic-scale deposition mechanism and lattice correlation of Pd
catalysts and Cu nuclei was also examined. He further developed several
low-dielectric-constant materials for application to multilevel Cu
interconnects and investigated their physical, chemical and mechanical
properties. Moreover, the bonding structures at the interface of Cu and
dielectrics were studied to correlate the interface bonding with
interface adhesion and Cu electromigration as well as to evaluate the
mechanical/electrical reliability of Cu interconnect structure. In
recent years, Dr. Chang further attempted the fabrication of diffusion
barriers which located between Cu wires and dielectrics; thin layers of
Co-W-P and multi-component materials were prepared, and their thermal
stability and diffusion resistance were examined. Also, Cu(Re) alloy
films were also successfully deposited by an electrochemical route for
self-forming an ultrathin Re diffusion barrier layer of only a few
nanometers thick during low-temperature annealing at 400°C.
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Left to right: Cu/dielectric interface bonding, early-stage electromigration and Co-W-P film.
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Based on Dr. Chang’s
experience of electrochemical process, advanced oxide/metal
hetero-nanostructures for optoelectronics and catalysis applications
have been fabricated. He innovatively synthesized three-dimensional
network hetero-nanostructures of metal nanoparticle, ZnO nanorod or
Pd-Sn-Zn nanodendrite grafted TiO2 nanotube arrays, which presented a
higher photocatalytic activity and water splitting (hydrogen
generation) efficiency than conventional P25 TiO2 did. Related
experimental results have been published as a scientific paper in
Journal of Physical Chemistry C and two papers in Journal of Materials
Chemistry.
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Left to right: TiO2/Sn-Pd, TiO2/ZnO/Ag, and TiO2/Pd-Sn-Zn hetero-nanostructures.
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