• Ceramist
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• v.22 no.1
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• pp.36-55
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• 2019

Atomically thin two-dimensional (2D) nanomaterials, including transition metal dichalcogenides (TMDs), graphene, boron nitride, and black phosphorus, have opened up new opportunities for the next generation optoelectronics owing to their unique properties such as high absorbance coefficient, high carrier mobility, tunable band gap, strong light-matter interaction, and flexibility. In this review, photodetectors based on 2D nanomaterials are classified with respect to critical element technology (e.g., active channel, contact, interface, and passivation). We discuss key ideas for improving the performance of the 2D photodetectors. In addition, figure-of-merits (responsivity, detectivity, response speed, and wavelength spectrum range) are compared to evaluate the performance of diverse 2D photodetectors. In order to achieve highly reliable 2D photodetectors, in-depth studies on material synthesis, device structure, and integration process are still essential. We hope that this review article is able to render the inspiration for the breakthrough of the 2D photodetector research field.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1242-1247
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• 2003

In order to passivate the GaAs surface, silicon-nitride films were fabricated by using laser CVD method. SiH$_4$ and NH$_3$ were used to obtain SiN films in the range of 100∼300$^{\circ}C$ on p-type (100) GaAs substrate. To determine interface characteristics of the metal-insulator-GaAs structure, electrical measurements were performed such as C-V curves and deep level transient spectroscopy (DLTS). The results show that the hysteresis was reduced and interface trap density was lowered to 1,012 ∼ 1,013 at 100 ∼ 200$^{\circ}C$. According to the study of surface leakage current, the passivated CaAs has less leakage current compared to non-passivated substrate.

• Journal of the Semiconductor & Display Technology
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• v.11 no.2
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• pp.7-11
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• 2012

SiNx films have been wildly used as anti-reflection coatings and passivation for crystalline silicon solar cells. In this study, the SiNx films were deposited by using high frequency (13.56MHz) PECVD and optical & passivation properties were investigated. The RF power was changed in a certain range for the film deposition. Then, the refractive index, etch rate, minority carrier lifetime and cell efficiency were measured to study the properties of the film respectively. The optimal deposition conditions for application to crystalline silicon solar cells were proposed as results of the study. Finally, the best cell efficiency of 16.98% was obtained from the solar cell with the SiNx films deposited by RF power of 550W.

• Corrosion Science and Technology
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• v.9 no.1
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• pp.20-28
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• 2010

According to the bipolar model, ion selectivity of some species in the passive film is important factor to control the passivation. An increase of cation selectivity of outer layer of the passive film can stabilize the film and improves the corrosion resistance. Therefore, the formation and roles of ionic species in the passive film should be elucidated. In this work, two types of solution (hydrochloric or sulfuric acid) were used to test high N and Mo-bearing stainless steels. The objective of this work was to investigate the formation of oxyanions in the passive film and the roles of oxyanions in passivation of stainless steel. Nitrogen exists as atomic nitrogen, nitric oxide, nitro-oxyanions (${NO_x}^-$), and N-H species, not nitride in the passive film. Because of its high mobility, the enriched atomic nitrogen can act as a reservoir. The formation of N-H species buffers the film pH and facilitates the formation of oxyanions in the film. ${NO_x}^-$ species improve the cation selectivity of the film, increasing the oxide content and film density. ${NO_x}^-$ acts similar to a strong inhibitor both in the passive film and at active sites. This facilitates the formation of chromium oxide. Also, ${NO_x}^-$ can make more molybdate and nitric oxide by reacting with Mo. The role of Mo addition on the passivation characteristics of stainless steel may differ with the test environment. Mo exists as metallic molybdenum, molybdenum oxide, and molybdate and the latter facilitates the oxide formation. When nitrogen and molybdenum coexist in stainless steel, corrosion resistance in chloride solutions is drastically increased. This synergistic effect of N and Mo in a chloride solution is mainly due to the formation of nitro-oxyanions and molybdate ion. Oxyanions can be formed by a 'solid state reaction' in the passive film, resulting in the formation of more molybdate and nitric oxide. These oxyanions improve the cation selectivity of the outer layer and form more oxide and increase the amount of chromium oxide and the ratio of $Cr_2O_3/Cr(OH)_3$ and make the film stable and dense.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.484-487
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• 2018

In this paper, the optical and electrical properties of ytterbium films were studied for water vapor transmission rate (WVTR) analysis of encapsulation films used in organic electronic devices. Ytterbium thin films show a wide range of light transmittance (70-10%) and resistivity ($6.0-0.16m{\Omega}{\cdot}cm$) depending on various film thicknesses (20-100 nm). The Yb thin films were oxidized with moisture and its transmittance and resistance changed in real time. As a result, the WVTR of parylene and aluminum nitride (AlN) laminated thin encapsulation film was measured to be $4.3{\times}10^{-3}g/m^2{\cdot}day$ with the 25 nm thick ytterbium thin film.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.75-81
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• 2018

The effect of $Ar-N_2$ plasma treatment on Cu surface as one of solutions to realize reliable Cu-Cu wafer bonding was investigated. Structural characteristic of $Ar-N_2$ plasma treated Cu surface were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscope. Ar gas was used for a plasma ignition and to activate Cu surface by ion bombardment, and $N_2$ gas was used to protect the Cu surface from contamination such as -O or -OH by forming a passivation layer. The Cu specimen under high Ar partial pressure plasma treatment showed more copper oxide due to the activation on Cu surface, while Cu surface after high $N_2$ gas partial pressure plasma treatment showed less copper oxide due to the formation of Cu-N or Cu-O-N passivation layer. It was confirmed that nitrogen plasma can prohibit Cu-O formation on Cu surface, but nitrogen partial pressure in the $Ar-N_2$ plasma should be optimized for the formation of nitrogen passivation layer on the entire surface of Cu wafer.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.30-36
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• 1997

AlGaAs/GaAs HBTs are developed well enough to be commercialized as an active device in optical transmission system, but there remains the unanswered questions about reliability. In this paper we applied the reverse constant current stress at the high voltage in avalanche region for a long time to find out a new degradation mechanism of junctrion I-V. The unction off-set voltage at which the current vanishes to zero was shifted to the negative direction of applied bias due to the increment of leakage current as the stress time increases. It was identified that the degradation was induced by the hot carriers which were generated at space charge region and trapped at the interface between GaAs base and the passivation nitride enhancing the electric field across the nesa edge.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.88-93
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• 1998

For the self-aligned AlGaAs/GaAs HBTs, the surface states at the interface between the extrinsic base surface and the passivation nitride is a major cause of degradation of dc characteristics. In this paper the degradation mechanisms of self-aligned AlGaAs/GaAs HBT were analyzed, and GaAs HBTs, which employed an InGaP ledge emitter structure formed by the nonself-aligned process to cover the surface of the extrinsic base and reduce the surface states, produced high reliability. Accoridng to the acceleration lifetime test, the nonself-aligned InGaP/GaAs HBTs produced very reliable dc characteristics comparing with the self-aligned AlGaAs/GaAs HBTs. The activation energy was 1.97eV and MTTF $4.8{\times}10^{8}$ hrs at $140^{\circ}C$ which satisfied the MIL standard.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.221-222
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• 2008

In Crystalline Si solar cells, Anti-Reflection Coating is contribute to improvement in energy conversion efficiency due to decrease of optical loss and recombination owing to surface passivation. Porous Si is formed electrochemical etching that uses chemical solution and anodization etching. So It gives that advantage in rapid process time and without high cost equipment. In this paper, We compare Porous Si with $SiO_2$/SiNx ARC and analyze that by anti-reflection coating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.546-546
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• 2008

Copper (Cu) Chemical mechanical polishing (CMP) has been an essential process for Cu wifing of DRAM and NAND flash memory beyond 45nm. Copper has been employed as ideal material for interconnect and metal line due to the low resistivity and high resistant to electro-migration. Damascene process is currently used in conjunction with CMP in the fabrication of multi-level copper interconnects for advanced logic and memory devices. Cu CMP involves removal of material by the combination of chemical and mechanical action. Chemicals in slurry aid in material removal by modifying the surface film while abrasion between the particles, pad, and the modified film facilitates mechanical removal. In our research, we emphasized on the role of chemical effect of slurry on Cu CMP, especially on the effect of amine functional group on removal rate selectivity between Cu and Tantalum-nitride (TaN) film. We investigated the two different kinds of complexing agent both with amine functional group. On the one hand, Polyacrylamide as a polymer affected the stability of abrasive, viscosity of slurry and the corrosion current of copper film especially at high concentration. At higher concentration, the aggregation of abrasive particles was suppressed by the steric effect of PAM, thus showed higher fraction of small particle distribution. It also showed a fluctuation behavior of the viscosity of slurry at high shear rate due to transformation of polymer chain. Also, because of forming thick passivation layer on the surface of Cu film, the diffusion of oxidant to the Cu surface was inhibited; therefore, the corrosion current with 0.7wt% PAM was smaller than that without PAM. the polishing rate of Cu film slightly increased up to 0.3wt%, then decreased with increasing of PAM concentration. On the contrary, the polishing rate of TaN film was strongly suppressed and saturated with increasing of PAM concentration at 0.3wt%. We also studied the electrostatic interaction between abrasive particle and Cu/TaN film with different PAM concentration. On the other hand, amino-methyl-propanol (AMP) as a single molecule does not affect the stability, rheological and corrosion behavior of the slurry as the polymer PAM. The polishing behavior of TaN film and selectivity with AMP appeared the similar trend to the slurry with PAM. The polishing behavior of Cu film with AMP, however, was quite different with that of PAM. We assume this difference was originated from different compactness of surface passivation layer on the Cu film under the same concentration due to the different molecular weight of PAM and AMP.