• Journal of the Korean institute of surface engineering
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• v.53 no.5
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• pp.249-256
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• 2020

As the size of manufacturing equipment for LCD and OLED displays increases, replacement of existing heavy stainless steel components with light metals, such as aluminum alloys, is being more important in semiconducting and display manufacturing industries. To use aluminum alloys for components in semiconducting and display industries, it is important to develop a new anodization method for improved performance of anodic oxide films than conventional anodization method based on sulfuric acid. In this work, optimum applied current density and the best sealing methods for anodic oxide films in 3% oxalic acid were explored. Experimental results showed 2.5 A/dm2 is the best applied current density for improved hardness and dielectric breakdown voltage. Sealing of the anodic oxide films further improved their hardness, dielectric breakdown voltage and resistance to HCl, by which application of anodic oxide films become applicable for components in semiconducting and display industries.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.4
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• pp.69-74
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• 2010

A new package substrate for dynamic random access memory(DRAM) devices has been developed using selective aluminum anodization. Unlike the conventional substrate structure commonly made by laminating epoxy-based core and copper clad, this substrate consists of bottom aluminum, middle anodic aluminum oxide and top copper. Anodization process on the aluminum substrate provides thick aluminum oxide used as a dielectric layer in the package substrate. Placing copper traces on the anodic aluminum oxide layer, the resulting two-layer metal structure is completed in the package substrate. Selective anodization process makes it possible to construct a fully filled via structure. Also, putting vias directly in the bonding pads and the ball pads in the substrate design, via in pad structure is applied in this work. These arrangement of via in pad and two-layer metal structure make routing easier and thus provide more design flexibility. In a substrate design, all signal lines are routed based on the transmission line scheme of finite-width coplanar waveguide or microstrip with a characteristic impedance of about $50{\Omega}$ for better signal transmission. The property and performance of anodic alumina based package substrate such as layer structure, design method, fabrication process and measurement characteristics are investigated in detail.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.757-763
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• 2019

A stacked high-voltage (900 V) Al electrolytic capacitor made with ZrO₂ coated anode foils, which has not been studied so far, is realized and the effects of Zr-Al-O composite layer on the electric properties are discussed. Etched Al foils coated with ZrO₂ sol are anodized in 2-methyl-1,3-propanediol (MPD)-boric acid electrolyte. The anodized Al foils are assembled with stacked structure to prepare the capacitor. The capacitance and dissipation factor of the capacitor with ZrO₂ coated anode foils increase by 41 % and decrease by 50 %, respectively, in comparison with those of Al anode foils. Zr-Al-O composite dielectric layer is formed between separate crystalline ZrO₂ with high dielectric constant and amorphous Al₂O₃ with high ionic resistivity. This work suggests that the formation of a composite layer by coating valve metal oxide on etched Al foil surface and anodizing it in MPD-boric acid electrolyte is a promising approach for high voltage and volume efficiency of capacitors.

• Corrosion Science and Technology
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• v.15 no.3
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• pp.120-124
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• 2016

The effect of alloying element Ca (0, 1, and 2 wt%) on corrosion resistance and bioactivity of the as-received and anodized surface of rolled plate AM60 alloys was investigated. A plasma electrolytic oxidation (PEO) was carried out to form anodic oxide film in $0.5mol\;dm^{-3}\;Na_3PO_4$ solution. The corrosion behavior was studied by polarization measurements while the in vitro bioactivity was tested by soaking the specimens in Simulated Body Fluid (1.5xSBF). Optical micrograph and elemental analysis of the substrate surfaces indicated that the number of intermetallic particles increased with Ca content in the alloys owing to the formation of a new phase $Al_2Ca$. The corrosion resistance of AM60 specimens improved only slightly by alloying with 2 wt% Ca which was attributed to the reticular distribution of $Al_2Ca$ phase existed in the alloy that might became barrier for corrosion propagation across grain boundaries. Corrosion resistance of the three alloys was significantly improved by coating the substrates with anodic oxide film formed by PEO. The film mainly composed of magnesium phosphate with thickness in the range $30-40{\mu}m$. The heat resistant phase of $Al_2Ca$ was believed to retard the plasma discharge during anodization and, hence, decreased the film thickness of Ca-containing alloys. The highest apatite forming ability in 1.5xSBF was observed for AM60-1Ca specimens (both substrate and anodized) that exhibited more degradation than the other two alloys as indicated by surface observation. The increase of surface roughness and the degree of supersaturation of 1.5xSBF due to dissolution of Mg ions from the substrate surface or the release of film compounds from the anodized surface are important factors to enhance deposition of Ca-P compound on the specimen surfaces.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.265.1-265.1
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• 2013

Nanoporous anodic aluminum oxide (AAO), a self-ordered hexagonal array has various applications for nanofabrication such as nanotemplate, and nanostructure. In order to obtain highly-ordered porous alumina membranes, Masuda et al. proposed a two-step anodization process however this process is confined to small domain size and long hours. Recently, alternative methods overcoming limitations of two-step process were used to make prepatterned Al surface. In this work, we confirmed that there is a specific tendency used a PDMS stamp to obtain a pre-patterned Al surface. Using the nanoindentaions of a PDMS stamp as chemical carrier for wet etching, we can easily get ordered nanoporous template without two-step process. This chemical etching method using a PDMS stamp is very simple, fast and inexpensive. We use two types of PDMS stamps that have different intervals (800nm, 1200nm) and change some parameters have influenced the patterning of being anodized, applied voltage, soaking and stamping time. Through these factors, we demonstrated the patterning effect of large scale PDMS stamp.

• Proceedings of the Korean Vacuum Society Conference
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• 2003.08a
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• pp.178-178
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• 2003

• Korean Journal of Materials Research
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• v.17 no.2
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• pp.81-85
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• 2007

Embedded capacitor technology can improve electrical perfomance and reduce assembly cost compared with traditional discrete capacitor technology. To improve the capacitance density of the $Al_2O_3$ based embedded capacitor on Cu cladded fiber reinforced plastics (FR-4), the specific surface area of the $Al_2O_3$ thin films was enlarged and their surface morphologies were controlled by anodization process parameters. From I-V characteristics, it was found that breakdown voltage and leakage current were 23 V and $1{\times}10^{-6}A/cm^2$ at 3.3 V, respectively. We have also measured C-V characteristics of $Pt/Al_2O_3/Al/Ti$ structure on CU/FR4. The capacitance density was $300nF/cm^2$ and the dielectric loss was 0.04. This nano-porous $Al_2O_3$ is a good material candidate for the embedded capacitor application for electronic products.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.69-72
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• 2002

We establish a visible light emission from porous polycrystalline silicon nano structure(PPNS). The PPNS layer are formed on heavily doped n-type Si substrate. 2um thickness of undoped polycrystalline silicon deposited using LPCVD (Low Pressure Chemical Vapor Deposition) anodized in a HF: ethanol(=1:1) as functions of anodizing conditions. And then a PPNS layer thermally oxidized for 1 hr at $900^{\circ}C$. Subsequently, thin metal Au as a top electrode deposited onto the PPNS surface by E-beam evaporator and, in order to establish ohmic contact, an thermally evaporated Al was deposited on the back side of a Si-substrate. When the top electrode biased at +6V, the electron emission observed in a PPNS which caused by field-induces electron emission through the top metal. Among the PPNSs as functions of anodization conditions, the PPNS anodized at a current density of $10mA/cm^{2}$ for 20 sec has a lower turn-on voltage and a higher emission current. Furthermore, the behavior of electron emission is uniformly maintained.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.3
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• pp.25-34
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• 1981

Aluminum anodization method has been investigated for fabricating charge coupled device(CCD) with two-level aluminum gate structure. Al2O3 films were formed to a thickness of 400-500A, by anodizing aluminum with 30-35V of anode voltage for 2 hours using 2 % ammonium tartrate solution as an electrolyte. Breakdown voltage of these films were about 30 volts. Using above mentioned Al2O3 film as an insulator between two aluminum electrodes, CCD transversal low pass filter has been fabricated. CCD transversal low pass filter with 17 tap coefficients has shown 22 dB stop-band attenuation. The operating clock frequency range of the fabricated device was from 3 KHz to 100 KHz.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.540-544
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• 2002

Hydration treatments were performed on the pure aluminum substrate at $100^{\circ}C$ followed by anodizing and heat treatments on the layers. The transformation behaviors of the oxide layers according to the hydration treatment were studied using TEM, XRD, RBS etc. Above $90^{\circ}C$ the hydrous oxide film could be formed, which were turned out to be hydrous oxides(AlOOH $nH_2$O). The anodization on the hydrous oxide film was more effective for the transition of amorphous anodic oxides to the crystalline $\Upsilon-Al_2$ $O_3$ comparing with the case for anodizing on the aluminum substrate without hydration treatment And additional heat treatments were also helpful for the acceleration of the transformation of the hydrous oxide to $\Upsilon-Al_2$ $O_3$. During the heat treatment the interface between $\Upsilon-Al_2$ $O_3$and the hydrous oxide layers migrated to the outer side of hydrous layer.