• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.206-209
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• 2002

The fixed abrasive pad(FAP) has been introduced in chemical mechanical polishing(CMP) field recently. In comparison with the general CMP which uses the slurry including abrasives, FAP takes advantage of planarity. resulting from decreasing pattern selectivity and defects such as dishing due to the reduction of abrasive concentration especially. This paper introduces the manufacturing technique of $Al_2$O$_3$-FAP using hydrophilic polymers with swelling characteristic in water and explains the self.texturing phenomenon. It also focuses on the chemical effects on tungsten film and the FAP is evaluated on the removal rate as a function of chemicals such as oxidizer, catalyst, and acid. The removal rate is achieved up to 1000A1min as about 70 percents of the general one. In the future. the research has a plan of the advanced FAP and chemicals in tungsten CMP considering micro-scratch, life-time, and within wafer non-uniformity.

• Korean Journal of Materials Research
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• v.21 no.5
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• pp.243-249
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• 2011

To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al-BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to $89^{\circ}C$/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al-BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.169-173
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• 2008

Characteristics of etching and induced surface morphology variation by wet-etching of n-type GaN were investigated using phosphoric acidic solutions. Generally, the etch-rate was increased as the temperature of the etch solutions was increased, and the highest etch rate of about $300{\AA}/min$ was achieved at the temperature of $180^{\circ}C$. The morphology variation of the etched surface was observed by optical microscopy and atomic force microscopy. Initially, high density of hexagonal holes or pits were formed on the etched surface at the time of 40 min with the bimodal size of $20{\mu}m$ or $5{\mu}m$, respectively. However, as the etching time was increased further, the lateral size of the hexagonal holes or pits was increased, and finally, joined and merged together at the time of 100 min. This means that the etching of n-type GaN by phosphoric acidic solutions proceeded through the lateral widening and the merging of initial holes and pits.

• Korean Journal of Metals and Materials
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• v.56 no.12
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• pp.915-920
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• 2018

With the development of modern microelectronics technologies, the power density of electronic devices is rapidly increasing, due to the miniaturization or integration of device elements which operate at high frequency, high power conditions. Resulting thermal problems are known to cause power leakage, device failure and deteriorated performance. To relieve heat accumulation at the interface between chips and heat sinks, thermal interface materials (TIMs) must provide efficient heat transport in the through-plane direction. We report on the enhanced thermal conduction of $Al_2O_3-based$ polymer composites, fabricated by the surface wetting and texturing of thermally conductive hexagonal boron nitride(h-BN) nanoplatelets with large anisotropy in morphology and physical properties. The thermally conductive polymer composites were prepared with hybrid fillers of $Al_2O_3$ macro beads and surface modified h-BN nanoplatelets. Hexagonal boron nitride (h-BN) has high thermal conductivity and is one of the most suitable materials for thermally conductive polymer composites, which protect electronic devices by efficient heat dissipation. In this study, we synthesized hexagonal boron nitride nanoparticles by the pyrolysis of cost effective precursors, boric acid and melamine. Through pyrolysis at $900^{\circ}C$ and subsequent annealing at $1500^{\circ}C$, hexagonal boron nitride nanoparticles with diameters of ca. 50nm were synthesized. We demonstrate that the addition of a small amount of calcium fluoride ($CaF_2$) during the preparation of the melamine borate adduct significantly enhanced the crystallinity of the h-BN and assisted the growth of nanoplatelets up to 100nm in diameters. The addition of a small amount of h-BN enhanced the thermal conductivity of the $Al_2O_3-based$ polymer composites, from 1.45W/mK to 2.33 W/mK.