• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 제11차 KACG 학술발표회 Crystalline Particle Symposium (CPS)
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• pp.129-153
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• 1996

In aqueous slurry processing of silicon nitride, the interaction of dispersant and binder on the surface of particles was studied to identify the effect of these additives on ceramic powder processing. Polymethacrylic acid (PMAA) and polyvinyl alcohol (PVA) were used as dispersant and binder, respectively. the adsorption isotherms of PMAA and PVA for the silicon nitride suspension were determined, while the adsorption of PMAA was differentiated in the mixed additive system by ultraviolet spectroscopy. These experiments were done in order to investigate the effect of these organic additives on the physicochemical properties of silicon nitride suspensions. The electrokinetic behavior of silicon nitride was subsequently measured by electrokinetic sonic amplitude (ESA). As PMAA adsorbed onto silicon nitride, the isoelectric point (pHicp) shifted from pH=6.7 to acidic pH, depending on the surface coverage of PMAA. However, adsorption of PVA did not change the pHicp of suspensions, but did decrease the surface potential of silicon nitride moderately. The rheological behavior of silicon nitride suspensions was measured to assess the stability of particles in aqueous media, and was correlated with the electrokinetic behavior and adsorption isotherm data for silicon nitride.

• 자원리싸이클링
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• 제18권1호
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• pp.38-43
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• 2009

본 고에서는 현행 고순도 폴리실리콘 제조공정에서 부산물로 발생하고 있는 실리콘 미세분말을 경제적인 가격에 태양전지급 원료로 재이용하고자 실리콘 미세분말의 무점결제 성형공정에 대한 연구를 수행하였다. 폴리실리콘 미세분말의 평균 크기는 $7.8{\mu}m$였으며, 주요 불순물은 표면 산화물과 수분이었다. 표면 산화물을 제거하기 위한 HF수용액-에탄올 혼합용액을 이용한 전처리공정을 행함으로써 폴리실리콘 분말의 성형성 그리고 성형체의 밀도 및 강도를 향상시킬 수 있었다. 진공 중에서 성형하는 경우 성형체 회수율이 20%증가하였다. 폴리실리콘 미세 분말은 공정 부산물 상태에서는 태양전지용 원료로 사용되기에 적합한 순도가 아니었지만, 건식 열처리를 행함으로써 태양전지급 이상의 순도를 확보할 수 있었다.

• 한국세라믹학회지
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• 제49권4호
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• pp.363-368
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• 2012

Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with $Si_3N_4$ content, while the highest extent of nitridation was measured in $Si_3N_4$-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the $Si_3N_4$-free specimen. On the other hand, pores from the decomposed pore former were retained in the $Si_3N_4$-added specimen. Introduction of small $Si_3N_4$ particles ($d_{50}=0.3{\mu}m$) into a powder compact consisting of large silicon particles ($d_{50}=7{\mu}m$) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to $Si_3N_4$ size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body.

• 한국세라믹학회지
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• 제22권1호
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• pp.53-59
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• 1985

Experiments related to nitriding silicon with addition of $Si_3N_4$ have provided information on the effects of such inclusion on the phase relationships of Reaction Bonded Silicon Nitride. In the current work specimens containing 0-25wt% Si3N4 which have 55.5wt% $\alpha$ 4.5wt% $eta$, 40wt% amorphous phase were nitrided for 7-20 hours at 1300-135$0^{\circ}C$ The evaluation of nitridation was per-formed by means of $\alpha$-and $\beta$-phase contents determination in nitrided specimens, In order to observe nitrided region between silicon and silicon nitride scanning electron microscopy was used to study reacted region between silicon and silicon nitride particle. For this purpose semiconductor-grade silicon wafer single crystal was used as a silicon source. The incorporation of small amount of $Si_3N_4$ powder is contributed to enhancing the rate of formation of $\alpha$-phase.

• 마이크로전자및패키징학회지
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• 제10권3호
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• pp.67-71
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• 2003

실리콘 주괴(ingot)에서 실리콘 웨이퍼를 제조할 때 사용되는 슬러리는 SiC 연마재와 절삭유를 포함한다. 실리콘 웨이퍼 제조 시 생긴 폐슬러지에서 SiC 연마재와 절삭유는 분리되어 재활용된다. 본 연구는 폐슬러지 Si 분말에 C분말을 혼합하여 SiC를 합성하는 것에 관한 것이다. 다양한 크기의 SiC 분말과 휘스커가 제조되었으며 기존의 휘스커의 크기보다 작은 나노미터 크기의 휘스커도 발생하였다. 일반적으로 휘스커는 금속 불순물을 첨가하여 제조되는데, 본 연구에서 나노미터 크기의 휘스커 발생은 폐슬러지에 첨가되어있는 미세한 크기의 금속불순물의 영향으로 판단된다.

• 한국세라믹학회지
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• 제32권10호
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• pp.1162-1168
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• 1995

Systematic studies of the effects of additives and processing variables on the sintered density and the effect of crystalline forms of starting powders on the microstructure of pressureless sintered silicon carbide are described. Oxide additives were effective for the densification of SiC up to 96% of theoretical density at temperature as low as 185$0^{\circ}C$. Use of embedding powder increased the sintered density, up to 98% of theoretical density, by decreasing the weight loss during sintering. Composite type duplex microstructure has been developed due to the $\beta$longrightarrow$\alpha$ phase transformation of SiC by sintering at 185$0^{\circ}C$ and heat treatment at 195$0^{\circ}C$ for 1h.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.356-362
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• 1998

Hertzian crack suppression phenomena and relatively high damage tolerance were investigated in hard/soft silicon nitride ($Si_3N_4$) bilayers. Coarse $\alpha}-Si_3N_4$ powder was wsed for the hard coating layer and fine $\alpha}-Si_3N_4$ powder was used for the soft substrate layer. The two layers were designed with a strong interface. Hertzian indentation was used to investigate contact fracture and damage tolerance property. Hertzian crack suppression has occurred with increasing applied load and decreasing coating thickness. The crack suppression contributed strength improvement, especially in the bilayers with thinner coatings. Ultimately, the combination of hard coating with soft but tough underlayer improved the damage tolerance of brittle $Si_3N_4$ ceramics.

• Advances in materials Research
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• 제5권3호
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• pp.131-140
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• 2016

Copper/silicon nitride ($Cu/Si_3N_4$) composites are fabricated by powder technology process. Copper is used as metal matrix and very fine $Si_3N_4$ particles (less than 1 micron) as reinforcement material. The investigated powder were used to prepare homogenous ($Cu/Si_3N_4$) composite mixtures with different $Si_3N_4$ weight percentage (2, 4, 6, 8 and10). The produced mixtures were cold pressed and sintered at different temperatures (850, 950, 1000, $1050^{\circ}C$). The microstructure and the chemical composition of the produced $Cu/Si_3N_4$ composites were investigated by (SEM) and XRD. It was observed that the $Si_3N_4$ particles were homogeneously distributed in the Cu matrix. The density, electrical conductivity and coefficient of thermal expansion of the produced $Cu/Si_3N_4$ composites were measured. The relative green density, sintered density, electrical conductivity as well as coefficient of thermal expansion were decreased by increasing the reinforcement phase ($Si_3N_4$) content in the copper matrix. It is also founded that the sintered density and electrical conductivity of the $Cu/Si_3N_4$ composites were increased by increase the sintering temperature.

• 한국재료학회지
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• 제14권5호
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• pp.358-362
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• 2004

$Si_3$$N_4$ ceramics have been identified as one of the promising structural ceramics. This study has been carried out to investigate of the synthetic behaviors of $Si_3$$N_4$ derived from domestic silica-stone by direct nitriding method. The silicon nitridation reaction has been studied in the temperature range of $1300～1550^{\circ}C$. Below the $1400^{\circ}C$, the nitriding rate was measured to be 16%. For the temperatures higher than the $1400^{\circ}C$, $\beta$-$Si_3$$N_4$ phase was formed mainly, and the nitriding rate showed above 98%. With the increasing of sample weight of silicon powder, the nitriding rate and $\beta$-$Si_3$$N_4$ phase increased at $1400^{\circ}C$ for 2 hours. The shape and particle size of$ Si_3$$N_4$ powder synthesized at $1400^{\circ}C$ for 2 hours showed the irregular angular-type and 10 $\mu\textrm{m}$, respectively.

• 한국분말재료학회지
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• 제28권1호
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• pp.25-30
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• 2021

The surface of silicon dummy wafers is contaminated with metallic impurities owing to the reaction with and adhesion of chemicals during the oxidation process. These metallic impurities negatively affect the device performance, reliability, and yield. To solve this problem, a wafer-cleaning process that removes metallic impurities is essential. RCA (Radio Corporation of America) cleaning is commonly used, but there are problems such as increased surface roughness and formation of metal hydroxides. Herein, we attempt to use a chelating agent (EDTA) to reduce the surface roughness, improve the stability of cleaning solutions, and prevent the re-adsorption of impurities. The bonding between the cleaning solution and metal powder is analyzed by referring to the Pourbaix diagram. The changes in the ionic conductivity, H2O2 decomposition behavior, and degree of dissolution are checked with a conductivity meter, and the changes in the absorbance and particle size before and after the reaction are confirmed by ultraviolet-visible spectroscopy (UV-vis) and dynamic light scattering (DLS) analyses. Thus, the addition of a chelating agent prevents the decomposition of H2O2 and improves the life of the silicon wafer cleaning solution, allowing it to react smoothly with metallic impurities.