• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.112-116
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• 2000

This paper presents anisotropic ethcing characteristics of single-crystal silicon in tetramethylammonium hydroxide(TMAH):isopropyl alcohol(IPA) solutions containing pyrazine. With the addition of IPA to TMAH solutions, etching characteristics are exhibited that indicate an improvement in flatness on the etching front and a reduction in undercutting, but the etch rate on (100) silicon is decreased. The (100) silicon etch rate is improved by the addition of pyrazine. An etch rate on (100) silicon of $0.8\;{\mu}m/min$, which is faster by 13 % than a 20 wt.% solution of pure TMAH, is obtained using 20 wt.% TMAH:0.5 g/100 ml pyrazine solutions, but the etch rate on (100) silicon is decreased if more pyrazine is added. With the addition of pyrazine to a 25 wt.% TMAH solution, variations in flatness on the etching front were not observed and the undercutting ratio was reduced by 30 ~ 50 %.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.2
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• pp.125-130
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• 2000

Two step growth of reduced pressure chemical vapor eposition has been successfully developed to achieve in-situ phosphorus-doped silicon epilayers, and the characteristic evolution on their microstructures has been investigated using scanning electron microscopy, transmission electron microscopy, and secondary ion mass spectroscopy. The two step growth, which employs heavily in-situ P doped silicon buffer layer grown at low temperature, proposes crucial advantages in manipulating crystal structures of in-situ phosphorus doped silicon. In particular, our experimental results showed that with annealing of the heavily P doped silicon buffer layers, high-quality epitaxial silicon layers grew on it. the heavily doped phosphorus in buffer layers introduces into native oxide and plays an important role in promoting the dispersion of native oxides. Furthermore, the phosphorus doping concentration remains uniform depth distribution in high quality single crystalline Si films obtained by the two step growth.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1019-1023
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• 1995

A light-emitting silicon material was prepared by electrochemical etching of n-Si single crystal wafers in a solution of hydrofluoric acid and ethanol. Visible photoluminescence from the silicon was inhomogeneous and decayed rapidly in the ambient laboratory conditions or with photoirradiation. Substantial improvements in photoluminescence which include little-dependent luminescence peak energy with excitation energy variation and longer-lasting room temperature visible photoluminescence were achieved when the surface of photoluminescent silicon material was derivatized with the surface modifier of octadecylmercaptan. Surface modification of the photoluminescent silicon was evidenced by the measurements of contact angles of static water drops, FT-IR spectra and XPS data, in addition to changed photoluminescence. Similar improvements in photoluminescence were observed with the light-emitting silicon treated with dodecylmercaptan, but not with octadecane. The present results indicate that sulfurs of octadecylmercaptans or dodecylmercaptans appear to coordinate the surface Si atoms of LESi and perturb the surface states to significantly change the luminescent characteristics of LESi.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.197-201
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• 1997

The momentum, heat and mass trasfer phenomena in the silicon melt of the Czochralki crystal growth system are calculated using a three dimensional numerical simulation thechnique. Even though axisymmetrical boundary conditions are imposed to all calculations in a 3cm diameter crucible, several types of non-axisymmetric profiles of velocities, temperature and oxygen concentration appeared in the melt. Because of the non-axisymmetric profiles of velocities, temperature and oxygen concentration appeared in the melt. Because of the non-axisymmetric profiles and rotations of fluid induced by the crucible rotation, temperatures and oxygen concentrations in the silicon melt fluctuate. The rotating velocity of the profile is calculated from the phase shift of the data of temperature or oxygen at two different points which have same radius from center but 90 degree angular difference. From this calculation, it is found that the rotating veolocity of the oxygen and temperature is different from the crucible rotation rates. Therefore the frequencies of the oscillating temperature and oxygen concentrations are not same to the frequencies of the crucible rotations. Futhermore, the components of the frequencies of the temperature and oxygen concentration at the same point are not same. The fluctuation behaviors of the temperature or oxygen themselves are also different when the points are different. The calculation show that the temperature and the oxygen concentration near the interface also fluctuate. The results suggest that the striation pattern found in the grown silicon single crystals may ben generated by the oxygen concentration and the temperature oscillations of the melt occurred near the interface.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.4
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• pp.141-147
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• 2018

Solar energy has attracted big attentions as one of clean and unlimited renewable energy. Solar energy is transformed to electrical energy by solar cells which are comprised of multi-silicon wafer or mono-silicon wafer. Monosilicon wafers are fabricated from the Czochralski method. In order to decrease fabrication cost, increasing a poly-silicon charge size in one quartz crucible has been developed very much. When we increase a charge size, the temperature control of a Czochralski equipment becomes more difficult due to a strong melt convection. In this study, we simulated a Czochralski equipment temperature at 20 inch and 24 inch in quartz crucible diameter and various charge sizes (90 kg, 120 kg, 150 kg, 200 kg, 250 kg). The simulated temperature profiles are compared with real temperature profiles and analyzed. It turns out that the simulated temperature profiles and real temperature profiles are in good agreement. We can use a simulated profile for the optimization of real temperature profile in the case of increasing charge sizes.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.159-168
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• 2008

Thermally-evaporated 10 nm-Ni/1 nm-Ru/(30 nm or 70 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Ru-inserted nickel monosilicide. The silicide samples underwent rapid thermal anne aling at $300{\sim}1,100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution X-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope(SPM) were used to determine the cross-sectional structure and surface roughness. The silicide, which formed on single crystal silicon and 30 nm polysilicon substrate, could defer the transformation of $Ni_2Si $i and $NiSi_2 $, and was stable at temperatures up to $1,100^{\circ}C$ and $1,100^{\circ}C$, respectively. Regarding microstructure, the nano-size NiSi preferred phase was observed on single crystalline Si substrate, and agglomerate phase was shown on 30 nm-thick polycrystalline Si substrate, respectively. The silicide, formed on 70 nm polysilicon substrate, showed high resistance at temperatures >$700^{\circ}C$ caused by mixed microstructure. Through SPM analysis, we confirmed that the surface roughness increased abruptly on single crystal Si substrate while not changed on polycrystalline substrate. The Ru-inserted nickel monosilicide could maintain a low resistance in wide temperature range and is considered suitable for the nano-thick silicide process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.143-145
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• 1996

A new method of fabricating 3-dimensional patterns on single crystal silicon is presented in this paper. The method utlizes both chemical and mechanical reactions to make patterns with dimensions of few microns in width and submicron in height. The primaryadvantage ofthis new method over conventional methods of making patterns on silicon lies in its cost effectiveness and speed. The process introduced in this paper is a maskless process and does not reauire expensive capital investment. It is expected that this method can be employed for flexible and cost effective fabrication of micro-machine components in MEMS application.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.186-195
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• 2002

The mechanism of micro machining of reacted layer on silicon surface were proposed. The depth of reacted layer and the change of mechanical property were measured and analyzed. Depth of hydrated layer which is created on the surface of silicon by potassium hydrate was analyzed with SEM and XPS. The decrease of the micro victors hardness of silicon surface was shown with the increase of the concentration of potassium hydrate and the change of the dynamic friction coefficient by chemical reacted layer was measured due to the readiness of machining. The experiment of groove machining was done with 3-axis machine with constant load. With chemical mechanical micro machining the surface crack and burrs generated by both brittle and ductile micro machining were diminished. And the surface profile and groove depth was shown in accordance with the machining speed and reaction time with SEM and AFM.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.246-251
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• 2014

Recent studies have shown methods of improving solar cell efficiency. Especially on single crystalline silicon wafer which is high-efficiency solar cell material that has been widely studied. Interstitial oxygen (Oi) is the main impurity in the Czochralski (Cz) growing method, and excess of this can form precipitates during cell fabrication. We have demonstrated the effect of Oi impurity and oxygen precipitation concentration of the wafer on Cz-silicon solar cell efficiency. The result showed a decrease in cell efficiency as Oi and oxygen precipitation increase. Moreover, we have found that the critical point of [Oi] to bring higher cell efficiency is at 14.5 ppma in non-existent Bulk Micro Defect (BMD).

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.495-501
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• 1991

This study is intended to make defect-free region, denuded zone at the silicon wafer surface for semiconductor device substrates. In this experiment, initial oxygen concentration of starting material CZ-grown silicon wafer, various heat treatment combinations, denuding ambient and the amounts of oxygen reduction were measured, and then denuded zone (DZ) formation and depth were investigated. In Low/High anneal (DZ formation could be achieved), the optimum temperature for Low anneal was 700$^{\circ}C$∼750$^{\circ}C$. In case of High anneal, with the time increased, DZ depth was increased at 1000$^{\circ}C$, 1150$^{\circ}C$ respectively, but on the contrary, DZ depth was decreased at low temperature 900$^{\circ}C$. As well, out-diffusion time below 2 hours was unsuitable for effective Gettering technique even though the temperature was high, and DZ formation could be achieved when initial oxygen concentration was only above 14 ppm in silicon wafer.