• Proceedings of the Korean Vacuum Society Conference
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• 1996.06a
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• pp.40-41
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• 1996

Nitridation technique has been receiving much attention for the formation of a thin nitrided buffer layer on which high quality nitride films can be formedl. Particularly, gallium nitride (GaN) has been considered as a promising material for blue-and ultraviolet-emitting devices. It can also be used for in situ formed and stable passivation layers for selective growth of $GaAs_2$. In this work, formation of a thin nitrided layer is investigated. Nitrogen electron cyclotron resonance(ECR)-plasma is employed for the formation of thin nitrided layer. The plasma source used in this work is a compact ECR plasma gun3 which is specifically designed to enhance control, and to provide in-situ monitoring of plasma parameters during plasma-assisted processing. Microwave power of 100-200 W was used to excite the plasma which was emitted from an orifice of 25 rnm in diameter. The substrate were positioned 15 em away from the orifice of plasma source. Prior to nitridation is performed, the surface of n-type (001)GaAs was exposed to hydrogen plasma for 20 min at $300{\;}^{\circ}C$ in order to eliminate a native oxide formed on GaAs surface. Change from ring to streak in RHEED pattern can be obtained through the irradiation of hydrogen plasma, indicating a clean surface. Nitridation was carried out for 5-40 min at $RT-600{\;}^{\circ}C$ in a ECR plasma-assisted molecular beam epitaxy system. Typical chamber pressure was $7.5{\times}lO^{-4}$ Torr during the nitridations at $N_2$ flow rate of 10 seem.(omitted)mitted)

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.162-162
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• 2010

InSb has received great attentions as a promising candidate for the active layer of infrared photodetectors due to the well matched band gap for the detection of $3{\sim}5\;{\mu}m$ infrared (IR) wavelength and high electron mobility (106 cm2/Vs at 77 K). In the fabrication of InSb photodetectors, passivation step to suppress dark currents is the key process and intensive studies were conducted to deposit the high quality passivation layers on InSb. Silicon dioxide (SiO2), silicon nitride (Si3N4) and anodic oxide have been investigated as passivation layers and SiO2 is generally used in recent InSb detector fabrication technology due to its better interface properties than other candidates. However, even in SiO2, indium oxide and antimony oxide formation at SiO2/InSb interface has been a critical problem and these oxides prevent the further improvement of interface properties. Also, the mechanisms for the formation of interface phases are still not fully understood. In this study, we report the quantitative analysis of indium and antimony oxide formation at SiO2/InSb interface during plasma enhanced chemical vapor deposition at various growth temperatures and subsequent heat treatments. 30 nm-thick SiO2 layers were deposited on InSb at 120, 160, 200, 240 and $300^{\circ}C$, and analyzed by X-ray photoelectron spectroscopy (XPS). With increasing deposition temperature, contents of indium and antimony oxides were also increased due to the enhanced diffusion. In addition, the sample deposited at $120^{\circ}C$ was annealed at $300^{\circ}C$ for 10 and 30 min and the contents of interfacial oxides were analyzed. Compared to as-grown samples, annealed sample showed lower contents of antimony oxide. This result implies that reduction process of antimony oxide to elemental antimony occurred at the interface more actively than as-grown samples.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.218-224
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• 2003

This paper describes a novel MEMS integration technique on a CMOS chip. MEMS integration on CMOS circuit has many advantages in view of manufacturing cost and reliability. The surface topography of a CMOS chip from a commercial foundry has 0.9 ${\mu}{\textrm}{m}$ bumps due to the conformal coating on aluminum interconnect patterns, which are used for addressing each MEMS element individually. Therefore, it is necessary to achieve a flat mirror-like CMOS chip fer the microelectromechanical system (MEMS) such as micro mirror array. Such CMOS chip needs an additional thickness of the dielectric passivation layer to ease the subsequent planarization process. To overcome a temperature limit from the aluminum thermal degradation, this study uses RF sputtering of silicon nitride at low temperature and then polishes the CMOS chip together with the surrounding dummy pieces to define a polishing plane. Planarization reduces 0.9 ${\mu}{\textrm}{m}$ of the bumps to less than 25 nm.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.1 no.1
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• pp.87-94
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• 2001

Silicon nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) are useful for a variety of applications, including anti-reflecting coatings in solar cells, passivation layers, dielectric layers in metal/insulator structures, and diffusion masks. PECVD systems are controlled by many operating variables, including RF power, pressure, gas flow rate, reactant composition, and substrate temperature. The wide variety of processing conditions, as well as the complex nature of particle dynamics within a plasma, makes tailoring SiN film properties very challenging, since it is difficult to determine the exact relationship between desired film properties and controllable deposition conditions. In this study, SiN PECVD modeling using optimized neural networks has been investigated. The deposition of SiN was characterized via a central composite experimental design, and data from this experiment was used to train and optimize feed-forward neural networks using the back-propagation algorithm. From these neural process models, the effect of deposition conditions on film properties has been studied. A recipe synthesis (optimization) procedure was then performed using the optimized neural network models to generate the necessary deposition conditions to obtain several novel film qualities including high charge density and long lifetime. This optimization procedure utilized genetic algorithms, hybrid combinations of genetic algorithm and Powells algorithm, and hybrid combinations of genetic algorithm and simplex algorithm. Recipes predicted by these techniques were verified by experiment, and the performance of each optimization method are compared. It was found that the hybrid combinations of genetic algorithm and simplex algorithm generated recipes produced films of superior quality.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.899-901
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• 2009

The magnesium fluoride ($MgF_2$) has very higher optical transmission than oxide or nitride material applied for gas barrier, so we manufactured Mg-Zn-F films with Mg-Zn-F target mixed in the various ratio of $MgF_2$ to Zn and characterized films' properties. Zn is used to increase packing density of barrier film. Thickness and optical transmission of Mg-Zn-F are 200 nm and over 90 %, respectively. The result of water vapor transmission rate at 38, RH 90 ~ 100% of the Mg-Zn-F film deposited with 4 : 6 ($MgF_2$ : Zn) ratio target reached below $1{\times}10^{-3}g$/($m^2{\cdot}day$), measuring limit of instrument.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1274-1276
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• 1993

The silicon-nitride films formed by laser CVD method are used for passivating GaAs surfaces. The electrical Properties of metal-insulator-GaAs structure are studied to determined the interfacial characteristics by C-V curves and deep level transient spectroscopy(DLTS). The SiN films are photolysisly deposited from $SiH_4\;and\;NH_3$ in the range of $100^{\circ}C-300^{\circ}C$ on P type, (100) GaAs. The hysteresis is reduced and interface trap density is lowered to $10^{12}-10^{13}$ at $100^{\circ}C-200^{\circ}C$. The surface leakage current is studied too. The passivated GaAs have a little leakage current compared to non passivated GaAs.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.451-457
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• 2006

We synthesized phase pure CrN having surface areas up to $47m^2/g$ starting from $CrCl_{3}$ with $NH_{3}$. Thermal Gravimetric Analysis coupled with X-ray diffraction was carried out to identify solid state transition temperatures and the phase after each transition. In addition, the BET surface areas, pore size distributions, and crystalline diameters for the synthesized materials were analyzed. Space velocity influenced a little to the surface areas of the prepared materials, while heating rate did not. We believe it is due to the fast removal of reaction by-products from the system. Temperature programmed reduction results revealed that the CrN was hardly passivated by 1% $O_{2}$. Molecular nitrogen was detected from CrN at 700 and $950^{\circ}C$, which may be from lattice nitrogen. In temperature programmed oxidation with heating rate of 10 K/min in flowing air, oxidation started at or higher than $300^{\circ}C$ and resulting $Cr_{2}O_{3}$ phase was observed with XRD at around $800^{\circ}C$. However the oxidation was not completed even at $900^{\circ}C$. CrN catalysts were highly active for n-butane dehydrogenation reaction. Their activity is even higher than that of a commercial $Pt-Sn/Al_{2}O_{3}$ dehydrogenation catalyst in terms of volumetric reaction rate. However, CrN was not active in pyridine hydrodenitrogenation.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.21-25
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• 2014

The silicon nitride ($SiN_x$) film for surface passivation and anti-reflection coating of crystalline silicon solar cell is very important and it is generally deposited by plasma enhanced chemical vapor deposition (PECVD). PECVD can be divided into low and high frequency method. In this paper, the $SiN_x$ film deposited by low and high frequency PECVD method was studied. First, to optimize the $SiN_x$ film deposited by low frequency PECVD method, the refractive index was measured by varying the process conditions like $SiH_4$, $NH_3$, $N_2$ gas rate, and RF power. When $SiH_4$ gas rate was increased and $NH_3$ gas rate was decreased, the refractive index was increased. The refractive index was also increased with RF power decline. Second, to compare the characteristics of the low and high frequency PECVD $SiN_x$ film, the refractive index was measured by varying $NH_3/SiH_4$ gas ratio and RF power and the minority carrier lifetime of before and after high temperature treatment process was also measured. The refractive index of both low and high frequency PECVD $SiN_x$ film was decreased with increase in $NH_3/SiH_4$ gas ratio and RF power. After high temperature treatment process, the minority carrier lifetime of both low and high frequency PECVD $SiN_x$ film was increased and increased degree was similar. The minority carrier lifetime of low frequency PECVD $SiN_x$ was increased from $11.03{\mu}m$ to $28.24{\mu}m$ and that of high frequency PECVD $SiN_x$ was increased from $11.60{\mu}m$ to $27.10{\mu}m$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.280-284
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• 2004

Multicrystalline silicon wafers were textured in an alkaline bath, basically using sodium hydroxide and in acidic bath, using mainly hydrofluoric acid (HF), nitric acid $(HNO_3)$ and de-ionized water (DIW). Some wafers were also acid polished for the comparative study. Comparison of average reflectance of the samples treated with the new recipe of acidic solution showed average diffuse reflectance less than even 5 percent in the optimized condition. Solar cells were thus fabricated with the samples following the main steps such as phosphorus doping for emitter layer formation, silicon nitride deposition for anti-reflection coating by plasma enhanced chemical vapor deposition (PECVD) and front surface passivation, screen printing metallization, co-firing in rapid thermal processing (RTP) Furnace and laser edge isolation and confirmed >14 % conversion efficiency from the best textured samples. This isotropic texturing approach can be instrumental to achieve high efficiency in mass production using relatively low cost silicon wafers as starting material.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.77-80
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• 2003

Adsorption of glycine on$Si_3N_4$powder surface has been investigated, which is supposed to enhance the formation of passive layer inhibiting oxidation in aqueous solution. In the basic solution, multinuclear surface complexing between Si and dissociated ligands was responsible for the saturated adsorption of glycine. In addition, $CeO_2$-based CMP slurry containing glycine was manufactured and then applied to planarize$SiO_2$and$Si_3N_4$thin film. Owing to the passivation by glycine, the removal rates, Rh, were decreased, however, the selectivities, RE(SiO$_2$)/RR($Si_3N_4$), increased and showed maximum at pH=12. The suppressed oxidation and dissolution by adsorbate were correlated with the dissociation behavior of glycine at different pH and subsequent chemical adsorption.