• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.30A no.1
• /
• pp.16-22
• /
• 1993

A via-hole process for reproducible and reliable GaAs MMIC fabrication is described. The via-hole etching process consists of two step dry etching. During the first etching step a BC $I_{3}$/C $I_{2}$/Ar gas mixure is used to achieve high etch rate and small lateral etching. In the second etching step. CC $L_{2}$ $F_{2}$ gas is used to achieve selective etching of the GaAs substrate with respect to the front side metal layer. Via holes are formed from the backside of a 100$\mu$m thick GaAs substrate that has been evaporated initially with 500.angs. thick chromium and subsequently a 2000.angs. thick gold layer. The fabricated via holes are electroplated with gold (~20$\mu$m thick) to form via connections. The results show that established via-hole process is satisfactory for GaAs MMIC fabrication.

• Restorative Dentistry and Endodontics
• /
• v.38 no.2
• /
• pp.73-78
• /
• 2013

Objectives: This study evaluated the effect of three different air-drying times on microleakage of three self-etch adhesive systems. Materials and Methods: Class I cavities were prepared for 108 extracted sound human premolars. The teeth were divided into three main groups based on three different adhesives: Opti Bond All in One (OBAO), Clearfil $S^3$ Bond (CSB), Bond Force (BF). Each main group divided into three subgroups regarding the air-drying time: without application of air stream, following the manufacturer's instruction, for 10 sec more than manufacturer's instruction. After completion of restorations, specimens were thermocycled and then connected to a fluid filtration system to evaluate microleakage. The data were statistically analyzed using two-way ANOVA and Tukey-test (${\alpha}$ = 0.05). Results: The microleakage of all adhesives decreased when the air-drying time increased from 0 sec to manufacturer's instruction (p < 0.001). The microleakage of BF reached its lowest values after increasing the drying time to 10 sec more than the manufacturer's instruction (p < 0.001). Microleakage of OBAO and CSB was significantly lower compared to BF in all three drying time (p < 0.001). Conclusions: Increasing in air-drying time of adhesive layer in one-step selfetch adhesives caused reduction of microleakage, but the amount of this reduction may be dependent on the adhesive components of self-etch adhesives.

• Restorative Dentistry and Endodontics
• /
• v.32 no.3
• /
• pp.169-179
• /
• 2007

This study was to compare the microshear bond strength $({\mu}SBS)$ of light- and chemically cured composites to enamel coupled with four 2-step self-etch adhesives and also to evaluate the incompatibility between 2-step self-etch adhesives and chemically cured composite resin. Crown segments of extracted human molars were cut mesiodistally, and a 1 mm thickness of specimen was made. They were assigned to four groups by adhesives used: SE group (Clearfil SE Bond) AdheSE group (AdheSE), Tyrian group (Tyrian SPE/One-Step Plus), and Contax group (Contax) Each adhesive was applied to a cut enamel surface as per the manufacturer's instruction. Light-cured (Filtek Z250) or chemically cured composite (Luxacore Smartmix Dual) was bonded to the enamel of each specimen using a Tygon tube. After storage in distilled water for 24 hours, the bonded specimens were subjected to ${\mu}SBS$ testing with a crosshead speed of 1 mm/minute. The mean ${\mu}SBS$ (n=20 for each group) was statistically compared using two-way ANOVA, Tukey HSD, and t test at 95% level. Also the interface of enamel and composite was evaluated under FE-SEM. The results of this study were as follows ; 1. The ${\mu}SBS$ of the SE Bond group to the enamel was significantly higher than that of the AdheSE group, the Tyrian group, and the Contax group in both the light-cured and the chemically cured composite resin (p < 0.05). 2. There was not a significant difference among the hdheSE group, the Tyrian group, and the Contax group in both the light-cured and the chemically cured composite resin. 3. The ${\mu}SBS$ of the light-cured composite resin was significantly higher than that of the chemically cured composite resin when same adhesive was applied to the enamel (p < 0.05). 4. The interface of enamel and all 2-step self-etch adhesives showed close adaptation, and so the incompatibility of the chemically cured composite resin did not show.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.2
• /
• pp.117-122
• /
• 2001

In this paper, we report on photoelectrochemical etching process of 6H-SiC semiconductor wafer. The etching was performed in two-step process; anodization of SiC surface to form a deep porous layer and thermal oxidation followed by an HF dip. Etch rate of about 615${\AA}$/min was obtained during the anodization using a dilute HF(1.4wt% in H$_2$O) electrolyte with the etching potential of 3.0V. The etching rate was increased with the bias voltage. It was also found out that the adition of appropriate portion of H$_2$O$_2$ into the HF solution improves the etching rate. The etching process resulted in a higherly anisotropic etching characteristics and showed to have a potential for the fabrication of SiC devices with a novel design.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.4
• /
• pp.112-120
• /
• 1996

With the MOsES (mask oxide sidewall etch scheme)process which uses the conventional i-line stepper and isotropic wet etching, CMOSFET's with fine gate pattern of 0.1.mu.m CMOSFET device, the screening oxide is deposited before the low energy ion implantation for source/drain extensions and two step sidewall scheme is adopted. Through the characterization of 0.1.mu.m CMOSFET device, it is found that the screening oxide deposition sheme has larger capability of suppressing the short channel effects than two step sidewall schem. In cse of 200.angs.-thick screening oxide deposition, both NMOSFET and PMOSFET maintain good subthreshold characteristics down to 0.1.mu.m effective channel lengths, and show affordable drain saturation current reduction and low impact ionization rates.

• 한국태양에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.40-44
• /
• 2011

Recent studies in crystalline silicon solar cell fabrication have been focused on high efficiency and low cost. However, the rising of the cost results in additional processes to approach high efficiency. The fabrication process also becomes complicated with additional technologies. In this paper, we studied the selective emitter formation with phosphorous paste to improve the conversion efficiency. Selective emitter formations like two-step diffusion or etch-back method require at least one more step compared in the conventional line since heavily and lightly doped area was needed to form separately.However,one-step diffusion process is the method diffusing heavily and lightly doped area at the same time only with additional screen-printing step. This study lays the foundation for the simple way to form the selective emitter.

• Restorative Dentistry and Endodontics
• /
• v.30 no.4
• /
• pp.344-351
• /
• 2005

This study compared the microshear bond strength $({\mu}SBS)$ to end and side of enamel rod bonded by four adhesives including two total etch adhesives and two self-etch adhesives. Crown segments of extracted human molars were cut mesiodistally. The outer buccal or lingual surface was used as specimens cutting the ends of enamel rods, and inner slabs used as specimens cutting the sides of enamel rods. They were assigned to four groups by used adhesives: Group 1 (All-Bond 2), Group 2 (Single Bond), Group 3 (Tyrian SPE/One-Step Plus), Group 4 (Adper Prompt L-Pop). After each adhesive was applied to enamel surface, three composite cylinders were adhered to it of each specimen using Tygon tube. After storage in distilled water for 24 hours, the bonded specimens were subjected to ${\mu}SBS$ testing with a crosshead speed of 1 mm/minute. The results of this study were as follows: 1. The $({\mu}SBS)$ of Group 2 $(16.50\pm2.31 MPa)$ and Group 4 $(15.83\pm2.33 MPa)$ to the end of enamel prism was significantly higher than that of Group 1 $(11.93\pm2.25 MPa)$ and Group 3 $(11.97\pm2.05 MPa)$ (p<0.05). 2. The $({\mu}SBS)$ of Group 2 $(13.43\pm2.93 MPa)$ to the side of enamel prism was significantly higher than that of Group 1 $(8.64\pm1.53 MPa)$, Group 3 $(9.69\pm1.80 MPa)$, and Group 4 $(10.56 \pm1.75 MPa)$ (p<0.05), 3. The mean $({\mu}SBS)$ to the end of enamel rod was significantly higher than that to the side of enamel rod in all group (p<0.05).

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.406-406
• /
• 2010

일반적으로, 나노스케일의 MOS 소자에서는 게이트 절연체 두께가 감소함에 따라 tunneling effect의 증가로 인해 PID (plasma induced damage)로 인한 소자 특성 저하 현상을 감소하는 추세로 알려져 있다. 하지만 요즘 많이 사용되고 있는 high-k 게이트 절연체의 경우에는 오히려 더 많은 charge들이 trapping 되면서 PID가 오히려 더 심각해지는 현상이 나타나고 있다. 이러한 high-k 게이트 식각 시 현재는 주로 Hf-based wet etch나 dry etch가 사용되고 있지만 gate edge 영역에서 high-k 게이트 절연체의 undercut 현상이나 PID에 의한 소자특성 저하가 보고되고 있다. 본 연구에서는 이에 차세대 MOS 소자의 gate stack 구조중 issue화 되고 있는 metal gate 층과 gate dielectric 층의 식각공정에 각각 중성빔 식각과 중성빔 원자층 식각을 적용하여 전기적 손상 없이 원자레벨의 정확한 식각 조절을 해줄 수 있는 새로운 two step 식각 공정에 대한 연구를 진행하였다. 먼저 TiN metal gate 층의 식각을 위해 HBr과 $Cl_2$ 혼합가스를 사용한 중성빔 식각기술을 적용하여 100 eV 이하의 에너지 조건에서 하부층인 $HfO_2$와 거의 무한대의 식각 선택비를 얻었다. 하지만 100 eV 조건에서는 낮은 에너지에 의한 빔 스케터링으로 실제 패턴 식각시 etch foot이 발생되는 현상이 관찰되었으며, 이를 해결하기 위하여 먼저 높은 에너지로 식각을 진행하고 $HfO_2$와의 계면 근처에서 100 eV로 식각을 해주는 two step 방법을 사용하였다. 그 결과 anistropic 하고 하부층에 etch stop된 식각 형상을 관찰할 수 있었다. 다음으로 3.5nm의 매우 얇은 $HfO_2$ gate dielectric 층의 정확한 식각 깊이 조절을 위해 $BCl_3$와 Ar 가스를 이용한 중성빔 원자층 식각기술을 적용하여 $1.2\;{\AA}$/cycle의 단일막 식각 조건을 확립하고 약 30 cycle 공정시 3.5nm 두께의 $HfO_2$ 층이 완벽히 제거됨을 관찰할 수 있었다. 뿐만 아니라, vertical 한 식각 형상 및 향상된 표면 roughness를 transmission electron microscope(TEM)과 atomic force microscope (AFM)으로 관찰할 수 있었다. 이러한 중성빔 식각과 중성빔 원자층 식각기술이 결합된 새로운 gate recess 공정을 실제 MOSFET 소자에 적용하여 기존 식각 방법으로 제작된 소자 결과를 비교해 본 결과 gate leakage current가 약 one order 정도 개선되었음을 확인할 수 있었다.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.36 no.3
• /
• pp.348-357
• /
• 2009

The purpose of this study was to evaluate the micro-tensile bond strength (${\mu}TBS$) of four luting resin to regional dentin of human primary teeth. Dentin from non-carious primary molars were prepared from different regions (s, superficial dentin; d, deep dentin; c, cervical dentin), and divided into groups based on anatomical locations and types of luting resins (Scotchbond Multi-purpose : SB ; One-Step : OS ; AdheSE Bond : ASE ; G-Bond : GB) : SB-s, SB-d, SB-c; OS-s, OS-d, OS-c; ASE-s, ASE-d, ASE-c ; GB-s, GB-d, GB-c. Luting resins were used according to the manufacturers' instructions, to bond $Light-Core^{TM}$ Core Build-Up Composite) to the exposed dentin specimens in the light-curing mode. After storage for 1 day, ${\mu}TBS$ was tested at a cross-head speed of 1 mm/min. Data were analyzed with T-test and two-way ANOVA. The bonding interface and fractography analyses were performed with SEM. The results were as follows : 1. ${\mu}TBS$ to superficial dentin was significantly higher than to deep dentin for SB(p<0.05). But there were no significant differences in regional ${\mu}TBS$ among OS, ASE, GB(p>0.05). 2. There were no significant differences in ${\mu}TBS$ to superficial dentin among each groups. But, in deep dentin, ${\mu}TBS$ of SB-d was significantly lower than those of OS-d, ASE-d, and GB-d(p<0.05). ${\mu}TBS$ of OS-d was significantly higher than those of GB-d(p<0.05), but there were no significant differences in ${\mu}TBS$ of ASEd. There were no significant differences among ${\mu}TBS$ of ASE-d, OS-d, and GB-d.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.7
• /
• pp.50-57
• /
• 1989

Tapered etching of polysilicon films has been achieved by implanting phosphorus ions into the polysilicon film and using plasma etch in either $CF_4-O_2\;or\;SF_6$. A two-step plasma etching method is also proposed to control the taper angle of the etched edge without changing the implantion conditions. The taper angle is determined by the ratio of the etch rate of the undamaged region to that of the damaged top region of the polysilicon layer. The ratio is found to be dependent on the implantion dose, the implantion energy and the anisotropy of etching. The minimum angle in our experiments is about $10^{\circ}$. When the two-step etching method is employed, the taper angles can be controlled from the minimum angle up to about $55^{\circ}$.