• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.101-106
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• 2009

In this paper, Thin films of $HfO_2$/Hf were deposited on p-type wafer by Atomic Layer Deposition (ALD). We studied the electrical and material characteristics of $HfO_2$/Hf/Si MOS capacitor depending on thickness of Hf metal layer. $HfO_2$ films were deposited using TEMAH and $O_3$ at $350^{\circ}C$. Samples were then annealed using furnace heating to $500^{\circ}C$. Round-type MOS capacitors have been fabricated on Si substrates with $2000\;{\AA}$-thick Pt top electrodes. The composition rate of the dielectric material was analyzed using TEM (Transmission Electron Microscopy), XRD (X-ray Diffraction) and XPS (X-ray Photoelectron Spectroscopy). Also the capacitance-voltage (C-V), conductance-voltage (G-V), and current-voltage (I-V) characteristics were measured. We calculated the density of oxide trap charges and interface trap charges in our MOS device. At the interface between $HfO_2$ and Si, both Hf-Si and Hf-Si-O bonds were observed, instead of Si-O bond. The sandwiched Hf metal layer suppressed the growing of $SiO_x$ layer so that $HfSi_xO_y$ layer was achieved. And finally, the generation of both oxide trap charge and interface trap charge in $HfO_2$ film was reduced effectively by using Hf metal layer.

• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.383-387
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• 2023

The quartz crystal microbalance (QCM), commonly used in high vacuum deposition, becomes difficult to use when a thick film is deposited on the quartz, affecting the crystal's inherent vibration. In this study, a non-destructive optical measurement method was developed to measure the film's deposition rate during the in-situ film deposition process. By measuring the scattered laser intensity caused by the dimer in the parylene gas passing through the gas flow path, it was successfully confirmed that the ratio of the dimer in the parylene gas increases as the pyrolysis temperature decreases. Additionally, it was noted that the film's thickness and haze increase as the pyrolysis temperature decreases by confirming the characteristics of the visible parylene films. Through the research results, we aim to utilize the stable in-situ film deposition rate measurement system to control the precise film deposition rate of parylene films.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.195-200
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• 1998

We have investigated the crystal structure and electrical properties of Pt/SBT/$CeO_2$/Si(MFIS) and Pt/SBT/Si(MFS) structures for the gate oxide of ferroelectric memory. XRD spectra and SEM showed that the SBT film of SBT/$CeO_2$/Si structure had larger grain than that of SBT/Si structure. Furthermore HRTEM showed that SBT/$CeO_2$/Si had 5 nm thick $SiO_2$layer and very smooth interface but SBT/Si had 6nm thick $SiO_2$layer and 7nm thick amorphous intermediate interface. Therefore, $CeO_2$film between SBT film and Si substrate is confirmed as a good candidate for a diffusion barrier. The remanent polarization decreased and coercive voltage increased in Pt/SBT/$CeO_2/Pt/SiO_2$/Si structure. This effect may increase memory window of MFIS structure directly related to the coercive voltage. From the capacitance-voltage characteristics, the memory of Pt/SBT(140 nm)/$CeO_2$(25 nm)/Si structure were in the range of 1~2 V at the applied voltage of 4~6 V. The memory window increased with the thickness of SBT film. These results may be due to voltage applied at SBT films. The leakage currents of Pt/SBT/$CeO_2$/Si and Pt/SBT/Si were $ 10^8A/\textrm{cm}^2$ and $ 10^6 A/\textrm{cm}^2$, respectively.

• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.163-170
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• 2002

This paper proposes a $10\;{\mu}m$ thick oxide air-bridge structure which can be used as a substrate for RF circuits. The structure was fabricated by anodic reaction, complex oxidation and micromachining technology using TMAH etching. High quality films were obtained by combining low temperature thermal oxidation ($500^{\circ}C$, 1 hr at $H_2O/O_2$) and rapid thermal oxidation (RTO) process ($1050^{\circ}C$, 2 min). This structure is mechanically stable because of thick oxide layer up to $10\;{\mu}m$ and is expected to solve the problem of high dielectric loss of silicon substrate in RF region. The properties of the transmission line formed on the oxidized porous silicon (OPS) air-bridge were investigated and compared with those of the transmission line formed on the OPS layers. The insertion loss of coplanar waveguide (CPW) on OPS air-bridge was (about 2dB) lower than that of CPW on OPS layers. Also, the return loss of CPW on OPS air-bridge was less than about -20 dB at measured frequency region for 2.2 mm. Therefore, this technology is very promising for extending the use of CMOS circuitry to higher RF frequencies.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.183-184
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• 2013

Two main MBE growth techniques have been used: plasma-assisted MBE (PA-MBE), which utilizes a rf plasma to supply active nitrogen, and ammonia MBE, in which nitrogen is supplied by pyrolysis of NH3 on the sample surface during growth. PA-MBE is typically performed under metal-rich growth conditions, which results in the formation of gallium droplets on the sample surface and a narrow range of conditions for optimal growth. In contrast, high-quality GaN films can be grown by ammonia MBE under an excess nitrogen flux, which in principle should result in improved device uniformity due to the elimination of droplets and wider range of stable growth conditions. A drawback of ammonia MBE, on the other hand, is a serious memory effect of NH3 condensed on the cryo-panels and the vicinity of heaters, which ruins the control of critical growth stages, i.e. the native oxide desorption and the surface reconstruction, and the accurate control of V/III ratio, especially in the initial stage of seed layer growth. In this paper, we demonstrate that the reliable and reproducible growth of GaN on Si (110) substrates is successfully achieved by combining two MBE growth technologies using rf plasma and ammonia and setting a proper growth protocol. Samples were grown in a MBE system equipped with both a nitrogen rf plasma source (SVT) and an ammonia source. The ammonia gas purity was ＞99.9999% and further purified by using a getter filter. The custom-made injector designed to focus the ammonia flux onto the substrate was used for the gas delivery, while aluminum and gallium were provided via conventional effusion cells. The growth sequence to minimize the residual ammonia and subsequent memory effects is the following: (1) Native oxides are desorbed at $750^{\circ}C$ (Fig. (a) for [$1^-10$] and [001] azimuth) (2) 40 nm thick AlN is first grown using nitrogen rf plasma source at $900^{\circ}C$ nder the optimized condition to maintain the layer by layer growth of AlN buffer layer and slightly Al-rich condition. (Fig. (b)) (3) After switching to ammonia source, GaN growth is initiated with different V/III ratio and temperature conditions. A streaky RHEED pattern with an appearance of a weak ($2{\times}2$) reconstruction characteristic of Ga-polarity is observed all along the growth of subsequent GaN layer under optimized conditions. (Fig. (c)) The structural properties as well as dislocation densities as a function of growth conditions have been investigated using symmetrical and asymmetrical x-ray rocking curves. The electrical characteristics as a function of buffer and GaN layer growth conditions as well as the growth sequence will be also discussed. Figure: (a) RHEED pattern after oxide desorption (b) after 40 nm thick AlN growth using nitrogen rf plasma source and (c) after 600 nm thick GaN growth using ammonia source for (upper) [110] and (lower) [001] azimuth.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.988-996
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• 1995

CuInSe$_2$this films as a light absorber layer were fabricated by vacuum evaporation using In$_2$Se$_3$and Cu$_2$Se precursors and their properties were analyzed. Indium selenide films of 0.5${\mu}{\textrm}{m}$ thickness were first deposited by vacuum evaporation of In$_2$Se$_3$ on a Corning 7059 glass substrate. The films deposited at suscepor temperature of 40$0^{\circ}C$ showed a flat surface morphology with densely Packed grain structure. CuInSe$_2$films directly formed by evaporating Cu$_2$Se on the predeposited In$_2$Se$_2$films also showed a very flat surface when the susceptor temperature was $700^{\circ}C$. Cu$_2$Se, a second phase in the CuInSe$_2$film, was removed by evaporating additional In$_2$Se$_3$on the CuInSe$_2$film at $700^{\circ}C$. The grain size of 1.2${\mu}{\textrm}{m}$ thick CuInSe$_2$, film was about 2${\mu}{\textrm}{m}$ and the film had a (112) preferred orientation. As the amount of deposited In$_2$Se$_3$increased, the electrical resistivity of CuInSe$_2$films increased because of the decrease of hole concentration. But the optical band gap was almost constant at the value of 1.04eV, The CuInSe$_2$film grown on a Mo/glass substrate had a similar smooth microstructure compared to that on a glass substrate. A solar cell with ZnO/CdS/CuInSe$_2$/Mo structure may be realized based on the above CuInSe$_2$films.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1541-1543
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• 1999

Screen printing에 의해 압전 후막을 제조하기 위하여 약 $0.6{\mu}m$의 평균 입자 크기를 갖는 PMN-PZT와 PAN-PZT 분말을 산화물 혼합법에 의해 제조하였다. 치밀한 후막의 제조를 위한 분말과 유기물의 비율은 분산이 가능한 범위에서 80:20 (분말:유기물)의 중량비를 나타내었다 사용된 기판과 하부전극은 각각 $SiO_2$/Si와 AgPd 였으며, 후막 제조시 박리 및 균열현상은 발생되지 않았다. 프린트된 후막은 건조온도와 무관한 미세구조를 나타내었으며, 보다 치밀한 구조를 갖는 후막의 제조를 이해 입자의 분산 및 열처리 조건 그리고 기판과의 매칭에 대해 연구가 계속되어야 할 것으로 생각된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4925-4929
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• 2015

Dye-sensitized solar cell(DSSC) has aroused intense interest owing to its competitive price and stabilized properties than Si based solar cells. Recently, many studies have been reported on the DSSC, especially development of a transparent conductive oxide-less dye-sensitized solar cell(TCO-less DSSC). In this paper, a thick and porous Ti electrode for low cost DSSC developed its properties. To estimate the Ti electrode, the films are tested FESEM and J-V evaluation method. An increase in Ti thickness from 50 nm to 200 nm mainly affects the fill factor without noticeably changing the photocurrent density. It was confirmed that optimal DSSC efficiency was obtained at Ti 150 nm.

• Electrical & Electronic Materials
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• v.16 no.9
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• pp.63.1-63
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• 2003

Catalytic chemical vapor deposition (Cat-CVD) has been developed to deposit alumina(Al$_2$O$_3$) thin films on silicon (Si) crystal using N$_2$ bubbled tir-methyl aluminium [Al(CH$_3$)$_3$, TMA] and molecular oxygen (O$_2$) as source species and tungsten wires as a catalyzer. The catalyzer dissociated TMA at approximately 600$^{\circ}C$ The maximum deposition rate was 18 nm/min at a catalyzer temperature of 1000 and substrate temperature of 800$^{\circ}C$. Metal oxide semiconductor (MOS) diodes were fabricated using gates composed of 32.5-nm-thick alumina film deposited as a substrate temperature of 400oC. The capacitance measurements resulted in a relatively dielectric constant of 7, 4, fixed charge density of 1.74*10e12/$\textrm{cm}^2$, small hysteresis voltage of 0.12V, and very few interface trapping charge. The leakage current was 5.01*10e-7 A/$\textrm{cm}^2$ at a gate bias of 1V.

• Advances in pediatric surgery
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• v.1 no.2
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• pp.177-180
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• 1995

A 2-day-old male (Premie, Large for gestational age(LGA), Intrauterine period(IUP) 33 weeks, birth weight 2,955 gram) was transferred with marked abdominal distention, bilious return via the orogastric tube, respiratory difficulty, and generalized edema (hydrops fetalis). He was born by cesarean section to a 36 year-old mother. Antenatal ultrasonogram at IUP 31 weeks demonstrated multiple dilated bowel loops suggestive of intestinal obstruction. There was no family history of cystic fibrosis. Simple abdominal films disclosed diffuse haziness and suspicious fine calcifications in the right lower quadrant. Barium enema demonstrated a microcolon. Sweat chloride test was not available in our institution. At laparotomy, there noted 1) a segmental volvulus of the small bowel with gangrenous change, associated with meconium peritonitis, 2) an atresia of the ileum at the base of the volvulus, and 3) the terminal ileum distal to the volvulus was narrow and impacted with rabbit pellets-like thick meconium. These findings appeared to be very similar to those of a complicated meconium ileus. In summary, the ileal atresia and meconium peritonitis seemed to be caused by antenatal segmental volvulus of the small intestine in a patient with probable meconeum ileus.