• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.53-53
• /
• 2011

As the dimension of Cu interconnects has continued to reduce, its resistivity is expected to increase at the nanoscale due to increased surface and grain boundary scattering of electrons. To suppress increase of the resistivity in nanoscale interconnects, alloying Cu with other metal elements such as Al, Mn, and Ag is being considered to increase the mean free path of the drifting electrons. The formation of Al alloy with a slight amount of Cu broadly studied in the past. The study of Cu alloy including a very small Al fraction, by contrast, recently began. The formation of Cu-Al alloy is limited in wet chemical bath and was mainly conducted for fundamental studies by sputtering or evaporation system. However, these deposition methods have a limitation in production environment due to poor step coverage in nanoscale Cu metallization. In this work, gap-filling of Cu-Al alloy was conducted by cyclic MOCVD (metal organic chemical vapor deposition), followed by thermal annealing for alloying, which prevented an unwanted chemical reaction between Cu and Al precursors. To achieve filling the Cu-Al alloy into sub-100nm trench without overhang and void formation, furthermore, hydrogen plasma pretreatment of the trench pattern with Ru barrier layer was conducted in order to suppress of Cu nucleation and growth near the entrance area of the nano-scale trench by minimizing adsorption of metal precursors. As a result, superconformal gap-fill of Cu-Al alloy could be achieved successfully in the high aspect ration nanoscale trenches. Examined morphology, microstructure, chemical composition, and electrical properties of superfilled Cu-Al alloy will be discussed in detail.

• Journal of the Semiconductor & Display Technology
• /
• v.6 no.2 s.19
• /
• pp.19-23
• /
• 2007

The blue emitting OLEDs using TMP-BiP[(4'-Benzoylferphenyl-4-yl)phenyl-methanone-Diethyl(biphenyl-4-ymethyl) phosphonate] host and DJNBD-1 dopant have been fabricated and characterized. In the device fabrication, 2-TNATA [4,4',4"-tris(2-naphthylphenyl-phenylamino)-triphenylamine] as a hole injection material and NPB [N,N'-bis(1-naphthyl)N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as a hole transport material were deposited on the ITO(indium tin oxide)/glass substrate by vacuum thermal evaporation method. Followed by the deposition, blue color emission layer was deposited using TMP-BiP as a host material and DJNBD-1 as a dopant. Finally, small molecule OLEDs with structure of $ITO/2-TNATA/NPB/TMP-BiP:DJNBD-l/Alq_3/LiF/Al$ were obtained by in-situ deposition of $Alq_3$, LiF and Al as the electron transport material, electron injection material and cathode, respectively. The effect of dopant into host material of the blue OLEDs was studied. The blue OLEDs with DJNBD-1 dopant showed that the maximum current and luminance were found to be about 34 mA and $8110\;cd/m^2$ at 11 V, respectively. In addition, the color coordinate was x=0.17, y=0.17 in CIE color chart, and the peak emission wavelength was 440 nm. The maximum current efficiency of 2.15 cd/A at 7 V was obtained in this experiment.

• Journal of Information Display
• /
• v.4 no.2
• /
• pp.1-6
• /
• 2003

In this paper, we demonstrate that the organic electrophosphorescent device is driven by the organic thin film transistor with spin-coated photoacryl gate insulator. It was found that electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure showed the non-saturated slope in the saturation region and the sub-threshold nonlinearity in the triode region, where we obtained the maximum power luminance that was about 90 $cd/m^2$. Field effect mobility, threshold voltage, and on-off current ratio in 0.45 ${\mu}m$ thick gate dielectric layer were 0.17 $cm^2/Vs$, -7 V, and $10^6$ , respectively. In order to form polyimide as a gate insulator, vapor deposition polymerization process was also introduced instead of spin-coating process, where polyimide film was co-deposited by high-vacuum thermal evaporation from 4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-oxydianiline (ODA) and cured at 150${\sqsubset}$for 1hr. It was also found that field effect mobility, threshold voltage, on-off current ratio, and sub-threshold slope with 0.45 ${\mu}m$ thick gate dielectric films were 0.134 $cm^2/Vs$, -7 V, and $10^6$ A/A, and 1 V/decade, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.506-508
• /
• 2005

In general, organic TFTs are comprised of four components: gate electrode, gate dielectric, organic active semiconductor layer, and source and drain contacts. The TFT current, in turn, is typically determined by channel length and width, carrier field effect mobility, gate dielectric thickness and permittivity, contact resistance, and biasing conditions. More recently, a number of techniques and processes have been introduced to the fabrication of OTFT circuits and displays that aim specifically at reduced fabrication cost. These include microcontact printing for the patterning of metals and dielectrics, the use of photochemically patterned insulating and conducting films, and inkjet printing for the selective deposition of contacts and interconnect pattern. In the fabrication of organic TFTs, microcontact printing has been used to pattern gate electrodes, gate dielectrics, and source and drain contacts with sufficient yield to allow the fabrication of transistors. We were fabricated a pentacene OTFTs on flexible PEN film. Au/Cr was used for the gate electrode, parylene-c was deposited as the gate dielectric, and Au/Cr was chosen for the source and drain contacts; were all deposited by ion-beam sputtering and patterned by microcontact printing and lift-off process. Prior to the deposition of the organic active layer, the gate dielectric surface was treated with octadecyltrichlorosilane(OTS) from the vapor phase. To complete the device, pentacene was deposited by thermal evaporation and patterned using a parylene-c layer. The device was shown that the carrier field effect mobility, the threshold voltage, the subthreshold slope, and the on/off current ratio were improved.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.05a
• /
• pp.28.1-28.1
• /
• 2009

The superior properties of ZnO such as high exciton binding energy, high thermal and chemical stability, low growth temperature and possibility of wet etching process in ZnO have great interest for applications ranging from optoelectronics to chemical sensor. Particularly, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. Currently, low-dimensional ZnO is synthesized by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), thermal evaporation, and sol.gel growth. Recently, our group has been reported about achievement the growth of Ga-doped ZnO nanorods using ZnO seed layer on p-type Si substrate by RF magnetron sputtering system at high rf power and high growth temperature. However, the crystallinity of nanorods deteriorates due to lattice mismatch between nanorods and Si substrate. Also, in the growth of oxide using sputtering, the oxygen flow ratio relative to argon gas flow is an important growth parameter and significantly affects the structural properties. In this study, Phosphorus (P) doped ZnO nanorods were grown on c-sapphire substrates without seed layer by radio frequency magnetron sputtering with various argon/oxygen gas ratios. The layer change films into nanorods with decreasing oxygen partial pressure. The diameter and length of vertically well-aligned on the c-sapphire substrate are in the range of 51-103 nm and about 725 nm, respectively. The photoluminescence spectra of the nanorods are dominated by intense near band-edge emission with weak deep-level emission.

• Journal of the Korean Ceramic Society
• /
• v.39 no.9
• /
• pp.896-901
• /
• 2002

Since many process parameters of FHD(Flame Hydrolysis Deposition) are involved in forming multi-component amorphous silica film ($SiO_2-B_2O_3-P_2O_5-GeO_2$), it has not been easy to predict the optical, mechanical and thermal properties of deposited film from the simple process parameters, such as source flow rate. Furthermore, the prediction of final composition of film becomes even more difficult after sintering at high temperature due to the evaporation of volatile dopants. The motivation of the study was to clarify the quantitative relationship between simple process parameters such as the flow rate of source gases and resulting chemical composition of sintered film. Hence, the compositional analysis of silica soot by FTIR(Fourier Transformation Infrared Spectroscopy) and ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectrometry) under the control of the amount of dopant was carried out to obtain the quantitative composition. By measuring spectrum of absorbance from FTIR, the compositional change of B-O, Si-O, OH($H_2O$) in silica film was measured. The concentrations of these dopants were also measured by ICP-AES, which were compared with the FTIR result. The final quantitative relationship between simple process parameters and composition was deduced from the comparison between two results.

• Journal of IKEEE
• /
• v.20 no.4
• /
• pp.337-343
• /
• 2016

This study conducted the gamma ray spectroscopic analysis of the microcolumnar CsI:Tl deposited onto the SiPMs using thermal evaporation deposition. The SEM measured thickness of microcolumnar CsI:Tl and of its individual columns. From the SEM observation, the measured thickness of CsI:Tl were $450{\mu}m$ and $600{\mu}m$. The gamma ray spectroscopic properties of microcolumnar CsI:Tl, $450{\mu}m$ and $600{\mu}m$ thick deposited onto the SiPMs were analyzed using standard gamma ray sources $^{133}Ba$ and $^{137}Cs$. The spectroscopic analysis of microcolumnar CsI:Tl deposited onto the SiPMs included the measurements of response linearity over the $^{137}Cs$ gamma ray intensity; and gamma ray energy spectrum. Furthermore from the gamma ray spectrum measurement of $^{133}Ba$ and $^{137}Cs$, $450{\mu}m$ thick CsI:Tl showed good efficiency when measured with $^{133}Ba$ and $600{\mu}m$ thick CsI:Tl was highly efficient when measured with $^{137}Cs$.

• Journal of Sensor Science and Technology
• /
• v.8 no.2
• /
• pp.115-123
• /
• 1999

A micro-gas sensor with heater and sensing electrode on the same plane was fabricated on phosphosilicate glass(PSG, 800nm)/$Si_3N_4$ (150nm) dielectric membrane. PSG film was provided by atmospheric pressure chemical vapor deposition(APCVD), and $Si_3N_4$ film by low pressure chemical vapor deposition (LPCVD). Total area of the fabricated device was $3.78{\times}3.78mm^2$. The area of diaphragm was $1.5{\times}1.5mm^2$, and that of the sensing layer was $0.24{\times}0.24mm^2$. Finite-element simulation was employed to estimate temperature distribution for a square-shaped diaphragm. The power consumption of Pt heater was about 85mW at $350^{\circ}C$. Tin thin films were deposited on the silicon substrate by thermal evaporation at room temperature and $232^{\circ}C$, and tin oxide films($SnO_2$) were prepared by thermal oxidation of the metallic tin films at $650^{\circ}C$ for 3 hours in oxygen ambient. The film analyses were carried out by SEM and XRD techniques. Effects of humidity and ambient temperature on the resistance of the sensing layer were found to be negligible. The fabricated micro-gas sensor exhibited high sensitivity to butane gas.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2012.05a
• /
• pp.65-65
• /
• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.10
• /
• pp.3368-3372
• /
• 2012

The $Bi_2O_3$ nanowires are highly sensitive to low concentrations of $NO_2$ in ambient air and are almost insensitive to most other common gases. However, it still remains a challenge to enhance their sensing performance and detection limit. This study examined the influence of the encapsulation of ${\beta}-Bi_2O_3$ nanorods with $In_2O_3$ on the $NO_2$ gas sensing properties. ${\beta}-Bi_2O_3-core/In_2O_3-shell$ nanorods were fabricated by a two-step process comprising the thermal evaporation of $Bi_2O_3$ powders and sputter-deposition of $In_2O_3$. Multiple networked ${\beta}-Bi_2O_3-core/In_2O_3-shell$ nanorod sensors showed the responses of 12-156% at 1-5 ppm $NO_2$ at $300^{\circ}C$. These response values were 1.3-2.7 times larger than those of bare ${\beta}-Bi_2O_3$ nanorod sensors at 1-5 ppm $NO_2$. The enhancement in the response of ${\beta}-Bi_2O_3$ nanorods to $NO_2$ gas by the encapsulation by $In_2O_3$ can be accounted for based on the space-charge model.