• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.6
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• pp.691-699
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• 2012

In this paper, we present a Vt-DRO with a low phase noise, which is achieved by improving the coupling structure between the dielectric resonator and microstrip line. The Vt-DRO is a closed-loop type and is composed of 3 blocks; dielectric resonator, phase shifter, and amplifier. We propose a mathematical estimation method of phase noise, using the group delay of the resonator. By modifying the coupling structure between the dielectric resonator and microstrip line, we achieved a group delay of 53 nsec. For convenience of measurement, wafer probes were inserted at each stage to measure the S-parameters of each block. The measured S-parameter of the Vt-DRO satisfies the open-loop oscillation condition. The Vt-DRO was implemented by connecting the input and output of the designed open-loop to form a closed-loop. As a result, the phase noise of the Vt-DRO was measured as -132.7 dBc/Hz(@ 100 kHz offset frequency), which approximates the predicted result at the center frequency of 5.3 GHz. The tuning-range of the Vt-DRO is about 5 MHz for tuning voltage of 0~10 V and the power is 4.5 dBm. PFTN-FOM is -31 dBm.

• Korean Journal of Ecology and Environment
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• v.36 no.1 s.102
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• pp.66-73
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• 2003

Field experimental study was performed to evaluate water and nutrient balances in paddy rice culture. The water balance showed that outflow generally balanced the inflow showing that about half (47${\sim}$54%) of total outflow was lost by surface drainage. No significant effect of fertilization rate was observed from three treatments (150%, 100%, and 70% of standard fertilization) on both rice yield and nutrient outflow from surface drainage. Therefore, reducing nonpoint source nutrient loading by reducing fertilization may not work well in the range of normal paddy rice farming practice, and instead it could be achieved by reducing surface drainage outflow. Water-saving irrigation by reducing pending depth, raising ridge height in rice field, and minimizing forced surface drainage are suggested to reduce surface drainage outflow. These practices can save water and protect water quality, however, deviation from conventional standard practices might affect the rice yield and further investigations are necessary. It was demonstrated that rainfall affects nutrient net outflow and paddy rice culture might be beneficial to wafer quality protection under normal rainfall condition.

• Clean Technology
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• v.23 no.4
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• pp.357-363
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• 2017

In this study, the supercritical carbon dioxide ($scCO_2$)/ n-butyl acetate (n-BA) co-solvent system was employed to remove an unexposed negative photoresist (PR) from the surface of a silicon wafer. In addition, the selectivity of the $scCO_2$/n-BA co-solvent system was confirmed for the unexposed and exposed negative PR. Optimum conditions for removal of the unexposed PR were obtained from various conditions such as pressure, temperature and n-BA ratio. The n-BA was highly soluble in $scCO_2$ without cloud point and phase separation in mostly experimental conditions. However, the $scCO_2$/n-BA co-solvent was phase separated at 100 bar, above $80^{\circ}C$. The unexposed and exposed PR was swelled in $scCO_2$ solvent at all experimental conditions. The complete removal of unexposed PR was achieved from the reaction condition of 160 bar, 10 min, $40^{\circ}C$ and 75 wt% n-BA in $scCO_2$, as measured by ellipsometry. The exposed photoresist showed high stability in the $scCO_2$/n-BA co-solvent system, which indicated that the $scCO_2$/n-BA co-solvent system has high selectivity for the PR removal in photo lithograph process. The $scCO_2$/n-BA co-solvent system not only prevent swelling of exposed PR, but also provide efficient and powful performance to removal unexposed PR.

• Safety and Health at Work
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• v.2 no.3
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• pp.210-217
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• 2011

Objectives: The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemicals used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories. Methods: A total of four photolithography processes in 4 Fabs at three different semiconductor manufacturing factories in Korea were selected for this study. This study investigated the types of chemicals used and generated during the photolithography process of each Fab, and the concentration levels of VOCs for each Fab. Results: A variety of organic compounds such as ketone, alcohol, and acetate compounds as well as aromatic compounds were used as solvents and developing agents in the processes. Also, the generation of by-products, such as toluene and phenol, was identified through a thermal decomposition experiment performed on a photoresist. The VOC concentration levels in the processes were lower than 5% of the threshold limit value (TLV)s. However, the air contaminated with chemical substances generated during the processes was re-circulated through the ventilation system, thereby affecting the airborne VOC concentrations in the photolithography processes. Conclusion: Tens of organic compounds were being used in the photolithography processes, though the types of chemical used varied with the factory. Also, by-products, such as aromatic compounds, could be generated during photoresist patterning by exposure to light. Although the airborne VOC concentrations resulting from the processes were lower than 5% of the TLVs, employees still could be exposed directly or indirectly to various types of VOCs.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.23-34
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• 1992

In order to fabricate magnetoresistive sensor, Fe-Ni and Co-Ni alleys were evaporated on the slide glass and the silicon wafers. Saturation magnetic induction($B_{s}$), coercive field strength($H_{c}$) and magnetoresistance were measured for fabricated samples. The evaporated Fe-Ni thin films show that the saturation magnetic induction was 0.65 T, and coercive field strength was 0.379 A/cm, and this value was changed to 0.370 A/cm(//), 0.390 A/cm(${\bot}$), respectively after magnetic annealing. For the measurement of coercive field strength, magnetizing frequency of 1 kHz was used. For the fabricated sensor element, the change of magnetoresistance (${\Delta}R/R$) was excessively unstable due to oxidation in the process of fabrication. The evaporated Co-Ni alloy thin films show that saturation magnetic induction was 0.66 T, and coercive field strengthes were 5.895 A/cm(//), 5.898 A/cm(${\bot}$), respectively, after magnetic annelaing. The change of magnetoresistance(${\Delta}R/R$) was $3.6{\sim}3.7%$ of which value was excessively stable to room temperature. Fe-Ni thin film could have many problems due to large affinity in the process of fabrication of magnetoresistance sensor, but Co-Ni thin film could be a suitable material for fabrication of magnetoresistance sensor, because of its small affinity and definite magnetoresistance effects.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.81-86
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• 2004

A new method to improve the wet etching characteristics is described. The anisotropic wet-etching of (100) Si with megasonic wave has been studied in KOH solution. Etching characteristics of p-type (100) 6 inch Si have been explored with and without megasonic irradiation. It has been observed that megasonic irradiation improves the characteristics of wet etching such as an etch uniformity and surface roughness. The etching uniformity on the whole wafer with and without megasonic irradiation were less than ${\pm}1\%$ and more than $20\%$, respectively. The initial root-mean-square roughness($R_{rms}$) of single crystal silicon is 0.23 nm. It has been reported that the roughnesses with magnetic stirring and ultrasonic agitation were 566 nm and 66 nm, respectively. Comparing with the results, etching with megasonic irradiation achieved the Rrms of 1.7 nm on the surface after the $37{\mu}m$ of etching depth. Wet etching of silicon with megasonic irradiation can maintain nearly the original surface roughness after etching process. The results have verified that the megasonic irradiation is an effective way to improve the etching characteristics such as etch uniformity and surface roughness.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.47-51
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• 2006

Recently, CMP (Chemical Mechanical Polishing) is one of very important processing in semiconductor technology because of large integration and application of design role. CMP is a planarization process of wafer surface using the chemical and mechanical reactions. One of the most important components of the CMP system is the polishing pad. During the CMP process, the pad itself becomes smoother and glazing. Therefore it is necessary to have a pad conditioning process to refresh the pad surface, to remove slurry debris and to supply the fresh slurry on the surface. A conditioning disk is used during the pad conditioning. There are diamonds on the surface of diamond disk to remove slurry debris and to polish pad surface slightly, so density, shape and size of diamond are very important factors. In this study, we characterized diamond disk with 9 kinds of sample.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.79-84
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• 2010

Formation of TSV (Through-Si-Via) with an Au seed layer and Cu filling to the via, simplification of bumping process for three dimensional stacking of Si dice were investigated. In order to produce the via holes, the Si wafer was etched by a DRIE (Deep Reactive Ion Etching) process using $SF_6$ and $C_4F_8$ plasmas alternately. The vias were 40 ${\mu}m$ in diameter, 80 ${\mu}m$ in depth, and were produced by etching for 1.92 ks. On the via side wall, a dielectric layer of $SiO_2$ was formed by thermal oxidation, and an adhesion layer of Ti, and a seed layer of Au were applied by sputtering. Electroplating with pulsed DC was applied to fill the via holes with Cu. The plating condition was at a forward pulse current density of 1000 mA/$dm^2$ for 5 s and a reverse pulse current density of 190 mA/$dm^2$ for 25 s. By using these parameters, sound Cu filling was obtained in the vias with a total plating time of 57.6 ks. Sn bumping was performed on the Cu plugs without lithography process. The bumps were produced on the Si die successfully by the simplified process without serious defect.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.3
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• pp.116-120
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• 2006

We have investigated plasma spray coated $Al_2O_3$ layers on Al-60 series substrates for development of wafer electrostatic chuck in semiconductor dry etching system. Samples were prepared without/with cooling bar on backside of samples, at various distances, and with different powder feed rates. There were many cracks and pores in the $Al_2O_3$ layers coated on Al-60 series substrates without cooling bar on the backside of samples. But the cracks and pores were almost disappeared in the $Al_2O_3$ layers on Al-60 series substrates coated with cooling bar on the back side of samples, 15 g/min. powder feed rate and various 60, 70, 80 mm working distances. Then the surface morphology was not changed with various working distances of 60, 70, 80 mm. When the powder feed rate was changed from 15 g/min to 20 g/min, the crack did not appear, but few pores appeared. Also the $Al_2O_3$ layer was coated with many small splats compared with $Al_2O_3$ layer coated with 15 g/min powder feed rate. The deposited rate of $Al_2O_3$ layer was higher when the process was done without cooling bar on the back side of sample than that with cooling bar on the back side of sample.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.79-93
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• 1991

With the advent of ULSI, many problems in previous metallization techniques and interconnection materials have become more serious. In this work, selective deposition of copper to fill the submicron contact has been tried. After forming electro-deposited copper films on p-type (100) silicon wafer using 0.75M $CuSO_4{\cdot}$5H_2O$ as an electrolyte, the effect of deposition time, current density and concentration of an additive on film properties were investigated. Film thickness, particle size and resistivity were analyzed by Alpha Step, SEM and 4 - point probe measurement respectively. The deposition rate was about $0.5-0.6\mu\textrm{m}$/min at $2A/dm^2$ and the particle size increased with increasing current density. The resistivities of electro-deposited copper films were about $3-6{\mu}{\Omega}{\cdot}$cm for the particle size above $4000{\AA}$. By the addition of 0.2 g/l gelatin, the particle size was reduced to less than $0.1{\mu}m $ and selective plugging of copper on submicron contacts could be successfully achieved.