• Journal of electromagnetic engineering and science
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• v.18 no.2
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• pp.101-107
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• 2018

The impedance bandwidth and radiation characteristics of an aperture-coupled microstrip line-fed patch antenna (ACMPA) with a high permittivity (${\varepsilon}_r=10$) feed substrate suitable for integration with a monolithic microwave integrated circuit (MMIC) are investigated for various feed substrate thicknesses through an experiment and computer simulation. The impedance bandwidth of an ACMPA with a high permittivity feed substrate increases as the feed substrate thickness decreases. Furthermore, the front-to-back ratio of an ACMPA with a high permittivity feed substrate increases and the cross-polarization level decreases as the feed substrate thickness decreases. As the impedance bandwidth of an ACMPA with a high permittivity feed substrate increases and its radiation characteristics improve as the feed substrate thickness decreases, the ACMPA configuration becomes suitable for integration with an MMIC.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.56-66
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• 2011

Multi-source evaporation is one of the methods to improve the thickness uniformity of thin films deposited by evaporation. In this study, a simulator for the relative thickness profile of a thin film deposited by a multi-source evaporation system was developed. Using this simulator, the relative thickness profiles of the evaporated thin films were simulated under various conditions, such as the number and arrangements of sources and source-to-substrate distance. The optimum conditions, in which the thickness uniformity is minimized, and the corresponding efficiency, were obtained. The substrate was a 5th generation substrate (dimensions of 1300 mm ${\times}$ 1100 mm). The number of sources and source-to-substrate distance were varied from 1 to 6 and 0 to the length of the major axis of the substrate (1300 mm), respectively. When the source plane, the area on which sources can be located, is limited to the substrate dimension, the minimum thickness uniformity, obtained when the number of sources is 6, was 3.3%; the corresponding efficiency was 16.6%. When the dimension of the source plane is enlarged two times, the thickness uniformity is remarkably improved while the efficiency is decreased. The minimum thickness uniformity, obtained when the number of sources is 6, was 0.5%; the corresponding efficiency was decreased to 9.1%. The expansion of the source plane brings about not only the improvement of the thickness uniformity, but also a decrement of the efficiency and an enlargement of equipment.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.3
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• pp.65-81
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• 1996

In this study forty-five X-bnd rectangular microstrip patch antennas fed by microstrip line using ${\lambda}$/4 transformer were fabricated on teflon substrates with low high permittivities and varous thickness (substrate thickness : 0.6 ~ 2.4 mm, permittivities : 2.15 ~ 10.0), and effects of permittivity and electrical thickness on antenna characteristics were studied with measured return loss (1/S$_{11}$) and resonant frequencies. When substrate electrical thickness was greater than 0.060 ${\lambda}_{0}$return loss was very good and genrally more than 20 dB, but resonance characteristics was somewhat unstable. The more than 0.088 ${\lambda}_{0}$ the thickness was, the more unstable it was. As a result, in the rest range except 12, 13 GHz we had very good mesured return loss iwth greater than 20 dB, and in the range 7 to 9 GHz resonant frequencies were within $\pm$2 % error, on ${\epsilon}_{r}$=5.0, height = 2.4 mm substrate.

• Korean Journal of Materials Research
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• v.25 no.9
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• pp.487-491
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• 2015

In photovoltaic power generation where minority carrier generation via light absorption is competing against minority carrier recombination, the substrate thickness and material quality are interdependent, and appropriate combination of the two variables is important in obtaining the maximum output power generation. Medici, a two-dimensional semiconductor device simulation tool, is used to investigate the interdependency in relation to the maximum power output in front-lit Si solar cells. Qualitatively, the results indicate that a high quality substrate must be thick and that a low quality substrate must be thin in order to achieve the maximum power generation in the respective materials. The dividing point is $70{\mu}m/5{\times}10^{-6}sec$. That is, for materials with a minority carrier recombination lifetime longer than $5{\times}10^{-6}sec$, the substrate must be thicker than $70{\mu}m$, while for materials with a lifetime shorter than $5{\times}10^{-6}sec$, the substrate must be thinner than $70{\mu}m$. In substrate fabrication, the thinner the wafer, the lower the cost of material, but the higher the cost of wafer fabrication. Thus, the optimum thickness/lifetime combinations are defined in this study along with the substrate cost considerations as part of the factors to be considered in material selection.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.450-453
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• 2012

In crystalline solar cells, the substrate itself constitutes a large portion of the fabrication cost as it is derived from semiconductor ingots grown in costly high temperature processes. Thinner wafer substrates allow some cost saving as more wafers can be sliced from a given ingot, although technological limitations in slicing or sawing of wafers off an ingot, as well as the physical strength of the sliced wafers, put a lower limit on the substrate thickness. Complementary to these economical and techno-physical points of view, a device operation point of view of the substrate thickness would be useful. With this in mind, BC-BJ Si and GaAs solar cells are compared one to one by means of the Medici device simulation, with a particular emphasis on the substrate thickness. Under ideal conditions of 0.6 ${\mu}m$ photons entering the 10 ${\mu}m$-wide BC-BJ solar cells at the normal incident angle (${\theta}=90^{\circ}$), GaAs is about 2.3 times more efficient than Si in terms of peak cell power output: 42.3 $mW{\cdot}cm^{-2}$ vs. 18.2 $mW{\cdot}cm^{-2}$. This strong performance of GaAs, though only under ideal conditions, gives a strong indication that this material could stand competitively against Si, despite its known high material and process costs. Within the limitation of the minority carrier recombination lifetime value of $5{\times}10^{-5}$ sec used in the device simulation, the solar cell power is known to be only weakly dependent on the substrate thickness, particularly under about 100 ${\mu}m$, for both Si and GaAs. Though the optimum substrate thickness is about 100 ${\mu}m$ or less, the reduction in the power output is less than 10% from the peak values even when the substrate thickness is increased to 190 ${\mu}m$. Thus, for crystalline Si and GaAs with a relatively long recombination lifetime, extra efforts to be spent on thinning the substrate should be weighed against the expected actual gain in the solar cell output power.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.393-396
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• 1999

A circuit model of silicon substrate coupling for CMOS RF-IC design is developed. Its characteristics are analyzed by using a simple RC mesh model in order to investigate substrate coupling. The coupling effects due to the substrate were characterized with substrate resistivity, oxide thickness, substrate thickness. and physical distance. Thereby the silicon substrate effects are analytically investigated and verified with simulation. The analysis and simulation of the model have excellent agreements with MEDICI(2D device simulator) simulation results.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.3
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• pp.57-62
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• 2012

In this paper, numerical analysis by finite element method, parameter design by the Taguchi method and ANOVA method were used to analyze about effect of design deviations and thickness variations on warpage of FCCSP substrate. Based on the computed results, it was known that core material in substrate was the most determining deviation for reducing warpage. Solder resist, prepreg and circuit layer were insignificant effect on warpage relatively. But these results meant not thickness effect was little importance but mechanical properties of core material were very effective. Warpage decreased as Solder resist and circuit layer thickness decreased but effect of prepreg thickness was conversely. Also, these results showed substrate warpage would be increased to maximum 40% as thickness deviation combination. It meant warpage was affected by thickness tolerance under manufacturing process even if it were met quality requirements. Threfore, it was strongly recommended that substrate thickness deviation should be optimized and controlled precisely to reduce warpage in manufacturing process.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.114-125
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• 2009

Effect of a finite square substrate plane on the radiation characteristics of a microstrip patch antenna is investigated. Effect of a finite square substrate plane on the resonance frequency and bandwidth is very small, while that on the radiation pattern is very large. The gain of front radiation and the direction of the maximum gain vary almost periodically with the length of a square substrate plane. The length of a square substrate plane for the maximum gam and the minimum gain of front radiation decrease as the electrical thickness of a substrate increases. The variation of the gain of front radiation with the length of a square substrate plane increases as the electrical thickness of a substrate increases. The variation of the radiation pattern with the length of a square substrate plane is almost determined by the electrical thickness of a substrate.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.301-313
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• 1996

The texture of vapor deposits(PVD and CVD) changes from the orientation that places the lowest energy lattice plane parallel to the substrate under the condition of low atom or ion concentration adjacent to the deposit, to the orientation that places the higher energy crystal planes parallel to the substrate as the atom or ion concentration adjacent to the deposit increases. However, in the early stage of deposition, the deposit-substrate interface energy and the surface energy constitute the most important energies of the system. Therefore, if the lattice match is established between the substrate and the deposit without generating much strain energy, the epitaxial growth takes place to reduce the interfacial energy. When the epitaxial growth does not take place, the surface energy is dominant in the early stage of deposition and the lowest energy crystal plane tends to be placed parallel to the substrate up to a critial thickness. The thickness depends on the deposition condition. If the deposition condition does not favor placing the lowest energy crystal plane parallel to the substrate, the initial texture will change to that compatible with the deposition condition as the film thickness increases, and the texture turnover thickness will be short. The microstructure and surface topography of deposits are related to their texture.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.477-480
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• 2004

We studied the characteristics of impedance and electromechanical coupling coefficient in ZnO and AIN thin films by using resonance frequency spectrum method. The response peak of impedance decreased with the decrease of thickness of piezoelectrics, the number of mode of response peak increased with the increase of substrate thickness. An error of $k_{t}^{2}$ estimated from input $k_{t}^{2}$ increased as the thickness of piezoelectrics decreased and the thickness of substrate increased. Also, the error was increased in case of a large acoustic impedance of substrate. It was found that the composite resonator operating in optimized condition could be designed through the resonance frequency spectrum analysis of composited resonator consisted of piezoelectric thin film and substrate.