Browsing by Author "Hsieh, JC"

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40-GHz coplanar waveguide bandpass filters on silicon substrate
(2002-11-01)
Chan, KT
;
Chen, CY
;
Chin, A
;
Hsieh, JC
;
Liu, J
We report a very simple process to fabricate high performance filter on Si at 40 GHz; using proton implantation. The filter has only -3.4-dB loss at peak transmission of 40 GHz; with a broad 9-GHz bandwidth. In sharp contrast, the filter on 1.5-mum SiO2 isolated Si has much worse transmission and reflection loss. This is the first demonstration of high performance filter at millimeter-wave regime on Si with process compatible to current VLSI technology.
Characteristics of vortex flow in a low speed air jet impinging onto a heated disk in a vertical cylindrical chamber
(2003-11-01)
Hsieh, JC
;
Cheng, TC
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
An experiment combining flow visualization and transient temperature measurement is carried out to investigate the characteristics of the mixed convective vortex flow resulting from a low speed air jet impinging onto a heated horizontal circular disk confined in a vertical adiabatic cylindrical chamber. Attention is focused on the conditions leading to the onset of the inertia and buoyancy driven vortex rolls and the effects of governing nondimensional groups on the steady and time dependent vortex flow. More specifically, experiments are conducted for the jet Reynolds number varied from 0 to 1082 and Rayleigh number from 0 to 18,790 for two different injection pipes. The results show that typically the steady vortex flow in the processing chamber consists of two inertia-driven and one buoyancy-driven circular vortex rolls. The secondary inertia-driven roll only appears at high jet Reynolds numbers. At low buoyancy-to-inertia ratio Gr/Re-j(2) the vortex rolls are steady and axisymmetric. But at certain high Gr/Re-j(2) the vortex flow becomes unstable and the vortex rolls are somewhat deformed. Besides, new vortex rolls can be induced by the additional thermal rising from the heated disk and the splitting of the primary inertia-driven roll. The temporal characteristics of the time periodic vortex flows are examined in detail. In the region dominated by the new rolls the flow oscillates significantly. Finally, empirical equations are proposed to correlate the oscillation frequency of the time periodic flow, and the size and location of the vortex rolls. Furthermore, the conditions for the onset of the buoyancy driven rolls are given. A flow regime map is provided to delineate the temporal state of the vortex flow. (C) 2003 Elsevier Ltd. All rights reserved.
Effects of jet-to-disk separation distance on the characteristics of mixed convective vortex flow in an impinging air jet confined in a cylindrical chamber
(2005-01-01)
Hsieh, JC
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
How the jet-to-disk separation distance H affects various aspects of the laminar mixed convective vortex flow resulting from a low speed air jet impinging onto a heated horizontal disk confined in a vertical adiabatic cylindrical chamber is explored herein by flow visualization combined with temperature measurement. In the present study the air flow rate is varied from 1.0 to 8.0 slpm (standard liter per minute) for two different injection pipes with the temperature difference between the heated disk and air injected into the chamber varied from 0 to 25.0degreesC at four jet-to-disk separation distances. The corresponding jet Reynolds and Rayleigh numbers, respectively, range from 0 to 1082 and from 0 to 63,420. The experimental results clearly reveal a new vortex roll. More specifically, in the upper range of the jet Reynolds number tested here a small tertiary inertia-driven circular vortex roll appears near the upper wall of the chamber. in addition to the previously known primary and secondary inertia-driven rolls. Besides. we also note that a reduction in the jet-to-disk separation distance causes a delayed onset of the inertia-driven rolls except for H greater than or equal to 20.0 mm and in the meantime causes a substantial decrease in the Rayleigh number since Ra alpha H-3, which in turn significantly reduces the size and strength of the buoyancy-driven roll. Moreover, the inertia-driven rolls are bigger for a larger H. At the largest H (=30.0 mm) tested here both the primary inertia-driven roll and buoyancy-driven roll are relatively large and they can contact with each other. Hence no space is available for the secondary inertia-driven roll to appear. Our data also suggest that the onset of the buoyancy roll takes place when the local buoyancy-to-inertia ratio at the edge of the disk Gr/Re-we(2) approximate to 33.0 within the experimental uncertainty. Finally, the temperature data indicate that the steady radial air temperature distributions are non-monotonic which mainly reflects the counter-rotating vortex flow structure of the primary inertia-driven and buoyancy-driven rolls. (C) 2004 Elsevier.Ltd. All rights reserved.
Frequency-dependent capacitance reduction in high-k AlTiOx and Al2O3 gate dielectrics from IF to RF frequency range
(2002-04-01)
Chen, SB
;
Lai, CH
;
Chan, KT
;
Chin, A
;
Hsieh, JC
We have characterized the capacitance and loss tangent for high-k Al2O3 and AlTiOx gate dielectrics from IF (100 KHz) to RF (20 GHz) frequency range. Nearly the same rate of capacitance reduction as SiO2 was demonstrated individually by the proposed Al2O3 and AlTiOx gate dielectrics as frequency was increased. Moreover, both dielectrics preserve the higher k better than SiO2 from 100 KHz to 20 GHz. These results suggest that both Al2O3 and AlTiOx are suitable for next generation MOSFET application into RF frequency regime.
High-density MIM capacitors using Al2O3 and AlTiOx dielectrics
(2002-04-01)
Chen, SB
;
Lai, CH
;
Chin, A
;
Hsieh, JC
;
Liu, J
We have investigated the electrical characteristics of Al2O3 and AlTiOx MIM capacitors from IF (100 KHz) to RF (20 GHz) frequency range. Record high capacitance density of 0.5 and 1.0 muF/cm(2) are obtained for Al2O3 and AlTiOx MIM capacitors, respectively, and the fabrication process is compatible to existing VLSI backend integration. However, the AlTiOx MIM capacitor has very large capacitance reduction as increasing frequencies. In contrast, good device integrity has been obtained for Al2O3 MIM capacitor as evidenced from the small frequency dependence, low leakage current, good reliability, small temperature coefficient, and low loss tangent.
ICA-based spatiotemporal approach for single-trial analysis of postmovement MEG beta synchronization
(2003-12-01)
Lee, PL
;
Wu, YT
;
Chen, LF
;
Chen, YS
;
Cheng, CM
The extraction of event-related oscillatory neuromagnetic activities from single-trial measurement is challenging due to the non-phase-locked nature and variability from trial to trial. The present study presents a method based on independent component analysis (ICA) and the use of a template-based correlation approach to extract Rolandic beta rhythm from magnetoencephalographic (MEG) measurements of right finger lifting. A single trial recording was decomposed into a set of coupled temporal independent components and corresponding spatial maps using ICA and the reactive beta frequency band for each trial identified using a two-spectrum comparison between the postmovement interval and a reference period. Task-related components survived dual criteria of high correlation with both the temporal and the spatial templates with an acceptance rate of about 80%. Phase and amplitude information for noise-free MEG beta activities were preserved not only for optimal calculation of beta rebound (event-related synchronization) but also for profound penetration into subtle dynamics across trials. Given the high signal-to-noise ratio (SNR) of this method, various methods of source estimation were used on reconstructed single-trial data and the source loci coherently anchored in the vicinity of the primary motor area. This method promises the possibility of a window into the intricate brain dynamics of motor control mechanisms and the cortical pathophysiology of movement disorder on a trial-by-trial basis. (C) 2003 Elsevier Inc. All rights reserved.
RF MIM capacitors using high-K Al2O3 and AlTiOx dielectrics
(2002)
Chen, SB
;
Lai, CH
;
Chin, A
;
Hsieh, JC
;
Liu, J
Record high capacitance density of 0.5 and 1.0 muF/cm(2) are obtained for Al2O3 and AlTiOx MIM capacitors respectively, with loss tangent < 0.01 and process compatible to existing VLSI back-end integration. However, the AlTiOx MINI capacitor has large capacitance reduction as increasing frequencies. In contrast, the Al2O3 MINI capacitor has good device integrity of low leakage current of 4.3x10(-8) A/cm(2), small frequency-dependent capacitance reduction, and good reliability.
RF noise in 0.18-mu m and 0.13-mu m MOSFETs
(2002-12-01)
Huang, CH
;
Lai, CH
;
Hsieh, JC
;
Liu, J
;
Chin, A
We have studied the gate finger number and gate ength dependence on minimum noise figure (NFmin) in deep submicrometer MOSFETs. A lowest NFmin. of 0.93 dB is measured in 0.18-mum MOSFET at 5.8 GHz as increasing finger number to 50 fingers, but increases abnormally when above 50. The scaling gate length to 0.13 mum shows larger NFmin than the 0.18-mum case at the same finger number. From the analysis of a well-calibrated device model, the abnormal finger number dependence is due to the combined effect of reducing gate resistance and increasing substrate loss as increasing finger number. The scaling to 0.13-mum MOSFET gives higher NFmin due to the higher gate resistance and a modified T-gate structure proposed to optimize the NFmin for further scaling down of the MOSFET.
Suppression of buoyancy-driven vortex flow resulting from a low speed jet impinging onto a heated disk in a vertical cylinder by cylinder top tilting
(2004-07-01)
Hsieh, JC
;
Cheng, CW
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
Buoyancy-driven vortex flow resulting from a low speed round gas jet impinging vertically downwards onto a heated horizontal circular disk confined in an adiabatic vertical cylindrical chamber can be strong and even unstable as the buoyancy-to-inertia ratio exceeds certain critical level. An experiment combining flow visualization and temperature measurement is conducted in the present study to explore the suppression of the above buoyancy-driven vortex gas flow by inclining the top of the cylindrical chamber. The chamber top is chosen to incline linearly in the radial direction so that the mean flow in the wall-jet region is accelerated and meanwhile the effective buoyancy signified by the local Rayleigh number reduces in that direction. Specifically, in the present experiment. the disk-to-chamber top separation distance decreases from 20.0 mm at the jet axis to 10.0 mm at the chamber side. Tests are conducted for the jet flow rate varied from 1.0 to 5.0 slpm (standard liter per minute) and the jet-to-disk temperature difference varied from 0 to 35.0 degreesC for two injection pipes with diameter 10.0 and 22.1 mm for the chambers with horizontal and inclined tops. The results from the flow visualization indicate that the chamber top inclination can effectively suppress the unstable buoyancy-induced vortex roll and the temporal flow oscillation at high buoyancy-to-inertia ratios. However, the effects of the chamber top inclination on the inertia-driven rolls are much milder. The non-monotonic air temperature distribution in the radial direction is found to result from the unique vortex flow structure in the chamber. A universal criterion based on the local flow and thermal conditions in the wall-jet region for the onset of the buoyancy-driven roll is proposed. To quantify the characteristics of the vortex flow in the chamber with the inclined top, empirical correlations have been proposed for the size and location of the vortex rolls. (C) 2004 Elsevier Ltd. All rights reserved.