Solid State Phenomena Vol. 343

Abstract: Wire bonding is the preferred interconnection in the IC packaging. Understanding the electrical performance of bonding wire as transmission line is utmost important. To date, there is very limited studies on the transmission performance of fine pitch bare bonding wire especially the insulated wires. This paper investigated the transmission performance of single bare bonding wires and insulated bonding wires with different wire material, wire diameter, bonding height, insulation thickness at high frequency. The simulation analysis shows that when the frequency increases above 15Ghz, the effect of the geometric parameters has no significant different to the transmission performance. The thickness of the insulation between 0.1μm to 0.3μm reacted similar performance for return loss and insertion loss across all frequency

Abstract: Fan-out wafer-level package is a very promising packaging technology with good thermal and electrical performance. The fan-out wafer-level package exhibits beneficial features such as low profile, high I/O density, low cost, and efficient computing. The package experiences large temperature variations in the assembly phase which causes internal stresses. In particular, the mismatch between the coefficient of thermal expansion of the epoxy molding compound and the substrate due to the cool down phase of the cure process causes the internal stresses in the package. These internally induced stresses result to interfacial delamination. In this study, the interfacial delamination on a fan-out wafer-level package right after post mold cure of glass wafer was evaluated using the stress-based damage index through the finite element analysis in the ANSYS software package. The model was validated by comparing the simulation result of the glass wafer warpage to the existing experimental result from literature. From the warpage simulation of the glass wafer, the region on the package with high stress level was located and examined which may cause interfacial delamination. The maximum shear stress and principal stress at the epoxy molding compound and the Silicon chip interface was found to exceed the adhesion strength. This indicates that the interfacial delamination is inevitable. The information obtained from the stress analysis of molded wafer provides insight for the possible interfacial failure of fan-out wafer-level package in the individual package when subjected to thermomechanical loads.

Abstract: Conductive and flexible electronics have attracted great demands and attention in the field of stretchable and wearable electronic devices. In this work, polydimethylsiloxane (PDMS) was composited with different drops of graphene solution to produce flexible, conductive and optically transparent PDMS/Graphene composite using the drop-cast method. The dielectric constants of PDMS and PDMS/Graphene composite were measured using Agilent dielectric probe. I-V characterization was used to measure the conductivity of the flexible substrate in flat and bending conditions. The UV-VIS was used to measure the transmittance properties of the substrate. Comparing the electrical properties of the pristine PDMS substrate with graphene composited PDMS substrates, the current shows a slight decrease due to the physical morphology of PDMS/Graphene composite that creates a small hole on the surface. No significant changes can be found between 1 drop, 2 drops, 3 drops and 4 drops of graphene in PDMS solution. For the dielectric measurement, the result of composited PDMS/Graphene sample had shown a lower value of dielectric constant (1.1 F/m) compared to pure PDMS (2.33 F/m). This shows that the existence of graphene in PDMS reduces the dielectric constant of pristine PDMS. The result of UV-VIS shows the samples with 4 drops of graphene having the lowest visible transmittance. The PDMS/Graphene composite can be concluded as a dielectric material with a lower dielectric constant. It has the potential to be used as a conductive substrate for further flexible interconnect materials since it has a unique electrical feature and robust mechanical strength.

Abstract: Metal oxide semiconductor (MOS) capacitor is a trilayer device that comprises of metal, dielectric, and semiconductor layer. The advancement of MOS technology has greatly give huge improvement to MOS devices which lead to scaling down the MOS devices. The reduction of dielectric thickness of conventional dielectric material has coming to an end, therefore as alternative new material with high mobility carrier is suggested to overcome the problem. The objectives of this work are to study the performance of MOS capacitor. Two parameters were varied, first the semiconductor material which is silicon (Si), germanium (Ge) and silicon germanium (SiGe) and second is the dielectric material that is silicon dioxide (SiO₂) and silicon nitride (Si₃N₄). The performance of the MOS capacitor is evaluated based on the capacitance-voltage (C-V) and current-voltage (I-V) characteristics. Silvaco TCAD tool were use as as simulation tool for the method of investigation. Result shown that the performance of the MOS capacitor increased when Ge and SiGe were used as semiconductor material and Si₃N₄ as dielectric layer. It can see that with V_T of 4.15 V for MOS with Ge and 4.28 V for MOS with SiGe. For the C-V properties C_max value for both devices are F and F, respectively. The results show that there is around 100% increment in capacitance value when Ge is used as semiconductor layer but there is no increment or decrement in capacitance value when SiGe is used. Based on the obtained results, Ge is chosen as the best semiconductor material.

Abstract: This paper investigates performance of ZnO/SnO₂ nanorods structure thin film deposited at two different ZnO seed layer (ZnO seed A and ZnO seed B) for humidity sensor application. ZnO seed A and ZnO seed B were deposited using two different method which were sputtering method and spin coating method respectively. ZnO/SnO₂ nanorods structure thin film that has been prepared on ZnO seed A and ZnO seed B using thermal chemical vapor deposition (CVD). The structural properties have been characterized using field emission scanning electron microscopy (FESEM) (JEOL JSM 6701F). Base on the FESEM image the size of ZnO seed A and ZnO seed B were ranging around 75 to 85 nm and 17 to 21 nm respectively. The results analyzed were for ZnO/SnO₂ composite nanorods structure size on ZnO seed A and ZnO seed B were averagely around 18 nm to 29 nm. The sensor properties were characterized by using current-voltage (I-V) measurement (Keithley 2400). ZnO/SnO₂ nanorods structure thin film deposited on ZnO Seed A performed highest sensitivity with 265 ratio compare to ZnO/SnO₂ nanorods structure thin film deposited on ZnO Seed B with 75 ratio of sensitivity.

Abstract: A series of GaAsBi/GaAs multiple quantum well p-i-n diodes was grown using molecular beam epitaxy and the opto-electrical characterisations are presented. The result shows that devices experience low carrier extractions when light is absorbed due to hole trapping in the valence band. Carrier enhancement can be achieved by applying slight reverse bias when the measurement was taken. The absorption coefficient of the devices is confirmed to be similar with other Bi-based work. GaAsBi/GaAs multiple quantum well do have a lot of room for improvement especially on growth, structure and strain level of the material. If these components can be catered, GaAsBi can be a competitive alternative for 1 eV junction in multiple junction solar cells.

Abstract: This paper investigates a breath sensor device that is designed to detect the moisture in human bulk matrix in outdoor conditions. The human bulk matrix is rich in moisture and carbon dioxide apart from the 872 volatile organic compounds emanating from the human breath. Human breathing effort is a respiration process that involves inhalation and exhalation modes. The human bulk matrix is a product of the latter. Most research in human breath analysis is concentrating on both human bulk matrix and breathing pattern. The aim of this study is to characterize the fabricated breath sensor at different input wave frequencies in the outdoor environment. In this study, an outdoor experiment was carried out using the breath sensor device that is connected to the input waveform from the frequency generator and the output reading is captured using the oscilloscope. A single exhaled breath originated from the human subject is required to activate the breath sensor. This method is easier and simpler, and the output wave result is generated by an oscilloscope in real-time. The result indicates that the investigated breath sensor is suitable for clinical and healthcare monitoring. Early studies indicate that the breath sensor can diagnose diseases related to breathing problems such as sleep apnoea, asthma, and strokes.