Association of Super-Advanced Electronics

Security at virtualization level has always been a major issue in cloud computing environment. A large number of virtual machines that are hosted on a single server by various customers/client may face serious security threats due to internal/external network attacks. In this work, we have examined and evaluated these threats and their impact on OpenStack private cloud. We have also discussed the most popular DOS (Denial-of-Service) attack on DHCP server on this private cloud platform and evaluated the vulnerabilities in an OpenStack networking component, Neutron, due to which this attack can be performed through rogue DHCP server. Finally, a solution, a game-theory based cloud architecture, that helps to detect and prevent DOS attacks in OpenStack has been proposed.

We demonstrate the feasibility of fabricating all‐printed organic TFT circuits by high precision alignment technology on flexible plastic substrates. The ring oscillator and 8‐bit asynchronous down counter of organic‐TFTs by all printing technology are investigated. We also present the performance of the light‐weight pressure sheet sensor with integrated gate driver of organic‐TFTs.

Recently, the downsizing and high-performing semiconductor packages have been developed and 3D packaging has been spurred research into reliability of TSV (through silicon via) [l]-[9]. In conventional SiP (System in Package), several semiconductor chips had been arranged in a plate. It is difficult to correspond to downsizing and high-performing of electronic devices because that large area is occupied by the package. The semiconductor chips have been stacked and TSVs have been used to communicate between the chips in order to solve above problems. The 3D stacked structure which was developed by ASET (Association of Su per-Advanced Electronics Technologies) [10] is shown in Fig.1. TSV (copper) is electrode which passes through silicon chip and micro bump (copper) [11] is arranged between chips. Heat is generated in package due to operation of semiconductor device, and it has been reported that silicon is broken by thermal stress which is depend on temperature increment. In case of 3D-SIP, higher stress has to be considered in the most outer part of TSV and micro bump structure due to warp and mismatch of CTE (coefficient of thermal expansion) of material. Therefore simulations with detail model must be desired for more accurate evaluation of stresses in Si chips and TSVs. However it is difficult that all of TSVs and micro bumps in chips were modeled due to large number of numerical data even if the latest computing systems have been adopted.

We evaluated low-impedance power distribution network (PDN) of decoupling capacitor embedded interposers for 3-D integrated LSI system. Measurements are carried out using the developed impedance analyzer system of a wide frequency range for evaluating ultralow impedance, and calculations are carried out using 2.5-D and 3-D finite element method (FEM) electromagnetic field simulator. We fabricated various types of capacitor mounted or capacitor embedded interposers test element group (TEG), such as surface-mounted and embedded chip capacitors, and thin film capacitors on silicon interposers using the same simple design to compare measurement results with calculation ones. As a result, the ultralow impedance evaluation system that has a high measurement dynamic range at the entire measurable frequency band can be realized. Furthermore, by using 2.5-D and 3-D FEM electromagnetic field simulator, it is expected that the accurate and wideband comparative verification of the PDN impedance analysis and evaluation can be realized.

The relation between maximum temperature in Si chip and varied heat transfer coefficients of heat sink is shown in Fig. 5. Maximum temperature for device operation was assumed to be 85 °C. Heat transfer coefficient of heat sink at device operation is estimated to be 4.5W/m2K by quadratic approximation of least square method. Maximum temperature of 3D SiP was almost 85 °C and uniform temperature distribution.

Thermal conduction and mechanical stresses in through silicon via (TSV) structures in three dimensional system in package (3D SiP) under device operation condition were discussed. A large scale simulator, ADVENTURECluster® based on finite element method (FEM) was used to simulate the effects of voids formed inside Cu TSVs on the thermal conduction and mechanical stresses in the TSV structure. The thermal performance that was required in 3D SiP was estimated to ensure the reliability. Simulations for thermal stresses in the TSV structure in 3D SiP were carried out under thermal condition due to power ON/OFF of device. In case that void was not present inside the TSV, the stresses in TSV were close to the hydrostatic pressure and the magnitude of the equivalent stress was lower than the yield stress of copper. Maximum principal stress of the Si chip in the TSV structure for the case without voids was lower than that of the bending strength of silicon. However, the level of the stresses in the Si chips should not be negligible for damages to Si chips. In case that void was present inside the TSV, stress concentration was occurred around the void in the TSV. The magnitude of the equivalent stress in the TSV was lower than the yield stress of copper. The magnitude of the maximum principal stress of the Si chip was lower than that of the bending strength of silicon. However, its level should not be negligible for damages to TSVs and Si chips. The stress on inner surfaces of Si chip was slightly reduced due to the presence of a void in the TSV.

For the thermal management of three-dimensional (3D) chip stack, its thermal resistance needs to be clearly understood. In this study, 3D stacked test chips are fabricated, which are implemented with PN junction diodes for temperature sensors and diffused resistors for heating. At SemiTherm2011, the equivalent thermal conductivity of the interconnection, including BEOL (Back-End-Of-the-Line, wiring layer) is experimentally obtained to be 1.6W/mC and this time, we measure the thermal effect of Cu TSVs and it is experimentally supported that as the Cu TSV area ratio increases, the thermal conductivity of chip with TSVs in the vertical direction increases, on the contrary, that in the horizontal direction decreases. Also, the transient thermal measurement is performed and its result is compared with steady state measurement result. Further, the thermal capacitance measurement of 3D stacked test chip with hot spot heating is performed, which is essential to determine the transient thermal performance of 3D chip stack.

Low stress package design is one of the greatest challenges for the realization of reliable 3D integrated devices, since they are composed of elements susceptible to failures under high stress such as thin dies, metal through silicon vias (TSVs), and fine pitch interconnections. In variety of package components, an organic interposer is a key to obtain low cost modules with high density I/Os. However, the large mismatch in coefficient of thermal expansion (CTE) between silicon dies and organic laminates causes high stress in an organic package. The major parametric components in 3D devices are dies with /without Cu-TSVs, laminates, bumps, and underfill layers. Especially, the die thicknesses and underfill properties are ones of the parameters that give us some range to control as package design parameters. In general, the underfill material with a high modulus and a low CTE is effective in reducing the stress in solder interconnections between the Si die and the laminate. However, the filler content of underfill materials with such mechanical properties generally results in high viscosity. The use of high viscous materials in between silicon dies in 3D modules can degrade process ability in 3D integration. In this study, we show that the interchip underfills in 3D modules have a wider mechanical property window than in 2D modules even with fine pitch interconnections consisting mostly of intermetallic compounds (IMCs). Also the finite element analysis results show that the optimization of the structural or thermomechanical properties of organic laminates and interchip underfill contributes to reduction of stressing thinned silicon dies which may have some risks to the device performance.

Power supply impedance of power distribution network (PDN) for a 3D system-in-package (SiP) has been investigated. The 3D SiP consisted of 3 stacked chips and an organic package substrate. These three chips were a memory chip on the top, Si interposer in the middle, and a logic chip on the bottom. The size of each chip was the same, and 9.93 mm by 9.93 mm. A large number of through silicon vias (TSV's) were formed to the silicon interposer and the logic chip. Next, the 3 stacked chips were assembled on the organic package substrate, whose size was 26 mm by 26 mm. The PDN impedance for each chip was extracted by using XcitePI (Sigrity Inc.). Then, the PDN impedance for the organic package substrate was extracted by using SIwave (Ansys Inc.). Finally, the total PDN impedance was synthesized. In this paper, the PDN impedances of the memory chip, Si interposer, and the logic chip were calculated respectively, and then the total PDN impedance was synthesized to estimate the power supply disturbance due to the anti-resonance peak.

TSV (Through Silicon Via) is one of the key elements for building 3D integrated silicon devices with high bandwidth interconnections. In this paper, we propose a diagnostic method for TSV defects by using X-ray projection microscopy. By optimizing the image contrast of the X-ray projection micrographs in reference to its X-ray intensity histogram, we could obtain the small defect features in TSVs fast and non-destructively. Comparison between this X-ray observation and the destructive cross sectional observation agreed very well. We also extended the implementation of this X-ray microscope diagnostic method to 8-in. full wafer observation. We investigated the wafers with copper-filled TSVs with 80 µm and 20 µm diameters, and confirmed the feasibility of this method for an in-line process monitoring.