Design considerations for the mechanical integrity of airgaps in nano-interconnects under chip–package interaction; a numerical investigation

Airgaps can undermine the mechanical properties of nano-interconnects and lead to reliability issues such as back end of line (BEOL) fractures. In this context, interconnect delamination under chip–package interaction (CPI) induced loads is a major failure mode which benefits from in-depth investigation. In this computational study, models of airgaps fabricated using the etch-back approach are developed for 90 nm pitch interconnects and potential mechanical failure modes including the fracture energy release rate (ERR) at various material interfaces are investigated. In addition, capacitance benefits of airgap implementation compared to the mainstream low-k technology are calculated using a capacitance simulator. Subsequently, mechanically conscious airgap design strategies are proposed which allow taking advantage of the maximal capacitive benefits of airgaps and limit the CPI related reliability concerns.     

A model and framework for human–environment interaction

This paper describes our approach for studying and prototyping human–environment interaction (HEI) within a pervasive space applied to ambient assistive living context. The objective of our approach consists in developing and implementing an HEI framework to modelling the human–machine interaction. This framework allows a customization facility for designers, developers and even end-users in defining and processing multimodal interaction. We underline the fact that the design of interaction for users with special needs do not have to be considered as orthogonal to the application but rather as a validation context which is the heart of our research laboratory activities. We have integrated our framework in demonstrator dedicated to people with disabilities to validate the concept. This paper will present the framework, the developed components of our HEI model and the prototype realised. The outcome of this research activity is to provide a multimodal processing framework to favour natural human pervasive environment by decreasing the cognitive workload necessary in a complex environment. Thus, this will contribute to achieve ubiquitous accessible space.     

The dipole–dipole interaction in photonic quantum wires

Numerical simulations are performed on the absorption coefficient in photonic quantum wires in the presence of the dipole–dipole interaction (DDI). The quantum wire is made from the two photonic crystals A and B where A is embedded in B. The probe and pump laser fields are applied to study the absorption process. Nanoparticles are not only interacting with each other via the DDI but also interacting with bound photon states of the wire. It is found that in the absence of the DDI the spectrum has two peaks and two minima. However, in the presence of the DDI the two peaks shift to the left of the zero detuning but the position of the minima does not change. These properties can be used to make new types of optoelectronic devices.     

Fluid–solid coupling thermo-mechanical analysis of high power LED package during thermal shock testing

The virtual design by numerical simulation to model various accelerated reliability testing conditions is adopted to validate and improve the reliability of the high power LED package. In this study, the reliability of the high power LED package during thermal shock testing is investigated by fluid–solid coupling thermo-mechanical modeling by considering nonlinear time and temperature dependent material properties. Through fluid–solid coupling transient thermal transfer analysis, it is found that the maximum thermal gradient exceeds 75 K during the rapid cooling process and 91 K during the rapid heating process of the thermal shock testing which is ignored in the traditional isothermal assumption. The calculation results indicate that the equivalent plastic strain range of the bonding wire within the LED package with consideration of the temperature gradient is much higher than that with the isothermal assumption. The assumption of the isothermal condition is not appropriate which will lead to overestimation of the predicted lifetime. The viscoelastic behaviors of the silicone have significant influences on the lifetime prediction of the bonding wire and silicone with low elastic modulus and coefficient of thermal expansion (CTE) can significantly enhance the reliability of the bonding wire under the thermal shock loading. The results in this study could provide a guideline on design for reliability in the high power LED packaging.     

On Recombination Processes in CdS–PbS Films

The transverse and longitudinal photoconductivity, photoluminescence, and cathodoluminescence of sublimated (CdS)_0.9–(PbS)_0.1 films at room temperature and upon cooling are studied. The role of inclusions of the narrow-gap phase in the processes is shown. The films are excited over the entire active surface and pointwise (within one crystallite). The surface recombination rate and the lifetime of majority charge carriers at different generation rates and characters of excitation are estimated. A comparative table of recombination parameters of CdS and CdS–PbS films is presented.     

On the Kalman–Yakubovich–Popov lemma and the multidimensional models

This paper focuses on Kalman–Yakubovich–Popov lemma for multidimensional systems described by Roesser model that possibly includes both continuous and discrete dynamics. It is shown that, similarly to the standard 1-D case, this lemma can be studied through the lens of S-procedure. Furthermore, by virtue of this lemma, we will examine robust stability, bounded and positive realness of multidimensional systems.     

Modelling of spatio–temporal interaction for video quality assessment

Video services have appeared in the recent years due to advances in video coding and convergence to IP networks. As these emerging services mature, the ability to deliver adequate quality to end-users becomes increasingly important. However, the transmission of digital video over error-prone and bandwidth-limited networks may produce spatial and temporal visual distortions in the decoded video. Both types of impairments affect the perceived video quality. In this paper, we examine the impact of spatio–temporal artefacts in video and especially how both types of errors interact to affect the overall perceived video quality. We show that the impact of the spatial quality on overall video quality is dependent on the temporal quality and vice-versa. We observe that the introduction of a degradation in one modality affects the quality perception in the other modality, and this change is larger for high-quality conditions than for low-quality conditions. The contribution of the spatial quality to the overall quality is found to be greater than the contribution of the temporal quality. Our results also indicate that low-motion talking-head content can be more negatively affected by temporal frame freezing artefacts than other general type of content with higher motion. Based on the results of a subjective experiment, we propose an objective model to predict overall video quality by integrating the contributions of a spatial quality and a temporal quality. The non-linear model shows a very high linear correlation with subjective data.     

DEC chip 21230底层软件的研究

基于对ＤＥＣ－２１２３０压缩芯片的设计思想和ＭＰＥＧ－１工作流程的理解,分析了２１２３０软件的体系结构,并对其中的关键部分进行了仔细研究,使得以其为核心的ＭＰＥＧ－２实时压缩得以实现。     

Human–robot interaction based on gesture and movement recognition

Human–robot interaction (HRI) has become a research hotspot in computer vision and robotics due to its wide application in human–computer interaction (HCI) domain. Based on the explored algorithms of gesture recognition and limb movement recognition in somatosensory interaction, an HRI model of a robotic arm is proposed for robot arm manipulation. More specifically, 3D SSD architecture is used for the location and identification of gesture and arm movement. Then, DTW template matching algorithm is adopted to trace the dynamic gestures. The interactive scenarios and interactive modes are designed for experiment and implementation. Virtual interactive experimental results have demonstrated the usefulness of our method.     

A hand gesture recognition technique for human–computer interaction

We propose an approach to recognize trajectory-based dynamic hand gestures in real time for human–computer interaction (HCI). We also introduce a fast learning mechanism that does not require extensive training data to teach gestures to the system. We use a six-degrees-of-freedom position tracker to collect trajectory data and represent gestures as an ordered sequence of directional movements in 2D. In the learning phase, sample gesture data is filtered and processed to create gesture recognizers, which are basically finite-state machine sequence recognizers. We achieve online gesture recognition by these recognizers without needing to specify gesture start and end positions. The results of the conducted user study show that the proposed method is very promising in terms of gesture detection and recognition performance (73% accuracy) in a stream of motion. Additionally, the assessment of the user attitude survey denotes that the gestural interface is very useful and satisfactory. One of the novel parts of the proposed approach is that it gives users the freedom to create gesture commands according to their preferences for selected tasks. Thus, the presented gesture recognition approach makes the HCI process more intuitive and user specific.     

Brain–computer interface: The next frontier of telemedicine in human–computer interaction

The study proposes a novel brain–computer interface scheme for the next frontier of telemedicine in human–computer interaction, where the goal is to improve the interactions between users and computers in telemedicine. The system consists of discriminative area selection, feature extraction and classification. Discriminative area selection is proposed to obtain the optimal discriminative area, which can decrease the time length of event-related area to achieve more efficient computation and higher accuracy. A fuzzy Hopfield neural network is used to classify the features extracted by means of wavelet-fractal approach. Experimental results show that the proposed system is robust and performs better than several previous methods. It is also suggested being suitable for the applications of telemedicine in human–computer interaction.     

基于0.5chip级LMMSE均衡算法研究

LMMSE接收机通过基于最小均方误差(MMSE)准则的均衡滤波,能够有效的抑制多径带来的符号间干扰,恢复扩频码字间的正交性。文章在UTRA HSPA+系统下行链路平台上,研究了LMMSE均衡器0.5chip级算法,并仿真证明,0.5chip级比1chip级算法具有更好的性能。     

A 0.7 V 6.66–9.36 GHz wide tuning range CMOS LC VCO with small chip size

The circuit designs are based on TSMC 0.18 μm CMOS standard technology model. The designed circuit uses transformer coupling technology in order to decrease chip area and increase the Q value. The switched-capacitor topology array enables the voltage-controlled oscillator (VCO) to be tuned between 6.66 and 9.36 GHz with 4.9 mW power consumption at supply voltage of 0.7 V, and the tuning range of the circuit can reach 33.7%. The measured phase noise is ?110.5 dBc/Hz at 1 MHz offset from the carrier frequency of 7.113 GHz. The output power level is about ?1.22 dBm. The figure-of-merit and figure-of-merit-with-tuning range of the VCO are about ?180.7 and ?191.25 dBc/Hz, respectively. The chip area is 0.429 mm² excluding the pads. The presented ultra-wideband VCO leads to a better performance in terms of power consumption, tuning range, chip size and output power level for low supply voltage.     

On the Poole–Frenkel Effect in Polycrystalline Europium Sulfide

Semiconductors - The field and temperature dependences of the electrical conductivity of europium sulfide are studied in the temperature range 160–430 K. It is found that the electrical...     

Do chip size limits exist for DCA?

Solder joints, the most widely used flip chip on board (FCOB) interconnects, have a relatively low structural compliance due to the large thermal expansion mismatch between silicon die and the organic substrate. The coefficient of thermal expansion (CTE) of the printed wiring board (PWB) is almost an order of magnitude greater than that of the integrated circuit (IC). Under operating and testing conditions, this mismatch subjects the solder joints to large creep strains and leads to early failure of the solder connections. The reliability of such flip chip structures can be enhanced by applying an epoxy-based underfill between the chip and the substrate, encapsulating the solder joints. This material, once cured, mechanically couples the IC and substrate together to locally constrain the CTE mismatch. However, the effects of CTE mismatch are assumed to become more severe with increasing chip size. Even with the addition of an underfill material, it has been supposed that there are limits on the chip size used in flip chip applications     

Structure of BaTiO3 thin films modified by film–substrate interaction

Substrate-free crystallization of BaTiO₃ thin films was investigated. It was found that the substrate-free crystallized BaTiO₃ films attain a hexagonal structure, whereas the substrate-supported films always crystallize in the tetragonal phase. The substrate-free crystallized hexagonal BaTiO₃ demonstrates detectable pyroelectric effect and does not exhibit phase transitions in the 25–423 K temperature range. Therefore, the substrate-free crystallized BaTiO₃ represents a previously unreported phase of BaTiO₃.     

On the Mechanism of the Vapor–Solid–Solid Growth of Au-Catalyzed GaAs Nanowires

Semiconductors - The mechanism of the vapor–solid–solid growth of Au-catalyzed GaAs nanowires in the temperature range of 420–450°C is investigated. For the first time, the...     

Mechanical reliability of Sn-rich Au–Sn/Ni flip chip solder joints fabricated by sequential electroplating method

In this study, we evaluated the mechanical reliability of Sn-rich, Au–Sn/Ni flip chip solder bumps by using a sequential electroplating method with Sn and Au. After reflowing, the average diameter of the solder bump was approximately 80 μm and only a (Ni,Au)₃Sn₄ intermetallic compound (IMC) layer was formed at the interface. Due to the preferential consumption of Sn atoms within the solder matrix during aging, the solder matrix was transformed sequentially in the following order: β-Sn and η-phase, η-phase, and η-phase and ε-phase. In the bump shear test, the shear force was not significantly changed despite aging at 150 °C for 1000 h and most of the fractures occurred at the interfaces. The interfacial fracture was significantly related to the formation of brittle IMCs at the interface. The Sn-rich, Au–Sn/Ni flip chip joint was mechanically much weaker than the Au-rich, Au–Sn/Ni flip chip joint. The study results demonstrated that the combination of Sn-rich, Au–Sn solder and Ni under bump metallization (UBM) is not a viable option for the replacement of the conventional, Au-rich, Au–20Sn solder.