A review of silicon-based wafer bonding processes,an approach to realize the monolithic integration of Si-CMOS and Ⅲ-Ⅴ-on-Si wafers

The heterogeneous integration of Ⅲ-Ⅴ devices with Si-CMOS on a common Si platform has shown great promise in the new generations of electrical and optical systems for novel applications,such as HEMT or LED with integrated control cir-cuitry.For heterogeneous integration,direct wafer bonding(DWB)techniques can overcome the materials and thermal mis-match issues by directly bonding dissimilar materials systems and device structures together.In addition,DWB can perform at wafer-level,which eases the requirements for integration alignment and increases the scalability for volume production.In this paper,a brief review of the different bonding technologies is discussed.After that,three main DWB techniques of single-,double-and multi-bonding are presented with the demonstrations of various heterogeneous integration applications.Mean-while,the integration challenges,such as micro-defects,surface roughness and bonding yield are discussed in detail.     

Cu wire bond parameter optimization on various bond pad metallization and barrier layer material schemes

The use of copper wire for semiconductor package assembly has been gradually gaining acceptance throughout the industry over the last decade. Although copper has several advantages over gold for wire bonding applications, the manufacturing difficulties using copper wire have made high volume, fine pitch copper bonding slow to materialize. In recent years with the spike in gold prices, copper wire has become even more attractive, and this has driven many studies on the topic.Due to the propensity for copper to work harden upon deformation, which occurs during the ball bonding process as the capillary tip smashes the ball into the bond pad, a high amount of stress is transferred into the bond pad structure. This can result in catastrophic defects such as dielectric cracking or pad cratering. The current study aims to quantify the level of underlying bond pad damage with respect to various bond pad metallization and barrier layer schemes. A first bond parameter optimization was completed on each experimental group. The results indicate that barrier layer structure and composition have a significant impact on the presence of pad cratering. The experimental group containing only TiN as the barrier material showed a high occurrence of cratering, while groups with Ti and TiW barrier metals showed no cratering, even if a TiN layer was on top of the Ti. The bond pad metal thickness, on the other hand, does not appear to play a significant role in the prevention of bond pad cratering. Metal thickness values ranging from 0.825 to 2.025 μm were evaluated, and none had bond pad cratering other than the group with TiN as the barrier metal. In addition to the first bond parameter evaluations with various bond pad and barrier metal combinations, the initial free air ball (FAB) optimization is discussed.     

Channel access and interference issues in multi-code DS-CDMA wireless packet (ATM) networks

Multi-Code Direct-Sequence Code-Division-Multiple-Access (MC-CDMA) has been proposed as a flexible multiple access scheme for wireless packet networks that support a large variety of mobiles with different and even time-varying rates. Using MC-CDMA, traffic streams with significantly different transmission rates can be easily integrated into a unified architecture, with all the transmissions occupying the same bandwidth and having the same spread spectrum processing gain. In this paper, we address medium-access and interference issues in MC-CDMA wireless packet networks. For medium access, we propose and study Multi-Code CDMA (MC-CDMA) with Distributed-Queueing Request Update Multiple Access (DQRUMA) to form a unified bandwidth-on-demand fair-sharing platform for multi-rate wireless services. DQRUMA is an efficient demand-assignment multiple access protocol for wireless access and scheduling. Pseudo-Noise (PN) codes (primary codes) and optimal power levels are allocated to the mobiles on a slot-by-slot basis, and a Maximum Capacity Power Allocation (MCPA) criterion exploits the sub-code concatenation property of the MC-CDMA transmission. Simulation results show that the system provides close to ideal-access performance for multi-rate mobiles, both with homogeneous traffic characteristics and with a mix of heterogeneous traffic characteristics. Finally, we analyze the effects of MC-CDMA intercell interference on the reverse link (i.e., mobile to cell site) and investigate interference reduction by using the Maximum Capacity Power Allocation (MCPA) criterion. Our results show significant reduction in reverse-link MC-CDMA intercell interference is possible using the MCPA criterion.     

（NixZn0.825—xCu0.170Co0.005）Fe1.90O3.85铁氧体的电磁性能

采用配方式（ＮｉｘＺｎ０．８２５－ｘＣｕ０．１７０Ｃｏ０．００５）Ｆｅ１．９０Ｏ３．８５（简称ＮｉＣｕＺｎ铁氧体）在较宽的组成范围内（ｘ＝０．２９５～０．７５０）研究了ＮｉＣｕＺｎ铁氧体的电磁性能,发现ＮｉＣｕＺｎ铁氧体的μ,Ｑ以及温度特性随Ｎｉ含量ｘ的变化与ＮｉＺｎ铁氧体有很大不同,并对产生这种现象的原因进行了初步探讨。     

BaFe12O19包覆γ—Fe2O3复合磁粉的制备及其磁性能研究

采用表面包覆法合成了一系列不同包覆量的ＢａＦｅ１２Ｏ１９－γ－Ｆｅ２Ｏ３复合磁粉,采用Ｘ射线粉末衍射（ＸＲＤ）对样品进行物相分析,用振动样品磁强计（ＶＳＭ）测试样品磁性能,得到矫顽力和比饱和磁化强度随包覆量变化的关系曲线,由此讨论了过渡层的存在对样品磁性能的影响以及不同焙烧工艺条件下,样品磁性能的变化规律,在复合磁粉中ＢａＦｅ１２Ｏ１９的摩尔分数ｘ＝３０％～７０％,得到的复合磁粉性能较好（Ｈ＝４５     

Compact modeling of 0.35 μm SOI CMOS technology node for 4 K DC operation using Verilog-A

Compact modeling of MOSFETs from a 0.35 μm SOI technology node operating at 4 K is presented. The Verilog-A language is used to modify device equations for BSIM models and more accurately reproduce measured DC behavior, which is not possible with the standard BSIM model set. The model presented exhibits convergent behavior and is shown to be experimentally accurate at 4 K. No design tool currently in place exhibits convergence and/or accuracy over this range. The Verilog-A approach also allows the embedding of nonlinear length, width and bias effects into BSIM calculated curves beyond those that can be achieved by the use of different BSIM parameter sets. Nonlinear dependences are necessary to capture effects particular to 4 K behavior, such as current kinks. The 4 K DC behavior is reproduced well by the compact model and the model seamlessly evolves during simulation of circuits and systems as the simulator encounters SOI MOSFETs with different lengths and widths. The incorporation of various length/width and bias dependent effects into one Verilog-A/BSIM4 library, therefore, produces one model for all sets of devices called up in a given product design kit (PDK) for this technology node.     

BCI Competition 2003--Data set IIb: support vector machines for the P300 speller paradigm

We propose an approach to analyze data from the P300 speller paradigm using the machine-learning technique support vector machines. In a conservative classification scheme, we found the correct solution after five repetitions. While the classification within the competition is designed for offline analysis, our approach is also well-suited for a real-world online solution: It is fast, requires only 10 electrode positions and demands only a small amount of preprocessing.     

Peripheral Nerve‐Derived Matrix Hydrogel Promotes Remyelination and Inhibits Synapse Formation

Regeneration of injured nerve tissues requires intricate interplay of complex processes like axon elongation, remyelination, and synaptic formation in a tissue‐specific manner. A decellularized nerve matrix‐gel (DNM‐G) and a decellularized spinal cord matrix‐gel (DSCM‐G) are prepared from porcine sciatic nerves and spinal cord tissue, respectively, to recapitulate the microenvironment cues unique to the native tissue functions. Using an in vitro dorsal root ganglion–Schwann cells coculture model and proteomics analysis, it is confirmed that DNM‐G promotes far stronger remyelination activity and reduces synapse formation of the regenerating axons in contrast to DSCM‐G, Matrigel, and collagen I, consistent with its tissue‐specific function. Bioinformatics analysis indicates that the lack of neurotrophic factors and presence of some axon inhibitory molecules may contribute to moderate axonal elongation activity, while laminin β2, Laminin γ1, collagens, and fibronectin in DNM‐G promote remyelination. These results confirm that DNM‐G is a promising matrix material for peripheral nerve repair. This study provides more insights into tissue‐specific extracellular matrix components correlating to biological functions supporting functional regeneration.