三维微弹簧型MEMS探卡的设计和制备

随着IC器件上的I/O尺寸减小和密度增加,与之通过接触来进行电性能测试的探卡密度也要相应增加,传统手工制作的环氧树脂针形探卡难以满足使用要求,使用MEMS技术制作探卡成为发展的趋势,但是当前MEMS探卡的主要问题是不能承受和产生破坏焊垫表面氧化层和污染层所需的应力.本文提出了一种简支梁结构、通过多次电镀工艺制作的三维弹性MEMS探卡,这种探卡可以承受更大应力,并且具有较小的自身电阻.针对间距为250 μm阵列排布的器件I/O,使用ANSYS有限元方法对弹簧型探卡进行了结构分析和设计,采用UV-LIGA工艺制备探卡,最后对探卡的力学性能进行了测试.     

Thermally actuated microprobes for a new wafer probe card

A new type of MEMS microprobe was designed and fabricated which can be used for a nest generation wafer probe card. A prototype MEMS probe card consisting of an array of microprobes individually actuated by bimorph heating to make contact with the test chip was also fabricated. This probe card is called the CHIPP (Conformable, HIgh-Pin count, Programmable) card and can be designed to contact up to 800 I/O pads along the perimeter of a 1-cm² chip with a microprobe repeat distance of approximately 50 μm. Microprobes for a prototype CHIPP probe card have been fabricated with a variety of cantilever structures including Al-SiO₂, W-SiO₂ and Al-Si bimorphs, and with the resistive heater placed either inside or on the surface of the cantilever. Ohmic contacts between tips and bond pads were tested with contact resistance as low as 250 mΩ. The deflection efficiency varies from 5.23-9.6 μm/mW for cantilever lengths from 300-500 μm. The maximum reversible deflection is in the range of 280 μm. The measured resonant frequency is 8.16 kHz for a 50×500 μm device and 19.4 kHz for a 40×300 μm device. Heat loss for devices operating in air was found to be substantially higher than for vacuum operation with a heat loss ratio of about 2/1 for a heater inside the structure, and 4.25/1 for a structure with the heater as an outer layer of the cantilever     

GaAs HBT中测信号防护处理

在集成电路前段代工厂制作完成后,为确保出货电性及封装良率,客户会要求出货前对器件进行电性及可靠度测试。由于HBT砷化镓芯片高集成度及高频等因素,在中测时存在振荡与干扰,无法得到真实的电性良率,而且不同于手动探针台每次只测试单一测试项,中测要对晶粒同时进行所有电性测试,进一步造成电性良率失真。针对此问题,对中测探针卡进行改良,通过比较TaN片电阻均匀性与手动探针台测量结果,以及观察电流值的高斯分布,证实中测结果的合理性。结果表明,对探针卡进行电磁屏蔽及电路匹配后,改善前后电性良率有显著提升,能满足快速且准确的检测目的。     

Wafer-level testing with a membrane probe

The authors describe a proprietary membrane probe card that addresses the needs of testing VLSI devices at the wafer level. The membrane probe allows the testing of devices with a high pin count at operating speed, while allowing a complete package test at the wafer level. The concepts and structure of the probe are examined, and its performance is demonstrated by time-domain and frequency-domain measurements of the typical electrical characteristics of a VLSI digital probe that accesses 272 pads at a pitch of 110 μm. Applications to a bipolar ECL (emitter-coupled logic) flash A/D (analog-to-digital) converter, a bipolar ECL D/A converter, an application-specific CMOS IC, an NMOS VLSI central processing unit, and area-array solder bumps are presented     

Design principle of micro-mechanical probe for lateral-deflection-controlled friction force microscopy

Design principles of lateral-deflection-controlled friction force microscopy (FFM) are presented. Lateral-deflection-controlled FFM can overcome a fundamental problem of dual-axis FFM and can provide higher lateral resolution by compensating for friction force and providing effectively high rigidity to the probe. In this paper, key micro components are investigated: micro structures for detection of lateral probe deflection and for lateral drive of the probe. The micro structure for deflection detection is fabricated at the end of the probe and is used in combination with an optical lever method. The micro structure that reflects light (positive type) can provide higher sensitivity than a conventional structure that does not reflect light (negative type). For the probe lateral drive, a micro conduction structure that connects the probe with a support beam is used. A micro electrical conduction structure using stiction is introduced, and its feasibility is experimentally confirmed. These micro structures can improve the measurement accuracy.     

New closed-form solution for kinematic parameter identification ofa binocular head using point measurements

This paper proposes a new closed-form solution for identifying the kinematic parameters of an active binocular head having four revolute joints and two prismatic joints by using three-dimensional (3-D) point (position) measurements of a calibration point. Since this binocular head is composed of off-the-shelf components, its kinematic parameters are unknown. Therefore, we can not directly apply those existing nonlinear optimization methods. Even if we want to use the nonlinear optimization methods, a closed-form solution can be first applied to obtain accurate enough initial values. Hence, this paper considers only methods that provide closed-form solutions, i.e., those requiring no initial estimates. Notice that most existing closed-form solutions require pose (i.e., both position and orientation) measurements. However, as far as we know, there is no inexpensive technique which can provide accurate pose measurements. Therefore, existing closed-form solutions based on pose measurements can not give us the required accuracy. As a result, we have developed a new method that does not require orientation measurements and can use only the position measurements of a calibration point to obtain highly accurate estimates of kinematic parameters using closed-form solutions. The proposed method is based on the complete and parametrically continuous (CPC) kinematic model, and can be applied to any kind of kinematic parameter identification problems with or without multiple end-effecters, providing that the links are rigid, the joints are either revolute or prismatic and no closed-loop kinematic chain is included.     

Measurement system for low force and small displacement contacts

To support the continued miniaturization of electrical contacts in multichip systems, three-dimensional (3-D) systems, wafer probe cards, and MEMS relays, there is a need for combined measurements of electrical and mechanical phenomena during contact formation. We have carried out a study of electrical contacts in the nN-mN force range for future generation probe cards and novel electronic packaging. One critical phenomenon in the contact formation process is nm-scale deformation of the material layers. To directly study this contact displacement, we have designed a measurement system comprised of a piezoresistive cantilever and an optical interferometer. Together, this system simultaneously measures contact resistance (mOhm to kOhm), force (nN to mN), and displacement (nm-/spl mu/m). These measurements allow the first direct observation of contact mechanical behavior in this important application range. These measurements show that asperities at the contact surface dominate the behavior of the contacts, causing deviations from the Hertzian model of elastic contacts. This paper describes the design and construction of this apparatus, and the operation in a contact mechanics experiment.     

A Micromachined Kelvin Probe With Integrated Actuator for Microfluidic and Solid-State Applications

This paper reports on a micromachined Kelvin probe structure with an integrated scanning tip and an integrated electrothermal actuator that provides axial dithering motion. The device is fabricated from metal foil by a modified microelectrodischarge machining process that allows electrical isolation within the device. In particular, it permits the incorporation of a wide epoxy plug that creates an insulating gap with low parasitic capacitance between the probe and the actuator. The epoxy structures are found to withstand the thermal and mechanical conditions encountered during device operation. The device is used to measure changes in the external surface potential of a parylene microfluidic channel as a function of varying pH of liquid inside the channel. A contact potential difference of$approx 6~ V$is measured for a change in pH from 4 to 8 within the channel. The device is also used to map embedded charge in a thin$ SiO_2$layer on a Si substrate, showing it to be suitable for monitoring microelectronics manufacturing processes.hfillhbox[1072]     

Signal-to-Noise Ratio Fundamental Limitations in Continuous-Time Linear Output Feedback Control

In the present technical note we study the fundamental limitation on stability that arise when an additive coloured Gaussian noise (ACGN) channel is explicitly considered over either the control or measurement paths of a linear time invariant (LTI) feedback loop. By considering a linear setting we can naturally express the fundamental limitation as a lower bound on the channel signal-to-noise ratio (SNR) required for stabilisability. We start by first obtaining a closed-form expression for the squared L ₂ norm of a partial fraction expansion with repeated poles in the Laplace domain. We then use the squared L ₂ norm result to obtain the closed-form expression for the infimal SNR required for stabilisability. The proposed closed-form includes the case of repeated unstable plant poles and non minimum phase (NMP) zeros.     

Patterned electroplating of micrometer scale magnetic structures on glass substrates

This paper has developed a new method of micro patterned electroplating that enables the fabrication of micrometer scale magnetic structures on glass substrates. In contrast to other methods, the process as developed here leaves the surrounding substrate area untouched: that is there is no seed layer present except underneath the magnetic structures. Patterned cobalt layers of thicknesses up to 8 /spl mu/m were fabricated exhibiting high saturation (1.5 T) and low coercive force. These layers have been used to create micrometer scale magnetic poles (magnetic tweezers) for biological and biophysical applications, where a clean untouched glass substrate in the sample area is most important. The technique, however, can be used in any situation where a residual seed layer on the surrounding area is unwanted, and afterwards removal of this seed layer is difficult or impossible.     

On design and optimization of face verification systems that are smart-card based

The optimization of a smart card face verification system is a very complex process with many key factors to consider. It involves the investigation of the effect the system parameters have on the system performance measured in terms of accuracy and speed. As the parameters involved are not independent, the search space is of exponential complexity. In practice only partial optimization is feasible with many parameters forced to take default values. We argue that the key options to optimize are image resolution or/and image pre-processing. In addition the main design issue is the degree of compression that can be applied to the probe image before it is transmitted to the smart card. In this work we investigate different optimization strategies by considering both image compression and image resolution, and demonstrate that both the system performance and speed of access can be improved by the jointly optimized parameter setting and the level of probe compression. The experimental results obtained on the XM2VTS database suggest that the choice of one strategy over another is a matter of the time available for the system design, system performance, and response time.     

A closed-form solution to tensor voting: theory and applications

We prove a closed-form solution to tensor voting (CFTV): Given a point set in any dimensions, our closed-form solution provides an exact, continuous, and efficient algorithm for computing a structure-aware tensor that simultaneously achieves salient structure detection and outlier attenuation. Using CFTV, we prove the convergence of tensor voting on a Markov random field (MRF), thus termed as MRFTV, where the structure-aware tensor at each input site reaches a stationary state upon convergence in structure propagation. We then embed structure-aware tensor into expectation maximization (EM) for optimizing a single linear structure to achieve efficient and robust parameter estimation. Specifically, our EMTV algorithm optimizes both the tensor and fitting parameters and does not require random sampling consensus typically used in existing robust statistical techniques. We performed quantitative evaluation on its accuracy and robustness, showing that EMTV performs better than the original TV and other state-of-the-art techniques in fundamental matrix estimation for multiview stereo matching. The extensions of CFTV and EMTV for extracting multiple and nonlinear structures are underway.     

Electromechanical coupling correction for piezoelectric layered beams

This paper deals with the bending of layered piezoelectric beams (multimorphs) subjected to arbitrary electrical and mechanical loading. Weinberg (1999) obtained a closed-form solution to this problem using Euler-Bernoulli beam theory and integrated equilibrium equations. In his analysis, Weinberg assumes that the electric field is constant through the thickness of the piezoelectric layers. This approximation is valid for materials with small electromechanical coupling (EMC) coefficients. In this paper, we relax this constraint and obtain a solution which accounts for the effect of strain on the electric field in the layers. We find that Weinberg's solution can be extended to arbitrary EMC with a simple correction to the moment of inertia I of the piezoelectric layers. The EMC correction amounts to replacing I with (1+/spl xi/)I, where /spl xi/ is the square of the expedient coupling coefficient. The error in beam curvature introduced by neglecting the effect of EMC is shown to be proportional to /spl xi/. This effect can be quite significant for modern piezoelectric materials which tend to have large EMC coefficients. The formulation is applied to three example cases: a cantilever unimorph, an asymmetric bimorph and a three-layer multimorph with an elastic core. The theoretical predictions for the last two examples are compared to simulations using the finite-element method (FEM) and found to be in excellent agreement.     

A cryptographic study of tokenization systems

Payments through cards have become very popular in today’s world. All businesses now have options to receive payments through this instrument; moreover, most organizations store card information of its customers in some way to enable easy payments in future. Credit card data are a very sensitive information, and theft of this data is a serious threat to any company. Any organization that stores credit card data needs to achieve payment card industry (PCI) compliance, which is an intricate process where the organization needs to demonstrate that the data it stores are safe. Recently, there has been a paradigm shift in treatment of the problem of storage of payment card information. In this new paradigm instead of the real credit card data a token is stored, this process is called “tokenization.” The token “looks like” the credit/debit card number, but ideally has no relation with the credit card number that it represents. This solution relieves the merchant from the burden of PCI compliance in several ways. Though tokenization systems are heavily in use, to our knowledge, a formal cryptographic study of this problem has not yet been done. In this paper, we initiate a study in this direction. We formally define the syntax of a tokenization system and several notions of security for such systems. Finally, we provide some constructions of tokenizers and analyze their security in light of our definitions.     

A selective review of direct, semi-inverse and inverse eigenvalue problems for structures described by differential equations with variable coefficients

Summary This selective review (with emphasis on the word “selective”) gives only a taste of extensive research that has been conducted since 1759 when Leonhard Euler posed, apparently for the first time, a boundary value problem. Since then numerous studies have been conducted for rods, Bernoulli-Euler beams, Bresse-Timoshenko beams, Kirchhoff-Love and Mindlin-Reissner plates and shells and structures analyzed via finer, higher-order theories. This selective review classifies the solutions as belonging to either of three main classes: (1) direct problems, (2) semi-inverse problems, (3) inverse problems. In addition, some new closed-form solutions are reported, that have been obtained via posing an inverse vibration problem. Due to the huge body of literature, author limits himself with discussing classic theories of structures.     

Using Trusted Email to Prevent Credit Card Frauds in Multimedia Products

This paper focuses on credit card fraud in Multimedia Products, which are soft-products. By soft-products, we mean intangible products that can be used and consumed without having them shipped physically, such as software, music and calling cards (calling time). The demand for soft-products, mainly Multimedia Products, on the Internet has grown in the last few years and is rapidly increasing. Credit card fraudulent transactions on such products are very easy to conduct, while very difficult to recover, compared to the fraud cases in hard-products transactions. This paper classifies the types of products sold on the Internet, and the usual fraud occurred in each type. It summarizes some of the existing best practices to prevent credit card fraud. Finally, it introduces the use of a Trusted Email as a way to authenticate the customer and to simulate his/her physical address (since on these products no actual shipping will happen).     

智能卡技术在数字式预收费电表中的应用

本文介绍了智能卡数字式预付费电表的软、硬件结构,以及电表智能卡的数据格式、通讯规程     

The model-based dynamic hand posture identification using genetic algorithm

This paper proposes a new hand posture identification system which applies genetic algorithm to develop an efficient 3D hand-model-fitting method. The 3D hand-model-fitting method consists of (1) finding the closed-form inverse kinematics solution, (2) defining the alignment measure function for the wrist-fitting process, and (3) applying genetic algorithm to develop the dynamic hand posture identification process. In contrast to the conventional computationally intensive hand-model-fitting methods, we develop an off-line training process to find the closed-form inverse kinematics solution functions, and a fast model-based hand posture identification process. In the experiments, we will illustrate that our hand posture identification system is very effective. Received: 10 April 1997 / Accepted: 18 June 1998     

Gimbal-less MEMS two-axis optical scanner array with high fill-factor

In this paper, we report on a MEMS-based two-axis optical scanner array with a high fill factor (>96%), large mechanical scan angles (/spl plusmn/4.4/spl deg/ and /spl plusmn/3.4/spl deg/), and high resonant frequencies (20.7 kHz). The devices are fabricated using SUMMiT-V, a five-layer surface-micromachining process. High fill factor, which is important for 1/spl times/N/sup 2/ wavelength-selective switches (WSSs), is achieved by employing crossbar torsion springs underneath the mirror, eliminating the need for gimbal structures. The proposed mirror structure can be readily extended to two-dimensional (2-D) array for adaptive optics applications. In addition to two-axis rotation, piston motion with a stroke of 0.8 /spl mu/m is also achieved. [1496].     

Throughput in Processor-Sharing Queues

Processor-sharing queues are often used to model file transmission in networks. While sojourn time is a common performance metric in the queueing literature, average transmission rate is the more commonly discussed metric in the networking literature. Whereas much is known about sojourn times, there is little known about the average service rate experienced by jobs in processor-sharing queues. We first define the average rate as observed by users and by the queue. In an M/M/1 processor-sharing queue, we give closed-form expressions for these average rates, and prove a strict ordering amongst them. We prove that the queue service rate (in bps) is an increasing function of the minimum required average transmission rate, and give a closed-form expression for the marginal cost associated with such a performance requirement. We then consider the effect of using connection access control by modeling an M/M/1/K processor-sharing queue. We give closed-form expressions for average transmission rates, and discuss the relationship between the queue service rate (in bps), the queue limit, the average rate, and the blocking probability