Manipulating DNA molecules in nanofluidic channels

Nanofluidic channels of ∼40×60 nm (width × depth) were fabricated with focused ion beam (FIB) milling instrument on a silicon nitride (Si₃N₄) film. Stained λ-phage DNA molecules were driven into these open channels by capillary force and observed with fluorescence microscopy. The movements of DNA molecule in these channels were discussed. These sub-100 nm scale channels may be useful in studying single biomacromolecules.     

Microfluidic chip designs process optimization and dimensional quality control

The challenge of fabricating geometries with critical dimensions ranging from few microns down to 10 nm with high production rate is delaying the development of nanotechnology based products. Diverse research works have shown the capability of technologies such as UV lithography, nano imprint lithography and e-beam lithography to produce micro and nano features. However, their application for tooling purposes is relatively new and the potential to produce nanometer features with high volume and low cost is enormous. Considering possible implementation in a mass production environment the precision of measuring results and the accuracy of measurement relocation are very relevant. In this paper, the capability of producing with high volume Lab-on-chip devices through injection molding is evaluated. Preparation of master geometries was made in a Si wafer using e-beam lithography and reactive ion etching. Subsequent nickel electroplating was employed to replicate the obtained geometries on the tool, which was used to mold on transparent polymer substrates the functional structures. To assess the critical factors affecting the replication quality throughout the different steps of the proposed process chain, test geometries were designed and produced on the side of the functional features. The so-called “Finger Print” of the lithography and molding processes was qualitatively and quantitatively evaluated through scanning electron microscopy and atomic force microscopy respectively. The entire process chain is therefore characterized and the degree of replication among the different replication steps quantified with precise measurements using a high accuracy relocation technique on the produced key test geometries. Influence of injection molding process parameters, feature dimensions and orientation relative to the polymer flow direction have been assessed in respect of the replication fidelity of the produced micro/sub-μm channels. Finally the paper addresses product compliance with specifications, focusing on tolerances of vertical dimensions using a metrological approach: sub-μm features on silicon, nickel stampers and injection molded substrates are measured. Results of measurement uncertainty calculation, quantitative replication fidelity assessment, and dimensional tolerances at the nanometer scale verification are reported.     

Direct Fabrication of Nanoscale Light Emitting Diode on Silicon Probe Tip for Scanning Microscopy

We have fabricated a silicon microprobe integrated with a nanometer-sized light emitting diode (Nano-LED) on the tip. This paper describes the fabrication procedure and preliminary topographic testing results. The silicon probe with electrode pattern was made by wet-etching a silicon-on-insulator wafer using oxide as the mask. Subsequently, the probe tip was cut using a focused ion beam (FIB) to form a 150 nm-wide gap. Semiconductor nanoparticles (CdSe/ZnS core-shell nanoparticles) were electrostatically trapped and excited within the electrode gap made on the probe tip. The LED-tip is approximately 150 nm 150 nm. The nano-LED light intensity and current were measured as a function of the driving voltage up to 25 V. In addition to the electroluminescence peaks from the CdSe particles, possible emission from silicon dioxide doped in the FIB milling process was also observed in the measured spectra. Basic mechanical characteristics of the silicon probe were measured by mounting the probe on a tuning fork in a standard near-field scanning optical microscopy (NSOM) set up. It was observed that the drag force reduces the probe oscillation as the vibrating tip approached the near-field of the sample surface. The topographic images of a chromium test pattern on a glass substrate were successfully acquired by keeping the probe tip within roughly 5 nm from the sample surface. Although the probe tip shape and the location of the Nano-LED are yet to be further optimized before realizing near-field optical scanning experiment, the result showed its great promise as a new type of NSOM tip with the ldquoon-proberdquo light-source.     

Structure modification of M-AFM probe for the measurement of local conductivity

In order to realize the evaluation of electrical properties of materials in nanometer scale, a method to measure the local conductivity of materials was demonstrated. A microwave atomic force microscope (M-AFM) probe which can propagate and emit microwave signals was fabricated. An open structure of a waveguide at the tip of the probe was introduced by focused ion beam fabrication. The M-AFM combined a network analyzer and an AFM was used to measure a sample. The amplitude and phase of the reflection coefficient of the microwave signals were measured, thereby the electrical conductivities of metallic materials were determined. The conductivity obtained by this method is agreement well with that measured by a high-frequency conductometry.     

A sub-micron metallic electrothermal gripper

We report the design, fabrication, and characterization of a multiple bent beam, sub-micron metallic electrothermal gripper. A bottom electroplating mold for electrodes was patterned using electron beam lithography in an SU-8, followed by nickel electroplating. A top electroplating mold for a sub-micron metallic gripper with high aspect ratio bent beams (thickness of 1 μm, width of 350 nm) was prepared using electron beam lithography in a polymethyl methacrylate (PMMA), followed by nickel electroplating and dry release of the top and bottom molds. The sub-micron gripper was characterized using a nanomanipulator system installed in a dual column scanning electron microscopy/focused ion beam system. The ability of the jaw to close up to 1.39 μm displacement with high precision and reliability has been reproducibly observed at an applied current of 28 mA, corresponding to the maximum power consumption of 11.2 mW. Finite element modeling displacement results performed using ANSYS for effective bent beam widths of 370 nm showed a good agreement with the measured displacement results. The sub-micron gripper demonstrated herein will enable the reproducible manipulations with nano-scale resolution displacement and could provide an effective means of interface between nano-scale objects and the micro/macro scale robotic systems.     

Magnetic reversal of sub-100 nm nanostructures studied by a FIB-trimmed recording head

Arrays of sub-100 nm square islands have been fabricated by patterning perpendicular Co₇₀Cr₁₈Pt₁₂ continuous films using focused ion beam (FIB) lithography. The recording studies were performed on a quasi-static write/read tester using FIB trimmed recording heads with a write width of about 100 nm. We demonstrate the ability to write controlled magnetic patterns by addressing individual single-domain islands in dense island arrays achieving bit densities as high as 60 Gbit/in² and to read back the written information. The range of write current over which single islands can be written is modeled using a write model which includes the write field distribution and the island switching field distribution. A window is found over which individual islands can be addressed without switching nearest neighbors.     

Fast prototyping of high-aspect ratio, high-resolution X-ray masks by gas-assisted focused ion beam

The capacity of chemically-assisted focused ion beam (FIB) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number {Z}) coatings on X-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing for fast prototyping of high-aspect ratio, high-resolution masks for deep X-ray lithography for the LIGA process. In preliminary demonstrations, an automated FIB system operating at 30 keV with a gallium liquid metal source and an iodine gas injection system was used for direct milling into a few micrometer thick gold of microstructures into the sub-hundred nanometer regime. Three-dimensional micromachining in bulk diamond is also reported to illustrate the capability of the technique.This work was made possible under funding for California Institute of Technology from NASA general contract (# NAS7-1407), the partial funding for CAMD from the DARPA grant HI-MEMS Development and Manufacturing (contract # N66001-98-1-8926). Patrick Deshaye (Norsam) microsculpting work is also gratefully acknowledged.This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.     

The application of back-scattered electron imaging for characterization of pearlitic steels

The microstructures of pearlitic steel wire rods and steel wires are commonly characterized by secondary electron imaging (SEI)technique using scanning electron microscopy(SEM).In this work,a back-scattered electron imaging(BSEI)method is proposed to determine the microstructures of undeformed and deformed pearlitic steels with nanometer scale pearlite lamellae.The results indicate that BSEI technique can characterize the pearlite lamellas veritably and is effective in quantitative measurement of the mean s...     

基于平晶的非线性激光扫描直径测量系统

设计了一种基于平晶扫描的轴类零件直径测量系统。激光透射旋转的平晶产生扫描平行光,扫描光偏移光轴的距离是入射角及平晶自身参数的非线性函数,光电检测及计时电路获得测量周期和对应被测工件边缘的信号跳变时间,根据时间与转动角度的比例关系将所得时间量换算成入射角度,最终实现直径测量。利用刀口法进行标定实验,分别采用参数拟合法和RBF神经网络法确定实际非线性测量方程,完成了各测头的标定,进一步实现多测头系统标定,在100 mm的测量范围内,3σ重复性误差为0.006 mm,测量误差为±0.010 mm。     

Residual Stress Measurement on a MEMS Structure With High-Spatial Resolution

A new approach to the local measurement of residual stress in microstructures is described in this paper. The presented technique takes advantage of the combined milling-imaging features of a focused ion beam (FIB) equipment to scale down the widely known hole drilling method. This method consists of drilling a small hole in a solid with inherent residual stresses and measuring the strains/displacements caused by the local stress release, that takes place around the hole. In the presented case, the displacements caused by the milling are determined by applying digital image correlation (DIC) techniques to high resolution micrographs taken before and after the milling process. The residual stress value is then obtained by fitting the measured displacements to the analytical solution of the displacement fields. The feasibility of this approach has been demonstrated on a micromachined silicon nitride membrane showing that this method has high potential for applications in the field of mechanical characterization of micro/nanoelectromechanical systems     

Magnetic lithography for servowriting applications using flexible magnetic masks nanofabricated on plastic substrates

Magnetic lithography (ML) is a process qualitatively analogous to contact optical lithography which transfers information from a nanopatterned magnetic mask (analog of optical photomask) to magnetic media (analog of photoresist), and is interesting for applications in instantaneous parallel magnetic recording, in particular for servowriting applications. The magnetic mask consists of nanopatterned magnetically soft material (FeNiCo, FeCo) on a thin flexible plastic substrate, typically Polyethylene teraphtalate (PET) or polyimide. When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. Flexible substrate of the magnetic mask offers superior compliance to magnetic media which is likely to have imperfect flatness and surface particulate contamination. We discuss nanofabrication challenges of magnetic masks on plastic substrates, including electron beam lithography, electroplating and lift-off processing on the nanometer scale, adhesion of metal thin films on PET and polyimide substrates, and release of plastic films from rigid substrates used during the processing. We present results on fabricated magnetic masks, magnetic force microscopy images of the magnetic transition patterns and disk spinstand tests of servowritten patterns.     

Optical Near-Field Probe Integrated With Self-Aligned Bow-Tie Antenna and Electrostatic Actuator for Local Field Enhancement

Microelectromechanical systems (MEMS)-based near-field scanning optical microscopy (NSOM) probes with a bow-tie antenna structure consisting of two metal triangular electrodes separated by a narrow gap have been designed and fabricated. An electrostatic actuator is integrated on this bow-tie probe to decrease the gap width for enhancing the optical near-field intensity. A self-alignment process based on deep reactive ion etching and wet anisotropic etching is established to fabricate the symmetric bow-tie structure. The static and dynamic actuations of electrostatic actuators are examined. With the mechanical resonance of the antenna structure to lateral direction, NSOM imaging is performed in the visible range, and the subwavelength resolution beyond the diffraction limit of light is demonstrated.1655     

Design and performance of a micro-sized biomorphic compound eyewith a scanning retina

Proposes a design of a biomorphic micro visual sensor equipped with a mechanical scanning system. The sensor is inspired by the structure of the fly's compound eye, which was found to possess a unique muscle and tendon actuation system for its scanning retina. The improvement in micro-opto-electro-mechanical systems encourages the design of reliable, efficient, and integrated smart visual sensors for robotic applications, in particular, for the autonomous visually guided navigation of mobile robots. The authors have verified the effect of retinal scanning for a robotic visual system through the construction of a large-scale prototype at the millimeter scale. The performance of a newly fabricated microelectromechanical system prototype whose size approaches the order of the insects' compound eyes is then evaluated in comparison with that of the large-scale prototype. The micro-sized visual sensor is composed of a scanning microlens array (120 μm in lens diameter) and a photo-diode array. The actuation of the microlens array induces a rotation of the visual axes. According to the principle of retinal scanning, the micro-sensor is able to retrieve the local angular velocity with enhanced reliability     

Stroboscopic interferometer system for dynamic MEMScharacterization

We describe a computer-controlled stroboscopic phase-shifting interferometer system for measuring out-of-plane motions and deformations of MEMS structures with nanometer accuracy. To aid rapid device characterization, our system incorporates (1) an imaging interferometer that records motion at many points simultaneously without point-by-point scanning, (2) an integrated computer-control and data-acquisition unit to automate measurement, and (3) an analysis package that generates sequences of time-resolved surface-height maps from the captured data. The system can generate a detailed picture of microstructure dynamics in minutes. A pulsed laser diode serves as the stroboscopic light source permitting measurement of large-amplitude motion (tens of micrometers out-of-plane) at kilohertz frequencies. The high out-of-plane sensitivity of the method makes it particularly suitable for characterizing actuated micro-optical elements for which even nanometer-scale deformations can produce substantial performance degradation. We illustrate the capabilities of the system with a study of the dynamic behavior of a polysilicon surface-micromachined scanning mirror that was fabricated in the MCNC MUMPS foundry process     

微机械陀螺DRIE刻蚀过程中的局域掩膜效应

在微机电系统(MEMS)制造中,深反应离子刻蚀(DRIE)过程的精度是影响器件特性的重要因素之一.本文设计了一种完全对称弹性梁结构的模态匹配式陀螺的原型器件,以此为对象研究了局域掩膜图形对于DRIE刻蚀过程的影响.器件的测试结果表明驱动和检测模态有明显的失配,该失配的发生原因除了气体阻尼,更主要来源于驱动和检测结构弹性梁尺寸的工艺偏差.在分析了实验过程及结果的基础上可以认为,除了典型的DRIE滞后效应等因素外,器件结构的局域掩膜效应加剧了工艺偏差:对称弹性梁结构周边的非对称掩膜图形导致了刻蚀气体分布的局部不均匀,增加了DRIE刻蚀的侧蚀偏差.     

一种HIRFL束流发射度测量系统的研究

对HIRFL束流发射度测量系统中以图形图像技术为基础的多孔屏法进行了研究，在图像处理过程中引入了高斯拟合、图像轮廓跟踪等技术。并以此为基础开发了一套软件系统，实现对束流发射度等参数的实时测量，同时具备一些重要图形的显示功能。该系统成功的将传统的荧光靶束流定性观测改进为精确的定量测量，而且测量速度也有了显著的提高。     

Micro-mirror laser scanner combined with a varifocal mirror

A laser beam scanning system consisting of a scanning micro-mirror and a varifocal micro-mirror is fabricated for laser beam sensing with variable beam diameter. The scanning micro-mirror is operated under the resonant oscillation condition with an electrostatic comb-drive actuator. The varifocal micro-mirror is driven by a bending moment generated at the circumference of mirror with a parallel-palate electrostatic actuator. The scanning micro-mirror and the varifocal mirror are fabricated on a silicon on insulator wafer. The rotational angle of 9° at 766 Hz is obtained at the voltage of 300 V. The spot size of the laser beam is adjusted from 0.5 to 3.5 cm at the distance of 43 m by changing varifocal voltage. The proposed scanning system can be useful for several sensing techniques.     

Tutorial - Robotics in the small Part II: Nanorobotics

Nanorobotics is the study of robotics at the nanometer scale, and includes robots that are nanoscale in size, i.e., nanorobots (which have yet to be realized), and large robots capable of manipulating objects that have dimensions in the nanoscale range with nanometer resolution, i.e., nanorobotic manipulators. Knowledge from mesoscopic physics, mesoscopic/supramolecular chemistry, and molecular biology at the nanometer scale converges to form the field. Various disciplines contribute to nanorobotics, including nanomaterial synthesis, nanobiotechnology, and microscopy for imaging and characterization. Such topics as self-assembly, nanorobotic assembly, and hybrid nanomanufacturing approaches for assembling nano building blocks into structures, tools, sensors, and actuators are considered areas of nanorobotic study. A current focus of nanorobotics is on the fabrication of nanoelectromechanical systems (NEMS), which may serve as components for future nanorobots. The main goals of nanorobotics are to provide effective tools for the experimental exploration of the nanoworld, and to push the boundaries of this exploration from a robotics research perspective.     

Air-damped microresonators with enhanced quality factor

It is known that the dissipative damping force due to the air film trapped between the bottom of surface micromachined resonators and the substrate on which they are fabricated decreases in magnitude as the separation between the two increases. The practical outcome of this is that microresonators located close to a substrate will have higher damping and a lower quality factor Q. In order to further investigate this effect and compare experimental findings with theory, a new test device that enables modulation of the damping interaction between a surface micromachined resonator and the substrate has been fabricated. The device consists of a surface micromachined polysilicon microresonator, which is self-elevated out of the plane of the substrate using a bimorph beam. A second, identical microresonator lying parallel to the plane of the substrate has also been fabricated. Both devices have been fabricated using the polysilicon multiuser microelectromechanical systems (MEMS) processes (polyMUMPs). The resonator-to-substrate separation of the elevated resonator is varied by changing the temperature of the bimorph beam, and the Q factors for different separations have been measured. Experimental results show that the elevated microresonators have Q values which are 65% higher than the in-plane microresonators. These experimental findings show good agreement with the theoretical model of damping used.     

Value-added defect testing techniques

In the transition from micrometer to nanometer technologies, many things have changed, but customer demands for low defects-per-million (DPM) failure rates have not. Modern electronic and mechanical systems contain an ever-increasing number of semiconductor components with each component containing ever-increasing gate counts per chip. With traditional quality levels, the reliability of these systems can degrade severely. Therefore, system providers must dramatically improve the reliability of each component to maintain system reliability at all levels. This article describes advanced design-for-manufacturability (DFM) test methods that target defect coverage, yield learning, and cost. The authors argue that testing can be useful for more than filtering chips. It can directly help target test pattern provide DFM tools and reduce overall costs.