This PDF file contains the front matter associated with SPIE Proceedings Volume 6882, including the Title Page, Copyright information, Table of Contents, the Conference Committee listing, and Plenary Paper.

The challenge in manufacturing disposable bio micro-fluidic devices centers on making complex structures with controlled wetting and adhesion characteristics that can be used with fluorescence detection at a very low cost of < $1 a part. We will report on a new low fluorescence UV curable material that can be patterned in the Contact Liquid Photolithographic Polymerization (CLiPP) process developed at U Colorado.

For some time, the micro-optics and photonics fields have relied on fabrication processes and technology borrowed from the well-established silicon integrated circuit industry. However, new fabrication methodologies must be developed for greater flexibility in the machining of micro-optic devices. To this end, we have explored grayscale lithography as an enabler for the realization of such devices. This process delivers the ability to sculpt materials arbitrarily in three dimensions, thus providing the flexibility to realize optical surfaces to shape, transform, and redirect the propagation of light efficiently. This has opened the door for new classes of optical devices. As such, we present a fiber-to-waveguide coupling structure utilizing a smoothly contoured lensing surface in the device layer of a silicon-on insulator (SOI) wafer, fabricated using grayscale lithography. The structure collects light incident normally to the wafer from a singlemode optical fiber plugged through the back surface and turns the light into the plane of the device layer, focusing it into a single-mode waveguide. The basis of operation is total internal reflection, and the device therefore has the potential advantages of providing a large bandwidth, low polarization sensitivity, high efficiency, and small footprint. The structure was optimized with a simulated annealing algorithm in conjunction with two-dimensional finite-difference time-domain (FDTD) simulation accelerated on the graphics processing unit (GPU), and achieves a theoretical efficiency of approximately seventy percent, including losses due to Fresnel reflection from the oxide/silicon interface. Initial fabrication results validate the principle of operation. We discuss the grayscale fabrication process as well as the through-wafer etch for mechanical stabilization and alignment of the optical fiber to the coupling structure. Refinement of the through-wafer etch process for high etch rate and appropriate sidewall taper are addressed.

The high demand for beam shaping technology by the display industry has lead to higher resolutions, smaller pixel pitch and reduced costs. Nowadays high quality, nematic Liquid Crystal on Silicon microdisplays (LCoS) with resolutions of 1920 × 1080 pixels and 8 μm pixel pitch are available. The optical properties of these microdisplays allow for their application as an adaptive optical element where instantaneous change between arbitrary beam profiles is necessary. Laser material processing which often requires high beam qualities with various beam profiles is one industry where this technology could be applied. In this paper, a compact beam shaping setup and simple characterization methods for practical use of the LCoS at micromachining stations are presented.

The use of microscanning mirrors in mobile laser projection systems demands for robust fabrication technologies. Dust, change in humidity and temperature can only be tolerated if the fragile devices are enclosed in a hermetic package. A novel fabrication process is presented based on two 30 micron thick epitaxially deposited silicon layers and a buried interconnection layer. This technology allows the fabrication of stacked combdrives for electrostatic mirror actuation and lateral feedthroughs needed for hermetic encapsulation with standard wafer bonding processes. High display resolution requires large scan angles of the mirror plate. Therefore, a fabrication technology for structured glass wafers is presented to provide deep cavities for large mirror plate movements. A solution for effective laser spot reflex suppression is presented based on a static tilt of the mirror plate in relation to the glass cover wafer during eutectic bonding. By doing so, the reflex generated at the glass surfaces is shifted out of the image area. The cavity pressure of packaged devices has been measured showing the necessity of a getter layer in order to provide cavity pressures below 1 mbar. The performance of a packaged device with integrated getter layer has been evaluated. A driving amplitude of only 6 V is needed to achieve scan angles of above 50 deg. White light interferometric measurements showed excellent planarity of the mirror plate with a radius of curvature of about 18 m.

Micro-positioning stages fabricated using Micro Electro Mechanical Systems (MEMS) based processes have been critical in enabling micro/nano manipulation and probing. These stages have been extensively used in micro-force sensors, scanning probe microscopy and micro optical lens scanners. This paper presents the design, kinematic and dynamic analysis, fabrication and characterization of a novel monolithic micro-positioning XY stage. The design of the proposed micro-positioning stage is based on a Parallel Kinematic Mechanism (PKM). The PKM based design decouples the motion in the XY direction. Additionally, it restricts the parasitic rotation of the end-effector (table) of the micro-positioning stage while providing an increased motion range. The motion of the stage is linear in the operating range thus simplifying its kinematics. The truss like parallel kinematic mechanism design of the stage structure reduces its mass while keeping the stage stiffness high. This leads to a high natural frequency of the micro-positioning stage (1250Hz) and a high Q-factor of 156. The stage mechanism is fabricated on a Silicon-On-Insulator (SOI) substrate and is actuated by integrated electrostatic rotary comb drives. The fabrication process uses multi-layer patterning along with an Inductively Coupled Plasma Deep Reactive Ion Etching (ICP-DRIE). The use of ICP-DRIE enables the high aspect ratio etching that is required for the stage fabrication and its optimal actuation using the integrated electrostatic rotary comb drives. The fabricated stages have a motion range of more than 30 microns of decoupled displacements along the X and Y directions at a driving voltage of 200V.

For applications such as computers, cellular telephones and Microsystems, it is essential to reduce the size and the weight of DC-DC converters. To miniaturize passive components, micromachining techniques provide solutions based on low-temperature process compatible with active part of the converter. This paper deals with the integration on silicon of "spiral-type" inductor topology. Electroplating techniques are used to achieve the copper conductor and the CoNiFe laminated magnetic core and several investigations on the electroplating bath's parameters have been realized in order to obtain the adequate magnetic properties. Finally, a 1μH micro-inductor prototype has been characterized.

Rotation of structures fabricated by planar processing into out-of-plane orientations can be used to greatly increase the 3-dimensionality of microstructures. Previously this has been achieved by a self-assembly process based on surface tension in meltable hinges. An important application is in fabricating vertical inductors on silicon, to reduce the substrate coupling and thus increase quality factor and self-resonance frequency. Previous processes have used copper tracks, and Pb-Sn hinges. However, the use of Cu limits potential applications because of oxidation, since the final structure is not embedded. Moreover, a substitute hinge material is also required, as a result of legislative restrictions on Pb use. In this paper, Au is used as an alternative to Cu for the fabrication of self-assembled 3D inductors. A process has been developed to overcome photoresist deterioration problems due to the alkaline nature of Au electro-deposition solutions. Furthermore, pure Sn is used instead of Pb-Sn as the hinge material. A Ni metal layer is introduced between the Au coils and the Sn hinge to prevent inter-diffusion and formation of eutectic Au-Sn compounds. Finally a gold capping technique is proposed to protect the Sn hinge from oxidation during hinge reflow. The fabrication techniques developed here are compatible with post-processing on active CMOS circuits, and can be adopted for other MEMS applications.

Proton beam writing (PBW) is a lithographic technique that utilizes MeV protons in a direct write mode to fabricate micro/nano features in suitable resist material (E.g PMMA, SU-8, silicon, Foturan). These micro/nano structures may be used in an electroplating step to yield robust metallic stamps/molds for the replication of the original and lends itself to the fabrication of micro/nano fluidic channels that are important components in devices such as biophotonic chips. Another feature of proton bombardment is its ability to induce an increase in refractive index along the ions path, in particular at the end of its range where there is substantial nuclear scattering. This allows PBW to directly write buried waveguides that can be accurately aligned with fluidic channels. Polydimethylsiloxane (PDMS) is an optically clear, biocompatible polymer that can be readily used with a mold (such as that created with PBW) and easily sealed so as to produce biophotonic chips containing micro/nano fluidic channels. This has lead us to favour PDMS as the base material for our work on the development of these biophotonic chips. The present work is concerned with the production of integrating channel waveguides in PDMS chips, so as to have a working device that may be used to detect fluorescently tagged biological samples. For this we have adopted two approaches, namely(1) directly embedding optical fibres in the polymer and (2) using PBW to directly write buried waveguides in the polymer.

Multi-project-wafer (MPW) services provide an economical route for prototyping of new electronic circuit designs. However, addition of MEMS functionality to MPW circuits by post-processing (also known as MEMS-last processing) is difficult and inefficient because MPW typically yields individual dies. One solution to this problem is to embed the MPW dies in a carrier wafer prior to MEMS processing. We have developed a process which allows 300 μm-thick CMOS dies to be embedded in a BSOI (bonded silicon-on-insulator) carrier prior to low-temperature processing for integration of metal MEMS. Deep reactive ion etching (DRIE) with an STS Multiplex ICP etcher is used to form cavities in the device layer of a BSOI wafer. By adjusting the passivation and etching cycles, the DRIE process has been optimized to produce near-vertical sidewalls when stopping on the buried oxide layer. The cavity sizes are closely matched to the die dimensions to ensure placement of the dies to within ±15 μm. Dies are placed in all the cavities, and then a photoresist layer is deposited by spin-coating and patterned to provide access to the required IC contact pads. The photoresist has the dual role of securing the dies and also planarizing the top surface of the carrier. After an appropriate baking cycle this layer provides a suitable base for multi-level electroplating or other low-temperature MEMS processing.

This paper reports a wet anisotropic etching process for the fabrication of silicon MEMS structures with rounded concave and sharp convex corners on (100)-Si wafers. The process is developed using tetramethyl ammonium hydroxide (TMAH) at different concentrations (10, 20, 25 wt%) and a small amount (0.1% v/v) of non-ionic surfactant NC-200. The etching characteristics are measured on a silicon hemisphere and several Si(100) wafers at 60 °C. The hemisphere is used to observe the etching behavior of different crystallographic planes. The present work aims at minimizing the etch rates of non-(100) planes, so that microstructures with rounded concave corners and convex corners can be realized easily. The proposed anisotropic wet etching is used for the fabrication of different kinds of microfluidic channels. Conformal etching in a single step can be realized for arbitrary mask designs targeting 20-25 μm deep microstructures.

In this paper we present a TCAD tool for MEMS, which combines process and layout design and provides links to behavioral modeling tools as well as to specialized modules for the optimized design of single components. There is a large amount of new fabrication technologies available which make the design of highly innovative MEMS and MOEMS possible. The design of such systems not only incorporates the layout of masks but also involves the composition of a flawless process chain. TCAD tools for MEMS available today do mostly not support the design of new fabrication processes together with behavioral simulation and layout design. Therefore, there is a need for a methodical approach to component-design, which leads an engineer from single components to a system ready for fabrication. Based on a conceptual model for the design process the latest version of the modular software environment BICEP³S (Braunschweigs Integrated CAD-Environment for Product Planning Process Simulation) is explained. The concept and data model of building blocks on component level, that act as knowledge containers for fabrication ready functional elements of microsystems, are shown in detail. As the detailed simulation of single process steps is crucial in fabrication oriented design cycles, we present an atomistic etch-simulator as one example for specialized simulation modules of our design environment.

Since porous silicon (PS) has a lower Young's Modulus as compared to silicon, Silicon/Porous Silicon (Si/PS) composite membranes are expected to show higher sensitivity as compared to membranes of silicon alone. In this paper we discuss the fabrication and testing of Si/PS composite membranes where a part of the silicon membrane depth is converted into PS. Composite membranes with Si/ microPS and Si/ macroPS were fabricated with varying porosity and same thickness. The composite membranes with micro PS show higher sensitivity than composite membranes with macro PS. Formation of microporous and macroporous silicon produces stress on the membrane varying with the porosity. The variation in compressive stress on the membrane with porosity for both micro and macro PS has been studied by measuring the deformation of the composite membrane with a surface profiler and the stress is found to be larger for microPS. The compressive stress results in an increase in the offset voltage by more than an order of magnitude for composite membranes with porosity above 50% as compared to one with a single crystalline silicon one. Though the composite membranes exhibit saturation and hysteresis at higher pressures, the response is linear and repeatable at pressures below 1 bar making this a viable option for sensing low pressures.

Femtosecond lasers have been widely used for the micro structuring of transparent materials for a wide range of applications. The local change in refractive index by the irradiation of laser pulse has been exploited for optical applications ranging from optical data storage to the fabrication of waveguides and couplers. In this work, a Ti:Sapphire femtosecond laser (800nm, ~150 fs and 1 kHz) is used for the fabrication of three dimensional (3D) waveguides in thick PMMA substrates. The femtosecond laser microfabrication (FLM) system consists of the laser and three translational (X, Y and Z) stages and one rotational controlled motorized stages. The coordinated motion of these four stages can be used to generate desired three dimensional pattern inside the transparent material due to refractive index modification. This work will present the design of 3D waveguide using commercially available solid modeler, the generation of motion control codes using a customized post processor and the writing of the developed pattern. Also, control of the laser process parameters to obtain desired feature quality by minimizing self-focusing and self-trapping in PMMA is discussed. This FLM system along with the 4-axis machining capability can be effectively used for the fabrication of complex 3D waveguide circuits in a single step process.

Photostructurable glass-ceramics (PSGCs), although not yet widely used, are well suited to many micro-optical and micromechanical applications. Their appeal stems from the combination of the physical properties of glass-ceramics with the excellent three-dimensional shaping control that can be achieved by laser-patterning a transparent photostructurable material. The PSGCs are both mechanically and thermally robust. Exposure with a focused 355-nm pulsed laser beam initiates a cascade of reactions that ends in crystallization of a different phase of the glass-ceramic. The crystal-rich phase etches chemically much faster than the original crystal-free phase. In this experiment, we examined the dependence of the chemical etch rate on the aspect ratios and sizes of structures made from Foturan, a commercially available PSGC. We fabricated several types of test structures in 1-mm-thick Foturan samples. We tested the initial and long-term etch behavior of Foturan etched in 5% HF as a function of the size of the etched structure. An aspect ratio of 100 for a 10-μm-wide trench etched through a 1000-μm-thick sample was achieved.

A dry film photoresist (MX 5020 from DuPont Electronic Technologies) was selected to fabricate microstructures with high sidewall verticality. Sidewall verticality of dry film is very important for better pattern transfer and sharp features. A fractional factorial design (FFD) method was used to identify the significant process variables for sidewall optimization. The most significant factor was determined to be exposure energy, as other factors were not significant in improving sidewall verticality. It was found that the sidewall slope increased with a decrease in exposure energy. The fabricated dry film molds with nearly vertical sidewalls (86°) were used for copper electroplating and sputter deposited Ti lift-off applications. The electroplating process was also optimized using a fractional factorial design. A lower plating current density resulted in a smoother, fine grained deposit compared to the higher current density, and the dry film resist was able to withstand a very acidic (pH ~1) copper sulfate plating solution. Sputtered titanium films with a thickness of 200 nm were also successfully lifted-off using dry film patterning.

The change of resistivity of the epoxy-based nanocomposite was studied in dependence on concentration of dispersed nanoparticles. The SU8 negative-tone photoresist was applied for the polymer matrix and the conductive carbon black powder for the fillings. The largest decrease of resistivity was obtained at 2-3 wt% of fillings whereas at loadings higher that 8 wt% it does not decreases further appreciably. The resistivity of the prepared nanocomposites becomes smaller after the UV-exposure. The applied nanofillings change the viscosity of the material but the spin-coating application still remains reliable and was approved to work well for concentrations of at least up to 3 wt%. The addition of nanofillings up to 2 wt% does not destroy the resolution of photolithography as seen on the standard test pattern with line widths from 2 to 10 μm.