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Overlay (OVL) is a key index in lithography, which will determine product quality, and its measurement is affected by many factors, such as measurement tool, measurement strategy, OVL mark and STI CMP, etc. For some layers used thick Photoresist(PR), OVL results are out of control due to worse PR profile, especially for asymmetric profile which will cause inaccurate mark signal reading, so it is difficult to guarantee to get actual OVL performance. In this paper, we take some of investigations to optimize OVL measurement accuracy of layer with thick PR, and the corresponding mechanism is also analyzed.

A cell culture on a scaffold has the advantages of functionality and easy handling, because the geometry of the cellular tissue is controlled by designing the scaffold. To create complex cellular tissue, scaffolds should be complex two-dimensional (2D) and three-dimensional (3D) structures. However, it is difficult to fabricate a scaffold with a 2D and 3D structure because the shape, size, and fabrication processes of a 2D structure in creating a cell layer, and a 3D structure containing cells, are different. In this research, we propose a micropatterning method for porous materials using the difference of the glass transition temperature between exposed and unexposed areas of a thick-photoresist. Since the proposed method does not require a vacuum, high temperature, or high voltage, it can be used for fabricating various structures with a wide range of scales, regardless of the materials used. Additionally, the patterning area can be fabricated accurately by photolithography. To evaluate the proposed method, a membrane integrated scaffold (MIS) with a 2D porous membrane and 3D porous material was fabricated. The MIS had a porous membrane with a pore size of 4 &mu, m or less, which was impermeable to cells, and a porous material which was capable of containing cells. By seeding HUVECs and HeLa cells on each side of the MIS, the cellular tissue was formed with the designed geometry.

This paper presents a fabrication of extremely thick SU-8 photoresist process in a height range Of $\mathbf{1000}\ \mu \mathbf{m}$ to $\mathbf{2000}\ \mu \mathbf{m}$ high-aspect-ratio microstructures. To differentiate conventional high-aspect-ratio tall structures less than $\mathbf{1000}\ \mu \mathbf{m}$, a new term, microtower, was adopted for the microstructure with a height of $\mathbf{1000}\ \mu \mathbf{m}$ or taller. In fabrication process, to avoid a long softbaking process from the thick photoresist and provide uniform film thickness, an SU-8 dry film was adopted. Ultra-violet (UV) light exposure with an acrylic filter was investigated in terms of transparency of the applicable wavelength spectrum. An array of the $\mathbf{1000}-\mu \mathbf{m}$ tall microtower array was fabricated without the acrylic filter resulting in wavy sidewalls. Whereas an array of $\mathbf{2000}-\mu \mathbf{m}$ tall microtower was fabricated with the acrylic filter resulting straight sidewalls. An array of $\mathbf{1500}-\mu \mathbf{m}$ -long inclined V-pillars was also successfully fabricated by adopting the UV exposure with the acrylic filter, and the fabricated microstructures have potential use as a microfilter in microfluidics. A state-of-art 100-turn toroid inductor was successfully fabricated and electrically characterized resulting an average inductance of 950 nH in the frequency range of 0.1 to 10 MHz. A low-frequency resistance of $\mathbf{5.4}\ \Omega$ at 0.1 MHz and a quality factor of 22 at 60 MHz were measured.

A major breakthrough in UV-LIGA (Lithographie, Galvanoformung and Abformung) started with the use of epoxy-based EPON® SU-8 photoresist in the mid-1990s. Using this photoresist has enabled the fabrication of tall and high aspect ratio structures without the use of a very expensive synchrotron source needed to expose the photoresist layer in X-ray LIGA. SU-8 photoresist appeared to be well-suited for LIGA templates, but also as a permanent material. Based on UV-LIGA and SU-8, Mimotec SA has developed processes to manufacture mold inserts and metallic components for various market fields. From one to three-level parts, from Ni to other materials, from simple to complicated parts with integrated functionalities, UV-LIGA has established itself as a manufacturing technology of importance for prototyping, as well as for mass-fabrication. This paper reviews some of the developments that led to commercial success in this field.

Based on a suitable infrared drying system, experimental considerations of photoresist drying during soft bake have been carried out. A simple mono-parametric model for describing drying kinetics of photo resists, derived from Second Fick?s Law, is presented in this paper. The presented model has been used for curve-fitting on the measurements. The resulting plots showing a good correlation to measurements, especially in the diffusion-dominated drying phases at long drying times. The diffusion coefficients (resulting from curve fits) clearly showing a thermal activated process. Subsequently, experimental considerations of drying of multi-layer systems has been carried out.

Ordered nanoarchitectures have attracted an intense research interest recently because of their promising device applications. They are always fabricated by self-assembling building blocks such as nanowires, nanodots. This kind of bottom up approaches is limited in poor control over height, lateral resolution, aspect ratio and patterning. Here, we break these limits and realize 3D sculpturing of vertical ZnO nanowire arrays (NAs) based on the conventional photolithography approach. These are achieved by immersing nanowire NAs in thick photoresist (PR) layers, which enable the cutting and patterning of ZnO NAs as well as the tailoring of NAs. Our strategy of 3D sculpturing of NAs promisingly paves the way for designing novel NAs-based nanoarchitectures.

Fast marching method is an accurate, extremely fast numerical technique in analyzing and computing moving fronts which can develop sharp corners and change topology. We successfully accomplish this method in two dimensions and the two-dimensional lithography process simulation of SU 8 photoresists has been implemented. The obtained results indicate that the fast marching method can actually accelerate the simulation and be used as an effective method for thick photoresist lithography process simulations.

In this work, the design and fabrication of a low f-number cylindrical microlens array is presented. The lenses were fabricated in thick photo resist of 12 μm thickness, using a contact printer exposure through a mask with a repetitive 6 μm line - 4 μm space pattern. Numerical calculations based on scalar diffraction theory were employed to model the light propagation inside the resist, determining the aerial image as a function of its thickness. Than the resist response characteristics, expressed by its contrast curve, and absorption rate were used to obtain a cross section profile. A good match between numerical and experimental results were found.

This work suggests a simple method to flatten thick layers (similar to 50-200 mu m) of SU-8 photoresist on small substrates (similar to 1 cm). The method sidesteps the edge beads problem and enables photolithography patterns up to the substrates' edges. Moreover, the method can be used even for substrates with large aspect ratios when the spin coating is largely impossible.

Fabrication of tall features using selective electrodeposition is well known process and has several applications in microelectronics packaging. The use of conventional exposure and development processes is limited by the aspect ratio and sizes of the features obtained. This paper describes a novel approach to fabricated tall structures featured in thick photoresist . Tin and copper tall structures were made by selective electrodeposition. Also presented are results from experiments performed to fabricate tall tin and copper pillars with nearly vertical walls on bare dices to form interconnect.

We report a new type of negative-tone photoresist in this paper. The resist is based on a composite of EPON resins 154 and 165 (both from Hexion Specialty Chemicals, Inc., Columbus, OH 43215). These two epoxy-based resins were mixed in an optimal ratio and dissolved in gamma-butyrolactone (GBL) solvent. The mixture was then photosensitized by adding a given amount of triaryl sulfonium salt to obtain a new negative-tone photoresist that can be used in for ultra-high-aspect-ratio microstructure fabrication with UV lithography. Preliminary studies have found that microstructures with heights of more than 1000 μm and feature sizes down to 10 μm (aspect-ratios of more than 100) can be obtained using the new resist film with ultraviolet lithography. The microstructures have excellent sidewall quality. In this paper, both the material properties and lithography properties of this new type of UV resist will be presented. The potential applications of the new resist in microfabrication and MEMS systems are also discussed.

A giant magnetoimpedance (GMI)-based biosensor was developed for detection of Escherichia coli (E. coli) O157: H7. The GMI sensor involving the sensing elements of Cr/Cu/NiFe/Cu/NiFe was fabricated by Micro Electro-Mechanical system (MEMS) technology, including thick photoresist lithography and electroplating. A separate Au film substrate as immunoplatform was used to capture E. coli O157:H7. The monoclonal mouse anti-E. coli antibody was immobilized on Au film substrate surface with a self-assembled layer. The different concentration E. coli O157:H7 (100, 300 and 500 cfu/ml) were combined with Dynabeads-antibody conjugates (DAC) respectively. DAC were prepared by conjugating streptavidin-coupled Dynabeads with biotin-labeled polyclonal mouse anti-E. coli antibodies. The classical sandwich assay was used for detection of E. coli O157:H7 targeted with Dynabeads by using antibody-antigen pair combination of biotin-streptavidin. The fundamental principle for detection of E. coli O157:H7 based on GMI sensor was that Dynabeads were employed as magnetic labels of E. coli O157:H7, and E. coli O157:H7 can be monitored by detecting the fringe field of Dynabeads using magnetic sensing elements. We observed that the GMI ratio were significantly improved due to the presence of E. coli O157:H7 combined with Dynabeads. The GMI ratio increased as the E. coli O157:H7 concentration increased. A lower detectable concentration of 100 cfu/ml was achieved in present work. The GMI-based biosensor provides a new method to rapid and sensitive detection E. coli O157:H7, which has a large potential for bio-application.

Digital Micromirror Device (DMD)-based grayscale lithography is a promising tool for three dimensional (3D) microstructuring of thick-film photoresist since it is a maskless process, provides possibility for the free-form of 3D microstructures, and therefore rapid and cost-effective microfabrication. However, process parameter determination lacks efficient optimization tool, and thus conventional look-up table (indicating the relationship between development depth and exposure dose value under a fixed development time) approach with manual try-and-error adjustment is still gold standard. In this paper, we firstly present a complete “input target-output parameters” single exposure optimization method for 3D microstructuring utilizing DMD-based grayscale lithography. This numerical optimization based on lithography simulation and sensitivity analysis can automatically optimize a combination of three process parameters for target microstructure; exposure dose pattern, a focal position, and development time. Through a series of experiments using a 20 μm thick positive photoresist, validity of the proposed optimization approach has been successfully verified. Secondly, with the purpose of further advancing accuracy and improve the uniformity of precision for the target area, a multiple exposure optimization method is proposed. The simulated results proved that the multiple exposure optimization method is a promising strategy to further improve precision for thicker photoresist structure.

本研究は, UV厚膜レジストによるフォトリソグラフィと電鋳の組み合わせによりマイクロコネクタを作製し, その特性評価を行った。作製したマイクロコネクタは100ピンで, 厚さ50μm, 最小幅15μm, 最大アスペクト比3.3であり, 端子間のピッチは80μmである。特性評価として接触力, 接触抵抗, ヤング率, 許容電流値の測定を行った。ソケット端子の変位量が5μmのときの接触力は3.3mNであった。四探針法により測定した端子間の接触抵抗は50mΩ以下であった。SPM法などにより端子を構成するNi構造体のヤング率を測定したところ180GPaであった。また, 環境試験を実施した結果, 設計したマイクロコネクタはAuめっきを施すことで安定した電気的接触が得られる見通しを得た。

The use of SU-8 high aspect ratio, thick, photoresist as a functional material for MEMS applications is described in this paper. SU-8 processing is developed to implement low-stress SU-8 structures as permanent and functional material incorporated with silicon-on-insulator technologies. Silicon micromachined cantilevers were fabricated with SU-8 structures on the cantilevers as added masses. Separation of material function can be achieved in this way. Silicon provides excellent mechanical properties, while SU-8 is used as extra mass to adjust the mechanical behaviour. The resonance behaviour of the cantilever structure with SU-8 is characterized through measurement, simulation and calculation, and the strength of the SU-8 material for this purpose is evaluated. The results show that SU-8 is well suited as a permanent material in mechanically active MEMS devices, and several applications are suggested. 3D MEMS architectures can also be achieved in this manner.

This research is on the development of a micro variable optics array which employs electrowetting as the working principle. The single pixel of the array has four separated electrodes and each of them is controlled independently giving the device multi-degree of freedom. The separated electrodes are fabricated using a thick photoresist and electroplating. Several formulas showing the relation among the radius of curvature, the prism angle, and electrowetting parameters are provided. The prism angles are measured to be ±30° and compared to the calculated values. The measurement of the radius of curvature is also presented showing that the various radiuses of curvature are achievable from concave to convex.

The high energy retrograde well implants for sub-0.18 microns CMOS are done at a normal or near normal incidence to minimize the shadowing due to the thick photoresist edges. The endstation geometry in a high energy implanter results in an incident angle variation across the wafer, which causes strong spatial variations in the well profile and can negatively impact device performance. We show that the spatial variations can have significant impact on shallow trench isolation (STI), by causing in a deterministic pattern the failure of STI devices on a wafer. These spatial variations are important and need to be taken into consideration for STI design.

Interest in thick photoresist applications is steadily growing. Specialised equipment has been developed to cope with the new challenges to process and pattern extremely thick photoresist layers. A decisive step in the preparation of resist layers is the prebaking. The impact of three different prebaking technologies on the resist performance has been investigated. Resist patterns obtained after oven, hotplate or IR prebaking exhibit equal high quality. Compared to oven and hotplate baking the process length and energy consumption is markedly reduced using IR radiation favouring this variant to be the optimum prebaking process for very thick photoresist layers.

A new low-cost UV LIGA process using photoresists as sacrificial layers has been developed to fabricate micromechanical components and systems. Commonly used photoresists are spun on a substrate and patterned by a mask aligner. Free-standing metal structures are built by patterning a second layer of thick photoresist and electroplating upon the photoresist sacrificial layer. Compared with all the existing sacrificial layer techniques, photoresists are easy to coat, easy to dissolve and fewer process steps are involved. The process is compatible to most of the materials and processes used in existing microfabrication technology. The precision issue of UV LIGA technique is also discussed.

Advanced mask aligner lithography (AMALITH) is a holistic approach to improve shadow printing (contact and proximity lithography) in mask aligners. AMALITH is based on two tools, the MO Exposure Optics®, a new illumination system allow shaping the angular spectrum of the illumination light, and LAB, a software tool for full 3D simulation of the shadow printing process. MO Exposure Optics® is provided by SUSS MicroTec AG ( http://www.suss.com ), as an upgrade for all current and older mask aligner models. MO Exposure Optics® decouples the illumination from lamp misplacement (self-calibrated light source), improves the light uniformity, provides telecentric illumination and enables customized illumination in mask aligners. LAB is a software tool provided by GenISys GmbH ( http://www.genisys-gmbh.com ), and allows simulating the complete chain from illumination, mask pattern, photoresist and resist processing. The combination of both tools allows optimizing mask aligner lithography beyond today's limits.

Three-dimensional (3D) UV microforming delivers promising results for advanced surface micromachining. This low-cost technology, a combination of UV patterning of very thick photoresist layers and moulding of the resulting patterns by electrodeposition, opens a wide range of applications. It allows the use of materials with interesting properties that could not be provided by standard processes. Furthermore, this method can be carried out directly on pre-processed chips. The practical application of the technology is demonstrated by planar and 3D microcoils.

Current photospeed testing methods are based on dose to clear (E 0 ) or resist contrast (γ 10 ). Either method is inadequate for controlling sensitivity to within ±1.5%. We investigated various methods for improving these photospeed tests. Ranked in order of decreasing importance are: (i) controlling standing waves (reflectivity); (ii) choice of developer, (iii) develop time; and (iv) exposure pattern. Reflectiuty can be controlled by careful attention to resist thickness, addition of a bottom antireflective layer, addition of a low refractive index layer (AquaTar), or by using a thick photoresist. Moreover, we can utilize the whole dissolution curve rather than the one-point determination of the E 0 test

International audience; This work deals with recent advances in the microfabrication process technology for medium to high-aspect ratiostructures fabricated by UV photolithography using different kinds of photoresists. The resulting structures were used asmolds and will be transformed into metal structures by electroplating. Two types of photoresists are compared: epoxybased(negative) SU-8 and acrylate-based (negative) Intervia BPN. This work was prompted by the need to find analternative to SU-8 photoresist which is difficult to process and remove after electroplating. The results presented in thispaper open up new possibilities for low-cost processes using electroplating in MEMS applications.

International audience; The roughness of etched SiC surfaces must be minimized to obtain surfaces with a smooth aspect, avoiding micromasking artifacts originating from re-deposited particles during the etching process. Four varieties of masks, Al, Ni, Si and C, were deposited on the SiC surface by photolithographic process. The C structures were formed by annealing conversion of patterned thick photoresist. On these surfaces, dry etching was performed with an SF6/O2 plasma produced in a Reactive-Ion-Etching (RIE) reactor. Although a better aspect of the surface is obtained with Ni in comparison with Al mask, micromasking could also occur even with Ni if the mask design was not enough spaced out. With C and Si masks, which produce fluorides species with negative boiling temperature, smooth etched surface was obtained without micromasking, even for tight masks covering up to 90% of the SiC surface.

A new self-aligned offset staggered polysilicon thin-film transistor (poly-Si TFT) has been proposed and demonstrated to have a suppressed leakage current. For the self-aligned offset structure, planarization with thick photoresist and etchback of photoresist are successfully utilized. The offset length can be easily controlled by the thickness of the gate material without photolithographic limitation. In the self-aligned offset polysilicon TFT's, the leakage current decreases with an increasing offset length.