Who deserves credit for the work reported in a scientific paper? That is the basic question of science authorship since, unlike authorship credit in the world of creative writing, what matters most for scientific papers are the ideas rather than the words. On the surface, it would seem that deciding who belongs in the list of authors would not be a difficult task. But the affairs of humans are rarely straightforward, and authorship controversies are not uncommon in the world of science and engineering.

We describe the development of novel suspension bridge-type microthermoelectric generators (μ -TEGs) having 64,000 to 147,000 serial-connected thermocouples in a 1-centimeter-square chip area using surface micromachining techniques. Each microthermocouple is constructed by a pair of n/p bridge-type polysilicon thin-film thermolegs and a pair of cold- and hot-side Cr/Au metal planes. Under a controlled fixed temperature difference between the cold/hot sides, the open-circuit voltage and the output power of the proposed μ -TEGs are simulated by commercial software (ANSYS). The influences of thermocouple thermo-leg dimensions and number of thermocouples on the thermoelectric characteristics of presented μ -TEGs are investigated. The implemented suspension bridge-type thermopile has a 2.5-μm-height air-gap separation from substrate and its fabrication yield is higher than 75% in the laboratory environment. The measured maximum temperature difference between the cold/hot sides of the proposed μ -TEGs is about 1.29°C, a maximum open-circuit voltage of 4.64  V/cm 2 and output power of 0.65  μW/cm 2 can be obtained.

A microelectromechanical system (MEMS) device might function perfectly well in the controlled environment in which it has been created. However, the device can be a real viable product only after it has been fabricated with proven performance in a package. As such, the assembly yield of a MEMS package is often a challenging target to meet. The design and fabrication of a free-floating membrane on a flexible substrate to enable easy and cost-effective packaging of MEMS devices is examined. Since standard MEMS fabrication processes are designed for rigid substrates, several process modifications were required to handle flexible substrates. The adaptation of each fabrication process has been documented. Furthermore, detailed information regarding the selection of compatible materials, as well as incompatibilities that were encountered, has been presented to aid future researchers in developing processes for flexible substrates.

The development of a novel automated microassembly mechanism based on on-chip actuators is described. The assembly mechanism utilizes repulsive-force actuators to flip surface-micromachined two-dimensional structures out-of-plane and assemble them in a vertical position. The assembly mechanism is suitable for wafer-level multidevice batch assembly without external interference. Prototypes were fabricated using the PolyMUMPs surface micromachining technology, then tested. The strength of the assembled structures in terms of withstanding external acceleration was calculated and experimentally measured. The measured results showed the assembly strength of 7 g for prototype 1 and 8 to 11 g for prototype 2.

A library search is a widely used method for the reconstruction of diffraction structures in optical scatterometry. In a library search, if the actual geometrical model of a measured signature is different from the model used in the establishment of a library, the search result will be meaningless. Therefore, the identification of the geometrical profile for a measured signature is critical. In addition, fast searching of the library is essential to find a best-matched signature even though the library may have huge amounts of data. The authors propose a support vector machine (SVM)-based method to deal with these issues. First, an SVM classifier is trained to identify the geometrical profile of a diffraction structure from its measured signature, and then another set of several SVM classifiers are trained to map the measured signature into a sublibrary to accelerate the search process. Simulations and experiments have demonstrated that the SVM classifier can identify the geometrical profile of one-dimensional trapezoidal gratings accurately, and the SVM-based library search strategy can achieve a fast and robust extraction of parameters for diffraction structures.

We study the effects of noise in scanning electron microscope (SEM) images on the size and roughness of contact holes when they are measured using top-down SEM images. The applied methodology is based on the generation of synthesized top-down SEM images, including several model contact edges with controlled roughness, critical dimension (CD) uniformity, and noise. The sources of image noise can be the shot noise of SEM electron beams and microscope electronics. The results show that noise reduces CD and correlation length while it increases the rms value of contact edge roughness (CER). CD variation is increased with noise in images with smooth and identical contacts, whereas it remains almost unaltered in images including rough contacts with CD nonuniformity. Furthermore, we find that the application of a noise-smoothing filter before image analysis rectifies the values of CD (at small filter parameter) and of rms and correlation length (at larger filter parameters), whereas it leads to marginally larger deviations from the true values of CD variation. Quantitative assessment of the model predictions reveals that the noise-induced variations of CD and CER values are less important compared with those caused by process stochasticity and material inhomogeneities.

We present a simple microassembly technology that easily realizes angular vertical combs for a microoptoelectromechanical systems scanner. The scanner is composed of a device section with comb electrodes and a tilting section with four tapered pillars. During the microassembly process, two tilting pillars push down the levers so that the comb electrodes connected with the micromirror are tilted; the other two alignment pillars fit into the alignment holes of the device section, which is fabricated via a deep reactive ion etching process of a silicon-on-insulator wafer. The tilting section is fabricated through a series of anisotropic wet etching of a (100) silicon wafer and patterning processes of SU-8, which is robust enough to ensure repeatability of the initial tilted angles of the movable comb electrodes. The pull-in investigation function is analyzed through a numerical estimation to obtain a large scan angle with stable behavior. The fabricated microscanner shows an optical scan angle of up to 4.23 deg at 90 V in the static mode and stable actuation of up to 11.3 deg at a resonant frequency of 2.87 kHz. The roughness of the mirror surface is less than 10 nm, which will have a negligible effect on imaging quality. The initial tilted angles in the microassembly process showed high repeatability within 10% error.

Characterization of defects and their sources is essential for developing mitigation solutions to support the production of defect-free extreme ultraviolet (EUV) mask blanks. The characterization of sub-100-nm defects pose challenges to the conventional metrology techniques, such as atomic force microscopy and scanning electron microscopy, limiting mitigation of nanoscale defects. SEMATECH’s Mask Blank Development Center houses advanced metrology capabilities that include transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) to address these shortcomings. Scanning TEM was used to study the disruption of the Mo/Si multilayer of phase defects and to perform elemental analysis with energy dispersive x-ray spectroscopy that has supported projects including substrate smoothing activities, deposition simulation development, and defect printability studies. The Auger instrument was used to create elemental maps for defect identification and to characterize the ion beam deposition tool. Using advanced metrology, mitigation of small defects is being realized, yielding mask blanks with defect counts as low as eight defects at 50-nm sensitivity (Lasertec M7360 SiO₂ sphere equivalent) measured over the quality area of 132×132 mm² . The issues with the metrology of increasingly small EUV mask blank defects will be outlined, and comprehensive defect characterization results using TEM and AES will be presented.

An aerial image model is used to study the effects of spherical aberration applied in the lens pupil domain of a lithography projection scanner. These effects include the illumination dependency of focus exposure matrix tilt and the linear relationship between primary and higher order spherical coefficients on best focus (BF). Experimental data trends of BF through pitch and orientation have been replicated by an analytical expression. This computationally efficient formulation has the capability to provide corrective spherical aberration coefficients, which decrease the pitch-dependent BF and increase process latitude.

Graphene, one of the recently discovered carbon nanostructures, has shown good piezoresistive properties. One of the most important areas of research for graphene sheets, in terms of basic science and application in strain or stress sensors, is the measurement of gauge factors. The gauge factors of various layers of graphene sheets are measured based on the equivalent stress beam. The measurement is carried out using a beam-bending method to detect the change in resistance of graphene sheets in different bending states. The gauge factor ranges from 10 to 15, depending on the number of layers in the graphene sheet. These results reveal the piezoresistance effect of single- and multi-layer graphene sheets, which will be of benefit in the fabrication of microsensors. The resistance of graphene sheets decreases as temperature increases from 20°C to 60°C, and the gauge factor is not very sensitive to changes in environmental temperature.

We propose an electron beam lithography system that would allow for pattern transfer from a magnetic reticle to a wafer. The reticle consists of a patterned magnetic media where magnetization of a nanomagnet stores a value of a pixel. Information stored on this media is transferred as a pattern onto the electron-resist via spin-polarized electrons photo-generated from the reticle and spin-filtered along the way to the wafer to generate contrast. It is speculated that such a system offers significantly higher throughput than a multielectron-beam lithography system and may outpace in flexibility, cost and throughput extreme ultra-violet-lithography systems that are currently being developed, while at least matching the resolution of both lithography systems.

Large field, ultra-high numerical aperture (NA) lithography is desired in semiconductor manufacturing. We report progress in developing a scanning evanescent wave lithography (s-EWL) imaging head with a two-stage gap control system including a DC noise canceling air bearing, which houses an AC noise-canceling piezoelectric actuator. Various design aspects of the system, including gap detection, prism design, optical alignment, software integration, feedback actuation, and a scanning scheme have been developed to ensure sub-100-nm gap control. Experimental results have shown successful gap gauging with a gap noise root-mean-square (RMS) of 1.38 nm in static gap control, and 4.64 nm in linear scanning gap control. Integrating the prototype imaging head into a two-beam interferometer platform has demonstrated dynamic stepping imaging using fused silica and sapphire prisms, with potential NA values up to 1.85 (26-nm half-pitch). These results achieved with s-EWL provide a possible route to extend optical lithography to 16-nm generations and beyond when combined with double patterning techniques.

Metallic wafer bonding is becoming a key enabling technology in microelectromechanical systems packaging and heterogeneous integration. We realize the bonding of silicon (Si) wafers coated with aluminum (Al) film with thin tin (Sn) film as the intermediate layer. The bonding pressure is 0.25 MPa. The bonding is achieved at temperatures as low as 280°C after a short bonding time of 3 min. The average bonding strength is 9.9 MPa. The minimum variation of bonding layer thickness is about 0.2 μm within a large area. A fracture surface study and a cross-section analysis are conducted and the bond mechanism is investigated. It is found that the fracture mainly occurs at Al/Sn interface during the shear test. Two bonding conditions are compared and the results show that applying bonding pressure before heating is important to achieve a uniform bonding layer.

A new methodology for inspection of through silicon via (TSV) process wafers is developed by utilizing an optical diffraction signal from the wafers. The optical system uses telecentric illumination and has a two-dimensional sensor for capturing the diffracted light from TSV arrays. The diffraction signal modulates the intensity of the wafer image. The optical configuration is optimized for TSV array inspection. The diffraction signal is sensitive to via-shape variations, and an area of deviation from a nominal via is analyzed using the signal. Using test wafers with deep via patterns on silicon wafers, the performance is evaluated and the sensitivities for various pattern profile changes are confirmed. This new methodology is available for high-volume manufacturing of future TSV three-dimensional complementary metal oxide semiconductor devices.

The move to low-k1 lithography makes it increasingly difficult to print feature sizes that are a small fraction of the wavelength of light. With further delay in the delivery of extreme ultraviolet lithography, these difficulties will motivate the research community to explore increasingly broad solutions. We propose that there is significant research potential in studying the essential premise of the design/manufacturing handoff paradigm. Today this premise revolves around design rules that define what implementations are legal, and raw shapes, which define design intent, and are treated as a fixed requirement for lithography. In reality, layout features may vary within certain tolerances without violating any design constraints. The knowledge of such tolerances can help improve the manufacturability of layout features while still meeting design requirements. We propose a methodology to convert electrical slack in a design to shape slack or tolerances on individual layout shapes. We show how this can be done for two important implementation fabrics: (a) cell-library-based digital logic and (b) static random access memory. We further develop a tolerance-driven optical proximity correction algorithm that utilizes this shape slack information during mask preparation to ensure that all features prints within their shape slacks in presence of lithographic process variations. Experiments on 45 nm silicon on insulator cells using accurate process models show that this approach reduces postlithography delay errors by 50%, and layout hotspots by 47% compared to conventional methods.

This paper analyzes the optical propagation and refraction phenomena in various complementary metal–oxide–semiconductor (CMOS) structures at 750 nm wavelength. Operation at these wavelengths offers the potential realizations of small microphotonic systems and micro-opto-electro-mechanical systems (MOEMS) in CMOS integrated circuitry, since Si-based optical sources, waveguides, and silicon (Si) detectors can all be integrated on a single chip. It could also increase the optical coupling efficiencies to external optical fibers. With the help of Monte Carlo and RSoft BeamPROP simulations, we demonstrate achievements with regard to optimizing vertical emission, focusing, refraction, splitting and wave guiding in 0.35 to 1.2 μm CMOS technology at 750 nm wavelength. The material properties, refractive indices, and thicknesses of various CMOS over-layers were incorporated in the simulations and analyses. The analyses show that both Si nitride and Si oxi-nitride offer good viability for developing such waveguides. Effective single-mode wave-guiding with calculated loss characteristics of 0.65  dB⋅cm ⁻¹ , with modal dispersion characteristics of less than 0.2  ps⋅cm ⁻¹ and with a bandwidth-length product of higher than 100 GHz-cm seems possible. A first iteration realization of an optical link is demonstrated, utilizing specially designed avalanche-based Si-LEDs and a specially designed first iteration CMOS waveguide. Potential applications of avalanche-based Si LEDs into microphotonic systems and MOEMS are furthermore proposed and highlighted.

This paper reports on the thermomechanical modeling and characterization of a micro-opto-electro-mechanical systems deformable mirror (DM). This unimorph DM offers a low-temperature cofired ceramic substrate with screen-printed piezoceramic actuators on its rear surface and a machined copper layer on its front surface. We present the DM setup, thermomechanical modeling, and hybrid fabrication. The setup of the DM is transferred into a thermomechanical model in ANSYS Multiphysics. The thermomechanical modeling of the DM evaluates and optimizes the mount material and the copper-layer thickness for the loading cases: homogeneous thermal loading and laser-loading of the mirror. Subsequently, the developed and theoretically optimized DM setup is experimentally validated. The homogeneous loading of the optimized design results in a membrane deformation with a rate of −0.2  μm K ⁻¹ , whereas the laser loading causes an opposed change with a rate of −0.2  μm W ⁻¹ . Therefore, the proposed mirror design is suitable to precompensate laser-generated mirror deformations by homogeneous thermal loading (heating). We experimentally show that a 35-K preheating of the mirror assembly compensates for an absorbed laser power of 1.25 W. Therefore, the novel compensation regime “compound loading” for the suppression of laser-induced deformations is developed and proven.

Conventional flexural plate-wave (FPW) transducers have limited applications in biomedical sensing due to their disadvantages such as high insertion loss and low quality factor. To overcome these shortcomings, we propose a FPW transducer on a low phase velocity insulator membrane (5-μm-thick SiO₂ ) with a novel groove-type reflective grating structure design. Additionally, a cystamine self-assembly monolayer and a glutaraldehyde cross-linking layer are implemented on the backside of the FPW device to immobilize alpha-fetoprotein (AFP) antibody. A FPW-based AFP biosensor with low detection limit (5  ng/mL ) can be achieved and used to measure the extreme low concentration of AFP antigen in human serum for early detection of hepatocellular carcinoma. The proposed FPW-based AFP biosensor also demonstrates a very high quality factor (206), low insertion loss (−40.854  dB ), low operating frequency (6.388 MHz), and high sensing linearity (90.7%).

Scatterometry is one of the most useful metrology methods for the characterization and control of critical dimensions and the detailed feature shape of periodic structures found in the microelectronics fabrication processes. Spectroscopic ellipsometry (SE) and normal incidence reflectometry (NI)-based scatterometry are widely used optical methodologies for metrology of these structures. Evolution of improved optical hardware and faster computing capabilities led to the development of Mueller matrix (MM)-based scatterometry (MMS). Unlike SE and NI, MM data provides complete information about the optical reflection and transmission of polarized light interacting with a sample. This gives MMS an advantage over traditional SE scatterometry due to the ability to characterize samples that have anisotropic optical properties and depolarize light. In this paper, we present the study of full MM (16-element) scatterometry over a wide spectral range from 245 to 1700 nm on a series of one-dimensional, two-dimensional symmetric, and asymmetric grating structures. A series of laterally complex nanoscale structures were designed and fabricated using a state-of-the-art e-beam patterning. Spectroscopic MM and SE data were collected using a dual rotating compensator ellipsometer. Commercial modeling software based on the rigorous coupled-wave approximation was used to precisely calculate the critical dimensions. Results from MMS were compared with scanning electron microscopy.

A novel silicon groove reflective grating structure (RGS) to reduce effectively the insertion loss of a high C-axis (002) thin-film zinc oxide (ZnO) surface acoustic wave (SAW) device is proposed. The insertion loss (S ₂₁ parameter) of three types of SAW devices was investigated and compared; one type had no RGS design, and the other two types had either a conventional metal electrode RGS or a novel etched silicon groove RGS. The wave propagation modes, the harmonic response, and the displacement amplitude profile of the proposed SAW devices were simulated by finite element analysis software (ANSYS). The implemented basic SAW device consists of a sputter-deposited high-quality ZnO thin film on the surface of a Si/SiO ₂ /Si ₃N₄ /Cr/Au substrate. The insertion loss of the proposed SAW device with silicon groove RGS can be reduced to −19.49  dB , which is much smaller than the insertion losses of the SAW devices with a metal electrode-type RGS (−33.15  dB ) and without an RGS (−47.9  dB ). The resonant frequencies of the SAW devices studied (47.37 to 48.05 MHz) are in close agreement with the simulated results (46.8 to 47.55 MHz).