A comparative study of different thick photoresists for MEMS applications

This work reports on recent advances in microfabrication process technology for medium to high-aspect ratio structures realised by UV photolithography using different kinds of photoresists. The resulting structures were used as moulds and will be translated into metallic structures by electroplating. We used four types of photoresists: SPR 220-7 novalak based (positive), SU8 epoxy based (negative), Ordyl P-50100 acrylate based (negative) dry film photoresist, and Diaplate 132 acrylate based wet photoresist (negative). The motivation for this work was to find an alternative to SU-8 photoresist, which is difficult to process and remove after electroplating. Depending on the application, we found that Ordyl P-50100 dry film photoresist is the best alternative to SU8 for realization of approximately 100 μ m deep moulds for electroplating in acidic electroplating solution. SPR 220-7 is a good alternative to SU8 for fabrication of 50 μ m deep moulds and electroplating in alkaline solutions. The results presented in this paper will open up new possibilities for low-cost processes using electroplating for MEMS applications.     

Microelectromechanical systems vibration powered electromagnetic generator for wireless sensor applications

This paper presents a silicon microgenerator, fabricated using standard silicon micromachining techniques, which converts external ambient vibrations into electrical energy. Power is generated by an electromagnetic transduction mechanism with static magnets positioned on either side of a moving coil, which is located on a silicon structure designed to resonate laterally in the plane of the chip. The volume of this device is approximately 100 mm³. ANSYS finite element analysis (FEA) has been used to determine the optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansoft’s Maxwell 3D software have been performed to determine the voltage generated from a single beam generator design. The predicted voltage levels of 0.7–4.15 V can be generated for a two-pole arrangement by tuning the damping factor to achieve maximum displacement for a given input excitation. Experimental results from the microgenerator demonstrate a maximum power output of 104 nW for 0.4g (g=9.81 m s⁻¹) input acceleration at 1.615 kHz. Other frequencies can be achieved by employing different geometries or materials.

     

An LCOS IC layout verification method that uses a computational model for lithography manufacturing

Abstract— An advanced approach to LCOS IC layout verification is presented. It is based on incorporating the results of optical lithography computational models into the verification process. The first section describes an algorithm for the numerical modeling of optical lithography that uses a source integration method for computation of an aerial image. The second section dwells on an application of this algorithm for layout physical verification. A proposed physical verification method uses modeled contours of the manufactured elements to check whether a given layout will be manufacturable. The proposed verification method also considers deviations of manufactured contours from their modeled shapes due to variation of manufacturing parameters to further improve verification quality. At the same time, the method is conservative in terms of the use of a time‐consuming lithographical modeling.     

Microelectromechanical systems vibration powered electromagnetic generator for wireless sensor applications

This paper presents a silicon microgenerator, fabricated using standard silicon micromachining techniques, which converts external ambient vibrations into electrical energy. Power is generated by an electromagnetic transduction mechanism with static magnets positioned on either side of a moving coil, which is located on a silicon structure designed to resonate laterally in the plane of the chip. The volume of this device is approximately 100 mm³. ANSYS finite element analysis (FEA) has been used to determine the optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansoft’s Maxwell 3D software have been performed to determine the voltage generated from a single beam generator design. The predicted voltage levels of 0.7–4.15 V can be generated for a two-pole arrangement by tuning the damping factor to achieve maximum displacement for a given input excitation. Experimental results from the microgenerator demonstrate a maximum power output of 104 nW for 0.4g (g=9.81 m s^?1) input acceleration at 1.615 kHz. Other frequencies can be achieved by employing different geometries or materials.     

Scalable Silicon Nanostructuring for Thermoelectric Applications

The current limitations of commercially available thermoelectric (TE) generators include their incompatibility with human body applications due to the toxicity of commonly used alloys and possible future shortage of raw materials (Bi-Sb-Te and Se). In this respect, exploiting silicon as an environmentally friendly candidate for thermoelectric applications is a promising alternative since it is an abundant, ecofriendly semiconductor for which there already exists an infrastructure for low-cost and high-yield processing. Contrary to the existing approaches, where n/p-legs were either heavily doped to an optimal carrier concentration of 10¹⁹ cm^?3 or morphologically modified by increasing their roughness, in this work improved thermoelectric performance was achieved in smooth silicon nanostructures with low doping concentration (1.5 × 10¹⁵ cm^?3). Scalable, highly reproducible e-beam lithographies, which are compatible with nanoimprint and followed by deep reactive-ion etching (DRIE), were employed to produce arrays of regularly spaced nanopillars of 400 nm height with diameters varying from 140 nm to 300 nm. A potential Seebeck microprobe (PSM) was used to measure the Seebeck coefficients of such nanostructures. This resulted in values ranging from ?75 μV/K to ?120 μV/K for n-type and 100 μV/K to 140 μV/K for p-type, which are significant improvements over previously reported data.