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Mask aligners are lithographic tools used to transfer a pattern of microstructures by shadow printing lithography onto a planar wafer. Contact lithography allows us to print large mask fields with sub-micron resolution, but requires frequent mask cleaning. Thus, contact lithography is used for small series of wafer production. Proximity lithography, where the mask is located at a distance of typically 30–100 μm above the wafer, provides a resolution of approximately 3–5 μm, limited by diffraction effects. Proximity lithography in mask aligners is a very cost-efficient method widely used in semiconductor, packaging and MEMS manufacturing industry for high-volume production. Micro-optics plays a key role in improving the performance of shadow printing lithography in mask aligners. Refractive or diffractive micro-optics allows us to efficiently collect the light from the light source and to precisely shape the illumination light (customized illumination). Optical proximity correction and phase shift mask technology allow us to influence the diffraction effects in the aerial image and to enhance resolution and critical dimension. The paper describes the status and future trends of shadow printing lithography in mask aligners and the decisive role of micro-optics as key enabling technology.

A process for the deposition of a solid layer onto a liquid is presented. The polymer poly-di-chloro-para-xylylene, also known as Parylene C, was grown on low vapour pressure liquids using the conventional low pressure chemical vapour deposition process. A reactor was built and a process developed to enable the deposition of Parylene C at atmospheric pressure over high vapour pressure liquids. It was used to deposit Parylene C over water among others. In all cases Parylene C encapsulated the liquid without influencing its initial shape. The results presented here show also that the Parylene C properties are not affected by its growth on liquid templates and the roughness of the Parylene C surface in contact with the liquid during the deposition is extremely low.

An experimental thermal characterization method is developed for high thermal conductivity thin films. The method utilizes Ta/Pt resistors on microfabricated free-standing thin film structures both for heating and temperature monitoring at different positions on the structures. The steady-state temperature at the heater and the sensor positions are monitored as a function of the power dissipated by the heater under vacuum environment, and the thermal conductivity is estimated by comparing these results to FEA and/or analytical models. The developed method is used to characterize the thermal conductivity of various different CVD diamond films of different grain sizes and films thicknesses. The measured thermal conductivity values range from 15 W/m·K to 300 W/m·K, which are at least one order of magnitude lower than that of natural diamond. It is also shown that the thermal conductivity of such films in the in-plane direction increases with increasing grain size and film.

In this paper, a novel 1×4 optical switch has been developed based on the DRIE vertical mirror technology. Three microactuated vertical silicon mirrors and five tapered/lensed fibers were employed to perform the 1×4 switch function. The comb actuators drive the mirrors linearly into the optical path due to the electrostatic force. The tilted mirror with an angle of 22.5° made the layout of the mirrors and optic fibers more compact. Finite element method (FEM) modeling on the linear comb actuator was implemented to verify the design. Deep reactive ion etching (DRIE) process was employed to fabricate the mirrors, combs and U-grooves on a SOI wafer. A satisfactory yield (up to 70%) was achieved during the microfabrication due to the compactness of the single photomask process. The prototype of the optical switch was packaged and systematically characterized in terms of bonding properties, optical performance including insertion loss, return loss, cross talk, and switch time. The design and microfabrication has been demonstrated to be successful. The packaging technique can be utilized in the similar category of optical MEMS devices. The optical performance of our switch exhibits the great promise in the application of optical networks.

A new method for realizing three-dimensional structures based on the standard silicon-on-insulator microelectromechanical systems is developed using vertically buckled bridges as structural elements. The vertical displacement, profile of the bridge, and obtainable accuracy of the displacement are examined. Using the lateral dimension control of the bridge and the supporting beams, the vertical positioning is realized based on the planer photolithography. As a demonstration, a vertical comb drive actuator is prepared and its performance is examined.

A large-aperture and large-angle MEMS-based 2D pointing mirror is presented. The device is electromagnetically actuated by a moving-magnet/stationary-coil pair and potentially suited for high power laser beam shaping and beam pointing applications, such as LIDAR. The 4×4 mm2 mirror, the radially symmetric compliant membrane, and the off-the-shelf permanent magnet are manually assembled, with the planar coil kept at a well-defined vertical distance from the permanent magnet by simple alignment pins. The mirror and the compliant membrane structures are separately microfabricated on bulk silicon and SOI wafers, respectively. The hybrid integration of microfabricated and off-the-shelf components enable low-risk/high-yield fabrication, while limiting the throughput. The device features minimum inter-axis cross coupling and good linearity and is highly immune to alignment and assembly imperfections, thanks to the robust actuation principle. All the components including the bi-axial electromagnetic actuator provide a device footprint as small as the top mirror, allowing the design to be used in compact and high-fill-factor mirror arrays. With a drive coil of 400 mA and 5.12 W drive power, the total uniaxial dc rotation exceeds ±16° (optical) for both axes with good decoupling. At maximum measured angle (biaxial 10° (mechanical)), a position stability better than 0.05° over 7 h, and a position repeatability of 0.04° over 5000 switching cycles is reported. Thermally, the simulated mirror temperature increases to 64 K above the heat sink temperature with a thermal in-flux of 1 kW m−2, under absolute vacuum.