David Karlén

MEMS Sensor for In Situ TEM Atomic Force Microscopy

Here, we present a MEMS atomic force microscope sensor for use inside a transmission electron microscope (TEM). This enables direct in situ TEM force measurements in the nanonewton range and thus mechanical characterization of nanosized structures. The main design challenges of the system and sensor are to reach a high sensitivity and to make a compact design that allows the sensor to be fitted in the narrow dimensions of the pole gap inside the TEM. In order to miniaturize the sensing device, an integrated detection with piezoresistive elements arranged in a full Wheatstone bridge was used. Fabrication of the sensor was done using standard micromachining techniques, such as ion implantation, oxide growth and deep reactive ion etch. We also present in situ TEM force measurements on nanotubes, which demonstrate the ability to measure spring constants of nanoscale systems.

A Micromachined 94 GHz Dielectric Resonator Antenna for Focal Plane Array Applications

In this paper a new concept of integrating micromachined high-resistivity (HR) silicon dielectric resonator antennas (DRAs) compatible with a millimeter wave multichip module deposited (MCM-D) process based on multiple layers of benzocyclobuthene (BCB) is presented. The HR Si wafer is used not only as a carrier substrate for the BCB but also for manufacturing of the integrated antenna elements. A 4times8 focal plane array (FPA) was designed for use in a 94 GHz imaging radar system. Each channel uses a small 2times2 DRA subarray as feed element. By using the presented antenna a higher impedance bandwidth and radiation efficiency can be attained compared to the use of microstrip antennas. An improved isolation between the antennas and the feed lines/active circuits is also realized.

Microreplication in a silicon processing compatible polymer material

We present a novel fabrication process for the integration of polymer micro-optical elements on silicon. The process relies on a reverse order protocol based on embossing in an amorphous fluorocarbon polymer, Cytoptrade

MEMS sensor for in situ TEM Atomic Force Microscopy

Here we present a MEMS atomic force microscope (AFM) sensor for use inside a transmission electron microscope (TEM). This enables direct in situ TEM force measurements in the nN range. The main design challenges of the sensor are a high sensitivity and the narrow dimensions of the pole gap inside the TEM. Fabrication of the sensor was done using standard micromachining techniques, such as ion implantation, oxide growth and deep reactive ion etch. We present in situ TEM force measurements on nanotubes, which demonstrates the ability to measure spring constants of nanoscale systems.

Refractive lenses in silicon micromachining by reflow of amorphous fluorocarbon polymer

A new fabrication process for refractive microlenses making use of reflow of an amorphous fluorocarbon polymer, Cytop?, is described. This process is suitable for MEMS structures that require the integration of high-quality lenses producing MOEMS. The reflowed polymer has excellent optical properties and can be used throughout the visible and near-infrared wavelength range. The reflow step also results in curing of the polymer into an extremely stable and chemically resistant material. This enables MOEMS fabrication by a reverse-order protocol, i.e. the structuring of the reflow lens on the wafer precedes the silicon micromachining. In the first study, lenses with a diameter of 150 ?m were fabricated. An optical analysis based on the sampled height profile revealed that the lenses worked as virtually perfect lenses, with a nominal focal length equal to ~1550 ?m, out to more than 50% of their diameter, while in the periphery the lens action was stronger, which leads to slightly pronounced side lobes in the shape of the focal spot. In the second parametric study, lenses with nominal diameters in the range of 25?150 ?m were fabricated. In this study, the thickness of the Cytop layer was larger which resulted in lenses with a smaller radius of curvature of the surface and hence an increased focusing power. In particular, the lenses with 25?50 ?m nominal diameters were found to have actual diameters somewhat larger than their nominal and a perfect lens shape all over their surface, yielding high-quality focusing lenses with f-numbers (focal length divided by useful diameter) as small as ~1.9.

Replication of continuous-profiled micro-optical elements for silicon integration

A novel scheme for the integration of diffractive optical elements onto silicon is presented. The processing is made in reverse order, meaning that the process of structuring the optical elements on the wafer precedes the silicon microstructuring. The first processing step on the wafer is the hot embossing of the optical microstructures into an amorphous fluorocarbon polymer spin coated on the wafer. The cured polymer forms a highly stable material with excellent optical properties. The remaining silicon processing is thus performed with the diffractive optical elements already in place. Two different diffractive structures were used in the development of the method-a (Fresnel) lens with a rather low f-number and a diffractive element producing a fan-out of a large number of paraxial beams.

Boron impurity at the Si/SiO2 interface in SOI wafers and consequences for piezoresistive MEMS devices

Boron impurity at the Si/SiO_{2} interface in SOI wafers and consequences for piezoresistive MEMS devices