We present experimental results on dry friction, which are consistent with the hypothesis that the stick-slip mechanism for energy release is described by self-organized criticality. The data, obtained with an Atomic Force Microscope set to measure lateral forces– examines the variation of the friction force as a function of time – or sliding distance. The materials studied were nominally flat surfaces of mica, quartz, silica and steel. An analysis of the data shows that the probability distribution of slip sizes follows a power law. Our data strongly supports the existence of self-organized criticality for nano-stick-slip in dry sliding friction.

The broad-spectrum sensitivity of cell based biosensors offers the capability for detecting known and unknown chemical/biological agents. One cellular parameter that is often measured is the extracellular potential of electrically active cells. Membrane excitability in osteoblasts plays a key role in modulating the electrical activity in the presence of chemical agents. However, the complexity of this signal makes interpretation of the cellular response to a chemical agent difficult to interpret. By analyzing shifts in the signal's power spectrum, it is possible to determine a frequency spectrum also known as Signature Pattern Vectors (SPV) specific to a chemical. We used a 5x5 multiple microelectrode array system to spatially position osteoblast cells, by using a gradient AC field. Fast Fourier Transformation (FFT) analyses were used to extract information pertaining to the frequency of firing from the extracellular potential.

Hot embossing has been widely accepted as an alternative to photolithography in generating patterns on polymer substrates. The optimization of embossing process should be accomplished based on polymer surface properties. Therefore, in this paper, polymers with different surface characteristic were selected and the surface properties of each polymers such as surface energy and adhesion force were investigated by contact angle and AFM. Based on these results, the imprinted nano patterns were compared. Silicon molds with nano size patterns were fabricated by e-beam direct writing. Molds were coated with self-assembled monolayer (SAM) of (1, 1, 2, 2H –perfluorooctyl)-trichlorosilane to reduce the stiction between molds and polymer substrates. For embossing, pressure of 500 psi, embossing time of 5 min and temperature of above transition temperature were applied. Mr-I 8010 polymer (Micro Resist Technology), Polymethylmethacrylate (PMMA 495k) and LOR (polyaliphatic imide copolymer) were used as substrate for hot embossing process development in nano size. These polymers were spun coated on the Si wafer with the thickness of 150 nm. The nano size patterns obtained by hot embossing were identified by atomic force microscopy without breaking the pattern and compared based on the polymer surface properties. The mr-I 8010 which has the lowest surface energy and adhesion force shows the best demolding property.

In this overview article several MEMS applications of poly-SiGe are discussed: thermal applications, the application as a capping layer for MEMS wafer-level packaging and the use as MEMS structural layer for processing MEMS devices on top of CMOS. For all these applications also different deposition processes have been developed: chemical vapor deposition at reduced pressure (RPCVD), at low pressure (LPCVD) and with plasma enhancement (PECVD). Special techniques to reduce the processing temperature to the absolute minimum are reviewed as well: the use of hydrogenated microcrystalline SiGe, of metal-induced crystallization and of laser annealing. The latter methods are important when one wants to process SiGe MEMS above advanced CMOS with low-permittivity dielectrics.

This paper reports optical studies on transparent electro-optic ceramics, 2%Er:PLZT and 0.5%Er-2.5%Yb:PLZT. Strong photoluminescence was observed in these polycrystalline ceramics in the 1550 nm region when pumped by diode lasers either at ∼970nm or ∼800nm. Efficient green upconversion luminescence was also observed. Co-doping Yb3+ did enhance the Er3+ emission in the 1550nm region when pumped with ∼970 nm diode laser. This work provides important information for developing microchip and high-power ceramic lasers using Er-doped PLZT ceramics.

Wafer and die level uniformity effects in Deep Reactive Ion Etching (DRIE) are quantitatively modeled and characterized. A two-level etching model has been developed to predict non-uniformities in high-speed rotating microstructures. The separation of wafer level and die level effects is achieved by sequentially etching wafers with uniformly distributed holes. The wafer level loadings range from 0.06% to 17.6%. Resulting wafer maps reflect the transition from an ion-limited region to a neutral-transport limited region. Additionally, long-range die-level interactions are also evaluated. Resulting die-level etching non-uniformities have a comparable magnitude to wafer-level effects. A model taking into account both the diffusion and reaction rate of neutrals is applied to predict the etching of up to 21 dies. Agreement between measurement and prediction support the hypothesis that the depletion of radicals is the main cause of die-level etch variation. The characterization and prediction methods are applied to etching a micro-scale turbine engine.

MEMS devices have unique packaging considerations compared to conventional semiconductor devices. They tend to have relatively large die size and many architectures cannot tolerate elevated temperatures. Often these devices require a vacuum environment for efficient operation. While advances have been made in hermetic packaging of MEMS devices, vacuum packaging remains elusive. One significant problem in developing vacuum sealing has been the inability to determine, readily and non-destructively, the vacuum level inside the package. We have previously described the development of a silicon MEMS-based chip design, “SensorChip™,” with integrated photonic crystal and reflective optics, which uses narrow-band optical emission and absorption for selective identification of gas and chemical species. Because the power consumption required to maintain a specific temperature is directly related to the vacuum level, these devices effectively serve as microscopic Pirani gauges – local vacuum sensors in the moderate vacuum range (0.01 to 1.0 torr) of interest to MEMS devices. Using the membrane itself as a vacuum gauge during sealing has proven to be an invaluable tool in developing a robust vacuum seal in a leadless chip carrier package. It has enabled us to optimize choice of design, materials and processing.

Precisely controlling the thickness of ultrathin silicon dioxide (SiO2) gate dielectric films is critical for high yield advanced generation semiconductor manufacturing. Advanced methods for producing ultrathin gates deposit both the gate dielectric and the polysilicon (poly-Si) gate electrode in a single cluster tool. This avoids the opportunity for adsorption of molecular airborne contamination (MAC) between deposition of the two layers, but necessitates measuring gate oxide thickness through a thick poly-Si layer.

Variations in poly-Si grain size, amorphous silicon content, and roughness, make it very difficult to model the optical feedback in the visible spectral range to resolve ultrathin (10–20 Å) gate oxides with sufficient accuracy and repeatability for process control.

This paper studies the optical behavior of the poly-Si/dielectric filmstack from 190 nm to 900 nm and the physical properties of the poly-Si layer. A more accurate modeling method is proposed to characterize the poly-Si and its top roughness layer using effective medium approximation (EMA) models. Using the new model, both a spectroscopic ellipsometer (SE) and a multi-angle multi-wavelength laser ellipsometer (MWLE) were employed to measure wafers with different poly-Si and gate oxide thicknesses. TEM was used to characterize the film thickness while roughness was determined using AFM. Good correlation was obtained between the TEM, AFM, and ellipsometry results. Excellent repeatability (0.04 Å 1σ on a 15 Å gate oxide for 10 days) and across the wafer uniformity (0.2 Å 1σ for a 49-point map) were also achieved when measuring gate dielectric films under the poly-Si with the MWLE.

A novel atomic force microscopy (AFM) probe has been developed to expand the capability and applications of dip-pen nanolithography (DPN) technology. This new probe has integrated microchannels and reservoirs for continuous ink feed, which allow “fountain-pen” writing called “Fountain Pen Nanolithography” (FPN). Ink is transported from the reservoirs through the microchannels and eventually dispensed onto substrates via a volcano-like dispensing tip. Numerical simulations have been performed to select optimal materials and suitable tip shapes providing a stable fluid-air interface in the tip. Microchannel and dispensing tip have been fabricated by surface micromachining, in particular employing 3 layers of thin films. Fluid flow through the microchannels has been experimentally examined. The probe was used to write on a gold substrate.