The various problem areas regarding assembling of microelements into complex microsystems are reviewed and the joining techniques are emphasised in particular. The dis,-ussion is focused on the fabrication of microrobotic systems and the various joining techniques are compared with respect to the potential of fulfilling the demands for such a process. Factor.; such as processing conditions, precision, stability, materials limitations, bond and device strength are included in the comparison. Different methods for handling and manipulating microelements are discussed and the experimental equipment used in our own investigations is presented.

A new form of sp3/sp2 carbon has been fabricated which exhibits a large number of valuable properties. This material combines low density (≤1.65 g/cm3), low stress (≤0,05 GPa), low thermal expansion (1.6×10−6 K−1) with high hardness (˜ 30 GPa), modulus (˜ 200 GPa), cracking threshold (≥ 3 N), fracture toughness (≥ 10 MPa-m1/2), long-term thermal stability (≥ 450°C in air and ≥ 600°C without oxygen), extremely high thermal shock resistance, excellent interface and adhesion to silicon, metals, and ceramics and an absolute resistance to the silicon etching acids. Most of its properties are actually constant up to 700K. The material combines a basically amorphous structure with one-axis anisotropy and a graphite-like layered arrangement with a length scale of the modulation about 14Å. We refer to this quasi-amorphous material as QUASAM. This paper describes QUASAM synthesis conditions, growth front planarity and material characterization with high-resolution x-ray diffraction, positron annihilation spectroscopy, atomic force microscopy and micro-Raman spectroscopy. In addition the mechanical and thermal examination of QUASAM and QUASAM/Si will be presnted in terms of micro-electro-mechanical systems (MEMS) and the technology prospective requirements of MEMS.

Two types of novel organic materials have been specifically developed for the fabrication of optical-communications systems devices. One is a UV-curable durable epoxy adhesive featuring refractive index controllability, low shrinkage during curing, and a low heat-expansion coefficient. These optically transparent adhesives are refractive index controllable between 1.45 and 1.59, and have been successfully applied to many optical devices that require return losses of more than 40 dB. The precision adhesives show an extremely low volume shrinkage of less than 2% during curing. The submicron positioning accuracy of these adhesives allows the fabrication of highperformance laser-diode modules and optical modulators. The other type of material is a fluorinated polyimide (F-PI) for optical waveguides; it features high optical transparency from visible to near-infrared and good heat resistance. Buried optical waveguides fabricated from F-PI operate in a single mode. They also exhibit a low loss of less than 0.3 dB/cm at the wavelength of 1.3 μm, and are heat and moisture resistant: the increase in optical loss is less than 5% after heating at 300°C for lh or after exposure to 85% relative humidity at 85°C for 24h.

This paper reports on a multiprobe scanning force microscope (SFM) utilizing an array of individually controlled piezoelectric Pb(Zr,Ti)O3 (PZT) microcantilevers. Each cantilever is unimorph beam including a sol-gel derived PZT thin film that has high piezoelectric constants in comparison with sputtered ZnO films. The cantilever is excited and actuated in z direction by applying ac and feedback dc voltages to the PZT layer. The variation of vibration amplitude is detected by measuring the change of current through the PZT layer. The 200-μm-long PZT microcantilever with the natural resonance frequency of 63.8 kHz has the high actuation sensitivity of 150 nmN and the maximum range of more than 1.5 μm. By actuating the self-excited cantilever to keep the current constant, we have succeeded in independent dynamic operation without z feedback actuation of the sample-side scanner. We have obtained independent parallel 2 × 1 images using two cantilevers of the array.

This paper discusses the development of a novel selective electroless copper metallisation route for the plating of epoxy substrates. This has the potential for the development of a more cost effective and environmentally friendly plating process than currently available technologies. The electroless process required that the electrically insulating epoxy substrate was initially activated to catalyse the reduction of the copper (I1) salt which was in solution to a copper (0) deposit. Selective activation was achieved by coating the epoxy substrates with a new proprietary palladium compound and selectively exposing specific areas to 222nm radiation from a KrCI* excimer lamp. It has been shown that only the palladium metal and not the proprietary precursor catalyse the reaction. After selective seeding the patterned epoxy substrates were copper plated in a commercial electroless copper bath. The process conditions and effect of surface preparation on the quality and resolution of the selectively deposited copper patterns are discussed.

The principles of operation of a MEMS-based magnetometer designed on the magnetoelastic effect are described. The active transduction element is a commercial (001) silicon microcantilever sputter coated with an amorphous thin film of the giant magnetostrictive alloy Terfenol-D [(Dy0.7Tb0.3)Fe2]. The easy axis of magnetization of the Terfenol-D film lies in the plane of the microcantilever and along the acicular direction. In addition to the magnetostrictive transducer, basic components include: (a) mechanical resonance of the coated-microcantilever through coupling to an ac magnetic field; and, (b) detection by optical beam deflection of the microcantilever motion utilizing a laser diode source and a position-sensitive detector. The sensitivity of this magnetostrictive magnetometer is currently 1 μT, which is three orders of magnitude better than a magnetometer based on a similar-sized piezoresistive cantilever.

Atmospheric pressure chemical vapor deposition (APCVD) was used to grow silicon carbide (SiC) on as-deposited and annealed polycrystalline silicon (polysilicon) films which were deposited on oxidized Si wafers. X-ray diffraction (XRD) reveals that SiC films grown on asdeposited polysilicon have a (110) orientation. XRD performed on as-deposited polysilicon before and after SiC growth reveals that the orientation of polysilicon changes from (110) to a mixture of (110) and (11) during growth of 2 μm-thick SiC films. Cross-sectional transmission electron microscopy (XTEM) images of the SiC/polysilicon interface show that the SiC appears to be unaffected by the recrystallization of the underlying polysilicon during the SiC growth. XRD from samples of SiC grown on annealed polysilicon show that both films have (110) and (111) orientations. For SiC films grown on annealed polysilicon substrates, XTEM images show that the crystallinity of the annealed polysilicon substrate does not significantly change during SiC growth. Furthermore, an investigation of the SiC/annealed-polysilicon interface using selected area diffraction (SAD) shows that an epitaxial relationship exists between the polysilicon and SiC grains.

We have measured autoadhesion (e.g. stiction) of individual polysilicon beams by interferometric optical microscopy. Untreated cantilever beams were dried from water in air, while treated beams were coated with a hydrophobic molecular coating of octadecyltrichlorosilane (ODTS). Adhesion values obtained for beams adhered to the substrate over a long length (large d) are independent of beam length with values of 16.7 and 4.4 mJ/m2 for untreated and treated samples respectively. These values can be understood in terms of differences in surface chemistry and polysilicon roughness. Using the shortest length beam which remains attached to the substrate, adhesion values were 280 and 16 mJ/m2 respectively. These higher values may be a result of capillarity effects. We recommend that measurements be made on beams in which d is large, in contrast to the current practice of noting the shortest beam adhered.

Diamondlike carbon (DLC) thin films have been widely used as hard coatings in a variety of applications where increased wear resistance and hardness are required. Vacuum arc DLC films are among the hardest, with measured hardness values of up to 68 GPa. In our deposition process a repetitively pulsed bias voltage is applied to the substrate, which controls the energy of the incoming C ions. DLC chemical and mechanical properties are strongly affected by the energy of the depositing ions. In this paper, we relate the mechanical properties of these films to the deposition parameters, and describe our initial Brillouin scattering measurements of the elastic constants of monolithic DLC films. Evidence for bulk longitudinal and surface Rayleigh excitation in films with thickness of 50 and 500 nm has been observed. Since the DLC films are amorphous, they are modeled as isotropic solids and the elastic constants CII and C44 are derived.

Dual ion implantation of titanium and carbon was shown to produce an amorphous surface layer in annealed bulk nickel, in electroformed Ni, and in electroformed Ni7 5Fe 2 5. Diamond-tip nanoindentation coupled with finite-element modeling quantified the elastic and plastic mechanical properties of the implanted region. The amorphized matrix, with a thickness of about 100 nm, has a yield stress of approximately 6 GP and an intrinsic hardness near 16 GPa, exceeding by an order of magnitude the corresponding values for annealed bulk Ni. Implications for micro-electromechanical systems are discussed.

The development of a variety of micro-optical chemical sensor and biosensor devices will rely on an ability to fabricate and effectively pattern physically and chemically sensitive materials. Toward this end, organically modified sol-gel materials are patterned onto a substrate using a benign technique called micro molding in capillaries (MIMIC). Closely spaced, organically modified silica ridges containing organic dyes are demonstrated. The mold consists of a micro channel-filled elastomeric master in contact with a glass substrate. Liquid sols fill the mold as a result of capillary action. A reservoir-channel system in the mold allows simultaneous casting of sols with different chemical compositions. After gelation, the elastomeric master is removed and sol-gel structures are left on the substrate. Cross-sectional dimensions of the ridges range from one to tens of micrometers, and can be centimeters in length. Because of the mild processing conditions, the method is especially attractive for solgel materials containing sensitive molecules such as indicator dyes and biomolecules. The technique holds promise for microfabricated sensor and integrated optics applications.

A variety of rotating micro structures were designed, fabricated and characterized for residual-stress (or strain) measurements in low-stress silicon nitride thin films, deposited by LPCVD on silicon wafers. The sensitivities of the micro structures were calculated by finite element method (FEM) and verified experimentally. The results were further confirmed by utilizing the wafer-curvature method for stress measurements. The size of the structures enables local residual-stress (or strain) measurement. The stress level depends on both the film thickness and the gas ratio and also varies with the location on the wafer.

This paper presents the process and experimental results about the improved initial bonding between #7740 glass and silicon wafers. We employed a modified initial bonding procedure, called by water-enhanced direct bonding(WDB) technique, and could obtain large initially-bonded area(≥ 95% of the whole wafer area) at room temperature and high interface energy (≥ 2,000 erg/cm2) through 250 °C post-annealing even though the glass wafer had high surface roughness. The main factors contributing to the wider bonded area and higher interface energy in the developed WDB process could be inferred the increase of chemical species (oxygen and hydroxyl groups) responsible for initial hydrogen bonding and conversion from hydroxyl bonds to siloxane bonds in the temperature range between room temperature and 250 °C.

Polycrystalline silicon, used as a transducing material in high temperature Silicon On Insulator piezoresistive pressure sensor, is well known to be strongly dependent on the process parameters. Indeed depending on the deposition, doping and annealing conditions, the structural parameters of polysilicon namely grain size and texture may be very different. We use here a complete model of the piezoresistivity in polysilicon including a significant effect at grain boundaries to study the influence of structural parameters on the resistivities, gauge factors and their thermal drifts between room temperature and 200°C. The model validity has been verified experimentally for two types of polysilicon materials (LPCVD at 620°C and LPCVD at 580°C), subsequently B-doped (from 9×1018 to 9×1019 cm−3) and annealed by Rapid Thermal Annealing at 1100°C/20s and 1100°C/40s respectively. A good agreement between theoretical and experimentally determined resistivities and gauge factors at a variable temperature is observed for the two types of polysilicon materials considering different grain sizes with a <110> dominant texture for LPCVD 620°C series and no preferential texture for LPCVD 580°C series.

The layout design of membrane-based sensors such as Silicon On Insulator micromachined pressure sensors requires the knowledge of the mechanical behavior of the complete structure as a function of pressure and temperature. Unfortunately, as a result of thermal mismatch, large stresses usually exist in composite SiO2/Si membranes that significantly affect the pressure response of such sensors, We present here an original study on the 3D-FEM modeling (ANSYS) of pre-stressed SiO2/Si membranes submitted to pressure. The model of thermoelastic stress (without any applied pressure) has been first validated by optical profilometry deflection measurements. 2.94 mm width membranes with Si thickness varying from 10.7 to 19.3 μm, as measured by FT-IR, and covered with 1.46 μm thick thermal oxide grown at 1130°C, have been studied. Thermoelastic deflections from I to 25 μm have been measured for decreasing Si thickness in agreement with the simulation. The simulated longitudinal stress relaxation over the oxide varies from 5 to 40 MPa between the membrane center and the frame when decreasing membrane thickness. Under pressure (10 and 100 mbar) and for a 19.3 μm thick composite membrane (0.5 )μm thick oxide), the calculated strains can exceed by 20% that of a bare Si one, due to a lower overall stiffness produced by the oxide compressive stress.

This paper gives a brief overview of fabrication problems and solutions for microelectromechnical system (MEMS) using PZT films based on surface micromachining techniques. In addition we report characteristics of PZT films on diagnostic test structures designed to test the new bottom electrode for MEMS. PZT(53/47) films were deposited by metalorganic decomposition on a 3″ silicon wafer with Pt/Ti/TiO2/Poly-Si/Si3N4 structure in order to fabricate piezoelectric cantilever beam microaccelerometers and uncooled infrared (IR) detectors. In order to investigate the feasibility of RuO2/Ru and Pt/RuO2 conducting layers as a new bottom electrode for piezoelectric MEMS, the piezoelectric constant (d33) of the PZT films on each bottom electrode was measured. Furthermore, we show the fraction of working top electrodes among 20 total electrodes according to electrode size to investigate the stability of PZT with different bottom electrodes. These results suggest that RuO2/Ru and Pt/RuO2 are possible for bottom electrodes of MEMS.

The ferroelectric (Pb, La) (Zr,Ti)03 (PLZT(9.4/65/35)) optical waveguiding thin films have been prepared on SiO2 coated Si and on silica glass substrates by pulsed laser deposition. X-ray θ–2θ scans revealed that the films are single-phase pseudo-cubic perovskite. The surface chemical composition of the as grown films were determined by XPS. The ferroelectric properties of the films as grown on Pt/Ti coated silicon were demonstrated by using a modified Sawyer-Tower circuit, and the optical waveguiding properties of the films were characterized by using a rutile prism coupling method. The as grown films have an average transmittance of 80% in the wavelength range of 400˜2000nm and a refractive index of 2.2 at 632.8mn close to the bulk PLZT. The distinct m-lines of the guided TM and TE modes of the films as grown on SiO2 coated Si substrates have been observed.

Piezoelectric/nonpiezoelectric multilayer films were prepared by using pulsed laser deposition technique. The piezoelectric ZnO layers were completely (0001) textured and had the piezoelectric coefficient d33. The nonpiezoelectric (inactive) Al2O3 layers were amorphous and acted as good media for microwave and supersonic wave propagation. The periods were controlled by the deposition time in the range of 2.0 to 400 nm with the total period number of 4 to 30. In the multilayer films with ultrashort period of 2.1 nm, (0002) X-ray diffraction peak of ZnO layers was considerably broadened by the noncrystalline Al2O3 layers. In the multilayer films with short period of 6.4 nm, the diffraction peaks presented in small angle implies that the interfaces between layers were much flat and sharp, And in the multilayer films with long period, (0002) peak was very sharp, similar to the normal ZnO thin films. High frequency resonance was measured in the long-period multilayer films in the range of 1 - 20 GHz and higher frequency resonance is expected in the multilayer films with shorter period.