Erwin Peiner

Piezoresistive cantilever as portable micro force calibration standard

Design, fabrication and test of cantilever-type sensors for active micro force calibration are described. The cantilever comprises a probing tip at its free end where a force can be applied which is measured using a piezoresistive strain gauge at the cantilever suspension. The stiffness of the cantilever is approximately given by the spring constant of a beam with a rectangular cross section as confirmed by finite element modelling. Prototypes with a stiffness of 0.66 N m?1 and 7.7 N m?1 are realized using standard silicon bulk micromachining technology. Testing is performed using a high-resolution micro force measuring set-up. In either case a highly linear relationship between the gauge output voltage and the probing force is revealed in the ?N range. Low scatter and drift corresponding to a standard deviation of ?0.22% was found for the resulting force sensitivity.

Doping Profile Analysis in Si by Electrochemical Capacitance‐Voltage Measurements

The electrochemical capacitance-voltage (ECV) technique was used to measure the carrier concentration profiles in Si. Using the conventional parallel-equivalent circuit model of the Schottky junction to describe the electrolyte-silicon barrier we found excellent agreement between ECV and four-point probe analyses within ±10 to 20% for bulk Si uniformly doped p- and n-type from 10 12 to 10 18 cm -3 . In this concentration range accuracy limits are determined mainly by the precise measurement of the area of the electrolyte-Si contact. For the anodic etching of Si, a constant effective dissolution valence of z=3.7 was used throughout the measurements. Investigations with isotype and anisotype doping transitions were performed employing ECV and other profiling techniques for comparison

Effect of III/V-Compound Epitaxy on Si Metal-Oxide-Semiconductor Circuits

Several approaches to the heteroepitaxial growth of InP on (100)Si employing an electrochemically etched Si mesa, SiO2 masks, and a maskless procedure were investigated with the objective of achieving area-selective InP integration into Si metal-oxide-semiconductor (Si-MOS) technology. Maskless InP/Si device layer growth by metal-organic vapour-phase epitaxy with good selectivity on a structured InP buffer layer, surrounded by oxide, was achieved. Undesired InP depositions were removed with an SiO2 emulsion, spun on prior to InP growth. To study the effects on the Si-based electronics, p-metal-oxide-semiconductor field-effect tansistors (MOSFETs) were exposed to the various stages of the heteroepitaxial InP growth process. We have studied the influence of hydride atmospheres and thermal anneals on their electrical performance. A standard InP-on-(100)Si growth procedure was found to be acceptable for the MOS components, as demonstrated by a Schmitt-trigger laser-diode driver circuit.

Diamond-like carbon for MEMS

Sputter-deposited amorphous diamond-like carbon (DLC, a-C) on silicon has been investigated with respect to micro electro mechanical systems (MEMS) applications. Sputtered a-C with a content of diamond-like sp3 bonded carbon of around 25% showed a high hardness of up to 30 GPa. Self-supporting cantilevers of 0.5 µm in thickness, several hundreds of µm in length and some tens of µm in width have been successfully realized using lift-off patterning of DLC and anisotropic silicon etching. The mechanical properties of DLC (Youngs modulus, stress, stress gradient fracture strength) were characterized by cantilever deflection analyses. DLC strain gauge resistors integrated on micromachined silicon boss membranes were investigated under tensile and compressive loading. Piezoresistive gauge factors in the range of 20–30 were observed at temperatures between room temperature and 50 °C.

Capabilities of ICP-RIE cryogenic dry etching of silicon: review of exemplary microstructures

Inductively coupled plasma (ICP) cryogenic dry etching was used to etch submicron pores, nano contact lines, submicron diameter pillars, thin and thick cantilevers, membrane structures and anisotropic deep structures with high aspect ratios in silicon for bio-nanoelectronics, optoelectronics and nano-micro electromechanical systems (NMEMS). The ICP cryogenic dry etching gives us the advantage of switching plasmas between etch rates of 13 nm min−1 and 4 µm min−1 for submicron pores and for membrane structures, respectively. A very thin photoresist mask can endure at −75 °C even during etching 70 µm deep for cantilevers and 300 µm deep for membrane structures. Coating the backsides of silicon membrane substrates with a thin photoresist film inhibited the lateral etching of cantilevers during their front release. Between −95 °C and −140 °C, we realized crystallographic-plane-dependent etching that creates facets only at the etch profile bottom. By varying the oxygen content and the process temperature, we achieved good control over the shape of the etched structures. The formation of black silicon during membrane etching down to 300 µm was delayed by reducing the oxygen content.

Evaluation of resonating Si cantilevers sputter-deposited with AlN piezoelectric thin films for mass sensing applications

We report on a micro-machined resonator for mass sensing applications which is based on a silicon cantilever excited with a sputter-deposited piezoelectric aluminium nitride (AlN) thin film actuator. An inductively coupled plasma (ICP) cryogenic dry etching process was applied for the micro-machining of the silicon substrate. A shift in resonance frequency was observed, which was proportional to a mass deposited in an e-beam evaporation process on top. We had a mass sensing limit of 5.2 ng. The measurements from the cantilevers of the two arrays revealed a quality factor of 155–298 and a mass sensitivity of 120.34 ng Hz−1 for the first array, and a quality factor of 130–137 and a mass sensitivity of 104.38 ng Hz−1 for the second array. Furthermore, we managed to fabricate silicon cantilevers, which can be improved for the detection in the picogram range due to a reduction of the geometrical dimensions.

Metastable phases formed by ion beam mixing of binary metal systems with positive heats of formation

Abstract Multilayered samples of ten binary metal systems of different overall compositions were bombarded at 77 K by 400 keV Kr + -ions. All systems have positive heats of formation, which means that in thermal equilibrium the miscibility in the solid state is small. The samples were analysed by in situ X-ray diffraction using a Seemann-Bohlin arrangement. The experiments led to the following results: - For the systems Au-Rh, Cu-Rh, and Cu-Ir, whose components all have fee structures, continuous series of single phase metastable fcc solid solutions are produced by ion beam mixing. - For the systems Au-Ir, Ag-Ir, and Ag-Rh, whose components all have fee-structures, and for the systems Au-Os, Au-Ru, Ag-Os, and Ag-Ru, where one component has fcc and the other has hcp structure, an extension of the terminal solid solubilities is obtained by ion irradiation. - Amorphous phase formation occurred during irradiation of the samples Au 50 Ir 50 , Au 70 Os 30 , and Au 49 Ru 51 . The dependence of the ion induced miscibility on the magnitude of the heat of formation is discussed.

Slender Tactile Sensor for Contour and Roughness Measurements Within Deep and Narrow Holes

A tactile cantilever sensor is described which was designed for quality assurance of high-aspect ratio microcomponents, e.g., spray holes of diesel injector nozzles. It was constructed as an extremely slender silicon cantilever of 1.5-5 mm in length, 30-200 mum in width, and 25-50 mum in height comprising a silicon probing tip at its free end. Close to its clamping, a piezoresistive strain gauge was integrated for signal read-out. The novel sensor was designed to be operated at high scanning speeds offering a millimeter scanning range at a micrometer lateral resolution and a ten nanometers vertical resolution. Cross sensitivity versus temperature and ambient light referred to vertical tip deflection was below 10 nm during a tactile measurement, which was performed under typical tactile probing conditions, i.e., temperature and light intensity variations of 1 K and 0.1 mW/cm 2, respectively. In form and roughness measurements with calibrated standard artifacts as well as with narrow spray holes of advanced diesel injector nozzles, we demonstrated the potential of slender cantilever sensors for high-aspect-ratio micrometrology.

Pick-and-Place Silver Sintering Die Attach of Small-Area Chips

A method for high-temperature-stable die attaches based on sintering of micro and nano silver particles is described. A low-temperature (200°C) and low-pressure (3 N/mm2) process was established to ensure compatibility with conventional adhesive die attach and to avoid surface damage on the dice, respectively. A modified flip-chip bonder providing high placement accuracy (2 μm) is used for a precise pick-and-place die attach. A thermal finite element modeling simulation was performed to analyze the bonding process. Additionally, the influence of the surface properties on the adhesion of sintered silver layers was investigated. The area-selective sintering method allows combination with other standard processes for die attach. It is now possible to establish pressure-assisted silver sintering for the series production of hybrid electronic circuits, which is an option requested by the industry to expand the operation range of sensors and electronics in harsh environments (e.g., measurement while drilling).

Sintering of Copper Particles for Die Attach

First steps are taken toward a low-cost alternative to silver sintering as a highly reliable die attach technology for deep drilling applications and future power electronic modules. In this feasibility analysis, we evaluate sintering of copper particles for die attach. Particulate copper pastes are pretreated in H2 atmosphere (50 mbar) in order to gain oxide-free particles. Subsequently, particles are sintered at a pressure of 40 N/mm2 and a temperature of 350°C for 2 min. Porosity, Youngs modulus as well as electrical and thermal conductivities of sintered layers are analyzed. Moreover, shear tests at ambient temperature are performed for evaluating the adhesion of monometallic as well as Cu-Au bonds according to the American military standard for chip-substrate contacts (MIL-STD-883H, method 2019.8).