Rudolf Buser

Very High Q-Factor Resonators in Monocrystalline Silicon

Note: 42 Reference SAMLAB-ARTICLE-1990-002 Record created on 2009-05-12, modified on 2016-08-08

Silicon cantilevers and tips for scanning force microscopy

Abstract Monocrystalline silicon cantilevers with integrated silicon tips for scanning force microscopy are fabricated by means of micromachining techniques. Theoretical considerations including finite element modelling have been carried out in order to find a suitable shape and dimensions according to the mechanical requirements. Several different cantilever designs have been fabricated: a simple beam with various cross sections as well as a folded meander shape with square cross section. Special attention has been paid to the application of these silicon microprobes to measure friction. Moreover, high-aspect-ratio silicon tips with variable geometries are presented and their integration onto cantilevers is demonstrated. Finally, the fabrication of an array of such microprobes is described, which enables multiple parallel or serial surface profiling to be achieved. These integrated micromachined cantilevers have been successfully applied in standard atomic force microscope measurement systems.

Micromachined atomic force microprobe with integrated capacitive read-out

The authors developed a micromachining process for the fabrication of highly sensitive capacitor probes to be used for displacement measurement of an atomic force cantilever. The capacitive structure consists of two adjacent single-crystal silicon beams, one carrying a sharp tip for the force interaction, the other being the counter-electrode. The air gap of 1.5 mu m separating the two electrodes is obtained by removal of the oxide in between by selective etching. The capacitance has a typical value of approximately=0.2 pF. Forces acting on the tip induce a bending of the cantilever and change the capacitance which can be detected by electronic circuits.

Resonant silicon structures

Note: 31 Reference SAMLAB-ARTICLE-1989-002doi:10.1016/0250-6874(89)80074-5 Record created on 2009-05-12, modified on 2016-08-08

ASEP : a CAD Program for Silicon Anisotropic Etching

Abstract A computer program is describe which simulates silicon single-crystal etching in KOH. Starting from a 2-D mask layout, the program finds the relevant etching planes and delivers a 3-D output of the etched structure with the etch time (or etch depth) as parameter. The resulting output plot is compared with realized test structures.

A high density microchannel network with integrated valves and photodiodes

We have realised a microchannel network with integrated valves, which allows parallel processing of nanoparticles with very high throughput. With the latest prototype, we could show for the first time, that integrated photodiodes are capable of detecting particles moving through the channels. In previous work, we have shown that manipulation of particles is possible. The size of the particles the system is designed for ranges from a few hundred nm to a few microns, which allows using the system for applications demanding the manipulation of biological cells or bacteria. Compared to related work on microvalve arrays with valve densities of around 100 valves in/sup -2/, our systems feature densities of up to 2150 valves in/sup -2/. This was achieved with a 3 microns thick silicone valve membrane. This is a factor of 10 less than thicknesses achieved in related work on thermopneumatic actuation with silicone rubber membranes.

Biaxial scanning mirror activated by bimorph structures for medical applications

Abstract We present here a micromachined scanning mirror as part of a keratotomy system which should be small enough to be set directly on the eye ball and thus follow its movement. The bimorph actuation type used here has the advantage of IC-compatible fabrication steps, high mechanical stiffness and a force independent of position. Beam and plate combinations of various sizes were fabricated to check the basic behaviour. The biaxial elements consist of a mirror plate and at least two independent actuators. The technological challenge of this device was to obtain a relatively thin silicon beam covered by a relatively thick aluminium layer. Doping of the silicon reduces the resistance and allows a guided current path, which is needed to drive the multiple actuator devices correctly. The insulation diodes show leakage currents of about 100 nA at 20 V. The dynamic range rises at least to 50 Hz which is sufficient for this device.

Silicon Pressure Sensor Based on a Resonating Element

Note: 51 Reference SAMLAB-ARTICLE-1991-006 Record created on 2009-05-12, modified on 2016-08-08

Tuning forks in silicon

The authors describe microfabricated tuning forks in silicon, which are excited electrodynamically. The pressure dependence of the resonance frequency and the Q-factor was measured by an interferometer over a range of pressure 1 mu bar to 2 bar. It is shown that micromachined structures in silicon have Q-factors which are comparable to those of similar quartz structures.<<ETX>>

CAD for silicon anisotropic etching

A computer program that simulates silicon single crystal etching in KOH is proposed. Starting from a two-dimensional mask the program finds the relevant etching planes and delivers a projected three-dimensional output of the etched structure with the etchtime (etchdepth) as parameter. The program is discussed and sample results are shown.<<ETX>>