Litef Gmbh

Bruno F Ryrko

Eberhard Handrich

Martin Hafen

Uwe Breng

Thomas Gessner

Peter Leinfelder

Maik Wiemer

Egbert Vetter

Steffen Zimmermann

G&uuml;nter Spahlinger

Wolfram Ebert

Walter Gutmann

A micromechanical rotation rate sensor based on the Coriolis principle includes two plate-like oscillators arranged one above the other in two planes for excitation to oscillate by means of an electrostatic drive. Three elements in each case form an oscillator structure. The oscillators are in each case suspended on opposite side edges by at least one web between an associated plate-like support and an associated drive plate element. The two supports and the two drive plate elements are, in each case, arranged one above the other in layers. A fixed plate element is located between the two drive plate elements so that, in each case, an identical narrow drive gap is defined between the drive plate elements. The drive gap is considerably smaller than the distance between the plate-like oscillators. An intermediate support that fills the intermediate space is inserted between the two plate-like supports and is completely electrically isolated from the surrounding frame to further reduce the respective capacitances to be recharged. The invention reduces the electrodynamic coupling between the drive and the read-out by a factor of about 100 in comparison with known micromechanical rotation rate sensors of like design.

Micromechanical rpm sensor

For the drive excitation, the method for the capacitive drive excitation of oscillators in sensors for the capacitive measurement of force, acceleration and, in particular, rotation rates according to the Coriolis principle, provides according to the invention for the use of high-frequency constant-amplitude pulse packets with no DC component, the width or phase angle of which can be adjusted in order to keep the oscillator speed constant, for the purpose of resetting or correcting tolerances. As an alternative, the method may also be configured in such a way that, in the case of oscillators with pairwise excitation electrodes which are symmetrical with respect to the rotation axis, equal constant-amplitude HF voltages are applied, the frequency of which is chosen to be substantially higher than the natural frequency of the oscillator, in which case a particular resulting force of attraction on the oscillator is brought about by shifting the phase angle between the drive voltages and, in the case of rotation rate sensors working according to the closed-loop principle, system resetting can also be ensured. By virtue of the invention, problems with coupling the excitation signal into the read channel of a micromechanical oscillator system can be brought well under control.

Method of stimulating an oscillator control for capacitive measurement of strength, acceleration and/or rotation speed

Strictly out-of-phase stimulation of the two oscillators of a micro-mechanical rate-of-rotation sensor based on the Coriolis principle, having two-plate like oscillators arranged in layers one above another in two parallel planes and capable of being stimulated to oscillate perpendicular to the planes by means of an electrostatic drive, is achieved by the oscillators each being connected via at least one spring to a couple element formed, in each case, in the same wafer layer. The couple elements are mirror-symmetrically configured with respect to a mid-plane between the oscillators and connected to each other by a coupling web arranged therebetween to form a couple structure for the oscillators.

Micro-mechanical rate-of-rotation sensor with coupled structure

Micromechanical rotation speed sensor

A high precision micromechanical accelerometer comprises a layered structure of five (5) semiconductor wafers insulated from one another by thin oxide layers. The accelerometer is formed by first connecting a coverplate and a baseplate to associated insulating plates. Counter-electrodes, produced by anisotropic etching from the respective insulating plates, are fixed to the coverplate and the baseplate respectively. The counter-electrodes are contactable through the cover or baseplate via contact windows. A central wafer contains a unilaterally linked mass (pendulum) that is also produced by anisotropic etching and which serves as a movable central electrode of a differential capacitor. The layered structure is hermetically sealed by semiconductor fusion bonding. A stepped gradation from the top is formed at a wafer edge region for attaching contact pads to individual wafers to permit electrical contacting of individual wafers. The invention permits fabrication of a .mu.B device characterized by extremely small leakage capacitances and high temperature stability.

Micromechanical accelerometer with plate-like semiconductor wafers

A high precision micromechanical accelerometer comprises a layered structure of five (5) semiconductor wafers insulated from one another by thin semiconductor material oxide layers. The accelerometer is formed by first connecting a coverplate and a baseplate to associated insulating plates. Counter-electrodes, produced by anisotropic etching from the respective insulating plates, are fixed to the coverplate and the baseplate respectively. The counter-electrodes are contactable through the cover or baseplate via contact windows. A central wafer contains a unilaterally linked mass (pendulum) that is also produced by anisotropic etching and which serves as a movable central electrode of a differential capacitor. The layered structure is hermetically sealed by semiconductor fusion bonding. A stepped gradation from the top is formed at a wafer edge region for attaching contact pads to individual wafers to permit electrical contacting of individual wafers. The invention permits fabrication of a .mu.B device characterized by extremely small leakage capacitances and high temperature stability.

Micromechanical accelerometer and method of manufacture thereof

A micromechanical bending spring joint is formed of selectively etched wafer material. The joint includes a pair of leaf springs arranged alongside each other. Each spring is inclined at an oblique angle to the opposed surfaces of the wafer and such springs cross to define a point of intersection. The joint, selectively etched from a single wafer, is characterized by high precision of fulcrum position, bending spring constant and transverse axis rigidity.

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Reute, Germany

Bruno F Ryrko