US 5,126,812 A · Monolithic micromechanical accelerometer

Abstract

A micromechanical accelerometer is disclosed comprising a mass of monocrystalline silicon in which a substantially symmetrical plate attached to a silicon frame by flexible linkages is produced by selective etching. The plate has a plurality of apertures patterned and etched therethrough to speed further etching and freeing of the plate and flexible linkages, suspending them above a void etched beneath. The plate has a weight disposed thereon near an end remote from the flexible linkages. The plate is capable of limited motion about an axis created by the flexible linkages. Stop means limit motion of the plate about the axis. Strain relief tension beams are provided to relieve stress induced by boron diffusion necessary to provide etch stopping and the tension beams are trimmable in a manner which permits tuning of the resonant frequency of the plate. Grooves or depressions are provided in the flexible linkages to resist bending or buckling without increasing torsional stiffness. The plate and flexible linkages are electrically isolated from the silicon mass and frame by dielectric or P-N junction isolation. Integral P-N junction electrodes and surface bridging electrodes may be used to provide top to bottom symmetry in torquing and sensing of the plate while maintaining isolation and monlithic construction. Bias and readout circuitry used to sense and torque the plate may be provided integrally with the plate and formed during plate processing.

Claims24

Dependent claims

A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising:

a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame;
a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame;
a plurality of electrodes disposed proximate to said void;
a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes;
and
a weight disposed asymmetrically on said plate and proximate to an end of said plate.

3 more elements

Dependencies are inferred from the claim text.

Monolithic micromechanical accelerometer

Life of this patent

Monolithic micromechanical accelerometer

Life of this patent

Abstract

Claims24