US 5,151,763 AGranted

Acceleration and vibration sensor and method of making the same

AssigneeRobert Bosch GmbH

InventorsJiri Marek, Frank Bantien, Dietmar Haack, Martin Warth

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Abstract

A semiconductor plate having an epitaxial layer of a conductivity type opposite to that of the substrate on which it is formed has a depression, including one or more elongate channels. The depression is etched into a depth passing entirely through the epitaxial layer to isolate at least one tongue extending from a tongue pedestal into the etched depression and having parallel major sides which are perpendicular to the principal planes of the semiconductor plate. The tongue is under-etched so that it will be free to vibrate by motion in directions parallel to the principal planes of the plate. One of the major sides of the tongue faces a stationary electrode across a gap and the electrode and the tongue are insulated from each other, at least in one embodiment, by the fact that the etched depression extends all the way through the epitaxial layer in its depth. Deflection or vibration of the tongue changes the capacitance between the electrode and the tongue and contacts are provided for measuring the capacitance. Various embodiments utilizing multiple tongues and one or more electrodes are shown.

Claims10

Dependent claims

A sensor for measurement of vibration or acceleration which is manufactured from a base plate of monocrystalline semiconductive material consisting of silicon containing minor amounts of other elements for affecting the conductivity types (p or n) of the material and having at least one tongue (12) etched out of said base plate and means for evaluating a deflection of said at least one tongue, characterized

in that said base plate comprises an upper layer (20) and a lower layer (21) which on account of n-type or p-type doping of said lower layer provides a pn junction in the case of said n-type doping or an np junction in the case of said p-type doping at its junction with said lower layer (21);
in that said at least one tongue has major sides perpendicular to a face surface of said base plate, has at least one major side facing, across a gap, a surface of said at least one electrode, has a firm root end which is integral with said base plate and has a free end longitudinally opposite to said root end, said electrode surface facing said tongue being perpendicular to a face surface of said base plate, said at least one tongue (12) and said at least one electrode (13) being formed entirely in said upper layer (20);
in that the surfaces respectively of said at least one tongue and of said at least one electrode are of said material consisting of silicon containing minor amounts of other elements;
in that said at least one tongue (12) and said at least one electrode (13) are insulated from each other by etched channels which extend in depth completely through said upper layer (20), and
in that, by virtue of electrical connections to said at least one tongue and said at least one electrode, a capacitance change between said at least one tongue and said at least one electrode is measurable, whereby the deflection of said tongue by vibration or acceleration of said base plate is measurable.

2 more elements

in that said base plate comprises an upper layer (21) and a lower layer (20) which on account of n-type or p-type doping of said lower layer provides a pn junction in the case of said n-type doping or an np junction in the case of said p-type doping at its junction with said lower layer (21);
in that said at least one tongue has major sides perpendicular to a face surface of said base late, has at least one major side facing, across a gap, a surface of said at least one electrode, has a firm root end which is integral with said base plate and has a free end longitudinally opposite to said root end, said electrode surface facing said tongue being perpendicular to a face surface of said base plate, said at least one tongue (12) and said at least one electrode (13) are formed entirely in said upper layer (20);
in that the surfaces respectively of said at least one tongue and of said at least one electrode are of said material consisting of silicon containing minor amounts of the elements;
in that said at least one tongue (12) and said at least one electrode (13) are insulated from each other by diffused isolation barriers (23) which extend in depth completely through said upper layer (20), and
in that by virtue of electrical connections to said at least one tongue and said at least one electrode, a capacitance change between said at least one tongue and said at least one electrode is measurable, whereby the deflection of said tongue by vibration or acceleration of said base plate is measurable.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/631,623Filed 21 Dec 1990
Priority: DE 400090315 Jan 1990
Granted: 29 Sep 1992
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01P 15/125
With conversion into electric or magnetic values: by capacitive pick-up
G01H 11/06
Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties: by electric means
G01P 15/0802
With conversion into electric or magnetic values: details
G01P 2015/0814
For one single degree of freedom of movement of the mass: for translational movement of the mass, e.g. shuttle type