Chemistry: analytical and immunological testing – Optical result – With reagent in absorbent or bibulous substrate
Reexamination Certificate
1999-09-22
2001-11-20
Nelms, David (Department: 2818)
Chemistry: analytical and immunological testing
Optical result
With reagent in absorbent or bibulous substrate
C438S742000, C073S504040
Reexamination Certificate
active
06319729
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to angular rate sensors and, more particularly, to a method of manufacturing an angular rate sensor.
BACKGROUND OF THE INVENTION
There is a considerable need for angular rate sensors for a variety of electronic measuring systems. For example, safety systems in cars for preventing injuries during roll-over or skidding systems require devices for determining the rate of change of axial alignment of the vehicle. Current sensors providing appropriate signals for such systems are expensive to manufacture as they require complex designs and corresponding expensive production technology.
Some prior art devices employ electrostatic excitation of an element and the detection of a capacitance change movement of the element induced by the Coriolis effect. These devices have generally been made using silicon-on-insulator wafers or poly-silicon. The limitations of such arrangements are that their silicon wafers are extremely costly, or that poly-silicon devices are of poor manufacturing quality having non-uniform characteristics and built-in stresses that can cause unintended characteristics to occur, particularly in any sprung elements.
SUMMARY OF THE INVENTION
The present invention is directed towards overcoming some of the problems, both in terms of cost and manufacturing simplicity, of the prior art.
According to the present invention there is provided a method of manufacturing an angular-rate sensor comprising the steps of:
fabricating components of the angular-rate sensor on a silicon substrate, the components including one or more masses, a support beam and buried conductors;
providing detection means; and
sealing the components in a cavity between a first glass plate and a second glass plate by anodic bonding.
The invention therefore makes it possible to fabricate angular rate sensors using low cost silicon wafers.
Preferably, the detection means are electrodes formed by metal deposition on the first glass plate.
Preferably, the masses, beam and substrate are in substantially parallel planes, and the method further comprises the step of asymmetrically etching the beam such that, in use, it has a tendency to bend in a direction having components both parallel and perpendicular to the parallel planes.
The method may further comprise the step of forming a n-type epitaxial layer over the buried conductors to protect the conductors from the anodic bonding.
The substrate is preferably a n-type single crystal silicon substrate.
Preferably, the buried conductors are fabricated by the steps of:
applying a photoresist mask to a surface of the substrate;
implanting ions into the substrate at gaps in the photoresist mask;
diffusing the ions into the substrate.
P-type contacts to the buried conductors may be provided by the steps of:
applying a photoresist mask to a surface of the substrate;
implanting ions into the substrate at gaps in the photoresist mask;
diffusing the ions into the substrate.
Preferably the anodic bonding step further comprises providing a passivation layer on the substrate.
The method may further comprise the step of aligning the substrate and the first glass plate such that the first and second electrodes form one or more capacitors.
REFERENCES:
patent: 5635639 (1997-06-01), Greiff et al.
patent: 5952572 (1999-09-01), Yamashita et al.
patent: 410 22 495 (1992-01-01), None
patent: 0 598 477 (1994-05-01), None
patent: 0 744 603 (1996-11-01), None
Jakobsen Henrik
Kvisteroey Terje
Boyle Fredrickson Newholm Stein & Gratz S.C.
Le Dung A
Nelms David
SensoNor asa
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