System and method for a three-axis MEMS accelerometer

• US 20050160814A1
• Filed: 01/24/2005
• Published: 07/28/2005
• Est. Priority Date: 01/24/2004
• Status: Active Grant

• Current Assignee: Nickolai Belov, Vladimir Vaganov
• Original Assignee: Nickolai Belov, Vladimir Vaganov
• Inventors: Belov, Nickolai, Vaganov, Vladimir
• Granted Patent: US 7,367,232 B2
• Time in Patent Office: Days
• US Class Current: 73/514.10
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: G01P 2015/0842 the mass being of clover leaf shape

Abstract

A system and method for inputting motion measurement data into a computationally based device are provided. In a first version three-axis accelerometer determines components of an inertial force vector with respect to an orthogonal coordinate system. The accelerometer includes a sensor die made of a semiconductor substrate having a frame element, a proof mass element, and an elastic element mechanically coupling the frame and the proof mass. The accelerometer also has three or more stress-sensitive IC components integrated into the elastic element adjacent to the frame element for electrical connectivity without metal conductor traversal of the elastic element.

Claims

1. A method of determining three components of an applied inertial force with respect to an orthogonal coordinate system, said method comprises the steps of:

providing a semiconductor sensor chip comprising a frame element, a proof mass element and an elastic element mechanically coupling the frame and proof mass element;

selectively positioning three or more stress-sensitive IC components integrated into the elastic element adjacent to the frame element for electrical connectivity without conductor traversal of elastic element surface;

applying a known inertial force to the sensor chip in at least three directions;

determining the offsets and matrix of sensitivities of the stress-sensitive IC components to the orthogonal components of the known applied force;

determining three orthogonal components of the applied inertial force by solving a system of at least three equations containing the three orthogonal components of the applied force, offsets and matrix of sensitivities of the stress-sensitive IC components to orthogonal components of the known inertial force vector.

2. A method of claim 1, further comprising the steps of providing additional stress sensitive components, which are used for increasing accelerometer reliability and accuracy by increasing the number of systems of equations for determining average values of the components of the applied force.

3. A three-axis accelerometer for determining components of an inertial force vector with respect to an orthogonal coordinate system, the accelerometer comprising:

a sensor die made of a semiconductor substrate comprising;

a frame element;

a proof mass element;

an elastic element mechanically coupling the frame and the proof mass, wherein the inertial force applied to proof mass induces stress in the elastic element;

three or more stress-sensitive IC components integrated into the elastic element adjacent to the frame element for electrical connectivity without metal conductor traversal of the elastic element,

whereby stress-sensitive IC components generate signals resulting from the stresses in the elastic element which are used in determining the applied force vector components.

4. A three-axis accelerometer of claim 3, whereby signals generated by stress-sensitive IC components from the applied force, are measured relative to at least one reference signal.

5. A three-axis accelerometer of claim 3, wherein the stress sensitive IC components are chosen from the group consisting essentially of:

a piezoresistor, a p-n junction, a tunnel diode, a Schottky diode, a shear stress component, a piezoresistive Wheatstone bridge, a MOS transistor, a complementary pair of CMOS transistors, a bipolar transistor, a pair of p-n-p and n-p-n bipolar transistors, a bipolar transistor and at least one piezoresistor connected to transistor, a MOS transistor and at least one piezoresistor connected to transistor, a bipolar transistor circuit, and a CMOS transistor circuit.

6. A three-axis accelerometer of claim 3, further comprising at least one sensor component chosen from the group of sensors consisting essentially of:

temperature sensor, magnetic sensor, pressure sensor, tactile sensor, acoustic sensor, chemical sensor, humidity sensor, radiation sensor, mass flow sensor, and optical sensor.

7. A three-axis accelerometer of claim 3, wherein the semiconductor substrate is comprised of material chosen from the group consisting essentially of:

elements from the IV group of the Periodic Table, silicon, germanium, silicon carbide, carbon, elements from III and V groups of the Periodic Table, gallium arsenide, gallium nitride, indium phosphide.

8. A three-axis accelerometer for determining components of an inertial force vector with respect to an orthogonal coordinate system, the accelerometer comprising:

a sensor die having side 1 and opposite side 2, die made of a semiconductor substrate comprising;

a frame element;

a proof mass element;

an elastic element having thickness and mechanically coupling the frame and the proof mass on side 1, wherein the inertial force applied to proof mass induces stress in the elastic element;

at least one cap mechanically coupled to the frame element from at least side 2 of the sensor chip, and

at least one electronic circuit coupled to accelerometer

whereby at least two dimensions of the proof mass element exceed the corresponding overall dimensions of the elastic element.

9. A three-axis accelerometer of claim 8, further comprising a proof mass, thickness of which exceeds the frame thickness but is less than the combined thickness of the frame and the cap coupled to the side 2 of the sensor die.

10. A three-axis accelerometer of claim 8, further comprising at least one electronic circuit providing one or more functions from a group of functions consisting essentially of:

sensing inertial force, sensing acceleration, sensing chemical parameters, providing reference signals, signal amplification, multiplexing, signal filtering, analog-to-digital conversion, signal processing, voltage stabilization, current stabilization, memory for compensation coefficients, temperature compensation, digital interface, power management, transmitting and receiving radio-signals, and power management of piezoelectric elements.

11. A three-axis accelerometer of claim 8 wherein at least one electronic circuit is located on the sensor substrate and has at least its portion located in the area directly above at least a part of proof mass.

12. A three-axis accelerometer of claim 8, wherein the semiconductor substrate is comprised of material chosen from the group consisting essentially of:

elements from the IV group of the Periodic Table, silicon, germanium, silicon carbide, carbon, elements from III and V groups of the Periodic Table, gallium arsenide, gallium nitride, indium phosphide.

13. A three-axis accelerometer of claim 8, where at least a portion of the proof mass element is composed of a material having a larger density than the semiconductor substrate.

14. A three-axis accelerometer of claim 8, further comprising a proof mass element consisting of at least two parts, a first integral part of a sensor die and at least one other part coupled with the first part and occupying a portion of the volume between the first part of the proof mass element and the frame of a sensor die.

15. A three-axis accelerometer of claim 8, wherein the elastic element has at least two portions of different thickness.

16. A three-axis accelerometer of claim 8, wherein the elastic element has at least one opening in its thickness dimension.

17. A three-axis accelerometer of claim 8, wherein the elastic element contains at least one stress concentrating element having a shape selected from a group of shapes consisting essentially of:

V-groove, trapezoidal groove, and a groove with the sidewalls forming an angle in the range of 90°

±

5°

with the surface of the elastic element.

18. A three-axis accelerometer of claim 8, wherein at least one electronic circuit comprises sensor components chosen from the group of sensors consisting essentially of:

temperature sensor, magnetic sensor, pressure sensor, tactile sensor, acoustic sensor, chemical sensor, humidity sensor, radiation sensor, mass flow sensor, and optical sensor.

19. A three-axis accelerometer of claim 8, where the elastic element in the sensor chip has the shape chosen from the group of shapes consisting essentially of:

ring, perforated ring, n-sided faceted geometry, beams, tethers, springs and combinations of these shapes.

20. A three-axis accelerometer for determining components of an inertial force vector with respect to an orthogonal coordinate system, the accelerometer comprising:

a sensor die having side 1 and opposite side 2, die made of a semiconductor substrate comprising;

a frame element;

a proof mass element;

an elastic element occupying at least three local areas and mechanically coupling the frame and the proof mass on side 1, wherein the inertial force applied to proof mass induces stress in the elastic element;

wherein the local areas of the elastic element are adjacent to proof mass from three sides and the proof mass has openings exposing the local areas of elastic elements from opposite side 2 of the sensor die.