Piezoelectric sensor apparatus

Patent metadata

Field	Value
Publication number	US-11487381-B2
Application number	US-201916512020-A
Country	US
Kind code	B2
Filing date	Jul 15, 2019
Priority date	Oct 29, 2015
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

An integrated force sensing element includes a piezoelectric sensor formed in an integrated circuit (IC) chip and a strain gauge at least partially overlying the piezoelectric sensor, where the piezoelectric sensor is able to flex. A human-machine interface using the integrated force sensing element is also disclosed and may include a conditioning circuit, temperature gauge, FRAM and a processor core.

First claim

What is claimed is:

1. An apparatus comprising:
a support structure having opposite first and second surfaces;
a silicon layer having respective opposite first and second surfaces, in which the first surface of the silicon layer is coupled to the first surface of the support structure;
a first dielectric layer on the second surface of the silicon layer;
a piezoelectric sensor including:
a first electrode on the first dielectric layer;
a second electrode; and
a piezoelectric material between the first and second electrodes;

a second dielectric layer over the second electrode;
a strain gauge over the second dielectric layer and at least partially overlying the piezoelectric sensor; and
a printed circuit board having a surface coupled to the second surface of the support structure, in which a cavity is interposed between the printed circuit board and the piezoelectric sensor, the cavity overlying the surface of the printed circuit board.

2. The apparatus of claim 1 , wherein the silicon layer has a thickness of 75 microns or less.

3. The apparatus of claim 2 , wherein the silicon layer has a thickness of 50 microns or less.

4. The apparatus of claim 1 , wherein the silicon layer has the cavity, at least part of the cavity extending through the silicon layer to the first dielectric layer.

5. The apparatus of claim 4 , further comprising a compliant material within the cavity.

6. The apparatus of claim 1 , further comprising a mold compound encapsulating at least the second dielectric layer and the strain gauge.

7. The apparatus of claim 1 , wherein the piezoelectric material is selected from a group consisting of: lead zirconate titanate (PZT), aluminum nitride (AlN), and zinc oxide (ZnO).

8. The apparatus of claim 1 , wherein the strain gauge includes silicon chromium (SiCr).

9. The apparatus of claim 1 , wherein the support structure is a lead frame.

10. The apparatus of claim 9 , wherein the cavity is interposed between the printed circuit board and the lead frame.

11. The apparatus of claim 9 , wherein the lead frame has the cavity, at least part of the cavity extending through the lead frame to the first surface.

12. The apparatus of claim 1 , wherein the strain gauge includes four strain gauge elements.

13. The apparatus of claim 12 , wherein the four strain gauge elements are four thin film resistors.

14. The apparatus of claim 13 , wherein the four thin film resistors are coupled in a Wheatstone bridge configuration.

15. The apparatus of claim 12 , wherein one or more of the four strain gauge elements has a serpentine shape.

16. The apparatus of claim 15 , wherein the four strain gauge elements include a thin film resistor material.

17. The apparatus of claim 1 , wherein the piezoelectric sensor includes ferroelectric capacitors coupled together in series and in parallel, in which a first ferroelectric capacitor includes the first and second electrodes and the piezoelectric material, and in which the remaining ferroelectric capacitors of the piezoelectric sensor include:
a respective first electrode;
a respective second electrode; and
a respective piezoelectric material between its first and second electrodes.

18. An apparatus comprising:
a support structure having opposite first and second surfaces;
a silicon layer having respective opposite first and second surfaces, in which the first surface of the silicon layer is coupled to the first surface of support structure;
a first dielectric layer on the second surface of the silicon layer;
a piezoelectric sensor including:
a first electrode on the first dielectric layer;
a second electrode; and
a piezoelectric material between the first and second electrodes;

a second dielectric layer over the second electrode;
a strain gauge over the second dielectric layer and at least partially overlying the piezoelectric sensor;
a printed circuit board having a surface coupled to the second surface of the support structure, in which a cavity is interposed between the printed circuit board and the piezoelectric sensor, the cavity overlying the surface of the printed circuit board;
a processor; and
a signal conditioning circuit having first and second inputs and an output, the first input coupled to the piezoelectric sensor, the second input coupled to the strain gauge, and the output coupled to the processor.

19. The apparatus of claim 18 , wherein one or more of the processor, the signal conditioning circuit, a random access memory (RAM), a temperature sensor, and a communications interface is in the silicon layer.

20. An apparatus comprising:
a silicon layer having opposite first and second surfaces;
a first dielectric layer on the second surface;
a piezoelectric sensor having first and second outputs, the piezoelectric sensor including ferroelectric capacitors coupled in series and in parallel, each ferroelectric capacitor including: a first electrode on the first dielectric layer; a second electrode; and a piezoelectric material between the first and second electrodes;
a second dielectric layer over the second electrode;
a strain gauge over the second dielectric layer and at least partially overlying the piezoelectric sensor, the strain gauge having respective first and second outputs and including four thin film resistors forming a Wheatstone bridge;
a multiplexer having first through fourth inputs and respective first and second outputs, its first and second inputs coupled respectively to the first and second outputs of the piezoelectric sensor, and its third and fourth inputs coupled respectively to the first and second outputs of the strain gauge; and
an amplifier including:
first and second buffers, each having respective first and second inputs and a respective output, the first input of the first buffer coupled to the first output of the multiplexer, and the first input of the second buffer coupled to the second output of the multiplexer; and
first and second resistors and a variable resistor, the first resistor coupled between the second input and the output of the first buffer, the second resistor coupled between the second input and the output of the second buffer, and the variable resistor coupled between the first and second resistors.

Assignees

• Texas Instruments Inc

Inventors

• Shih Wei-Yan
• Kummerl Steve
• Toth Mark Stephen
• Lohia Alok
• Sculley Terry Lee
• Lee Seung Bae
• Summerfelt Scott Robert

Classifications

• G01L1/22

  using resistance strain gauges · CPC title

• G06F3/0416 Primary

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F3/0414 Primary

  using force sensing means to determine a position · CPC title

• G06F3/044

  by capacitive means · CPC title

• G01L1/16

  using properties of piezoelectric devices · CPC title