Resonant inertial microsensor with variable thickness produced by surface engineering

Abstract

The invention relates to a surface-type MEMS resonant sensor, comprising a resonator (4) with excitation in a plane, which sensor comprises: a first, so-called thick area (2), having a first thickness (E1), forming a seismic mass,a second, thin area (4), having a second thickness (E2), lower than the first, for detection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show, in a top view and a side view, respectively, an inertial sensor according to the invention.

FIG. 1C shows, in a top view, an inertial sensor according to the invention with another arrangement of the elements in a plane.

FIG. 1D shows, in a top view, a device according to the invention, with two inertial sensors according to the invention assembled differentially.

FIGS. 2A to 2G and 3A to 3F show a first embodiment of a method according to the invention.

FIGS. 4A to 4F and 5A to 5E show a second embodiment of a method according to the invention.

FIGS. 6A to 6E and 7A to 7E show a third embodiment of a method according to the invention.

FIG. 8 shows a gyrometer.

FIGS. 9A and 9B show a top view and a side view, respectively, of an inertial sensor according to the prior art.

Claims

1. Surface-type MEMS resonant sensor, comprising a resonator with excitation in a plane, which sensor comprises: a first, so-called thick area, having a first thickness, forming a seismic mass,a second, thin area, having a second thickness (E2), lower than the first, for detection.

2. Sensor according to claim 1, of the accelerometer type, wherein the first area has a surface S smaller than 0.1 mm2.

3. Sensor according to claim 1, of the gyrometer type, wherein the first area has a surface S smaller than 5 mm2.

4. Sensor according to one of claims 1, wherein the first and second areas are formed in the superficial semiconductor layer of a SOI substrate.

5. Sensor according to claim 1, wherein it comprises a third area forming a hinge or a torsion axis.

6. Sensor according to claim 5, wherein the third area has a thickness between that of the first area and that of the second area.

7. Sensor according to claim 5, wherein the third area has a thickness equal to that of the first area.

8. Sensor according to claim 5, wherein the third area has a thickness equal to that of the second area.

9. Sensor according to claim 1, wherein it also comprises mechanical stops limiting the movement of the seismic mass.

10. Sensor according to claim 1, wherein it also comprises detection means.

11. Sensor according to claim 10, wherein the detection means comprise means for digital filtering and/or digital processing of the signal.

12. Surface detection device comprising a first resonant sensor and a second resonant sensor, each according to claim 1 with differential assembly.

13. Method for producing a surface-type MEMS resonant sensor comprising a resonator with excitation in the plane, which method comprises: the formation of a thick area, having a first thickness, forming a seismic mass,the formation of a thin area, having a second thickness, lower than the first, for detection.

14. Method according to claim 13, wherein the thick area and the thin area are formed by etching a layer of semiconductor material in three dimensions.

15. Method according to claim 13, wherein the thin and thick areas are formed by etching a surface semiconductor material layer of a SOI substrate, in a direction perpendicular to a main plane of said SOI substrate.

16. Method according to claim 13, wherein it also comprises the formation of a third area, called a hinge or torsion axis area, with a thickness between that of the first area and that of the second area.

17. Method according to claim 16, wherein the second area and third area are obtained by etching steps independent of one another.

18. Method according to claim 13, wherein it also comprises the formation of a third area, called a hinge or torsion axis area, with a thickness equal to that of the first area.

19. Method according to claim 18, wherein the first and second areas are obtained during a single etching step, independent of the etching step making it possible to produce the third area.

20. Method according to claim 13, wherein it also comprises the formation of a third area, called a hinge or torsion axis area, with a thickness equal to that of the second area.

21. Method according to claim 20, wherein the second and third areas are obtained in a single etching step, independent of the etching step making it possible to produce the first area.

22. Method according to claim 13, wherein the thin area is produced in a superficial semiconductor layer, and the thick area is produced in a semiconductor layer epitaxially grown on said superficial layer and in said superficial layer.