MICRO-DEVICE HAVING A PLURALITY OF MOBILE ELEMENTS ARRANGED IN A PLURALITY OF EMBEDDED CAVITIES

• US 20180265348A1
• Filed: 03/12/2018
• Published: 09/20/2018
• Est. Priority Date: 03/16/2017
• Status: Active Grant

• Current Assignee: Safran SA
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Berthelot, Audrey, Colin, Mikael
• Granted Patent: US 10,472,227 B2
• Time in Patent Office: Days
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 2203/0315 Cavities
• CPC Class Codes: B81B 7/0038 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: B81C 1/00285 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81C 2201/0105 Sacrificial layer
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts

Abstract

A micro-device comprising:

• • a substrate,
  • a stationary element rigidly connected to the substrate,
  • a first mobile element suspended from the stationary element by first retention elements and configured to move with respect to the stationary element,
  • a second mobile element suspended from the first mobile element by second retention elements and configured to move with respect to the first mobile element and the stationary element,
  • a first cavity, at least some of the walls of which are formed by the stationary element and in which the first mobile element is encapsulated,
  • a second cavity positioned in the first cavity, at least some of the walls of which are formed by the first mobile element, in which the second mobile element is encapsulated and which is insulated from the first cavity.

Claims

1. A micro-device comprising at least:

a substrate,

a stationary element rigidly connected to the substrate,

a first mobile element suspended from the stationary element by first retention elements and configured to move with respect to the stationary element,

a second mobile element suspended from the first mobile element by second retention elements and configured to move with respect to the first mobile element and the stationary element,

a first cavity, at least some of the walls of which is formed by the stationary element and in which the first mobile element is encapsulated,

a second cavity positioned in the first cavity, at least some of the walls of which is formed by the first mobile element, in which the second mobile element is encapsulated and which is insulated from the first cavity.

2. The micro-device according to claim 1, wherein the stationary element forms a stationary frame rigidly connected to the substrate and wherein the first mobile element forms a mobile frame suspended from the stationary frame.

3. The micro-device according to claim 1, wherein at least one of the following conditions is fulfilled:

the first mobile element is configured to move in translation, or in rotation, or in translation and rotation, with respect to the stationary element;

the second mobile element is configured to move in translation, or in rotation, or in translation and rotation, with respect to the first mobile element and the stationary element.

4. The micro-device according to claim 1, wherein at least one of the following conditions is fulfilled:

the first retention elements comprise first arms for retaining in suspension, the ends of which are connected to the stationary element and to the first mobile element;

the second retention elements comprise second arms for retaining in suspension, the ends of which are connected to the first mobile element and to the second mobile element.

5. The micro-device according to claim 1, wherein the centres of the first and second cavities are aligned one above the other along an axis substantially perpendicular to the substrate.

6. The micro-device according to claim 1, further comprising at least one of:

at least one first opening formed through at least one of the walls of the first cavity, such that the pressure in the first cavity is substantially equal to a pressure outside of the micro-device;

at least one second opening formed through at least one of the walls of the second cavity, such that the pressure in the second cavity is substantially equal to the pressure outside of the micro-device.

7. The micro-device according to claim 1, further comprising at least one of:

a first cover rigidly connected to the stationary element and sealing the first cavity;

a second cover rigidly connected to the first mobile element and sealing the second cavity with respect to the first cavity, the second cover being mobile with respect to the first cover and the stationary element.

8. The micro-device according to claim 7, further comprising at least one of:

a first sealing bead rigidly connecting the first cover to the stationary element,

a second sealing bead rigidly connecting the second cover to the first mobile element, the second sealing bead being mobile with respect to the first sealing bead, the first cover and the stationary element.

9. The micro-device according to claim 1, further comprising at least one of:

elements for detection, or measurement, or detection and measurement, of a movement of the first mobile element with respect to the stationary element;

elements for detection, or measurement, or detection and measurement, of a movement of the second mobile element with respect to the first mobile element;

elements configured to move the first mobile element with respect to the stationary element;

elements configured to move the second mobile element with respect to the first mobile element.

10. The micro-device according to claim 1, further comprising:

a third mobile element positioned between the first and second mobile elements, suspended from the first mobile element by third retention elements, configured to move with respect to the first mobile element and the stationary element, and which is encapsulated in the second cavity,

a third cavity positioned in the second cavity, at least some of the walls of which is formed by the third mobile element, in which the second mobile element is encapsulated and which is sealed with respect to the atmosphere of the first and second cavities,

and wherein the second mobile element is suspended from the third mobile element by the second retention elements and is configured to move with respect to the third mobile element, the first mobile element and the stationary element.

11. A method for manufacturing a micro-device, comprising at least:

making a stationary element rigidly connected to a substrate;

making a first mobile element suspended from the stationary element by first retention elements and configured to move with respect to the stationary element,

making a second mobile element suspended from the first mobile element by second retention elements and configured to move with respect to the first mobile element and the stationary element,

making a first cavity, at least some of the walls of which is formed by the stationary element and in which the first mobile element is encapsulated,

making a second cavity positioned in the first cavity, at least some of the walls of which is formed by the first mobile element, in which the second mobile element is encapsulated and which is insulated from the first cavity.

12. The method according to claim 11, wherein the making of the stationary element, of the first mobile element and of the second mobile element comprises the implementation of the following steps:

etching of a first layer of material positioned on a first sacrificial layer itself positioned on the substrate, such that remaining portions of the first layer of material form the stationary element, the first mobile element, the second mobile element, the first retention elements and the second retention elements, then

etching of a portion of the first sacrificial layer through the first etched layer of material, making the first mobile element and the second mobile element mobile with respect to the stationary element.

13. The method according to claim 11, wherein the making of the first cavity and of the second cavity comprises the implementation of a transfer of a second layer of material onto the stationary element and the first mobile element, such that:

a first portion of the second layer of material is rigidly connected to the stationary element,

a second portion of the second layer of material, mobile with respect to the first portion of the second layer of material and forming a second cover of the second cavity, is rigidly connected to the first mobile element,

the first portion of the second layer of material is rigidly connected to a second substrate such the second layer of material is positioned between the stationary element and mobile elements and the second substrate that forms a first cover of the first cavity,

the second portion of the second layer of material is mobile with respect to the second substrate.

14. The method according to claim 11, wherein the making of the first cavity and of the second cavity comprises the implementation of the following steps:

etching of a second layer of material positioned on a second sacrificial layer itself positioned on a second substrate, forming a first portion of the second layer of material, a second portion of the second layer of material and fourth retention elements such that the second portion of the second layer of material is configured to be suspended from the first portion of the second layer of material by the fourth retention elements,

transfer of the second layer of material onto the stationary element and the first mobile element, such that the first portion of the second layer of material is rigidly connected to the stationary element and the second portion of the second layer of material is rigidly connected to the first mobile element,

etching of a portion of the second sacrificial layer through the openings passing through the second substrate, making the second portion of the second layer of material mobile with respect to the first portion of the second layer of material and the second substrate.

15. The method according to claim 13, wherein the transfer of the second layer of material onto the stationary element and the first mobile element comprises the implementation of direct bonding between the second layer of material and the stationary element and between the second layer of material and the first mobile element, or sealing between the second layer of material and the stationary element by a first sealing bead and sealing between the second layer of material and the first mobile element by a second sealing bead.