Dual cavity pressure structures

• US 9,725,305 B2
• Filed: 03/16/2016
• Issued: 08/08/2017
• Est. Priority Date: 03/17/2015
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Lee, Daesung, Shin, Jong Il, Smeys, Peter
• Primary Examiner(s): Pham, Thanh V
• Application Number:
  US15/071,499
• Publication Number:
  US 20160272486A1
• Time in Patent Office: 510 Days
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2207/012 the micromechanical device and the control or processing electronics being separate parts in the same package
• 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 1/00214 Processes for the simultaneaous manufacturing of a network or an array of similar microstructural devices
• CPC Class Codes: B81C 1/00293 maintaining a controlled atmosphere with processes not provided for in B81C1/00285
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 2203/035 Soldering
• CPC Class Codes: G01P 15/0802 Details

Abstract

Provided herein is a method including forming a trench in a handle substrate, and a trench lining is formed in the trench. A first cavity and a second cavity are formed in the handle substrate, wherein the first cavity is connected to the trench. A first MEMS structure and the handle substrate are sealed for maintaining a first pressure within the trench and the first cavity. A second MEMS structure and the handle substrate are sealed for maintaining the first pressure within the second cavity. A portion of the trench lining is exposed, and the first pressure is changed to a second pressure within the first cavity. The first cavity and the trench are sealed to maintain the second pressure within the trench and the first cavity.

Claims

1. A method comprising:

forming a trench in a first side of a first silicon wafer;

forming a cavity connected to the trench in the first side of the first silicon wafer;

forming an oxide layer on the first side and in the trench;

bonding the first side of the first silicon wafer to a second silicon wafer;

forming a MEMS (micro-electro-mechanical systems) structure in the second silicon wafer;

bonding the second silicon wafer to a third silicon wafer,

removing a portion of a second side of the first silicon wafer, wherein the removing exposes the oxide layer;

setting a pressure within the trench and the cavity; and

forming a layer on the second side of the first silicon wafer, wherein the layer seals the trench, the cavity, and the MEMS structure.

2. The method of claim 1, wherein the bonding the second silicon wafer to the third silicon wafer includes eutectic bonding between the second silicon wafer and the third silicon wafer.

3. The method of claim 1, further comprising forming an additional cavity in the first side of the first silicon wafer.

4. The method of claim 3, wherein the additional cavity in the first side of the first silicon wafer includes a different pressure from the pressure within the trench and the cavity.

5. The method of claim 1, further comprising forming an additional MEMS structure in the second silicon wafer.

6. The method of claim 1, wherein the bonding the second silicon wafer to the third silicon wafer provides a hermetic seal and an electrical connection.

7. The method of claim 1, wherein the bonding the second silicon wafer to the third silicon wafer includes forming an aluminum-germanium bond.

8. The method of claim 1, wherein

the oxide layer is permeable to a gas, and

the setting the pressure within the trench and the cavity includes passing the gas through the oxide layer.

9. The method of claim 1,

wherein the oxide layer reduces the width of the trench, and wherein further the removing the portion of the second side of the first silicon wafer exposes a portion of the oxide layer;

and

further comprising removing a portion of the exposed portion of the oxide layer.

10. A method comprising:

forming a trench in a handle substrate;

forming a trench lining in the trench;

forming a first cavity and a second cavity in the handle substrate, wherein the first cavity is connected to the trench;

sealing a first MEMS structure and the handle substrate for maintaining a first pressure within the trench and the first cavity;

sealing a second MEMS structure and the handle substrate for maintaining the first pressure within the second cavity;

exposing a portion of the trench lining;

changing the first pressure to a second pressure within the first cavity; and

sealing the first cavity and the trench to maintain the second pressure within the trench and the first cavity.

11. The method of claim 10, further comprising removing a portion of the exposed portion of the trench lining.

12. The method of claim 10, wherein forming the trench lining includes growing silicon dioxide.

13. The method of claim 10, wherein

the width of the trench is 2 to 4 microns before the forming the trench lining, and

the width of the trench is 0.5 to 2.0 microns after the forming the trench lining.

14. The method of claim 10, wherein the sealing includes depositing a metal layer over the trench lining.

15. The method of claim 10, wherein

the trench lining is permeable to a gas, and

the changing the first pressure to a second pressure within the first cavity includes passing the gas through the trench lining.

16. The method of claim 10, wherein the gas is helium or hydrogen.