MEMS Integrated Pressure Sensor Devices and Methods of Forming Same

• US 20160159644A1
• Filed: 02/15/2016
• Published: 06/09/2016
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Chu, Chia-Hua, Cheng, Chun-Wen
• Granted Patent: US 10,017,382 B2
• Time in Patent Office: Days
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81B 7/0041 maintaining a controlled atmosphere with techniques not provided for in B81B7/0038
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• 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: B81B 7/04 Networks or arrays of similar microstructural devices
• CPC Class Codes: B81C 1/00134 comprising flexible or deformable structures manufacture of MEMS devices for specific applications, see relevant places, e.g. gyroscopes G01C19/5719, pressure sensors G01L9/0042, accelerometers G01P15/0802, acoustic transducers or diaphragms therefor H04R31/00
• CPC Class Codes: B81C 1/00293 maintaining a controlled atmosphere with processes not provided for in B81C1/00285
• CPC Class Codes: B81C 1/00309 suitable for fluid transfer from the MEMS out of the package or vice versa, e.g. transfer of liquid, gas, sound
• CPC Class Codes: B81C 2201/013 Etching
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5769 Manufacturing; Mounting; Housings
• CPC Class Codes: G01L 19/0076 using buried connections
• CPC Class Codes: G01L 19/0092 Pressure sensor associated with other sensors, e.g. for measuring acceleration or temperature G01L9/025, G01L9/045, G01L9/065, G01L9/085, G01L9/105, G01L9/125, G01L19/02, G01L19/04 take precedence; measuring two or more variable G01D21/02; temperature sensors with pressure compensation G01K1/26
• CPC Class Codes: G01L 9/0044 Constructional details of non-semiconductive diaphragms
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• CPC Class Codes: G01P 15/0802 : Details
• CPC Class Codes: G01P 15/125 : by capacitive pick-up

Abstract

A method embodiment includes providing a micro-electromechanical (MEMS) wafer including a polysilicon layer having a first and a second portion. A carrier wafer is bonded to a first surface of the MEMS wafer. Bonding the carrier wafer creates a first cavity. A first surface of the first portion of the polysilicon layer is exposed to a pressure level of the first cavity. A cap wafer is bonded to a second surface of the MEMS wafer opposite the first surface of the MEMS wafer. The bonding the cap wafer creates a second cavity comprising the second portion of the polysilicon layer and a third cavity. A second surface of the first portion of the polysilicon layer is exposed to a pressure level of the third cavity. The first cavity or the third cavity is exposed to an ambient environment.

Claims

1. A method comprising:

providing a device substrate comprising a membrane for a first micro-electromechanical (MEMS) device;

bonding a carrier having a first cavity to the device substrate, wherein bonding the carrier includes aligning the first cavity with a first surface of the membrane;

patterning the device substrate to define a first MEMS structure aligned with the membrane;

bonding a cap to the device substrate to form a second cavity comprising a second surface of the membrane and the first MEMS structure; and

patterning the carrier to expose the first cavity to ambient pressure.

2. The method of claim 1, wherein providing a device substrate comprises:

forming a polysilicon layer over a MEMS substrate, wherein patterning the device substrate to define the first MEMS structure comprises patterning the MEMS substrate; and

patterning the polysilicon layer to define the membrane.

3. The method of claim 1, wherein bonding the cap to the device substrate comprises at least partially defining a sealed pressure level for the second cavity, wherein the second surface of the membrane is exposed to the sealed pressure level of the second cavity.

4. The method of claim 3, wherein bonding the cap to the device substrate comprises using an eutectic bonding process to define the sealed pressure level of the second cavity.

5. The method of claim 1, wherein patterning the device substrate further defines a second MEMS structure for a second MEMS device, and wherein bonding the cap to the device substrate further forms a third cavity comprising the second MEMS structure.

6. The method of claim 5, wherein the second MEMS device is a motion sensor, a gyroscope, or an accelerometer.

7. The method of claim 1, wherein the first MEMS device is a pressure sensor.

8. The method of claim 1, wherein the cap comprises an input/output contact pad, and wherein the method further comprises exposing the input/output contact pad by removing a portion of the carrier.

9. A method comprising:

providing a device substrate comprising a membrane for a pressure sensor device;

bonding a carrier to the device substrate to define a first cavity, wherein a first surface of the membrane is exposed to a pressure level of the first cavity;

patterning the device substrate to define;

a first micro-electromechanical (MEMS) structure aligned with the membrane; and

a second MEMS structure adjacent the first MEMS structure; and

bonding a cap to an opposing side of the device substrate as the carrier, wherein bonding the cap defines;

a second cavity comprising the first MEMS structure, wherein a second surface of the membrane is exposed to an ambient pressure level through the second cavity; and

a third cavity comprising the second MEMS structure.

10. The method of claim 9, wherein providing the device substrate comprises

forming a polysilicon layer over a MEMS substrate, wherein patterning the device substrate to define the first MEMS structure and the second MEMS structure comprises patterning the MEMS substrate;

and

patterning the polysilicon layer to define the membrane and a trench in the polysilicon layer, wherein the trench provides a leak path allowing ambient air flow into the second cavity.

11. The method of claim 10 further comprising:

forming an oxide release layer over the polysilicon layer; and

after patterning the device substrate to define the first MEMS structure and the second MEMS structure, removing at least a portion of the oxide release layer using a vapor HF etching process.

12. The method of claim 11, wherein forming the oxide release layer comprises filling the trench with a first portion of the oxide release layer, and wherein the vapor HF etching process removes the first portion of the oxide release layer from the trench.

13. The method of claim 9, wherein bonding the carrier to the device substrate comprises a fusion bonding process, and wherein a sealed pressure level of the first cavity is at least partially defined by the fusion bonding process.

14. A micro-electromechanical (MEMS) device comprising:

a device substrate comprising;

a membrane for a pressure sensor, wherein a first surface of the membrane is exposed to a sealed pressure level of a first cavity and a second surface of the membrane is exposed to an ambient pressure level; and

a first MEMS structure over and aligned with the membrane;

a cap over first MEMS structure and bonded to the device substrate by a plurality of eutectic bonds; and

a carrier bonded to an opposing side of the device substrate as the cap.

15. The MEMS device of claim 14, wherein the first cavity is defined by the plurality of eutectic bonds between the cap and the device substrate.

16. The MEMS device of claim 15, wherein the second surface of the membrane is exposed to the ambient pressure level through a second cavity in the carrier.

17. The MEMS device of claim 15, wherein the first MEMS structure is disposed in the first cavity.

18. The MEMS device of claim 17, wherein the second surface of the membrane is exposed to the ambient pressure level through a third cavity connected to a leak path in the device substrate.

19. The MEMS device of claim 18, wherein the first MEMS structure is disposed in the third cavity.

20. The MEMS device of claim 14 further comprising:

a fourth cavity defined by the cap and the device substrate; and

a second MEMS structure adjacent the first MEMS structure and disposed in the fourth cavity.