PRESSURE SENSOR GENERATING A TRANSDUCED SIGNAL WITH REDUCED AMBIENT TEMPERATURE DEPENDENCE, AND MANUFACTURING METHOD THEREOF

• US 20160370242A1
• Filed: 12/28/2015
• Published: 12/22/2016
• Est. Priority Date: 06/22/2015
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Duqi, Enri, Conti, Sebastiano, Costantini, Sonia
• Granted Patent: US 10,809,140 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• 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 7/0061 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 1/00285 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81C 2201/0116 Thermal treatment for structural rearrangement of substrate atoms, e.g. for making buried cavities
• CPC Class Codes: B81C 2201/0133 Wet etching
• CPC Class Codes: B81C 2203/0145 Hermetically sealing an opening in the lid
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: G01L 9/065 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A pressure sensor designed to detect a value of ambient pressure of the environment external to the pressure sensor includes: a first substrate having a buried cavity and a membrane suspended over the buried cavity; a second substrate having a recess, hermetically coupled to the first substrate so that the recess defines a sealed cavity the internal pressure value of which provides a pressure-reference value; and a channel formed at least in part in the first substrate and configured to arrange the buried cavity in communication with the environment external to the pressure sensor. The membrane undergoes deflection as a function of a difference of pressure between the pressure-reference value in the sealed cavity and the ambient-pressure value in the buried cavity.

Claims

1. A pressure sensor configured to detect a value of ambient pressure of an environment external to the pressure sensor, comprising:

a first semiconductor body having an inner buried cavity, and a membrane suspended over the buried cavity;

a second semiconductor body having a recess, the second semiconductor body being hermetically coupled to the first semiconductor body in such a way that said recess faces the membrane, thus defining a sealed cavity having an internal pressure value that provides a pressure-reference value; and

a channel formed at least in part in the first semiconductor body and configured to set the buried cavity in fluidic communication with the environment external to the pressure sensor,

said membrane being configured to undergo deflection as a function of a pressure difference between the pressure-reference value in the sealed cavity and a pressure value in the buried cavity.

2. The pressure sensor according to claim 1, wherein said membrane houses a transducer assembly configured to generate a transduced electrical signal as a function of the deflection of the membrane, said transducer assembly being arranged in a surface portion of the membrane facing inside of the sealed cavity.

3. The pressure sensor according to claim 1, wherein the channel extends as partial prolongation of the buried cavity in a same plane as the buried cavity, reaching a side wall, orthogonal to said plane, of the first semiconductor body.

4. The pressure sensor according to claim 1, wherein the channel extends as partial prolongation of the buried cavity, in part along a first direction belonging to a plane of the buried cavity and in part along a second direction orthogonal to the first direction, reaching a side of the first semiconductor body exposed to the external environment.

5. The pressure sensor according to claim 4, further comprising:

a coupling region that completely surrounds the membrane, said first semiconductor body and second semiconductor body being hermetically coupled together via the coupling region, wherein said channel extends along the second direction in a portion of the first semiconductor body external to the coupling region.

6. The pressure sensor according to claim 1, wherein:

the channel extends in the first semiconductor body as partial prolongation of the buried cavity, in part along a first direction belonging to a plane of the buried cavity and in part along a second direction orthogonal to the first direction, reaching a side of the first semiconductor body facing the second semiconductor body, and

the channel further extends completely through the second semiconductor body, the buried cavity being in fluidic communication with the external environment through the channel in the second semiconductor body.

7. The pressure sensor according to claim 6, further comprising:

a coupling region that completely surrounds the membrane, said first and second semiconductor bodies being hermetically coupled together via the coupling region, wherein said channel further extends in the second direction through the coupling region.

8. The pressure sensor according to claim 1, comprising a getter layer housed in said recess and configured to reduce, when activated, the pressure value inside the sealed cavity.

12. The method according to claim 1, wherein forming the channel comprises:

etching the first semiconductor body as partial prolongation of the buried cavity, in a same plane as the buried cavity; and

cutting the first semiconductor body for exposing the channel at a side wall, orthogonal to said plane, of the first semiconductor body.

9. A method, comprising:

manufacturing a pressure sensor configured to detect a value of ambient pressure of an environment external to the pressure sensor, the manufacturing including;

forming, in a first semiconductor body, a buried cavity and a membrane suspended over the buried cavity;

forming, in a second semiconductor body, a recess;

hermetically coupling the second semiconductor body to the first semiconductor body so that said recess faces the membrane, thus defining a sealed cavity having an internal pressure value that provides a pressure-reference value;

forming a channel at least in part in the first semiconductor body; and

arranging the buried cavity in fluidic communication with the environment external to the pressure sensor via said channel.

10. The method according to claim 9, wherein the manufacturing includes forming a transducer assembly in a surface region of the membrane facing inside of the sealed cavity, the transducer assembly being configured to generate a transduced electrical signal as a function of a deflection of the membrane.

11. The method according to claim 9, wherein forming the buried cavity and forming the channel in the first semiconductor body are performed simultaneously.

13. The method according to claim 9, wherein forming the channel comprises:

etching the first semiconductor body as partial prolongation of the buried cavity in a first direction belonging to a plane of the buried cavity, to form a first subchannel; and

etching the first semiconductor body in a second direction orthogonal to the first direction, for connecting the first subchannel fluidically with a side of the first semiconductor body exposed towards the external environment, to form a second subchannel.

14. The method according to claim 9, wherein forming the channel comprises:

etching the first semiconductor body as partial prolongation of the buried cavity, along a first direction belonging to a plane of the buried cavity, to form a first subchannel;

etching the first semiconductor body along a second direction orthogonal to the first direction, for connecting the first subchannel fluidically with a side of the first semiconductor body facing the second semiconductor body, to form a second subchannel; and

etching the second semiconductor body to form a through hole fluidically connected to the buried cavity via the first and second subchannels.

15. The method according to claim 13, wherein the manufacturing includes:

forming a coupling region that surrounds the membrane completely; and

hermetically coupling together said first and second semiconductor bodies via the coupling region, wherein forming the second subchannel comprises etching the first semiconductor body outside the coupling region.

16. The method according to claim 14, wherein the manufacturing includes:

forming a coupling region that surrounds the membrane completely;

forming a through hole in the coupling region; and

hermetically coupling together said first and second semiconductor bodies via the coupling region, wherein forming the second subchannel comprises etching the first and second semiconductor bodies in an area corresponding to said through hole of the coupling region.

17. The method according to claim 9 wherein forming the membrane and the buried cavity comprise:

etching first trenches in the first semiconductor body, said first trenches delimiting between them first walls of semiconductor material;

growing epitaxially, starting from said first walls, a closing layer of semiconductor material, said closing layer closing said first trenches at the top to form said membrane; and

carrying out a thermal treatment such as to cause migration of the semiconductor material of said first walls and forming the buried cavity.

18. The method according to claim 17, wherein:

forming the channel comprises etching second trenches in the first semiconductor body, as partial prolongation of the first trenches, said second trenches delimiting between them second walls of semiconductor material;

growing the closing layer epitaxially further comprises closing said second trenches at tops of the second trenches; and

carrying out the thermal treatment further comprises causing migration of the semiconductor material of said second walls and forming the channel.

19. A pressure sensor configured to detect a value of ambient pressure of an environment external to the pressure sensor, comprising:

a first semiconductor body having an inner buried cavity, and a membrane suspended over the buried cavity;

a second semiconductor body hermetically coupled to the first semiconductor and defining a sealed cavity between the first and second semiconductor bodies, the sealed cavity having an internal pressure value that provides a pressure-reference value; and

a channel formed at least in part in the first semiconductor body and configured to set the buried cavity in fluidic communication with the environment external to the pressure sensor,

said membrane being configured to undergo deflection as a function of a pressure difference between the pressure-reference value in the sealed cavity and a pressure value in the buried cavity.

20. The pressure sensor according to claim 19, wherein said membrane houses a transducer assembly configured to generate a transduced electrical signal as a function of the deflection of the membrane, said transducer assembly being arranged in a surface portion of the membrane.