Assembly of a capacitive acoustic transducer of the microelectromechanical type and package thereof

• US 8,433,084 B2
• Filed: 05/10/2010
• Issued: 04/30/2013
• Est. Priority Date: 05/11/2009
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Conti, Sebastiano, Vigna, Benedetto, Cortese, Mario Francesco
• Primary Examiner(s): Qin, Jianchun
• Application Number:
  US12/777,058
• Publication Number:
  US 20100284553A1
• Time in Patent Office: 1,086 Days
• Field of Search: 381/174
• US Class Current: 381/174
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• 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 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: H01L 2224/4554 Coating
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48145 the bodies being stacked
• CPC Class Codes: H01L 2224/48471 the other connecting portion not on the bonding area being a ball bond, i.e. wedge-to-ball, reverse stitch
• CPC Class Codes: H01L 2224/48479 on the semiconductor or solid-state body
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/16151 Cap comprising an aperture, e.g. for pressure control, encapsulation
• CPC Class Codes: H01L 2924/16152 Cap comprising a cavity for hosting the device, e.g. U-shaped cap
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 1/06 Arranging circuit leads; Relieving strain on circuit leads
• CPC Class Codes: H04R 1/086 Protective screens, e.g. all weather or wind screens
• CPC Class Codes: H04R 1/2838 of the bandpass type
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2201/003 : Mems transducers or their use

Abstract

A microelectromechanical-acoustic-transducer assembly has: a first die integrating a MEMS sensing structure having a membrane, which has a first surface in fluid communication with a front chamber and a second surface, opposite to the first surface, in fluid communication with a back chamber of the microelectromechanical acoustic transducer, is able to undergo deformation as a function of incident acoustic-pressure waves, and faces a rigid electrode so as to form a variable-capacitance capacitor; a second die, integrating an electronic reading circuit operatively coupled to the MEMS sensing structure and supplying an electrical output signal as a function of the capacitive variation; and a package, housing the first die and the second die and having a base substrate with external electrical contacts. The first and second dice are stacked in the package and directly connected together mechanically and electrically; the package delimits at least one of the front and back chambers.

Claims

1. A microelectromechanical acoustic transducer assembly, comprising:

a microelectromechanical system (MEMS) sensing structure including a sensing capacitor that includes;

a rigid electrode; and

a membrane integrated in a first die of semiconductor material, the membrane having a first surface in fluid communication with a front chamber and a second surface, opposite to the first surface, in fluid communication with a back chamber, said membrane being configured to undergo deformation as a function of incident acoustic-pressure waves from said front chamber, and facing the rigid electrode, the sensing capacitor having capacitance that varies as a function of the deformation of said membrane;

an electronic circuit integrated in a second die of semiconductor material, operatively coupled to said MEMS sensing structure, and configured to supply an electrical output signal as a function of the capacitive variation of said sensing capacitor; and

a package configured to house said first die and said second die and including a base substrate carrying electrical contacts for connection of said microelectromechanical acoustic transducer assembly externally, wherein;

said first die and said second die are stacked on one another in said package and are directly connected together mechanically and electrically,

said package directly delimits a first side at least one of said front chamber and said back chamber and the membrane delimits a second side of the at least one of said front chamber and said back chamber,

said first die includes a substrate having an active surface at which said membrane is arranged, and a rear surface starting from which the back chamber extends, through said substrate to said membrane; and

said second die is stacked on said first die and has a facing surface facing said active surface of said first die so as to be arranged over said membrane.

2. The assembly according to claim 1, wherein said second die is stacked on said first die in such a way as to define an empty space in a position corresponding to said membrane so as to enable the membrane to be deformed.

3. The assembly according to claim 2, further comprising:

bumps of conductive material configured to mechanically and electrically couple the first die with the second die and contribute to define said empty space above said membrane; and

a closing ring of conductive material set between said first die and said second die and surrounding said membrane, the closing ring being configured to hermitically close said empty space.

4. The assembly according to claim 1, wherein said rigid electrode is formed by a conductive layer carried by said second die, set adjacent to said facing surface of said second die.

5. The assembly according to claim 1, wherein said second die has a through hole configured to enable entry of said acoustic pressure waves, and in fluid communication with said membrane.

6. The assembly according to claim 5, wherein said package has an access port configured to enable entry of said acoustic pressure waves, and wherein said through hole is one of a plurality of through holes of said second die, the plurality of through holes being in fluid communication with said access port and said membrane, and being arranged in such a way as to define a mechanical filter with respect to impurities entering the assembly through the access port.

7. The assembly according to claim 6, wherein said through holes are arranged to form a honeycomb or checkerboard lattice and have a circular or square cross section in a plane extending parallel to a longitudinal plane of said membrane.

8. The assembly according to claim 7, wherein said through holes have in said cross section a diametric or lateral dimension between 20 μ

m and 200 μ

m, and are arranged, in said lattice, at a pitch between 30 μ

m and 300 μ

m from one another.

9. The assembly according to claim 5, wherein said second die comprises a silicon-on-insulator (SOI) wafer, and said through hole is provided through an active layer of said SOI wafer;

said second die having, in a position corresponding to said through hole, a cavity provided through an intermediate insulating layer and a base layer of said SOI wafer.

10. The assembly according to claim 5, wherein said package is a substrate-level package and comprises a coating set on said base substrate and laterally surrounding said first die and said second die;

and wherein said through hole defines an external access port.

11. The assembly according to claim 5, wherein said second die has doping and resistivity characteristics such as to be operable as a shield for an external electromagnetic disturbance;

the assembly further comprising a passivation material set on said facing surface of said second die and configured to provide a screen for incident light.

12. The assembly according to claim 5, wherein said second die has doping and resistivity characteristics such that the second die is configured to shield against an external electromagnetic disturbance.

13. The assembly according to claim 1, further comprising electrical connectors electrically connecting at least one of said first and second dies to said base substrate, the electrical connectors including electrical wire connections, and through vias provided through said first die and/or said second die.

14. The assembly according to claim 13, wherein said base substrate includes an outer surface, opposite to a surface for coupling with said first die and said second die, the assembly further comprising:

electrical contact pads positioned on the outer surface of the base substrate and configured to connect to an external electrical circuit board, and

through electrical connections extending through the base substrate and configured to enable electrical connection of said first die and/or said second die to said electrical contact pads.

15. The assembly according to claim 1, wherein said base substrate delimits and defines said at least one of said front chamber and said back chamber.

16. The assembly according to claim 1, wherein said package has a casing coupled to said base substrate and configured to define said at least one of said front chamber and said back chamber.

17. The assembly according to claim 16, wherein said package is a top-port package and said casing has an opening defining an access port configured to enable entry of said acoustic pressure wave;

said casing contributing to define said front chamber.

18. An electronic device, comprising;

a central processing unit; and

a microelectromechanical acoustic transducer assembly that includes;

a microelectromechanical system (MEMS) sensing structure including a sensing capacitor that includes;

a rigid electrode; and

a membrane integrated in a first die of semiconductor material, the membrane having a first surface in fluid communication with a front chamber and a second surface, opposite to the first surface, in fluid communication with a back chamber, said membrane being configured to undergo deformation as a function of incident acoustic-pressure waves from said front chamber, and facing the rigid electrode, the sensing capacitor having capacitance that varies as a function of the deformation of said membrane;

an electronic circuit integrated in a second die of semiconductor material, operatively coupled to said MEMS sensing structure, and configured to supply an electrical output signal as a function of the capacitive variation of said sensing capacitor; and

a package configured to house said first die and said second die and including a base substrate carrying electrical contacts for connection of said microelectromechanical acoustic transducer assembly externally, wherein;

said first die and said second die are stacked on one another in said package and are directly connected together mechanically and electrically,

said package directly delimits a first side at least one of said front chamber and said back chamber and the membrane delimits a second side of the at least one of said front chamber and said back chamber,

said first die includes a substrate having an active surface at which said membrane is arranged, and a rear surface starting from which the back chamber extends, through said substrate to said membrane; and

said second die is stacked on said first die and has a facing surface facing said active surface of said first die so as to be arranged over said membrane.

19. The electronic device according to claim 18, wherein said electronic device is one of:

a mobile phone, a PDA, a notebook, a voice recorder, an audio reader with voice-recorder functions, a console for videogames, a hydrophone.

20. The electronic device according to claim 18, wherein said package has an access port configured to enable entry of said acoustic pressure waves, and wherein said second die includes a plurality of through holes in fluid communication with said access port and said membrane, and arranged in such a way as to define a mechanical filter with respect to impurities entering the assembly through the access port.

21. A process for manufacturing a microelectromechanical acoustic transducer assembly, comprising:

forming a microelectromechanical system (MEMS) sensing structure having a sensing capacitor that includes a rigid electrode and a membrane integrated in a first die of semiconductor material, the membrane having a first surface in fluid communication with a front chamber and a second surface, opposite to the first surface, in fluid communication with a back chamber of said microelectromechanical acoustic transducer assembly, said membrane being configured to undergo deformation as a function of incident acoustic-pressure waves from said front chamber, and facing the rigid electrode, the sensing capacitor having capacitance varying with the deformation of said membrane;

forming, in a second die of semiconductor material, an electronic circuit operatively coupled to said MEMS sensing structure, and configured to supply an electrical output signal as a function of the capacitive variation of said sensing capacitor;

forming a package configured to house said first die and said second die, and comprising a base substrate carrying electrical contacts configured to connect said microelectromechanical acoustic transducer assembly externally; and

coupling said first die and said second die so that they are stacked on one another in said package and connected directly together mechanically and electrically, wherein forming the package comprises providing said package so that it delimits at least one between said front chamber and said back chamber of said microelectromechanical acoustic transducer, wherein;

forming said MEMS sensing structure includes forming the membrane in an active surface of a substrate of the first die and forming the back chamber starting from a rear surface of the substrate and extending through said substrate to said membrane; and

forming said second die includes stacking said second die on said first die and arranging a facing surface of the second die to face said active surface of said first die extend over said membrane.

22. The method according to claim 21, wherein said coupling is executed after forming said MEMS sensing structure in said first die and said electronic circuit in said second die.

23. The method according to claim 21, comprising forming a through hole through said second die by chemical etching, after forming said electronic circuit in said second die.

24. A microelectromechanical acoustic transducer assembly, comprising:

a microelectromechanical system (MEMS) sensing structure including a sensing capacitor that includes;

a rigid electrode; and

a membrane facing the rigid electrode and having a first surface in fluid communication with a front chamber and a second surface, opposite to the first surface, in fluid communication with a back chamber, said membrane being configured to undergo deformation as a function of incident acoustic-pressure waves from said front chamber, and being configured to have a capacitance that varies as a function of the deformation of said membrane;

a first die of semiconductor material;

an electronic circuit integrated in a second die of semiconductor material, operatively coupled to said MEMS sensing structure, and configured to supply an electrical output signal as a function of the capacitive variation of said sensing capacitor, wherein said first die and said second die are stacked on one another and are directly connected together mechanically and electrically; and

a base substrate on which the first and second dies are stacked, wherein said base substrate directly delimits a first side at least one of said front chamber and said back chamber and the membrane delimits a second side of the at least one of said front chamber and said back chamber, wherein;

said first die includes a substrate having an active surface at which said membrane is arranged, and a rear surface starting from which the back chamber extends, through said substrate to said membrane; and

said second die is stacked on said first die and has a facing surface facing said active surface of said first die so as to be arranged over said membrane.

25. The assembly according to claim 24, wherein the membrane is integrated in the first die of semiconductor material.

26. The assembly according to claim 24, further comprising:

bumps of conductive material configured to mechanically and electrically couple the first die with the second die and contribute to define an empty space above said membrane; and

a closing ring of conductive material set between said first die and said second die and surrounding said membrane, the closing ring being configured to hermitically close said empty space.

27. The assembly according to claim 24, wherein the first side is a bottom side of said back chamber and the second side is a top side of the back chamber.

28. The assembly according to claim 24, wherein said base substrate has an access port configured to enable entry of said acoustic pressure waves.

29. The assembly according to claim 24, wherein said base substrate includes an outer surface, opposite to a surface for coupling with said first die and said second die, the assembly further comprising:

electrical contact pads positioned on the outer surface of the base substrate and configured to connect to an external electrical circuit board, and

through electrical connections extending through the base substrate and configured to enable electrical connection of said first die and/or said second die to said electrical contact pads.

30. A microelectromechanical acoustic transducer assembly, comprising:

a microelectromechanical system (MEMS) sensing structure including a sensing capacitor that includes;

a rigid electrode; and

a membrane integrated in a first die of semiconductor material, the membrane having a first surface in fluid communication with a front chamber and a second surface, opposite to the first surface, in fluid communication with a back chamber, said membrane being configured to undergo deformation as a function of incident acoustic-pressure waves from said front chamber, and facing the rigid electrode, the sensing capacitor having capacitance that varies as a function of the deformation of said membrane;

an electronic circuit integrated in a second die of semiconductor material, operatively coupled to said MEMS sensing structure, and configured to supply an electrical output signal as a function of the capacitive variation of said sensing capacitor; and

a package configured to house said first die and said second die and including a base substrate carrying electrical contacts for connection of said microelectromechanical acoustic transducer assembly externally, wherein;

said first die and said second die are stacked on one another in said package and are directly connected together mechanically and electrically,

said package directly delimits a first side at least one of said front chamber and said back chamber and the membrane delimits a second side of the at least one of said front chamber and said back chamber,

said second die has a through hole configured to enable entry of said acoustic pressure waves, and in fluid communication with said membrane, and

said second die comprises a silicon-on-insulator (SOI) wafer, and said through hole is provided through an active layer of said SOI wafer;

said second die having, in a position corresponding to said through hole, a cavity provided through an intermediate insulating layer and a base layer of said SOI wafer.

31. The assembly according to claim 30, wherein:

said package is a substrate-level package and comprises a coating set on said base substrate and laterally surrounding said first die and said second die; and

said through hole defines an external access port.

32. The assembly according to claim 30, wherein said package has a casing coupled to said base substrate and configured to define said at least one of said front chamber and said back chamber.