Stacked-die MEMS resonator system

• US 9,821,998 B2
• Filed: 06/20/2016
• Issued: 11/21/2017
• Est. Priority Date: 06/15/2006
• Status: Active Grant

• Current Assignee: SiTime Corporation (Megachips Corporation)
• Original Assignee: SiTime Corporation (Megachips Corporation)
• Inventors: Gupta, Pavan, Partridge, Aaron, Lutz, Markus
• Primary Examiner(s): Diaz, Jose R
• Application Number:
  US15/187,748
• Publication Number:
  US 20170029269A1
• Time in Patent Office: 519 Days
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 2207/094 Feed-through, via
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• CPC Class Codes: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81B 7/0083 Temperature control
• CPC Class Codes: B81C 1/0023 Packaging together an electronic processing unit die and a micromechanical structure die MEMS packages B81B7/0032; MEMS packaging processes B81C1/00261
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: B81C 1/00333 Aspects relating to packaging of MEMS devices, not covered by groups B81C1/00269 - B81C1/00325
• CPC Class Codes: B81C 1/00341 Processes for manufacturing microsystems not provided for in groups B81C1/00023 - B81C1/00261
• CPC Class Codes: B81C 2201/016 Passivation
• 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 2203/0154 Moulding a cap over the MEMS device
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48245 the item being metallic
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 23/3107 the device being completely enclosed
• CPC Class Codes: H01L 23/34 Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements thermal treatment apparatus H01L21/00
• CPC Class Codes: H01L 23/498 Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers shape of the substrate H01L23/13
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• 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 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/1461 : MEMS
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H10N 30/302 : Sensors

Abstract

In a microelectromechanical system (MEMS) device, a CMOS die is affixed to a die-mounting surface and wire-bonded to electrically conductive leads, and a MEMS die is stacked on and electrically coupled to the CMOS die in a flip-chip configuration. A package enclosure envelopes the MEMS die, CMOS die and wire bonds, and exposes respective regions of the electrically conductive leads.

Claims

1. A microelectromechanical system (MEMS) device comprising:

a die-mounting surface;

electrically conductive leads;

a CMOS die affixed to the die-mounting surface;

wire bonds that extend from the CMOS die to the electrically conductive leads, respectively;

a MEMS die stacked on and electrically coupled to the CMOS die in a flip-chip configuration;

a package enclosure that envelopes the MEMS die, CMOS die and wire bonds and has an exterior surface at which respective regions of the electrically conductive leads are exposed; and

wherein the MEMS die comprises a resonant MEMS structure and wherein the CMOS die comprises circuitry to sense an electrical signal generated by motion of the resonant MEMS structure.

2. The MEMS device of claim 1 wherein the die-mounting surface comprises a lead frame and wherein the electrically conductive leads are fabricated as constituent members of the lead frame.

3. The MEMS device of claim 1 wherein the die-mounting surface comprises a first substantially planar surface of a die-attach paddle, the die-attach paddle having a second substantially planar surface at least partially exposed at the exterior surface of the package enclosure.

4. The MEMS device of claim 1 wherein the CMOS die comprises opposing first and second faces and wherein (i) the first face of the CMOS die is adhered to the die-mounting surface to affix the CMOS die to the die-mounting surface, (ii) the MEMS die is stacked on the second face of the CMOS die, and (iii) the wire bonds extend from the electrically conductive leads to respective contact points on the second face of the CMOS die.

5. The MEMS device of claim 1 wherein the CMOS die further comprises circuitry to compensate for temperature sensitivity of the resonant MEMS structure.

6. The MEMS device of claim 1 wherein at least one of the MEMS die and CMOS die comprises conductive flip-chip bumps soldered respectively to counterpart conductive contacts on the other of the MEMS die and CMOS die to establish the electrical coupling between the CMOS die and MEMS die.

7. The MEMS device of claim 1 further comprising an electrically-insulating passivation layer disposed between the MEMS die and CMOS die, the passivation layer having a plurality of apertures through which the MEMS die is electrically coupled to the CMOS die.

8. The MEMS device of claim 1 wherein the CMOS die is affixed to the die-mounting surface by at least one of a thermally-conductive adhesive or an electrically-conductive adhesive.

9. The MEMS device of claim 1 wherein the package enclosure comprises a molding compound that envelopes the MEMS die, CMOS die and wire bonds.

10. A method of fabricating a microelectromechanical system (MEMS) device having a CMOS die and a MEMS die, the method comprising:

fabricating a resonant MEMS structure within the MEMS die and fabricating circuitry within the CMOS die to sense an electrical signal generated by motion of the resonant MEMS structure;

affixing the CMOS die to a die-mounting surface;

wire-bonding electrically conductive package leads to the CMOS die;

stacking the MEMS die on and electrically coupling the MEMS die to the CMOS die in a flip-chip configuration; and

enveloping the MEMS die, CMOS die and wire-bonding within a package enclosure having an exterior surface at which respective regions of the electrically conductive leads are exposed.

11. The method of claim 10 wherein the die-mounting surface comprises a lead frame, the method further comprising fabricating the electrically conductive leads as constituent members of the lead frame.

12. The method of claim 10 wherein affixing the CMOS die to the die-mounting surface comprises affixing the CMOS die to a substantially planar first surface of a die-attach paddle that also has a substantially planar second surface, and wherein enveloping the MEMS die, CMOS die and wire bonds within the package enclosure comprises enveloping the first surface of the die-attach paddle within the package enclosure while at least partly exposing the second surface of the die-attach paddle at the exterior surface of the package enclosure.

13. The method of claim 10 wherein the CMOS die comprises opposing first and second faces and wherein (i) affixing the CMOS die to the die-mounting surface comprises adhering the first face of the CMOS die is adhered to the die-mounting surface, (ii) stacking the MEMS die on the CMOS die comprises stacking the MEMS die is stacked on the second face of the CMOS die, and (iii) wire-bonding the electrically conductive package leads to the CMOS die comprises wire-bonding the electrically conductive leads to respective contact points on the second face of the CMOS die.

14. The method of claim 10 further comprising fabricating within the CMOS die circuitry to compensate for temperature sensitivity of the resonant MEMS structure.

15. The method of claim 10 wherein stacking the MEMS die on and electrically coupling the MEMS die to the CMOS die in the flip-chip configuration comprises soldering conductive flip-chip bumps disposed on at least one of the MEMS die and CMOS die to respective counterpart conductive contacts on the other of the MEMS die and CMOS die.

16. The method of claim 10 further comprising disposing an electrically-insulating passivation layer between the MEMS die and CMOS die, the passivation layer having a plurality of apertures through which the MEMS die is electrically coupled to the CMOS die.

17. The method of claim 10 wherein affixing the CMOS die the die-mounting surface comprises affixing the CMOS die to the die-mounting surface using at least one of a thermally-conductive adhesive or an electrically-conductive adhesive.

18. The method of claim 10 wherein enveloping the MEMS die, CMOS die and wire bonds within a package enclosure comprises enveloping the MEMS die, CMOS die and wire-bonding within a molding compound.