Low-profile stacked-die MEMS resonator system

Patent metadata

Field	Value
Publication number	US-10287162-B2
Application number	US-201715805031-A
Country	US
Kind code	B2
Filing date	Nov 6, 2017
Priority date	Jun 15, 2006
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A low-profile packaging structure for a microelectromechanical-system (MEMS) resonator system includes an electrical lead having internal and external electrical contact surfaces at respective first and second heights within a cross-sectional profile of the packaging structure and a die-mounting surface at an intermediate height between the first and second heights. A resonator-control chip is mounted to the die-mounting surface of the electrical lead such that at least a portion of the resonator-control chip is disposed between the first and second heights and wire-bonded to the internal electrical contact surface of the electrical lead. A MEMS resonator chip is mounted to the resonator-control chip in a stacked die configuration and the MEMS resonator chip, resonator-control chip and internal electrical contact and die-mounting surfaces of the electrical lead are enclosed within a package enclosure that exposes the external electrical contact surface of the electrical lead at an external surface of the packaging structure.

First claim

What is claimed is:

1. A microelectromechanical system (MEMS) device comprising:
a lead frame having a center opening and a plurality of leads;
a complementary metal oxide semiconductor (CMOS) die mounted in a flip-chip configuration on the lead frame and having first and second contacts, the second contacts being disposed adjacent and electrically coupled to the plurality of leads; and
a MEMS die mounted in a flip-chip configuration on the CMOS die and extending at least partly into the center opening in the lead frame, the MEMS die having a MEMS resonator and contacts coupled to the first contacts of the CMOS die.

2. The MEMS device of claim 1 wherein the contacts of the MEMS die comprise a first contact to receive a resonator-drive signal from the CMOS die and a second contact to output a resonator-sense signal to the CMOS die, the resonator-drive signal to drive the MEMS resonator into mechanically resonant motion and the resonator-sense signal being indicative of the mechanically resonant motion.

3. The MEMS device of claim 2 wherein the CMOS die comprises circuitry to receive the resonator-sense signal from the MEMS die via at least one of the first contacts and to generate the resonator-drive signal based at least in part on the resonator-sense signal.

4. The MEMS device of claim 3 wherein the CMOS die further comprises circuitry to generate a clock signal based on the resonator-sense signal and to compensate the clock signal according to temperature sensitivity of the MEMS resonator.

5. The MEMS device of claim 4 wherein the circuitry to compensate the clock signal according to temperature sensitivity of the MEMS resonator comprises a temperature sensor.

6. The MEMS device of claim 1 further comprising a package enclosure that envelopes the MEMS die and CMOS die.

7. The MEMS device of claim 6 wherein the plurality of leads are exposed at an exterior surface of the package enclosure.

8. The MEMS device of claim 1 wherein the lead frame comprises a die-mounting surface and wherein the CMOS die is affixed to the die-mounting surface.

9. The MEMS device of claim 8 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.

10. 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 apertures through which the contacts of the MEMS die are electrically coupled to the first contacts of the CMOS die.

11. A method of fabricating a microelectromechanical system (MEMS) device, the method comprising:
fabricating a lead frame having a center opening and a plurality of leads;
mounting a complementary metal oxide semiconductor (CMOS) die in a flip-chip configuration on the lead frame such that first contacts of the CMOS die are exposed in the center opening of the lead frame and second contacts of the CMOS die are disposed adjacent the plurality of leads;
electrically coupling the second contacts of the CMOS die to the plurality of leads;
fabricating a MEMS die having contacts and a MEMS resonator;
mounting the MEMS die in a flip-chip configuration on the CMOS die such that the MEMS die extends at least partly into the center opening in the lead frame and the contacts of the MEMS die are disposed adjacent the second contacts of the CMOS die; and
electrically coupling the contacts of the MEMS die to the first contacts of the CMOS die.

12. The method of claim 11 wherein electrically coupling the contacts of the MEMS die to the first contacts of the CMOS die the contacts of the MEMS die comprises:
coupling a first contact of the MEMS die to a drive contact of the CMOS die to enable reception, within the MEMS die, of a resonator-drive signal from the CMOS die; and
coupling a second contact of the MEMS die to a sense contact of the CMOS die to enable conduction of a resonator-sense signal from the MEMS die to the CMOS die, the resonator-drive signal to drive the MEMS resonator into mechanically resonant motion and the resonator-sense signal oscillating in response to the mechanically resonant motion.

13. The method of claim 12 further comprising fabricating, within the CMOS die, circuitry to receive the resonator-sense signal from the MEMS die and to generate the resonator-drive signal based at least in part on the resonator-sense signal.

14. The method of claim 13 further comprising fabricating, within the CMOS die, circuitry to generate a clock signal based on the resonator-sense signal and to compensate the clock signal according to temperature sensitivity of the MEMS resonator.

15. The method of claim 14 wherein fabricating the circuitry to compensate the clock signal according to temperature sensitivity of the MEMS resonator comprises fabricating a temperature sensor within the CMOS die.

16. The method of claim 11 further comprising enclosing the MEMS die and the CMOS die within a package enclosure.

17. The method of claim 16 wherein enclosing the MEMS die and the CMOS die within the package enclosure comprises exposing the plurality of leads at an exterior surface of the package enclosure.

18. The method of claim 11 wherein fabricating the lead frame comprises fabricating a die-mounting surface as part of the lead frame, and wherein mounting the CMOS die on the lead frame comprises affixing the CMOS die to the die-mounting surface.

19. The method of claim 18 wherein affixing the CMOS die to the die-mounting surface comprises adhering the CMOS die to the die-mounting surface using at least one of a thermally-conductive adhesive or an electrically-conductive adhesive.

20. The method of claim 11 further comprising disposing an electrically-insulating passivation layer between the MEMS die and CMOS die, and wherein electrically coupling the contacts of the MEMS die to the first contacts of the CMOS die comprises electrically coupling the contacts of the MEMS die to the first contacts of the CMOS die through apertures in the passivation layer.

Assignees

• Sitime Corp

Inventors

• Gupta Pavan
• Partridge Aaron
• Lutz Markus

Classifications

• H10W90/756

  between a chip and a stacked lead frame, conducting package substrate or heat sink · CPC title

• H10W74/111

  the semiconductor body being completely enclosed · CPC title

• H10W74/00

  Encapsulations, e.g. protective coatings · CPC title

• H10W72/884

  Die-attach connectors and bond wires · CPC title

• H10W70/60

  Insulating or insulated package substrates; Interposers; Redistribution layers (leadframes H10W70/40) · CPC title