Stacked die package for MEMS resonator system

• US 8,324,729 B2
• Filed: 06/02/2011
• Issued: 12/04/2012
• 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): Parekh, Nitin
• Application Number:
  US13/151,316
• Publication Number:
  US 20110227175A1
• Time in Patent Office: 551 Days
• Field of Search: 257/728, 257/666, 257/777, 257/784, 257/E23.141, 257/E23.031
• US Class Current: 257/728
• 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

A stacked die package for an electromechanical resonator system includes a chip that contains an electromechanical resonator bonded onto the control chip for the electromechanical resonator by a thermally and/or electrically conductive epoxy. In various embodiments, the electromechanical resonator can be a micro-electromechanical system (MEMS) resonator or a nano-electromechanical system (NEMS) resonator. Packaging configurations that may include the chip that contains the electromechanical resonator and the control chip include chip-on-lead (COL), chip-on-paddle (COP), and chip-on-tape (COT) packages. The stacked die package provides small package footprint and/or low package thickness, as well as low thermal resistance and a robust conductive path between the chip that contains the electromechanical resonator and the control chip.

Claims

1. A packaging structure for an electromechanical resonator system, the packaging structure comprising:

a control chip for a microelectromechanical resonator;

an electromechanical resonator chip that (i) includes the microelectromechanical resonator and (ii) is mounted on the control chip in a stacked die configuration, wherein the electromechanical resonator chip is physically coupled to the control chip by a thermally conductive epoxy;

a lead frame including at least one electrical lead having a mounting surface and an electrical contact surface, wherein the stacked die configuration is mounted on and physically coupled to the mounting surface of the electrical lead, and wherein the stacked die configuration is electrically coupled to the electrical lead; and

a mold compound, enclosing at least a portion of the lead frame and stacked die configuration of the control chip and the electromechanical resonator chip, wherein (i) the mounting surface of the electrical lead and the portion of the stacked die configuration which is mounted thereon are enclosed in the mold compound and (ii) the electrical contact surface of the electrical lead is externally exposed.

2. The packaging structure of claim 1, wherein the bulk layer of the electromechanical resonator chip is bonded to a passivation layer of the control chip via the thermally conductive epoxy.

3. The packaging structure of claim 2, wherein the thermally conductive epoxy has a coefficient of thermal expansion that is substantially equal to a coefficient of thermal expansion of a base material of the control chip and/or a base material of the electromechanical resonator chip.

4. The packaging structure of claim 1, wherein the at least one electrical lead is wirebonded to the control chip.

5. The packaging structure of claim 1, wherein the lead frame includes a plurality of electrical leads, wherein each lead has an exposed electrical contact surface positioned on an external surface of the packaging structure.

6. The packaging structure of claim 1, further including a first electrically conductive bonding wire, disposed within the mold compound, to electrically couple circuitry disposed on or in the control chip to the electromechanical resonator of the electromechanical resonator chip.

7. The packaging structure of claim 6, further including:

a second electrically conductive bonding wire disposed within the mold compound, and

wherein the second electrically conductive bonding wire electrically couples the control chip and the portion of the at least one electrical lead that is disposed in the mold compound.

8. The packaging structure of claim 1, wherein a first surface of the control chip resides on the mounting surface of the at least one electrical lead and is bonded thereto via electrically insulating epoxy.

9. The packaging structure of claim 8, wherein the electromechanical resonator chip is attached to a second surface of the control chip via the thermally conductive epoxy.

10. The packaging structure of claim 9, wherein the electromechanical resonator chip is electrically coupled to the control chip via a first bonding wire and wherein the first bonding wire is disposed within the mold compound.

11. The packaging structure of claim 10, wherein the control chip is electrically coupled to the lead frame via a second bond wire.

12. The packaging structure of claim 1, wherein the control chip includes a temperature sensor.

13. The packaging structure of claim 12, wherein the control chip compensates for changes in temperature of the microelectromechanical resonator using data from the temperature sensor.

14. The packaging structure of claim 13, wherein the thermally conductive epoxy thermally couples the electromechanical resonator chip to the control chip such that the temperature sensor generates data which is representative of the temperature of the electromechanical resonator chip.

15. The packaging structure of claim 14, wherein a first surface of the control chip resides on the mounting surface of the at least one electrical lead and is bonded thereto via electrically insulating epoxy.

16. The packaging structure of claim 15, wherein the electromechanical resonator chip is attached to a second surface of the control chip via the thermally conductive epoxy.

17. The packaging structure of claim 16, wherein the electromechanical resonator chip is electrically coupled to the control chip via a first bonding wire and wherein the first bonding wire is disposed within the mold compound.

18. The packaging structure of claim 1, wherein:

the control chip includes a temperature sensor and circuitry to compensate for changes in temperature of the microelectromechanical resonator using data from the temperature sensor; and

the thermally conductive epoxy thermally couples the microelectromechanical resonator to the temperature sensor such that the temperature sensor generates data which correlates to the temperature of the microelectromechanical resonator.

19. The packaging structure of claim 1, further including an electrically insulating material disposed between the stacked die configuration and the mounting surface of the electrical lead.

20. The packaging structure of claim 1, wherein the electrical contact surface of the electrical lead is an externally exposed portion of the packaging structure.