Microelectromechanical systems using thermocompression bonding

• US 7,750,462 B1
• Filed: 10/30/2007
• Issued: 07/06/2010
• Est. Priority Date: 10/12/1999
• Status: Expired due to Fees

• Current Assignee: Microassembly Technologies Incorporated
• Original Assignee: Microassembly Technologies Incorporated
• Inventors: Cohn, Michael Bennett, Kung, Joseph T.
• Primary Examiner(s): COLEMAN, WILLIAM D
• Application Number:
  US11/929,115
• Time in Patent Office: 980 Days
• Field of Search: 257/704, 438/456, 228/123.6
• US Class Current: 257/704
• CPC Class Codes: B81C 1/00238 Joining a substrate with an electronic processing unit and a substrate with a micromechanical structure
• CPC Class Codes: B81C 2203/0109 Bonding an individual cap on the substrate
• 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 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: H01L 2224/05553 being rectangular
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48095 Kinked
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 2224/75 Apparatus for connecting with bump connectors or layer connectors
• CPC Class Codes: H01L 2224/7598 specially adapted for batch processes
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 2224/85207 Thermosonic bonding
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/49 of a plurality of wire connectors
• CPC Class Codes: H01L 24/75 Apparatus for connecting with bump connectors or layer connectors
• CPC Class Codes: H01L 24/81 using a bump connector
• 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 2924/00014 : 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 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01032 : Germanium [Ge]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01045 : Rhodium [Rh]
• CPC Class Codes: H01L 2924/01046 : Palladium [Pd]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• CPC Class Codes: H01L 2924/01077 : Iridium [Ir]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/1461 : MEMS
• CPC Class Codes: H01L 2924/15788 : Glasses, e.g. amorphous oxides, nitrides or fluorides
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/207 : Diameter ranges
• CPC Class Codes: H01L 2924/30105 : Capacitance
• CPC Class Codes: H01L 2924/3011 : Impedance

Abstract

Improved microelectromechanical systems (MEMS), processes and apparatus using thermocompression bonding are disclosed. For example, process embodiments are disclosed in which wafer-scale as well as die-scale thermocompression bonding is utilized to encapsulate MEMS and/or to provide electrical interconnections with MEMS. Apparatus embodiments include apparatus for performing thermocompression bonding and bonded hybrid structures manufactured in accordance with the process embodiments. Devices having various substrate bonding and/or sealing configurations variously offer the advantage of reduced size, higher manufacturing yields, reduced costs, improved reliability, improved compatibility with existing semiconductor manufacturing process and/or greater versatility of applications.

Claims

1. A sensor comprising:

a first substrate;

a microelectromechanical device disposed on the first substrate and having at least one electrical terminal;

a first bonding feature of bonding material disposed on the first substrate around the microelectromechanical device, wherein the bonding material comprises conductive bonding material in electrical contact with the at least one electrical terminal of the microelectromechanical device;

a second substrate which is in aligned confronting relation to the first substrate;

an integrated circuit disposed on the second substrate, the integrated circuit having at least one terminal; and

a second bonding feature of bonding material disposed on the second substrate, at least partially congruent with the first bonding feature, wherein the bonding material comprises conductive bonding material in electrical contact with the at least one terminal of the integrated circuit, the second substrate being bonded to the first substrate with the first and second bonding features bonded together to create a hermetically sealed cavity and with electric coupling of the microelectromechanical device and the integrated circuit.

2. The sensor of claim 1 wherein

the microelectromechanical device is an inertial sensor comprising a mass flexurally suspended from the first substrate and having terminals capacitively coupled to the mass such that the capacitance between the terminals and the mass varies as the mass is displaced;

and

the integrated circuit is a capacitive readout circuit, the first and second substrates being bonded such that the respective bumps and target features electrically couple the inertial sensor and the capacitive readout circuit.

3. The sensor of claim 1 wherein

the integrated circuit further comprises a voltage amplifier;

the first and second substrates are bonded such that the respective bumps and target features electrically couple the inertial sensor and the voltage amplifier.

4. The sensor of claim 1 wherein

the first and second bonding features of the first and second substrates are rings;

the bonds between the rings are thermocompressive bonds wherein least one of the rings has been plastically deformed.

5. A bonded hybrid structure comprising:

a first substrate;

a sensing device disposed on the first substrate and having electrical terminals comprising a plurality of bumps of conductive bonding material;

a dielectric substrate in aligned confronting relation to the first substrate;

a plurality of target features of conductive bonding material disposed on the dielectric substrate, at least partially congruent with the bumps of the first substrate;

the first substrate being thermocompressively bonded to the dielectric substrate to form a hybrid structure such that the plurality of bumps are bonded and electrically coupled to respective ones of the plurality of target features;

a plurality of conductive lines disposed on the dielectric substrate and extending from the target features bonded to the bumps of the first substrate;

a second substrate;

an integrated circuit disposed on the second substrate, and having electrical terminals comprising wire-bond pads; and

the hybrid structure being electrically coupled to the integrated circuit of the second substrate via the wire-bond pads.

6. An integrated device, comprising:

a first substrate;

a microelectromechanical device disposed on the first substrate;

a first bonding feature comprising conductive bonding material disposed on the first substrate to form a ring;

a bump of conductive bonding material disposed on the first substrate, the bump being in electrical contact with the device;

a second substrate substantially aligned in confronting relation to the first substrate;

a second bonding feature comprising conductive bonding material disposed on the second substrate;

a target feature made of conductive bonding material disposed on the second substrate; and

a wirebond pad disposed on the second substrate and electrically connected to the target feature, the first substrate and the second substrate being thermocompressively bonded without substantially heating the substrates and with the first bonding feature bonded to the second bonding feature to seal the microelectromechical device in a cavity between the first substrate and the second substrate with an electrical connection between the microelectromechanical device and the target feature and with plastic deformation of at least one of the ring or the second bonding feature.

7. The integrated device of claim 6, wherein the target feature is electrically isolated from the seal ring.

8. The integrated device of claim 6, wherein a portion of the ring thermocompressively bonded has a height less than about 50 microns.

9. The integrated device of claim 6, wherein the wirebond pad is outside the cavity, and the bump is in the cavity and electrically connected to the wirebond pad with a trace of conductive bonding material, the trace of conductive bonding material being electrically isolated from the second bonding feature.

10. The integrated device of claim 6, wherein the wirebond pad is electrically connected to the microelectromechanical device via the target feature.

11. The integrated device of claim 6, wherein the ring has a height that is less than about 100 microns after bonding and is electrically isolated from the conductive trace.

12. The integrated device of claim 10, wherein the conductive trace is at least 0.5 micron in height.

13. The integrated device of claim 10, wherein the conductive trace is at least about 1 micron in height.

14. A wafer-scale thermocompression bonding process for bonding at least first and second wafers together, the first wafer having a microelectromechanical device disposed thereon, the second wafer having an integrated circuit disposed thereon, the bonding process comprising:

electroplating bonding features including conductive bonding material onto predetermined locations of the first wafer, the bonding features surrounding the micro electromechanical device;

disposing target features of including conductive bonding material onto complementary locations of the second wafer, the complementary locations at least partially corresponding to the predetermined locations on the first wafer;

placing the first and second wafers in aligned confronting relation with one another such that the features of the first and second wafers are at least partially congruent; and

applying sufficient pressure and heat to the first and second wafers to plastically deform the features whereby the first and second wafers are thermocompressively bonded together and the integrated circuit and the microelectromechanical device are electrically connected by the bonding.

15. The wafer-scale thermocompression bonding process of claim 14 wherein

electroplating bonding features onto the predetermined locations comprises electroplating sealing rings onto the predetermined locations;

and

the process further comprises creating a sustainable vacuum in a cavity bounded by the sealing rings and the first and second wafers.

16. The wafer-scale thermocompression bonding process of claim 14 wherein

electroplating bonding features onto the predetermined locations comprises electroplating a sealing ring onto the predetermined locations;

and

the process further comprises hermetically sealing a cavity bounded by the sealing ring and the first and second wafers.

17. The wafer-scale thermocompression bonding process of claim 14 wherein the bonding material is selected from the group consisting of gold, copper, aluminum, palladium, gold-tin, lead-tin, indium-lead, gold-indium-lead.

18. An apparatus for thermocompressively bonding plural substantially planar substrates together, at least one of the substrates having a prefabricated microelectromechanical device disposed thereon, the substrates also having bonding material disposed thereon and being in aligned confronting relation with one another, the apparatus comprising:

first and second force transfer means positioned in spaced relation to one another along an axis such that the substrates can be placed into a gap therebetween, at least one of the first and second force transfer means being partially resilient in the direction of the axis;

means for applying an axially-directed compressive force to the force transfer means to thereby compress the substrates disposed in the gap;

means for preventing substantially all lateral movement of the force transfer means during application of the axially-directed compressive force; and

means for heating the substrates during application of the axially-directed compressive force to thereby plastically deform the bonding material and thermocompressively bond the substrates together.

19. The apparatus of claim 18 wherein

the first force transfer means is a beam having narrowed sections for providing resiliency in the beam;

and

the second force transfer means is a substantially rigid beam.

20. The apparatus of claim 18 wherein the first and second force transfer means comprise first and second billets each having a nominal diameter which generally corresponds to the substrates to be bonded, the billets having a pair of resilient lips held in confronting spaced relation to one another, the lips flexing in the axial direction during application of the axially-directed compressive force.

21. The apparatus of claim 18 wherein

the apparatus further comprises spacing means for spacing the first and second transfer means from one another;

and

the means for preventing substantially all lateral movement comprises a plurality of fasteners which nominally clamp the first and second force transfer means to the spacing means to thereby prevent substantially all lateral movement of the force transfer means.