Wafer Level Structures and Methods for Fabricating and Packaging MEMS

• US 20120142144A1
• Filed: 11/29/2011
• Published: 06/07/2012
• Est. Priority Date: 12/03/2010
• Status: Active Grant

• Current Assignee: Integrated Biosensing Technologies
• Original Assignee: Integrated Biosensing Technologies
• Inventors: Taheri, Babak
• Granted Patent: US 8,569,090 B2
• Time in Patent Office: Days
• US Class Current: 438/107
• CPC Class Codes: B81B 2207/092 Buried interconnects in the substrate or in the lid
• CPC Class Codes: B81B 2207/095 through the lid
• CPC Class Codes: B81B 2207/096 through the substrate
• CPC Class Codes: B81B 2207/097 Interconnects arranged on the substrate or the lid, and covered by the package seal
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• 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: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/32145 the bodies being stacked
• 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 2224/73265 Layer and wire connectors
• 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

Abstract

Methods of fabricating a Micro-Electromechanical System (MEMS) in a hermetically sealed cavity formed at a substrate level are provided. Generally, the method comprises: (i) forming a number of first open cavities in a surface of a first substrate and a number of second open cavities in a surface of a second substrate corresponding to the first open cavities; (ii) forming an actuator/sensor layer including a number of MEMS devices with electrically conductive regions therein; (iii) bonding the first substrate and the second substrate to the actuator/sensor layer so that at least one of the number of the first and second open cavities align with at least one of the number of MEMS devices to form a sealed cavity around the MEMS; and (iv) electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity through an electrical interconnect. Other embodiments are also described.

Claims

1. A method comprising:

forming a number of first open cavities in a surface of a first substrate and a number of second open cavities in a surface of a second substrate corresponding to the first open cavities;

forming an actuator/sensor layer including a number of Micro-Electromechanical System (MEMS) devices with electrically conductive regions therein;

bonding the first substrate and the second substrate to the actuator/sensor layer so that at least one of the number of the first and second open cavities align with at least one of the number of MEMS devices to form a sealed cavity around the MEMS; and

electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity through an electrical interconnect.

2. The method of claim 1, wherein bonding the first substrate and the second substrate to the actuator/sensor layer comprises one or more of fusion bonding, eutectic bonding, anodic bonding and glass frit bonding to form a hermetically sealed cavity around the MEMS.

3. The method of claim 2, wherein the electrical interconnect comprises a lateral contact structure in contact with the electrically conductive regions of the MEMS device extending from the hermetically sealed cavity between the actuator/sensor layer and the first or second substrate, and wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises exposing a portion of the lateral contact structure.

4. The method of claim 3, wherein bonding the first substrate and the second substrate to the actuator/sensor layer further comprises hermetically sealing the lateral contact structure to the actuator/sensor layer and the first and second substrate.

5. The method of claim 3, wherein the lateral contact is a multilayer contact structure comprising one or more interleaved dielectric layers and conductive layers.

6. The method of claim 2, wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises forming a silicon via through either the first or second substrate to the electrically conductive regions of the MEMS device.

7. The method of claim 2, wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises forming a silicon via through either the first or second substrate to a lateral contact structure in contact with the electrically conductive regions of the MEMS device extending from the hermetically sealed cavity between the actuator/sensor layer and the first or second substrate.

8. The method of claim 2, wherein fusion bonding comprises forming fusion bonds between layers formed on the first substrate, the second substrate and the actuator/sensor layer and comprising one or more of silicon, silicon-dioxide or silicon-nitride.

9. The method of claim 1, further comprising dicing the bonded first substrate, the actuator/sensor layer and second substrate to form individual MEMS packaged with wafer level chip scale packaging (WLCSP).

10. The method of claim 9, further comprising wire bonding the pad to a complementary metal oxide semiconductor (CMOS) die and packaging individual MEMS and CMOS die in a multi-die package.

11. The method of claim 1, wherein at least one of the first or second substrates further includes a complementary metal oxide semiconductor (CMOS) integrated circuit (IC), and wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises electrically connecting the electrically conductive regions of the MEMS device through the CMOS IC.

12. A method comprising:

forming a number of Micro-Electromechanical System (MEMS) devices including electrically conductive regions therein on a surface of a first substrate;

forming a number of first open cavities in the surface of the first substrate underlying the number of MEMS devices;

forming a number of second open cavities in a surface of a second substrate corresponding to the first open cavities; and

bonding the first substrate to the second substrate so that at least one of the number of the first and second open cavities align with at least one of the number of MEMS devices to form a sealed cavity around the MEMS device; and

electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity through an electrical interconnect.

13. The method of claim 12, wherein the electrical interconnect comprises a lateral contact structure in contact with the electrically conductive regions of the MEMS device extending from the hermetically sealed cavity between the first and second substrate, and wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises exposing a portion of the lateral contact structure.

14. The method of claim 12, wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises forming a silicon via through either the first or second substrate to the electrically conductive regions of the MEMS device.

15. The method of claim 12, forming the number of first open cavities in the surface of the first substrate is performed concurrently with forming the number of MEMS devices using an etching process.

16. The method of claim 12, wherein at least one of the first or second substrates further includes a complementary metal oxide semiconductor (CMOS) integrated circuit (IC), and wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises electrically connecting the electrically conductive regions of the MEMS device through the CMOS IC.

17. A method comprising:

etching a number of first open cavities in a surface of a first substrate to form a top cap (TCAP);

forming an actuator/sensor layer including a number of Micro-Electromechanical System (MEMS) devices with electrically conductive regions therein;

bonding the first substrate to the actuator/sensor layer so that at least one of the number of the first open cavities aligns with at least one of the number of MEMS devices;

etching a number of second open cavities in a surface of a second substrate corresponding to the first open cavities to form a bottom cap (BCAP);

bonding the second substrate to the actuator/sensor layer so that at least one of the number of the second open cavities align with at least one of the number of MEMS devices and at least one of the first open cavities to form a sealed cavity around the MEMS device; and

electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity through an electrical interconnect.

18. The method of claim 17, wherein bonding the first substrate and the second substrate to the actuator/sensor layer comprises one or more of fusion bonding, eutectic bonding, anodic bonding and glass frit bonding to form a hermetically sealed cavity around the MEMS.

19. The method of claim 18, wherein the electrical interconnect comprises a lateral contact structure in contact with the electrically conductive regions of the MEMS device extending from the hermetically sealed cavity between the actuator/sensor layer and the first or second substrate, and wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises exposing a portion of the lateral contact structure.

20. The method of claim 18, wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises forming a silicon via through either the first or second substrate to the electrically conductive regions of the MEMS device.

21. The method of claim 17, wherein the actuator/sensor layer comprises single crystalline silicon, and further comprising thinning the actuator/sensor layer to a thickness of 60 μ

m or less prior to bonding the second substrate to the actuator/sensor layer.

22. The method of claim 21, further comprising forming anti-collision extrusions on the actuator layer to prevent stiction and limit the actuator layer travel range.

23. The method of claim 17, wherein at least one of the first or second substrates further includes a complementary metal oxide semiconductor (CMOS) integrated circuit (IC), and wherein electrically connecting the electrically conductive regions of the MEMS device to a pad outside of the sealed cavity comprises electrically connecting the electrically conductive regions of the MEMS device through the CMOS IC.