Selective nitride outgassing process for MEMS cavity pressure control

• US 9,884,758 B2
• Filed: 06/15/2016
• Issued: 02/06/2018
• Est. Priority Date: 01/15/2016
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Cheng, Shyh-Wei, Hsu, Hsi-Cheng, Chen, Hsin-Yu, Chiang, Ji-Hong, Weng, Jui-Chun, Wu, Wei-Ding, Wu, Yu-Jui, Hu, Ching-Hsiang, Chen, Ming-Tsung
• Primary Examiner(s): GREEN, TELLY D
• Application Number:
  US15/182,754
• Publication Number:
  US 20170203962A1
• Time in Patent Office: 601 Days
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2207/012 the micromechanical device and the control or processing electronics being separate parts in the same package
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 7/0038 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81C 1/00285 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• 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 2203/0792 Forming interconnections between the electronic processing unit and the micromechanical structure

Abstract

The present disclosure relates to a MEMS package having an outgassing element configured to adjust a pressure within a hermetically sealed cavity by inducing outgassing of into the cavity, and an associated method. In some embodiments, the method is performed by forming an outgassing element within a passivation layer over a CMOS substrate and forming an outgassing resistive layer to cover the outgassing element. The outgassing resistive layer is removed from over the outgassing element, and the MEMS substrate is bonded to a front side of the CMOS substrate to enclose a first MEMS device within a first cavity and a second MEMS device within a second cavity. After removing the outgassing resistive layer, the outgassing element releases a gas into the second cavity to increase a second pressure of the second cavity to be greater than a first pressure of the first cavity.

Claims

1. A method for manufacturing a micro-electromechanical systems (MEMS) package, the method comprising:

forming an outgassing element within a passivation layer over a CMOS substrate;

forming an outgassing resistive layer to cover the outgassing element;

removing the outgassing resistive layer from over the outgassing element; and

bonding a MEMS substrate to a front side of the CMOS substrate to enclose a first MEMS device within a first cavity and a second MEMS device within a second cavity, wherein after removing the outgassing resistive layer, the outgassing element releases a gas into the second cavity during or after the bonding to increase a second pressure of the second cavity to be greater than a first pressure of the first cavity.

2. The method of claim 1, wherein outgassing resistive layer comprises silicon nitride.

3. The method of claim 1, wherein the outgassing element is formed by depositing and patterning a high density plasma oxide layer within a trench of the passivation layer, wherein the outgassing element is formed to have an upper surface aligned with that of a hard mask overlying the passivation layer.

4. The method of claim 1, further comprising:

forming a plurality of semiconductor devices within a substrate;

forming a plurality of metal interconnect layers including metal wire layers and vias within a dielectric structure comprising a plurality of inter-level dielectric layers over the substrate; and

forming the passivation layer over the plurality of metal interconnect layers and the inter-level dielectric layer.

5. The method of claim 4, further comprising:

performing a second patterning process to the passivation layer and the outgassing resistive layer to form a plurality of bonding trenches through the outgassing resistive layer and the passivation layer, while the outgassing element is protected by the outgassing resistive layer;

wherein the plurality of bonding trenches are formed to expose a top metal layer of the plurality of metal interconnect layers, which is used as a first bonding metal layer for bonding the MEMS substrate and the CMOS substrate.

6. The method of claim 5, wherein a second bonding metal layer is formed on a protrusion extending outward from the MEMS substrate prior to removing the outgassing resistive layer.

7. A method for manufacturing a micro-electromechanical systems (MEMS) package, the method comprising:

forming an outgassing element at a front side of a CMOS substrate;

forming an outgassing resistive layer to cover the outgassing element;

performing a thermal process to the CMOS substrate;

removing the outgassing resistive layer;

bonding a MEMS substrate to the CMOS substrate to enclose a first MEMS device within a first hermetically sealed cavity having a first pressure and a second MEMS device within a second hermetically sealed cavity having a second pressure; and

wherein after removing the outgassing resistive layer, the outgassing element releases a gas into the second cavity during or after the bonding to increase the second pressure of the second cavity.

8. The method of claim 7, wherein the outgassing resistive layer comprises silicon nitride.

9. The method of claim 7, wherein the outgassing element is formed by depositing and patterning a high density plasma oxide layer.

10. The method of claim 7, wherein the CMOS substrate is formed and patterned by a process comprising:

forming a plurality of semiconductor devices within a semiconductor substrate;

forming a plurality of metal interconnect layers including metal wire layers and vias within a dielectric structure comprising a plurality of inter-level dielectric layers over the semiconductor substrate;

forming a passivation layer over the inter-level dielectric layer;

performing a first patterning process to the passivation layer to form a trench within an upper surface of the passivation layer, wherein the trench comprises the outgassing element in the trench;

forming the outgassing resistive layer to cover the outgassing element;

performing the second patterning process to the passivation layer;

performing the thermal process to releases a second gas from the passivation layer; and

removing the outgassing resistive layer.

11. The method of claim 10, wherein the passivation layer is patterned by the first patterning process using a hard mask layer, wherein the outgassing element is formed to have an upper surface aligned with an upper surface of the hard mask layer.

12. The method of claim 10, wherein the second patterning process comprises patterning the passivation layer and the outgassing resistive layer to form a plurality of bonding trenches through the outgassing resistive layer and the passivation layer, while the outgassing element is protected by the outgassing resistive layer.

13. The method of claim 12, wherein the plurality of bonding trenches are formed to expose a top metal layer of the plurality of metal interconnect layers, which is used as a first bonding metal layer for bonding the MEMS substrate and the CMOS substrate.

14. The method of claim 7, wherein the MEMS substrate is formed by a process comprising:

forming a first recess and a second recess from a front side of a capping substrate,

bonding a MEMS layer to the front side of the capping substrate; and

patterning the MEMS layer to form the first MEMS device and the second MEMS device;

wherein the first recess is located at a first position in communication with the first MEMS device and configured as a part of the first cavity, and the second recess is located at a second position in communication with the second MEMS device and configured as a part of the second cavity.

15. A method for manufacturing a micro-electromechanical systems (MEMS) package, the method comprising:

forming a passivation layer over a semiconductor substrate to form a CMOS substrate;

forming an outgassing element within the passivation layer;

bonding a MEMS substrate to the CMOS substrate and enclosing a first MEMS device hermetically sealed within a first cavity having a first pressure and a second MEMS device hermetically sealed within a second cavity having a second pressure; and

wherein the outgassing element is exposed to the second cavity, and is configured to release a gas into the second cavity to increase the second pressure of the second cavity to be greater than the first pressure of the first cavity during or after bonding the MEMS substrate to the CMOS substrate;

wherein the outgassing element is formed by patterning to form a trench into the passivation layer using a hard mask layer, depositing an outgassing layer within the trench and over the passivation layer, and removing the outgassing layer from an upper surface of the hard mask layer to form the outgassing element coplanar with the hard mask layer.

16. The method of claim 15, wherein the outgassing element is formed using a high density plasma oxide.

17. The method of claim 15,

wherein the CMOS substrate and the MEMS substrate are bonded through a top metal layer of the CMOS substrate and a conductive bonding pad of the MEMS substrate;

wherein the top metal layer is formed between the passivation layer and the semiconductor substrate.

18. The method of claim 17, wherein:

wherein the MEMS substrate and the conductive bonding pad are formed to extend through the passivation layer to contact the top metal layer at a bonding interface.

19. The method of claim 15, further comprising:

forming a first recess and a second recess from a front side of a capping substrate; and

bonding the MEMS substrate to the front side of the capping substrate; and

wherein a dielectric liner is formed between the capping substrate and the MEMS substrate and lining surfaces of the first and second recesses.

20. The method of claim 15, prior to the bonding, further comprising:

forming an outgassing resistive layer to cover the outgassing element;

forming bonding trenches through the passivation layer; and

removing the outgassing resistive layer.