MEMS Devices and Methods of Forming the Same

• US 20170210618A1
• Filed: 01/21/2016
• Published: 07/27/2017
• Est. Priority Date: 01/21/2016
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Chang, Kai-Fung, Leu, Len-Yi, Tsai, Lien-Yao
• Granted Patent: US 9,926,190 B2
• Time in Patent Office: Days
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2207/09 Packages
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 2203/0109 Bonding an individual cap on the substrate
• CPC Class Codes: B81C 2203/0172 Seals
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: H01L 21/76898 formed through a semiconductor substrate
• CPC Class Codes: H01L 2224/80805 involving forming a eutectic alloy at the bonding interface
• CPC Class Codes: H01L 2224/81805 involving forming a eutectic alloy at the bonding interface
• CPC Class Codes: H01L 23/481 Internal lead connections, e.g. via connections, feedthrough structures

Abstract

A MEMS device and methods of forming are provided. A dielectric layer of a first substrate is patterned to expose conductive features and a bottom layer through the dielectric layer. A first surface of a second substrate is bonded to the dielectric layer and the second substrate is patterned to form a membrane and a movable element. A cap wafer is bonded to the second substrate, where bonding the cap wafer to the second substrate forms a first sealed cavity comprising the movable element and a second sealed cavity that is partially bounded by the membrane. Portions of the cap wafer are removed to expose the second sealed cavity to ambient pressure.

Claims

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

patterning a dielectric layer of a first substrate to expose conductive features and a bottom layer through the dielectric layer, the first substrate comprising the dielectric layer and the bottom layer, the conductive features being disposed in the dielectric layer proximate to the bottom layer;

bonding a first surface of a second substrate to the dielectric layer;

patterning the second substrate to form a membrane and a movable element;

forming a first plurality of metal bonds on a second surface of the second substrate, wherein the second surface is opposite the first surface;

forming a second plurality of metal bonds on a surface of a cap wafer;

bonding the cap wafer to the second substrate by bonding the second plurality of metal bonds to the first plurality of metal bonds, wherein bonding the cap wafer to the second substrate forms a first sealed cavity comprising the movable element and a second sealed cavity that is partially bounded by the membrane; and

removing portions of the cap wafer to expose the second sealed cavity to ambient pressure.

2. The method of claim 1, wherein bonding the cap wafer to the second substrate comprises a eutectic bonding process, wherein a pressure level of the first cavity after the bonding is defined by the eutectic bonding process.

3. The method of claim 1, wherein bonding the second substrate to the first substrate comprises a fusion bonding process.

4. The method of claim 1, further comprising forming a through via that extends from a conductive feature in the dielectric layer through the second substrate.

5. The method of claim 1, further comprising forming a plurality of anti-stiction bumps over one of the conductive features.

6. The method of claim 5, wherein the anti-stiction bumps are positioned underneath the movable element.

7. The method of claim 1, wherein the second substrate comprises low resistance silicon.

8. The method of claim 1, wherein removing portions of the cap wafer to expose the second sealed cavity to ambient pressure comprises forming an opening in the cap wafer to expose the second cavity to an ambient environment.

9. The method of claim 1, wherein the bonding of the first surface of the second substrate to the dielectric layer creates a third sealed cavity, wherein a pressure level of the third cavity after the bonding is defined by the bonding process.

10. A method for forming a micro-electromechanical systems (MEMS) device comprising:

patterning a dielectric layer of a first substrate to create a first cavity and a second cavity, the first substrate comprising the dielectric layer and a bottom layer, a first electrode disposed on the bottom layer in the first cavity and a second electrode disposed on the bottom layer in the second cavity;

patterning the dielectric layer to expose a plurality of conductors, the conductors disposed in the dielectric layer on the bottom layer;

bonding a first surface of a second substrate to the dielectric layer, the bonding sealing the second cavity;

forming a plurality of through vias that extend from the conductors through the second substrate;

patterning the second substrate to create a movable feature, the movable feature positioned over the first electrode;

patterning the second substrate to create a membrane, the membrane positioned over the second electrode;

forming an opening in a third substrate;

bonding the third substrate to the second substrate in a manner that the opening in the third substrate is positioned over the membrane, wherein bonding the third substrate to the second substrate forms a third sealed cavity and a fourth sealed cavity, the third sealed cavity comprising the movable feature and the first cavity, and the fourth cavity being partially bounded by the membrane; and

removing portions of the third substrate to expose the fourth sealed cavity to ambient pressure through the opening in the third substrate.

11. The method of claim 10, wherein a pressure level of the third sealed cavity is defined by a bonding process between the third substrate and the second substrate.

12. The method of claim 10, wherein bonding the first surface of a second substrate to the dielectric layer comprises fusion bonding.

13. The method of claim 10, further comprising forming a plurality of anti-stiction bumps over the first electrode.

14. The method of claim 10, wherein bonding the third substrate to the second substrate comprises a eutectic bonding process between a first plurality of bonds disposed on the second substrate and a second plurality of bonds disposed on the third substrate.

15-20. -20. (canceled)

21. A method for forming a micro-electromechanical systems (MEMS) device comprising:

bonding a first substrate to a second substrate, the bonding of the first substrate to the second substrate creating a first sealed cavity and a second sealed cavity, wherein a first conductive feature is exposed in the first sealed cavity and a second conductive feature is exposed in the second sealed cavity;

depositing and patterning a first mask layer, the first mask layer being patterned to expose a section of the second substrate;

etching the second substrate through the patterned first mask layer to form a membrane overlying the first conductive feature;

depositing and patterning a second mask layer, the second mask layer being patterned to expose a plurality of sections of the second substrate;

etching the second substrate to form a movable element overlying the second conductive feature, wherein the etching of the second substrate unseals the second sealed cavity;

bonding a cap layer to the second substrate to form a third sealed cavity and a fourth sealed cavity, the third sealed cavity comprising the movable element, the fourth cavity being defined in part by the membrane; and

thinning the cap layer to expose an opening in the cap layer, wherein exposing the opening in the cap layer unseals the fourth sealed cavity and exposes the membrane to ambient pressure.

22. The method according to claim 21, further comprising thinning the second substrate after bonding the second substrate to the first substrate.

23. The method according to claim 21, further comprising:

depositing and patterning a third mask layer over the second substrate, the third mask layer being patterned to expose portions of the second substrate;

etching the second substrate and the first substrate through the patterned third mask layer to create a plurality of openings, a conductive feature of the first substrate being exposed by each of the plurality of openings; and

performing a plating process form a plurality of through vias in each of the plurality of openings.

24. The method according to claim 21, wherein the membrane and the movable element are formed in separate etching processes.

25. The method according to claim 21, further comprising forming a plurality of anti-stiction bumps in the cap layer.