CMOS-MEMS Integrated Flow for Making a Pressure Sensitive Transducer

• US 20150060954A1
• Filed: 08/29/2013
• Published: 03/05/2015
• Est. Priority Date: 08/29/2013
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Cheng, Chun-Wen, Liang, Kai-Chih, Chu, Chia-Hua
• Granted Patent: US 9,254,997 B2
• Time in Patent Office: Days
• US Class Current: 257/254
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81C 1/00238 Joining a substrate with an electronic processing unit and a substrate with a micromechanical structure

Abstract

A sensor is made up of two substrates which are adhered together. A first substrate includes a pressure-sensitive micro-electrical-mechanical (MEMS) structure and a conductive contact structure that protrudes outwardly beyond a first face of the first substrate. A second substrate includes a complementary metal oxide semiconductor (CMOS) device and a receiving structure made up of sidewalls that meet a conductive surface which is recessed from a first face of the second substrate. A conductive bonding material physically adheres the conductive contact structure to the conductive surface and electrically couples the MEMS structure to the CMOS device.

Claims

1. A sensor, comprising:

a first substrate including a conductive contact structure which protrudes outwardly beyond a face of the first substrate and which is electrically coupled to a pressure-sensitive micro-electrical-mechanical (MEMS) structure on the first substrate;

a second substrate including;

a receiving structure having a conductive surface which is recessed from a first face of the second substrate by sidewalls that bound the conductive surface, wherein the conductive surface is electrically coupled to a complementary metal oxide semiconductor (CMOS) device on the second substrate; and

a conductive bonding material to physically adhere the conductive contact structure to the conductive surface and to electrically couple the MEMS structure to the CMOS device.

2. The sensor of claim 1, wherein the sensor includes a capacitive sensing element comprising:

a conductive membrane, which acts as a first capacitive plate, arranged on the first substrate; and

a metal layer, which acts as a second capacitive plate, arranged on the second substrate.

3. The sensor of claim 2, wherein the first substrate comprises:

a conductive cantilever support structure which physically supports and is electrically coupled to the conductive membrane; and

a conductive anchor structure arranged to physically support the conductive cantilever structure and to electrically couple the conductive cantilever to the conductive contact structure.

4. The sensor of claim 3, wherein the second substrate includes an aperture which is aligned to the conductive membrane when the first and second substrates are physically adhered to one another.

5. The sensor of claim 4, where the second substrate further comprises:

a CMOS circuit configured to supply a predetermined charge to the conductive membrane and to monitor how a voltage changes between the conductive membrane and metal layer as a function of the predetermined charge.

6. The sensor of claim 2, wherein the second substrate comprises an analog-to-digital converter to digitize an electrical signal related to a position of the conductive membrane in time.

7. The sensor of claim 6, wherein the second substrate comprises an analog or digital acoustic filter.

8. The sensor of claim 1, wherein the receiving structure comprises:

a hydro-fluoric (HF) acid barrier layer that extends laterally along a surface of the second substrate and which extends vertically along the sidewall from the surface of the second substrate to the recessed conductive surface.

9. The sensor of claim 1, wherein the conductive contact comprises:

a polysilicon body that protrudes from the surface of the first substrate, wherein conductive vias couple the polysilicon body to the anchor structure; and

a germanium pad coupling the polysilicon body to the conductive surface of the second substrate.

10. A method, comprising:

processing a first substrate to form a pressure-sensitive micro-electrical-mechanical (MEMS) structure, wherein a first face of the first substrate includes a substantially planar dielectric region with a conductive contact structure which extends through the substantially planar dielectric region and which protrudes outwardly beyond the substantially planar dielectric region;

processing a second substrate having opposing faces to form a complementary metal oxide semiconductor (CMOS) device, wherein a first of the opposing faces for the second substrate includes a conductive receiving structure that is recessed relative to the first face for the second substrate; and

bonding the first face of the first substrate to the first face of the second substrate such that the conductive contact structure of the first substrate is received within the conductive receiving structure.

11. The method of claim 10, wherein prior to the bonding, a conductive membrane of the MEMS structure is fastened to the dielectric region.

12. The method of claim 11, further comprising:

after the bonding has been performed, carrying out an etch to free the conductive membrane from the dielectric region so the conductive membrane moves or vibrates based on an impingent pressure wave.

13. The method of claim 10, wherein, prior to bonding the first face of the first substrate to the first face of the second substrate, the conductive contact structure on first substrate is formed by:

forming a polysilicon layer over vias which extend through the substantially planar dielectric region, wherein the vias are coupled to a polysilicon anchor structure underlying the substantially planar dielectric region;

forming a germanium pad over the polysilicon layer; and

patterning the polysilicon layer and the germanium pad to form the conductive contact structure.

14. The method of claim 13, wherein forming the receiving structure comprises peforming an etch to form a recess in a dielectric layer on the second substrate, and wherein the patterned polysilicon layer and germanium pad are received in the receiving structure after bonding has been performed.

15. The method of claim 10, wherein forming the pressure-sensitive MEMS structure comprises:

forming a conductive membrane in the first substrate and covering the conductive membrane by a protective layer prior to bonding the first and second substrates; and

after bonding the first and second substrates, performing an etch to release the conductive membrane from the protective layer.

16. The method of claim 15, wherein processing the second substrate further comprises:

forming vapor hydro-fluoric (vHF) barrier prior to bonding the first and second substrate, and

wherein performing the etch to release the conductive membrane from the protective layer comprises immersing the first and second substrates in vHF.

17. A sensor, comprising:

a first substrate including;

a conductive contact structure which protrudes outwardly beyond a face of the first substrate and which is electrically coupled to a conductive membrane, which acts as a first capacitive plate, on the first substrate;

a second substrate including;

a receiving structure having a conductive surface which is recessed from a first face of the second substrate by sidewalls and which is electrically coupled to a metal layer, which acts as a second capacitive plate, on the second substrate; and

a circuit on the second substrate and configured to supply a predetermined charge to the conductive membrane and to monitor how a voltage changes between the conductive membrane and the metal layer as a function of the predetermined charge.

18. The sensor of claim 17, further comprising:

a conductive eutectic bonding material to physically adhere the conductive contact structure to the conductive surface of the receiving structure and to electrically couple the conductive membrane to the circuit.

19. The sensor of claim 18, wherein the receiving structure comprises:

a polysilicon body that protrudes from the surface of the first substrate, wherein conductive vias couple the polysilicon body to the anchor structure; and

a germanium pad coupling the polysilicon body to the conductive surface of the second substrate.

20. The sensor of claim 19, wherein the second substrate includes an aperture which is aligned to the conductive membrane when the first and second substrates are physically adhered to one another, and wherein the polysilicon body and germanium pad are received in the receiving structure.