FLOW SENSORS HAVING NANOSCALE COATING FOR CORROSION RESISTANCE

• US 20110146398A1
• Filed: 12/18/2009
• Published: 06/23/2011
• Est. Priority Date: 12/18/2009
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: SPELDRICH, JAMIE, BECK, SCOTT E., QASIMI, MOHAMMED A. JAVVAD, BEY, PAUL P.
• Granted Patent: US 8,161,811 B2
• Time in Patent Office: Days
• US Class Current: 73/204.27
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48599 Principal constituent of the connecting portion of the wire connector being Gold (Au)
• CPC Class Codes: H01L 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 23/3142 Sealing arrangements between parts, e.g. adhesion promotors
• CPC Class Codes: H01L 23/3192 Multilayer coating
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/06 of a plurality of bonding areas
• CPC Class Codes: H01L 24/45 of an individual wire connector
• 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 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 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 Silicon [Si]
• CPC Class Codes: H01L 2924/01022 Titanium [Ti]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/0105 Tin [Sn]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/04941 : TiN
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/1461 : MEMS
• CPC Class Codes: Y10T 29/49002 : Electrical device making

Abstract

A corrosion resistant flow sensor apparatus includes a flow sensor including a micromachinable substrate mounted on a package substrate that includes electrically conductive traces and substrate bond pads. The flow sensor includes a MEMS sensing structure for sensing a mass flow parameter and sensor bond pads coupled to the sensing structure. The sensor bond pads include a top metal layer on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall. Bond wires couple the sensor bond pads to the substrate bond pads. A housing including sides and a top portion is around the flow sensor and includes a flow channel having an inlet and an outlet. A multi-layer corrosion protection coating includes a nm scale adhesion layer and a self assembled monolayer (SAM) is on the adhesion layer. The protection coating covers the sensor bond pads including the metal diffusion barrier layer sidewall.

Claims

1. A corrosion resistant flow sensor apparatus, comprising:

a package substrate having a package substrate surface including a plurality of substrate bond pads thereon;

at least one flow sensor die comprising silicon mounted on said package substrate surface including a sensing structure for sensing a mass flow parameter from a medium flowing over said sensing structure and a plurality of sensor bond pads coupled to said sensing structure for providing a sensing signal, wherein said sensor bond pads comprise a top metal layer disposed on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall;

bond wires for coupling said plurality of sensor bond pads to said substrate bond pads;

a housing comprising plastic formed around said sensor die and said sensor bond wires comprising sides and a top portion, wherein said housing includes a flow channel having an inlet for providing said medium flowing over said sensing structure and an outlet;

a multi-layer corrosion protection coating comprising a nanometer-scale adhesion layer and a self assembled monolayer (SAM) that is hydrophobic or hydrophilic disposed on said adhesion layer, wherein said multi-layer corrosion protection coats said sensor bond pads including over said metal diffusion barrier layer sidewall and coats said sensor bond wires, and

a signal processing circuit on said substrate surface that receives and processes said sensing signal from said sensing structure.

2. The flow sensor apparatus of claim 1, wherein said package substrate comprises a printed circuit board (PCB).

3. The flow sensor apparatus of claim 1, wherein said SAM comprises a hydrophobic layer.

4. The flow sensor apparatus of claim 1, wherein said SAM has a thickness from 2 Angstroms to 10 nanometers.

5. The flow sensor apparatus of claim 3, wherein said flow sensor comprises an airflow sensor, and said sensing structure comprises a MEMS micro-bridge.

6. The flow sensor apparatus of claim 1, wherein a multi-layer corrosion protection coating is a dielectric coating.

7. A corrosion resistant flow sensor apparatus, comprising:

a package substrate having a package substrate surface including a plurality of electrically conductive traces and substrate bond pads thereon;

at least one flow sensor comprising a micromachinable substrate mounted on said package substrate surface including a sensing structure for sensing a mass flow parameter from a medium flowing over said sensing structure and a plurality of sensor bond pads coupled to said sensing structure for providing a sensing signal, wherein said sensor bond pads comprise a top metal layer disposed on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall;

bond wires coupling said plurality of sensor bond pads to said substrate bond pads;

a housing formed around said flow sensor and said sensor bond wires comprising sides and a top portion, said housing including a flow channel having an inlet for providing said medium flowing over said sensing structure and an outlet, and

a multi-layer corrosion protection coating comprising a nanometer-scale adhesion layer and a self assembled monolayer (SAM) that is hydrophobic or hydrophilic disposed on said adhesion layer, wherein said multi-layer corrosion protection coating covers sensor bond pads including over said metal diffusion barrier layer sidewall and covers said bond wires.

8. The flow sensor apparatus of claim 7, wherein said package substrate comprises a PCB and said micromachinable substrate comprises silicon.

9. The flow sensor apparatus of claim 7, wherein said micromachinable substrate comprises glass or quartz.

10. The flow sensor apparatus of claim 7, further comprising a signal processing circuit on said package substrate surface coupled to said sensor bond pads by said plurality of electrically conductive traces to receive and process said sensing signal from said sensing structure.

11. The flow sensor apparatus of claim 7, wherein said top metal layer comprises gold and said metal diffusion barrier layer comprises a refractory metal.

12. The flow sensor apparatus of claim 7, wherein said housing comprises a plastic.

13. The flow sensor apparatus of claim 7, wherein said flow sensor comprises an airflow sensor, and said sensing structure comprises a MEMS micro-bridge.

14. The flow sensor apparatus of claim 7, wherein said flow sensor comprises a membrane-based sensor.

15. The flow sensor apparatus of claim 7, wherein said multi-layer corrosion protection coating further comprises a fluid diffusion layer different from said adhesion layer between said adhesion layer and said SAM.

16. The flow sensor apparatus of claim 15, wherein said adhesion layer comprises alumina, titania or silica.

17. The flow sensor apparatus of claim 16, wherein said fluid diffusion barrier layer is a nanometer thick layer and comprises a silicon oxide, silicon carbide, silicon nitride, or a silicon oxynitride layer.

18. The flow sensor apparatus of claim 7, wherein SAM has a thickness from 2 Angstroms to 10 nanometers.

19. The flow sensor apparatus of claim 7, wherein said metal diffusion barrier layer comprises Ti, TiN, TiW, Ta, TaN, Zr, ZrN, V, Pt, Cr₂O₃, Ta₂O₅ or combinations thereof.

20. The flow sensor apparatus of claim 7, wherein said multi-layer corrosion protection coating is a dielectric coating.

21. A method of forming corrosion resistant fluid sensor apparatus, comprising:

mounting a flow sensor comprising a micromachinable substrate on a package substrate surface, said flow sensor including a sensing structure for sensing a mass flow parameter from a medium flowing over said sensing structure and a plurality of sensor bond pads coupled to said sensing structure for providing a sensing signal, wherein said sensor bond pads comprise a top metal layer disposed on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall;

wire bonding to couple said flow sensor bond pads to bond pads on said package substrate surface;

forming a housing comprising plastic around the flow sensor, wherein the housing includes at least one flow tube providing an inlet and an outlet;

blanket deposition of a multi-layer corrosion protection coating at a temperature <

150°

C. on said flow sensor, wherein said blanket deposition comprises;

depositing a nm scale adhesion layer;

depositing a self assembled monolayer (SAM) that is hydrophobic or hydrophilic on said adhesion layer, wherein said multi-layer corrosion protection coats said sensor bond pads including over said metal diffusion barrier layer sidewall and coats said sensor bond wires.

22. The method of claim 21, wherein said blanket deposition comprises a vapor phase deposition process.

23. The method of claim 21, wherein said adhesion layer comprises alumina, titania or silica.

24. The method of claim 21, wherein said multi-layer corrosion protection coating is a dielectric coating.

25. The method of claim 21, wherein said flow sensor comprises a sensor die comprising silicon.