Shell flow sensor

• US 20090044620A1
• Filed: 08/13/2007
• Published: 02/19/2009
• Est. Priority Date: 08/13/2007
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Ridley, Jeffrey A., Higashi, Robert E., Lu, Son T.
• Granted Patent: US 7,549,206 B2
• Time in Patent Office: Days
• US Class Current: 73/204.230
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A flow sensor system and a method for fabricating the same. A substrate is provided, comprising a detector wafer upon which a flow sensor is formed. One or more shells can then be configured upon the substrate whose walls form a flow channel. The flow channel is fabricated directly upon the substrate in a manner that allows the flow channel to couple heat transfer directly to the flow sensor in order to eliminate the need for two or more different types of sacrificial layers during the fabrication of the flow sensor upon the substrate and in which the shell(s) is coupled with fluidic measurement to provide for the flow sensor.

Claims

1. A method for fabricating a flow sensor, comprising:

providing a substrate comprising a detector wafer upon which a flow sensor is formed;

configuring upon said substrate, at least one shell whose walls form a flow channel; and

fabricating said flow channel directly upon said substrate in which said flow channel couples heat transfer directly to said flow sensor in order to eliminate a need for two or more different types of sacrificial layers during a fabrication of said flow sensor upon said substrate and in which said at least one shell is coupled with fluidic measurement to provide for said flow sensor.

2. The method of claim 1 further comprising providing in association with said substrate, a low stress dielectric layer in order to increase a pressure range of said flow sensor.

3. The method of claim 1 further comprising providing a thin layer of polyimide capped with SiO₂ and patterned with respect to said substrate to form a plurality of slots at an edge of said flow channel.

4. The method of claim 1 further comprising:

depositing with respect to said substrate a thick layer of polyimide; and

patterning a slope thereon to assist in fabricating said flow channel.

5. The method of claim 1 further comprising:

depositing a thick layer of SiO₂ over a thick layer of polyimide; and

patterning thick layer of SiO₂ to expose a thin layer of polyimide and a plurality of slots at said edge of said flow channel.

6. The method of claim 1 further comprising:

removing polyimide with respect to said substrate using an oxygen plasma etch; and

releasing said at least one shell to form said flow channel; and

thereafter filling a plurality of slots at said edge of said flow channel with a TEOS layer to seal said flow channel.

7. The method of claim 1 further comprising:

patterning a plurality of holes on a backside of said substrate;

thereafter DRIE etching said plurality of holes through said substrate from said backside;

attaching respectively glass capillaries to at least two of said plurality of holes to couple fluid flow into and out of said flow sensor, such that at least one remaining hole among said plurality of holes removes silicon from below said flow sensor, thereby providing thermal isolation for said flow sensor.

8. The method of claim 1 further comprising:

providing in association with said substrate, a low stress dielectric layer in order to increase a pressure range of said flow sensor;

providing a thin layer of polyimide capped with SiO₂ and patterned with respect to said substrate to form a plurality of slots at an edge of said flow channel;

depositing with respect to said substrate a thick layer of polyimide;

patterning a slope thereon to assist in fabricating said flow channel;

depositing a thick layer of SiO₂ over said thick layer of polyimide; and

patterning thick layer of SiO₂ to expose said thin layer of polyimide and a plurality of slots at said edge of said flow channel.

9. The method of claim 8 further comprising:

removing polyimide with respect to said substrate using an oxygen plasma etch; and

releasing said at least one shell to form said flow channel; and

thereafter filling said plurality of slots at said edge of said flow channel with a TEOS layer to seal said flow channel.

10. The method of claim 8 further comprising:

patterning a plurality of holes on a backside of said substrate;

thereafter DRIE etching said plurality of holes through said substrate from said backside;

attaching respectively glass capillaries to at least two of said plurality of holes to couple fluid flow into and out of said flow sensor, such that at least one remaining hole among said plurality of holes removes silicon from below said flow sensor, thereby providing thermal isolation for said flow sensor.

19. The system of claim 1 wherein:

polyimide is removed with respect to said substrate using an oxygen plasma etch; and

said at least one shell is released to form said flow channel; and

said substrate having a plurality of slots at said edge of said flow channel filled with a TEOS layer to seal said flow channel.

20. The system of claim 1 wherein:

said substrate comprises a plurality of holes patterned on a backside of said substrate, said plurality of holes DRIE etched through said substrate from said backside; and

respective glass capillaries are attached to at least two of said plurality of holes to couple fluid flow into and out of said flow sensor, such that at least one remaining hole among said plurality of holes removes silicon from below said flow sensor, thereby providing thermal isolation for said flow sensor.

11. A method for fabricating a flow sensor, comprising:

providing a substrate comprising a detector wafer upon which a flow sensor is formed;

configuring upon said substrate, at least one shell whose walls form a flow channel;

fabricating said flow channel directly upon said substrate in which said flow channel couples heat transfer directly to said flow sensor in order to eliminate a need for two or more different types of sacrificial layers during a fabrication of said flow sensor upon said substrate and in which said at least one shell is coupled with fluidic measurement to provide for said flow sensor;

providing in association with said substrate, a low stress dielectric layer in order to increase a pressure range of said flow sensor;

providing a thin layer of polyimide capped with SiO₂ and patterned with respect to said substrate to form a plurality of slots at an edge of said flow channel;

depositing with respect to said substrate a thick layer of polyimide;

patterning a slope thereon to assist in fabricating said flow channel;

depositing a thick layer of SiO₂ over said thick layer of polyimide; and

patterning thick layer of SiO₂ to expose said thin layer of polyimide and a plurality of slots at said edge of said flow channel.

12. The method of claim 11 further comprising:

removing polyimide with respect to said substrate using an oxygen plasma etch; and

releasing said at least one shell to form said flow channel; and

thereafter filling said plurality of slots at said edge of said flow channel with a TEOS layer to seal said flow channel.

13. The method of claim 11 further comprising:

patterning a plurality of holes on a backside of said substrate;

thereafter DRIE etching said plurality of holes through said substrate from said backside;

attaching respectively glass capillaries to at least two of said plurality of holes to couple fluid flow into and out of said flow sensor, such that at least one remaining hole among said plurality of holes removes silicon from below said flow sensor, thereby providing thermal isolation for said flow sensor.

14. A shell flow sensor system, comprising:

a substrate comprising a detector wafer upon which a flow sensor is formed;

at least one shell configured upon said substrate, wherein said at least one shell comprises walls that form a flow channel of said flow sensor, wherein said flow channel is located directly upon said substrate such that said flow channel couples heat transfer directly to said flow sensor in order to eliminate a need for two or more different types of sacrificial layers during a fabrication of said flow sensor upon said substrate and in which said at least one shell is coupled with fluidic measurement to provide for said flow sensor.

15. The system of claim 14 further comprising a low stress dielectric layer associated with said substrate in order to increase a pressure range of said flow sensor.

16. The system of claim 14 further comprising a thin layer of polyimide capped with SiO₂ and patterned with respect to said substrate to form a plurality of slots at an edge of said flow channel.

17. The system of claim 14 further comprising:

a thick layer of polyimide deposited upon said substrate; and

a slope located thereon to assist in a fabrication of said flow channel.

18. The system of claim 14 further comprising:

a thick layer of SiO₂ deposited over a thick layer of polyimide; and

a thick layer of SiO₂ patterned to expose a thin layer of polyimide and a plurality of slots at said edge of said flow channel.