Method for fabricating a microscale anemometer

• US 7,451,537 B2
• Filed: 05/18/2005
• Issued: 11/18/2008
• Est. Priority Date: 01/18/2002
• Status: Expired due to Term

• Current Assignee: Board of Trustees of The University of Illinois
• Original Assignee: Board of Trustees of The University of Illinois
• Inventors: Chen, Jack, Liu, Chang
• Primary Examiner(s): Kim; Paul D
• Application Number:
  US11/132,144
• Publication Number:
  US 20050268455A1
• Time in Patent Office: 1,280 Days
• Field of Search: 295/921, 295/93, 295/95, 296/11, 732/041.1, 732/042.2, 732/042.6, 732/042.7, 732/052.5, 738/618.5
• US Class Current: 29/595
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/688 using a particular type of heating, cooling or sensing element G01F1/6847 takes precedence
• CPC Class Codes: G01P 5/12 using variation of resistance of a heated conductor
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/49083 Heater type

Abstract

Method for fabricating a microscale anemometer on a substrate. A sacrificial layer is formed on the substrate, and a metal thin film is patterned to form a sensing element. At least one support for the sensing element is patterned. The sacrificial layer is removed, and the sensing element is lifted away from the substrate by raising the supports, thus creating a clearance between the sensing element and the substrate to allow fluid flow between the sensing element and the substrate. The supports are raised preferably by use of a magnetic field applied to magnetic material patterned on the supports.

Claims

1. A method for fabricating a microscale anemometer, the method comprising the steps of:

forming a sacrificial layer on a substrate;

patterning a metal thin film on the sacrificial layer to form a sensing element;

patterning at least one support for the sensing element, wherein at least a part of the at least one support is provided on the sacrificial layer;

removing the sacrificial layer to release the sensing element and at least the part of the at least one support;

lifting the sensing element away from the substrate to create a clearance between the sensing element and a surface of the substrate; and

patterning a polymer layer substantially overlapping the thin film.

2. The method of claim 1 wherein said step of patterning at least one support includes the step of:

patterning a beam of ductile metal.

3. The method of claim 2 further comprising the step of:

patterning a layer of magnetic material on the at least one support.

4. The method of claim 3 wherein the step of lifting the sensing element comprises the step of:

after removing the sacrificial layer, applying a magnetic field to the layer of magnetic material to raise the at least one support at an angle with respect to the substrate.

5. The method of claim 4 wherein said step of patterning the layer of magnetic material comprises the step of:

for each of the at least one support, defining a space in the layer of magnetic material to create an uncovered portion which defines a bending region.

6. The method of claim 5 wherein said step of lifting the sensing element induces plastic deformation in each of the at least one support at its respective bending regions.

7. The method of claim 6 further comprising the step of:

after the step of removing the sacrificial layer, electroplating the bending region of each of the at least one support with nickel to strengthen the respective bending region.

8. The method of claim 1 wherein the thin film comprises nickel.

9. A method for fabricating a microscale anemometer, the method comprising the steps of:

forming a sacrificial layer on a substrate;

patterning a metal thin film on the sacrificial layer to form a sensing element;

patterning at least one support for the sensing element, wherein at least a part of the at least one support is provided on the sacrificial layer;

removing the sacrificial layer to release the sensing element and at least the part of the at least one support;

lifting the sensing element away from the substrate to create a clearance between the sensing element and a surface of the substrate;

wherein said step of patterning at least one support includes the step of patterning a beam of ductile metal;

further comprising the step of;

patterning a layer of magnetic material on the at least one support;

wherein the step of lifting the sensing element comprises the step of, after removing the sacrificial layer, applying a magnetic field to the layer of magnetic material to raise the at least one support at an angle with respect to the substrate;

wherein said step of patterning the layer of magnetic material comprises the step of, for each of the at least one support, defining a space in the layer of magnetic material to create an uncovered portion which defines a bending region;

wherein said step of lifting the sensing element induces plastic deformation in each of the at least one support at its respective bending regions;

after the step of removing the sacrificial layer, electroplating the bending region of each of the at least one support with nickel to strengthen the respective bending region; and

before said electroplating step, patterning a photoresist on the sensing element.

10. A method for fabricating a microscale anemometer, the method comprising the steps of:

forming a sacrificial layer on a substrate;

patterning a metal thin film on the sacrificial layer to form a sensing element;

patterning at least one support for the sensing element, wherein at least a part of the at least one support is provided on the sacrificial layer;

removing the sacrificial layer to release the sensing element and at least the part of the at least one support; and

lifting the sensing element away from the substrate to create a clearance between the sensing element and a surface of the substrate;

wherein said step of patterning the support comprises patterning a polymer layer onto the sacrificial layer.

11. The method of claim 10 wherein said step of patterning a polymer layer comprises spinning, patterning, and curing the polymer layer onto the sacrificial layer.

12. A method for fabricating a microscale anemometer, the method comprising the steps of:

forming a sacrificial layer on a substrate;

patterning a metal thin film on the sacrificial layer to form a sensing element;

patterning at least one support for the sensing element, wherein at least a part of the at least one support is provided on the sacrificial layer;

removing the sacrificial layer to release the sensing element and at least the part of the at least one support; and

lifting the sensing element away from the substrate to create a clearance between the sensing element and a surface of the substrate,

wherein said step of forming a sacrificial layer comprises the steps of;

patterning a copper layer onto a surface of the substrate;

patterning a chrome layer onto the copper layer; and

patterning a titanium thin film onto the chrome layer.

13. A method for fabricating a microscale anemometer, the method comprising the steps of:

forming a sacrificial layer on a substrate;

patterning a metal thin film on the sacrificial layer to form a sensing element;

patterning at least one support for the sensing element, wherein at least a part of the at least one support is provided on the sacrificial layer;

removing the sacrificial layer to release the sensing element and at least the part of the at least one support;

lifting the sensing element away from the substrate to create a clearance between the sensing element and a surface of the substrate;

patterning a polymer layer substantially overlapping the thin film; and

wherein the thin film comprises at least one layer of nickel and at least one layer of platinum.