Cantilever sensor and fabrication method thereof

• US 7,022,540 B2
• Filed: 05/30/2003
• Issued: 04/04/2006
• Est. Priority Date: 05/30/2002
• Status: Expired due to Fees

• Current Assignee: Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Kim, Hyung Joon, Lee, Jeong Hoon, Kim, Tae Song, Kang, Ji Yoon
• Primary Examiner(s): Gurley, Lynne A.
• Assistant Examiner(s): Stevenson, Andre′
• Application Number:
  US10/448,188
• Publication Number:
  US 20030224551A1
• Time in Patent Office: 1,040 Days
• Field of Search: 438/666, 438/685, 438/761, 438/778, 438/787, 438/791, 438/928, 438/976, 438/977, 438/5, 438/10, 438/48, 438/50, 438/52, 438/57, 438/66, 438/73, 438/98, 438/459, 438/381, 438/238, 438/652, 438/656, 257414-470, 257/528, 257/619, 257/622
• US Class Current: 438/50
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

In a cantilever sensor and a fabrication thereof, by forming piezoelectric films on the same surface, it is possible to sense various information by an electric measuring method. The cantilever sensor comprises a first silicon nitride film formed onto the top surface of a silicon substrate; a silicon oxide film formed onto the first silicon nitride film; a lower electrode formed onto the silicon oxide film; a first piezoelectric film and a second piezoelectric film formed onto the lower electrode, the second piezoelectric film formed out of contact with the first piezoelectric film; an upper electrode respectively formed onto the first and second piezoelectric films; a protecting film formed onto the silicon oxide film, the lower electrode, the first and second piezoelectric films and the upper electrode; a first and a second openings respectively formed on the protecting film on the upper electrode and the protecting film on the lower electrode; a first and a second contact pads respectively formed at the first and second openings; a T-shaped sensing portion formed at the end of a cantilever; a second silicon nitride film formed on the bottom surface of the silicon substrate.

Claims

1. A fabrication method of a cantilever sensor, comprising:

depositing a silicon nitride film respectively onto the top and the bottom surfaces of a silicon substrate;

depositing a silicon oxide film onto the top silicon nitride film;

depositing a lower electrode onto the silicon oxide film;

depositing a first piezoelectric film and a second piezoelectric film onto the lower electrode so as not to contact with each other;

depositing an upper electrode respectively onto the first and second piezoelectric films;

depositing a protecting film onto the silicon oxide film, the lower electrode, the first and second piezoelectric films and the upper electrodes;

forming a first opening on the protecting film of the upper electrode and forming a second opening on the protecting film of the lower electrode;

forming a first and second contact pads respectively on the first and second openings;

removing part of the silicon nitride film on the bottom surface of the substrate;

forming a membrane of predetermined thickness by etching the silicon substrate in which the silicon nitride film is removed; and

forming a cantilever by removing part of the membrane by etching the surrounding portion of the cantilever.

2. The method of claim 1, wherein the lower electrode comprises Pt, and the method further comprising a step for depositing an adhesive layer onto the silicon oxide film before depositing the lower electrode.

3. The method of claim 2, wherein the adhesive layer comprises Ta.

4. The method of claim 1, wherein a thickness of the piezoelectric films is within the range of 0.3˜

2 μ

m.

5. The method of claim 1, further comprising:

forming an Au layer onto the protecting film of the upper electrode and the first contact pad respectively; and

forming an Au layer onto the backside of the cantilever.

6. The method of claim 5, further comprising:

adhering a biomass probe onto the Au layers.

7. The method of claim 1, wherein the cantilever forming step comprises:

forming an analyte binding portion for mounting a sensing material on the end of the cantilever by performing the etching with a distance from the second piezoelectric film.

8. The method of claim 7, wherein the analyte binding portion is shaped into T-type.

9. The method of claim 1, wherein the protecting film comprises at least one of a silicon oxide film, a silicon nitride film and a silicon carbonization film.

10. The method of claim 1, wherein the upper and lower electrodes comprise at least one of platinum and conductive oxide.

11. A fabrication method of a cantilever sensor, comprising:

depositing a silicon nitride film respectively onto the top and the bottom surfaces of a silicon substrate;

removing part of the silicon nitride film on the bottom surface of the substrate;

forming a membrane of a predetermined thickness by etching the silicon substrate in which the silicon nitride film is removed;

depositing a YSZ layer onto the top silicon nitride film;

depositing a lower electrode onto the YSZ layer;

depositing a first piezoelectric film and a second piezoelectric film onto the lower electrode so as not to contact with each other;

depositing an upper electrode respectively onto the first and second piezoelectric films;

depositing a protecting film onto the YSZ layer, the lower electrode, the first and second piezoelectric films and the upper electrode;

forming a first opening on the protecting film of the upper electrode and forming a second opening on the protecting film of the lower electrode; and

forming a first and second contact pads respectively on the first and second openings.

12. The method of claim 11, wherein the lower electrode comprises Pt, and the method further comprises a step for depositing an adhesive layer onto the silicon oxide film before depositing the lower electrode.

13. The method of claim 12, wherein the adhesive layer contains Ta.

14. The method of claim 11, wherein a thickness of the YSZ layer is within the range of 500˜

1000 Å

.

15. The method of claim 11, wherein a thickness of the piezoelectric films is within the range of 2˜

50 μ

m.

16. The method of claim 11, further comprising:

forming an Au layer onto the protecting film of the upper electrode and the first contact pad respectively; and

forming an Au layer onto the backside of the cantilever.

17. The method of claim 16, further comprising:

adhering a biomass probe onto the Au layers.

18. The method of claim 11, wherein the cantilever forming step comprises:

forming an analyte binding portion for mounting a sensing material on the end of the cantilever by performing the etching with a distance from the second piezoelectric film.

19. The method of claim 18, wherein the analyte binding portion is shape into T-type.

20. The method of claim 11, wherein the protecting film comprises at least one of a silicon oxide film, a silicon nitride film and a silicon carbonization film.

21. The method of claim 12, wherein the upper and lower electrodes comprise at least one of platinum and conductive oxide.