Circular Surface Acoustic Wave (SAW) Devices, Processes for Making Them, and Methods of Use

• US 20090114798A1
• Filed: 07/02/2008
• Published: 05/07/2009
• Est. Priority Date: 04/20/2007
• Status: Active Grant

• Current Assignee: George Washington University
• Original Assignee: George Washington University
• Inventors: Zaghloul, Mona, Tigli, Onur
• Granted Patent: US 8,018,010 B2
• Time in Patent Office: Days
• US Class Current: 250/200
• CPC Class Codes: G01N 2291/0255 (Bio)chemical reactions, e.g. on biosensors
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/2462 Probes with waveguides, e.g. SAW devices
• CPC Class Codes: G01N 29/326 compensating for temperature variations
• CPC Class Codes: H03B 5/326 the resonator being an acoustic wave device, e.g. SAW or BAW device
• CPC Class Codes: H03H 9/02881 of diffraction of wave beam
• CPC Class Codes: H03H 9/14547 Fan shaped; Tilted; Shifted; Slanted; Tapered; Arched; Stepped finger transducers
• CPC Class Codes: H03H 9/14561 Arched, curved or ring shaped transducers

Abstract

The design, fabrication, post-processing and characterization of a novel circular design SAW (Surface Acoustic Wave) based bio/chemical sensor in CMOS technology is introduced. The sensors are designed in AMI 1.5 μm 2 metal, 2 poly process. A unique maskless post processing sequence is designed and completed. The three post-processing steps are fully compatible with any CMOS technology. This allows any signal control/processing circuitry to be easily integrated on the same chip. ZnO is used as the piezoelectric material for the SAW generation. A thorough characterization and patterning optimization of the sputtered ZnO was carried out. The major novelties that are introduced in the SAW delay line features are: The embedded heater elements for temperature control, compensation and acoustic absorbers that are designed to eliminate edge reflections and minimize triple transit interference. Both of these attributes are designed by using the CMOS layers without disturbing the SAW performance.

Claims

1. An integrated circuit chip having a circular design SAW device as an on-chip component.

2. The chip of claim 1, wherein the chip is a microprocessor.

3. The chip of claim 1, wherein the chip is a programmable integrated circuit.

4. The chip of claim 1, wherein the chip is a microelectromechanical system (MEMS).

5. The chip of claim 1, wherein the chip is a nanoelectromechanical system (NEMS).

6. A circular design SAW device having an absorber structure which comprise CMOS layers of metal1, metal2, and polysilicon.

7. An LC circuit which comprises a circular design SAW device and an amplifier on the same chip.

8. A local oscillator, which comprises the LC circuit of claim 7 connected to a Pierce oscillator.

9. A circular design SAW resonator fabricated using CMOS technology.

10. A process for fabricating a circular design SAW device using standard CMOS technology, comprising:

i) depositing piezoelectric material on top of SAW IDT'"'"'s, and ii) performing a wet-etching of the piezoelectric material to expose the pads for bonding, wherein the SAW IDT'"'"'s are patterned on the dielectic layer during CMOS fabrication and a reactive ion etch releases the IDT'"'"'s from the dielectric layer before the piezoelectric material is deposited.

11. The process of claim 10, wherein the piezoelectric material is ZnO.

12. The process of claim 10, wherein the wet-etching uses a very dilute acid solution.

13. The process of claim 12, wherein the very dilute acid solution is a two acid mixture, wherein each acid of the two acid mixture is selected from the group consisting of acetic acid, hydrochloric acid, and phosphoric acid.

14. The process of claim 11, wherein the CMOS process sequence includes fabricating an absorber structure on the SAW device designed from stacking CMOS layers of metal1, metal2 and polysilicon to achieve a surface higher than the IDT level for attenuating or reflecting the acoustic waves.

15. A circular design SAW device made by the process of any of claims 10-14.

16. A circular design SAW based integrated circuit based detection system comprising:

(i) a circular design sensor having at least one sensing element for selectively combining with target molecules, said sensor generating a signal when combined with said target molecules responsive to incident electromagnetic radiation applied to said sensor/target combination; and

(ii) an integrated circuit microchip to which the sensor is affixed, the integrated circuit microchip including;

a plurality of detection channels operatively associated with said sensing elements, each of said detection channels including a detector for detecting electromagnetic signals, said detectors selected from the group consisting of photodiodes and phototransistors.

17. The integrated circuit of claim 16, wherein the sensor comprises a chemical receptor, a bioreceptor, a polymer, a biopolymer, a molecular imprint polymer, a biomimetic, an antibody, an enzyme, a cell receptor, a molecular print assay, or a nucleic acid.

18. The system of claim 16, where detection of the target utilizes phase shift detection within the SAW device.

19. The system of claim 16, where detection of the target utilizes frequency shift detection within the SAW device.

20. The system of claim 16 or 17, wherein the system is implemented in a hand held unit.