PZT microdevice

• US 5,914,507 A
• Filed: 10/30/1996
• Issued: 06/22/1999
• Est. Priority Date: 05/11/1994
• Status: Expired due to Fees

• Current Assignee: Regents of the University Minnesota
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Kim, Joon Han, Polla, Dennis L.
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US08/739,808
• Time in Patent Office: 965 Days
• Field of Search: 257/417, 257/254, 257/418, 257/420, 257/753, 73/514.21, 73/514.22, 73/514.23, 73/514.34, 73/514.36, 73/DIG. 1, 73/DIG. 4
• US Class Current: 257/254
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/2047 Membrane type
• CPC Class Codes: Y10S 73/01 Vibration
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

A micromechanical device or microactuator based upon the piezoelectric, pyroelectric, and electrostrictive properties of ferroelectric thin film ceramic materials such as PZT. The microdevice has a device substrate and a deflectable component. The deflectable component is mounted for deflection on the device substrate and has a sensor/actuator. The sensor/actuator has first and second electrodes and a piezoelectric thin film disposed between the first and second electrodes. The thin film is preferably PZT. The sensor/actuator is disposed on a sensor/actuator substrate. The sensor/actuator substrate is formed of a material selected for being resistive to attack by hydrofluoric acid vapor. The invention also relates to a method for fabricating such micromechanical devices or microactuators.

Claims

1. A microdevice comprising:

a device substrate having a trench area;

a deflectable component being mounted for deflection on the device substrate over the trench area, the deflectable component having a sensor/actuator, the sensor/actuator having a first top electrode and a second bottom electrode and a piezoelectric thin film disposed between said first and second electrodes, said thin film being PZT, the sensor/actuator being disposed on a sensor/actuator substrate, the device substrate and sensor/actuator substrate each being formed of a material selected for being resistive to attack by a selected etchant used for etching in the trench area; and

a selectively removable encapsulation layer being deposited on selected portions of the microdevice to substantially isolate the selected portions of the microdevice from exposure to the selected etchant, wherein the selectively removable encapsulation layer can be removed from the selected portions of the microdevice.

2. The microdevice of claim 1 further including at least one adhesion enhancing layer disposed between the sensor/actuator second electrode and the sensor/actuator substrate.

3. The microdevice of claim 2 wherein the adhesion enhancing layer is formed of at least one material selected from a group consisting of:

polycrystalline silicon; and

titanium oxide (TiO₂).

4. The microdevice of claim 1 wherein at least a portion of the deflectable component is disposed in relation to the trench area formed in the device substrate such that said trench area accommodates deflection of the deflectable component therein.

5. The microdevice of claim 4 wherein the deflectable component is a cantilever beam, the cantilever beam having a proximate end and a distal end, the proximate end being operably coupled to the device substrate.

6. The microdevice of claim 1 wherein the sensor/actuator substrate is formed of silicon nitride, the silicon nitride having been post annealed.

7. The microdevice of claim 6 wherein the silicon nitride sensor/actuator substrate is post annealed at 600 to 1200 degrees centigrade for 5 to 180 minutes.

8. The microdevice of claim 7 wherein the silicon nitride sensor/actuator substrate is post annealed at substantially 950 degrees centigrade for substantially 30 minutes.

9. The microdevice of claim 1 wherein the bottom electrode is formed from at least one material selected from a list of materials consisting of:

ruthenium(Ru);

ruthenium oxide (RuO₂);

platinum/ruthenium oxide (RuO₂); and

platinum/ruthenium.

10. The microdevice of claim 9 wherein the encapsulation layer is formed from at least one material selected from a list of materials consisting of:

PECVD silicon nitride;

photoresist;

palylene; and

polyamide.

11. The microdevice of claim 10 wherein the trench area is etched underlying at least a portion of the sensor/actuator.

12. The microdevice of claim 11 wherein a plurality of bores are defined in the encapsulation layer, said bores extending to a margin of the trench area.

13. The microdevice of claim 1 wherein the encapsulation layer is formed of a plurality of layers having a silicon nitride layer and at least one layer of photoresist.