Piezoelectric actuator of an ink-jet printhead and method for forming the same
View Patent ↗A piezoelectric actuator for providing a driving force to a pressure chamber of an ink-jet printhead for ejecting ink by deforming a vibration plate, the vibration plate forming an upper wall of the pressure chamber, the piezoelectric actuator including a lower electrode formed on the vibration plate, a piezoelectric film having either: (a) peripheral portions, the piezoelectric film formed on the lower electrode at a position that corresponds to the pressure chamber and having a space between the peripheral portions and the lower electrode, or (b) a lateral surface, the piezoelectric film formed on the lower electrode at a position that corresponds to the pressure chamber, the lateral surface of the piezoelectric film substantially forming a right angle with respect to a top surface of the lower electrode, and an upper electrode formed on the piezoelectric film for applying a voltage to the piezoelectric film.
1. A piezoelectric actuator for providing a driving force to a pressure chamber of an ink-jet printhead for ejecting ink by deforming a vibration plate, the vibration plate forming an upper wall of the pressure chamber, the piezoelectric actuator comprising:
a lower electrode formed on the vibration plate;
a piezoelectric film having protruding portions, the piezoelectric film being formed on the lower electrode at a position that corresponds to the pressure chamber, the protruding portions protruding from upper sidewall portions of the piezoelectric film such that an upper portion of the piezoelectric film has a wider width than a lower portion of the piezoelectric film; and
an upper electrode formed on the piezoelectric film for applying a voltage to the piezoelectric film, wherein a space exists between a lower surface of the protruding portions and an upper surface of the lower electrode.
2. The piezoelectric actuator as claimed in claim 1 , wherein the width of the lower portion of the piezoelectric film contacting the lower electrode is about 70% to about 90% of a width of the pressure chamber.
3. The piezoelectric actuator as claimed in claim 1 , wherein the lower electrode comprises a two-layer structure in which a titanium (Ti) layer and a platinum (Pt) layer are sequentially stacked.
4. The piezoelectric actuator as claimed in claim 3 , wherein the titanium (Ti) layer has a thickness of about 400 Å and the platinum (Pt) layer has a thickness of about 5000 Å.
5. The piezoelectric actuator as claimed in claim 1 , wherein the vibration plate is made of silicon.
6. The piezoelectric actuator as claimed in claim 5 , further comprising a silicon oxide layer between the vibration plate and the lower electrode.
7. The piezoelectric actuator as claimed in claim 1 , wherein the space has a thickness of about 2 to about 8 μm along a direction substantially perpendicular to a plane along which the lower electrode extends.
8. The piezoelectric actuator as claimed in claim 1 , wherein the piezoelectric film has a substantially T-shaped cross-sectional shape.
9. The piezoelectric actuator as claimed in claim 1 , wherein the piezoelectric film includes lead zirconate titanate.
10. The piezoelectric actuator as claimed in claim 1 , wherein the protruding portions of the piezoelectric film extend away from the upper sidewall portions of the piezoelectric film along a direction substantially parallel to a direction along which the lower electrode extends.
11. The piezoelectric actuator as claimed in claim 1 , wherein a lower sidewall portion of the piezoelectric actuator extends substantially perpendicular to a direction along which the lower electrode extends.
12. The piezoelectric actuator as claimed in claim 11 , wherein the lower sidewall portion and the lower surface of a corresponding one of the protruding portions extend substantially perpendicular to each other.
13. The piezoelectric actuator as claimed in claim 1 , wherein:
the lower portion of the piezoelectric film has a substantially uniform thickness, and
a substantially central portion of the upper portion of the piezoelectric film has a larger thickness than peripheral portions of the upper portion of the piezoelectric film.
14. The piezoelectric actuator as claimed in claim 13 , wherein an upper surface of the piezoelectric film is curved.
15. A piezoelectric actuator for providing a driving force to a pressure chamber of an ink-jet printhead for ejecting ink by deforming a vibration plate, the vibration plate forming an upper wall of the pressure chamber, the piezoelectric actuator comprising:
a lower electrode formed on the vibration plate;
a piezoelectric film having protruding portions, the piezoelectric film being formed on the lower electrode at a position that corresponds to the pressure chamber, the protruding portions protruding from upper sidewall portions of the piezoelectric film such that an upper portion of the piezoelectric film has a wider width than a lower portion of the piezoelectric film; and
an upper electrode formed on the piezoelectric film for applying a voltage to the piezoelectric film, wherein the protruding portions of the piezoelectric film extend away from the upper sidewall portions of the piezoelectric film along a direction substantially parallel to a direction along which the lower electrode extends.