Micro-electro-mechanical fluid ejector and method of operating same

• US 6,357,865 B1
• Filed: 10/12/1999
• Issued: 03/19/2002
• Est. Priority Date: 10/15/1998
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Kubby, Joel A., Chen, Jingkuang, Pan, Feixia
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Nguyen, Lamson D.
• Application Number:
  US09/416,329
• Time in Patent Office: 889 Days
• Field of Search: 347/20, 347/54, 347/68, 347/70, 347/71, 347/72, 347/9, 347/10, 347/11
• US Class Current: 347/68
• CPC Class Codes: B41J 2/14 Structure thereof only for on-demand ink jet heads
• CPC Class Codes: B41J 2/14314 Structure of ink jet print heads with electrostatically actuated membrane
• CPC Class Codes: B41J 2/16 Production of nozzles
• CPC Class Codes: B41J 2/1628 dry etching
• CPC Class Codes: B41J 2/1629 wet etching
• CPC Class Codes: B41J 2/1631 photolithography
• CPC Class Codes: B41J 2/1639 sacrificial molding
• CPC Class Codes: B41J 2/1642 thin film formation by CVD [chemical vapor deposition]
• CPC Class Codes: B41J 2002/041 Electromagnetic transducer

Abstract

A micro-electromechanical fluid ejector that is easily fabricated in a standard polysilicon surface micromachining process is disclosed, which can be batch fabricated at low cost using existing external foundry capabilities. In addition, the surface micromachining process has proven to be compatible with integrated microelectronics, allowing for the monolithic integration of the actuator with addressing electronics. A voltage drive mode and a charge drive mode for the power source actuating a deformable membrane is also disclosed.

Claims

1. A micro-electromechanical fluid ejector, comprising:

a single semiconductor substrate having an insulating layer thereon;

a conductor on the insulating layer;

a polysilicon membrane that is formed by surface micromachining through the deposition and patterning of a polysilicon layer, the membrane comprising a membrane top and membrane sides, the membrane sides supporting the membrane above the conductor and the insulating layer, the membrane being conductive;

an actuator chamber formed between the membrane and the insulating layer;

a nozzle plate surrounding the membrane, the nozzle plate having a nozzle top and nozzle sides;

a pressure chamber formed between the nozzle plate and the membrane, wherein fluid is stored;

a nozzle formed in the nozzle plate for ejecting fluid;

a power source connected between the conductor and the membrane, the power source when activated supplying sufficient force to deflect the membrane top towards the conductor, thereby increasing the supply of fluid in pressure chamber;

wherein the conductor, membrane and actuator chamber are formed by surface micromachining techniques.

2. A micro-electromechanical fluid ejector, as claimed in claim 1, further comprising:

a nipple on the bottom side of the top of the membrane, the nipple arranged to land on an insulating film to thereby prevent the top of the membrane from touching the conductor.

3. A micro-electromechanical fluid ejector, as claimed in claim 2, wherein the membrane top is circular in shape.

4. A micro-electromechanical fluid ejector, as claimed in claim 1, wherein the membrane is made of polysilicon.

5. micro-electromechanical fluid ejector, as claimed in claim 4, wherein the fluid comprises ink.

6. A method of operating a micro-electromechanical fluid ejector, comprising:

locating a polysilicon membrane that is formed by surface micromachining through the deposition and patterning of a polysilicon layer, the membrane having a membrane top and membrane sides enclosing an actuator chamber, the membrane being formed on an insulating layer which has been deposited on a single semiconductor substrate;

locating a conductor on the insulating layer within the actuator chamber;

surrounding the membrane with a nozzle plate having a nozzle formed therein;

supplying fluid to the nozzle plate; and

applying a power source between the membrane and the conductor to form an electrostatic force which causes the membrane to deflect towards the conductor;

wherein the conductor, membrane and actuator chamber are formed by surface micromachining techniques.

7. A method of operating a micro-electromechanical fluid ejector, as claimed in claim 6, further comprising:

locating a nipple on the bottom of the top of membrane, the nipple arranged to land on an insulating film to thereby prevent the top of the membrane from touching the conductor.

8. A method of operating a micro-electromechanical fluid ejector, as claimed in claim 6, wherein the power source is a voltage source.

9. A method of operating a micro-electromechanical fluid ejector, as claimed in claim 8, wherein the electrostatic force causes the membrane to deflect from a relaxed position to a maximum pull-in position which is the maximum displacement of the membrane, resulting in a repeatable volume reduction of the actuator chamber.

10. A method of operating a micro-electromechanical fluid ejector, as claimed in claim 6, wherein the power source is a current source.

11. A method of operating a micro-electromechanical fluid ejector, as claimed in claim 10, wherein the current source is variable.

12. A method of operating a micro-electromechanical fluid ejector as claimed in claim 11, wherein the electrostatic forces causes the membrane to deflect from a relaxed position to a variable pull-in position, the variable pull-in position being controlled by the amount of charge supplied by the current source.