Multiple stage MEMS release for isolation of similar materials

• US 20070138582A1
• Filed: 12/20/2005
• Published: 06/21/2007
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Jia, Nancy, Ryu, Kee, Nystrom, Peter
• Granted Patent: US 7,838,321 B2
• Time in Patent Office: Days
• US Class Current: 257/416
• CPC Class Codes: B41J 2/14 Structure thereof only for on-demand ink jet heads
• CPC Class Codes: B41J 2/16 Production of nozzles
• CPC Class Codes: B41J 2/1626 etching
• CPC Class Codes: B41J 2/1639 sacrificial molding
• CPC Class Codes: B41J 2002/043 Electrostatic transducer
• CPC Class Codes: B81B 2201/052 Ink-jet print cartridges
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: B81C 2201/0133 Wet etching
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal

Abstract

This describes a starting structure and method for forming a micro-mechanical device. These devices have several uses in both government and commercial applications. The starting structure can be sold or supplied to others who will then make a final product, or it can be used directly to make a final product. An appropriate use of this starting structure is to make deformable devices useful in an inkjet printing device.

Claims

1. A starting structure useful in manufacturing a micro-mechanical device, said structure having layers in an operative arrangement each layer sequentially stacked one on the other, said layers comprising a first sacrificial layer, a second sacrificial layer, and desired underlying layer(s), said first sacrificial layer having similar material etching properties with said desired underlying layer, said second sacrificial layer having widely separated material etching properties from said desired underlying layer, wherein said second sacrificial layer being substantially resistant to a material used to remove said first sacrificial layer and wherein said second sacrificial layer is enabled to protect said underlying layer as said first sacrificial layer is removed by said etching.

2. The starting structure of claim 1 comprising a base wafer as part of said desired underlying layer(s).

3. The starting structure of claim 1 wherein said micro-electro-mechanical device is a deformable device.

4. The starting structure of claim 1 wherein said underlying layer comprises a base wafer, a dielectric layer(s) and a conductor layer.

5. The starting structure of claim 1 comprising a deformable membrane.

6. The starting structure of claim 1 wherein at least one of said sacrificial layers provides a space or a gap in said micro-mechanical device.

7. The starting structure of claim 1 wherein said starting structure is used to produce as said micro-mechanical device useful as an electrostatic membrane that is deformable upon the application of an actuation potential.

8. A starting structure capable of forming a micro-mechanical device, said starting structure comprising in an operative arrangement, a deformable upper layer, a desired underlying layer(s), a first sacrificial layer, and a second sacrificial layer, said first sacrificial layer having similar material etching properties in an etching environment with said desired underlying layer, said second sacrificial layer having widely different material etching properties to said desired underlying layer(s), said desired underlying layer comprising a silicon base wafer, a conductor, and a dielectric material, said second sacrificial layer enabled to protect said desired underlying layer while being resistant to a material used to remove said first sacrificial layer.

9. The starting structure of claim 8 wherein said first sacrificial layer comprises a silicon oxide, more specifically, a PSG oxide.

10. The starting structure of claim 8 wherein said second sacrificial layer is dissolvable and comprises Si₃N₄.

11. The starting structure of claim 8 wherein said micro-mechanical device is a device having an upper deformable layer, said layer selected from the group consisting of deformable membranes, movable plates, beams and mixtures thereof.

12. The starting structure of claim 8 wherein removal of at least one of said sacrificial layers provides a space or gap which assists in a deformability of said upper layer of said micro-mechanical device.

13. The starting structure of claim 8 formulated by starting with a Silicon base wafer, and superimposing over said wafer at least a Silicon conductor, at least one Silicon based dielectric material, a first sacrificial layer, a second sacrificial layer and a deformable Polysilicon layer.

14. A method for the formation of a micro-mechanical device useful in an inkjet printing device, said method comprising providing a starting structure comprising in an operative arrangement a deformable upper Polysilicon layer, an underlying layer(s), a first sacrificial Oxide layer and a second sacrificial Nitride layer, providing an etching process whereby said first sacrificial layer is removed by a Hydrofluoric Acid (HF) initial etch release thereby leaving said second Nitride sacrificial layer and said underlying layer(s) in tact, and subsequently removing said second Nitride sacrificial layer by a hot Phosphoric Acid etch, to provide a deformable micro-mechanical device having an air gap(s) therein left by the removal of said first and second sacrificial layers.

15. The method of claim 14 wherein said first sacrificial layer comprises SiO₂.

16. The method of claim 14 wherein said second sacrificial layer comprises Si₃N₄.

17. The method of claim 14 wherein said underlying layer(s) comprises a Silicon base layer.

18. The method of claim 14 wherein removal of at least one of said sacrificial layers provides a space or gap which assists in the formation of said deformable upper Polysilicon layer.

19. The method of claim 14 wherein said resulting micro-mechanical device comprises an electrically isolated electrode which is enabled to attract a movable Polysilicon layer or membrane upon application of an actuation potential.

20. The method of claim 14 wherein said deformable upper Polysilicon layer is provided adjacent to said air gaps, and wherein a release hole is provided in said micro-mechanical device to permit passage of release etchants to remove said first and second sacrificial layers.