MEMS devices with an etch stop layer

• US 8,576,474 B2
• Filed: 01/17/2008
• Issued: 11/05/2013
• Est. Priority Date: 08/14/2004
• Status: Active Grant

• Current Assignee: Ignite USA (Ignite)
• Original Assignee: Fusao Ishii
• Inventors: Ishii, Fusao
• Primary Examiner(s): TRA, TUYEN Q
• Application Number:
  US12/009,389
• Publication Number:
  US 20080218844A1
• Time in Patent Office: 2,119 Days
• Field of Search: 359/237, 359/245, 359/254, 359290-292, 359/212.1, 359/214.1, 359/223.1
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0181 See-saws
• 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 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: B81C 2203/0771 Stacking the electronic processing unit and the micromechanical structure
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

This invention discloses a MEMS device supported on a substrate formed with electric circuit thereon. The MEMS device includes at least an electrode connected to the circuit and at least a movable element that is controlled by the electrode. The MEMS device further includes a conformal protective layer over the electrode and the circuit wherein the protective layer is semiconductor-based material. In a preferred embodiment, the MEMS device is a micromirror and the semiconductor material is one of a group of materials consisting of Si, SiC, Ge, SiGe, SiNi and SiW.

Claims

1. A MEMS device supported on a substrate comprising:

an electronic circuit disposed on said substrate;

at least an electrode connected to said electronic circuit for receiving control signals from said electronic circuit;

at least a mechanical movable reflective element controlled by said control signals received by said electrode;

a combined etch-stop protective structure includes a planar etch stop layer disposed on a top surface of the substrate immediately below the electrode and completely covering said electronic circuit underneath and wherein said combined etch-stop protective structure further includes a conformal etch-stop layer covering said planar etch stop layer and said electrode electrically connected to said circuit disposed below the planar-etch stop layer; and

a hinge extends vertically from a top surface of the electrode and supports the mechanically movable reflective element of top of the hinge.

2. The MEMS device of claim 1 wherein

said conformal etch-stop layer further covering electrode sidewalls.

3. The MEMS device of claim 1 wherein:

said first etch-stop protective layer is composed of a semiconductor material.

4. The MEMS device of claim 1 wherein:

said planar etch-stop protective layer is composed of one of a semiconductor material in a group consists of Si, SiC, Ge, SiGe, SiNi and SiW.

5. The MEMS device of claim 1 wherein:

said planar etch-stop protective layer is composed of a semiconductor material doped as a PN junction with a reverse polarity to a voltage applied to said electrode to prevent an electrical current transmitting from said electrode to said planar etch-stop protective layer.

6. A MEMS device comprising:

a substrate;

an electronic circuit disposed on said substrate;

at least an electrode connected to said electronic circuit for receiving control signals;

at least a mechanical movable reflective element supported on top of a vertical hinge controlled by said control signals received by said electrode; and

a combined etch-stop protective structure includes a planar etch stop layer disposed on a top surface of the substrate immediately below the electrode and completely covering said electronic circuit underneath, wherein said combined etch-stop protective structure further includes a conformal protective layer covering over a top surface and sidewalls of said electrode wherein said etch-stop conformal protective layer is semiconductor material and wherein the vertical hinge extends vertically from a top surface of the electrode disposed above the planar etch stop layer.

7. The MEMS device of claim 6 wherein:

said mechanical movable reflective element comprises a plurality of mirror elements each having a micromirror and said semiconductor material is composed of one of the materials in a group consists of Si, SiC, Ge, SiGe, SiNi and SiW.

8. A micromirror device comprising:

a substrate;

an electronic circuit disposed on said substrate;

at least an electrode connected to said electronic circuit for receiving control signals;

at least a mechanical movable reflective element controlled by said control signals received by said electrode;

a combined etch-stop protective structure includes a planar etch stop layer disposed on a top surface of the substrate immediately below the electrode and completely covering said electronic circuit underneath and wherein said combined etch-stop protective structure further includes a conformal etch-stop layer covering said planar etch stop layer and said electrode; and

a vertical hinge extends vertically from a top surface of the electrode supported on top of the planar etch-stop protective layer wherein said planar etch-stop protective layer has at least a through-hole filled with a via connector for connecting between said electrode disposed on top of the via connector and said electronic circuit completely covered by said via connector and said planar etch stop protective layer made of a semiconductor material.

9. The MEMS device of claim 8 wherein

said vertical hinge supports the mechanical movable reflective element.

10. A MEMS device comprising:

a substrate supporting an electric circuit thereon;

a combined etch-stop protective structure includes a planar etch stop protective layer disposed on a top surface of the substrate completely covering said electronic circuit underneath and wherein said combined etch-stop protective structure further includes a conformal etch-stop layer covering said planar etch stop layer and at least an electrode disposed on top of the planar etch-stop protective layer wherein said planar etch-stop protective layer further comprises at least a doped area on top of the electronic circuit;

the electrode disposed on top of said doped area of said planar etch-stop protective layer for electrically connecting to said electronic circuit disposed below the planar etch-stop protective layer; and

a vertical hinge supports and connected to a moveable reflective element on top of the hinge wherein the hinge extends vertically from a top surface of the electrode.

11. A MEMS device comprising:

a substrate supporting an electric circuit thereon;

a combined etch-stop protective structure includes a planar etch-stop protective layer disposed on a top surface of the substrate completely covering said electronic circuit underneath and wherein said combined etch-stop protective structure further includes a conformal etch-stop layer covering said planar etch stop layer and at least an electrode disposed on top of the planar etch-stop protective layer;

the electrode disposed on top of said planar etch-stop protective layer is electrically connected to said circuit through a via connector penetrated through said planar etch-stop protective layer;

at least a mechanical movable reflective element controlled by electrical signals applied to said electrode;

a vertical hinge supports and connected to said moveable reflective element;

said electronic circuit is completely covered by said planar etch stop protective layer and said via connector; and

said hinge extends vertically from a top surface of one of said electrodes.

12. The MEMS device of claim 11 wherein:

the hinge is connected to the mechanical movable reflective element with a plug.

13. The MEMS device of claim 12 wherein:

said plug is composed of a material same as said movable reflective element.

14. A MEMS device comprising:

a substrate supporting an electric circuit thereon;

at least an electrode connected to and receives control signals from said electric circuit;

at least a mechanical movable reflective element controlled by said control signals received by the electrode;

a combined etch-stop protective structure includes a planar etch stop layer disposed on a top surface of the substrate immediately below the electrode and completely covering said electronic circuit underneath and wherein said combined etch-stop protective structure further includes a conformal etch-stop layer covering said planar etch stop layer and said electrode electrically connected to said circuit disposed below the planar-etch stop layer;

a vertical hinge constituting a partially etched-off vertical wall of a semiconductor layer

a tab extends along a direction substantially perpendicular to said vertical hinge wherein said tab constituting a partially etched-off top horizontal plane etching simultaneously with and composed of a same material as said partially etched-off vertical wall and connected to said vertical hinge for supporting said movable reflective element thereon to function as a mirror; and

the hinge extends vertically from a top surface of said electrodes.

15. A MEMS device comprising:

a substrate supporting an electric circuit thereon;

at least an electrode connected to and receives control signals from said electric circuit;

at least a mechanical movable reflective element controlled by said control signals received by electrode;

a combined etch-stop protective structure includes a planar etch stop layer disposed on a top surface of the substrate immediately below the electrode and completely covering said electronic circuit underneath and wherein said combined etch-stop protective structure further includes a conformal etch-stop layer covering said planar etch stop layer and said electrode electrically connected to said circuit disposed below the planar-etch stop layer;

a vertical hinge constituting a partially etched-off vertical wall of a semiconductor layer;

a foot about perpendicular to said vertical hinge wherein said foot constituting a partially etched-off bottom plane etching simultaneously with and composed of a same material as said partially etched-off vertical wall and connected to a bottom part of said vertical hinge; and

said foot is disposed on top of a top surface of said electrode electrically connected to the circuit covered under the planar etch-stop protective layer.