Micromechanical actuator with asymmetrically shaped electrodes

• US 7,629,725 B1
• Filed: 04/01/2005
• Issued: 12/08/2009
• Est. Priority Date: 11/08/2002
• Status: Expired due to Fees

• Current Assignee: Iris Ao, Inc.
• Original Assignee: Iris Ao, Inc.
• Inventors: Knollenberg, Clifford F., Helmbrecht, Michael Albert
• Primary Examiner(s): Tamai; Karl I
• Application Number:
  US11/096,395
• Time in Patent Office: 1,712 Days
• Field of Search: 310/309, 359223-226, 359/290, 359/291, 359/872
• US Class Current: 310/309
• CPC Class Codes: B81B 2203/0163 Spring holders
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 2203/056 Rotation in a plane parallel to the substrate
• CPC Class Codes: B81B 3/0037 For increasing stroke, i.e. achieve large displacement of actuated parts
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/0825 the reflecting element being a flexible sheet or membrane, e.g. for varying the focus flexible mirrors for cosmetic use A45D42/24
• CPC Class Codes: H01H 2059/0081 with a tapered air-gap between fixed and movable electrodes
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A micromachined actuator including a body or platform mounted to a suspension system anchored to a substrate. In one embodiment, the suspension system is comprised of a set of one or more spring flexures connecting the actuator body to the substrate with strain relief provided via connecting torsional elements. In another embodiment, the suspension system includes a first set of one or more spring flexures each with one end anchored to a largely rigid intermediate frame and the other end attached to the body. A second set of one or more flexures is attached between the intermediate frame and the substrate. A third actuator embodiment maximizes force electrode area to minimize voltage required for electrostatic actuation. A fourth embodiment provides electrical interconnect to an actuator or an actuator array using polysilicon with silicon nitride isolation. Actuators may be fabricated by combining the key features of all four embodiments or actuators may be fabricated using any combination of two or three of the embodiments.

Claims

1. An actuator system, comprising:

a microelectromechanical (MEMS) structure comprising;

an actuator body connected with a suspension system; and

the suspension system connected with a substrate, the suspension system being configured to elevate the actuator body above the substrate upon actuation in a motion substantially perpendicular to the substrate, the suspension system comprising a set of one or more flexures and a set of one or more torsional elements, wherein each flexure connects the actuator body with the substrate and each torsional element connects a corresponding flexure with the actuator body and provides strain relief between the corresponding flexure and the actuator body, each torsional element having a length comprising the distance from the corresponding flexure to the actuator body, the length being greater than the width of the torsional element, and

the substrate connected with the MEMS structure, the substrate comprising;

a set of one or more asymmetrically shaped electrodes for inducing actuation of the suspension system when a voltage is applied to the set of electrodes; and

an interconnect layer comprising a set of one or more interconnects coupled to the set of electrodes, the set of interconnects being coupled to a control circuit for controlling voltages applied to the set of electrodes via the set of interconnects, wherein;

the suspension system and the set of electrodes are entirely located underneath the actuator body;

the set of electrodes are not located underneath the suspension system;

the entire suspension system is located underneath approximately the edge of the actuator body;

each electrode is located underneath the center of the actuator body and extends past the suspension system to a location underneath the edge of the actuator body; and

the interconnect layer is beneath the set of electrodes.

2. The actuator system of claim 1 wherein an electrode in the set of electrodes has a skewed non-diamond shape.

3. The actuator system of claim 1,

wherein each electrode in the set of electrodes is configured to induce actuation of a corresponding flexure when a voltage is applied to the electrode.

4. The actuator system of claim 3, wherein each torsional element has an angle of twist per unit moment (θ

/Nm) of 7.00E+06 or greater.

5. The actuator system of claim 3, wherein each torsional element has a length dimension that extends from the corresponding flexure to the actuator body, the length dimension having a value equal to or greater than 5 μ

m.

6. The actuator system of claim 3, wherein each torsional element has a width dimension that extends perpendicular to the length dimension and substantially parallel to the substrate, the width dimension having a value equal to or greater than 2 μ

m and less than 10 μ

m.

7. The actuator system of claim 3, wherein a torsional element comprises a torsional attachment or a torsional spring.

8. The actuator system of claim 3, wherein a torsional element is shaped in a serpentine form.

9. The actuator system of claim 3, wherein:

the suspension system further comprises a set of one or more anchor points, wherein each anchor point connects a corresponding flexure to the substrate and has an angle of twist per unit moment value substantially equal to a first value; and

each torsional element has an angle of twist per unit moment value substantially equal to a second value, wherein the second value is greater than the first value.

10. The actuator system of claim 1, wherein the actuator body is a platform, actuator segment, or mirror segment.