High voltage drive circuitry aligned with MEMS array

• US 20030140698A1
• Filed: 01/21/2003
• Published: 07/31/2003
• Est. Priority Date: 01/26/2001
• Status: Active Grant

• Current Assignee: Lumentum Operations, LLC (Lumentum Holdings Inc.)
• Original Assignee: Michael L. Nagy, Steven L. Garverick
• Inventors: Nagy, Michael L., Garverick, Steven L.
• Granted Patent: US 6,705,165 B2
• Time in Patent Office: Days
• US Class Current: 73/514.18
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0022 using fibre gratings
• CPC Class Codes: H04Q 2011/0024 using space switching
• CPC Class Codes: H04Q 2011/003 using switches based on microelectro-mechanical systems [MEMS]
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0049 Crosstalk reduction; Noise; Power budget

Abstract

Pulse-width modulation (PWM) control and drive circuitry particularly applicable to an array of electrostatic actuators formed in a micro electromechanical system (MEMS), such as used for optical switching. The high-voltage portion may be incorporated in an integrated circuit having drive cells vertically aligned with the MEMS elements. A control cell associated with each actuator includes a register selectively stored with a desired pulse width. A clocked counter distributes its outputs to all control cells. When the counter matches the register, a polarity signal corresponding to a drive clock is latched and controls the voltage applied to the electrostatic cell. The MEMS element may be a tiltable plate supported in its middle by a torsion beam. Complementary binary signals may drive two capacitors formed across the axis of the beam. The register and comparison logic for each cell may be formed by a content addressable memory.

Claims

1. A system including an array of electrically actuated mechanical elements, comprising:

a plurality of electrically controlled actuators arranged in an array and each including at least a first mechanical element with an electrical connection thereto for driving a movement of said first mechanical element relative to a second mechanical element;

a plurality of control circuits associated with respective ones of electrically controlled actuators and connected to respective ones of said electrical connections;

wherein said plurality of control circuits comprise a low-voltage digital circuit section powered by a low-voltage power bus conveying a low voltage; and

wherein each of said control circuits further comprises a high-voltage circuit section powered by a high-voltage power bus conveying a high voltage at least four times said low voltage; and

wherein said plurality of actuators are implemented in one level of a bonded structure and wherein said high-voltage circuits are implemented in at least one first integrated circuit in a second level of said bonded structure, the corresponding actuators and high-voltage circuits being vertically aligned in said bonded structure.

2. The system of claim 1, wherein said low-voltage digital circuit section is implemented in at least one second integrated circuit offset to a side of an area of said high-voltage circuits.

3. The system of claim 1, low-voltage digital circuit section is at least partially implemented as a content addressable memory.

4. The system of claim 1, wherein said electrically controlled actuators are electrostatically controlled actuators each comprising first and second respectively to said first and second mechanical elements.

5. The system of claim 4, wherein all said second electrodes are fixed to a common second mechanical element.

6. The system of claim 4, wherein said high-voltage circuits impose a variable width ternary pulse across said first and second electrodes.

7. An array of electrostatically tiltable plates, comprising:

a plurality of tiltable plates formed as a two-dimensional array having a pitch in first layer of a bonded structure, said first layer comprising silicon and silicon oxide layers, each plate being twistably supported by and having approximately equal first and second areas separated by an axis of a torsion beam;

a second layer of said bonded structure including for each of said plates a first electrode and a second electrode in respective opposition to said first and second areas of said mirror plate, respective variable gap capacitors being formed between said first and second electrodes and said mirror plate;

a plurality of drive cells formed in a first integrated circuit fixed to said second layer and associated respectively with each of said plates, each drive cell supplying to its first electrode a respective high-voltage first drive signal and to its second electrode a respective high-voltage second drive signal, wherein each said drive cell is powered by a high-voltage bus supplying a high voltage and is arranged vertically below its corresponding plate in said bonded structure with said pitch; and

a control section formed in a second integrated circuit fixed to said second layer and powered by a low-voltage bus supplying a low voltage no more than 25% of said high voltage.

8. The array of claim 7, wherein said second integrated circuit is disposed in parallel to said first integrated circuit in an area away from an area enclosing all said electrodes.

9. The array of claim 7, wherein said drive cells deliver complementary, variable-width, ternary pulses between respective ones of said first and second electrodes and said plates.

10. A multi-level MEMS system, comprising:

a first level including a two-dimensional array of a plurality of electrically controlled micro electromechanical system (MEMS) elements having associated electrical actuators;

a second level bonded to said first level including

at least one high-voltage integrated circuit having an array of drive sections disposed below respective ones of said MEMS elements, powered by a high-voltage power bus conveying a high voltage, and producing high-voltage drive signals for said associated electrical actuators, and

at least one low-voltage integrated circuit, powered by a low-voltage power bus conveying a low voltage, and producing respective low-voltage control signals independently controlling respective ones of said drive sections,

wherein said high voltage is at least four times said low voltage.

11. The system of claim 10, wherein said high voltage is at least eight times said low voltage.

12. The system of claim 10, wherein said at least one second integrated circuit is disposed to a side of said MEMS elements.

13. The system of claim 10, further comprising electrical interconnects between said at least one first integrated circuit and said at least one second integrated circuit.

14. The system of claim 13, wherein said electrical interconnects number no more than two for each of said drive sections.

15. The system of claim 10, wherein said electrical actuators are electrostatic actuators.

16. The system of claim 15, wherein each of said MEMS elements comprise a first electrode variably spaced from and second electrode and further comprising a high-voltage drive for all of said second electrodes.

17. The system of claim 10, wherein said MEMS elements comprise tiltable plates.