Mems electrostatic actuator device for rf varactor applications

Patent metadata

Field	Value
Publication number	US-2016176701-A1
Application number	US-201615044016-A
Country	US
Kind code	A1
Filing date	Feb 15, 2016
Priority date	Sep 13, 2011
Publication date	Jun 23, 2016
Grant date	—

Abstract

A MEMs actuator device and method of forming includes arrays of actuator elements. Each actuator element has a moveable top plate and a bottom plate. The top plate includes a central membrane member and a cantilever spring for movement of the central membrane member. The bottom plate consists of two RF signal lines extending under the central membrane member. A MEMs electrostatic actuator device includes a CMOS wafer, a MEMs wafer, and a ball bond assembly. Interconnections are made from a ball bond to an associated through-silicon-via (TSV) that extends through the MEMS wafer. A RF signal path includes a ball bond electrically connected through a TSV and to a horizontal feed bar and from the first horizontal feed bar vertically into each column of the array. A metal bond ring extends between the CMOS wafer and the MEMS wafer. An RF grounding loop is completed from a ground shield overlying the array to the metal bond ring, a TSV and to a ball bond.

First claim

1 . A microelectromechanical system (MEMS) electrostatic actuator device, comprising:
at least one array of actuator elements, wherein each actuator element comprises:
a bottom plate having a first electrode for a first RF signal line and a second electrode for a second RF signal line;
a pedestal;
a top electrode connected to the pedestal, the top electrode having a center membrane portion that extends over the first RF signal line and the second RF signal line; and
a pair of cantilever hinges connected between the top electrode and an anchor on opposite ends of the center membrane portion, the pair of cantilever hinges allowing for movement of the center membrane portion closer to and further from the bottom plate.

2 . The MEMS electrostatic actuator device of claim 1 , wherein the top electrode has a pair of drive members extending from the center membrane on the opposite ends and wherein each actuator element further comprises a pair of drive out electrodes, each one of the pair of drive out electrodes extending under an associated one of the pair of drive members.

3 . The MEMS electrostatic actuator device of claim 1 , wherein each actuator element further includes a pull-in electrode between the first RF signal line and the second RF signal line.

4 . A MEMS electrostatic actuator device, comprising:
a CMOS wafer portion having CMOS circuitry; a MEMS wafer portion bonded to the CMOS wafer portion, the MEMS wafer portion having an array of actuator elements formed thereon and a plurality of through-silicon-vias (TSVs) extending through the MEMS wafer portion; and a plurality of ball bonds formed on a side of the MEMS wafer portion opposite the CMOS wafer portion, wherein an RF signal ball bond of the plurality of ball bonds is electrically connected through an RF signal TSV of the plurality of TSVs and an RF signal horizontal feeder bar to a plurality of RF signal lines, wherein the plurality of RF signal lines include one RF signal line extend through each column of the array of actuator elements.

5 . The MEMS electrostatic actuator device of claim 4 , further comprising a metal bond ring extending between the CMOS wafer portion and the MEMS wafer portion, the metal bond ring surrounding the array of actuator elements.

6 . The MEMS electrostatic actuator device of claim 5 , wherein a GND signal ball bond of the plurality of ball bonds is electrically connected through a GND TSV of the plurality of TSVs and the metal bond ring to the CMOS wafer portion to provide an RF grounding loop.

7 . The MEMS electrostatic actuator device of claim 6 , further comprising a ground shield on a side of the CMOS wafer portion facing the MEMS wafer portion, the ground shield extending over the entire array of actuator elements, wherein the ground shield is electrically connected to the metal bond ring and forms part of the RF grounding loop.

8 . A method of forming an actuator element of an array of actuator elements in a MEMS electrostatic actuator device, comprising the steps of:
forming first and second RF electrodes on the surface of a MEMS wafer; forming a first dielectric layer over the first and second RF electrodes; forming a layer of sacrificial material over the first dielectric layer; forming anchor vias in the layer of sacrificial material; depositing a thinner layer of metal over the sacrificial material including within the anchor vias; forming a second dielectric layer over the layer of metal; patterning and etching the second dielectric layer to remove the second dielectric layer outside of a center membrane area and a hinge area; depositing a thicker layer of metal over the thinner layer of metal outside of the center membrane area and the hinge area and over the second dielectric layer in the center membrane area and the hinge area; forming a masking layer that covers the thicker layer of metal in a drive member area; performing an etch that removes the thicker layer of metal where exposed by the masking layer, wherein the etch continues after removing the thicker layer of metal to remove the thinner layer of metal except where the second dielectric layer protects the thinner layer of metal in the center membrane area and the hinge area; removing the masking layer; removing the second dielectric layer, leaving a metal top plate having a drive member of both the thicker layer of metal and the thinner layer of metal, a center membrane having the thinner layer of metal without the overlying thicker layer of metal, and a hinge portion having the thinner layer of metal without the overlying thicker layer of metal.

Assignees

• Texas Instruments Inc

Inventors

• Gupta Arun
• Mcdonald William C
• Fruehling Adam
• Kmecko Ivan
• Barron Lance
• Agrawal Divyanshu
• Turner Arthur M
• Ehmke John C
• Baker James C

Classifications

• B81B7/008 Primary

  MEMS characterised by an electronic circuit specially adapted for controlling or driving the same (B81B7/0087 takes precedence; arrangements for starting, regulating, braking, or otherwise controlling an actuator H02N; control arrangements or circuits for visual indicators G09G3/00) · CPC title

• B81B2203/0127

  Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function · CPC title

• B81B2207/096

  through the substrate · CPC title

• B81C1/00158

  Diaphragms, membranes (manufacture process for semi-permeable inorganic membranes B01D67/0039) · CPC title

• B81B2201/016

  having a bridge fixed on two ends and connected to one or more dimples · CPC title