Method for making micromechanical structures having at least one lateral, small gap therebetween and micromechanical device produced thereby

• US 6,846,691 B2
• Filed: 07/24/2003
• Issued: 01/25/2005
• Est. Priority Date: 08/24/2000
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Nguyen, Clark T. C., Hsu, Wan-Thai, Clark, John R.
• Primary Examiner(s): TSAI, H JEY
• Application Number:
  US10/625,992
• Publication Number:
  US 20040150057A1
• Time in Patent Office: 551 Days
• Field of Search: 438 48- 53
• US Class Current: 438/48
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81C 1/0019 Flexible or deformable structures not provided for in groups B81C1/00142 - B81C1/00182
• CPC Class Codes: B81C 1/00626 Processes for achieving a desired geometry not provided for in groups B81C1/00563 - B81C1/00619
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 3/007 for the manufacture of electromechanical resonators or networks
• CPC Class Codes: H03H 3/0072 of microelectro-mechanical resonators or networks micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C
• CPC Class Codes: H03H 3/013 for obtaining desired frequency or temperature coefficient H03H3/0076 H03H3/04, H03H3/10 take precedence
• CPC Class Codes: H03H 9/02362 Folded-flexure
• CPC Class Codes: H03H 9/2436 Disk resonators
• CPC Class Codes: H03H 9/46 Filters multiple-port electromechanical filters H03H9/70
• CPC Class Codes: H03H 9/462 Microelectro-mechanical filters
• CPC Class Codes: H03H 9/505 for microelectro-mechanical filters

Abstract

A method and resulting formed device are disclosed wherein the method combines polysilicon surface-micromachining with metal electroplating technology to achieve a capacitively-driven, lateral micromechanical resonator with submicron electrode-to-resonator capacitor gaps. Briefly, surface-micromachining is used to achieve the structural material for a resonator, while conformal metal-plating is used to implement capacitive transducer electrodes. This technology makes possible a variety of new resonator configurations, including disk resonators and lateral clamped-clamped and free-free flexural resonators, all with significant frequency and Q advantages over vertical resonators. In addition, this technology introduces metal electrodes, which greatly reduces the series resistance in electrode interconnects, thus, minimizing Q-loading effects while increasing the power handling ability of micromechanical resonators.

Claims

1. A method for making micromechanical structures having at least one lateral gap therebetween, the method comprising:

providing a substrate;

surface micromachining the substrate to form a capacitively-driven, lateral micromechanical structure having a first vertical sidewall and a sacrificial spacer layer on the first vertical sidewall;

forming a first capacitive transducer electrode on the substrate, the first capacitive transducer electrode including a second vertical sidewall separated from the first vertical sidewall by the spacer layer; and

removing the spacer layer to form a first lateral submicron capacitive gap between the micromechanical structure and the first capacitive transducer electrode to increase electromechanical coupling therebetween.

2. The method as claimed in claim 1 wherein the step of surface micromachining further forms a third vertical sidewall on the micromechanical structure with the sacrificial spacer layer thereon and wherein the method further comprises forming a second capacitive transducer electrode including a fourth vertical sidewall separated from the third vertical sidewall by the spacer layer and wherein the step of removing further forms a second lateral submicron gap between the micromechanical structure and the second capacitive transducer electrode.

3. The method as claimed in claim 1 wherein the micromechanical structure includes a resonator and wherein the first lateral submicron capacitive gap is an electrode-to-resonator capacitive gap.

4. The method as claimed in claim 1 wherein the step of forming includes the step of plating metal on the substrate and wherein the first capacitive transducer electrode is a plated metal electrode.

5. The method as claimed in claim 4 further comprising preventing metal from being plated on the micromechanical structure.

6. The method as claimed in claim 1 wherein the step of forming includes the step of growing the first capacitive transducer electrode via selective epitaxial growth.

7. The method as claimed in claim 1 wherein the step of forming includes the steps of depositing polysilicon and etching the polysilicon to form the first capacitive transducer electrode.