Microelectromechanical structure and process of making same

• US 5,717,631 A
• Filed: 07/25/1995
• Issued: 02/10/1998
• Est. Priority Date: 07/21/1995
• Status: Expired due to Term

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Carley, L. Richard, Fedder, Gary K., Reed, Michael L., Santhanam, Suresh
• Primary Examiner(s): Nguyen, Viet Q.
• Application Number:
  US08/507,676
• Time in Patent Office: 931 Days
• Field of Search: 437/190, 437/69, 437/72, 437/80, 437/225, 437/228, 156/643, 29/25.35, 369/126, 369/127, 365/174
• US Class Current: 365/174
• CPC Class Codes: B81B 2201/07 Data storage devices, static or dynamic memories
• CPC Class Codes: B81B 2201/12 STM or AFM microtips
• CPC Class Codes: B81B 2203/0361 Tips, pillars
• CPC Class Codes: B81C 1/0015 Cantilevers switches using MEMS H01H1/0036; electrostatic relays using micromechanics H01H59/0009; microelectro-mechanical resonators H03H9/02244
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G11B 2005/0002 Special dispositions or recording techniques
• CPC Class Codes: G11B 9/14 using microscopic probe means , i.e. recording or reproducing by means directly associated with the tip of a microscopic electrical probe as used in Scanning Tunneling Microscopy [STM] or Atomic Force Microscopy [AFM] for inducing physical or electrical perturbations in a recording medium; Record carriers or media specially adapted for such transducing of information marking using electrical current B41M5/20; measuring roughness or irregularity of surfaces G01B7/34; details of scanning-probe microscopes G01Q
• CPC Class Codes: G11B 9/1409 Heads
• CPC Class Codes: G11B 9/1418 Disposition or mounting of heads or record carriers G11B17/00 and G11B19/00 take precedence
• CPC Class Codes: G11B 9/1445 switching at least one head in operating function; Controlling the relative spacing to keep the head operative, e.g. for allowing a tunnel current flow
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: Y10S 977/861 Scanning tunneling probe
• CPC Class Codes: Y10S 977/881 Microscopy or spectroscopy, e.g. sem, tem
• CPC Class Codes: Y10S 977/888 Shaping or removal of materials, e.g. etching
• CPC Class Codes: Y10S 977/89 Deposition of materials, e.g. coating, cvd, or ald

Abstract

A microelectromechanical device is comprised of a cantilevered beam positioned above, and free to move relative to, a substrate. The beam may carry a plurality of conductors which are insulated from one another. One or more tips is positioned on the beam with each tip being in electrical contact with one of the conductors. A memory device may be constructed by providing an array of such cantilevered beams proximate to a layer of media. Devices for positioning the beam in x and y directions perpendicular to each other and parallel to the layer of media and in a z direction perpendicular to the media are provided. A control circuit generates control signals input to the positioning devices for positioning the tips according to x, y, and z coordinates. A read/write circuit which is in electrical communication with the conductors of the beam, provide signals to the tips to cause the tips to write those signals to the layer of media in a write mode and to read previously written signals sensed by the tips in a read mode. A fabrication method is also disclosed.

Claims

1. A process for fabricating a microelectromechanical device from a substrate carrying at least one layer of a non-erodible material laid out to form at least a portion of said microelectromechanical device and at least one layer of an erodible material, comprising the steps of:

using the layer of non-erodible material as a mask and anisotropically etching any of said layer of erodible material not occluded by said layer of non-erodible material; and

gas etching said substrate to form a pit under at least a beam portion of said microelectromechanical device to free said beam portion of said microelectromechanical device from said substrate.

2. The process for fabricating a microelectromechanical device of claim 1 wherein said non-erodible material is a metal conductor and said erodible material is an insulator.

3. The process for fabricating a microelectromechanical device of claim 2 wherein said conductor is aluminum and said insulator is an oxide, and wherein said step of anisotropic etching includes the step of ion etching in an oxygen rich atmosphere.

4. The process for fabricating a microelectromechanical device of claim 3 wherein said step of gas etching includes the step of gas etching with a fluoride gas.

5. The process for fabricating a microelectromechanical device of claim 4 wherein said fluoride gas is CF₄ NO₂.

9. The process of claim 1 wherein said microelectromechanical device includes a positioning portion, and wherein said step of gas etching includes the step of gas etching for a period to time sufficient to etch a pit under said beam portion but insufficient to form a pit under said positioning portion.

6. A process for fabricating a microelectromechanical device from a substrate carrying at least one layer of a non-erodible conductive aluminum mask material laid out to form at least a portion of said microelectromechanical device and at least one layer of an erodible insulative oxide material, comprising the steps of:

anisotropic etching any of said layer of erodible material not occluded by said layer of non-erodible material using an ion etch in an oxygen rich atmosphere; and

gas etching said substrate to form a pit under at least a beam portion of said microelectromechanical device to free said beam portion of said microelectromechanical device from the substrate.

7. The process of fabricating a microelectromechanical device of claim 6 wherein said step of gas etching includes the step of gas etching with a fluoride gas.

8. The process for fabricating a microelectromechanical device of claim 7 wherein said fluoride gas is CF₄ No₂.