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Title: Method for forming suspended micromechanical structures

Abstract

A micromachining method is disclosed for forming a suspended micromechanical structure from {111} crystalline silicon. The micromachining method is based on the use of anisotropic dry etching to define lateral features of the structure which are etched down into a {111}-silicon substrate to a first etch depth, thereby forming sidewalls of the structure. The sidewalls are then coated with a protection layer, and the substrate is dry etched to a second etch depth to define a spacing of the structure from the substrate. A selective anisotropic wet etchant (e.g. KOH, EDP, TMAH, NaOH or CsOH) is used to laterally undercut the structure between the first and second etch depths, thereby forming a substantially planar lower surface of the structure along a {111} crystal plane that is parallel to an upper surface of the structure. The lateral extent of undercutting by the wet etchant is controlled and effectively terminated by either timing the etching, by the location of angled {111}-silicon planes or by the locations of preformed etch-stops. This present method allows the formation of suspended micromechanical structures having large vertical dimensions and large masses while allowing for detailed lateral features which can be provided by dry etch definition. Additionally, themore » method of the present invention is compatible with the formation of electronic circuitry on the substrate.

Inventors:
 [1]
  1. Albuquerque, NM
Issue Date:
Research Org.:
Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
OSTI Identifier:
872838
Patent Number(s):
6020272
Assignee:
Sandia Corporation (Albuquerque, NM)
Patent Classifications (CPCs):
B - PERFORMING OPERATIONS B81 - MICROSTRUCTURAL TECHNOLOGY B81C - PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
method; forming; suspended; micromechanical; structures; micromachining; disclosed; structure; 111; crystalline; silicon; based; anisotropic; dry; etching; define; lateral; features; etched; -silicon; substrate; etch; depth; sidewalls; coated; protection; layer; spacing; selective; wet; etchant; koh; edp; tmah; naoh; csoh; laterally; undercut; depths; substantially; planar; surface; crystal; plane; parallel; upper; extent; undercutting; controlled; effectively; terminated; timing; location; angled; planes; locations; preformed; etch-stops; allows; formation; vertical; dimensions; masses; allowing; detailed; provided; definition; additionally; compatible; electronic; circuitry; substantially planar; micromechanical structure; crystal plane; dry etching; electronic circuit; upper surface; silicon substrate; electronic circuitry; crystalline silicon; micromechanical structures; method allows; suspended micromechanical; lateral extent; micromachining method; vertical dimension; method allow; mechanical structure; machining method; /438/216/

Citation Formats

Fleming, James G. Method for forming suspended micromechanical structures. United States: N. p., 2000. Web.
Fleming, James G. Method for forming suspended micromechanical structures. United States.
Fleming, James G. Sat . "Method for forming suspended micromechanical structures". United States. https://www.osti.gov/servlets/purl/872838.
@article{osti_872838,
title = {Method for forming suspended micromechanical structures},
author = {Fleming, James G},
abstractNote = {A micromachining method is disclosed for forming a suspended micromechanical structure from {111} crystalline silicon. The micromachining method is based on the use of anisotropic dry etching to define lateral features of the structure which are etched down into a {111}-silicon substrate to a first etch depth, thereby forming sidewalls of the structure. The sidewalls are then coated with a protection layer, and the substrate is dry etched to a second etch depth to define a spacing of the structure from the substrate. A selective anisotropic wet etchant (e.g. KOH, EDP, TMAH, NaOH or CsOH) is used to laterally undercut the structure between the first and second etch depths, thereby forming a substantially planar lower surface of the structure along a {111} crystal plane that is parallel to an upper surface of the structure. The lateral extent of undercutting by the wet etchant is controlled and effectively terminated by either timing the etching, by the location of angled {111}-silicon planes or by the locations of preformed etch-stops. This present method allows the formation of suspended micromechanical structures having large vertical dimensions and large masses while allowing for detailed lateral features which can be provided by dry etch definition. Additionally, the method of the present invention is compatible with the formation of electronic circuitry on the substrate.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 2000},
month = {Sat Jan 01 00:00:00 EST 2000}
}

Works referenced in this record:

Anisotropic etching of (111)-oriented silicon and applications
conference, August 1998


Free standing single-crystal silicon microstructures
journal, March 1995