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Title: Novel silicon fabrication process for high-aspect-ratio micromachined parts

Abstract

Bulk micromachining generally refers to processes involving wet chemical etching of structures formed out of the silicon substrate and so is limited to fairly large, crude structures. Surface micromachining allows intricate patterning of thin films of polysilicon and other materials to form essentially two-dimensional layered parts (since the thickness of the parts is limited by the thickness of the deposited films). There is a third type of micromachining in which the part is formed by filling a mold which was defined by photolithographic means. Historically micromachining molds have been formed in some sort of photopolymer, be it with x-ray lithography (``LIGA``) or more conventional UV lithography, with the aim of producing piece parts. Recently, however, several groups including ours at Sandia have independently come up with the idea of forming the mold for mechanical parts by etching into the silicon substrate itself. In Sandia`s mold process, the mold is recessed into the substrate using a deep silicon trench etch, lined with a sacrificial or etch-stop layer, and then filled with any of a number of mechanical materials. The completed structures are not ejected from the mold to be used as piece parts rather, the mold is dissolved from around selectedmore » movable segments of the parts, leaving the parts anchored to the substrate. Since the mold is recessed into the substrate, the whole micromechanical structure can be formed, planarized, and integrated with standard silicon microelectronic circuits before the release etch. In addition, unlike surface-micromachined parts, the thickness of the molded parts is limited by the depth of the trench etch (typically 10--50 {mu}m) rather than the thickness of deposited polysilicon (typically 2 {mu}m). The capability of fabricating thicker (and therefore much stiffer and more massive) parts is critical for motion-sensing structures involving large gimballed platforms, proof masses, etc.« less

Authors:
;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
106408
Report Number(s):
SAND-95-1885C; CONF-9510196-1
ON: DE95016761
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: 1995 Society of Photo-Optical Instrumentation Engineers (SPIE) meeting, Austin, TX (United States), 23-24 Oct 1995; Other Information: PBD: [1995]
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; 36 MATERIALS SCIENCE; SILICON; MOLDING; MICROELECTRONIC CIRCUITS; FABRICATION; MACHINING; MATERIALS; ETCHING; MASKING

Citation Formats

Fleming, J.G., and Barron, C.C. Novel silicon fabrication process for high-aspect-ratio micromachined parts. United States: N. p., 1995. Web.
Fleming, J.G., & Barron, C.C. Novel silicon fabrication process for high-aspect-ratio micromachined parts. United States.
Fleming, J.G., and Barron, C.C. Tue . "Novel silicon fabrication process for high-aspect-ratio micromachined parts". United States. https://www.osti.gov/servlets/purl/106408.
@article{osti_106408,
title = {Novel silicon fabrication process for high-aspect-ratio micromachined parts},
author = {Fleming, J.G. and Barron, C.C.},
abstractNote = {Bulk micromachining generally refers to processes involving wet chemical etching of structures formed out of the silicon substrate and so is limited to fairly large, crude structures. Surface micromachining allows intricate patterning of thin films of polysilicon and other materials to form essentially two-dimensional layered parts (since the thickness of the parts is limited by the thickness of the deposited films). There is a third type of micromachining in which the part is formed by filling a mold which was defined by photolithographic means. Historically micromachining molds have been formed in some sort of photopolymer, be it with x-ray lithography (``LIGA``) or more conventional UV lithography, with the aim of producing piece parts. Recently, however, several groups including ours at Sandia have independently come up with the idea of forming the mold for mechanical parts by etching into the silicon substrate itself. In Sandia`s mold process, the mold is recessed into the substrate using a deep silicon trench etch, lined with a sacrificial or etch-stop layer, and then filled with any of a number of mechanical materials. The completed structures are not ejected from the mold to be used as piece parts rather, the mold is dissolved from around selected movable segments of the parts, leaving the parts anchored to the substrate. Since the mold is recessed into the substrate, the whole micromechanical structure can be formed, planarized, and integrated with standard silicon microelectronic circuits before the release etch. In addition, unlike surface-micromachined parts, the thickness of the molded parts is limited by the depth of the trench etch (typically 10--50 {mu}m) rather than the thickness of deposited polysilicon (typically 2 {mu}m). The capability of fabricating thicker (and therefore much stiffer and more massive) parts is critical for motion-sensing structures involving large gimballed platforms, proof masses, etc.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1995},
month = {8}
}

Conference:
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