Low-temperature bonding of thick-film polysilicon for microelectromechanical system (MEMS)

Hannu Luoto (Corresponding Author), Tommi Suni, Martin Kulawski, Kimmo Henttinen, Hannu Kattelus

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)

Abstract

Polysilicon thick films have been found to be an irreplaceable option in various sensors and other microelectromechanical system (MEMS)-designs. Polysilicon is also a prospective option for replacing single-crystal silicon in customized silicon-on-insulator-substrates. Due to the nature of polysilicon, bonding for MEMS-purposes has so far concentrated on anodic bonding, which has drawbacks for instance in terms of process duration and thermal load. The objective of this work is to develop low-temperature direct bonding for various polysilicon films. Polysilicon films were grown at varying temperatures and pressures with and without boron doping. The films were polished by chemical–mechanical polishing and cleaned. Surface qualities were studied by atomic-force-microscope before bonding. Wafers were then activated with argon plasma and bonded to oxidized silicon, quartz and glass. Bonding quality was evaluated with scanning-acoustic-microscope, the crack-opening-method and HF-etching. Scanning-electron-microscopy was used to investigate film and interface quality. This development has led to a new kind of polishing process, where several microns of polysilicon are removed still leaving surface direct bondable. This is accomplished by a dedicated and effectively planarizing polishing process. Spontaneous bonding took place and good bonding quality was achieved after annealing at 200°C.
Original languageEnglish
Pages (from-to)401-405
Number of pages5
JournalMicrosystem Technologies
Volume12
Issue number5
DOIs
Publication statusPublished - 2006
MoE publication typeA1 Journal article-refereed

Fingerprint

Thick films
Polysilicon
microelectromechanical systems
MEMS
thick films
Silicon
Polishing
polishing
Temperature
silicon
Acoustic microscopes
acoustic microscopes
Quartz
Boron
Argon
argon plasma
Thermal load
systems engineering
Surface properties
Etching

Keywords

  • LT-bonding
  • low temperatures
  • polysilicon
  • poly
  • CMP
  • MEMS

Cite this

Luoto, Hannu ; Suni, Tommi ; Kulawski, Martin ; Henttinen, Kimmo ; Kattelus, Hannu. / Low-temperature bonding of thick-film polysilicon for microelectromechanical system (MEMS). In: Microsystem Technologies. 2006 ; Vol. 12, No. 5. pp. 401-405.
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abstract = "Polysilicon thick films have been found to be an irreplaceable option in various sensors and other microelectromechanical system (MEMS)-designs. Polysilicon is also a prospective option for replacing single-crystal silicon in customized silicon-on-insulator-substrates. Due to the nature of polysilicon, bonding for MEMS-purposes has so far concentrated on anodic bonding, which has drawbacks for instance in terms of process duration and thermal load. The objective of this work is to develop low-temperature direct bonding for various polysilicon films. Polysilicon films were grown at varying temperatures and pressures with and without boron doping. The films were polished by chemical–mechanical polishing and cleaned. Surface qualities were studied by atomic-force-microscope before bonding. Wafers were then activated with argon plasma and bonded to oxidized silicon, quartz and glass. Bonding quality was evaluated with scanning-acoustic-microscope, the crack-opening-method and HF-etching. Scanning-electron-microscopy was used to investigate film and interface quality. This development has led to a new kind of polishing process, where several microns of polysilicon are removed still leaving surface direct bondable. This is accomplished by a dedicated and effectively planarizing polishing process. Spontaneous bonding took place and good bonding quality was achieved after annealing at 200°C.",
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Low-temperature bonding of thick-film polysilicon for microelectromechanical system (MEMS). / Luoto, Hannu (Corresponding Author); Suni, Tommi; Kulawski, Martin; Henttinen, Kimmo; Kattelus, Hannu.

In: Microsystem Technologies, Vol. 12, No. 5, 2006, p. 401-405.

Research output: Contribution to journalArticleScientificpeer-review

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AU - Luoto, Hannu

AU - Suni, Tommi

AU - Kulawski, Martin

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AU - Kattelus, Hannu

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N2 - Polysilicon thick films have been found to be an irreplaceable option in various sensors and other microelectromechanical system (MEMS)-designs. Polysilicon is also a prospective option for replacing single-crystal silicon in customized silicon-on-insulator-substrates. Due to the nature of polysilicon, bonding for MEMS-purposes has so far concentrated on anodic bonding, which has drawbacks for instance in terms of process duration and thermal load. The objective of this work is to develop low-temperature direct bonding for various polysilicon films. Polysilicon films were grown at varying temperatures and pressures with and without boron doping. The films were polished by chemical–mechanical polishing and cleaned. Surface qualities were studied by atomic-force-microscope before bonding. Wafers were then activated with argon plasma and bonded to oxidized silicon, quartz and glass. Bonding quality was evaluated with scanning-acoustic-microscope, the crack-opening-method and HF-etching. Scanning-electron-microscopy was used to investigate film and interface quality. This development has led to a new kind of polishing process, where several microns of polysilicon are removed still leaving surface direct bondable. This is accomplished by a dedicated and effectively planarizing polishing process. Spontaneous bonding took place and good bonding quality was achieved after annealing at 200°C.

AB - Polysilicon thick films have been found to be an irreplaceable option in various sensors and other microelectromechanical system (MEMS)-designs. Polysilicon is also a prospective option for replacing single-crystal silicon in customized silicon-on-insulator-substrates. Due to the nature of polysilicon, bonding for MEMS-purposes has so far concentrated on anodic bonding, which has drawbacks for instance in terms of process duration and thermal load. The objective of this work is to develop low-temperature direct bonding for various polysilicon films. Polysilicon films were grown at varying temperatures and pressures with and without boron doping. The films were polished by chemical–mechanical polishing and cleaned. Surface qualities were studied by atomic-force-microscope before bonding. Wafers were then activated with argon plasma and bonded to oxidized silicon, quartz and glass. Bonding quality was evaluated with scanning-acoustic-microscope, the crack-opening-method and HF-etching. Scanning-electron-microscopy was used to investigate film and interface quality. This development has led to a new kind of polishing process, where several microns of polysilicon are removed still leaving surface direct bondable. This is accomplished by a dedicated and effectively planarizing polishing process. Spontaneous bonding took place and good bonding quality was achieved after annealing at 200°C.

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