Control of Sidewall Profile in Dry Plasma Etching of Polyimide

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Abstract

Spin-on polyimide is an organic thin film often used as a sacrificial layer for surface micromachining due to its high thermal stability, ease of removal, and compatibility with many materials and processes used in the realization of microelectromechanical systems (MEMS). The incorporation of sloped sidewalls in polyimide for fabricating pedestal structures is crucial in order to provide strong anchors in free-standing MEMS devices, especially in cases having a high aspect ratio and/or where structural materials have limited deposition conformality. This paper demonstrates a reliable reactive ion etching (RIE) methodology for tuning the polyimide sidewall angle, ranging from a vertical sidewall up to an angle of about 25° from the vertical. The key modifications to the process parameter space include changes to the process temperature and chamber pressure. This paper also presents a novel lift-off process, which is based on the use of an interfacial polymer layer to facilitate removal of an overlying silicon oxide hard mask. This procedure allows polyimide sacrificial layers employing a silicon oxide hard mask to be used on samples that have exposed silicon oxide layers elsewhere on the chip that are required to remain intact during hard mask removal. Therefore, this lift-off process is applicable in situations where the silicon oxide hard mask removal cannot be accomplished by wet etching in hydrofluoric acid solutions. [2016-0314]

Original languageEnglish
Article number7888473
Pages (from-to)593-600
Number of pages8
JournalJournal of Microelectromechanical Systems
Volume26
Issue number3
DOIs
Publication statusPublished - 1 Jun 2017

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Plasma etching
Silicon oxides
Polyimides
Masks
MEMS
Surface micromachining
Hydrofluoric acid
Wet etching
Reactive ion etching
Anchors
Aspect ratio
Thermodynamic stability
Tuning
Thin films
Polymers
Temperature

Cite this

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title = "Control of Sidewall Profile in Dry Plasma Etching of Polyimide",
abstract = "Spin-on polyimide is an organic thin film often used as a sacrificial layer for surface micromachining due to its high thermal stability, ease of removal, and compatibility with many materials and processes used in the realization of microelectromechanical systems (MEMS). The incorporation of sloped sidewalls in polyimide for fabricating pedestal structures is crucial in order to provide strong anchors in free-standing MEMS devices, especially in cases having a high aspect ratio and/or where structural materials have limited deposition conformality. This paper demonstrates a reliable reactive ion etching (RIE) methodology for tuning the polyimide sidewall angle, ranging from a vertical sidewall up to an angle of about 25° from the vertical. The key modifications to the process parameter space include changes to the process temperature and chamber pressure. This paper also presents a novel lift-off process, which is based on the use of an interfacial polymer layer to facilitate removal of an overlying silicon oxide hard mask. This procedure allows polyimide sacrificial layers employing a silicon oxide hard mask to be used on samples that have exposed silicon oxide layers elsewhere on the chip that are required to remain intact during hard mask removal. Therefore, this lift-off process is applicable in situations where the silicon oxide hard mask removal cannot be accomplished by wet etching in hydrofluoric acid solutions. [2016-0314]",
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author = "Michal Zawierta and Mariusz Martyniuk and Jeffery, {Roger D.} and Gino Putrino and Adrian Keating and {Dilusha Silva}, {K. K.M.B.} and Lorenzo Faraone",
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T1 - Control of Sidewall Profile in Dry Plasma Etching of Polyimide

AU - Zawierta, Michal

AU - Martyniuk, Mariusz

AU - Jeffery, Roger D.

AU - Putrino, Gino

AU - Keating, Adrian

AU - Dilusha Silva, K. K.M.B.

AU - Faraone, Lorenzo

PY - 2017/6/1

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N2 - Spin-on polyimide is an organic thin film often used as a sacrificial layer for surface micromachining due to its high thermal stability, ease of removal, and compatibility with many materials and processes used in the realization of microelectromechanical systems (MEMS). The incorporation of sloped sidewalls in polyimide for fabricating pedestal structures is crucial in order to provide strong anchors in free-standing MEMS devices, especially in cases having a high aspect ratio and/or where structural materials have limited deposition conformality. This paper demonstrates a reliable reactive ion etching (RIE) methodology for tuning the polyimide sidewall angle, ranging from a vertical sidewall up to an angle of about 25° from the vertical. The key modifications to the process parameter space include changes to the process temperature and chamber pressure. This paper also presents a novel lift-off process, which is based on the use of an interfacial polymer layer to facilitate removal of an overlying silicon oxide hard mask. This procedure allows polyimide sacrificial layers employing a silicon oxide hard mask to be used on samples that have exposed silicon oxide layers elsewhere on the chip that are required to remain intact during hard mask removal. Therefore, this lift-off process is applicable in situations where the silicon oxide hard mask removal cannot be accomplished by wet etching in hydrofluoric acid solutions. [2016-0314]

AB - Spin-on polyimide is an organic thin film often used as a sacrificial layer for surface micromachining due to its high thermal stability, ease of removal, and compatibility with many materials and processes used in the realization of microelectromechanical systems (MEMS). The incorporation of sloped sidewalls in polyimide for fabricating pedestal structures is crucial in order to provide strong anchors in free-standing MEMS devices, especially in cases having a high aspect ratio and/or where structural materials have limited deposition conformality. This paper demonstrates a reliable reactive ion etching (RIE) methodology for tuning the polyimide sidewall angle, ranging from a vertical sidewall up to an angle of about 25° from the vertical. The key modifications to the process parameter space include changes to the process temperature and chamber pressure. This paper also presents a novel lift-off process, which is based on the use of an interfacial polymer layer to facilitate removal of an overlying silicon oxide hard mask. This procedure allows polyimide sacrificial layers employing a silicon oxide hard mask to be used on samples that have exposed silicon oxide layers elsewhere on the chip that are required to remain intact during hard mask removal. Therefore, this lift-off process is applicable in situations where the silicon oxide hard mask removal cannot be accomplished by wet etching in hydrofluoric acid solutions. [2016-0314]

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