TY - JOUR
T1 - Method for Keyhole-Free High-Aspect-Ratio Trench Refill by LPCVD
AU - Veltkamp, Henk-Willem
AU - Janssens, Yves L.
AU - de Boer, Meint J.
AU - Zhao, Yiyuan
AU - Wiegerink, Remco J.
AU - Tas, Niels R.
AU - Lötters, Joost C.
N1 - Funding Information:
This work is part of the research programs “Integrated Wobbe Index Meter” under project number 13952 and “PiezoMEMS for Flow+” under project number 15026, which are co-financed by the Netherlands Organization for Scientific Research (NWO), Bronkhorst High-Tech B.V., and Krohne Ltd.
Publisher Copyright:
© 2022 by the authors.
Financial transaction number:
2500040275
PY - 2022/11/4
Y1 - 2022/11/4
N2 - In micro-machined micro-electromechanical systems (MEMS), refilled high-aspect-ratio trench structures are used for different applications. However, these trenches often show keyholes, which have an impact on the performance of the devices. In this paper, explanations are given on keyhole formation, and a method is presented for etching positively-tapered high-aspect ratio trenches with an optimised trench entrance to prevent keyhole formation. The trench etch is performed by a two-step Bosch-based process, in which the cycle time, platen power, and process pressure during the etch step of the Bosch cycle are studied to adjust the dimensions of the scallops and their location in the trench sidewall, which control the taper of the trench sidewall. It is demonstrated that the amount of chemical flux, being adjusted by the cycle time of the etch step in the Bosch cycle, relates the scallop height to the sidewall profile angle. The required positive tapering of 88° to 89° for a keyhole-free structure after a trench refill by low-pressure chemical vapour deposition is achieved by lowering the time of the etch step.
AB - In micro-machined micro-electromechanical systems (MEMS), refilled high-aspect-ratio trench structures are used for different applications. However, these trenches often show keyholes, which have an impact on the performance of the devices. In this paper, explanations are given on keyhole formation, and a method is presented for etching positively-tapered high-aspect ratio trenches with an optimised trench entrance to prevent keyhole formation. The trench etch is performed by a two-step Bosch-based process, in which the cycle time, platen power, and process pressure during the etch step of the Bosch cycle are studied to adjust the dimensions of the scallops and their location in the trench sidewall, which control the taper of the trench sidewall. It is demonstrated that the amount of chemical flux, being adjusted by the cycle time of the etch step in the Bosch cycle, relates the scallop height to the sidewall profile angle. The required positive tapering of 88° to 89° for a keyhole-free structure after a trench refill by low-pressure chemical vapour deposition is achieved by lowering the time of the etch step.
KW - High-aspect-ratio trenches
KW - Keyhole-free refilling by LPCVD
KW - Trench isolation/insulation
UR - http://www.scopus.com/inward/record.url?scp=85141796620&partnerID=8YFLogxK
U2 - 10.3390/mi13111908
DO - 10.3390/mi13111908
M3 - Article
AN - SCOPUS:85141796620
SN - 2072-666X
VL - 13
JO - Micromachines
JF - Micromachines
IS - 11
M1 - 1908
ER -