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Open AccessArticle

Investigation of the Young’s Modulus and the Residual Stress of 4H-SiC Circular Membranes on 4H-SiC Substrates

1
GREMAN UMR-CNRS 7347, Université de Tours, INSA Centre Val de Loire, 37071 Tours, France
2
Paul Scherrer Institute, ODRA/116, 5232 Villigen, Switzerland
3
STMicroelectronics, Stradale Primosole, 50, 95121 Catania, Italy
*
Author to whom correspondence should be addressed.
Micromachines 2019, 10(12), 801; https://doi.org/10.3390/mi10120801
Received: 1 October 2019 / Revised: 7 November 2019 / Accepted: 19 November 2019 / Published: 21 November 2019
(This article belongs to the Special Issue SiC based Miniaturized Devices)
The stress state is a crucial parameter for the design of innovative microelectromechanical systems based on silicon carbide (SiC) material. Hence, mechanical properties of such structures highly depend on the fabrication process. Despite significant progresses in thin-film growth and fabrication process, monitoring the strain of the suspended SiC thin-films is still challenging. However, 3C-SiC membranes on silicon (Si) substrates have been demonstrated, but due to the low quality of the SiC/Si heteroepitaxy, high levels of residual strains were always observed. In order to achieve promising self-standing films with low residual stress, an alternative micromachining technique based on electrochemical etching of high quality homoepitaxy 4H-SiC layers was evaluated. This work is dedicated to the determination of their mechanical properties and more specifically, to the characterization of a 4H-SiC freestanding film with a circular shape. An inverse problem method was implemented, where experimental results obtained from bulge test are fitted with theoretical static load-deflection curves of the stressed membrane. To assess data validity, the dynamic behavior of the membrane was also investigated: Experimentally, by means of laser Doppler vibrometry (LDV) and theoretically, by means of finite element computations. The two methods provided very similar results since one obtained a Young’s modulus of 410 GPa and a residual stress value of 41 MPa from bulge test against 400 GPa and 30 MPa for the LDV analysis. The determined Young’s modulus is in good agreement with literature values. Moreover, residual stress values demonstrate that the fabrication of low-stressed SiC films is achievable thanks to the micromachining process developed.
Keywords: 4H-SiC; bulk micromachining; electrochemical etching; circular membrane; bulge test; vibrometry; mechanical properties; Young’s modulus; residual stress; FEM 4H-SiC; bulk micromachining; electrochemical etching; circular membrane; bulge test; vibrometry; mechanical properties; Young’s modulus; residual stress; FEM
MDPI and ACS Style

Ben Messaoud, J.; Michaud, J.-F.; Certon, D.; Camarda, M.; Piluso, N.; Colin, L.; Barcella, F.; Alquier, D. Investigation of the Young’s Modulus and the Residual Stress of 4H-SiC Circular Membranes on 4H-SiC Substrates. Micromachines 2019, 10, 801.

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