Mapping the strain and tilt of a suspended 3C-SiC membrane through micro X-ray diffraction

• Partial relaxation has been observed across a suspended 3C-SiC membrane using micro X-ray diffraction techniques.
• Poor crystalline quality of the 3C-SiC epilayer induces large uncertainties on the positions of Bragg peaks and hence strain.
• Crystalline tilt has been measured across a 3C-SiC membrane by mapping the Si peak position.
• A high resolution area map of membrane corner revealed layer distortions at the edge of 3C-SiC membrane suspended region.
• Results suggest that chemical etching causes edge localised shear strain within the 3C-SiC membrane.

Micro X-ray diffraction (μ-XRD) has been used to map the strain profile of a suspended crystalline cubic Silicon Carbide (3C-SiC) square membrane. While the presence of crystal defects in the 3C-SiC epilayer induces significant errors on the position of the 3C-SiC Bragg peaks, relaxation from residual tensile strain can be observed and directly quantified from the XRD measurements. The advantage of μ-XRD over other strain mapping techniques is that the tilt of the crystalline layers can be measured simultaneously with the lattice parameters. Significant tilt variations have been observed at the corner of the 3C-SiC membrane, implying that the undercut from chemical etching induces distortions in the crystal structure. These distortions are likely to be the cause of the increase in strain commonly observed at the edges of suspended structures using the micro-Raman shift strain mapping technique.

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