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

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.