Strain mapping of silicon carbon suspended membranes

Highlights: • A novel process has been developed to fabricate suspended Si_1-yC_y membranes. • The process can be extended to silicon membranes as an alternative to SOI wafers. • The strain of the suspended Si_1-yC_y epilayer was measured using a µ -XRD technique. • The tensile strain of the suspended Si_1-yC_y increased by 20% of its original value. • Increased tensile strain is caused by crystalline tilt at edges of the membrane. The alloy silicon carbon (Si_1-yC_y) has various strain engineering applications. It is often implemented as a dopant diffusion barrier and has been identified as a potential buffer layer for cubic silicon carbide (3C-SiC) heteroepitaxy. While suspended membranes formed from thin films of semiconductor (Ge and 3C-SiC) and dielectric (Si₃N₄) materials have been well studied, pseudomorphic, defect-free epilayers under high levels of tensile strain have received little attention. Often, tensile strain is a desired quality of semiconductors and enhancing this property can lead to various benefits of subsequent device applications. The strain state and crystalline tilt of suspended Si_1-yC_y epilayers have been investigated through micro-X-ray diffraction techniques. The in-plane tensile strain of the alloy was found to increase from 0.67% to 0.82%. This strain increase could reduce the C content required to achieve suitable levels of strain in such alloys and further strain enhancement could be externally induced. The source of this strain increase was found to stem from slight tilts at the edges of the membranes, however, the bulk of the suspended films remained flat. The novel process utilised to fabricate suspended Si_1-yC_y thin-films is applicable to many other materials that are typically not resistant to anisotropic Si wet etchants.