Experimental observation and analytical model of the stress gradient inversion in 3C-SiC layers on silicon

Abstract

A detailed study of the static bending of micro-cantilevers has been performed for structures created from thin 3C-SiC films grown on (100) and (111) oriented silicon substrates. The biaxial stress distribution in the direction of the film normal has been evaluated based on analysis of the deformation profiles of clamped-free 3C-SiC beams of various thicknesses. Surprisingly, the obtained results clearly indicate that for as-grown samples of both studied orientations, the absolute value of the intrinsic stress increases from the interface to the surface of the film. We propose a simple analytical model of a relaxation process that explains in a quantitative way this unexpected phenomenon of stress gradient inversion.

Controlling the intrinsic bending of hetero-epitaxial silicon carbide micro-cantilevers

“…Note that this finding is potentially in agreement with the work by Zielinski and coworkers. [39][40][41] They investigated cantilever bending for SiC with thicknesses from 100 nm to above 1 µm and shown constant upward bending in SiC(111) as we report, but only downward bending in SiC(100). As we show here, the upward bending of SiC(100) is restricted to a narrow region, i.e.…”

3C-SiC — From Electronic to MEMS Devices

“…where λ n is a constant depending of the mode (λ 1 = 1.875, λ 2 = 4.694), h and L are, respectively, the thickness and the length of the beam, E the Young's modulus and ρ the cantilever material density (3.2 g cm -3 for SiC). Indeed, as mentioned previously, the use of this method has highlighted the fact that 3C-SiC (100) cantilevers are bended downwards whereas 3C-SiC (111) cantilevers are bended upwards, which is clearly visible on submicron-thick cantilevers, and reveal opposite residual stress effects [68,106].…”

Factors affecting the f × Q product of 3C-SiC microstrings: What is the upper limit for sensitivity?

“…29,37 In addition, the lattice and thermal expansion mismatches between Si and SiC result in the formation of defects and residual stress within the epitaxial SiC film. [37][38][39] We have previously shown that we could achieve f n  Q product of $10 12 (Hz) with large absorption area through the application of cubic silicon carbide (3C-SiC) microstrings with high intrinsic tensile mean stress, which outperforms the highest reported state of the art silicon nitride (a-Si 3 N 4 ) microstrings and offer high promise for chemical sensing. 29 In this work, we explore the factors affecting the R  Q and f n  Q products of the fundamental out-of-plane flexural mode of 3C-SiC microstrings, including the film quality, residual mean stress (r), geometry, clamping condition, and environmental pressure.…”