Intrinsic stress and mechanical properties of hydrogenated silicon carbide produced by plasma-enhanced chemical vapor deposition

Abstract

Hydrogenated SiC films were deposited by radio frequency plasma chemical vapor deposition in a silane–ethylene gas mixture. In the as-deposited condition the films are in compression with absolute values as high as 2×1010 dyn/cm2 (2 GPa). The origin of the stress is attributed to hydrogen incorporation, as evidenced by C–H and Si–H bands observed in infrared transmission measurements of as-deposited films. The hydrogen content was measured directly by 15N nuclear reaction analysis. Values as high as 40% (at.) were observed. Annealing the films in vacuum above 400 °C eliminated the hydrogen-related bands, accompanied by a simultaneous stress reversal from compressive to tensile. It is shown that the stress magnitude and sign can be modulated, depending on the annealing conditions. The ultimate tensile strength and elastic modulus were measured using the bulge test on free-standing membranes. Their values are close to bulk values. Raman spectroscopy and x-ray diffraction show that the films are amorphous. SiC membranes 3 μm thick and 50 mm in diameter were produced with 75% transmission at 632.8 nm, uncorrected for reflection losses.