STRESS BEHAVIOR OF MAGNETRON-SPUTTERED SIC THIN-FILMS ON THERMAL CYCLING AND ANNEALING

The stresses in silicon carbide (SiC) films prepared by r.f. magnetron sputtering have been studied by using a bending beam technique. The as-deposited SiC films exhibit a relatively high compressive stress, which decreases with the increase in film thickness. These films are mostly amorphous. When subjected to thermal cycling, the films exhibit significant stress relaxation above 320-degrees-C. When annealed above 500-degrees-C, the stress changes from compressive to tensile. The tensile stress continuously increases with the increase in the annealing temperature. From the results of X-ray diffraction and Raman spectroscopy, below 600-degrees-C, the change in the film stress could be attributed to the annihilation of voids or vacancies in the film. Above 500-degrees-C, the stress change can be attributed to crystallization. Above 800-degrees-C, it can be attributed to the phase transitions of the amorphous carbons to polycrystalline graphite and the amorphous SiC to polycrystalline beta-Si C, and the growth of the crystalline silicon. The film exhibits microcracks after being annealed at 800-degrees-C. The cracks became wider when annealing is carried out above 800-degrees-C. The SiC films so prepared could sustain a compressive stress as high as 12 x 10(8) N m-2 and a tensile stress around 6 x 10(8) N m-2.