SPECIMEN SIZE EFFECT OF TENSILE-STRENGTH OF SURFACE-MICROMACHINED POLYCRYSTALLINE SILICON THIN-FILMS

A new tensile tester using an electrostatic-force grip was developed t o evaluate the tensile strength and the reliability of thin-film mater ials, The tester was constructed in a scanning electron microscope (SE M) chamber for in situ observation and was applied for tensile testing of polycrystalline silicon (poly-Si) thin films with dimensions of 30 -300 mu m long, 2-5 mu m wide, and 2 mu m thick, It was found that the mean tensile strengths of nondoped and P-doped poly-Si are 2.0-2.8 an d 2.0-2.7 GPa, respectively, depending on the length of the specimens, irrespective of the specimen width, Statistical analysis of these siz e effects on the tensile strength predicted that the location of the f racture origin was on the edge of the specimen, which was identified b y the SEM observation of the fracture surface of the thin films.