Comparison of the Young's modulus of polysilicon film by tensile testing and nanoindentation

This paper focuses on the derivation of reliable Young's modulus for thin polysilicon film by a Nanoindenter® through comparisons with two direct techniques, an interferometric strain/displacement gage and a microvernier gage. For this purpose, a specimen having 50 μm wide, 3.5 μm thick, and 1 mm long gage section is used. Narrow platinum lines are deposited 250 μm apart on the specimens to form interference patterns. Load is applied by a piezo-actuator. Four microverniers are added at the top and bottom portions of the gage section. The images of the vernier while testing are recorded and analyzed later after testing. The Young's modulus values calculated by the two direct methods are very similar and the value is about 163 GPa. After testing with the ISDG and the vernier, the untested part of the same specimen is used for nanoindentation. A scanning probe microscope is used to scan the indented surfaces. An extensive parametric study is performed to get reliable modulus values. The 'strain rate' in a nanoindentation test is one of the governing parameters for the correct measurements of Young's modulus.