優先配向を有する多結晶シリコン薄膜におけるピエゾ抵抗係数の上下界導出法

概要

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This paper proposed the derivation method of upper and lower bounds for variable piezoresistive coefficients of polycrystalline silicon (polysilicon) films having preferred orientation. Two sets of fundamental piezoresistive coefficients of the polysilicon film were derived from the coefficients of single-crystalline silicon using two approximation models based on assumptions that the stress is uniform and the resistivity change is uniform at any point of the film. The upper and lower bounds for the effective piezoresistive coefficients were mathematically defined using the piezoresistive coefficients obtained from the two approximation models. In order to confirm the validity of this definition, the upper and lower bounds, which are applicable to any polysilicon film, were calculated, and were compared with the measurement results previously reported by some groups. The upper and lower bounds were consistent with the measurement results, which supports the validity of this derivation.