Change of Mechanical Properties of Ta2O5 Thin Film during Crystallization Annealing.

Abstract

With the increasing level of integration in semiconductor devices, Ta2O5 thin film is attracting much interest for use in the capacitors of semiconductor memory devices because of its high dielectric constant. In the fabrication process of the device, the Ta2O5 thin film is deposited in the amorphous condition and then crystallized by annealing. In order to increase the mechanical reliability of the capacitors, the change in mechnical properties of the Ta2O5 film during crystallization must be determined. The Young's modulus was therefore measured by the three-point bending method, and residual stress and thermal expansion coefficient were calculated by measuring the curvature of a substrate with the Ta2O5 film. It was found that the crystallization increases the residual stress of the film from 250 to 400 MPa and the Young's modulus from 130 to 180 GPa.And the thermal expansion coefficient is decreased from 5.7×10-6 to 3.6×10-6.