Stress mechanism analysis by finite element method for different dielectric films deposited with ion-beam assisted deposition on flexible substrates

Abstract

In this study, an investigation was made into the optical and stress properties of four dielectric films: silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5) and niobium pentoxide (Nb2O5). This was because they are commonly used in the optoelectronic and semiconductor devices. The classification of these stress properties includes tensor & compressive, thermal & intrinsic, and principal & shearing. The stress mechanism of these dielectric films deposited on polyethylene terephthalate (PET) and polycarbonate (PC) flexible substrates with ion-beam assisted deposition (IBAD) was investigated by the finite element method (FEM). Meanwhile, the equivalent room temperature (ERT) of FEM was used for the analysis of the intrinsic stresses, and then the methods of home-made phase-shifting shadow moiré interferometer and Mohr circle were employed to analyze the anisotropic principal and shearing stresses. The results demonstrated that the residual stress of these dielectric films could get broken on the PC flexible substrate. However, only all of the SiO2/PC films were measured. Also, the residual stress on PET flexible substrate could change from the tensile stress to the compressive one when the thickness of the film increased. However, only all of the Ta2O5/PET films got compressed when the film thickness increased. Therefore, the anisotropic stress of the four dielectric films on the PET substrate suggests that both the maximum principal and shearing stresses should be Ta2O5>TiO2≥Nb2O5>SiO2. They are proportion to Q (elastic-energy/mole). The FEM method combined with the high-order polynomial fitting curvature could obtain the intrinsic stress and yield the error within 2.47 %.