Induced Thermal Residual Stress for a Highly Bendable Thin Film Encapsualtion

Abstract

Thin Film Encapsulation (TFE) is necessary for environmental stability of the organic electronics, but its fragility should be overcome. In this study, a compressive thermal residual stress is introduced at the organic/inorganic layer interface to release the external tensile bending stress. To induce the optimized thermal residual stress, material property and the thickness of the organic layer are engineered. Cyclohexyl acrylate (CHA) and 1,3,5-trimethyl-1,3,5-trivinyl cyclosiloxane (V3D3) are copolymerized for the organic material of the TFE. Modulus and the thermal expansion coefficient (CTE) are determined by controlling the ratio of the monomers. Distinct process temperature of iCVD (30 °C) and ALD (50 °C) induce a negative thermal residual stress. Thermal residual stress is optimized by tuning the thickness of the organic layer. With the compressive thermal residual stress, TFE maintains its barrier performance after bending 1000 times with the tensile strain of 1 %.