Cracks In Silicon Oxide Films:Morphologies And Influencing Factors

When a thin film moderately adherent to a substrate is subjected to residual tensile stress,the cooperation between film crack and interface debonding leads to unusual crack patterns,such as spirals,alleys of crescents and variously oriented strips.In order to study the mechanics of different crack morphology,silica sol prepared by sol-gel method is used herein.We use a spin-coater to plate that silica sol on the glass substrate,and change the interfacial property of the film layer between the film layers and the speed of the homogenizer to control the film thickness.Then we bring in the thermal stress by the way of high-temperature drying,and finally,many unique crack morphologies are observed after high temperature drying,such as straight-sided crack network,wavy crack network and their coexistence.The optical microscope and scanning electron microscope reveal that the coexistence and transition of these two kinds of crack networks are closely related to whether the interface debonding occurs simultaneously or not.The influence of film thickness on crack morphology is also analyzed,and the effect of thin film thickness on the crack is found.One is that the thickness of the film changed the overall morphology of the crack,and the other influence of thickness is the wavelength of the same crack.This paper analyzes and classifies the changes in the overall morphology of cracks under different film thicknesses.There is a linear relationship between wavelength and thickness of the crescent crack.The observation also has the initial growth process of the crack,which is a simple analysis of the process of cracking the crack network.Subsequently,some new special morphological cracks are reported,and the reasons for the formation of these special morphological cracks are analyzed.Finally,our phase field simulation has recovered formation of straight-sided and curved crack networks.It is worthwhile to further elucidate how the interface debonding facilitates formation of the wavy crack network by using such phase field modeling in future.In this paper,we provide a reliable support for understanding the formation of cracks.