In microelectric packaging , polymer thin films are commonly used as dielectric materials. But mechanical properties of polymer are generally difficult to know, because of the time-dependent properties. Additionally, the mechanical properties of polymer thin film are not easily characterized by uniaxial tension or compression test. The relation between load and displacement obtained from Nano-indentation method gives a lot of information on the mechanical properties of thin films like stress-strain relation.
PIQ(Polyimide), Poly(imide-siloxane), BCB(Benzocyclobutene) were coated on silicon wafer by spin coating, and soft baking was followed on hot plate and then hard baking was carried out in a temperature-controlled condition. The mechanical properties of polymer, such as visco-elasticity, and viscous flow, are time-dependent. Therefore it is necessary to conduct a time-dependent test in order to obtain the mechanical properties of polymer. Creep test was conducted to evaluate the mechanical properties of polymer thin film using Nano-indenter.
From result, creep was followed by behavior of 4-element model (Burgers model). So, Creep equation can be obtained from Sneddon’s equation and constitute equation.
The resultant data from creep test was compared with CSM(Continuous Stiffness Method) Data to prove reliable. The time-dependent mechanical properties of polymer thin films from creep test showed no load-dependence within linear visco-elastic range.
The effects of curing temperature on the mechanical properties were also investigated using the above creep model.