Abstract: A process for the preparation of free-standing polyimide (PI) thin films of less than 1 μm thickness was proposed and the property of the films was analyzed. In this process, a polyamic acid (PAA) thin film of 1 μm thickness was first prepared on a ZnO coated substrate and then released using diluted hydrochloride acid. The PAA film was reattached to the substrate and treated thermally to create a polyimide thin film. The thickness of the PI film was reduced using excimer laser ablation. The surface morphology and the spectral characteristics of the polyimide film were investigated using atomic force microscope, Fourier transform infrared spectroscope and spectrophotometry. Results showed that ZnO thin films sputtered at room temperature served as a good release agent for preparing free-standing polyimide films with thickness more than 950 nm. The thickness of the PI films could be reduced to as thin as 150 nm by excimer laser ablation. In the wavelength range from 400 nm to 2500 nm, the average transmittance increased from 80.3% to 83.5% when the thickness of the polyimide film decreased from 950 nm to 150 nm.

Key words: polyimide, KrF excimer laser, thermal imidization, zinc oxide