Characterization of charges in fluorinated polyimide film with different thermal history by using capacitance-voltage methods

We have studied the effect of thermal bake history of MPOS (Cu-fluorinated polyimide-SiO₂-Si) capacitor on the deviations from ideality, such as shifts or distortions, in the capacitance-voltage (C-V) curve characteristics. The dielectric constant was calculated to be 2.4 for the fluorinated polyimide film. It was observed, with bias temperature stress (BTS) technique, that mobile positive charges were responsible for the flat band voltage (V_FB) shift for the MPOS capacitor hard-baked at 325 °C and annealed at 425 °C. On the other hand, in the case of the MPOS capacitor hard baked at 350 or 375 °C and then annealed at 425 °C, immobile positive charges were observed. From the direction and amount of the shift, the charges responsible for the V_FB shift were positive ions and their concentration was approximately 10¹¹/cm². The activation energy of the positive mobile charge drift was calculated to be 0.6 V.