Space charge distributions in Polyimide thin films determined by FLIMM

Polyimides (PI) are used in microelectronics mainly as insulating and passivating layers. In these applications space charge-related processes such as conduction, field distortion and ageing phenomena are important to consider for reliability and failure purpose. It is therefore of great interest to estimate these distributions in order to optimize PI-containing structures and designs. However, no space charge measurements have been reported for PI films of the order of 10 μm thickness, and anyway such results are scarce whatever the material considered. In this preliminary work, space charge distribution in PI thin film has been measured after the application of a dc electric field using metal-insulator-semiconductor structure by Focused Laser Intensity Modulation Method. Different types of electrode substrate (n-type Si and p-type Si) have been considered to evaluate their influence on space charge formation. Experimental results demonstrate that the amount of charge and the polarity of the dominant injected charges exhibit an important dependence on the electrode substrate.