We used electrical characterization as well as surface analytical methods to understand leakage behavior and breakdown mechanisms of three different interlayer dielectrics (ILD) in detail. Leakage current measurements were conducted on Back End of Line (BEoL) metal comb structures with variations of line spaces. Schottky barriers as well as trap potential heights were estimated. Furthermore the Schottky barrier height was determined on blanked wafers by X-Ray Photoelectron Spectroscopy (XPS) and Reflection Electron Energy Loss Spectroscopy (REELS). A correlation between the two methods was established. In addition REELS studies were performed on samples with etch induced damage that was emulated by argon sputtering of pristine ILDs. Two defect states have been found within the band gap of all ILDs, which could influence the electron transport at the dielectrics interface.