We report for the first time the effect of a Cu flash layer sandwiched between copper film and TaN barrier layer on the properties of copper films. The structures studied, including a Cu film deposited by Metal Organic Chemical Vapor Deposition (MOCVD), Cu flash layer and TaN barrier by ionized metal plasma (IMP) technique on Si substrate with SiO2, were fabricated in a three-in-one system supplied by Applied Materials and characterized by x-ray diffraction, atomic force microscopy, adhesion test and stress measurement. By depositing a Cu flash layer with IMP technique prior to the MOCVD deposition, the properties of the MOCVD Cu films can be significantly improved. The <111> oriented diffraction intensity of the Cu film is found to increase, while the intensity of other direction diffraction <200> to decrease as the thickness of the Cu flash layer is increased. The adhesion strength of the CVD Cu film to the flash layer and TaN barrier metal, determined by scratch test and pull tester, is enhanced as the Cu flash layer becomes thicker. The root mean square roughness and the grain size of CVD Cu film is found sensitive to the Cu flash layer and can be optimized by monitoring the deposition of the Cu flash layer. In addition to these, some other properties of the Cu film and the mechanism for the improvement in the properties are also discussed.