ナノ領域が支配するCu薄膜の界面端はく離強度特性

抄録

The stress concentration near interface edge dominates the delamination of thin films. The size of stress-concentrated region is dependent on the film thickness. As the film thickness is approaching 100 nm in an advanced LSI component, the region size is in the nano-scale. In this study, the delamination tests are conducted for multi-films, Cu/TiN, on a Si-substrate with different thickness of Cu (50 nm, 100 nm and 500 nm), and the effect of stress-concentrated region on the strength of Cu/TiN interface at the edge is examined. In the tests the stress-concentrated region is about 5 nm, 10nm, and 40 nm, respectively. In all experiments, the delamination crack initiates at the free edge of Cu/TiN interface. As the fluctuation of strength is small, the results are reliable. The stress distribution at the delamination reveals that the stress at the free edge is larger for thinner Cu film though it is reverse in the region of 20∼50 nm < r <300 nm (r: distance from the edge). Averaging the stress near the free edge, it is found that the delamination in all tests takes place when the stress at r <100 nm reaches about 18∼19 MPa. This signifies that the region of r <100 nm characterize the interface toughness and the size is larger than the stress-concentrated region in the specimen.