During the plasma etching of Al-Si-Cu alloy used as a metal interconnection, it is generally reported that the metal pillar (or conical residue) affecting the degradation of device yield is formed by the micromasking effect of copper compound. However, it is stilldisputed with the formation mechanism and composition of the micromasking material. Moreover, the elimination method of the metal pillar is not well known.
According to previous reports, it is argued that the micromasking material consists of Cu agglomerates, A12Cu, or CuC1, and the formation mechanism of the micromasking is due to byproduct during plasma etching or reaction product during metal depositionor etching. However, using scanning electron microscopy (SEM), energy dispersive of x-ray (EDX), and high resolution Auger spectroscopy (HRAES), it is newly found that the micromasking consists of three layered structure, that is copper aluminum oxide, A12Cu, and Cu agglomerates. These results are quite different from previous reports. In addition, the removal methods of the metal pillar are suggested, which are high power dry etch process and multilayered metal deposition.