다마신 구리 배선 구조에서 은 박막을 이용한 산화 방지 방법

Abstract

As a density of the devices per chip increases, a resistance-capacitance time delay from an interconnection recently limits the overall chip speed. Therefore, low resistivity copper was introduced instead of aluminum and new method that is damascene process accordingly was also introduced. In this paper, the effect of PEG and HCl at the copper electrodeposition and the oxidation preventive method were investigated. The addition of PEG and chloride ion strongly inhibits the deposition of copper. Especially, when the molarity of PEG is same with chloride ion, the suppression effect was maximized (40 % reduction of deposition thickness). PEG and HCl inhibit the copper deposition by the adsorption of a suppressing species. Raman spectra of PEG with CuSO4 showed changes of oxygen related band as compared with pure PEG. This is the evidence of complex formation by PEG and CuSO4. The increased resistivity of the deposited copper in the presence of PEG and chloride ion recovered to about 1. 7 μΩ ㎝ through annealing at 400℃ for 30 min in N2 atmosphere. Displacement deposited Ag layer at the expense of very thin Cu was investigated as an oxidation barrier in damascene Cu structure. A 40 nm thick bright and continuous Ag film was formed at the surface of electrodeposited Cu by simply immersing the copper film into the silver displacement solution. Oxidation resistance of four different kinds of samples (electrodeposited copper, annealed electrodeposited copper, silver passivated electrodeposited copper, and annealed silver passivated electrodeposited copper) were compared. Ag film at Cu surface drastically blocked the oxygen diffusion into the Cu film and retarded the oxidation. More importantly, upon annealing at 400℃ N2 atmosphere, further ability of oxygen diffusion barrier via elimination and stuffing of grain boundaries of Cu was observed.