Thermal stability of thin poly-Si/Ta2O5/TiN capacitors for dynamic random access memory applicationsThe properties of Ta 2 N and TaN compound films as a diffusion barrier between Cu and Si have been investigated by examining compositional depth profiles obtained by Auger electron spectroscopy. The use of a Ta 2 N barrier is effective for improving the thermal stability of the contact system by raising the silicide formation temperature as compared with the use of a Ta barrier. The contact system of Cu/TaN/Si is fairly stable due to annealing for 1 h even at 750°C. This is interpreted by the stability of the TaN compound, which is chemically inert to Si as well as Cu at this temperature. Eliminating the grain growth of TaN due to annealing is also effective for suppressing the physical diffusion through the barrier.
Thin film reaction of transition metals with germaniumAlloy films of Ta 1−x W x were prepared by co-sputtering and their diffusion-barrier properties in Cu/ Si contacts were examined. The alloy films over 30 at. % of the W composition were in a state of substitutional solid solution, and the resistivity of 100-nm-thick film was ϳ45 ⍀ cm, at most. In the Cu/ Ta 1−x W x / Si contacts, the silicidation temperature of 680°C was higher than that reported for the Cu/Ta/Si or Cu/W/Si contact. We confirmed for the Cu/ Ta 0.5 W 0.5 / Si contact that Cu penetration into the Si substrate was completely suppressed by a thin amorphous interfacial layer upon annealing at temperatures below that of silicidation reaction. It was revealed that at more elevated temperatures, an extremely small amount of Cu atoms was incorporated into the silicide layer at the Ta 0.5 W 0.5 / Si interface during reaction and penetrated into the Si substrate through the silicide layer.
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