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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.

A thermally stable Cu/ZrN/Si contact system using a ZrN diffusion barrier of low resistivity was developed. In the contact system, the growth of an oriented ZrN(100) layer on Si(100), and subsequent growth of a Cu(110) layer on ZrN(100) were observed. The obtained contact system was fairly stable after annealing even at 750 °C for 1 h without any diffusion and/or reactions at either the interface of Cu/ZrN or ZrN/Si. It was revealed that the ZrN layer with low electrical resistivity showed a high performance as a diffusion barrier, and was one of the excellent materials for the use in ultralarge scale integration technology.

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