Thermal stability of nanoscale silver metallization in Ag/W/Co/Si(1 0 0) multilayer

In this work, we have studied thermal stability of nanoscale Ag metallization and its contact with CoSi2 in heat-treated Ag(50 nm)/W(10 nm)/ Co(10 nm)/Si(1 0 0) multilayer fabricated by sputtering method. To evaluate thermal stability of the systems, heat-treatment was performed from 300 to 900 8C in an N2 ambient for 30 min. All the samples were analyzed by four-point-probe sheet resistance measurement (Rs), Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD), and atomic force microscopy (AFM). Based on our data analysis, no interdiffiusion, phase formation, and Rs variation was observed up to 500 8C in which the Ag layer showed a (1 1 1) preferred crystallographic orientation with a smooth surface and Rs of about 1 V/&. At 600 8C, a sharp increase of Rs value was occurred due to initiation of surface agglomeration, WSi2 formation, and interdiffusion between the layers. Using XRD spectra, CoSi2 formed at the Co/Si interface preventing W silicide formation at 750 and 800 8C. Meantime, RBS analysis showed that in this temperature range, the Wacts as a cap layer, so that we have obtained a W encapsulated Ag/CoSi2 contact with a smooth surface. At 900 8C, the CoSi2 layer decomposed and the layers totally mixed. Therefore, we have shown that in Ag/W/Co/Si(1 0 0) multilayer, the Ag nano-layer is thermally stable up to 500 8C, and formation of W-capped Ag/CoSi2 contact with Rs of 2 V/& has been occurred at 750–800 8C