Hot-wire assisted atomic layer deposition of Tungsten films

This thesis aims to establish a novel technique of atomic layer deposition (ALD) for the future ultra-large-scale integration (ULSI) of microelectronics. We developed a hot-wire assisted ALD (HWALD), where a heated tungsten (W) filament is utilized instead of a plasma to generate radicals. HWALD is expected to be another candidate for deposition in future ULSI technology. Particularly, this thesis focuses on the application of HWALD for W deposition by providing sequential pulses of atomic hydrogen (at-H) and WF6. This thesis demonstrates the results of HWALD W in the cold-/hot-wall reactor. In the cold-wall reactor, β-phase W of high resistivity was obtained, whereas the α-phase W of low resistivity was obtained in the hot-wall reactor. The α-phase W possessed a low resistivity of 15 µΩ•cm. Furthermore, a uniform and conformal coverage of HWALD W on high aspect ratio structures (up to an aspect ratio of 36). Moreover, an inherent area-selective HWALD of W was proposed. The nucleation and growth of HWALD W on various substrates were studied. No nucleation was found on a thermally-grown SiO2 surface nor on (ALD-grown) TiN and Al2O3 surfaces. On the contrary, HWALD W could be successfully deposited on W and Co surfaces. Due to the nucleation delays on different surfaces, an area-selective HWALD W process was achieved on W/SiO2 and Co/SiO2 patterned surfaces