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In Situ Reflectometry During LPCVD Tungsten Growth

By J. Holleman, A. Hasper and J. Middelhoek


The formation of LPCVD tungsten by means of the reduction of WF6 with Si, H2 and SiH4 is monitored in situ using a wavelength adjustable reflectometer. The initial self stopping growth of W by Si reduction is strongly dependant on surface status [1]. SEM observations together with Auger depth profiling and weight measurements support a growth model of islands that grow laterally and vertically until islands touch. After the self stopping Si reduction the W layer was increased in thickness by either the h or SiH4 reduction. The surface roughness calculated from the reflectance appears to increase linearly with thickness in the case of H2 reduction. Typical rms roughness was found to be 7% of layer thickness in the H2 reduction case. The reflectance of H2 reduced W layers could be improved by interrupting the growth process with a renucleation step using SiH4. Selective deposition and in situ growth rate measurements can be monitored when the deposition is carried out on a grating of SiO2 as a mask. Precleaning of the reactor with an NF3 plasma results in a strong retardation of the H2 reduction reaction

Publisher: 'Cambridge University Press (CUP)'
Year: 1990
DOI identifier: 10.1557/proc-168-107
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Provided by: NARCIS
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