Low-temperature laser deposition of tungsten by silane- and disilane-assisted reactions

Abstract

A reaction, based on tungsten hexafluoride chemically reduced by silicon hydride vapors, has been developed for low-temperature laser deposition of high-purity tungsten. Compared to previous tungsten deposition methods, the new (pyrolytic) process requires very little thermal energy for initiation and propagation of the scanned reaction. WF6 and SiH4 (or Si2H6) mixtures have been optimized to yield tungsten interconnect lines with abrupt square cross section and conductivities of 12–25 μΩ cm. Impurity levels are below the detection limits of Auger spectroscopy. Lines 3–20 μm in width and 0.1–4 μm in thickness are written at scan speeds of ∼100 μm/s. Argon-ion laser powers (488 nm) are typically 30–60 mW, corresponding to reaction temperatures sufficiently low for direct writing on polyimide dielectrics.