Low Temperature Deposition of Ge Thin Films for Phase Change Memory

Abstract

The deposition of Ge-Sb-Te (GST) chalcogenide alloys in high aspect-ratio trench structures via CVD and ALD-like processes has attracted great attention for their application in next generation non-volatile Phase Change Random Access Memory (PRAM) devices. Several Ge (II) silylamido precursors were synthesized and characterized, and their behaviors in thermal CVD processes explored. Of these, a novel Ge precursor - bis (2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentanide) germanium (II) was found to give a deposition rate of 1 Aå/min at 320 ºC by using NH3 as a co-reactant gas. Deposition rates below 0.1 Aå/min at these temperatures were obtained in the presence of H2 or an inert gas, which means this precursor exhibits the co-reactant limited deposition which is desirable for good step-coverage and uniform film growth in ALD. Data will be presented on deposition rates vs. temperature using this precursor and compared with two other bis(silylamido) germanium precursors. Preliminary results on the deposition of GeTe binary films will also be presented.