Low-Temperature Dechlorosilylation Chemistry for Area-Selective Deposition of Ge2Sb2Te5 and Its Mechanism in Nanopatterns

Area-selective deposition (ASD) is a bottom-up patterning technique that is of interest for nanoprocessing and next-generation semiconductor device manufacturing. This work demonstrates the great potential of dechlorosilylation chemistry for ASD through the example of Ge2Sb2Te5 (GST), a promising phase change material for storage class memory (SCM) applications. The fabrication of SCM devices may be facilitated by ASD as it involves complex nanoscale three-dimensional structures. We therefore investigate GST ASD on a TiN growth area with SiO2 as a nongrowth area. A selectivity of >0.9 is maintained up to ∼45 nm of GST by using a single reaction of an aminosilane small molecule inhibitor in combination with GST atomic layer deposition (ALD) with GeCl2·C4H8O2, SbCl3, and Te[(CH3)3Si]2 as precursors at 70 °C. The high selectivity is maintained for much thicker films compared to that of previously investigated ALD chemistries that use other precursors and O2, H2O, or NH3 co-reagents in combination with the same inhibitor. Interestingly, the selectivity, the ideal 2:2:5 composition, and the amorphous phase of Ge2Sb2Te5 are maintained during ASD on SiO2/TiN line patterns with a half-pitch of 45 nm. A careful study of the growth evolution suggests that the growth mechanism for ASD on these nanopatterns relies on diffusion in addition to adsorption, indicating that diffusion-mediated selective deposition is not limited to metal ASD processes such as those of Ru and Pt. We propose that the combination of the ALD dechlorosilylation chemistry with passivation approaches including small molecule inhibitors creates a promising avenue for expanding the ASD material space to a wide range of new materials, enabling new applications for ASD in nanoelectronics, nanoprocessing, catalysis, etc.