Aminosilane small molecule inhibitors for area-selective deposition: Study of substrate-inhibitor interfacial interactions

Abstract

Area-selective atomic layer deposition (AS-ALD) is a coveted method for the fabrication of next-generation nano-electronic devices, as it can complement lithography and improve alignment through atomic scale control. Selective reactions of small molecule inhibitors (SMIs) can be used to deactivate growth on specific surface areas and as such enable AS-ALD. To investigate new applications of ASD, we need insight into the reactions of SMIs with a broad range of technology relevant materials. This paper investigates the reactions of aminosilane SMIs with a broad range of oxide surfaces and the impact on subsequent atomic layer deposition (ALD). We compare the reactions of two aminosilane SMIs, namely, dimethylamino-trimethylsilane (DMA-TMS) and hexamethyldisilazane (HMDS), with a hydroxylated SiO2 surface and the impact on subsequent ALD processes. The DMA-TMS reaction saturates faster than the HMDS reaction and forms a dense trimethylsilyl (TMS) layer with a higher TMS surface concentration. The higher TMS surface concentration yields better inhibition and higher selectivity during subsequent TiO2 ALD. We show that a wide range of surfaces, i.e., MgO, HfO2, ZrO2, Al2O3, TiO2 (TiN/TiOx), SiO2, SnO2, MoOx, and WO3 remain reactive after DMA-TMS exposure for conditions where SiO2 is passivated, indicating that DMA-TMS can enable AS-ALD on these surfaces with respect to SiO2. On these surfaces, DMA-TMS forms residual TMS and/or SiOxCyHz surface species that do not markedly inhibit ALD but may affect interface purity. Surfaces with lower, similar, and higher surface acidity than SiO2 all show less reactivity toward DMA-TMS, suggesting that surface acidity is not the only factor affecting the substrate-inhibitor interaction. Our study also compares a hybrid inorganic-organic SnOxCyHz and inorganic SnO2 material in view of their relevance as resist for extreme ultraviolet lithography. DMA-TMS can enable selective infiltration in SnOxCyHz, as opposed to selective deposition on SnO2, indicating tunable reactivity by bulk and surface composition. These insights into the reactivity of aminosilane SMIs may aid the design of new area-selective deposition processes, broaden the material space, and enable new applications.