Impact of SiO2 surface composition on trimethylsilane passivation for area-selective deposition

Alkyl-terminated surfaces have received significant interest as growth-blocking surfaces in area-selective deposition (ASD). Gas-phase chemical functionalization is attractive in this context due to its short process times, potentially wide applicability, and ease of integration in industrial process flows. However, the relation between the surface chemistry, the passivating agent, and the growth-blocking efficacy of such treatments is not well understood which can lead to suboptimal passivation performance. This work investigates the reaction between dimethylamino-trimethylsilane (DMA-TMS) and SiO2 surfaces with varying composition, and identifies the impact of surface composition on passivation efficacy and selectivity. DMA-TMS reacts rapidly with Si–OH groups on SiO2 in a self-limiting surface reaction, resulting in an –O–Si(CH3)3 covered surface. In contrast, Si–O–Si groups are either unreactive or significantly less reactive towards DMA-TMS. Increasing the number of Si–OH versus Si–O–Si groups on the initial SiO2 surface therefore results in a higher –O–Si(CH3)3 density after DMA-TMS treatment. As a consequence, the selectivity of an ASD process towards SiO2 improves, as demonstrated for ruthenium atomic layer deposition from 1-ethylbenzyl-1,4-cyclohexadienyl-ruthenium and oxygen. This work illustrates the impact of tuning surface composition on passivation and selectivity for ASD.