Area-selective atomic layer deposition of Al2O3 film on Cu and Si substrates using bulky Al precursor AlMe2(iPr-AMD)

Trimethylaluminum (TMA) loses its selectivity within a short time, which is problematic because it exhibits excessively high reactivity toward H2O and surface sites, an extremely small molecular size, and low thermal stability even if a passivation layer is used. To achieve high selectivity, precise control of the reaction between the precursor and the substrate surface and minimization of unwanted reactivity are essential. Therefore, to achieve excellent area-selective atomic layer deposition (AS-ALD), we thoroughly investigated novel precursors and found that AlMe2(iPr-AMD) is an outstanding candidate that exhibits good thermal properties and high volatility. We carried out AS-ALD of an Al2O3 film on Cu and native oxide Si substrates using AlMe2(iPr-AMD) with H2O as a coreactant. For the dielectric-on-dielectric selective growth process, 1-dodecanethiol (DDT) was used as a self-assembled monolayer (SAM) passivant on the Cu surface. The Al2O3 film growth was inhibited on the Cu surface as a result of passivation by the SAM during deposition of a >100 Å-thick Al2O3 film onto the native oxide layer of a Si surface at 150 °C using AlMe2(iPr-AMD). For the dielectric-on-metal selective growth process, n-octadecyltrichlorosilane (ODTS) was used as a SAM passivant on the dielectric surface. In contrast to the DDT SAM, the ODTS SAM showed restrained Al2O3 film growth on the Si surface and achieved Al2O3 film growth only on the Cu surface. These results indicate that the AlMe2(iPr-AMD) precursor adsorption is strongly inhibited by SAM passivation as a result of its bulky structure, reduced Lewis acidity, and lower level of reactivity compared to TMA.