Area-Selective Deposition of AlO_x and Al-Silicate for Fully Self-Aligned Via Integration

The rush for better-performing electronics, and manufacturing processes that heavily rely on “top-down” patterning techniques, is making the integration of “self-aligned” fabrication methods, such as area-selective deposition (ASD), a critical objective for continued device scaling. The fully self-aligned via (FSAV) scheme is broadly proposed as a “killer application” to determine whether ASD can shift from an R&D process to high-volume manufacturing. Nevertheless, the lack of a suitable low-κ deposition process has prevented the realization of FSAV by dielectric-on-dielectric ASD. This is primarily due to the high temperature and/or strong oxidizers employed during low-κ dielectric deposition and their unsuitability in the presence of organic masks, such as self-assembled monolayers (SAMs), used to prevent material nucleation during ASD. In this work, AlO x and Al-silicate atomic layer deposition (ALD) processes are studied to provide suitable materials for ASD-enabled FSAV. Dimethylaluminum isopropoxide and H 2 O are utilized to deposit the metal oxide, whereas Al-silicate is grown by adding 2,2-dimethoxy-1,6-diaza-2-silacyclooctane (DMDAcO) pulses to the AlO x ALD cycle. The selectivity of such processes is demonstrated on 50 nm Cu/SiO 2 structures, using octadecanethiol-derived SAMs to inhibit material nucleation on the metal lines. Scanning and transmission electron microscopies are employed to assess the quality of the ASD processes and investigate the mechanisms behind defect generation on a nongrowth surface. X-ray photoelectron spectroscopy measurements show the high purity of the AlO x film, whereas DMDAcO-ligand incorporation into the Al-silicate matrix is observed. Planar capacitor structures are used to assess the electrical properties of both ASD films, revealing that the silicate film exhibits a relatively low κ-value (5.3 ± 0.2), with a high acceleration field factor (32.4 ± 1.4) and a dielectric breakdown voltage of 6.0 ± 0.3 V at 100 °C.