Paper TF-TuM6
Area Selective Atomic Layer Deposition of Dielectric Films on Metal/Dielectric Patterns

Tuesday, October 29, 2013, 9:40 am, Room 104 A

Electronic devices consisting of a variety of different materials continue to undergo rigorous scaling to achieve higher switching speeds. Planar and 3-D structures such as those found in FinFETs and in the transistor backend contain metal/dielectric patterns, for which selective deposition processes may facilitate the fabrication of devices with feature sizes on the order of nanometers. Selective deposition approaches are required that can provide deposition of different materials with a variety of thicknesses while maintaining the selectivity up to higher thickness limits.

Atomic layer deposition (ALD) is a good choice for selective deposition because it is based on self-limiting reactions between gas phase precursors and specific functional groups at the growth surface. This chemical specificity provides a means to achieve selectivity in ALD on a spatially patterned substrate. In previous studies on area selective ALD of dielectrics on a dielectric pattern, deposited thicknesses were on the order of nanometers. The selectivity was generally obtained by passivation of the surface using self-assembled monolayers (SAM) in the regions where ALD was not desired. However, existing methods for selective ALD likely do not have the robustness needed for deposition of thicker films. Hence, there is a need for new approaches to achieve selective dielectric-on-dielectric growth for film thicknesses of 10 nm or more.

In this work, we probe the thickness limits of area selective deposition of dielectric-on-dielectric by selectively depositing an organic SAM as the blocking layer on metal parts of a metal/dielectric (Cu/SiO₂) pattern. Both alkanethiols and alkylphosphonic acids have been reported to form well packed SAMs on metal surfaces. Here, we apply them to area selective ALD, and examine the blocking properties of octadecylphosphonic acid (ODPA) and octadecanethiol (ODT) SAMs on Cu. We show that both of these SAMs can prevent subsequent deposition of metal oxide dielectric films via ALD. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) confirm no growth of the metal oxide on the ODPA-protected Cu for up to 36 nm of metal oxide deposition, while ellipsometry and XPS results show metal oxide growth on the dielectric regions of the samples, i.e. SiO₂. We also report results on regenerating the ODT SAM protecting layer between ALD cycles and show that this approach is effective in improving the blocking properties of the SAM on Cu. This strategy provides the ability to carry out selective deposition for film thicknesses greater than 30nm, opening up the possibility for new applications in next generation electronic devices.