Background
As device dimensions for integrated circuits continuously scale downwards, significant focus has been devoted to developing alternate processes for the nanofabrication of functional structures. One of the processes being explored is called area-selective atomic layer deposition (AS-ALD). In contrast to conventional lithography techniques, AS-ALD does not require any subsequent etch steps, making it a promising alternative for patterning. In a typical AS-ALD process, a surface is patterned with functional groups that have different reactivities to both of the ALD precursors. The ALD precursors react selectively with one of these regions of different functional groups and in a self-limiting fashion, deposit only in the preferred region until the desired thickness of the pattern has been achieved. In general, these functional groups are deposited using techniques such as microcontact printing, photolithography, and nanolithography, which have been used to create surfaces with different reactivities. These methods, however, are very challenging to apply over surfaces that already have curvature and rely on lithographic and etching techniques to get this initial surface.
Technology description
Researchers at The University of Texas at Austin have developed a method to deposit metals on a nanomaterial using self-assembled monolayers (SAMs). SAMs such as alkylchlorosilanes and alkylmethoxysilanes are reacted with a patterned surface. These SAMs “assemble” in large regions but contain defects around edges and corners of features due to the effects of the curvature. These defects serve as nucleation sites for subsequent ALD, which will reduce the cost of nanomanufacturing processes by eliminating the need for any additional etching and lithography steps. More information may be found in this peer-reviewed journal article.
Figure 1. Schematic showing how SAM treatment across topography can be used to confer TiN ALD selectivity to different regions of a substrate.
