Fabrication of Free-Standing Three-Dimensional Structures By Atomic Layer 3D Printing

Abstract

One of the most common processes to produce microelectronics is optical lithography. It combines deposition by different thin film techniques including CVD or ALD with etching of defined structures using masks [1]. This multistep procedure is time-consuming and wasteful of material. Spatial Atomic Layer Printing offers an alternative for the direct production of defined structures and therefore for components in microelectronics.In this study, free-standing three-dimensional bridges are produced using the atomic layer 3D printer, developed by ATLANT 3D Nanosystems, that provides direct atomic layer writing process. For this purpose, two crossing lines are deposited from a support and a print material, subsequently the support material is removed via wet chemistry etching processes. To ensure an intact bridge, different material combinations of platinum, titanium dioxide, silicon dioxide and zinc oxide are used and post-processed by different etching methods. In particular, the materials used and the type of etching play an important role in producing freely standing structures. Important aspects in the preparation of the component are the influence of the etchant on the materials, the temperature used, the surface tensions of the etchant and the cleaning agent as well as the mechanical stress during the process.The most promising material combination during the test series is a printing material of titanium dioxide deposited with TTIP and H2O and a support material of zinc oxide deposited with diethylzinc and H2O. To ensure the gentlest possible etching process, the support material is removed by vapor etching using hydrochloric acid and the sample is cleaned by immersion in a mixture of 90 % ethanol and 10 % water. As a result, most of the titanium dioxide bridges are retained and can be characterized (see Figure 1). It can be demonstrated that the ATLANT 3D Nanosystems atomic layer 3D printing process can be used for the direct deposition of free-standing three-dimensional structures that can be further used to fabricate components in microelectronics (see Figure 1).Figure 1. Free-standing titanium dioxide bridges (4000 cycles) produced with zinc oxide as the support material (2000 cycles) and etched with vapor of hydrochloric acid. SEM pictures of (a) multiple bridges, (b) single free-standing bridge.[1] W. M. Moreau, Semiconductor Lithography: Principles, Practices, and Materials. 2012. Figure 1