Handbook of Modern Coating Technologies

Modification of materials for the creation of small-sized 3D structures

The first PBW studies were published in the late 1990s [117—119]. They demonstrated the possibility of utilizing focused 2-MeV proton beams to create micro-components and revealed a number of physical principles making PBW a promising technology for producing
nanostructures. In the past decade (2000—10), this technology was being developed along several lines, including the improvement of focused beam characteristics and the evaluation of beam interactions with various resistive materials. A theoretical analysis of manufacturing sub-100-n structures was undertaken [120]. An important advantage of PBW is the possibility of obtaining nanocomponents with a high aspect ratio (160:1), making such structures essen­tially three-dimensional. This required evaluation of the influence of different conditions of focused ion beam irradiation on the quality of resultant nanocomponents. In the experi­ments reported in Refs. [121,122], the roughness height at the side walls was measured to range from 3 to 7 nm depending on the type of the resistive material and the irradiation algorithm. This characteristic is of importance for applications where nanocomponents serve as channels for flowing liquids and for creating nanostamps. Another important characteris­tic is side wall prismaticity. As shown in the article [123], since the proton trajectories in a resist material are rectilinear, the angle between the side wall and the surface is 89.5 degrees. Further improvement in PBW technology is currently underway in several laboratories [124,125]. Operating modes and irradiation conditions for various resists are fairly well estab­lished. Proton fluences and characteristic dimensions of the resulting in small-sized compo­nents for different types of resists are listed in Table 5.2.

Using hydrogen silsesquioxane (HSQ) as a resist, a structure in the form of a separately standing line (a protrusion with a characteristic width of 22 nm) was obtained [127] (Fig. 5—10). The next step was the introduction of the results of studies into production sys­tems for manufacturing nanocomponents. A PBW-based MIF was developed at the Shibaura Institute of Technology, Tokyo, Japan, for market promotion and industrial application [128].

Micro- and nanostructures produced by focused charged particle beams have a broad range of applications, some of which are discussed later.