In this blog post, we’ll explore the concept and manufacturing methods of thin films—a representative technology of nanotechnology—as well as the reasons they are utilized across various industrial sectors.
Nanotechnology is one of the most talked-about fields of the 21st century. At some point, terms like “nano” and “ultra-small” became commonplace, appearing not only in the news but also on the streets. “Nano” is a prefix meaning one-billionth, and 1 nanometer (nm) equals one-billionth of a meter. Nanotechnology refers to the technology of creating and manipulating materials at the nanometer scale. A prime example of this nanotechnology is the thin film. While the membrane forming a soap bubble or an oil film floating on the surface of water can be considered thin films in a broad sense, in general, the term refers to extremely thin layers of metals, semiconductors, insulators, and other materials formed in the desired location, shape, and structure in industrial settings. Thin films, as the name implies, are extremely thin layers, and even today, they are utilized as core technologies in various high-tech industries, including semiconductors and displays. Generally, thin films refer to layers so thin that they are difficult to produce through mechanical processing alone. So, how are thin films made, and why do people pay so much attention to them?
First, thin-film fabrication technologies are traditionally categorized into wet and dry methods. Wet methods are further divided into electrolytic and non-electrolytic processes. Although electrolytic and non-electrolytic processes differ in their specific procedures, they share the common feature of utilizing plating technology. Dry methods are classified into Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), and thermal spray. CVD and PVD both share the common feature of using raw materials in a gaseous state. However, while PVD primarily forms thin films by utilizing the physical changes of raw materials under vacuum conditions, CVD involves the deposition of a thin film through chemical reactions between the raw materials supplied onto the substrate, generally requiring high process temperatures. The thermal spray method refers to a technique in which the material intended for thin-film formation is sprayed onto the surface of an object to create a coating.
In addition to these traditional thin-film fabrication techniques, spin coating is another widely used method. Spin coating is a process in which the material to be used for the thin film is dropped onto a substrate, which is then rotated at high speed to form a thin film. It typically uses liquid-state precursor materials; the centrifugal force generated by high-speed rotation removes excess solution and results in a thin film of uniform thickness. Therefore, the thickness of the thin film can be controlled by adjusting the rotation speed, and the structure and properties of the thin film vary depending on the interaction between the precursor and the substrate, as well as the process conditions. As various fabrication technologies, including spin coating, continue to advance, more precise and efficient methods for fabricating thin films are steadily being developed.
So why have thin films produced in this way garnered so much attention? To understand the reason, we need to examine the characteristics of thin films. When a material is in a thin-film state, its inherent physical and chemical properties may change. For example, a metal that is not easily combustible under normal conditions may oxidize readily when in the form of a very thin film, and certain insulating materials may exhibit changes in their electrical properties at extremely thin thicknesses. By appropriately utilizing these changes in properties, it is possible to enhance the performance of various electronic components, including semiconductors.
Furthermore, generally speaking, as particle size decreases, the ratio of surface area to volume increases. Since volume is proportional to the cube of a length and surface area is proportional to the square of a length, the ratio of surface area to volume becomes larger as the size decreases. Therefore, fabricating materials into thin-film form allows for a significantly larger surface area, enabling more efficient enhancement of various reactions and performance characteristics. Furthermore, since the structure and properties of thin films can be precisely controlled by adjusting the conditions during the fabrication process, they are widely applied in numerous fields—including semiconductors, displays, and energy devices—and their importance continues to grow.
So far, we have examined the types of thin-film fabrication technologies and the characteristics of thin films. Thin films have already established themselves as a core technology in various high-tech industries, including solar cells, displays, transistors, and semiconductors, and research and development continue steadily thanks to their high efficiency and excellent performance. However, many people still view thin films as a complex technology far removed from their own lives. Yet, if you take just a little interest and look into it, you will easily see that thin films are a crucial technology that powers the various electronic devices and high-tech industries in our daily lives. A small interest in science and technology will be the first step toward understanding future technologies.
