Spin coating experiments and theory for undergraduate physics and engineering students—A connection to microfabrication.

Spin coating is a process by which thin and uniform layers of liquids are formed on substrates by rotation of the substrate at high speed. Production of these thin liquid layers, specifically using liquids called photoresists, is essential for photolithography in semiconductor and microelectronics processing whereby patterns are transferred and ultimately formed in layers on the substrate. With the surge in interest for increased domestic semiconductor processing capabilities, it makes sense that students in physics and engineering are provided with more knowledge of these processing techniques and how they rely on, among other things, traditional course work, and topics. Spin coating provides an excellent example to connect fluid dynamics with microfabrication. We present detailed experiments that can be performed in a college-level undergraduate laboratory, wherein students can explore both the variables appearing in a known model for spin coating in addition to investigating several of the variables related key assumptions used in the derivation of the model but which do not appear in the resulting equation. Editor's note: The semiconductor industry, which is predicted to reach US$1 trillion by 2030, is a major employer of physicists. Semiconductor processing relies on photolithography, and photolithography relies on spin coating of photoresists. These facts on their own might inspire instructors to teach students about spin coating, even if the phenomenon was not such a beautiful application of fluid mechanics. This paper shows you how to teach students about spin coating using inexpensive equipment and safe fluids (corn syrup, castor oil, and olive oil). Students can predict how and whether the film thickness depends on variables such as density, speed, viscosity, and time, and can test these predictions in the laboratory. [ABSTRACT FROM AUTHOR]