Directed Self-Assembly: From the Top-Down to the Bottom-Up

In previous posts, we’ve made references to Moore’s law and how, with uncanny accuracy, it has predicted that the number of transistors in a dense integrated circuit (IC) would double approximately every two years. The semiconductor industry has tirelessly chased Moore’s law ever since it was first coined in the 1970s, but as ICs have become smaller and smaller, traditional lithography processes have made it more and more difficult to keep up.

Current manufacturing techniques use a top-down approach, meaning that they do not focus on the nanolevel. Instead, they work with existing products and try to make changes to accommodate the needs of the industry. In contrast, a bottom-up approach to manufacturing would mean using nanotechnology to address the need on an atomic level, assembling the product atom by atom. It’s the difference between carving away at an existing tool until you make the tool that you need and building the tool from scratch based on your needs. The bottom-up approach is still in its theoretical stages but looks promising as the future of the industry. One such approach is called directed self-assembly (DSA). At Brewer Science, we are leading the industry with this technology.

Scientists are taking more cues from the world around them as technology advances. Man-made products have long attempted in vain to mimic the elegant molecular processes of nature—the fluid ways with which molecules form and combine, the processes by which cells are formed and duplicated. This natural propensity of molecules to orient themselves is the inspiration for the DSA work being done today. Using DSA, we are able to manipulate products on the nanolevel and use the natural orientation of molecules to bring new products to life.

Most polymers used in commercial manufacturing are random copolymers, meaning that the two different types of monomers of which they are composed are configured in a random pattern, with no order involved. Block copolymers are also composed of two different types of monomers yet are segregated by type. Imagine a string of red and green Christmas lights: In a random copolymer, all of the lights are in an unstructured, random pattern of intermixing red and green. In a block copolymer, all of the of red lights would be on one end, and all of the green lights would be on the other.

DSA relies on these block copolymers to create a sort of organized polymer map on the wafer using conventional lithography methods to control the polymer configuration, combining the top-down and bottom-up approaches. By creating physical walls with photoresist (the graphoepitaxy method) or creating a designed chemical outline on the wafer (the chemoepitaxy method), we can guide the polymers into certain desirable patterns. Because the blocks of different monomers naturally want to separate yet are covalently bonded together, the block copolymers form into various shapes, including cylinders or even spheres, depending on their structure. These shapes allow for varying pattern combinations, increasing our range of possible configurations and subsequent products.

Nanotechnology is currently only in its infancy; we are designing materials right now to perform one specific task at a time. The future generations of nanotechnology development could bring multitasking nanostructures and integrated nanosystems that could accomplish complex and sophisticated processes.

We don’t know what the future of nanotechnology will bring. But we have the tools to use when we get there. Brewer Science is prepared for the next generation. Are you?


Check out our new DSA video at for a visual glimpse into the magic of directed self-assembly.

  Directed Self-AssemblyLithographyDSAIntegrated Circuits
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