Knowledge Center
Knowledge Center

Directed Self-Assembly (DSA)

A complementary lithography technology.


DSA is a complementary lithography technology. When used in conjunction with a pre-pattern that automatically directs the orientation of block copolymers, DSA can reduce the pitch of the final printed structure. Using 193nm lithography, DSA has demonstrated the ability to pattern structures down to 12.5nm. The industry also is working on next-generation, high chi materials, which could extend the technology beyond 12.5nm.

DSA works, briefly, by exploiting the differing surface energies of the components of a block co-polymer (BCP) such as PS-b-PMMA (poly(styrene-block-methyl methacrylate)). The two components are mutually repulsive, and in the absence of a defined surface pattern will form a so-called “fingerprint” morphology, with alternating domains of polymer A and polymer B forming curved patterns over the coated surface. Pre-patterns, formed either by chemical stripes on the surface (chemoepitaxy) or physical trenches (graphoepitaxy), are used to define the polymer structure. By providing a favorable surface for either polymer A or polymer B, the pre-pattern constrains the BCP material to form lines and spaces, contact holes, or whatever features might be desired. Defects can result from defects or variations in the pre-pattern, in the BCP material, or in the segregation step. Of these, segregation defects are unique to DSA, while the others are familiar from conventional lithography processes.

As DSA processes are still fairly immature, firm conclusions about its viability for mass production are difficult. It appears, though, that the most common problems, such as particles and spot defects, are probably due to immature processes and materials and will become less frequent over time. While DSA-specific defects do exist, they are rare and are unlikely to pose serious obstacles to adoption of this technology. At least in the short term. Scalability of DSA processes to still smaller feature sizes remains an open question. If smaller features require new material systems, these questions may have to be revisited for each process node.


Using DSA With EUV