Technology path-finding framework for directed-self assembly for via layers

Abstract

Directed self assembly (DSA) is a very promising patterning technology for the sub-7-nm technology nodes, especially for via/contact layers. In the graphoepitaxy type of DSA, a complementary lithography technique is used to print the guiding templates, where the block copolymer (BCP) phase-separates into regular structures. Accordingly, the design-friendliness of a DSA-based technology is affected by several factors: the complementary lithography technique, the legal guiding templates, the number of masks/exposures used to print the templates, the related design rules, the forbidden patterns (hotspots), and the characteristics of the BCP. Thus, foundries have a huge number of choices to make for a future DSA-based technology, affecting the design-friendliness, and the cost of the technology. We propose a framework for DSA technology path-finding, for via layers, to be used by the foundry as part of design and technology co-optimization. The framework optimally evaluates a DSA-based technology in which an arbitrary lithography technique is used to print the guiding templates, possibly using many masks/exposures, and provides a design-friendliness metric. In addition, if the evaluated technology is not design-friendly, the framework computes the minimum-cost technology change that makes the technology design-friendly. The framework is used to evaluate technologies like DSA+193-nm immersion (193i) lithography, DSA+extreme ultraviolet (EUV), and DSA+193i self-aligned double patterning. For example, one study showed that one mask of EUV in a DSA+EUV technology can replace three masks of 193i in a DSA+193i technology.