Development and advanced characterization of novel chemically amplified resists for next generation lithography
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The microelectronics industry has made remarkable progress with the development of integrated circuit (IC) technology which depends on the advance of micro-fabrication and integration techniques. On one hand, next-generation lithography (NGL) technologies which utilize extreme ultraviolet (EUV) and the state-of-art 193 nm immmersion and double patterning lithography have emerged as the promising candidates to meet the resolution requirements of the microelectronic industry roadmap. On the other hand, the development and advanced characterization of novel resist materials with the required critical imaging properties, such as high resolution, high sensitivity, and low line edge roughness (LER), is also indispensable. In conventional multi-component chemically amplified resist (CAR) system, the inherent incompatibility between small molecule photoacid generator (PAG) and the bulky polymer resin can lead to PAG phase separation, PAG aggregation, non-uniform PAG and acid distribution, as well as uncontrolled acid migration during the post-exposure baking (PEB) processes in the resist film. These problems ultimately create the tri-lateral tradeoff between achieving the desired lithography characteristics. Novel resist materials which can relief this constraint are essential and have become one of the most challenging issues for the implementation NGL technologies. This thesis work focuses on the development and characterization of novel resist materials for NGL technologies. In the first part of the thesis work, advanced characterization techniques for studying resist fundamental properties and lithographic performance are developed and demonstrated. These techniques provide efficient and precise evaluations of PAG acid generation, acid diffusivity, and intrinsic resolution and LER of resist materials. The applicability of these techniques to the study of resist structure-function relationships are also evaluated and discussed. In the second part of the thesis work, the advanced characterization and development of a novel resist system, the polymer-bound-PAG resists, are reported. The advantages of direct incorporation of PAG functionality into the resist polymer main chain are investigated and illustrated through both experimental and modeling studies. The structure-function relationships between the fundamental properties of polymer-bound-PAG resists and their lithographic performance are also investigated. Recommendations on substantial future works for characterizing and improving resist lithographic performance are discussed at the end of this thesis work.