Materials Design Considerations for Future Lithographic Technologies
Journal of Photopolymer Science and Technology (Fotoporima Konwakai shi)
Progress in VLSI device design and manufacture continues to demand increasingly smaller and more precise device features. While today, almost all commercial devices are made by i-and g-line (365-436 nm) photolithography, new lithographic strategies will be required within the next 5-8 years. Concomitant with the development of new lithographic techniques is the development of new resist materials. This paper presents a view of the varied chemistries that are available for the design of resist
... terials. Particular emphasis is placed on the novel chemistry and processing techniques, such as chemically amplified mechanisms and gas-phase functionalization processes, that have been developed in recent years. Parallel to the design of resist chemistries and associated processes is the development of highly sophisticated equipment used to print the circuit patterns. The predominant technology today is "conventional photolithography" (i and g-line photolithography employing 350-450. nm light). Incremental improvements in tool design and performance have allowed the continued use of 350-450 nm light to produce ever smaller features (6). Additionally, the same basic positive photoresist consisting of a diazonaphthoquinone photoactive compound and a novolac resin has continued to be the resist of choice (7,8). The alternative lithographic technologies, will, however, require new resist chemistries. The leading technological alternatives to conventional photolithography are short wavelength (190-250 nm) photolithography, direct-write or projection electron-beam, proximity x-ray or scanning ion-beam lithography (1,5,9). RESIST DESIGN REQUIREMENTS The focus of this paper concerns the design of polymer/organic materials and chemistries that may prove useful in radiation sensitive resist films. Such resists must be carefully designed to meet the specific requirements of each lithographic technology. Although these requirements vary according to the radiation source and device processing sequence, the following resist properties are common to all lithographic technologies: sensitivity, contrast, resolution, optical density, etching resistance, and The unabated progress in design and integration of VLSI devices continues to demand increasingly smaller and more precise device features. At the present time, almost all commercial devices are made by photolithography utilizing UV radiation in the wavelength range of 365-436 nm. However, within the next 5-8 years, new lithographic strategies will be required to meet resolution needs that will likely extend well below 0.5 µm. Technologies under development include electron-beam, ion-beam, X-ray, short-wavelength and extreme-UV lithographies. Each of these alternative technologies will require new polymeric resist materials and processes. This chapter has attempted to discuss the varied chemistries that are available for the design of resist materials. The future of microlithography is bright and contains many challenges in the areas of resist research and associated processing. There is no doubt that within the decade, many new materials will be commonplace within the manufacturing environment. .