Lithography: Transition to Materials Synthesis

Transition to Materials Synthesis (1993–2008): Materials Capability Established to Support Expanding Mission Breadth

It is clear that the semiconductor industry needs improvements in both exposure tool optics and photoresist performance in order to keep shrinking feature sizes. There can be no doubt that improvements in stepper optics have made major contributions to increased resolution. However, the impact of the other components of the lithographic process cannot be overlooked. The drive to explore every avenue to increase lithography resolution prompted Lincoln Laboratory to investigate new materials for photoresists tailored to be transparent at ever-shorter wavelengths, to explore chemical amplification as a new imaging scheme, and to develop nonaromatic systems with improved dry etch resistance for 193-nm lithography. Together, such process improvements have been as important as better optics and shorter wavelengths at sustaining Moore's Law.

Diblock copolymers self assembly (left) and directed assembly (right) with 45 nm lamella Diblock copolymers self-assembly (top) and directed assembly (bottom) with 45 nm lamella.

Because many materials of interest could not be readily acquired, Lincoln Laboratory initiated in 1997 a synthetic chemical research effort that included the building and equipping of a new chemical synthesis and analytical chemical laboratory. Out of this effort came a variety of new material concepts for improved lithography performance, including new photoresist polymers, contrast enhancing layers, high-index immersion fluids, and photosensitizers. The ability to formulate novel photoresists allowed for insights into fundamental resist properties, including material causes of line-edge roughness and polymer-based sensitization of photoresists.

An outgrowth of this synthesis capability was the ability to develop spatially and chemically modified surfaces that exhibit superhydrophobicity and switchable adhesion with applications in microfluidics and multifunctional materials. Building on Lincoln Laboratory’s expertise in explosives phenomenology, the chemical synthesis capability was directed to performing laboratory synthesis of simulants to determine the phenomenology of laboratory-synthesized surrogate chemical agents and to quantify current detector capability toward those surrogate agents, resulting in improved sampling strategies for site assessment missions.

 

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