CO2‐Based Dual‐Tone Resists for Electron Beam Lithography

The increasing global environmental and energy crisis has urgently motivated the advancement of sustainable materials. Significant effort has been focused on developing new materials to replace the fossil‐based resists in the semiconductor industry based on greener sources such as ice, dry ice, small organic molecules, and proteins. Such resist materials, however, have yet to meet the stringent requirements of high sensitivity, high resolution, reliable repeatability, and good compatibility with the current protocols. To this end, CO2‐based polycarbonates (CO2‐PCs) obtained from the copolymerization of CO2 and epoxides are demonstrated as sustainable dual‐tone (positive & negative tone) resists for electron beam lithography. By adjusting the chemical structure, developing agent, and molecular weight, the CO2‐PCs present high sensitivities to electron beam (1.3/120 µC cm−2), narrow critical dimensions (29/58 nm), and moderate line edge roughness (4.6/26.7 nm) for negative and positive resists, respectively. A deep understanding of the exposure mechanism of CO2‐PC resists is provided on the basis of the Fourier transform infrared, Raman, and electron ionization mass spectroscopy. 2D photonic crystal devices are fabricated using the negative and positive CO2‐PC resists, respectively, and both devices show distinct colors derived from their well‐defined nanostructures, indicating the great practical potential of CO2‐derived electron beam resists. CO2‐derived polycarbonates obtained via the copolymerization of CO2 with various oxiranes are utilized as dual‐tone resists for the first time with outstanding sensitivity and resolution under electron beam exposure.