Dry heterometallic resist processing based on thermal sublimation deposition and development

A negative tone heterometallic ring resist (HRR) based on a supramolecular assembly [NH2(allyl)2][Cr7NiF8(piv)16] with previously demonstrated resolution down to sub-10nm lines is evaluated in terms of its flexibility to be processed either ‘wet’ (spin-cast, solvent-developed) or ‘dry’ (deposition and development by vacuum sublimation). The implemented sublimation hardware fits easily in the wafer load-lock chamber of EUV and electron beam exposure systems dedicated to R&D activities and allows for HRR films to be uniformly deposited or developed in the same vacuum environment. The HRR shows a sublimation rate dependence on temperature that obeys a Clausius-Clapeyron relation, with thermal stability up to 275°C. Flood exposures of the HRR show identical sensitivity between wet and dry deposited films, while contrast degradation is observed when dry development is initiated by increasing the temperature prior to system pump down. A modified sublimation setup allows for the dry development of exposed HRR samples inside the electron beam tool without breaking vacuum. In this case, nominally patterned 25nm L/S are identically resolved at 30 keV for wet- or dry-developed HRR.