By using very short-wavelength electrons for the exposure of the resists, an excellent resolution of up to 2 nm can be achieved (spot beam). Exposure is carried out by conventional e-beam equipment following the principle of direct writing or shaped beam procedure.
If new and clean substrates (wafers) are used, a bake at approximately 200 °C for several minutes is sufficient for drying, but the substrates have to be processed quickly afterwards.
During development, a positive tone resist film is patterned by a removal of exposed areas, while unexposed areas are removed when negative resists are used. To achieve reproducible results,
Adhesion between coating and substrates is a very sensitive feature. Smallest changes of the cleaning procedures or the process parameters can have a fatal impact on the adhesive strength.
For the removal of all e-beam resist coatings baked at lower temperatures (softbake), polar solvents may be used such as e.g. the recommended thinner AR 300-12 or AR 600-01, 600-07,
Prior to the coating procedure, resists have to be adjusted to the temperature of the (preferably air-conditioned) working area. If the resist is too cold, air moisture may precipitate on the resist.
With respect to the achievable resolution, purely academic resolution values and industrially utilisable values represent two quite different aspects. Theoretically, resolutions of 2 nm are possible (single electron spot)
Bubbles after spin deposition are in most cases air bubbles, e.g. if the resist bottle was agitated or moved around, or if the resist was diluted prior to the coating step. Coating procedures performed immediately after bottle opening,
Electron beam resists of the AR 6000 and AR 7000 production line display quite different etch resistance features in dry etch processes such as e.g. argon sputter and CF 4 . Novolak-
Just recently coated resist films still contain a substantial amount of residual solvent, depending on the respective film thickness. The subsequent bake step at 90 – 100 °C is performed in order to dry the resist films,