8. Which resolutions do e-beam resists achieve?
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). Accomplished were however, after a long optimisation processes, structures of < 10 nm so far. In our AR NEWS (14. edition), a 6-nm line of AR-N 7520 at a film thickness of 60 nm is presented. With PMMA- and calixarene resists, similarly high resolutions are obtained at film thicknesses of max. 50 nm, but these structures are still far from a commercial application due to the process parameters (most of all the high exposure doses required).
With PMMA e-beam resists, resolutions of up to 150 nm can be achieved at a film thickness of 400 nm, which are the typical parameters used in mask production. Resolutions of 50 nm are industrially realisable for 100-nm films. With negative tone electron beam resists, meanwhile already approximately 100-nm structures are reliably generated in production processes.