Writing Nanostructures with a Helium Beam

Abstract

It is of considerable ttduiologicid iiitrrcst how new proccsscs for nanofabrication can be sed to go Ixyond resolution limits 01 optical litliugraphy. The rcquireincnts for such new tcdinologies arc high resolution, paralld writing m d thc possibility to form aperiodic structures. 111 our apliroadi to atom lithography we USE a rcsist tediiiique to burn pattcriis into a litliograpliic sample, where we make use ai the large internal energy (20 eV) of metastable hcliuin. For this trduiiqiie a tliin (1.5 nzn) self-assembliiig nionolaycr (SAM) of dodccmcthiolate molecules is de ositcd on a gold saniplc, wliidi is then stmcturccl by Augcr-drexcitation of He*-ntoms that hit the layer! This spatially damaged layer s e r w as a rcsist for a wet-dimnical etching process (sce fig.l(a)-(d)). In a first experinleiit we were able to copy a mask into lhc gold layer (SCT figure) and adiicved an edge resolution of less than 80 nni (see fig.l(c)!(f)). The nec~ssary dose for exposure corrcspondcd to one He'-atom per SAM-inoleciile, whidi means in our setup an rxposiirc tiinc of 8 niinutcs. In the next cxpcrinicnt.al step wc r i l l realize a pinhole camera for metastable helium whidi will allow us to produce structure^ in thc order of 30-50 inn by dernagnification of "mcsoscopic" (total sire 200 pm, fcature s i x 10 p i ) objects by a factor of 50-100. The scheme of a pinhole camera hears sevcral advantagcs besides its simple setup, as there me: the absence of any chromatic aberrations and the possibility to form pictura of npcriodic objects.