We report the development of an imaging layer technology for 50 kV electron-beam lithography based upon the displacement of noncovalently bound amine ligands from a siloxane host film. The patterned films were used as templates for the selective deposition of an electroless nickel film resulting in a positive tone imaging mechanism. The deposited nickel was sufficiently robust to function as an etch mask for pattern transfer by reactive ion etching. Metallized and etched patterns with linewidths to approximately 40 nm are demonstrated using an exposure dose of 500 μC/cm2.

We have used the laser Doppler technique of electrophoretic light scattering to study the electrokinetic and gross conformational manifestations of the binding of divalent cations to DNA in low-salt solutions. By electrokinetic assay, divalent ion affinities to DNA in the 5–500 μM range increase in the order Mn+2<Co+2<Mg+2<Cu+2. The ELS spectra show that Cu+2 denatures double-stranded DNA in the 50–200 μM concentration range, thereby augmenting the reduction in electrophoretic mobility. Counterion condensation theory correctly predicts the form of the electrophoretic mobility reduction for territorially bound ions such as Mg+2, but the absolute magnitudes of electrophoretic mobility predicted by an equation deduced from condensation theory overestimate our experimental values.

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Articles you may be interested inTransport studies of isolated molecular wires in self-assembled monolayer devices J. Appl. Phys. 98, 034314 (2005); 10.1063/1.2005372 Photochemical reaction of organosilane self-assembled monolayer as studied by scanning probe microscopy A scanning tunneling microscope (STM) has been used to investigate organosilane self-assembled monolayer films (SAMs) as imaging layers for low voltage e-beam lithography. We have studied three different SAMs [(aminoethylaminomethyl)phenethyltrimethoxysilane (PEDA), 4-chloromethylphenyltrichlorosilane (CMPTS), and n-octadecyltrichlorosilane (OTS)J deposited on the native oxide of Si. We have found OTS to act as a positive resist in wet etch processing upon exposure to 50 keV electrons, in agreement with Lercel p. Vac. Sci. Technol. B 11, 2823(19931-Identically processed samples patterned with low voltage (-10 to --25 V tip-sample bias) electrons in the STM exhibit a negative tone. STM biases below -10 V were insufficient to expose the film. An improved etch for STM-generated patterns, leading to smoother surfaces, was developed. STM exposure of PEDA and CMPTS SAMs leads to a destruction of ligand functionality. An exposure threshold of--4 V bias for CMPTS and -8 V for PEDA has been established. As an example of post-exposure processing, these latent images were metallized with an aqueous Pd(II) catalyst solution followed by an electroless Ni plating bath. The patterned, thin (25 nm) Ni layers grown in this way are shown to be excellent masks for reactive ion etching (RIB) with SF 6 , exhibiting at least a 1:200 etch selectivity on Si. Linewidths after metallization of 20 nm and etched (CBrF/O z RIE) trench widths of 25 nm are shown.