Self-Assembled Monolayer Films for Nanofabrication

ABSTRACTCentral to nanofabrication is the ability to transfer a pattern from an imaging layer to a device or structure. At the smallest dimensions (<20 nm), thin resists or imaging layers have been used exclusively. The transfer of a pattern that is formed in a thin layer resist presents severe technological challenges to resist materials development. A novel approach based on self-assembling monomolecular layer resists is demonstrated with two organosilane films, formed from (aminoethylaminomethyl)phenethyltrimethoxysilane (PEDA) and 4-chloromethylphenyltrichlorosilane (CMPTS). The molecules have separate chemical functionalities for binding to a Si substrate and for promoting chemistry leading to catalysis and the growth of an electroless plated metal film. STM lithographic exposure destroys the ability of the molecule to bind to a catalyst, which initiates an electroless metallization. This forms the basis for a selective imaging and the pattern transfer process. A 25 nm thick Ni layer acts as a very robust etch mask, even as the unmasked regions of Si are etched as deep as 5 μm by reactive ion etching with SF6. With our process 15 nm lines with 3.3 nm edge roughness have been fabricated in the plated Ni and etched into the underlying Si. The development of the resist process and the STM lithography will be described and the resolution of the approach will be discussed.