Differentiation of field-induced and native oxide using selective formation of self-assembled monolayer

The formation process of an alkylsiloxane self-assembled monolayer SAM.on silicon oxide produced under various conditions was investigated. The growth rate of octadecyltrichlorosilane OTS.SAM was dependent on the moisture level in the oxidation system. Area-selective oxidation of a silicon substrate with a native oxide layer was carried out under controlled humidity conditions by the field induced oxidation FIO.technique using an atomic force microscope with a conductive cantilever. The silicon substrate partly FIO oxidized under dry nitrogen was immersed into the OTS solution, and the contact angle and topographic image showed that the OTS layer was formed only on the native oxide. In contrast, when the FIO was performed under a humidity of 88%, OTS SAM was formed both on FIO and native oxides. These results indicate that SAM formation on silicon oxides can be locally suppressed by FIO in a dry environment. Using this technique, we could fabricate an OTS SAM line structure as narrow as 22 nm. q1999 Elsevier Science B.V. All rights reserved.