Surface Potential Contrasts between Silicon Surfaces Covered and Uncovered with an Organosilane Self-Assembled Monolayer

K. Hayashi¹, N. Saito¹, H. Sugimura¹, O. Takai¹ and N. Nakagiri²

1) Department of Materials Processing Engineering, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan
2) Core Technology Center, Nikon Co., Shinagawa, Tokyo 140-8601, Japan

Organosilane self-assembled monolayers (SAMs) terminated with various functional groups formed on Si substrate has been investigated by Kelvin-probe force microscopy (KFM). SAMs were prepared from n-octadecyltrimethoxysilane (ODS:CH3(CH2)17Si(OCH3)3), heptadecafluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane (FAS:CF3(CF2)7(CH2)2Si(OCH3)3), and n-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS:H2N(CH2) 6NH(CH2)3Si(OCH3)3) by chemical vapor deposition (CVD) [1]. These SAMs were micropatterned by photolithography using a vacuum ultraviolet light at 172 nm [2], and then imaged by KFM. Surface potentials of the ODS- and FAS-SAMs were lower than that of the Si substrate where covered with native oxide, while the potential of the AHAPS-SAM was higher than that of the SiO2/Si surface. The origin of such surface potential contrasts are ascribable to dipole moments of the SAMs governed by their chemical structures, molecular orientations and arrangements.

[1] A. Hozumi, K. Ushiyama, H. Sugimura and O. Takai, Langmuir 15, 7600 (1999)
[2] H. Sugimura, K. Ushiyama, A. Hozumi and O. Takai, Langmuir 16, 885 (2000)