Effect of Etchant on SOI Wafer Surface Roughness for APTES Silanization

Abstract

Abstract In biosensor, organic molecule is used as coupling agent for silicon wafer to attach with DNA since DNA cannot be directly bonded with the silicon surface. There are several organic molecules that can self-assemble on silicon surface and modify their properties. Silane molecules such as (3-aminopropyl) triethoxysilane (APTES), (3-(aminopropyl) triethoxysilane (APTMS) and (3-mercaptopropyl) trimethoxysilane (MPTMS) have been commonly used as a primary step to covalently attach on silicon-on-insulator (SOI) wafer. Silanes were attached to the Si-O-Si bond on the surface on SOI wafer. In this research, the effect of APTES silanization on the surface roughness of SOI wafer was studied. Tetramethylammonium hydroxide (TMAH) was used to etch SOI wafer. Ranges of surface roughness of SOI wafer were obtained after adding some additives such as isopropyl alcohol (IPA) and triton X-100. Subsequently, gold nanoparticles (AuNPs) were attached on SOI wafer surface to confirm the existing of APTES. The surface roughness of SOI wafer was characterized in detail using atomic force microscope (AFM) and scanning electron microscope (SEM). The wettability of APTES solution on the etched SOI wafer surface was measured using goniometer. It was found that lower surface roughness of SOI wafer was observed after etched using ternary solutions that consisted of TMAH, Triton X-100 and IPA. It produced excellent hydrophilic effect of APTES solution then resulted in the highest weight percent of gold attached on the SOI wafer after the silanization process.