Comparative Study of Surface Activation Steps for Thermally Grown Oxide Interface and Optimal Silanization

Abstract

Silanization is one of the widely explored surface modification strategies for biofunctionalization of oxide interfaces. For biosensor applications, silanes with active terminal groups such as amine, thiol, carboxylic, and aldehyde groups are utilized in routine. In near‐field sensing schemes like biologically sensitive field‐effect transistors, it is crucial to generate a homogeneous layer of silane to confine the biointeractions in close vicinity of the sensor interface. The homogeneity of such biofunctional layer is determined by the surface activation and silanization protocol being applied. Herein, the impact of the surface activation process and silanization on electrical characteristics of field‐effect devices is studied comprehensively using an electrolyte‐oxide‐semiconductor (EOS) capacitor with a high‐quality gate oxide. The thermally grown silicon oxide (SiO2) interface is activated using acidic mixtures and plasma treatment, while the subsequent silanization steps are investigated comparatively using two different silanes (3‐aminopropyl triethoxysilane (APTES) and 3‐glycidyloxypropyl trimethoxysilane (GPTMS) in wet‐chemical and vapor‐phase processes. Furthermore, the optimized silanization process is utilized to immobilize an oligo strand at the EOS capacitor surface, followed by the hybridization of complementary oligo strands. The optimized protocol holds the potential for large‐scale production of functional oxide interfaces for various applications.