We tried to find an alternative dielectric film to own the high quality sensitive properties, so that, magnesium oxide (MgO) has been selected as a pH sensitive dielectric for the EIS operation, and is known as an alternative gate dielectric as CMOS technology has aggressively scaled down.The high-k MgO as sensing membrane on EIS structure and to investigated the characteristics of the different rapid thermal annealing(RTA) temperature in oxygen ambient. Furthermore, we studied the sensing performance of the MgO EIS structure tested in different ion (H⁺,Na⁺, K⁺, Urea, Glucose) solution.

The electrolyte-insulator-semiconductor (EIS) structures with MgO sensing membranes were fabricated on 4-inch n-type (100) Si wafer, which have a resistivity of 5–10 Ω-cm. Before deposition of the MgO film, the wafers were cleaned by using HF-dip (HF: H₂O = 1:100) to remove the native oxide. Then, a 50-nm MgO was deposited by radio frequency (RF) reactive sputtering on n-type silicon wafer. During RF sputtering, Mg oxide-target was used with 25 sccm argon flow rate (Ar: O₂=25:0). The (RF) power and pressure are 150Watt and 20mTorr, respectively. Next, Samples was annealed at different temperatures (600^oC, 700^oC, 800^oC) by rapid thermal annealing (RTA) in O₂ ambient for 30 sec. The back-side contact of the Si wafer was deposited by Al film with 300nm-thick. Then, sensing area was defined by standard photolithography process using a photosensitive epoxy, SU8-2005 of MicroChem Inc. Finally, the samples were fabricated on the copper lines of printed circuit board (PCB) by silver gel. Epoxy package was used to separate the EIS structure and the copper line.

In this study, we report an electrolyte–insulator–semiconductor (EIS) sensor with a high-k magnesium oxide (MgO) as sensing material. The effect of rapid thermal annealing (RTA) on the deposited sensing membrane has been studied in terms of structural and sensing characteristics. We used X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) to investigate the structural and morphological characteristics of deposited films. Furthermore, we studied the sensing performance of the MgO EIS structure in different ion solutions such as Urea and Glucose solutions. EIS device with MgO as sensing membrane that has been subjected to 800 ºC RTA treatment exhibits better sensing characteristics such as sensitivity of 61.64 mV/pH, hysteresis voltage of 5.03mV and 1.55mV/hr drift rate.