Role of oxide charges on the voltage and current coupling effects between adjacent devices examined by concentric metal-insulator-semiconductor (MIS) tunnel diodes with ultra-thin oxide

The impacts of positive oxide charges within the silicon oxide (SiO2) layer on the coupling mechanism in metal-insulator-semiconductor (MIS)-coupled devices were studied. By employing the post-metallization annealing (PMA) process, the condition of coupled devices with fewer oxide charges was established. In terms of coupled voltage, the presence of oxide charges facilitated the transmission of gate voltage-induced quasi-Fermi level splitting to neighboring devices, resulting in the induction of coupled voltage. Conversely, with few oxide charges, no coupled voltage was observed at the neighboring device. Additionally, positive oxide charges induced an inversion channel at the silicon surface, fostering the sharing of minority carriers in the conducting channel between adjacent devices. The saturation currents of non-PMA devices were 104 times larger than PMA devices. Less oxide charge will induce less coupling. These mechanisms were validated through TCAD simulations. Furthermore, the impact of oxide charges on photo-sensing was discussed, revealing that oxide charges enhanced the light absorption area and increased photon-induced carriers. However, the PMA devices showed a larger light-to-dark current ratio (>300) due to a smaller dark current.