Mechanism of Difficulty to Study the Physics of Leakage Current Reduction by Nitridation of Silicon before High-k Dielectric Deposition Due to Change in Nucleation Characteristics and Some Other Factors

Abstract

It is expected that the leakage current can be reduced by nitridation of silicon before high-k dielectric deposition. In reality, it is not so simple because the nucleation of high-k dielectric on nitrided silicon may be different from the nucleation on silicon. In addition, the interfacial layer between the high-k dielectric becomes thinner because of the nitridation. Furthermore, the bandgap of the interfacial layer becomes smaller due to the nitridation. However, there may be less defect states in the high-k dielectric because of the nitridation. More in-depth study is needed to clarify whether leakage current is really reduced by nitridation. Experimental observation indicates the leakage current can be increased or decreased by nitridation depending on the details of the processing conditions. However, the capacitance is usually increased by nitridation; reduction of capacitance due to RTN is an unusual observation but it is possible.

Peculiarities of the Interface between High-Permittivity Dielectrics and Semiconductors

“…A kind of natural thickness saturation is perceptible in some cases. For example, in the case of Ta 2 O 5 on Si, after oxygen anneals values of about 3 nm are obtained (Lau, 2012). These values are close to the values for the case of Ta 2 O 5 films grown by thermal oxidation of Ta (Karmakov et al, 2012).…”

An Extended Unified Schottky-Poole-Frenkel Theory to Explain the Current-Voltage Characteristics of Thin Film Metal-Insulator-Metal Capacitors with Examples for Various High-k Dielectric Materials

“…For a capacitor structure involving a Schottky junction with a small effective Schottky energy barrier, there may be a lot of electrons injected into the insulating film resulting in large leakage current; a large quantity of electron traps near the Schottky junction serve as "electron injection N148 ECS Journal of Solid State Science and Technology, 1 (6) N139-N148 (2012) delay elements". 48 Up to now, deep donors and electron traps are not well characterized and understood in high-k dielectric materials. Thus more theoretical and experimental effort should be directed to understand the defect states involved.…”