Abstract
Current and capacitance characteristics of Al/SiO2/Si(p) metal-insulator-semiconductor tunnel diode (MISTD) with oxide thickness in the range of about 2-4 nm were fabricated and studied in detail in this work. We found that the saturation reverse bias current will increase with oxide thickness in this range of oxide thickness. This non-intuitive phenomenon is caused by different levels of Schottky barrier height modulation (SBHM), which leads to the injection of the majority from metal. The majority current of Al/SiO2/Si(p) MISTD is usually neglected because of the blocking of the oxide layer and the Schottky barrier. The mechanism and numerical analysis of SBHM are discussed in this work. SBHM is significant when the oxide is thin enough for the majority to tunnel from metal to semiconductor and thick enough to hold a part of the minority inversion layer. In this specific oxide thickness range, increasing oxide thickness will increase the ability to hold the inversion layer, thus leading to higher oxide voltage (Vox) and stronger SBHM. As a result, we find that stronger SBHM lets more majority have enough energy to inject from metal to semiconductor and cause higher reverse saturation current in MISTD with thicker oxide. With the numerical analysis in our work, we also predict this non-intuitive phenomenon will start to turn around when oxide thickness is thicker than about 33Å. This phenomenon indicated that majority current is an un-neglectable component when the oxide is thick enough to hold the inversion layer partially. The analysis in this work is also helpful to complete the missing part of the theory describing the current behavior of MISTD.
Highlights
The dimension of MOSFET keeps scaling down to improve area consumption, power consumption, and operation speed
Some works still finely described the current behavior of metal-insulatorsemiconductor tunnel diode (MISTD)
In 2001, Lin et al further discussed the current behavior of Al/SiO2/Si(p) MISTD [5]. [5] further confirmed that the current of Al/SiO2/Si(p) MISTD is dominated by the minority and finely describe the generation mechanism of MISTD
Summary
The dimension of MOSFET keeps scaling down to improve area consumption, power consumption, and operation speed. Metal-insulator-semiconductor tunnel (MIS) structure with ultrathin insulator layer is not considered when serving as a part of traditional transistors because of its high leakage current [1] and the problem of nonuniformity [2] At this time, high-k material appears and gets huge success [1] because high-k can keep high gate control with a thick dielectric layer. Studies focus on deep depletion [6], fringing field [7,8], oxide nonuniformity [6, 9],and carrier lifetime [10] all find increasing reverse bias current with oxide thickness This phenomenon is difficult to be interpreted by [3,4,5]. Detailed analysis on this phenomenon was performed, and a relatively complete model was derived
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