Effect of Lateral Diffusion Current in Inversion I-V Characteristic of MOS Devices with Ultrathin Oxide and Its Applications
Date Issued
2014
Date
2014
Author(s)
Lin, Yen-Kai
Abstract
In this thesis, we demonstrate the importance of the lateral diffusion current in the current behavior of MOS(p) capacitor with ultrathin oxide and the applications by utilizing the lateral diffusion current. In chapter 2, through comparing the current phenomenon of MOS(p) capacitors with different gate patterns, we can verify that the lateral diffusion current plays an important role in the current characteristic of MOS(p) capacitor. In other words, the perimeter-dependent current behavior is caused by the lateral diffusion current. By the supplement of the lateral diffusion current, the electron concentration is higher in the edge region than in the bulk region, leading to the increase in the edge oxide voltage and smaller Schottky barrier height of holes which allows massive Schottky diode hole current to flow through the edge of the device. Furthermore, the concept of supplement of electrons can be used to explain the difference of gate leakage currents of MOSCAP(p) and NMOSFET. In chapter 3, due to the change of the lateral diffusion current with temperature, we make use of the lateral diffusion current to detect temperature in MOS(p) tunneling temperature sensor whose inversion current is perimeter-dependent. This perimeter-dependent current phenomenon cannot be explained by the thermal generation current in the depletion region, and the temperature dependence of current does not agree with the experimental data. Instead, the edge Schottky diode hole current can be used to well explain the current behavior. In chapter 4, we demonstrate MOS(p) photodiodes by utilizing the lateral diffusion currents. Through fabricating MOS(p) photodiodes with different oxide thicknesses, we find that when the oxide is thicker, the light current is larger. This cannot be explained by the conventional explanation, i.e., the edge photo-generation current in depletion region. Moreover, by using TCAD simulation, it is proved that the edge depletion width will decrease with thicker oxide, indicating that the collection region of light is smaller and the light current also should be smaller. Just like the MOS(p) tunneling temperature sensor, the perimeter-dependent current characteristic of MOS(p) photodiode can be found in some papers and experiments in chapter 4, and this phenomenon only can be explained by the edge Schottky diode hole current. In chapter 5, we compare the current characteristics of MOS(p) and MOS(n) capacitors. In MOS(n), due to its different band structures compared to MOS(p), the lateral diffusion cannot affect the dark current behavior but can influence the light current significantly, leading to strong sensitivity enhancement in the device with thicker oxide. This phenomenon only can be explained by the oxide voltage tuning, which introduce large electron direct tunneling current, induced by the lateral hole diffusion current.
Subjects
超薄氧化層
金氧半元件
側邊擴散電流
蕭基位障調變
金氧半穿隧溫度感測器
金氧半光二極體
Type
thesis
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