P型與N型金氧半電容元件於超薄氧化層之電特性比較及應用
Comparison of the Electrical Characteristics of MOS Capacitors with Ultra-thin Oxides Grown on P- and N-type Si Substrates
Date Issued
2006
Date
2006
Author(s)
Chang, Shu-Jau
DOI
zh-TW
Abstract
For deeper understanding of p- and n-type MOS capacitor devices, we grew oxide on p- and n-type silicon substrates simultaneously with different recipes. When measuring current-voltage (J-V) characteristics, it was found that the oxide thickness dependencies of the current magnitudes of these two devices were different. Furthermore, with thin oxide films, the response of inversion saturation current to temperature in n-type MOS capacitors was much lower than that in p-type devices. The origin of these differences was mainly that the inversion saturation current in n-type devices was controlled by the recombination mechanism in interface traps located in sub-oxide, while the inversion saturation current in p-type devices was controlled by the generation mechanism. Based on the different current response to temperature of n-substrate MOS devices, we designed an interesting temperature sensor by connecting two devices in series, where n-type device was regarded as a constant current source.
When measuring capacitance-voltage (C-V) characteristics, it was found that the quality of the thin oxide film of n-type device was much better than that of p-type device. In other words, the interface trap density of n-type device is less than that of p-type device while both oxide films are very thin, which is strongly related to the sub-oxide. We improved the sub-oxide quality by increasing the growth time of oxidation, and then observed that the discrepancy between them became unapparent. Moreover, when the oxide film of n-type device was thinner, we found that negative capacitance occurred near the region when bias was changed from depletion to inversion. This is because when biasing in the neighborhood, lots of electron-hole pairs will start to recombine, which results in the stored charges near the interfacial layers decrease as the applied terminal voltage is increased. Again, when we increase the oxidation time, that is, thickening the oxide films, the negative-capacitance effect become unobvious. It is concluded that the sub-oxide plays an important role in the comparison of the characteristics of p- and n-type devices.
Subjects
金氧半電容
P型
N型
溫度感測器
負電容
MOS capacitor
p-type
n-type
temperature sensor
negative capacitance
Type
thesis