||電気系E3棟2階 会議室C E3-216
"High performance and low noise metal-oxide-semiconductor field-effect transistors"
The low frequency noise in metal-oxide-semiconductor field-effect transistors also known as Flicker or even 1/f noise is recently gaining interest among the microelectronic manufacturers. Indeed, it is up converted in phase noise at high frequency and therefore it is becoming a strong limiting factor of performance since the devices are severely scaled down, thus the interest to reduce it to catch up with the semiconductor roadmap. Besides, the study of the low frequency noise can provide precious information regarding for example the fabrication process or the quality of a MOSFET. Consequently, in addition to provide the noise performance of a given technology, its study in the case of newly developed devices ultimately aimed at replacing the present CMOS technology is of interest not only to investigate the source of the low frequency noise but also to optimize a fabrication process or even investigate the conduction mechanism. The present seminar will fall within this scope and will be organized into 3 main sections.
The first section will analyze the reduction of the low frequency noise in MOSFETs. Indeed, the implementation of a new salicide structure for the source and drain contacts resulted in a 2 decades reduction of the low frequency noise. In addition, it has been revealed that a further reduction can be expected by using a newly developed plasma process for the fabrication of the gate oxide.
The second section will assess the performances and especially the noise one of a newly developed MOSFET working on accumulation mode rather than on the conventional inversion one. In addition to feature a higher drivability and a better reliability than the conventional MOSFETs, these new devices exhibit a lower low frequency noise level, making them a very serious replacement for the future CMOS technology.
The third section will present the 1/f noise study in MOSFETs at high drain current. As a matter of fact, within this region, parasitic noise such as the one coming from the access series resistances are covering up the 1/f noise stemming from the channel of the MOSFETs, preventing us to study it. However, on account of a newly developed process and of a new orientation of the silicon, its investigation at high drain current has been made possible. This revealed that both noise sources, the traps located at the Si/SiO2 interface and the fundamental fluctuation of the mobility are generating the 1/f noise at the same time. These results arisen new questions about the induced mobility fluctuations of the correlated number and mobility fluctuation theory.