New Processes and Technologies to Reduce the Low‐Frequency Noise of Digital and Analog Circuits

The chapter is intended to provide the reader with means to reduce low‐frequency noise in Metal-Oxide-Semiconductor Field-Effect-Transistor (MOSFET). It is demonstrated that low‐resistivity source and drain electrodes can greatly lower the low‐frequency noise level by suppressing their contribution to the total noise. Furthermore, new plasma processes having the advantages to work at low electron temperature can achieve a further reduction, thanks to the fabrication of a better gate oxide and to a reduction of damages generally induced by conventional plasma processes. Reducing the impact of the traps on the carrier flowing inside the channel by burying the channel can also achieve a reduction of the noise level, but unfortunately at the cost of a degradation of the electrical performances. Finally, the noise analysis of the low‐frequency noise in accumulation‐mode MOSFETs showed that these newly developed devices have a lower noise level than conventional structures, which, in addition to their superiority in term of electrical performances, establishes them as a serious platform for the next Complementary Metal-Oxide-Semiconductor Field-Effect-Transistor (CMOS) technology

Carrier Mobility in Field-Effect Transistors

Authors investigate the carrier mobility in field-effect transistors mainly when fabricated on Si(110) wafers. They showed that the methods developed to extract the conduction parameters cannot be implemented for Si(110) p-MOSFETs. Authors then developed a more accurate mobility model able to simulate not only the drivability but also the transconductance for these same devices. The study of the relation between the mobility, channel direction and wafer orientation revealed that the channel direction had a significant impact on the mobility for transistors fabricated on Si(110) wafers, the highest electron and hole mobilites being obtained for a channel along the and directions, respectively. No relations were found for Si(100) wafers. The study of the dependence of the scattering mechanism limiting the mobility in Si(110) n-MOSFETs showed that the Coulomb and surface roughness scattering mechanisms were responsible for the degradation of the mobility when compared to the one on Si(100) wafers. Finally, the measurement of the mobility in an accumulation-mode MOSFETs is not straightforward since a bulk contribution, owing to the SOI layer, is adding to channel current. A methodology has been successfully implemented that led to the experimental verification of the universal behaviour of the mobility in an accumulation layer