The Length-Dependence of the 1/f Noise of Graded-Channel SOI nMOSFETs

This paper describes a low-frequency (LF) noise study of Graded-Channel Fully Depleted (FD) Silicon-on-Insulator (SOI) n-channeIMOS transistors, with special emphasis on the length dependence.It is shown that the LF noise is predominantly 1/f-like with acurrent noise spectral density behaving in most cases according tothe trapping model. While a clear improvement in the lineartransfer characteristics is obtained for the GC structure, comparedwith the uniformly doped FD or the undoped intrinsic devices, theLF noise magnitude is found to be larger, which may bedetrimental for analog/RF applications. It is demonstrated here thatthe higher noise is associated with the extra current in the GCnMOSFET, giving rise to excess fluctuations which are probablyassociated with generation-recombination events at the boundarybetween the extrinsic and the intrinsic part of the device.