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-channel MOS transistors, with special emphasis on the length dependence. It is shown that the LF noise is predominantly 1/f-like with a current noise spectral density behaving in most cases according to the trapping model. While a clear improvement in the linear transfer characteristics is obtained for the GC structure, compared with the uniformly doped FD or the undoped intrinsic devices, the LF noise magnitude is found to be larger, which may be detrimental for analog/RF applications. It is demonstrated here that the higher noise is associated with the extra current in the GC nMOSFET, giving rise to excess fluctuations which are probably associated with generation-recombination events at the boundary between the extrinsic and the intrinsic part of the device.