Book: Low-Frequency Noise in Advanced MOS Devices (Analog Circuits and Signal Processing)
The excess noise above the well-known thermal noise and shot noise that
shows up at low frequencies, the so-called low-frequency noise (other names
are 1/f noise or flicker noise), has raised questions for a long time and has
now become more important than ever. The low-frequency noise generated
in the electronic devices is a key problem in analog circuits and systems
since it sets a limit on how small signals that can be detected and processed
in the circuits. In the early 1990s, the metal-oxide-semiconductor fieldeffect-
transistor (MOSFET) had a channel length of around 0.5 μm and was
mainly used in digital electronics. The MOS transistor at that time had a
conventional Si channel, SiO2 gate dielectrics and few advanced features.
The tremendous improvements in CMOS performance during the last
decade, resulting from continuous advances in the CMOS technology, have
stimulated the recent explosion in information and communication
technology. Nowadays, MOS transistors are not used only in digital
applications but also in a wide range of analog circuits. The low-frequency
noise in the CMOS devices has therefore emerged as an important concern.
The rapid shrinking of the device dimensions (the smallest gate length is
around 30 nm in 2006) is not only a challenging technological problem, the
low-frequency noise also increases as the dimensions become smaller with
fewer and fewer charge carriers in the active region of the device. It has even
been predicted that low-frequency noise will be a problem in digital
applications in a few years time.