146
Strain-Engineered MOSFETs
noise level already is a problem in RF and analogue applications, and soon
exceeds the limits for a reliable device operation also in digital applications.
Overcoming the 1/f noise in electronic circuits and devices is an extremely
important challenge for the future. Low-frequency noise measurements are
also an important tool for device diagnostics. The 1/f noise is very sensitive
to trap and defects in the device, and is strongly related to physical processes
such as trapping and release phenomena, electron scattering mechanisms,
and phonon processes. The low-frequency noise can therefore be used as the
information-carrying signal to evaluate and get insight into the physics and
properties of a particular system, and estimate the quality and reliability of
a device [7, 8].
In order to minimise the device 1/f noise, an understanding of the noise
mechanisms, the underlying physics, and the location of the sources is necessary. Still today, after several decades of debate, the exact origin of the 1/f
noise is, in many aspects, unclear [9]. In this chapter, the 1/f noise sources and
their origins have been discussed, including the physical properties of mobility fluctuation noise, one of the most debated proposed 1/f noise mechanisms.
An elaborate analysis and modelling of the 1/f noise in terms of carrier number fluctuations, mobility fluctuations, substrate voltage effects, gate voltage
dependency, stress, and correlated mobility fluctuations is presented in terms
of the device physics and the properties of current transport. For extracting
information from traps, the time domain of random telegraph signal (RTS)
noise is also explored. The low-frequency noise study in various emerging
devices presented here is intended for use in designing nanoscale devices with
new materials and architectures for optimising the 1/f noise performance.
6.1 Noise Mechanisms
Currents and voltages in an electronic circuit show random fluctuations
(thereby causing a sharp rise and fall) around their DC bias values due
to fluctuations in the physical processes that govern the electronic carrier
transport. The desired signal is difficult to detect distinctly if the background noise power is significantly high compared to the signal strength.
Noise is a fundamental problem in science and engineering since it cannot be completely eliminated. In devices with highly scaled dimensions, the
accuracy of measurements is thus limited by setting a lower limit on signal
strength that can be accurately detected and processed. The importance of
noise characterisation has been acknowledged in a variety of fields, such as
telecommunication, nanoelectronics, mesoscopic structures, and biological
systems. However, noise not only poses a problem that should be avoided
as much as possible, but it also can actually be used as a tool to evaluate
and get insight into the properties and reliability of a particular system.
Strain-Engineered MOSFETs
noise level already is a problem in RF and analogue applications, and soon
exceeds the limits for a reliable device operation also in digital applications.
Overcoming the 1/f noise in electronic circuits and devices is an extremely
important challenge for the future. Low-frequency noise measurements are
also an important tool for device diagnostics. The 1/f noise is very sensitive
to trap and defects in the device, and is strongly related to physical processes
such as trapping and release phenomena, electron scattering mechanisms,
and phonon processes. The low-frequency noise can therefore be used as the
information-carrying signal to evaluate and get insight into the physics and
properties of a particular system, and estimate the quality and reliability of
a device [7, 8].
In order to minimise the device 1/f noise, an understanding of the noise
mechanisms, the underlying physics, and the location of the sources is necessary. Still today, after several decades of debate, the exact origin of the 1/f
noise is, in many aspects, unclear [9]. In this chapter, the 1/f noise sources and
their origins have been discussed, including the physical properties of mobility fluctuation noise, one of the most debated proposed 1/f noise mechanisms.
An elaborate analysis and modelling of the 1/f noise in terms of carrier number fluctuations, mobility fluctuations, substrate voltage effects, gate voltage
dependency, stress, and correlated mobility fluctuations is presented in terms
of the device physics and the properties of current transport. For extracting
information from traps, the time domain of random telegraph signal (RTS)
noise is also explored. The low-frequency noise study in various emerging
devices presented here is intended for use in designing nanoscale devices with
new materials and architectures for optimising the 1/f noise performance.
6.1 Noise Mechanisms
Currents and voltages in an electronic circuit show random fluctuations
(thereby causing a sharp rise and fall) around their DC bias values due
to fluctuations in the physical processes that govern the electronic carrier
transport. The desired signal is difficult to detect distinctly if the background noise power is significantly high compared to the signal strength.
Noise is a fundamental problem in science and engineering since it cannot be completely eliminated. In devices with highly scaled dimensions, the
accuracy of measurements is thus limited by setting a lower limit on signal
strength that can be accurately detected and processed. The importance of
noise characterisation has been acknowledged in a variety of fields, such as
telecommunication, nanoelectronics, mesoscopic structures, and biological
systems. However, noise not only poses a problem that should be avoided
as much as possible, but it also can actually be used as a tool to evaluate
and get insight into the properties and reliability of a particular system.