Physics of fluctuation processes in downscaled silicon MOSFETs |
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Authors: | N B Lukyanchikova E Simoen and C Claeys |
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Institution: | 1.V. E. Lashkarev Institute for Physics of Semiconductors of the National Academy of Sciences of Ukraine,Kiev,Ukraine;2.Interuniversity Microelectronics Center,Leuven,Belgium;3.Catholic University of Leuven,Leuven,Belgium |
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Abstract: | Physical mechanics of fluctuation processes in advanced submicron and decananometer MOSFETs (metal-oxide-semiconductor field-effect
transistors) including the ultra-thin film SOI (siliconon-insulator) devices using strained silicon films are reviewed. The
review is substantially based on the results obtained by the authors. It is shown that the following drastic changes occur
in the nature and parameters of noise in such devices as a result of their downscaling when the gate oxide thickness and the
channel length and width are decreased, the SOI substrates are used, the silicon film thickness is reduced, the film doping
level is varied, the strained silicon films are employed, etc. Firstly, the Lorentzian components can appear in the current
noise spectra. Those components are due to (i) electron tunneling from the valence band through the gate oxide in the SOI
MOSFETs of a sufficiently thin gate oxide (LKE-Lorentzians); (ii) Nyquist fluctuations generated in the source and drain regions
near the back Si/SiO2 interface in the SOI MOSFETs (BGI Lorentzians); (iii) electron exchange between the channel and some single trap in the gate
oxide of the transistors with sufficiently small length and width of the channel (RTS Lorentzians). Secondly, the 1/f-noise level can increase due to (i) the appearance of recombination processes near the Si/SiO2 interface activated by the currents of electron tunneling from the valence band; (ii) an increase in the trap density in
the gate oxide of the devices fabricated on the biaxially tensile-strained silicon films; (iii) the contribution of the 1/f fluctuations of the current flowing through the gate oxide as a result of electron tunneling from the conduction band. At
the same time, the 1/f-noise level may decrease due to a decrease in the trap density in the gate oxide of the transistors fabricated on the uniaxially
tensile-strained silicon films. Moreover, a 1/f
1.7 component may appear in the noise spectra for the transistors of a sufficiently thin gate oxide, whose component is due to
charge fluctuations on the defects located near the interface between the gate polysilicon and the gate oxide. |
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