A study of quantum interference fluctuations in deep sub-μm MOSFET´s under cryogenic conditions

We investigated the phase coherence length, l_φ, in large Si-MOSFET´s fabricated using current process technology, with a particular emphasis on highly doped silicon substrates, and then studied the effects of quantum conductance fluctuations in deep sub-μm MOSFET´s, with channel length comparable to l_φ. We identified, in a 0.2 μm MOSFET, universal conductance fluctuations in the strong inversion regime and conductance fluctuations due to variable range hopping in the weak inversion regime. The drain bias dependence of these fluctuations indicates clearly that they become a serious concern only at drain voltages lower than 10 mV. Therefore, even if the wave nature of electrons results in quantum conductance fluctuations, it will not lead to a limitation on device miniaturization in future Si-ULSI´s