Study of Random Telegraph Noise in Ultra Small MOSFET and its Reliability

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Random telegraph noise originating from carrier trapping in ultra small MOSFETs have been measured by an automated measurement system composed of desktop computer, Picoーammeter and voltage sources. Vast number of on-off current characteristics has been accumulated into computer memory and then capture/emission time for carriers have been statistically analyzed. Noted that the random telegraph noise should be measured under the condition of low temperature fluctuation, typically less than one degree centigrade, because the change of measurement temperature causes order of magnitude difference in the average capture/emission times : derived barrier height is approximately several hundred meV. The activation energy of the capture/emission time is found to directly relate to barrier heignt associated with elastic strain originating from lattice restructuring.The analysis of the noise data reveals that the traps causing random telegraph noise locate 1 to 2 nm apart from the Si/Sio2 interfac … More e. The Coulomb repulsive range due to the trapped charge is a function of the inversion charge density because of the screening effect. In the strong inversion regime, the random telegraph noise was rarely observed. In the weak inversion condition, random telegraph noise is observed for the MOSFETs with channel width of below one tenth micrometer because the repulsive range is the order of several hundredth micrometer. Measurements at low temperature demonstrated enhanced random noise.The mechanism of interface trap generation has been investigated. Trap generation rate due to high energy electrons is function of the number of electrons colliding the interface and of their kinetic energy. Number of generated traps due to holes is found to be proportional to that of the injected holes into the oxide.In ultra small MOSFETs, carrier energy is no more unique function of electric field in the channel because of non-equilibrium carrier transport. Therefore, voltage scaling guideline should be modified from the conventional model. We proposed a new voltage scaling guideline for ultra small MOSFETs. Less