IN-DEPTH EXPLORATION OF SI-SIO2 INTERFACE TRAPS IN MOS-TRANSISTORS USING THE CHARGE-PUMPING TECHNIQUE

It is shown that the charge pumping (CP) technique can be used for ext raction of the depth concentration profile of traps situated in the ox ide of metal-oxide-semiconductor, (MOS) transistors, near and at the S i-SiO2 interface. The trap density is obtained from the variation of t he charge pumping current as a function of frequency, the other measur ement parameters being kept constant. The concentration profiles are m easured on n and p-channel transistors from several technologies, and on virgin and stressed devices, The results show that the trap concent ration decreases rapidly from the Si-SiO2 interface in the direction o f the oxide depth and suggest that it becomes constant at a fraction o f nanometer from the silicon interface. The method easily demonstrates the trap creation due to Fowler-Nordheim stress, The profiles compare favorably with those measured using a new drain-current transient tec hnique, In all cases, the integration of the depth concentration profi les leads to the interface trap densities measured using the conventio nal charge pumping method.