Study of Si(100)-SiO₂ Interface Trap Time Constant Distributions in Large Area Conventional MOSFETs-Comparison with Submicron Devices

Abstract

A charge pumping (CP) technique has been proposed more than two decades ago to extract the Si(100)-SiO 2 interface trap time constant distribution (ITTCD) that exists at this interface. To that aim, several Elliot curves (1) needed to be recorded at a frequency, f 0 , of the order of f 0 =10 4 Hz and for a set of selected gate voltage swing, Vsw, values. The charge recombining during one period of the gate signal, Qcp 0 =Icp 0 /f 0 was extracted from the maximum CP current measured, Icp 0 , at f 0 , supposed to result from recombination due to identical electron and hole free carrier concentrations at the interface. From Qcp 0 , the recombined charge was finally measured as function of frequency, f, yielding a set of Qcp 0 (f) curves, one for each Vsw value. Assuming, as done primarily, that carrier capture resulted from tunneling from the interface to the traps in the near oxide, the set of Qcp 0 (f) curves provided a single trap "depth" concentration profile. The same kind of profile was recorded from n-and p-channel MOSFETs of different technologies (2, 3). As Pb0 centers are known to be the amphoteric defects that characterize the Si(100)-SiO 2 interface, even after forming annealing in conventional MOSFETs with thermally grown oxides, and as these centers are located at the interface, the trap time constant distribution was re-interpreted. Then, in order to evidence the way the Pb0 centers occupy the interface, the experimental conditions primarily used to extract the profiles are modified. These results are discussed with regard to previous work in that field (4, 5) and to recent results obtained by T. Tsuchiya and co-workers on submicron devices (6, 7).