Thermally stimulated current method

Basic principle

The measurement method of thermally stimulated current (TSC) has a long history in the investigation of interface states and oxide traps (Simmons and Taylor, 1972; Mar and Simmons, 1975) even if it has not reached the same level of attention as the C–V and conductance techniques. It is especially suited for traps positioned close to the oxide/semiconductor interface, often called border traps (Fleetwood et al., 1998). The principle is based on releasing charge carriers from the trap potentials by first cooling the sample to a temperature low enough to make the thermal emission rate of the captured carrier in the region of hours, or long enough to be considered “frozen in.” This is followed by a linear temperature increase, releasing charge carriers, which gives rise to a current from which activation energies and capture cross sections can be obtained.

We will discuss TSC based on an example shown in Fig. 7.1 for a MOS structure with high-k oxide, including interface states and border traps. In our example, the latter are assumed to exist in the transition region, often occurring at the interface between the high-k oxide and an interlayer with properties as discussed in Section 4.5 (Lukovsky and Phillips, 2005).