EFFECTS STEMMING FROM RELAXATION OF THE SPACE-CHARGE REGION IN THE SEMICONDUCTOR DURING THERMALLY STIMULATED DEPOLARIZATION OF A METAL-INSULATOR-SEMICONDUCTOR STRUCTURE

A study has been made of how the interaction of the subsystem of relax ation oscillators of an insulator with the electronic subsystem of the semiconductor affects the thermally stimulated depolarization (TSD) o f metal-insulator-semiconductor (MIS) structures. A theory is derived for the TSD. The change in the voltage drop across the insulator due t o relaxation of the space-charge region of the semiconductor is taken into account. The relaxation of the spare-charge region radically modi fies the shape and quantitative characteristics of the peaks in the TS D current. These peaks split or broaden, and the area under them decre ases significantly. The standard procedure for analyzing such peaks le ads to incorrect values of the TSD characteristics. A new approach to the study of the TSD of MIS structures is developed. This approach use s synchronized measurements of the temperature dependence of the depol arization current, J(T), and of the high-frequency capacitance, C(HF)( T). This new method has been used for experiments on metal-oxide-semic onductor structures with a thermal oxide 2 . 10(-5) cm thick with an a rea of 10(-2) cm2. The structures were fabricated from P-doped Si with a resistivity on the order of 4.5 OMEGA . cm and a (100) orientation. A displacement of mobile positive ions in the SiO2 toward its interfa ce with the Si was induced by a thermal-field stress at 473 K and by a voltage V(g) = 10 V. After the structure was cooled to 200 K, and the sign of V(g) was reversed, the ordinary algorithm for measuring the T SD was implemented. Curves of J(T) and C(HF)(T) were recorded simultan eously. The experimental data are described well by a theory derived f or the very simple case of a purely thermal-emission transport of ions in the SiO2 under conditions such that the change in the Si surface p otential induced by the displacement of the ions does not disrupt the thermodynamic equilibrium in the space-charge layer of the semiconduct or.