Meaning
Physical constants describe the frequency at which electrons or holes escape from localized energy wells within a dielectric material. The thermal detrapping rate increases exponentially as the temperature of the semiconductor device rises. This escape mechanism directly impacts the data retention time of non-volatile memory cells by reducing the stored charge level.
Energy Barrier
Deep levels within the bandgap of the insulator hold charge carriers until they gain enough kinetic energy to leave. A higher energy barrier results in a lower thermal detrapping rate at room temperature. Engineers calculate this barrier to predict how long a device will hold data in the field.
Retention Loss
Charge leakage over time causes the threshold voltage of a memory cell to shift toward its erased state. Because the thermal detrapping rate governs this process, it determines the maximum storage time before data corruption occurs. High density flash chips are particularly sensitive to this charge loss because their smaller cell volumes have less margin for error.
Temperature Dependence
Heat acts as the primary catalyst for the movement of electrons out of their trapped state. The thermal detrapping rate follows a predictable curve where every ten degree increase roughly doubles the speed of charge loss. This relationship allows manufacturers to test twenty years of retention in a few weeks by placing parts in a high temperature oven.
The results of these tests confirm whether the oxide quality meets the requirements for industrial or automotive use.
