Saturation of Transient Current Read at Millisecond-Scale in MOS Capacitor with Ultra-Thin Oxide when Switching

MOS capacitor is widely used in modern semiconductor industry, especially for memory usage. In this work, transient currents read at millisecond-scale of MOS with ultra-thin oxide in voltage-switching programs were studied by experiment and simulation. Read current was observed to be saturated for a large enough write voltage, and was found to be maximal at appropriate oxide thickness. Even when too many inversion electrons were stored initially for write voltage greater than saturation voltage, electron density would decay rapidly and a number of holes would drift in for recombination within the first 1 ms due to the too small band bending. As a result, there would be a saturated value of inversion charges stored at millisecond time scale. The transient behavior studied in this work is fundamental and should be considered in the design of dynamic memory device.