With Phase-change memory (PCM), information can be stored as different resistance states even when not powered. In order to accurately characterize the reliability of PCM devices, data retention has to be tested carefully. In this paper, a new test method is applied to measure the data retention of T-shaped PCM devices. This method makes it possible to accelerate crystallization in the amorphous area by using current bias. The new method works based on the field-induced crystallization theory, and could be able to gather fast and detailed information about high-resistance state’s failure process, and at the same time, it could avoid issues related to high temperature. Experimental data for T-shaped PCM devices based on Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> are presented and analyzed. An exponential trend-line of failure time t versus reciprocal bias current 1/I shows only negligible deviation of the measured data points, enabling the extrapolation of the retention behavior for ten-year lifetime. A maximum disturb current value of 5.08 μA is extracted to guarantee the ten years data retention requirement for PCM applications.
The interface which should correspond to Ohmic contact between the TiN bottom electrode and the TiN adhesive layer is investigated. However, from the measured V-I curve, a non-linear relationship is observed. The previous research and the replotted V-I curve using double-logarithmic scale demonstrate that an oxide layer at the interface is the major reason for the non-linear relationship and that the conduction mechanism here follows the Space-Charge-Limited- Current mechanism. To eliminate the interface effect, a pulse current with a compliance is introduced. A phenomenon is observed that negative resistance occurs because of the capture of filament in the oxide layer. As the width of pulse current increases, the interface effect is eliminated due to the formation of a permanent conducting filament. And , the VI curve shows a linear relationship, representing that the interface corresponds to Ohmic contact and the interface effect has been eliminated efficiently.