Resistance and Threshold Switching Voltage Drift Behavior in Phase-Change Memory and Their Temperature Dependence at Microsecond Time Scales Studied Using a Micro-Thermal Stage

We study the drift behavior of RESET resistance
$R_{\rm RESET}$
and threshold switching voltage
$V_{\rm th}$
in phase-change memory (PCM) and their temperature dependence. To extend the temperature-dependent measurement to microsecond time scales, we integrate an innovative micro-thermal stage (MTS) on the PCM cell. The MTS changes the temperature of the programmed region of the PCM cell within a few microseconds by placing the Pt heater in close proximity of the programmed region. First, we experimentally verify the existing phenomenological
$R_{\rm RESET}$
and
$V_{\rm th}$
drift model for constant annealing temperature at various temperatures between 25
$^{\circ}\hbox{C}$
and 185
$^{ \circ}\hbox{C}$
down to 100
$\mu\hbox{s}$
and show that the measured temperature dependence of the drift coefficient agrees well with what is expected from the existing drift models. Based on the existing drift model for a constant annealing temperature, we derive the analytical expression for the
$R_{\rm RESET}$
drift for time-varying annealing temperature and experimentally verify the analytical expression. The derived analytical expression is important to understand the impact of thermal disturbance on PCM reliability such as variations in
$R_{\rm RESET}$
and
$V_{\rm th}$
.