Two-point capacitance-voltage (TPCV) concept: A new method for NBTI characterization

Negative bias temperature instability (NBTI) in MOS capacitors has been investigated using a novel NBTI measurement method, named two-point capacitance-voltage (TPCV). This method is based on C-V techniques and allows one to independently separate the interface (ΔN
_it
) and oxide traps (ΔN
_ot
) induced by NBTI. For the first time, to our knowledge, such a method is proposed. The TPCV method permits a broad investigation in reliability studies by exploiting changes in capacitance. It is based on a simple theoretical concept and consists of measuring the evolution of capacitance at two points; the first at the flat-band voltage (V
_fb
) and the second at V
_fb
+ ΔV. By assuming a linear CV characteristic variation between V
_fb
and mid-gap voltage (V
_mg
), the relations of voltage shifts components (V
_fb
, V
_mg
, and V
_it
) are developed. The experimental results have shown that the proposed approach allows reducing the recovery amount compared to full CV characteristics. The trapped charge, ΔN
_ot
and ΔN
_it
present a power law stress-time-dependence. In addition, the results have shown a quasi different kinetic of interface state generation as well as oxide trapped charges, while the component ΔN
_ot
is greater than ΔN
_it
.