Improvement of field and time dependent breakdown of trench capacitor using O/N/O dielectric and rounding off technique

Abstract

Etching following re-oxidation (commonly called rounding-off oxidation) and oxide/nitride/oxide (ONO) dielectrics were used to improve the breakdown characteristics of trench capacitors fabricated by RIE processing. These improved trench capacitors were then evaluated by a field-dependent breakdown test and a time-dependent breakdown test. The results show that ONO dielectric and rounding off oxidation can raise the breakdown voltage of trench capacitors. However, from the time-dependent breakdown tests, only rounding-off oxidation can reduce the number of defects at the interface so as to improve the MTTF (mean time to failure) of trench capacitors. Nevertheless, if both ONO dielectric and rounding-off oxidation techniques are used, the improvement can be very significant.