Reliability characterization of dielectrics in 200V trench capacitors

Conventional reliability tests of silicon nitride dielectrics in 200V trench capacitors were carried out to predict lifetime. The applicability of constant voltage/current stress and ramped voltage/current stress tests was investigated. The methods which are typically used for planar thin dielectrics did not yield feasible predictions. In particular, charge-to-breakdown value does not appear to be a suitable measurement for the determination of the dielectric failure in trench capacitors. Lifetime extrapolation using ramped voltage stress tests can be performed. However, these results strongly depend on the delay time of the test due to charge trapping effects in the silicon nitride layer.