Degradation Phenomenon of p+ to p+ Isolation Characteristics Caused by Carrier Injection in a High-Voltage Process

In this study, an investigation for the degradation of p+ to p+ isolation characteristics in a high voltage process with shallow trench isolation was carried out. It could be explained that the degradation phenomenon was caused by carrier injection. In order to improve this, the results of p+ to p+ isolation degradation were determined under different ion implantation conditions and depths and widths of isolation. From these results, it was found that carrier injection mainly occurred at the sidewall of a trench, and the interface trap between Si3N4 and SiO2 was considered to be a dominant factor based on the result of degradation reduction with increasing thickness of sidewall oxide. Consequently, the improvement of the p+ to p+ isolation degradation caused by carrier injection could be achieved by optimizing the dose of a masked lightly doped drain and a field implantation energy.