IMPROVEMENT OF THE SIO2/SI INTERFACE OF METAL-OXIDE-SEMICONDUCTOR DEVICES USING GATE DIELECTRICS FORMED BY NF3-AIDED OXIDATION AND N2O POSTANNEALING

With the increasing requirement for ultrathin gate dielectrics in advanced metal-oxide-semiconductor structures, a low thermal budget process to grow thin dielectric film is vital, while at the same time maintaining the good interface quality and thin film reliability. In this article, thermal nitridation of fluorinated oxide in N2O ambient was investigated. While fluorinated oxides provide a lower thin film stress and better interface than conventional oxides, an excess amount of fluorine in the starting oxide has an adverse effect on the high field stability. For N2O-nitrided oxide, high temperature and prolonged nitridation time reduce the interface state generation DELTAD(it) resulting from avalanche electron injection at the expense of increasing the flatband voltage shift DELTAV(fb). The electrical properties are strongly process dependent. The best operating window of N2O nitridation of fluorinated oxide (F-ox), grown at 900-degrees-C with a 100 ppm NF3 additive, lies between 30 and 120 min at 950-degrees-C. With careful control of fluorinated oxide growth parameters and N2O annealing, we have demonstrated an excellent way to fabricate dielectric thin films for future applications.